Modelling resonances of the standing body exposed to vertical whole-body vibration: Effects of posture

NASA Astrophysics Data System (ADS)

Subashi, G. H. M. J.; Matsumoto, Y.; Griffin, M. J.

2008-10-01

Lumped parameter mathematical models representing anatomical parts of the human body have been developed to represent body motions associated with resonances of the vertical apparent mass and the fore-and-aft cross-axis apparent mass of the human body standing in five different postures: 'upright', 'lordotic', 'anterior lean', 'knees bent', and 'knees more bent'. The inertial and geometric parameters of the models were determined from published anthropometric data. Stiffness and damping parameters were obtained by comparing model responses with experimental data obtained previously. The principal resonance of the vertical apparent mass, and the first peak in the fore-and-aft cross-axis apparent mass, of the standing body in an upright posture (at 5-6 Hz) corresponded to vertical motion of the viscera in phase with the vertical motion of the entire body due to deformation of the tissues at the soles of the feet, with pitch motion of the pelvis out of phase with pitch motion of the upper body above the pelvis. Upward motion of the body was in phase with the forward pitch motion of the pelvis. Changing the posture of the upper body had minor effects on the mode associated with the principal resonances of the apparent mass and cross-axis apparent mass, but the mode changed significantly with bending of the legs. In legs-bent postures, the principal resonance (at about 3 Hz) was attributed to bending of the legs coupled with pitch motion of the pelvis in phase with pitch motion of the upper body. In this mode, extension of the legs was in phase with the forward pitch motion of the upper body and the upward vertical motion of the viscera.

The influence of gravity on regional lung blood flow in humans: SPECT in the upright and head-down posture.

PubMed

Ax, M; Sanchez-Crespo, A; Lindahl, S G E; Mure, M; Petersson, J

2017-06-01

Previous studies in humans have shown that gravity has little influence on the distribution of lung blood flow while changing posture from supine to prone. This study aimed to evaluate the maximal influence of posture by comparison of regional lung blood flow in the upright and head-down posture in 8 healthy volunteers, using a tilt table. Regional lung blood flow was marked by intravenous injection of macroaggregates of human albumin labeled with 99m Tc or 113m In, in the upright and head-down posture, respectively, during tidal breathing. Both radiotracers remain fixed in the lung after administration. The distribution of radioactivity was mapped using quantitative single photon emission computed tomography (SPECT) corrected for attenuation and scatter. All images were obtained supine during tidal breathing. A shift from upright to the head-down posture caused a clear redistribution of blood flow from basal to apical regions. We conclude that posture plays a role for the distribution of lung blood flow in upright humans, and that the influence of posture, and thereby gravity, is much greater in the upright and head-down posture than in horizontal postures. However, the results of the study demonstrate that lung structure is the main determinant of regional blood flow and gravity is a secondary contributor to the distribution of lung blood flow in the upright and head-down positions. NEW & NOTEWORTHY Using a dual-isotope quantitative SPECT method, we demonstrated that although a shift in posture redistributes blood flow in the direction of gravity, the results are also consistent with lung structure being a greater determinant of regional blood flow than gravity. To our knowledge, this is the first study to use modern imaging methods to quantify the shift in regional lung blood flow in humans at a change between the upright and head-down postures. Copyright © 2017 the American Physiological Society.

Effects of deep breathing on internal oblique and multifidus muscle activity in three sitting postures

PubMed Central

Ko, Min-Joo; Jung, Eun-Joo; Kim, Moon-Hwan; Oh, Jae-Seop

2018-01-01

[Purpose] This study was to investigate differences in the level of activity of the external oblique (EO), internal oblique (IO), and multifidus (MF) muscles with deep breathing in three sitting postures. [Subjects and Methods] Sixteen healthy women were recruited. The muscle activity (EO, IO, MF) of all subjects was measured in three sitting postures (slumped, thoracic upright, and lumbo-pelvic upright sitting postures) using surface electromyography. The activity of the same muscles was then remeasured in the three sitting postures during deep breathing. [Results] Deep breathing significantly increased activity in the EO, IO, and MF compared with normal breathing. Comparing postures, the activity of the MF and IO muscles was highest in the lumbo-pelvic upright sitting posture. [Conclusion] An lumbo-pelvic upright sitting posture with deep breathing could increase IO and MF muscle activity, thus improving lumbo-pelvic region stability. PMID:29706695

Interactive effect of body posture on exercise-induced atrial natriuretic peptide release.

PubMed

Ray, C A; Delp, M D; Hartle, D K

1990-05-01

The purpose of this investigation was to test the hypothesis that supine exercise elicits a greater atrial natriuretic peptide (ANP) response than upright exercise because of higher atrial filling pressure attained in the supine posture. Plasma ANP concentration ([ANP]) was measured during continuous graded supine and upright exercise in eight healthy men at rest after 4 min of cycling exercise at 31, 51, and 79% of posture-specific peak oxygen uptake (VO2 peak), after 2 min of cycling at posture-specific VO2 peak, and 5 and 15 min postexercise. [ANP] was significantly increased (P less than 0.05) above rest by 64, 140, and 228% during supine cycling at 51 and 79% and VO2 peak, respectively. During upright cycling, [ANP] was significantly increased (P less than 0.05) at 79% (60%) and VO2 peak (125%). After 15 min of postexercise rest, [ANP] remained elevated (P less than 0.05) only in the supine subjects. [ANP] was 63, 79, and 75% higher (P less than 0.05) in the supine than in the upright position during cycling at 51 and 79% and VO2 peak. Systolic, diastolic, and mean blood pressures were not significantly (P greater than 0.05) different between positions in all measurement periods. Heart rates were lower (P less than 0.05) in the supine position compared with the upright position. In conclusion, these results suggest that supine exercise elicits greater ANP release independent of blood pressure and heart rate but presumably caused by greater venous return, central blood volume, and concomitant atrial filling pressure and stretch.

Leg orientation as a clinical sign for pusher syndrome

PubMed Central

Johannsen, Leif; Broetz, Doris; Karnath, Hans-Otto

2006-01-01

Background Effective control of (upright) body posture requires a proper representation of body orientation. Stroke patients with pusher syndrome were shown to suffer from severely disturbed perception of own body orientation. They experience their body as oriented 'upright' when actually tilted by nearly 20° to the ipsilesional side. Thus, it can be expected that postural control mechanisms are impaired accordingly in these patients. Our aim was to investigate pusher patients' spontaneous postural responses of the non-paretic leg and of the head during passive body tilt. Methods A sideways tilting motion was applied to the trunk of the subject in the roll plane. Stroke patients with pusher syndrome were compared to stroke patients not showing pushing behaviour, patients with acute unilateral vestibular loss, and non brain damaged subjects. Results Compared to all groups without pushing behaviour, the non-paretic leg of the pusher patients showed a constant ipsiversive tilt across the whole tilt range for an amount which was observed in the non-pusher subjects when they were tilted for about 15° into the ipsiversive direction. Conclusion The observation that patients with acute unilateral vestibular loss showed no alterations of leg posture indicates that disturbed vestibular afferences alone are not responsible for the disordered leg responses seen in pusher patients. Our results may suggest that in pusher patients a representation of body orientation is disturbed that drives both conscious perception of body orientation and spontaneous postural adjustment of the non-paretic leg in the roll plane. The investigation of the pusher patients' leg-to-trunk orientation thus could serve as an additional bedside tool to detect pusher syndrome in acute stroke patients. PMID:16928280

Relationships among spinal mobility and sagittal alignment of spine and lower extremity to quality of life and risk of falls.

PubMed

Ishikawa, Yoshinori; Miyakoshi, Naohisa; Hongo, Michio; Kasukawa, Yuji; Kudo, Daisuke; Shimada, Yoichi

2017-03-01

Spinal deformities can affect quality of life (QOL) and risk of falling, but no studies have explored the relationships of spinal mobility and sagittal alignment of spine and the lower extremities simultaneously. Purpose of this study is to clarify the relationship of those postural parameters to QOL and risk of falling. The study evaluated 110 subjects (41 men, 69 women; mean age, 73 years). Upright and flexion and extension angles for thoracic kyphosis, lumbar lordosis, and spinal inclination were evaluated with SpinalMouse ® . Total-body inclination and hip and knee flexion angles in upright position were measured from lateral photographs. Subjects were divided into Fallers (n=23, 21%) and Non-fallers (n=87, 79%) based on past history of falls. QOL was assessed using the Short Form 36 Health Survey (SF-36 ® ). Age, total-body inclination, spinal inclination upright and in extension, thoracic kyphosis in flexion, lumbar lordosis upright and in extension, and knee flexion correlated significantly with the SF-36. Multiple regression analysis revealed total-body inclination and knee flexion to have the most significant relationships with the SF-36. SF-36, total-body inclination, spinal inclination in extension, thoracic kyphosis in flexion, lumbar lordosis upright and in extension, and hip and knee flexion angles differed significantly between Fallers and Non-fallers (P<0.05 for all). Multivariate logistic regression analyses revealed lumbar lordosis in extension to be a significant predictor of falling (P=0.038). Forward-stooped posture and knee-flexion deformity could be important indicator of lower QOL. Moreover, limited extension in the lumbar spine could be a useful screening examination for fall prevention in the elderly. Copyright © 2017 Elsevier B.V. All rights reserved.

Genetics Home Reference: multiple system atrophy

MedlinePlus

... inability to hold the body upright and balanced (postural instability). The other type of multiple system atrophy , ... cells in parts of the nervous system that control movement, balance and coordination, and autonomic functioning. The ...

Spinal Stiffness in Prone and Upright Postures During 0-1.8 g Induced by Parabolic Flight.

PubMed

Swanenburg, Jaap; Meier, Michael L; Langenfeld, Anke; Schweinhardt, Petra; Humphreys, B Kim

2018-06-01

The purpose of this study was to analyze posterior-to-anterior spinal stiffness in Earth, hyper-, and microgravity conditions during both prone and upright postures. During parabolic flight, the spinal stiffness of the L3 vertebra of a healthy 37-yr-old man was measured in normal Earth gravity (1.0 g), hypergravity (1.8 g), and microgravity (0.0 g) conditions induced in the prone and upright positions. Differences in spinal stiffness were significant across all three gravity conditions in the prone and upright positions. Most effect sizes were large; however, in the upright posture, the effect size between Earth gravity and microgravity was medium. Significant differences in spinal stiffness between the prone and upright positions were found during Earth gravity and hypergravity conditions. No difference was found between the two postures during microgravity conditions. Based on repeated measurements of a single individual, our results showed detectable changes in posterior-to-anterior spinal stiffness. Spinal stiffness increased during microgravity and decreased during hypergravity conditions. In microgravity conditions, posture did not impact spinal stiffness. More data on spinal stiffness in variable gravitational conditions is needed to confirm these results.Swanenburg J, Meier ML, Langenfeld A, Schweinhardt P, Humphreys BK. Spinal stiffness in prone and upright postures during 0-1.8 g induced by parabolic flight. Aerosp Med Hum Perform. 2018; 89(6):563-567.

Comparison of anti-siphon devices-how do they affect CSF dynamics in supine and upright posture?

PubMed

Gehlen, Manuel; Eklund, Anders; Kurtcuoglu, Vartan; Malm, Jan; Schmid Daners, Marianne

2017-08-01

Three different types of anti-siphon devices (ASDs) have been developed to counteract siphoning-induced overdrainage in upright posture. However, it is not known how the different ASDs affect CSF dynamics under the complex pressure environment seen in clinic due to postural changes. We investigated which ASDs can avoid overdrainage in upright posture best without leading to CSF accumulation. Three shunts each of the types Codman Hakim with SiphonGuard (flow-regulated), Miethke miniNAV with proSA (gravitational), and Medtronic Delta (membrane controlled) were tested. The shunts were compared on a novel in vitro setup that actively emulates the physiology of a shunted patient. This testing method allows determining the CSF drainage rates, resulting CSF volume, and intracranial pressure in the supine, sitting, and standing posture. The flow-regulated ASDs avoided increased drainage by closing their primary flow path when drainage exceeded 1.39 ± 0.42 mL/min. However, with intraperitoneal pressure increased in standing posture, we observed reopening of the ASD in 3 out of 18 experiment repetitions. The adjustable gravitational ASDs allow independent opening pressures in horizontal and vertical orientation, but they did not provide constant drainage in upright posture (0.37 ± 0.03 mL/min and 0.26 ± 0.03 mL/min in sitting and standing posture, respectively). Consequently, adaptation to the individual patient is critical. The membrane-controlled ASDs stopped drainage in upright posture. This eliminates the risk of overdrainage, but leads to CSF accumulation up to the volume observed without shunting when the patient is upright. While all tested ASDs reduced overdrainage, their actual performance will depend on a patient's specific needs because of the large variation in the way the ASDs influence CSF dynamics: while the flow-regulated shunts provide continuous drainage in upright posture, the gravitational ASDs allow and require additional adaptation, and the membrane-controlled ASDs show robust siphon prevention by a total stop of drainage.

Postural Stability is Altered by Blood Shift

NASA Astrophysics Data System (ADS)

Marais, M.; Denise, P.; Guincetre, J. Y.; Normand, H.

2008-06-01

Non-vestibular influences as shift in blood volume changed perception of body posture. Then, factors affecting blood shift may alter postural control. The purpose of our study was to investigate the effects of leg venous contention on postural stability. Twelve subjects were studied on a balance plate for 5 minutes with the eyes closed, in 3 conditions: with no leg venous contention or grade 1 and 3 support stockings. Standard deviation of x and y position was calculated before and after the closure of the eyes. Strong venous contention altered postural stability, after the eyes were closed, during the first 10 s of standing. As support stockings prevent blood shift induced by upright posture, this result is in line with the hypothesis that blood shifts influence the perception of body orientation and postural control among others factors as vision, vestibular inputs... This strong venous contention could induce an increase of fall.

Influence of Electrotactile Tongue Feedback on Controlling Upright Stance during Rotational and/or Translational Sway-referencing with Galvanic Vestibular Stimulation

NASA Technical Reports Server (NTRS)

Wood, Scott J.; Tyler, Mitchell E.; Bach-y-Rita, Paul; MacDougall, Hamish G.; Moore, Steven T.; Stallings, Valerie L.; Paloski, William H.; Black, F. Owen

2007-01-01

Integration of multi-sensory inputs to detect tilts relative to gravity is critical for sensorimotor control of upright orientation. Displaying body orientation using electrotactile feedback to the tongue has been developed by Bach-y-Rita and colleagues as a sensory aid to maintain upright stance with impaired vestibular feedback. MacDougall et al. (2006) recently demonstrated that unpredictably varying Galvanic vestibular stimulation (GVS) significantly increased anterior-posterior (AP) sway during rotational sway referencing with eyes closed. The purpose of this study was to assess the influence of electrotactile feedback on postural control performance with pseudorandom binaural bipolar GVS. Postural equilibrium was measured with a computerized hydraulic platform in 10 healthy adults (6M, 4F, 24-65 y). Tactile feedback (TF) of pitch and roll body orientation was derived from a two-axis linear accelerometer mounted on a torso belt and displayed on a 144-point electrotactile array held against the anterior dorsal tongue (BrainPort, Wicab, Inc., Middleton, WI). Subjects were trained to use TF by voluntarily swaying to draw figures on their tongue, both with and without GVS. Subjects were required to keep the intraoral display in their mouths on all trials, including those that did not provide TF. Subjects performed 24 randomized trials (20 s duration with eyes closed) including four support surface conditions (fixed, rotational sway-referenced, translating the support surface proportional to AP sway, and combined rotational-translational sway-referencing), each repeated twice with and without GVS, and with combined GVS and TF. Postural performance was assessed using deviations from upright (peak-to-peak and RMS sway) and convergence toward stability limits (time and distance to base of support boundaries). Postural stability was impaired with GVS in all platform conditions, with larger decrements in performance during trials with rotation sway-referencing. Electrotactile feedback improved performance with GVS toward non-GVS levels, again with the greatest improvement during trials with rotation sway-referencing. These results demonstrate the effectiveness of tongue electrotactile feedback in providing sensory substitution to maintain postural stability with distorted vestibular input.

Recent bed rest results and countermeasure development at NASA

NASA Technical Reports Server (NTRS)

Hargens, A. R.

1994-01-01

Bedrest studies of normal subjects provide opportunities to understand physiologic responses to supine posture and inactivity. Furthermore, head-down tilt has been a valuable procedure to investigate adaptation to microgravity and development of countermeasures to maintain the health and well-being of humans during space-flight. Recent bedrest experiments at NASA have ranged in duration from a few hours to 17 weeks. Acute studies of 6 degrees head-down tilt indicate that elevation of capillary blood pressure from 28 to 34 mm Hg and increased capillary perfusion in tissues of the head cause facial and intracranial edema. Intracranial pressure increases from 2 to 17 mm Hg going from upright posture to 6 degrees head-down tilt. Microvessels of the head have a low capacity to constrict and diminish local perfusion. Elevation of blood and tissue fluid pressures/flow in the head may also explain the higher headward bone density associated with long-term head-down tilt. These mechanistic studies of head-down tilt, along with a better understanding of the relative stresses involved with upright posture and lower body negative pressure, have facilitated development of suitable physiologic countermeasures to maintain astronaut health during microgravity. Presently no exercise hardware is available to provide a blood pressure gradient from head to feet in space. However, recent studies in our laboratory suggest that treadmill exercise using a graded lower-body compression suit and 100 mmHg lower body negative pressure provides equivalent or greater physiologic stress than similar upright exercise on Earth. Therefore, exercise within a lower body negative pressure chamber may provide a cost-effective and simple countermeasure to maintain the cardiovascular and neuro-musculoskeletal systems of astronauts during long-duration flight.

A link-segment model of upright human posture for analysis of head-trunk coordination

NASA Technical Reports Server (NTRS)

Nicholas, S. C.; Doxey-Gasway, D. D.; Paloski, W. H.

1998-01-01

Sensory-motor control of upright human posture may be organized in a top-down fashion such that certain head-trunk coordination strategies are employed to optimize visual and/or vestibular sensory inputs. Previous quantitative models of the biomechanics of human posture control have examined the simple case of ankle sway strategy, in which an inverted pendulum model is used, and the somewhat more complicated case of hip sway strategy, in which multisegment, articulated models are used. While these models can be used to quantify the gross dynamics of posture control, they are not sufficiently detailed to analyze head-trunk coordination strategies that may be crucial to understanding its underlying mechanisms. In this paper, we present a biomechanical model of upright human posture that extends an existing four mass, sagittal plane, link-segment model to a five mass model including an independent head link. The new model was developed to analyze segmental body movements during dynamic posturography experiments in order to study head-trunk coordination strategies and their influence on sensory inputs to balance control. It was designed specifically to analyze data collected on the EquiTest (NeuroCom International, Clackamas, OR) computerized dynamic posturography system, where the task of maintaining postural equilibrium may be challenged under conditions in which the visual surround, support surface, or both are in motion. The performance of the model was tested by comparing its estimated ground reaction forces to those measured directly by support surface force transducers. We conclude that this model will be a valuable analytical tool in the search for mechanisms of balance control.

In Vivo Spinal Posture during Upright and Reclined Sitting in an Office Chair

PubMed Central

Zemp, Roland; Taylor, William R.; Lorenzetti, Silvio

2013-01-01

Increasing numbers of people spend the majority of their working lives seated in an office chair. Musculoskeletal disorders, in particular low back pain, resulting from prolonged static sitting are ubiquitous, but regularly changing sitting position throughout the day is thought to reduce back problems. Nearly all currently available office chairs offer the possibility to alter the backrest reclination angles, but the influence of changing seating positions on the spinal column remains unknown. In an attempt to better understand the potential to adjust or correct spine posture using adjustable seating, five healthy subjects were analysed in an upright and reclined sitting position conducted in an open, upright MRI scanner. The shape of the spine, as described using the vertebral bodies' coordinates, wedge angles, and curvature angles, showed high inter-subject variability between the two seating positions. The mean lumbar, thoracic, and cervical curvature angles were 29 ± 15°, −29 ± 4°, and 13 ± 8° for the upright and 33 ± 12°, −31 ± 7°, and 7 ± 7° for the reclined sitting positions. Thus, a wide range of seating adaptation is possible through modification of chair posture, and dynamic seating options may therefore provide a key feature in reducing or even preventing back pain caused by prolonged static sitting. PMID:24175307

Temporal parameter change of human postural control ability during upright swing using recursive least square method

NASA Astrophysics Data System (ADS)

Goto, Akifumi; Ishida, Mizuri; Sagawa, Koichi

2010-01-01

The purpose of this study is to derive quantitative assessment indicators of the human postural control ability. An inverted pendulum is applied to standing human body and is controlled by ankle joint torque according to PD control method in sagittal plane. Torque control parameters (KP: proportional gain, KD: derivative gain) and pole placements of postural control system are estimated with time from inclination angle variation using fixed trace method as recursive least square method. Eight young healthy volunteers are participated in the experiment, in which volunteers are asked to incline forward as far as and as fast as possible 10 times over 10 [s] stationary intervals with their neck joint, hip joint and knee joint fixed, and then return to initial upright posture. The inclination angle is measured by an optical motion capture system. Three conditions are introduced to simulate unstable standing posture; 1) eyes-opened posture for healthy condition, 2) eyes-closed posture for visual impaired and 3) one-legged posture for lower-extremity muscle weakness. The estimated parameters Kp, KD and pole placements are applied to multiple comparison test among all stability conditions. The test results indicate that Kp, KD and real pole reflect effect of lower-extremity muscle weakness and KD also represents effect of visual impairment. It is suggested that the proposed method is valid for quantitative assessment of standing postural control ability.

Upright exercise or supine lower body negative pressure exercise maintains exercise responses after bed rest

NASA Technical Reports Server (NTRS)

Lee, S. M.; Bennett, B. S.; Hargens, A. R.; Watenpaugh, D. E.; Ballard, R. E.; Murthy, G.; Ford, S. R.; Fortney, S. M.

1997-01-01

Adaptation to bed rest or space flight is accompanied by an impaired ability to exercise in an upright position. We hypothesized that a daily, 30-min bout of intense, interval exercise in upright posture or supine against lower body negative pressure (LBNP) would maintain upright exercise heart rate and respiratory responses after bed rest. Twenty-four men (31 +/- 3 yr) underwent 5 d of 6 degree head-down tilt: eight performed no exercise (CON), eight performed upright treadmill exercise (UPex), and eight performed supine treadmill exercise against LBNP at -51.3 +/- 0.4 mm Hg (LBNPex). Submaximal treadmill exercise responses (56, 74, and 85% of VO2peak) were measured pre- and post-bed rest. In CON, submaximal heart rate, respiratory exchange ratio, and ventilation were significantly greater (P < or = 0.05) after bed rest. In UPex and LBNPex, submaximal exercise responses were similar pre- and post-bed rest. Our results indicate that a daily 30-min bout of intense, interval upright exercise training or supine exercise training against LBNP is sufficient to maintain upright exercise responses after 5 d of bed rest. These results may have important implications for the development of exercise countermeasures during space flight.

Gaze and viewing angle influence visual stabilization of upright posture

PubMed Central

Ustinova, KI; Perkins, J

2011-01-01

Focusing gaze on a target helps stabilize upright posture. We investigated how this visual stabilization can be affected by observing a target presented under different gaze and viewing angles. In a series of 10-second trials, participants (N = 20, 29.3 ± 9 years of age) stood on a force plate and fixed their gaze on a figure presented on a screen at a distance of 1 m. The figure changed position (gaze angle: eye level (0°), 25° up or down), vertical body orientation (viewing angle: at eye level but rotated 25° as if leaning toward or away from the participant), or both (gaze and viewing angle: 25° up or down with the rotation equivalent of a natural visual perspective). Amplitude of participants’ sagittal displacement, surface area, and angular position of the center of gravity (COG) were compared. Results showed decreased COG velocity and amplitude for up and down gaze angles. Changes in viewing angles resulted in altered body alignment and increased amplitude of COG displacement. No significant changes in postural stability were observed when both gaze and viewing angles were altered. Results suggest that both the gaze angle and viewing perspective may be essential variables of the visuomotor system modulating postural responses. PMID:22398978

Mechanism of Headward Fluid Shift During Exposure To Microgravity

NASA Technical Reports Server (NTRS)

Hargens, Alan R.; Parazynski, Scott E.; Watenpaugh, Donald E.; Aratow, Michael; Murthy, Gita; Kawai, Yasuaki

1994-01-01

A prominent feature of early cardiovascular adaptation to the microgravity of space flight is a shift of blood and tissue fluid from the lower body to the upper body. Symptoms of this fluid shift include facial edema, nasal congestion, and headache. Normally on Earth, the human body is exposed to hydrostatic (gravitational) blood pressure gradients during upright posture. In this posture, mean arterial pressures at head, heart, and foot levels are approximately 70, 100, and 200 mm Hg, respectively. Theoretically, all hydrostatic pressures within arteries and veins are lost during exposure to microgravity so that mean arterial pressure in all regions of the body is uniform and approximately equal to that at heart level (100 mm Hg). Acute studies of 60 head-down tilt (simulated microgravity on Earth) indicate that facial edema is caused by: 1) elevation of capillary blood pressure from 28 to 34 mm Hg, 2) reduction of blood colloid osmotic pressure 22 to 18 mm Hg, and 3) 50% increase of blood perfusion in tissues of the head. Furthermore, as compared to microvasculature in the feet, microvessels of the head have a low capacity to constrict and diminish local perfusion. Elevation of blood and tissue fluid pressures/flow in the head may also explain the higher headward bone density associated with long-term head-down tilt. These mechanistic studies of head-down tilt, along with a better understanding of the relative stresses involved with upright posture and lower body negative pressure, have facilitated development of physiologic countermeasures to maintain astronaut health during microgravity. Presently no exercise hardware is available to provide a blood pressure gradient from head to feet in space. However, recent studies in our laboratory suggest that treadmill exercise within lower body negative pressure provides equivalent or greater physiologic stress as compared to similar upright exercise on Earth.

Contributions of visual and embodied expertise to body perception.

PubMed

Reed, Catherine L; Nyberg, Andrew A; Grubb, Jefferson D

2012-01-01

Recent research has demonstrated that our perception of the human body differs from that of inanimate objects. This study investigated whether the visual perception of the human body differs from that of other animate bodies and, if so, whether that difference could be attributed to visual experience and/or embodied experience. To dissociate differential effects of these two types of expertise, inversion effects (recognition of inverted stimuli is slower and less accurate than recognition of upright stimuli) were compared for two types of bodies in postures that varied in typicality: humans in human postures (human-typical), humans in dog postures (human-atypical), dogs in dog postures (dog-typical), and dogs in human postures (dog-atypical). Inversion disrupts global configural processing. Relative changes in the size and presence of inversion effects reflect changes in visual processing. Both visual and embodiment expertise predict larger inversion effects for human over dog postures because we see humans more and we have experience producing human postures. However, our design that crosses body type and typicality leads to distinct predictions for visual and embodied experience. Visual expertise predicts an interaction between typicality and orientation: greater inversion effects should be found for typical over atypical postures regardless of body type. Alternatively, embodiment expertise predicts a body, typicality, and orientation interaction: larger inversion effects should be found for all human postures but only for atypical dog postures because humans can map their bodily experience onto these postures. Accuracy data supported embodiment expertise with the three-way interaction. However, response-time data supported contributions of visual expertise with larger inversion effects for typical over atypical postures. Thus, both types of expertise affect the visual perception of bodies.

Tactile Sensory Supplementation of Gravitational References to Optimize Sensorimotor Recovery

NASA Technical Reports Server (NTRS)

Black, F. O.; Paloski, W. H.; Bloomberg, J. J.; Wood, S. J.

2007-01-01

Integration of multi-sensory inputs to detect tilts relative to gravity is critical for sensorimotor control of upright orientation. Displaying body orientation using electrotactile feedback to the tongue has been developed by Bach-y- Rita and colleagues as a sensory aid to maintain upright stance with impaired vestibular feedback. This investigation has explored the effects of Tongue Elecrotactile Feedback (TEF) for control of posture and movement as a sensorimotor countermeasure, specifically addressing the optimal location of movement sensors.

Biomechanical analysis of low back load when sneezing.

PubMed

Hasegawa, Tetsuya; Katsuhira, Junji; Matsudaira, Ko; Iwakiri, Kazuyuki; Maruyama, Hitoshi

2014-09-01

Although sneezing is known to induce low back pain, there is no objective data of the load generated when sneezing. Moreover, the approaches often recommended for reducing low back pain, such as leaning with both hands against a wall, are not supported by objective evidence. Participants were 12 healthy young men (mean age 23.25 ± 1.54 years) with no history of spinal column pain or low back pain. Measurements were taken using a three-dimensional motion capture system and surface electromyograms in three experimental conditions: normal for sneezing, characterized by forward trunk inclination; stand, in which the body was deliberately maintained in an upright posture when sneezing; and table, in which the participants leaned with both hands on a table when sneezing. We analyzed and compared the intervertebral disk compressive force, low back moment, ground reaction force, trunk inclination angle, and co-contraction of the rectus abdominis and erector spinae muscles in the three conditions. The intervertebral disk compressive force and ground reaction force were significantly lower in the stand and table conditions than in the normal condition. The co-contraction index value was significantly higher in the stand condition than in the normal and table conditions. When sneezing, body posture in the stand or table condition can reduce load on the low back compared with body posture in the normal sneezing condition. Thus, placing both hands on a table or otherwise maintaining an upright body posture appears to be beneficial for reducing low back load when sneezing. Copyright © 2014 Elsevier B.V. All rights reserved.

A multicentre randomized controlled trial of gentle assisted pushing in the upright posture (GAP) or upright posture alone compared with routine practice to reduce prolonged second stage of labour (the Gentle Assisted Pushing study): study protocol.

PubMed

Hofmeyr, G Justus; Singata, Mandisa; Lawrie, Theresa; Vogel, Joshua P; Landoulsi, Sihem; Seuc, Armando H; Gülmezoglu, A Metin

2015-12-16

Fundal pressure (pushing on the upper part of the uterus in the direction of the birth canal) is often performed in routine practice, however the benefit and indications for its use are unclear and vigorous pressure is potentially harmful. There is some evidence that it may be applied routinely or to expedite delivery in some situations (e.g. fetal distress or maternal exhaustion), particularly in settings where other methods of achieving delivery (forceps, vacuum) are not available. Gentle assisted pushing (GAP) is an innovative method of applying gentle but steady pressure to the uterine fundus with the woman in an upright posture. This trial aims to evaluate the use of GAP in an upright posture, or upright posture alone, on reducing the mean time of delivery and the associated maternal and neonatal complications in women not having delivered following 15-30 min in the second stage of labour. We will conduct a multicentre, randomized, unblinded, controlled trial with three parallel arms (1:1:1). 1,145 women will be randomized at three hospitals in South Africa. Women will be eligible for inclusion if they are ≥18 years old, nulliparous, gestational age ≥ 35 weeks, have a singleton pregnancy in cephalic presentation and vaginal delivery anticipated. Women with chronic medical conditions or obstetric complications are not eligible. If eligible women are undelivered following 15-30 min in the second stage of labour, they will be randomly assigned to: 1) GAP in the upright posture, 2) upright posture only and 3) routine practice (recumbent/supine posture). The primary outcome is the mean time from randomization to complete delivery. Secondary outcomes include operative delivery, adverse neonatal outcomes, maternal adverse events and discomfort. This trial will establish whether upright posture and/or a controlled method of applying fundal pressure (GAP) can improve labour outcomes for women and their babies. If fundal pressure is found to have a measurable beneficial effect, this gentle approach can be promoted as a replacement for the uncontrolled methods currently in use. If it is not found to be useful, fundal pressure can be discouraged.

Fingertip contact influences human postural control

NASA Technical Reports Server (NTRS)

Jeka, J. J.; Lackner, J. R.

1994-01-01

Touch and pressure stimulation of the body surface can strongly influence apparent body orientation, as well as the maintenance of upright posture during quiet stance. In the present study, we investigated the relationship between postural sway and contact forces at the fingertip while subjects touched a rigid metal bar. Subjects were tested in the tandem Romberg stance with eyes open or closed under three conditions of fingertip contact: no contact, touch contact (< 0.98 N of force), and force contact (as much force as desired). Touch contact was as effective as force contact or sight of the surroundings in reducing postural sway when compared to the no contact, eyes closed condition. Body sway and fingertip forces were essentially in phase with force contact, suggesting that fingertip contact forces are physically counteracting body sway. Time delays between body sway and fingertip forces were much larger with light touch contact, suggesting that the fingertip is providing information that allows anticipatory innervation of musculature to reduce body sway. The results are related to observations on precision grip as well as the somatosensory, proprioceptive, and motor mechanisms involved in the reduction of body sway.

The relationship between hippocampal volume and static postural sway: results from the GAIT study.

PubMed

Beauchet, Olivier; Barden, John; Liu-Ambrose, Teresa; Chester, Victoria L; Szturm, Tony; Allali, Gilles

2016-02-01

The role of the hippocampus in postural control, in particular in maintaining upright stance, has not been fully examined in normal aging. This study aims to examine the association of postural sway with hippocampal volume while maintaining upright stance in healthy older individuals. Seventy healthy individuals (mean age 69.7 ± 3.4 years; 41.4 % women) were recruited in this study based on cross-sectional design. Hippocampal volume (quantified from a three-dimensional T1-weighted MRI using semi-automated software), three center of pressure (COP) motion parameters (sway area, path length of anterior-posterior (AP) and medial-lateral (ML) displacement) while maintaining upright stance (eyes open and closed), and the relative difference between open and closed eye conditions were used as outcome measures. Age, sex, body mass index, lower limb proprioception, distance vision, 15-item geriatric depression scale score, total cranial volume, and white matter abnormalities were used as covariates. The sway area decreased from open to closed eye condition but this variation was non-significant (P = 0.244), whereas path length of AP and ML displacement increased significantly (P < 0.003). Increase in sway area from open to closed eyes was associated with greater hippocampal volume (β -18.21; P = 0.044), and a trend for an association of increase in path length of AP displacement (P = 0.075 for open eyes and P = 0.071 for closed eyes) with greater hippocampal volume was reported. The hippocampus is involved in upright postural control in normal aging, such that an increase in sway area of COP motion from open to closed eyes is associated with greater hippocampal volume in healthy older adults.

Posterior thalamic hemorrhage induces "pusher syndrome".

PubMed

Karnath, Hans-Otto; Johannsen, Leif; Broetz, Doris; Küker, Wilhelm

2005-03-22

Recent findings argue for a pathway in humans for sensing the orientation of gravity and controlling upright body posture, separate from the one for orientation perception of the visual world. Stroke patients with contraversive pushing were shown to experience their body as oriented upright when actually tilted about 20 degrees to the ipsilesional side, in spite of normal visual-vestibular functioning. A recent study suggested the involvement of posterolateral thalamus typically associated with the disorder. To evaluate the relationship between pushing behavior and thalamic function. Over a 3-year period the authors prospectively investigated 40 patients with left- or right-sided thalamic strokes. Twenty-eight percent showed contraversive pushing. The authors found a strong relationship between etiology, vascular territory, lesion size, and neurologic disorders associated with contraversive pushing. Pusher patients had larger lesions that typically were caused by hemorrhage (vs infarcts) located in the posterior thalamus (vs anterior thalamic lesions in those patients without pushing behavior). A paresis of the contralesional extremities was more frequent and more severe in pusher patients. Further, these patients showed more additional spatial neglect with right thalamic lesions, while they tended to be more aphasic with left thalamic lesions. Posterior thalamus seems to be fundamentally involved in our control of upright body posture. Higher pressure, swelling, and other secondary pathologic processes associated with posterior thalamic hemorrhage (vs thalamic infarction) may provoke contraversive pushing in combination with additional neurologic symptoms.

In vivo locomotor strain in the hindlimb bones of alligator mississippiensis and iguana iguana: implications for the evolution of limb bone safety factor and non-sprawling limb posture

PubMed

Blob; Biewener

1999-05-01

Limb postures of terrestrial tetrapods span a continuum from sprawling to fully upright; however, most experimental investigations of locomotor mechanics have focused on mammals and ground-dwelling birds that employ parasagittal limb kinematics, leaving much of the diversity of tetrapod locomotor mechanics unexplored. This study reports measurements of in vivo locomotor strain from the limb bones of lizard (Iguana iguana) and crocodilian (Alligator mississippiensis) species, animals from previously unsampled phylogenetic lineages with non-parasagittal limb posture and kinematics. Principal strain orientations and shear strain magnitudes indicate that the limb bones of these species experience considerable torsion during locomotion. This contrasts with patterns commonly observed in mammals, but matches predictions from kinematic observations of axial rotation in lizard and crocodilian limbs. Comparisons of locomotor load magnitudes with the mechanical properties of limb bones in Alligator and Iguana indicate that limb bone safety factors in bending for these species range from 5.5 to 10.8, as much as twice as high as safety factors previously calculated for mammals and birds. Limb bone safety factors in shear (3.9-5.4) for Alligator and Iguana are also moderately higher than safety factors to yield in bending for birds and mammals. Finally, correlations between limb posture and strain magnitudes in Alligator show that at some recording locations limb bone strains can increase during upright locomotion, in contrast to expectations based on size-correlated changes in posture among mammals that limb bone strains should decrease with the use of an upright posture. These data suggest that, in some lineages, strain magnitudes may not have been maintained at constant levels through the evolution of a non-sprawling posture unless the postural change was accompanied by a shift to parasagittal kinematics or by an evolutionary decrease in body size.

The association between later cortical potentials and later phases of postural reactions evoked by perturbations to upright stance.

PubMed

Quant, Sylvia; Maki, Brian E; McIlroy, William E

2005-06-24

Previous studies have suggested that early cortical potentials (e.g. N1) that are evoked by perturbations to upright stance are associated with sensory processing of the initial perturbation and that later potentials may represent cognitive processing of this perturbation. However, it has also been suggested that later cortical potentials could reflect sensory and motor processing of later phases of the postural reaction. The current study set out to provide additional insight into the association between perturbation-evoked cortical potentials and postural reactions evoked by whole-body perturbations. By altering the deceleration onset of the perturbation, which altered the timing of later postural responses, we determined whether changes in later postural responses were associated with changes in later potentials. Based on previous work, we hypothesized that later potentials would not be associated with changes in later postural responses. During stance, seven healthy young adults were instructed to maintain their balance following two types of perturbations: (1) acceleration phase immediately followed by a deceleration phase (TASK 1), and (2) acceleration phase followed by a delayed deceleration phase (TASK 2). In spite of profound task differences in later postural responses, results revealed no significant differences in later potentials. This work provides additional support for the idea that latter elements of perturbation-evoked cortical responses are likely independent of evoked motor reactions required to maintain stability.

Development of a sliding mode control model for quiet upright stance.

PubMed

Zhang, Hongbo; Nussbaum, Maury A; Agnew, Michael J

2016-02-01

Human upright stance appears maintained or controlled intermittently, through some combination of passive and active ankle torques, respectively representing intrinsic and contractile contributions of the ankle musculature. Several intermittent postural control models have been proposed, though it has been challenging to accurately represent actual kinematics and kinetics and to separately estimate passive and active ankle torque components. Here, a simplified single-segment, 2D (sagittal plane) sliding mode control model was developed for application to track kinematics and kinetics during upright stance. The model was implemented and evaluated using previous experimental data consisting of whole body angular kinematics and ankle torques. Tracking errors for the whole-body center-of-mass (COM) angle and angular velocity, as well as ankle torque, were all within ∼10% of experimental values, though tracking performance for COM angular acceleration was substantially poorer. The model also enabled separate estimates of the contributions of passive and active ankle torques, with overall contributions estimated here to be 96% and 4% of the total ankle torque, respectively. Such a model may have future utility in understanding human postural control, though additional work is needed, such as expanding the model to multiple segments and to three dimensions. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

Gender differences in body-sway factors of center of foot pressure in a static upright posture and under the influence of alcohol intake.

PubMed

Kitabayashi, Tamotsu; Demura, Shinichi; Noda, Masahiro; Yamada, Takayoshi

2004-07-01

This study aimed to examine gender differences in 4 body-sway factors of the center of foot pressure (CFP) during a static upright posture and the influence of alcohol intake on them. Four body-sway factors were interpreted in previous studies using factor analysis (the principal factor method and oblique solution by promax-rotation) on 220 healthy young males and females as follows; unit time sway, front-back sway, left-right sway and high frequency band power. The CFP measurement for 1 min was carried out twice with 1 min rest. The measurements of blood pressure, heart rate, whole body reaction time, standing on one leg with eyes closed, and CFP were carried out before and after the alcohol intake using 11 healthy young males and females. The measurement device used was an Anima's stabilometer G5500. The data sampling frequency was 20 Hz. Reliability of 4 body-sway factors was very high. Significant gender differences were found in the left-right sway and the high frequency band power factors, but the influence on body-sway is, as a whole, can be disregarded. These four sway factors can determine the influence of alcohol intake as efficient as 32 sway parameters.

Topsy-turvy locomotion: biomechanical specializations of the elbow in suspended quadrupeds reflect inverted gravitational constraints

PubMed Central

Fujiwara, Shin-ichi; Endo, Hideki; Hutchinson, John R

2011-01-01

Some tetrapods hang upside down from tree branches when moving horizontally. The ability to walk in quadrupedal suspension has been acquired independently in at least 14 mammalian lineages. During the stance (supportive) phase of quadrupedal suspension, the elbow joint flexor muscles (not the extensors as in upright vertebrates moving overground) are expected to contract to maintain the flexed limb posture. Therefore muscular control in inverted, suspended quadrupeds may require changes of muscle control, and even morphologies, to conditions opposite to those in upright animals. However, the relationships between musculoskeletal morphologies and elbow joint postures during the stance phase in suspended quadrupeds have not been investigated. Our analysis comparing postures and skeletal morphologies in Choloepus (Pilosa), Pteropus (Chiroptera), Nycticebus (Primates) and Cynocephalus (Dermoptera) revealed that the elbow joints of these animals were kept at flexed angles of 70–100 ° during the stance phase of quadrupedal suspension. At these joint angles the moment arms of the elbow joint flexors were roughly maximized, optimizing that component of antigravity support. Our additional measurements from various mammalian species show that suspended quadrupeds have relatively small extensor/flexor ratios in both muscle masses and maximum moment arms. Thus, in contrast to the pattern in normal terrestrial quadrupeds, suspended quadrupeds emphasize flexor over extensor muscles for body support. This condition has evolved independently multiple times, attendant with a loss or reduction of the ability to move in normal upright postures. PMID:21477151

Hemodynamic Response of the Supplementary Motor Area during Locomotor Tasks with Upright versus Horizontal Postures in Humans

PubMed Central

Obayashi, Shigeru; Nakajima, Katsumi; Hara, Yukihiro

2016-01-01

To understand cortical mechanisms related to truncal posture control during human locomotion, we investigated hemodynamic responses in the supplementary motor area (SMA) with quadrupedal and bipedal gaits using functional near-infrared spectroscopy in 10 healthy adults. The subjects performed three locomotor tasks where the degree of postural instability varied biomechanically, namely, hand-knee quadrupedal crawling (HKQuad task), upright quadrupedalism using bilateral Lofstrand crutches (UpQuad task), and typical upright bipedalism (UpBi task), on a treadmill. We measured the concentration of oxygenated hemoglobin (oxy-Hb) during the tasks. The oxy-Hb significantly decreased in the SMA during the HKQuad task, whereas it increased during the UpQuad task. No significant responses were observed during the UpBi task. Based on the degree of oxy-Hb responses, we ranked these locomotor tasks as UpQuad > UpBi > HKQuad. The order of the different tasks did not correspond with postural instability of the tasks. However, qualitative inspection of oxy-Hb time courses showed that oxy-Hb waveform patterns differed between upright posture tasks (peak-plateau-trough pattern for the UpQuad and UpBi tasks) and horizontal posture task (downhill pattern for the HKQuad task). Thus, the SMA may contribute to the control of truncal posture accompanying locomotor movements in humans. PMID:27413555

Orthostatic stress is necessary to maintain the dynamic range of cardiovascular control in space

NASA Technical Reports Server (NTRS)

Baisch, J. F.; Wolfram, G.; Beck, L.; Drummer, C.; Stormer, I.; Buckey, J.; Blomqvist, G.

2000-01-01

In the upright position, gravity fills the low-pressure systems of human circulation with blood and interstitial fluid in the sections below the diaphragm. Without gravity one pressure component in the vessels disappears and the relationship between hydrostatic pressure and oncotic pressure, which regulates fluid passage across the capillary endothelium in the terminal vascular bed, shifts constantly. The visible consequences of this are a puffy face and "bird" legs. The plasma volume shrinks in space and the range of cardiovascular control is reduced. When they stand up for the first time after landing, 30-50% of astronauts suffer from orthostatic intolerance. It remains unclear whether microgravity impairs cardiovascular reflexes, or whether it is the altered volume status that causes the cardiovascular instability following space flight. Lower body negative pressure was used in several space missions to stimulate the cardiovascular reflexes before, during and after a space flight. The results show that cardiovascular reflexes are maintained in microgravity. However, the astronauts' volume status changed in space, towards a volume-retracted state, as measurements of fluid-regulating hormones have shown. It can be hypothesized that the control of circulation and body fluid homeostasis in humans is adapted to their upright posture in the Earth's gravitational field. Autonomic control regulates fluid distribution to maintain the blood pressure in that posture, which most of us have to cope with for two-thirds of the day. A determined amount of interstitial volume is necessary to maintain the dynamic range of cardiovascular control in the upright posture; otherwise orthostatic intolerance may occur more often.

Sleep deprivation affects sensorimotor coupling in postural control of young adults.

PubMed

Aguiar, Stefane A; Barela, José A

2014-06-27

Although impairments in postural control have been reported due to sleep deprivation, the mechanisms underlying such performance decrements still need to be uncovered. The purpose of this study was to investigate the effects of sleep deprivation on the relationship between visual information and body sway in young adults' postural control. Thirty adults who remained awake during one night and 30 adults who slept normally the night before the experiment participated in this study. The moving room paradigm was utilized, manipulating visual information through the movement of a room while the floor remained motionless. Subjects stood upright inside of a moving room during four 60-s trials. In the first trial the room was kept stationary and in the following trials the room moved with a frequency of 0.2Hz, peak velocity of 0.6cm/s and 0.9cm peak-to-peak amplitude. Body sway and room displacement were measured through infrared markers. Results showed larger and faster body sway in sleep deprived subjects with and without visual manipulation. The magnitude with which visual stimulus influenced body sway and its temporal relationship were unaltered in sleep deprived individuals, but they became less coherent and more variable as they had to maintain upright stance during trials. These results indicate that after sleep deprivation adults become less stable and accurate in relating visual information to motor action, and this effect is observed after only a brief period performing postural tasks. The low cognitive load employed in this task suggests that attentional difficulties are not the only factor leading to sensorimotor coupling impairments observed following sleep deprivation. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Use of Body Armor Protection Levels with Squad Automatic Weapon Fighting Load Impacts Soldier Performance, Mobility, and Postural Control

DTIC Science & Technology

2015-05-01

changes have been historically seen with the heavier approach march load between 21 kg and 33 kg (Schiffman et al., 2006, and Harman et al., 1999) or...the heaviest emergency approach march load greater than 32 kg (Attwells et al., 2006, and Harman et al., 1999). Increasing ballistic protection...vital to maintaining upright posture while walking ( Harman et al., 1999). Alterations made lower in the kinematic chain, such as the hip flexion

Advantages and disadvantages of stiffness instructions when studying postural control.

PubMed

Bonnet, Cédrick T

2016-05-01

To understand the maintenance of upright stance, researchers try to discover the fundamental mechanisms and attentional resources devoted to postural control and eventually to the performance of other tasks (e.g., counting in the head). During their studies, some researchers require participants to stand as steady as possible and other simply ask participants to stand naturally. Surprisingly, a clear and direct explanation of the usefulness of the steadiness requirement seems to be lacking, both in experimental and methodological discussions. Hence, the objective of the present note was to provide advantages and disadvantages of this steadiness requirement in studies of postural control. The advantages may be to study fundamental postural control, to eliminate useless postural variability, to control spurious body motions and to control the participants' thoughts. As disadvantages, this steadiness requirement only leads to study postural control in unnatural upright stance, it changes the focus of attention (internal vs. external) and the nature of postural control (unconscious vs. conscious), it increases the difficulty of a supposedly easy control task and it eliminates or reduces the opportunity to record exploratory behaviors. When looking carefully at the four advantages of the steadiness requirement, one can believe that they are, in fact, more disadvantageous than advantageous. Overall therefore, this requirement seems illegitimate and it is proposed that researchers should not use it in the study of postural control. They may use this requirement only if they search to know the limit until which participants can consciously reduce their postural sway. Copyright © 2015 Elsevier B.V. All rights reserved.

The influence of seat height, trunk inclination and hip posture on the activity of the superior trapezius and longissimus

PubMed Central

Bertolaccini, Guilherme da Silva; Nakajima, Rafael Kendi; Filho, Idinei Francisco Pires de Carvalho; Paschoarelli, Luis Carlos; Medola, Fausto Orsi

2016-01-01

[Purpose] This study was aimed at investigating the influence of seat height and body posture on the activity of the superior trapezius and longissimus muscles. [Subjects and Methods] Twenty two healthy subjects were instructed to perform a total of eight different body postures, varying according three main factors: seat height (low and high seat); trunk inclination (upright and leaning forward at 45°); and the hips in abduction and adduction. Electromyography of the superior trapezius and longissimus was collected bilaterally, and the average values were obtained and compared across all the postures. [Results] The activity of the superior trapezius and longissimus significantly changes according to the seat height and trunk inclination. For both seat heights, sitting with trunk leaning forward resulted in a significant increase in the activity of both muscles. When sitting in a high seat and the trunk leaning forward, the superior trapezius activity was significantly reduced when compared to the same posture in a low seat. [Conclusion] This study contributes to the knowledge on the influence of the body posture and seat configuration on the activity of postural muscles. Reducing the biomechanical loads on the postural muscles must be targeted in order to improve users’ comfort and safety. PMID:27313381

Mechanics of limb bone loading during terrestrial locomotion in the green iguana (Iguana iguana) and American alligator (Alligator mississippiensis).

PubMed

Blob, R W; Biewener, A A

2001-03-01

In vivo measurements of strain in the femur and tibia of Iguana iguana (Linnaeus) and Alligator mississippiensis (Daudin) have indicated three ways in which limb bone loading in these species differs from patterns observed in most birds and mammals: (i) the limb bones of I. iguana and A. mississippiensis experience substantial torsion, (ii) the limb bones of I. iguana and A. mississippiensis have higher safety factors than those of birds or mammals, and (iii) load magnitudes in the limb bones of A. mississippiensis do not decrease uniformly with the use of a more upright posture. To verify these patterns, and to evaluate the ground and muscle forces that produce them, we collected three-dimensional kinematic and ground reaction force data from subadult I. iguana and A. mississippiensis using a force platform and high-speed video. The results of these force/kinematic studies generally confirm the loading regimes inferred from in vivo strain measurements. The ground reaction force applies a torsional moment to the femur and tibia in both species; for the femur, this moment augments the moment applied by the caudofemoralis muscle, suggesting large torsional stresses. In most cases, safety factors in bending calculated from force/video data are lower than those determined from strain data, but are as high or higher than the safety factors of bird and mammal limb bones in bending. Finally, correlations between limb posture and calculated stress magnitudes in the femur of I. iguana confirm patterns observed during direct bone strain recordings from A. mississippiensis: in more upright steps, tensile stresses on the anterior cortex decrease, but peak compressive stresses on the dorsal cortex increase. Equilibrium analyses indicate that bone stress increases as posture becomes more upright in saurians because the ankle and knee extensor muscles exert greater forces during upright locomotion. If this pattern of increased bone stress with the use of a more upright posture is typical of taxa using non-parasagittal kinematics, then similar increases in load magnitudes were probably experienced by lineages that underwent evolutionary shifts to a non-sprawling posture. High limb bone safety factors and small body size in these lineages could have helped to accommodate such increases in limb bone stress.

Pusher syndrome--a frequent but little-known disturbance of body orientation perception.

PubMed

Karnath, Hans-Otto

2007-04-01

Disturbances of body orientation perception after brain lesions may specifically relate to only one dimension of space. Stroke patients with "pusher syndrome" suffer from a severe misperception of their body's orientation in the coronal (roll) plane. They experience their body as oriented 'upright' when it is in fact markedly tilted to one side. The patients use the unaffected arm or leg to actively push away from the un-paralyzed side and resist any attempt to passively correct their tilted body posture. Although pusher patients are unable to correctly determine when their own body is oriented in an upright, vertical position, they seem to have no significant difficulty in determining the orientation of the surrounding visual world in relation to their own body. Pusher syndrome is a distinctive clinical disorder occurring characteristically after unilateral left or right brain lesions in the posterior thalamus and -less frequently- in the insula and postcentral gyrus. These structures thus seem to constitute crucial neural substrates controlling human (upright) body orientation in the coronal (roll) plane. A further disturbance of body orientation that predominantly affects a single dimension of space, namely the transverse (yaw) plane, is observed in stroke patients with spatial neglect. Apparently, our brain has evolved separate neural subsystems for perceiving and controlling body orientation in different dimensions of space.

Evaluation of influence of stretching therapy and ergonomic factors on postural control in patients with chronic non-specific low back pain.

PubMed

Gawda, Piotr; Dmoszyńska-Graniczka, Magdalena; Pawlak, Halina; Cybulski, Marek; Kiełbus, Michał; Majcher, Piotr; Buczaj, Agnieszka; Buczaj, Marcin

2015-01-01

The vertical orientation of the body in the upright standing position is maintained by keeping the body's centre of gravity (COG) upright, above the base of support, by a dynamic interplay of visual, vestibular, and somatosensory control systems. The objectives of this study were: to compare the postural control strategy between people with and without low back pain (LBP), to estimate the influence of the stretching therapy on the postural control strategy, and to discover the relationship between the restriction of spine mobility and occurrence of some ergonomic factors. The study consisted of 32 patients with LBP and 25 healthy controls. Postural characteristics of the subjects were measured with the use of a computerized force platform. The software programme filters and measures COG sway velocity in different conditions. Additional measurements and tests were conducted in patients after stretching therapy. Based on survey research, all individuals were selected and evaluated from the aspect of ergonomics. The results of the COG sway velocity vary under the testing conditions. From the aspect of ergonomic attitude and influence of the rehabilitation, results varied in the groups. Ergonomic factors are often accompanied by the appearance of LBP. The restrictions within the musculoskeletal system cause disorders in muscle synergies, which is expressed by an increase in the angular velocity of the COG. In patients with chronic back pain syndrome, selected stretching therapy techniques improves the range of motion of the spine and reduces pain.

Ventral and Dorsal Pathways Relate Differently to Visual Awareness of Body Postures under Continuous Flash Suppression

PubMed Central

Goebel, Rainer

2018-01-01

Abstract Visual perception includes ventral and dorsal stream processes. However, it is still unclear whether the former is predominantly related to conscious and the latter to nonconscious visual perception as argued in the literature. In this study upright and inverted body postures were rendered either visible or invisible under continuous flash suppression (CFS), while brain activity of human participants was measured with functional MRI (fMRI). Activity in the ventral body-sensitive areas was higher during visible conditions. In comparison, activity in the posterior part of the bilateral intraparietal sulcus (IPS) showed a significant interaction of stimulus orientation and visibility. Our results provide evidence that dorsal stream areas are less associated with visual awareness. PMID:29445766

Mechanical Characteristics of Reflex Durign Upright Posture in Paralyzed Subjects

NASA Astrophysics Data System (ADS)

Kim, Yongchul; Youm, Youngil; Lee, Bumsuk; Kim, Youngho; Choi, Hyeonki

The characteristics of flexor reflexes have been investigated in the previous studies with human subjects who were seated or supine position. However, researchers did not describe how the spinal circuits are used in different hip angles for paralyzed subjects, such as the standing position with walker or cane. In upright posture the compatibility between a flexor reflex of leg and body balance is a special problem for lower limb injured subjects. Therefore, the purpose of this study was to investigate the effects of hip angle change on the flexor reflex evoked in standing paralyzed subjects supported by walker. In this study, six spinal cord injured and four stroke subjects were recruited through the inpatient physical therapy clinics of Korea national rehabilitation hospital. A single axis electronic goniometer was mounted on the lateral side of the hip joint of the impaired limb to record movements in the sagittal plane at this joint. The electronic goniometer was connected to a data acquisition system, through amplifiers to a computer. Since subject' posture influenced characteristics of the flexion reflex response, the subjects were supported in an upright posture by the help of parallelogram walder. Two series of tests were performed on each leg. The first series of the tests investigated the influence of hip angle during stationary standing posture on flexion reflex response. The hip angle was adjusted by the foot plate. The second examined the effect of the voluntary action of subject on swing motion during the gait. The electrically induced flexion reflex simultaneously produced the flexion of the hip, knee and dorsiflexion of the ankle enabling the swing phase of walking. Form the experimental results we observed that the reflex response of hip joint was largerwith the hip in the extended position than in the flexed position during standing posture. Under voluntary movement on flexion reflex during gaint, the peak hip angle induced by stimulation was increased in spinal cord injury and stroke patients by subject' voluntary movement.

Analysis of the impact of a cognitive task on the posture of elderly subjects with depression compared with healthy elderly subjects.

PubMed

Casteran, Matthieu; Putot, Alain; Pfitzenmeyer, François; Thomas, Elizabeth; Manckoundia, Patrick

2016-11-01

While previous studies have demonstrated that depressive elderly subjects (DES) experience difficulties in the processing of simultaneous cognitive tasks, few have examined the coupling of cognitive tasks with seemingly 'automatic' tasks, such as standing upright. Current patient management focuses on pharmacological treatments and cognitive-behavioral therapies. Healthy elderly (HES) and non-treated DES were included. Postural sway in DES was compared with that in HES while in single-task and dual-task conditions. The single-task consisted of standing upright. For the dual-task, the subjects recalled various items from memory or counted while standing upright. Postural sway was evaluated by computing the center of pressure (CoP) area and path length. DES showed greater postural sway than HES in all conditions. The HES showed a greater CoP area in the dual-task than in the single-task conditions. In DES, the CoP area in the single-task condition was similar to that in the dual-task condition. The greater postural sway observed in DES may be a cause of a greater risk of falls. We showed that even seemingly automatic tasks, such as maintaining an upright posture, are affected by depression. These results are important for the management of DES. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Effect of posture on the diurnal variation in clinically significant diabetic macular edema.

PubMed

Polito, Antonio; Polini, Giovanni; Chiodini, Raffaella Gortana; Isola, Miriam; Soldano, Franca; Bandello, Francesco

2007-07-01

To investigate the role of posture and other systemic factors in the diurnal variation of clinically significant diabetic macular edema (CSDME). Ten eyes of 10 diabetic subjects with CSDME underwent four OCT foveal thickness measurements with StratusOCT at 9 AM and 12, 3, and 6 PM consecutively on two different days, with the subject in an upright position on one and in a recumbent position on the other. For the "recumbent-position" measurements, the patients were admitted the night before and remained in bed during the entire day of testing. Clinical laboratory results at baseline included HbA1c, urinary albumin, and serum creatinine. Refraction and Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity were also measured before each OCT measurement was taken. Variations in blood pressure, body temperature, plasma glucose, renin, aldosterone, and cortisol levels were measured and then correlated with macular thickness. Foveal thickening decreased in all cases over the course of the day. The decrease, however, was significantly greater for the upright-position measurements (relative mean +/- SD decrease of 20.6% +/- 6.5% in the upright position and 6.2% +/- 4.6% in the recumbent position). Visual acuity improved by at least 1 ETDRS line in three eyes in the upright position as opposed to only one eye in the recumbent position. There seemed to be no association between any of the systemic factors studied and foveal thickening, with the exception of cortisol. The results support the hypothesis that posture and hydrostatic pressure play a major role in determining time-related shifts in CSDME and suggest that the forces of Starling's law can in part, account for CSDME formation.

Quantifying and Reducing Posture-Dependent Distortion in Ballistocardiogram Measurements

PubMed Central

Javaid, Abdul Q.; Wiens, Andrew D.; Fesmire, N. Forrest; Weitnauer, Mary A.; Inan, Omer T.

2015-01-01

Ballistocardiography is a non-invasive measurement of the mechanical movement of the body caused by cardiac ejection of blood. Recent studies have demonstrated that ballistocardiogram (BCG) signals can be measured using a modified home weighing scale, and used to track changes in myocardial contractility and cardiac output. With this approach, the BCG can potentially be used both for preventive screening and for chronic disease management applications. However, for achieving high signal quality, subjects are required to stand still on the scale in an upright position for the measurement; the effects of intentional (for user comfort) or unintentional (due to user error) modifications in the position or posture of the subject during the measurement have not been investigated in the existing literature. In this study, we quantified the effects of different standing and seated postures on the measured BCG signals, and on the most salient BCG-derived features compared to reference standard measurements (e.g., impedance cardiography). We determined that the standing upright posture led to the least distorted signals as hypothesized, and that the correlation between BCG-derived timing interval features (R-J interval) and the pre-ejection period, PEP (measured using ICG), decreased significantly with impaired posture or sitting position. We further implemented two novel approaches to improve the PEP estimates from other standing and sitting postures, using system identification and improved J-wave detection methods. These approaches can improve the usability of standing BCG measurements in unsupervised settings (i.e. the home), by improving the robustness to non-ideal posture, as well as enabling high quality seated BCG measurements. PMID:26058064

Effect of standing on neurohumoral responses and plasma volume in healthy subjects

NASA Technical Reports Server (NTRS)

Jacob, G.; Ertl, A. C.; Shannon, J. R.; Furlan, R.; Robertson, R. M.; Robertson, D.

1998-01-01

Upright posture leads to rapid pooling of blood in the lower extremities and shifts plasma fluid into surrounding tissues. This results in a decrease in plasma volume (PV) and in hemoconcentration. There has been no integrative evaluation of concomitant neurohumoral and PV shifts with upright posture in normal subjects. We studied 10 healthy subjects after 3 days of stable Na+ and K+ intake. PV was assessed by the Evans blue dye method and by changes in hematocrit. Norepinephrine (NE), NE spillover, epinephrine (Epi), vasopressin, plasma renin activity, aldosterone, osmolarity, and kidney response expressed by urine osmolality and by Na+ and K+ excretion of the subjects in the supine and standing postures were all measured. We found that PV fell by 13% (375 +/- 35 ml plasma) over approximately 14 min, after which time it remained relatively stable. There was a concomitant decrease in systolic blood pressure and an increase in heart rate that peaked at the time of maximal decrease in PV. Plasma Epi and NE increased rapidly to this point. Epi approached baseline by 20 min of standing. NE spillover increased 80% and clearance decreased 30% with 30 min of standing. The increase in plasma renin activity correlated with an increase in aldosterone. Vasopressin increased progressively, but there was no change in plasma osmolarity. The kidney response showed a significant decrease in Na+ and an increase in K+ excretion with upright posture. We conclude that a cascade of neurohumoral events occurs with upright posture, some of which particularly coincide with the decrease in PV. Plasma Epi levels may contribute to the increment in heart rate with maintained upright posture.

Effect of body posture on involuntary swallow in healthy volunteers.

PubMed

Shiino, Yoshitaka; Sakai, Shogo; Takeishi, Ryosuke; Hayashi, Hirokazu; Watanabe, Masahiro; Tsujimura, Takanori; Magara, Jin; Ito, Kayoko; Tsukada, Tetsu; Inoue, Makoto

2016-03-01

Clinically, reclining posture has been reported to reduce risk of aspiration. However, during involuntary swallow in reclining posture, changes in orofacial and pharyngeal movement before and during pharyngeal swallow should be considered. Further, the mechanisms underlying the effect of body posture on involuntary swallow remain unclear. The aim of the present study was to determine the effect of body posture on activity patterns of the suprahyoid muscles and on patterns of bolus transport during a natural involuntary swallow. Thirteen healthy male adults participated in a water infusion test and a chewing test. In the water infusion test, thickened water was delivered into the pharynx at a very slow rate until the first involuntary swallow was evoked. In the chewing test, subjects were asked to eat 10 g of gruel rice. In both tests, the recording was performed at four body postures between upright and supine positions. Results showed that reclining changed the location of the bolus head at the start of swallow and prolonged onset latency of the swallowing initiation. Muscle burst duration and whiteout time measured by videoendoscopy significantly increased with body reclining and prolongation of the falling time. In the chewing test, reclining changed the location of the bolus head at the start of swallow, and the frequency of bolus residue after the first swallow increased. Duration and area of EMG burst and whiteout time significantly increased with body reclining. These data suggest that body reclining may result in prolongation of pharyngeal swallow during involuntary swallow. Copyright © 2015 Elsevier Inc. All rights reserved.

Asymmetric balance control between legs for quiet but not for perturbed stance.

PubMed

Vieira, Osvaldo; Coelho, Daniel Boari; Teixeira, Luis Augusto

2014-10-01

Interlateral performance asymmetry in upright balance control was evaluated in this investigation by comparing unipedal stance on the right versus the left leg. Participants were healthy young adults, hand-foot congruent preference for the right body side. Balance performance was evaluated in unperturbed quiet stance and in the recovery of balance stability following a mechanical perturbation induced by unexpected load release. Evaluation was made under availability of full sensory information, and under deprivation of vision combined with distortion of sensory inputs from the feet soles. Results from perturbed posture revealed that muscular response latency and postural sway were symmetric between the legs. Unipedal stance was more stable when the body was supported on the right as compared with the left leg. No interaction was found between leg and sensory condition. Our findings are interpreted as resulting from specialization of the sensorimotor system controlling the right leg for continuous low-magnitude postural adjustments, while corrections to large-scale stance sway are symmetrically controlled between body sides.

Stimulus Control, Transfer and Maintenance of Upright Walking Posture with a Severely Retarded Adult.

ERIC Educational Resources Information Center

Horner, Robert H.

Upright walking posture was successfully trained, maintained, and transferred to a new setting in a 28-year-old profoundly retarded adult. An apparatus in the S's cap and vest provided reinforcement (radio) when the S's head was up. The first four phases of the study demonstrated stimulus control in the training setting, while the next nine phases…

Words That Move Us. The Effects of Sentences on Body Sway

PubMed Central

Stins, John F.; Marmolejo-Ramos, Fernando; Hulzinga, Femke; Wenker, Eric; Cañal-Bruland, Rouwen

2017-01-01

According to the embodied cognition perspective, cognitive systems and perceptuo-motor systems are deeply intertwined and exert a causal effect on each other. A prediction following from this idea is that cognitive activity can result in subtle changes in observable movement. In one experiment, we tested whether reading various sentences resulted in changes in postural sway. Sentences symbolized various human activities involving high, low, or no physical effort. Dutch participants stood upright on a force plate, measuring the body center of pressure, while reading a succession of sentences. High physical effort sentences resulted in more postural sway (greater SD) than low physical effort sentences. This effect only showed up in medio-lateral sway but not anterio-posterior sway. This suggests that sentence comprehension was accompanied by subtle motoric activity, likely mirroring the various activities symbolized in the sentences. We conclude that semantic processing reaches the motor periphery, leading to increased postural activity. PMID:28713451

Accuracy of saccades to remembered targets as a function of body orientation in space

NASA Technical Reports Server (NTRS)

Vogelstein, Joshua T.; Snyder, Lawrence H.; Angelaki, Dora E.

2003-01-01

A vertical asymmetry in memory-guided saccadic eye movements has been previously demonstrated in humans and in rhesus monkeys. In the upright orientation, saccades generally land several degrees above the target. The origin of this asymmetry has remained unknown. In this study, we investigated whether the asymmetry in memory saccades is dependent on body orientation in space. Thus animals performed memory saccades in four different body orientations: upright, left-side-down (LSD), right-side-down (RSD), and supine. Data in all three rhesus monkeys confirm previous observations regarding a significant upward vertical asymmetry. Saccade errors made from LSD and RSD postures were partitioned into components made along the axis of gravity and along the vertical body axis. Up/down asymmetry persisted only in body coordinates but not in gravity coordinates. However, this asymmetry was generally reduced in tilted positions. Therefore the upward bias seen in memory saccades is egocentric although orientation in space might play a modulatory role.

Effects of posture on exercise performance - Measurement by systolic time intervals.

NASA Technical Reports Server (NTRS)

Spodick, D. H.; Quarry-Pigott, V. M.

1973-01-01

Because posture significantly influences cardiac performance, the effects of moderate supine and upright ergometer exercise were compared on the basis of proportional (+37%) rate increments over resting control. Supine exercise produced significant decreases in left ventricular ejection time (LVET), pre-ejection period (PEP), and isovolumic contraction time (IVCT). Ejection time index (ETI) and corrected ejection time (LVETc) did not change significantly. Upright exercise produced greater decreases in PEP and LVET, but despite the rate increase there was no change in LVET, which resulted in sharp increases in ETI and LVETc. The discordant directional effects on LVET and its rate-correcting indices between the two postures were consistent with hemodynamic studies demonstrating lack of stroke volume change during supine exercise and increased stroke volume over control during light to moderate upright exercise.

Coupling of fingertip somatosensory information to head and body sway

NASA Technical Reports Server (NTRS)

Jeka, J. J.; Schoner, G.; Dijkstra, T.; Ribeiro, P.; Lackner, J. R.

1997-01-01

Light touch contact of a fingertip with a stationary surface can provide orientation information that enhances control of upright stance. Slight changes in contact force at the fingertip provide sensory cues about the direction of body sway, allowing attenuation of sway. In the present study, we asked to which extent somatosensory cues are part of the postural control system, that is, which sensory signal supports this coupling? We investigated postural control not only when the contact surface was stationary, but also when it was moving rhythmically (from 0.1 to 0.5 Hz). In doing so, we brought somatosensory cues from the hand into conflict with other parts of the postural control system. Our focus was the temporal relationship between body sway and the contact surface. Postural sway was highly coherent with contact surface motion. Head and body sway assumed the frequency of the moving contact surface at all test frequencies. To account for these results, a simple model was formulated by approximating the postural control system as a second-order linear dynamical system. The influence of the touch stimulus was captured as the difference between the velocity of the contact surface and the velocity of body sway, multiplied by a coupling constant. Comparison of empirical results (relative phase, coherence, and gain) with model predictions supports the hypothesis of coupling between body sway and touch cues through the velocity of the somatosensory stimulus at the fingertip. One subject, who perceived movement of the touch surface, demonstrated weaker coupling than other subjects, suggesting that cognitive mechanisms introduce flexibility into the postural control scheme.

Effects of a prior stretching of the plantarflexor muscles on the capacity to control upright stance maintenance in healthy adults.

PubMed

Rougier, Patrice; Burdet, Cyril; Genthon, Nicolas

2006-10-01

To assess whether prior stretching of a muscle can induce improved postural control, 15 healthy adults stood still upright with their eyes closed before and after a series of bilateral stretches of the triceps surae muscles. The analysis focused on the center of pressure (CP) and the vertical projection of the center of gravity (CGv) trajectories and their difference (CP - CGv). The prolonged stretching induced a forward shift of the mean position of the CGv. The frequency analysis showed a constancy of the amplitudes of both basic movements whereas an increased mean power frequency was seen for the CP - CGv movements. A fractional Brownian motion modeling of the trajectories indicates shortest time intervals and lower covered distances by the CGv before a change in its control occurs along the antero-posterior axis. This reorganization is thought to be a result of improved body movement detection, which allows postural control over the longest time intervals to be triggered more rapidly.

Performing saccadic eye movements or blinking improves postural control.

PubMed

Rougier, Patrice; Garin, Mélanie

2007-07-01

To determine the relationship between eye movement and postural control on an undisturbed upright stance maintenance protocol, 15 young, healthy individuals were tested in various conditions. These conditions included imposed blinking patterns and horizontal and vertical saccadic eye movements. The directions taken by the center of pressure (CP) were recorded via a force platform on which the participants remained in an upright position. The CP trajectories were used to estimate, via a low-pass filter, the vertically projected movements of the center of gravity (CGv) and consequently the difference CP-CGv. An analysis of the frequency shows that regular bilateral blinking does not produce a significant change in postural control. In contrast, performing saccadic eye movements induces some reduced amplitude for both basic CGv and CP-CGv movements principally along the antero-posterior axis. The present result supports the theory that some ocular movements may modify postural control in the maintenance of the upright standing position in human participants.

The effect of trunk flexion on lower-limb kinetics of able-bodied gait.

PubMed

Kluger, David; Major, Matthew J; Fatone, Stefania; Gard, Steven A

2014-02-01

Able-bodied individuals spontaneously adopt crouch gait when walking with induced anterior trunk flexion, but the effect of this adaptation on lower-limb kinetics is unknown. Sustained forward trunk displacement during walking can greatly alter body center-of-mass location and necessitate a motor control response to maintain upright balance. Understanding this response may provide insight into the biomechanical demands on the lower-limb joints of spinal pathology that alter trunk alignment (e.g., flatback). The purpose of this study was to determine the effect of sustained trunk flexion on lower-limb kinetics in able-bodied gait, facilitating understanding of the effects of spinal pathologies. Subjects walked with three postures: 0° (normal upright), 25±7°, and 50±7° trunk flexion. With increased trunk flexion, decreased peak ankle plantar flexor moments were observed with increased energy absorption during stance. Sustained knee flexion during mid- and terminal stance decreased knee flexor moments, but energy absorption/generation remained unchanged across postures. Increased trunk flexion placed significant demand on the hip extensors, thus increasing peak hip extensor moments and energy generation. The direct relationship between trunk flexion and energy absorption/generation at the ankle and hip, respectively, suggest increased muscular demand during gait. These findings on able-bodied subjects might shed light on muscular demands associated with individuals having pathology-induced positive sagittal spine balance. Copyright © 2013 Elsevier B.V. All rights reserved.

Lumbar spine disc heights and curvature: upright posture vs. supine compression harness

NASA Technical Reports Server (NTRS)

Lee, Shi-Uk; Hargens, Alan R.; Fredericson, Michael; Lang, Philipp K.

2003-01-01

INTRODUCTION: Spinal lengthening in microgravity is thought to cause back pain in astronauts. A spinal compression harness can compress the spine to eliminate lengthening but the loading condition with harness is different than physiologic conditions. Our purpose was to compare the effect of spine compression with a harness in supine position on disk height and spinal curvature in the lumbar spine to that of upright position as measured using a vertically open magnetic resonance imaging system. METHODS: Fifteen healthy subjects volunteered. On day 1, each subject lay supine for an hour and a baseline scan of the lumbar spine was performed. After applying a load of fifty percent of body weight with the harness for thirty minutes, the lumbar spine was scanned again. On day 2, after a baseline scan, a follow up scan was performed after kneeling for thirty minutes within the gap between two vertically oriented magnetic coils. Anterior and posterior disk heights, posterior disk bulging, and spinal curvature were measured from the baseline and follow up scans. RESULTS: Anterior disk heights increased and posterior disk heights decreased compared with baseline scans both after spinal compression with harness and upright posture. The spinal curvature increased by both loading conditions of the spine. DISCUSSION: The spinal compression with specially designed harness has the same effect as the physiologic loading of the spine in the kneeling upright position. The harness shows some promise as a tool to increase the diagnostic capabilities of a conventional MR system.

Electro-tactile stimulation of the posterior neck induces body anteropulsion during upright stance.

PubMed

De Nunzio, A M; Yavuz, U S; Martinez-Valdes, E; Farina, D; Falla, D

2018-05-01

Sensory information conveyed along afferent fibers from muscle and joint proprioceptors play an important role in the control of posture and gait in humans. In particular, proprioceptive information from the neck is fundamental in supplying the central nervous system with information about the orientation and movement of the head relative to the rest of the body. The previous studies have confirmed that proprioceptive afferences originating from the neck region, evoked via muscle vibration, lead to strong body-orienting effects during static conditions (e.g., leaning of the body forwards or backwards, depending on location of vibration). However, it is not yet certain in humans, whether the somatosensory receptors located in the deep skin (cutaneous mechanoreceptors) have a substantive contribution to postural control, as vibratory stimulation encompasses the receptive field of all the somatosensory receptors from the skin to the muscles. The aim of this study was to investigate the postural effect of cutaneous mechanoreceptor afferences using electro-tactile stimulation applied to the neck. Ten healthy volunteers (8M, 2F) were evaluated. The average position of their centre of foot pressure (CoP) was acquired before, during, and after a subtle electro-tactile stimulation over their posterior neck (mean ± SD = 5.1 ± 2.3 mA at 100 Hz-140% of the perception threshold) during upright stance with their eyes closed. The electro-tactile stimulation led to a body-orienting effect with the subjects consistently leaning forward. An average shift of the CoP of 12.1 ± 11.9 mm (mean ± SD) was reported, which significantly (p < 0.05) differed from its average position under a control condition (no stimulation). These results indicate that cutaneous mechanoreceptive inflow from the neck is integrated to control stance. The findings are relevant for the exploitation of electro-tactile stimulation for rehabilitation interventions where induced anteropulsion of the body is desired.

Variations in rest vertical dimension: effects of standing posture in edentulous patients.

PubMed

Makzoume, Joseph E

2007-01-01

The orientation of a patient's head changes, depending on whether he or she is sitting or standing in a relaxed upright position. An edentulous patient's vertical dimension at rest may show variations that can result in an inaccurate determination of his or her occlusal vertical dimension. This study recorded the rest vertical dimension (RVD) established among 60 totally edentulous subjects who were standing in the position of greatest comfort (self-balance position) and compared it with the patients' RVD when they were seated in a relaxed upright position, with the Frankfort Plane parallel to the horizontal. The RVD was measured (in mm) between two dots located on the midline of the face. Two measurements were made: one when the patient was seated upright and relaxed (with the Frankfort Plane parallel to the horizontal) with no head support, and the other when the patient was standing relaxed on both feet in a self-balance position. Five alternated measurements were made for each subject in each position. A mean RVD was calculated for each subject in each body posture and the mean values from both positions were compared. Statistical analysis was performed using Student's t-test (alpha = 0.05). No significant differences were noted between the RVD of the seated and standing positions (P = 0.67).

Space Physiology Studies

NASA Technical Reports Server (NTRS)

Hargens, A. R.; Ballard, R. E.; Boda, W. L.; Ertl, A. C.; Schneider, S. M.; Hutchinson, K. J.; Lee, S. M.; Murthy, G.; Putcha, L.; Watenpaugh, D. E.

1999-01-01

Calculations suggest that exercise in space to date has lacked sufficient loads to maintain musculoskeletal mass. Lower body negative pressure (LBNP) produces a force at the feet equal to the product of the LBNP and body cross-sectional area at the waist. Supine exercise within 50-60 mm Hg LBNP improves tolerance to LBNP and produces forces similar to those occurring during upright posture on Earth. Thus, exercise within LBNP may help prevent deconditioning of astronauts by stressing tissues of the lower body in a manner similar to gravity and also, may provide a safe and effective alternative to centrifugation in terms of cost, mass, volume, and power usage. We hypothesize that supine treadmill exercise during LBNP at one body weight (50-60 mm Hg LBNP) will provide cardiovascular and musculoskeletal loads similar to those experienced while upright in lg. Also, daily supine treadmill running in a LBNP chamber will maintain aerobic fitness, orthostatic tolerance, and musculoskeletal structure and function during bed rest (simulated microgravity).

Stiffness and Damping in Postural Control Increase with Age

PubMed Central

Cenciarini, Massimo; Loughlin, Patrick J.; Sparto, Patrick J.; Redfern, Mark S.

2011-01-01

Upright balance is believed to be maintained through active and passive mechanisms, both of which have been shown to be impacted by aging. A compensatory balance response often observed in older adults is increased co-contraction, which is generally assumed to enhance stability by increasing joint stiffness. We investigated the effect of aging on standing balance by fitting body sway data to a previously-developed postural control model that includes active and passive stiffness and damping parameters. Ten young (24 ± 3 y) and seven older (75 ± 5 y) adults were exposed during eyes-closed stance to perturbations consisting of lateral pseudorandom floor tilts. A least-squares fit of the measured body sway data to the postural control model found significantly larger active stiffness and damping model parameters in the older adults. These differences remained significant even after normalizing to account for different body sizes between the young and older adult groups. An age effect was also found for the normalized passive stiffness, but not for the normalized passive damping parameter. This concurrent increase in active stiffness and damping was shown to be more stabilizing than an increase in stiffness alone, as assessed by oscillations in the postural control model impulse response. PMID:19770083

The effect of abdominal drawing-in exercise and myofascial release on pain, flexibility, and balance of elderly females.

PubMed

Yu, Seong Hun; Sim, Yong Hyeon; Kim, Myung Hoon; Bang, Ju Hee; Son, Kyung Hyun; Kim, Jae Woong; Kim, Hyun Jin

2016-10-01

[Purpose] This study is designed to compare the effects of abdominal drawing-in exercise and myofascial release on pain, flexibility, and balance of elderly females. [Subjects and Methods] Forty elderly females aged 65 or older who had complained of low back pain for three months or longer were selected as the subjects. They were randomly and equally assigned to either an abdominal drawing-in group or a myofascial release group. The subjects conducted exercise three times per week, 40 minutes each time, for eight weeks. As evaluation tools, visual analogue scale for pain, remodified schober test for flexibility, and upright posture with eye opening on hard platform, upright posture with eye closing on hard platform, upright posture with eye opening on soft platform, upright posture with eye closing on soft platform using tetrax for balance were used. [Results] The abdominal drawing-in exercise group saw significant difference in pain and balance after the exercise compared to before the exercise. The myofascial release group saw significant difference in pain and flexibility after exercise compared to before the exercise. [Conclusion] The above study showed that abdominal drawing-in exercise affected elderly females regarding pain and balance and myofascial release influenced their pain and flexibility.

Perception-Action and Adaptation in Postural Control of Children and Adolescents with Cerebral Palsy

ERIC Educational Resources Information Center

Barela, Jose A.; Focks, Grietje M. Jaspers; Hilgeholt, Toke; Barela, Ana M. F.; Carvalho, Raquel de P.; Savelsbergh, Geert J. P.

2011-01-01

The aim of this study was to examine the coupling between visual information and body sway and the adaptation in this coupling of individuals with cerebral palsy (CP). Fifteen children with and 15 without CP, 6-15 years old, were required to stand upright inside of a moving room. All children first performed two trials with no movement of the room…

Fetal malnutrition--the price of upright posture?

PubMed Central

Briend, A

1979-01-01

The pattern of preterm fetal growth faltering, normally seen in man, differs from that observed in animals. This type of fetal growth cannot be considered as an adaptation to facilitate birth but is more likely to be due to rapid evolution and imperfect adaptation to the upright posture. The pattern of posture and physical activity during pregnancy may therefore be an important determinant of fetal growth. Differences in intrauterine nutrition existing between social groups, usually ascribed to variations of maternal diet and nutrition, may well result from different patterns of maternal activity in the weeks preceding birth. PMID:476446

Effect of body posture on chewing behaviours in healthy volunteers.

PubMed

Iizumi, T; Magara, J; Tsujimura, T; Inoue, M

2017-11-01

Mastication is essential to the eating process and forms an important part of feeding behaviour. Many factors related to the food bolus, such as bolus texture and size, are known to influence mastication. The aim of this study was to determine the effects of body posture on (i) chewing duration prior to the first swallow and (ii) patterns of mastication-related EMG activity. We asked 10 healthy adults to chew 8 g of steamed rice with barium sulphate while we recorded masseter, suprahyoid and infrahyoid muscle activity and simultaneously collected videofluorographic images. Participants chewed in either an upright or reclining position. Chewing duration, which was defined as the time from the start of mastication to the first swallow, was not different between the positions. However, the variability of chewing duration was larger in the upright versus reclining position, and the chewing duration in the reclining position was distributed around 15 s. Masseter activity gradually decreased in a time-dependent manner and was significantly larger at the early versus late stage of mastication. Suprahyoid activity was significantly larger at the early versus middle stage of mastication in the upright position only. Finally, masseter activity per second was negatively correlated with changes in chewing duration, that is, the larger the increase in chewing duration in the reclining position, the more the decrease in masseter activity per second. These results suggest that position-dependent changes in chewing behaviours, as described by chewing duration and EMG activity, may vary among participants. © 2017 John Wiley & Sons Ltd.

Effects of posture on shear rates in human brachial and superficial femoral arteries

PubMed Central

Newcomer, S. C.; Sauder, C. L.; Kuipers, N. T.; Laughlin, M. H.; Ray, C. A.

2012-01-01

Shear rate is significantly lower in the superficial femoral compared with the brachial artery in the supine posture. The relative shear rates in these arteries of subjects in the upright posture (seated and/or standing) are unknown. The purpose of this investigation was to test the hypothesis that upright posture (seated and/or standing) would produce greater shear rates in the superficial femoral compared with the brachial artery. To test this hypothesis, Doppler ultrasound was used to measure mean blood velocity (MBV) and diameter in the brachial and superficial femoral arteries of 21 healthy subjects after being in the supine, seated, and standing postures for 10 min. MBV was significantly higher in the brachial compared with the superficial femoral artery during upright postures. Superficial femoral artery diameter was significantly larger than brachial artery diameter. However, posture had no significant effect on either brachial or superficial femoral artery diameter. The calculated shear rate was significantly greater in the brachial (73 ± 5, 91 ± 11, and 97 ± 13 s−1) compared with the superficial femoral (53 ± 4, 39 ± 77, and 44 ± 5 s−1) artery in the supine, seated, and standing postures, respectively. Contrary to our hypothesis, our current findings indicate that mean shear rate is lower in the superficial femoral compared with the brachial artery in the supine, seated, and standing postures. These findings of lower shear rates in the superficial femoral artery may be one mechanism for the higher propensity for atherosclerosis in the arteries of the leg than of the arm. PMID:18245564

Anal sphincter lacerations and upright delivery postures--a risk analysis from a randomized controlled trial.

PubMed

Altman, Daniel; Ragnar, Inga; Ekström, Asa; Tydén, Tanja; Olsson, Sven-Eric

2007-02-01

To evaluate obstetric sphincter lacerations after a kneeling or sitting position at second stage of labor in a multivariate risk analysis model. Two hundred and seventy-one primiparous women with normal pregnancies and spontaneous labor were randomized, 138 to a kneeling position and 133 to a sitting position. Medical data were retrieved from delivery charts and partograms. Risk factors were tested in a multivariate logistic regression model in a stepwise manner. The trial was completed by 106 subjects in the kneeling group and 112 subjects in the sitting group. There were no significant differences with regard to duration of second stage of labor or pre-trial maternal characteristics between the two groups. Obstetrical sphincter tears did not differ significantly between the two groups but an intact perineum was more common in the kneeling group (p<0.03) and episiotomy (mediolateral) was more common in the sitting group (p<0.05). Three grade IV sphincter lacerations occurred in the sitting group compared to none in the kneeling group (NS). Multivariate risk analysis indicated that prolonged duration of second stage of labor and episiotomy were associated with an increased risk of third- or fourth-degree sphincter tears (p<0.01 and p<0.05, respectively). Delivery posture, maternal age, fetal weight, use of oxytocin, and use of epidural analgesia did not increase the risk of obstetrical anal sphincter lacerations in the two upright postures. Obstetrical anal sphincter lacerations did not differ significantly between a kneeling or sitting upright delivery posture. Episiotomy was more common after a sitting delivery posture, which may be associated with an increased risk of anal sphincter lacerations. Upright delivery postures may be encouraged in healthy women with normal, full-term pregnancy.

Leaning to the left makes the Eiffel Tower seem smaller: posture-modulated estimation.

PubMed

Eerland, Anita; Guadalupe, Tulio M; Zwaan, Rolf A

2011-12-01

In two experiments, we investigated whether body posture influences people's estimation of quantities. According to the mental-number-line theory, people mentally represent numbers along a line with smaller numbers on the left and larger numbers on the right. We hypothesized that surreptitiously making people lean to the right or to the left would affect their quantitative estimates. Participants answered estimation questions while standing on a Wii Balance Board. Posture was manipulated within subjects so that participants answered some questions while they leaned slightly to the left, some questions while they leaned slightly to the right, and some questions while they stood upright. Crucially, participants were not aware of this manipulation. Estimates were significantly smaller when participants leaned to the left than when they leaned to the right.

Comparison of Human and Humanoid Robot Control of Upright Stance

PubMed Central

Peterka, Robert J.

2009-01-01

There is considerable recent interest in developing humanoid robots. An important substrate for many motor actions in both humans and biped robots is the ability to maintain a statically or dynamically stable posture. Given the success of the human design, one would expect there are lessons to be learned in formulating a postural control mechanism for robots. In this study we limit ourselves to considering the problem of maintaining upright stance. Human stance control is compared to a suggested method for robot stance control called zero moment point (ZMP) compensation. Results from experimental and modeling studies suggest there are two important subsystems that account for the low- and mid-frequency (DC to ~1 Hz) dynamic characteristics of human stance control. These subsystems are 1) a “sensory integration” mechanism whereby orientation information from multiple sensory systems encoding body kinematics (i.e. position, velocity) is flexibly combined to provide an overall estimate of body orientation while allowing adjustments (sensory re-weighting) that compensate for changing environmental conditions, and 2) an “effort control” mechanism that uses kinetic-related (i.e., force-related) sensory information to reduce the mean deviation of body orientation from upright. Functionally, ZMP compensation is directly analogous to how humans appear to use kinetic feedback to modify the main sensory integration feedback loop controlling body orientation. However, a flexible sensory integration mechanism is missing from robot control leaving the robot vulnerable to instability in conditions were humans are able to maintain stance. We suggest the addition of a simple form of sensory integration to improve robot stance control. We also investigate how the biological constraint of feedback time delay influences the human stance control design. The human system may serve as a guide for improved robot control, but should not be directly copied because the constraints on robot and human control are different. PMID:19665564

Comparison of human and humanoid robot control of upright stance.

PubMed

Peterka, Robert J

2009-01-01

There is considerable recent interest in developing humanoid robots. An important substrate for many motor actions in both humans and biped robots is the ability to maintain a statically or dynamically stable posture. Given the success of the human design, one would expect there are lessons to be learned in formulating a postural control mechanism for robots. In this study we limit ourselves to considering the problem of maintaining upright stance. Human stance control is compared to a suggested method for robot stance control called zero moment point (ZMP) compensation. Results from experimental and modeling studies suggest there are two important subsystems that account for the low- and mid-frequency (DC to approximately 1Hz) dynamic characteristics of human stance control. These subsystems are (1) a "sensory integration" mechanism whereby orientation information from multiple sensory systems encoding body kinematics (i.e. position, velocity) is flexibly combined to provide an overall estimate of body orientation while allowing adjustments (sensory re-weighting) that compensate for changing environmental conditions and (2) an "effort control" mechanism that uses kinetic-related (i.e., force-related) sensory information to reduce the mean deviation of body orientation from upright. Functionally, ZMP compensation is directly analogous to how humans appear to use kinetic feedback to modify the main sensory integration feedback loop controlling body orientation. However, a flexible sensory integration mechanism is missing from robot control leaving the robot vulnerable to instability in conditions where humans are able to maintain stance. We suggest the addition of a simple form of sensory integration to improve robot stance control. We also investigate how the biological constraint of feedback time delay influences the human stance control design. The human system may serve as a guide for improved robot control, but should not be directly copied because the constraints on robot and human control are different.

Exercise against lower body negative pressure as a countermeasure for cardiovascular and musculoskeletal deconditioning

NASA Astrophysics Data System (ADS)

Murthy, G.; Watenpaugh, D. E.; Ballard, R. E.; Hargens, A. R.

Exposure to lower body negative pressure (LBNP) with oral salt and water ingestion has been tested by astronauts as a countermeasure to prevent postflight orthostatic intolerance. Exercise is another countermeasure that astronauts commonly use during spaceflight to maintain musculoskeletal strength. We hypothesize that a novel combination of exercise and simultaneous exposure to lower body negative pressure during spaceflight will produce Earth-like musculoskeletal loads as well as cardiovascular stimuli to maintain adaptation to Earth's gravity. Results from recent studies indicate that leg exercise within a LBNP chamber against the suction force of 100 mmHg LBNP in horizontal-supine posture produces an equivalent, if not greater exercise stress compared to similar leg exercise in upright posture (without LBNP) against Earth's gravity. 12 Therefore, the concept of LBNP combined with exercise may prove to be a low cost and low mass technique to stress the cardiovascular and the musculoskeletal systems simultaneously.

Posture systematically alters ear-canal reflectance and DPOAE properties

PubMed Central

Voss, Susan E.; Adegoke, Modupe F.; Horton, Nicholas J.; Sheth, Kevin N.; Rosand, Jonathan; Shera, Christopher A.

2010-01-01

Several studies have demonstrated that the auditory system is sensitive to changes in posture, presumably through changes in intracranial pressure (ICP) that in turn alter the intracochlear pressure, which affects the stiffness of the middle-ear system. This observation has led to efforts to develop an ear-canal based noninvasive diagnostic measure for monitoring ICP, which is currently monitored invasively via access through the skull or spine. Here, we demonstrate the effects of postural changes, and presumably ICP changes, on distortion product otoacoustic emissions (DPOAE) magnitude, DPOAE angle, and power reflectance. Measurements were made on 12 normal-hearing subjects in two postural positions: upright at 90 degrees and tilted at −45 degrees to the horizontal. Measurements on each subject were repeated five times across five separate measurement sessions. All three measures showed significant changes (p < 0.001) between upright and tilted for frequencies between 500 and 2000 Hz, and DPOAE angle changes were significant at all measured frequencies (500–4000 Hz). Intrasubject variability, assessed via standard deviations for each subject’s multiple measurements, were generally smaller in the upright position relative to the tilted position. PMID:20227475

Slow changing postural cues cancel visual field dependence on self-tilt detection.

PubMed

Scotto Di Cesare, C; Macaluso, T; Mestre, D R; Bringoux, L

2015-01-01

Interindividual differences influence the multisensory integration process involved in spatial perception. Here, we assessed the effect of visual field dependence on self-tilt detection relative to upright, as a function of static vs. slow changing visual or postural cues. To that aim, we manipulated slow rotations (i.e., 0.05° s(-1)) of the body and/or the visual scene in pitch. Participants had to indicate whether they felt being tilted forward at successive angles. Results show that thresholds for self-tilt detection substantially differed between visual field dependent/independent subjects, when only the visual scene was rotated. This difference was no longer present when the body was actually rotated, whatever the visual scene condition (i.e., absent, static or rotated relative to the observer). These results suggest that the cancellation of visual field dependence by dynamic postural cues may rely on a multisensory reweighting process, where slow changing vestibular/somatosensory inputs may prevail over visual inputs. Copyright © 2014 Elsevier B.V. All rights reserved.

A Comparison of the Physiology and Mechanics of Exercise in LBNP and Upright Gait

NASA Technical Reports Server (NTRS)

Boda, W. L.; Watenpaugh, D. E.; Ballard, R. E.; Chang, D.; Looft-Wilson, R.; Hargens, A. R.

1996-01-01

Bone, muscular strength, aerobic capacity, and normal fluid pressure gradients within the body are lost during bed rest and spaceflight. Lower Body Negative Pressure (LBNP) exercise may create musculoskeletal and cardiovascular strains equal to a greater than those experienced on Earth and elucidate some of the mechanisms for maintaining bone integrity. LBNP exercise simulates gravity during supine posture by using negative pressure to pull subjects inward against a treadmill generating footward forces and increasing transmural pressures. Footward forces are generated which equal the product of the pressure differential and the cross-sectional area of the LBNP waist seal. Subjects lie supine within the chamber with their legs suspended from one another via cuffs, bungee cords, and pulleys, such that each leg acts as a counterweight to the other leg during the gait cycle. The subjects then walk or run on a treadmill which is positioned vertically within the chamber. Supine orientation allows only footward force production due to the negative pressure within the chamber. The purpose of this study was to determine if the kinematics, kinetics, and metabolic rate during supine walking and slow running on a vertical treadmill within LBNP are similar to those on a treadmill in 1-g environment in an upright posture.

MRI measurements of intracranial pressure in the upright posture: The effect of the hydrostatic pressure gradient.

PubMed

Alperin, Noam; Lee, Sang H; Bagci, Ahmet M

2015-10-01

To add the hydrostatic component of the cerebrospinal fluid (CSF) pressure to magnetic resonance imaging (MRI)-derived intracranial pressure (ICP) measurements in the upright posture for derivation of pressure value in a central cranial location often used in invasive ICP measurements. Additional analyses were performed using data previously collected from 10 healthy subjects scanned in supine and sitting positions with a 0.5T vertical gap MRI scanner (GE Medical). Pulsatile blood and CSF flows to and from the brain were quantified using cine phase-contrast. Intracranial compliance and pressure were calculated using a previously described method. The vertical distance between the location of the CSF flow measurement and a central cranial location was measured manually in the mid-sagittal T1 -weighted image obtained in the upright posture. The hydrostatic pressure gradient of a CSF column with similar height was then added to the MR-ICP value. After adjustment for the hydrostatic component, the mean ICP value was reduced by 7.6 mmHg. Mean ICP referenced to the central cranial level was -3.4 ± 1.7 mmHg compared to the unadjusted value of +4.3 ± 1.8 mmHg. In the upright posture, the hydrostatic pressure component needs to be added to the MRI-derived ICP values for compatibility with invasive ICP at a central cranial location. © 2015 Wiley Periodicals, Inc.

The Gravity of LBNP Exercise: Lessons Learned from Identical Twins in Bed for 30 Days

NASA Technical Reports Server (NTRS)

Hargens, Alan R.; Groppo, Eli R.; Lee, Stuart M. C.; Watenpaugh, Donald; Schneider, Suzanne; O'Leary, Deborah; Smith, Scott M.; Steinbach, Gregory C.; Tanaka, Kunihiko; Kimura, Shinji;

Cervical vertebral realignment when voluntarily adopting a protective neck posture.

PubMed

Newell, Robyn S; Siegmund, Gunter P; Blouin, Jean-Sébastien; Street, John; Cripton, Peter A

2014-07-01

In vivo human volunteer study of the intervertebral postural changes and muscle activity levels while tensing the neck muscles. To determine if actively tensing the neck muscles changes the posture of the cervical spine and, because axial impact neck injury often occurs while inverted, whether these changes exist both upright and upside down. Rollover accidents are dynamic and complex events in which head contacts with the vehicle interior can cause catastrophic neck injuries. Computational modeling has suggested that active neck muscles may increase the risk of cervical spine fracture in a rollover crash. Cadaver testing has also demonstrated that overall neck alignment and curvature are key to understanding and preventing catastrophic neck injuries. Although muscle activity and neck posture affects the resulting injury, there are currently no in vivo data describing how tensing the neck muscles influences intervertebral posture. Eleven human subjects (6 females, 5 males) actively tensed their neck muscles while seated upright and inverted. Vertebral alignment was measured using fluoroscopy and muscle activity was recorded using surface and indwelling electrodes in 8 neck muscles. On average, tensed muscles increased cervical spine curvature and anterior motion of the cervical vertebrae relative to the torso. These changes, which were magnified by inversion, indicate that cervical intervertebral posture differs considerably between the relaxed and tensed states. Active muscle contraction can change the vertebral alignment in upright and inverted postures. This change in posture may alter the load path and injury mechanics during an axial head impact and may help explain the disparity between the neck injuries observed in real-world rollover accidents and ex vivo cadaver experiments. N/A.

Symmetry in running.

PubMed

Raibert, M H

1986-03-14

Symmetry plays a key role in simplifying the control of legged robots and in giving them the ability to run and balance. The symmetries studied describe motion of the body and legs in terms of even and odd functions of time. A legged system running with these symmetries travels with a fixed forward speed and a stable upright posture. The symmetries used for controlling legged robots may help in elucidating the legged behavior of animals. Measurements of running in the cat and human show that the feet and body sometimes move as predicted by the even and odd symmetry functions.

Neuropathological aspects of conservative treatment of scoliosis. A theoretical view point.

PubMed

Czupryna, Krzysztof; Nowotny-Czupryna, Olga; Nowotny, Janusz

2012-01-01

An upright body posture cannot be maintained passively for reasons including a high location of the centre of gravity (COG) and a small support area. Proper alignment of body parts is maintained automatically, tending towards a pattern encoded in the CNS. A particularly important role in posture regulation is played by the short muscles of the back, which respond to being stretched with a contraction. During the early phase of scoliosis, the CNS automatically corrects abnormalities, but over time habituation occurs and the CNS treats them as something normal. Any attempt to restore proper body alignment is treated as an error and CNS automatically restores this abnormal pattern. With a prolonged deviation in body part alignment, CNS treats it as a defect and runs compensatory mechanisms to restore the balance of the body as a whole. Balance is ensured by postural compensation, but this does not restore proper body part alignment. In the treatment of scoliosis, it is important both to slow down progression and to prevent the development of abnormal postural habits, which are part of a vicious circle even without progression. Secondary prevention is therefore needed in all patients. Passive observation limits the possibilities for prevention and contradicts the principle of early implementation of rehabilitation. Depending on the size of the angle of curvature, recommended treatments of scoliosis comprise observation, corset bracing, and surgery. Physiotherapy is often treated as an unconventional and ineffective treatment. Often, the biggest problem is transferring the resulting correction to automatic maintenance of a correct posture in the vertical position. The aim of this paper was to discuss the conservative treatment of scoliosis with regard to difficulties maintaining the correct alignment of the body parts in the vertical position that accompany scoliosis.

The variability of the force produced by the plantar flexor muscles does not associate with postural sway in older adults during upright standing.

PubMed

Barbosa, Roberto N; Silva, Nilson R S; Santos, Daniel P R; Moraes, Renato; Gomes, Matheus M

2018-05-31

The force variability of the plantar flexor muscles (PFM) appears to be directly related to the control of upright standing. Nevertheless, this association is still uncertain in older adults. This study aimed to evaluate the relationship between PFM force variability and postural sway in the upright standing in older women. Forty older women performed submaximal plantar flexion movements measured by force transducers coupled to an experimental chair. They performed this task during three sets of 20 s at 5% and 10% of their maximum voluntary isometric contraction with and without the aid of visual feedback of the force produced. The volunteers then stood barefoot, with eyes closed and feet parallel on a force platform, which allowed the measurement of the center of pressure displacement in the anteroposterior direction. The results did not indicate a significant association between force variability of the PFMs and postural sway in older women. It can be inferred that the force variability of the PFM does not play an important role in controlling the posture in this population, suggesting that other factors may influence the functioning of the postural control system in older adults. Copyright © 2018. Published by Elsevier B.V.

Postural Stability When Leaning from Perceived Upright

NASA Technical Reports Server (NTRS)

Vanya, Robert D.; Grounds, John F.; Wood, Scott J.

2011-01-01

The transition between quiet stance and gait requires the volitional movement of one?s center of mass (COM) toward a limit of stability (LOS). The goal of this study was to measure the effect of leaning from perceived upright on postural stability when voluntarily maintaining fixed stance positions and during perturbations of the support surface. The COM was derived from force plate data in 12 healthy subjects while standing with feet positioned so that lateral base of support was equal to foot length. For all conditions, arms were folded and subjects were instructed to lean without bending at the hips or lifting their feet. The LOS was determined during maximal voluntary leans with eyes open and closed. The COM was then displayed on a monitor located in front of the subject. Subjects were visually guided to lean toward a target position, maintain this position for 10s, return to upright, and then repeat the same targeted lean maneuver with eyes closed. Targets were randomly presented at 2? in 8 directions and between 2-6? in these same directions according to the asymmetric LOS. Subjects were then verbally guided to lean between 2? back and 4? forward prior to a perturbation of the support surface in either a forward or backward direction. The average LOS was 5.8? forward, 2.9? back, and 4.8? in left/right directions, with no significant difference between eyes open and closed. Center of pressure (COP) velocity increased as subjects maintained fixed stance positions farther from upright, with increased variability during eyes closed conditions. The time to stability and COP path length increased as subjects leaned opposite to the direction of the support surface perturbations. We conclude that postural stability is compromised as subjects lean away from perceived upright, except for perturbations that induce sway in the direction opposite the lean. The asymmetric LOS relative to perceived upright favors postural stability for COM movements in the forward direction.

Influence of obesity on accurate and rapid arm movement performed from a standing posture.

PubMed

Berrigan, F; Simoneau, M; Tremblay, A; Hue, O; Teasdale, N

2006-12-01

Obesity yields a decreased postural stability. The potentially negative impact of obesity on the control of upper limb movements, however, has not been documented. This study sought to examine if obesity imposes an additional balance control constraint limiting the speed and accuracy with which an upper limb goal-directed movement performed from an upright standing position can be executed. Eight healthy lean subjects (body mass index (BMI) between 20.9 and 25.0 kg/m(2)) and nine healthy obese subjects (BMI between 30.5 and 48.6 kg/m(2)) pointed to a target located in front of them from an upright standing posture. The task was to aim at the target as fast and as precisely as possible after an auditory signal. The difficulty of the task was varied by using different target sizes (0.5, 1.0, 2.5 and 5.0 cm width). Hand movement time (MT) and velocity profiles were measured to quantify the aiming. Centre of pressure and segmental kinematics were analysed to document postural stability. When aiming, the forward centre of pressure (CP) displacement was greater for the obese group than for the normal BMI group (4.6 and 1.9 cm, respectively). For the obese group, a decrease in the target size was associated with an increase in backward CP displacement and CP peak speed whereas for the normal BMI group backward CP displacements and CP peak speed were about the same across all target sizes. Obese participants aimed at the target moving their whole body forward whereas the normal BMI subjects predominantly made an elbow extension and shoulder flexion. For both groups, MT increased with a decreasing target size. Compare to the normal BMI group, this effect was exacerbated for the obese group. For the two smallest targets, movements were on average 115 and 145 ms slower for the obese than for the normal BMI group suggesting that obesity added a balance constraint and limited the speed with which an accurate movement could be done. Obesity, because of its effects on the control of balance, also imposes constraints on goal-directed movements. From a clinical perspective, obese individuals might be less efficient and more at risk of injuries than normal weight individuals in a large number of work tasks and daily activities requiring upper limb movements performed from an upright standing position.

Effects of body lean and visual information on the equilibrium maintenance during stance.

PubMed

Duarte, Marcos; Zatsiorsky, Vladimir M

2002-09-01

Maintenance of equilibrium was tested in conditions when humans assume different leaning postures during upright standing. Subjects ( n=11) stood in 13 different body postures specified by visual center of pressure (COP) targets within their base of support (BOS). Different types of visual information were tested: continuous presentation of visual target, no vision after target presentation, and with simultaneous visual feedback of the COP. The following variables were used to describe the equilibrium maintenance: the mean of the COP position, the area of the ellipse covering the COP sway, and the resultant median frequency of the power spectral density of the COP displacement. The variability of the COP displacement, quantified by the COP area variable, increased when subjects occupied leaning postures, irrespective of the kind of visual information provided. This variability also increased when vision was removed in relation to when vision was present. Without vision, drifts in the COP data were observed which were larger for COP targets farther away from the neutral position. When COP feedback was given in addition to the visual target, the postural control system did not control stance better than in the condition with only visual information. These results indicate that the visual information is used by the postural control system at both short and long time scales.

Normative 3D opto-electronic stereo-photogrammetric posture and spine morphology data in young healthy adult population

PubMed Central

2017-01-01

Design: Observational cross-sectional study. The current study aims to yield normative data: i.e., the physiological standard for 30 selected quantitative 3D parameters that accurately capture and describe a full-skeleton, upright-standing attitude. Specific and exclusive consideration was given to three distinct categories: postural, spine morphology and pelvic parameters. To capture such 3D parameters, the authors selected a non-ionising 3D opto-electronic stereo-photogrammetric approach. This required the identification and measurement of 27 body landmarks, each specifically tagged with a skin marker. As subjects for the measurement of these parameters, a cohort of 124 asymptomatic young adult volunteers was recruited. All parameters were identified and measured within this group. Postural and spine morphology data have been compared between genders. In this regard, only five statistically significant differences were found: pelvis width, pelvis torsion, the “lumbar” lordosis angle value, the lumbar curve length, and the T12-L5 anatomically-bound lumbar angle value. The “thoracic” kyphosis mean angle value was the same in both sexes and, even if, derived from skin markers placed on spinous processes it resulted in perfect agreement with the X-ray based literature. As regards lordosis, a direct comparison was more difficult because methods proposed in the literature differ as to the number and position of vertebrae under consideration, and their related angle values. However, when the L1 superior–L5 inferior end plate Cobb angle was considered, these results aligned strongly with the existing literature. Asymmetry was a standard postural-spinal feature for both sexes. Each subject presented some degree of leg length discrepancy (LLD) with μ = 9.37mm. This was associated with four factors: unbalanced posture and/or underfoot loads, spinal curvature in the frontal plane, and pelvis torsion. This led to the additional study of the effect of LLD equalisation influence on upright posture, relying on a sub-sample of 100 subjects (51 males, 49 females). As a result of the equalisation, about 82% of this sub-sample showed improvement in standing posture, mainly in the frontal plane; while in the sagittal plane less than 1/3 of the sub-sample showed evidence of change in spinal angles. A significant variation was found in relation to pelvis torsion: 46% of subjects showed improvement, 49% worsening. The method described in study presents several advantages: non-invasive aspect; relatively short time for a complete postural evaluation with many clinically useful 3D and 2D anatomical/biomechanical/clinical parameters; analysis of real neutral unconstrained upright standing posture. PMID:28640899

Spinal lordosis optimizes the requirements for a stable erect posture.

PubMed

Wagner, Heiko; Liebetrau, Anne; Schinowski, David; Wulf, Thomas; de Lussanet, Marc H E

2012-04-16

Lordosis is the bending of the lumbar spine that gives the vertebral column of humans its characteristic ventrally convex curvature. Infants develop lordosis around the time when they acquire bipedal locomotion. Even macaques develop a lordosis when they are trained to walk bipedally. The aim of this study was to investigate why humans and some animals develop a lumbar lordosis while learning to walk bipedally. We developed a musculoskeletal model of the lumbar spine, that includes an asymmetric, dorsally shifted location of the spinal column in the body, realistic moment arms, and physiological cross-sectional areas (PCSA) of the muscles as well as realistic force-length and force-velocity relationships. The model was used to analyze the stability of an upright body posture. According to our results, lordosis reduces the local joint torques necessary for an equilibrium of the vertebral column during an erect posture. At the same time lordosis increases the demands on the global muscles to provide stability. We conclude that the development of a spinal lordosis is a compromise between the stability requirements of an erect posture and the necessity of torque equilibria at each spinal segment.

Spinal lordosis optimizes the requirements for a stable erect posture

PubMed Central

2012-01-01

Background Lordosis is the bending of the lumbar spine that gives the vertebral column of humans its characteristic ventrally convex curvature. Infants develop lordosis around the time when they acquire bipedal locomotion. Even macaques develop a lordosis when they are trained to walk bipedally. The aim of this study was to investigate why humans and some animals develop a lumbar lordosis while learning to walk bipedally. Results We developed a musculoskeletal model of the lumbar spine, that includes an asymmetric, dorsally shifted location of the spinal column in the body, realistic moment arms, and physiological cross-sectional areas (PCSA) of the muscles as well as realistic force-length and force-velocity relationships. The model was used to analyze the stability of an upright body posture. According to our results, lordosis reduces the local joint torques necessary for an equilibrium of the vertebral column during an erect posture. At the same time lordosis increases the demands on the global muscles to provide stability. Conclusions We conclude that the development of a spinal lordosis is a compromise between the stability requirements of an erect posture and the necessity of torque equilibria at each spinal segment. PMID:22507595

Resisted side-stepping: the effect of posture on hip abductor muscle activation

PubMed Central

Berry, Justin W.; Lee, Theresa S.; Foley, Hanna D.; Lewis, Cara L.

2016-01-01

Study Design Controlled laboratory study, repeated-measures design. Objectives To compare hip abductor muscle activity and hip and knee joint kinematics in the moving limb to the stance limb during resisted side-stepping and also to determine if muscle activity was affected by the posture (upright standing versus squat) used to perform the exercise. Background Hip abductor weakness has been associated with a variety of lower extremity injuries. Resisted side-stepping is often used as an exercise to increase strength and endurance of the hip abductors. Exercise prescription would benefit from knowing the relative muscle activity level generated in each limb and for different postures during the side-stepping exercise. Methods Twenty-four healthy adults participated in this study. Kinematics and surface electromyographic (EMG) data from the gluteus maximus, gluteus medius, and tensor fascia lata (TFL) were collected as participants performed side-stepping with a resistive band around the ankle while maintaining each of 2 postures: 1) upright standing and 2) squat. Results Mean normalized EMG signal amplitude of the gluteus maximus, gluteus medius, and TFL was higher in the stance limb than the moving limb (P≤.001). Gluteal muscle activity was higher, while TFL muscle activity was lower, in the squat posture compared to the upright standing posture (P<.001). Hip abduction excursion was greater in the stance limb than in the moving limb (P<.001). Conclusions The 3 hip abductor muscles respond differently to the posture variations of side-stepping exercise in healthy individuals. When prescribing resisted side-stepping exercises, therapists should consider the differences in hip abductor activation across limbs and variations in trunk posture. PMID:26161629

Destabilization of Human Balance Control by Static and Dynamic Head Tilts

NASA Technical Reports Server (NTRS)

Paloski, William H.; Wood, Scott J.; Feiveson, Alan H.; Black, F. Owen; Hwang, Emma Y.; Reschke, Millard F.

2004-01-01

To better understand the effects of varying head movement frequencies on human balance control, 12 healthy adult humans were studied during static and dynamic (0.14,0.33,0.6 Hz) head tilts of +/-30deg in the pitch and roll planes. Postural sway was measured during upright stance with eyes closed and altered somatosensory inputs provided by a computerized dynamic posturography (CDP) system. Subjects were able to maintain upright stance with static head tilts, although postural sway was increased during neck extension. Postural stability was decreased during dynamic head tilts, and the degree of destabilization varied directly with increasing frequency of head tilt. In the absence of vision and accurate foot support surface inputs, postural stability may be compromised during dynamic head tilts due to a decreased ability of the vestibular system to discern the orientation of gravity.

Lumbar spine disc height and curvature responses to an axial load generated by a compression device compatible with magnetic resonance imaging

NASA Technical Reports Server (NTRS)

Kimura, S.; Steinbach, G. C.; Watenpaugh, D. E.; Hargens, A. R.

2001-01-01

STUDY DESIGN: Axial load-dependent changes in the lumbar spine of supine healthy volunteers were examined using a compression device compatible with magnetic resonance imaging. OBJECTIVE: To test two hypotheses: Axial loading of 50% body weight from shoulder to feet in supine posture 1) simulates the upright lumbar spine alignment and 2) decreases disc height significantly. SUMMARY OF BACKGROUND DATA: Axial compression on the lumbar spine has significantly narrowed the lumbar dural sac in patients with sciatica, neurogenic claudication or both. METHODS: Using a device compatible with magnetic resonance imaging, the lumbar spine of eight young volunteers, ages 22 to 36 years, was axially compressed with a force equivalent to 50% of body weight, approximating the normal load on the lumbar spine in upright posture. Sagittal lumbar magnetic resonance imaging was performed to measure intervertebral angle and disc height before and during compression. RESULTS: Each intervertebral angle before and during compression was as follows: T12-L1 (-0.8 degrees +/- 2.5 degrees and -1.5 degrees +/- 2.6 degrees ), L1-L2 (0.7 degrees +/- 1.4 degrees and 3.3 degrees +/- 2.9 degrees ), L2-L3 (4.7 degrees +/- 3.5 degrees and 7.3 degrees +/- 6 degrees ), L3-L4 (7.9 degrees +/- 2.4 degrees and 11.1 degrees +/- 4.6 degrees ), L4-L5 (14.3 degrees +/- 3.3 degrees and 14.9 degrees +/- 1.7 degrees ), L5-S1 (25.8 degrees +/- 5.2 degrees and 20.8 degrees +/- 6 degrees ), and L1-S1 (53.4 degrees +/- 11.9 degrees and 57.3 degrees +/- 16.7 degrees ). Negative values reflect kyphosis, and positive values reflect lordosis. A significant difference between values before and during compression was obtained at L3-L4 and L5-S1. There was a significant decrease in disc height only at L4-L5 during compression. CONCLUSIONS: The axial force of 50% body weight in supine posture simulates the upright lumbar spine morphologically. No change in intervertebral angle occurred at L4-L5. However, disc height at L4-L5 decreased significantly during compression.

Physiological Mechanisms Mediating the Coupling between Heart Period and Arterial Pressure in Response to Postural Changes in Humans

PubMed Central

Silvani, Alessandro; Calandra-Buonaura, Giovanna; Johnson, Blair D.; van Helmond, Noud; Barletta, Giorgio; Cecere, Anna G.; Joyner, Michael J.; Cortelli, Pietro

2017-01-01

The upright posture strengthens the coupling between heart period (HP) and systolic arterial pressure (SAP) consistently with a greater contribution of the arterial baroreflex to cardiac control, while paradoxically decreasing cardiac baroreflex sensitivity (cBRS). To investigate the physiological mechanisms that mediate the coupling between HP and SAP in response to different postures, we analyzed the cross-correlation functions between low-frequency HP and SAP fluctuations and estimated cBRS with the sequence technique in healthy male subjects during passive head-up tilt test (HUTT, n = 58), during supine wakefulness, supine slow-wave sleep (SWS), and in the seated and active standing positions (n = 8), and during progressive loss of 1 L blood (n = 8) to decrease central venous pressure in the supine position. HUTT, SWS, the seated, and the standing positions, but not blood loss, entailed significant increases in the positive correlation between HP and the previous SAP values, which is the expected result of arterial baroreflex control, compared with baseline recordings in the supine position during wakefulness. These increases were mirrored by increases in the low-frequency variability of SAP in each condition but SWS. cBRS decreased significantly during HUTT, in the seated and standing positions, and after blood loss compared with baseline during wakefulness. These decreases were mirrored by decreases in the RMSSD index, which reflects cardiac vagal modulation. These results support the view that the cBRS decrease associated with the upright posture is a byproduct of decreased cardiac vagal modulation, triggered by the arterial baroreflex in response to central hypovolemia. Conversely, the greater baroreflex contribution to cardiac control associated with upright posture may be explained, at least in part, by enhanced fluctuations of SAP, which elicit a more effective entrainment of HP fluctuations by the arterial baroreflex. These SAP fluctuations may result from enhanced fluctuations of vascular resistance specific to the upright posture, and not be driven by the accompanying central hypovolemia. PMID:28396638

Physiological Mechanisms Mediating the Coupling between Heart Period and Arterial Pressure in Response to Postural Changes in Humans.

PubMed

Silvani, Alessandro; Calandra-Buonaura, Giovanna; Johnson, Blair D; van Helmond, Noud; Barletta, Giorgio; Cecere, Anna G; Joyner, Michael J; Cortelli, Pietro

2017-01-01

The upright posture strengthens the coupling between heart period (HP) and systolic arterial pressure (SAP) consistently with a greater contribution of the arterial baroreflex to cardiac control, while paradoxically decreasing cardiac baroreflex sensitivity (cBRS). To investigate the physiological mechanisms that mediate the coupling between HP and SAP in response to different postures, we analyzed the cross-correlation functions between low-frequency HP and SAP fluctuations and estimated cBRS with the sequence technique in healthy male subjects during passive head-up tilt test (HUTT, n = 58), during supine wakefulness, supine slow-wave sleep (SWS), and in the seated and active standing positions ( n = 8), and during progressive loss of 1 L blood ( n = 8) to decrease central venous pressure in the supine position. HUTT, SWS, the seated, and the standing positions, but not blood loss, entailed significant increases in the positive correlation between HP and the previous SAP values, which is the expected result of arterial baroreflex control, compared with baseline recordings in the supine position during wakefulness. These increases were mirrored by increases in the low-frequency variability of SAP in each condition but SWS. cBRS decreased significantly during HUTT, in the seated and standing positions, and after blood loss compared with baseline during wakefulness. These decreases were mirrored by decreases in the RMSSD index, which reflects cardiac vagal modulation. These results support the view that the cBRS decrease associated with the upright posture is a byproduct of decreased cardiac vagal modulation, triggered by the arterial baroreflex in response to central hypovolemia. Conversely, the greater baroreflex contribution to cardiac control associated with upright posture may be explained, at least in part, by enhanced fluctuations of SAP, which elicit a more effective entrainment of HP fluctuations by the arterial baroreflex. These SAP fluctuations may result from enhanced fluctuations of vascular resistance specific to the upright posture, and not be driven by the accompanying central hypovolemia.

Effect of age and posture on human lymphocyte adenylate cyclase activity.

PubMed

Mader, S L; Robbins, A S; Rubenstein, L Z; Tuck, M L; Scarpace, P J

1988-03-01

1. A number of age-related changes have been reported in the catecholamine-adrenoceptor-adenylate cyclase system. Most of the data available on these alterations come from resting subjects; the response to acute stress may provide additional insights into the age effect on these responses. 2. We measured supine and 10 min upright plasma noradrenaline and lymphocyte adenylate cyclase activity in ten healthy elderly subjects (age 66-80 years) and seven healthy young subjects (age 27-34 years). 3. Isoprenaline stimulation of lymphocyte adenylate cyclase activity was not significantly different between supine and upright positions or between elderly and young subjects. There was a marked increase in forskolin-stimulated adenylate cyclase activity in the upright posture in both elderly and young subjects. The increment over supine levels was 70% in the elderly (P less than 0.025) and 73% in the young (P less than 0.05). This enhanced forskolin activity was not seen in two young subjects who became syncopal. 4. These data suggest that enhanced forskolin-stimulated adenylate cyclase activity occurs after 10 min of upright posture in both elderly and young subjects, and may be relevant to immediate blood pressure regulation. We were unable to demonstrate any age-related differences in these acute adrenergic responses.

Holistic processing for bodies and body parts: New evidence from stereoscopic depth manipulations.

PubMed

Harris, Alison; Vyas, Daivik B; Reed, Catherine L

2016-10-01

Although holistic processing has been documented extensively for upright faces, it is unclear whether it occurs for other visual categories with more extensive substructure, such as body postures. Like faces, body postures have high social relevance, but they differ in having fine-grain organization not only of basic parts (e.g., arm) but also subparts (e.g., elbow, wrist, hand). To compare holistic processing for whole bodies and body parts, we employed a novel stereoscopic depth manipulation that creates either the percept of a whole body occluded by a set of bars, or of segments of a body floating in front of a background. Despite sharing low-level visual properties, only the stimulus perceived as being behind bars should be holistically "filled in" via amodal completion. In two experiments, we tested for better identification of individual body parts within the context of a body versus in isolation. Consistent with previous findings, recognition of body parts was better in the context of a whole body when the body was amodally completed behind occluders. However, when the same bodies were perceived as floating in strips, performance was significantly worse, and not significantly different, from that for amodally completed parts, supporting holistic processing of body postures. Intriguingly, performance was worst for parts in the frontal depth condition, suggesting that these effects may extend from gross body organization to a more local level. These results provide suggestive evidence that holistic representations may not be "all-or-none," but rather also operate on body regions of more limited spatial extent.

Periodically Relieving Ischial Sitting Load to Decrease the Risk of Pressure Ulcers

PubMed Central

Makhsous, Mohsen; Rowles, Diane M.; Rymer, William Z.; Bankard, James; Nam, Ellis K.; Chen, David; Lin, Fang

2010-01-01

Objective To investigate the relieving effect on interface pressure of an alternate sitting protocol involving a sitting posture that reduces ischial support. Design Repeated measures in 2 protocols on 3 groups of subjects. Setting Laboratory. Participants Twenty able-bodied persons, 20 persons with paraplegia, and 20 persons with tetraplegia. Interventions Two 1-hour protocols were used: alternate and normal plus pushup. In the alternate protocol, sitting posture was alternated every 10 minutes between normal (sitting upright with ischial support) and with partially removed ischial support (WO-BPS) postures; in the normal plus pushup protocol, sitting was in normal posture with pushups (lifting the subject off the seat) performed every 20 minutes. Main Outcome Measure Interface pressure on seat and backrest. Results In WO-BPS posture, the concentrated interface pressure observed around the ischia in normal posture was significantly repositioned to the thighs. By cyclically repositioning the interface pressure, the alternate protocol was superior to the normal plus pushup protocol in terms of a significantly lower average interface pressure over the buttocks. Conclusions A sitting protocol periodically reducing the ischial support helps lower the sitting load on the buttocks, especially the area close to ischial tuberosities. PMID:17601466

Preoperative Assessment of Neural Elements in Lumbar Spinal Stenosis by Upright Magnetic Resonance Imaging: An Implication for Routine Practice?

PubMed

Lang, Gernot; Vicari, Marco; Siller, Alexander; Kubosch, Eva J; Hennig, Juergen; Südkamp, Norbert P; Izadpanah, Kaywan; Kubosch, David

2018-04-06

Introduction Lumbar spinal stenosis (LSS) is a kinetic-dependent disease typically aggravating during spinal loading. To date, assessment of LSS is usually performed with magnetic resonance imaging (MRI). However, conventional supine MRI is associated with significant drawbacks as it does not truly reflect physiological loads, experienced by discoligamentous structures during erect posture. Consequently, supine MRI often fails to reveal the source of pain and/or disability caused by LSS. The present study sought to assess neural dimensions via MRI in supine, upright, and upright-hyperlordotic position in order to evaluate the impact of patient positioning on neural narrowing. Therefore, radiological measures such as neuroforaminal dimensions, central canal volume, sagittal listhesis, and lumbar lordosis at spinal level L4/5 were extracted and stratified according to patient posture. Materials and methods Overall, 10 subjects were enclosed in this experimental study. MRI was performed in three different positions: (1) 0° supine (SP), (2) 80° upright (UP), and (3) 80° upright + hyperlordotic (HY) posture. Upright MRI was conducted utilizing a 0.25T open-configuration scanner equipped with a rotatable examination bed allowing for true standing MRI. Radiographic outcome of upright MRI imaging was extracted and evaluated according to patient positioning. Results Upright MRI-based assessment of neural dimensions was successfully accomplished in all subjects. Overall, radiographic parameters revealed a significant decrease of neural dimensions from supine to upright position: Specifically, mean foraminal area decreased from SP to UP by 13.3% (P ≤ 0.05) as well as from SP to HY position by 21% (P ≤ 0.05). Supplementation of hyperlordosis did not result in additional narrowing of neural elements (P ≥ 0.05). Furthermore, central canal volume revealed a decrease of 7% at HY and 8% at UP compared to SP position (P ≥ 0.05). Assessment of lumbar lordosis yielded in a significant increase when assessed at HY (+22.1%) or UP (+8.7%) compared to SP (P ≤ 0.05). Conclusions Our data suggest that neuroforaminal dimensions assessed by conventional supine MRI are potentially overestimated in patients with LSS. Especially, in patients having occult disease not visualized on conventional imaging modalities, upright MRI allows for a precise, clinically relevant, and at the same time non-invasive evaluation of neural elements in LSS when neural decompression is considered.

Mechanical effort predicts the selection of ankle over hip strategies in nonstepping postural responses

PubMed Central

Jonkers, Ilse; De Schutter, Joris; De Groote, Friedl

2016-01-01

Experimental studies have shown that a continuum of ankle and hip strategies is used to restore posture following an external perturbation. Postural responses can be modeled by feedback control with feedback gains that optimize a specific objective. On the one hand, feedback gains that minimize effort have been used to predict muscle activity during perturbed standing. On the other hand, hip and ankle strategies have been predicted by minimizing postural instability and deviation from upright posture. It remains unclear, however, whether and how effort minimization influences the selection of a specific postural response. We hypothesize that the relative importance of minimizing mechanical work vs. postural instability influences the strategy used to restore upright posture. This hypothesis was investigated based on experiments and predictive simulations of the postural response following a backward support surface translation. Peak hip flexion angle was significantly correlated with three experimentally determined measures of effort, i.e., mechanical work, mean muscle activity and metabolic energy. Furthermore, a continuum of ankle and hip strategies was predicted in simulation when changing the relative importance of minimizing mechanical work and postural instability, with increased weighting of mechanical work resulting in an ankle strategy. In conclusion, the combination of experimental measurements and predictive simulations of the postural response to a backward support surface translation showed that the trade-off between effort and postural instability minimization can explain the selection of a specific postural response in the continuum of potential ankle and hip strategies. PMID:27489362

Evolution of seahorses' upright posture was linked to Oligocene expansion of seagrass habitats.

PubMed

Teske, Peter R; Beheregaray, Luciano B

2009-08-23

Seahorses (Syngnathidae: Hippocampus) are iconic marine teleosts that are readily identifiable by their upright posture. The fossil record is inadequate to shed light on the evolution of this trait because it lacks transitional forms. There are, however, extant syngnathid species (the pygmy pipehorses) that look like horizontally swimming seahorses and that might represent a surviving evolutionary link between the benthic seahorses and other, free-swimming members of the family Syngnathidae. Using sequence data from five nuclear loci, we confirm the sister taxon relationship between seahorses and pygmy pipehorses. Molecular dating indicates that the two taxa diverged during the Late Oligocene. During this time, tectonic events in the Indo-West Pacific resulted in the formation of vast amounts of new shallow-water areas and associated expansion of seagrass habitats that would have favoured the seahorses' upright posture by improving their camouflage while not affecting their manoeuvrability negatively. The molecular techniques employed here provide new insights into the evolution of a taxon whose fossil record is incomplete, but whose evolutionary history is so recent that the major stages of morphological evolution are still represented in extant species.

Decreasing Internal Focus of Attention Improves Postural Control during Quiet Standing in Young Healthy Adults

ERIC Educational Resources Information Center

Nafati, Gilel; Vuillerme, Nicolas

2011-01-01

This experiment was designed to investigate whether and how decreasing the amount of attentional focus invested in postural control could affect bipedal postural control. Twelve participants were asked to stand upright as immobile as possible on a force platform in one control condition and one cognitive condition. In the latter condition, they…

The Effect of Body Posture on Brain Glymphatic Transport.

PubMed

Lee, Hedok; Xie, Lulu; Yu, Mei; Kang, Hongyi; Feng, Tian; Deane, Rashid; Logan, Jean; Nedergaard, Maiken; Benveniste, Helene

2015-08-05

The glymphatic pathway expedites clearance of waste, including soluble amyloid β (Aβ) from the brain. Transport through this pathway is controlled by the brain's arousal level because, during sleep or anesthesia, the brain's interstitial space volume expands (compared with wakefulness), resulting in faster waste removal. Humans, as well as animals, exhibit different body postures during sleep, which may also affect waste removal. Therefore, not only the level of consciousness, but also body posture, might affect CSF-interstitial fluid (ISF) exchange efficiency. We used dynamic-contrast-enhanced MRI and kinetic modeling to quantify CSF-ISF exchange rates in anesthetized rodents' brains in supine, prone, or lateral positions. To validate the MRI data and to assess specifically the influence of body posture on clearance of Aβ, we used fluorescence microscopy and radioactive tracers, respectively. The analysis showed that glymphatic transport was most efficient in the lateral position compared with the supine or prone positions. In the prone position, in which the rat's head was in the most upright position (mimicking posture during the awake state), transport was characterized by "retention" of the tracer, slower clearance, and more CSF efflux along larger caliber cervical vessels. The optical imaging and radiotracer studies confirmed that glymphatic transport and Aβ clearance were superior in the lateral and supine positions. We propose that the most popular sleep posture (lateral) has evolved to optimize waste removal during sleep and that posture must be considered in diagnostic imaging procedures developed in the future to assess CSF-ISF transport in humans. The rodent brain removes waste better during sleep or anesthesia compared with the awake state. Animals exhibit different body posture during the awake and sleep states, which might affect the brain's waste removal efficiency. We investigated the influence of body posture on brainwide transport of inert tracers of anesthetized rodents. The major finding of our study was that waste, including Aβ, removal was most efficient in the lateral position (compared with the prone position), which mimics the natural resting/sleeping position of rodents. Although our finding awaits testing in humans, we speculate that the lateral position during sleep has advantage with regard to the removal of waste products including Aβ, because clinical studies have shown that sleep drives Aβ clearance from the brain. Copyright © 2015 the authors 0270-6474/15/3511034-11$15.00/0.

The Effect of Body Posture on Brain Glymphatic Transport

PubMed Central

Lee, Hedok; Xie, Lulu; Yu, Mei; Kang, Hongyi; Feng, Tian; Deane, Rashid; Logan, Jean; Nedergaard, Maiken

2015-01-01

The glymphatic pathway expedites clearance of waste, including soluble amyloid β (Aβ) from the brain. Transport through this pathway is controlled by the brain's arousal level because, during sleep or anesthesia, the brain's interstitial space volume expands (compared with wakefulness), resulting in faster waste removal. Humans, as well as animals, exhibit different body postures during sleep, which may also affect waste removal. Therefore, not only the level of consciousness, but also body posture, might affect CSF–interstitial fluid (ISF) exchange efficiency. We used dynamic-contrast-enhanced MRI and kinetic modeling to quantify CSF-ISF exchange rates in anesthetized rodents' brains in supine, prone, or lateral positions. To validate the MRI data and to assess specifically the influence of body posture on clearance of Aβ, we used fluorescence microscopy and radioactive tracers, respectively. The analysis showed that glymphatic transport was most efficient in the lateral position compared with the supine or prone positions. In the prone position, in which the rat's head was in the most upright position (mimicking posture during the awake state), transport was characterized by “retention” of the tracer, slower clearance, and more CSF efflux along larger caliber cervical vessels. The optical imaging and radiotracer studies confirmed that glymphatic transport and Aβ clearance were superior in the lateral and supine positions. We propose that the most popular sleep posture (lateral) has evolved to optimize waste removal during sleep and that posture must be considered in diagnostic imaging procedures developed in the future to assess CSF-ISF transport in humans. SIGNIFICANCE STATEMENT The rodent brain removes waste better during sleep or anesthesia compared with the awake state. Animals exhibit different body posture during the awake and sleep states, which might affect the brain's waste removal efficiency. We investigated the influence of body posture on brainwide transport of inert tracers of anesthetized rodents. The major finding of our study was that waste, including Aβ, removal was most efficient in the lateral position (compared with the prone position), which mimics the natural resting/sleeping position of rodents. Although our finding awaits testing in humans, we speculate that the lateral position during sleep has advantage with regard to the removal of waste products including Aβ, because clinical studies have shown that sleep drives Aβ clearance from the brain. PMID:26245965

Influence of prolonged wearing of unstable shoes on upright standing postural control.

PubMed

Sousa, Andreia S P; Macedo, Rui; Santos, Rubim; Sousa, Filipa; Silva, Andreia; Tavares, João Manuel R S

2016-02-01

To study the influence of prolonged wearing of unstable shoes on standing postural control in prolonged standing workers. The participants were divided into two groups: one wore unstable shoes while the other wore conventional shoes for 8weeks. Stabilometry parameters related to centre of pressure (CoP), rambling (RM) and trembling (TR) as well as the total agonist/antagonist muscle activity, antagonist co-activation and reciprocal activation were evaluated during upright standing, before and after the 8weeks period. In both moments, the subjects were evaluated wearing the unstable shoes and in barefoot. The unstable shoe condition presented increased CoP displacement related variables and decreased co-activation command compared to barefoot before and after the intervention. The prolonged wearing of unstable shoes led to: (1) reduction of medial-lateral CoP root mean square and area; (2) decreased anteroposterior RM displacement; (3) increased anteroposterior RM mean velocity and mediolateral RM displacement; (4) decreased anteroposterior TR RMS; and (5) increased thigh antagonist co-activation in the unstable shoe condition. The unstable shoe condition is associated to a higher destabilising effect that leads to a selection of more efficient and accurate postural commands compared to barefoot. Prolonged wearing of unstable shoes provides increased effectiveness and performance of the postural control system, while wearing of unstable shoes in upright standing, that are reflected by changes in CoP related variables and by a reorganisation of postural control commands. Copyright © 2015 Elsevier B.V. All rights reserved.

[Descending control of quiet standing and walking: a plausible neurophysiological basis of falls in elderly people].

PubMed

Nakajima, Masashi

2011-03-01

Quiet standing and walking are generally considered to be an automatic process regulated by sensory feedback. In our report "Astasia without abasia due to peripheral neuropathy," which was published in 1994, we proposed that forced stepping in patients lacking the ankle torque is a compensatory motor control in order to maintain an upright posture. A statistical-biomechanics approach to the human postural control system has revealed open-loop (descending) control as well as closed-loop (feedback) control in quiet standing, and fractal dynamics in stride-to-stride fluctuations of walking. The descending control system of bipedal upright posture and gait may have a functional link to cognitive domains. Increasing dependence on the descending control system with aging may play a role in falls in elderly people.

Detection of Obstructive sleep apnea in awake subjects by exploiting body posture effects on the speech signal.

PubMed

Kriboy, M; Tarasiuk, A; Zigel, Y

2014-01-01

Obstructive sleep apnea (OSA) is a common sleep disorder. OSA is associated with several anatomical and functional abnormalities of the upper airway. It was shown that these abnormalities in the upper airway are also likely to be the reason for increased rate of apneic events in the supine position. Functional and structural changes in the vocal tract can affect the acoustic properties of speech. We hypothesize that acoustic properties of speech that are affected by body position may aid in distinguishing between OSA and non-OSA patients. We aimed to explore the possibility to differentiate OSA and non-OSA patients by analyzing the acoustic properties of their speech signal in upright sitting and supine positions. 35 awake patients were recorded while pronouncing sustained vowels in the upright sitting and supine positions. Using linear discriminant analysis (LDA) classifier, accuracy of 84.6%, sensitivity of 92.7%, and specificity of 80.0% were achieved. This study provides the proof of concept that it is possible to screen for OSA by analyzing and comparing speech properties acquired in upright sitting vs. supine positions. An acoustic-based screening system during wakefulness may address the growing needs for a reliable OSA screening tool; further studies are needed to support these findings.

Eye, head, and body coordination during large gaze shifts in rhesus monkeys: movement kinematics and the influence of posture.

PubMed

McCluskey, Meaghan K; Cullen, Kathleen E

2007-04-01

Coordinated movements of the eye, head, and body are used to redirect the axis of gaze between objects of interest. However, previous studies of eye-head gaze shifts in head-unrestrained primates generally assumed the contribution of body movement to be negligible. Here we characterized eye-head-body coordination during horizontal gaze shifts made by trained rhesus monkeys to visual targets while they sat upright in a standard primate chair and assumed a more natural sitting posture in a custom-designed chair. In both postures, gaze shifts were characterized by the sequential onset of eye, head, and body movements, which could be described by predictable relationships. Body motion made a small but significant contribution to gaze shifts that were > or =40 degrees in amplitude. Furthermore, as gaze shift amplitude increased (40-120 degrees ), body contribution and velocity increased systematically. In contrast, peak eye and head velocities plateaued at velocities of approximately 250-300 degrees /s, and the rotation of the eye-in-orbit and head-on-body remained well within the physical limits of ocular and neck motility during large gaze shifts, saturating at approximately 35 and 60 degrees , respectively. Gaze shifts initiated with the eye more contralateral in the orbit were accompanied by smaller body as well as head movement amplitudes and velocities were greater when monkeys were seated in the more natural body posture. Taken together, our findings show that body movement makes a predictable contribution to gaze shifts that is systematically influenced by factors such as orbital position and posture. We conclude that body movements are part of a coordinated series of motor events that are used to voluntarily reorient gaze and that these movements can be significant even in a typical laboratory setting. Our results emphasize the need for caution in the interpretation of data from neurophysiological studies of the control of saccadic eye movements and/or eye-head gaze shifts because single neurons can code motor commands to move the body as well as the head and eyes.

Reinforcement learning for stabilizing an inverted pendulum naturally leads to intermittent feedback control as in human quiet standing.

PubMed

Michimoto, Kenjiro; Suzuki, Yasuyuki; Kiyono, Ken; Kobayashi, Yasushi; Morasso, Pietro; Nomura, Taishin

2016-08-01

Intermittent feedback control for stabilizing human upright stance is a promising strategy, alternative to the standard time-continuous stiffness control. Here we show that such an intermittent controller can be established naturally through reinforcement learning. To this end, we used a single inverted pendulum model of the upright posture and a very simple reward function that gives a certain amount of punishments when the inverted pendulum falls or changes its position in the state space. We found that the acquired feedback controller exhibits hallmarks of the intermittent feedback control strategy, namely the action of the feedback controller is switched-off intermittently when the state of the pendulum is located near the stable manifold of the unstable saddle-type upright equilibrium of the inverted pendulum with no active control: this action provides an opportunity to exploit transiently converging dynamics toward the unstable upright position with no help of the active feedback control. We then speculate about a possible physiological mechanism of such reinforcement learning, and suggest that it may be related to the neural activity in the pedunculopontine tegmental nucleus (PPN) of the brainstem. This hypothesis is supported by recent evidence indicating that PPN might play critical roles for generation and regulation of postural tonus, reward prediction, as well as postural instability in patients with Parkinson's disease.

Evaluation of the effect of postural and gravitational variations on the distribution of pulmonary blood flow via an image-based computational model.

PubMed

Burrowes, K S; Hunter, P J; Tawhai, M H

2005-01-01

We have developed an image-based computational model of blood flow within the human pulmonary circulation in order to investigate the distribution of flow under various conditions of posture and gravity. Geometric models of the lobar surfaces and largest arterial and venous vessels were derived from multi-detector row X-ray computed tomography. The remaining blood vessels were generated using a volume-filling branching algorithm. Equations representing conservation of mass and momentum are solved within the vascular geometry to calculate pressure, radius, and velocity distributions. Flow solutions are obtained within the model in the upright, inverted, prone, and supine postures and in the upright posture with and without gravity. Additional equations representing large deformation mechanics are used to calculate the change in lung geometry and pressure distributions within the lung in the various postures - creating a coupled, co-dependent model of mechanics and flow. The embedded vascular meshes deform in accordance with the lung geometry. Results illustrate a persistent flow gradient from the top to the bottom of the lung even in the absence of gravity and in all postures, indicating that vascular branching structure is largely responsible for the distribution of flow.

Effects of visual motion consistent or inconsistent with gravity on postural sway.

PubMed

Balestrucci, Priscilla; Daprati, Elena; Lacquaniti, Francesco; Maffei, Vincenzo

2017-07-01

Vision plays an important role in postural control, and visual perception of the gravity-defined vertical helps maintaining upright stance. In addition, the influence of the gravity field on objects' motion is known to provide a reference for motor and non-motor behavior. However, the role of dynamic visual cues related to gravity in the control of postural balance has been little investigated. In order to understand whether visual cues about gravitational acceleration are relevant for postural control, we assessed the relation between postural sway and visual motion congruent or incongruent with gravity acceleration. Postural sway of 44 healthy volunteers was recorded by means of force platforms while they watched virtual targets moving in different directions and with different accelerations. Small but significant differences emerged in sway parameters with respect to the characteristics of target motion. Namely, for vertically accelerated targets, gravitational motion (GM) was associated with smaller oscillations of the center of pressure than anti-GM. The present findings support the hypothesis that not only static, but also dynamic visual cues about direction and magnitude of the gravitational field are relevant for balance control during upright stance.

Seated saline suppression testing for the diagnosis of primary aldosteronism: a preliminary study.

PubMed

Ahmed, Ashraf H; Cowley, Diane; Wolley, Martin; Gordon, Richard D; Xu, Shengxin; Taylor, Paul J; Stowasser, Michael

2014-08-01

Failure of aldosterone suppression by sodium loading during fludrocortisone suppression testing (FST) or saline suppression testing (SST) confirms primary aldosteronism (PA). We previously found recumbent SST (RSST) to lack sensitivity. Aldosterone levels can be higher upright (e.g. seated) than recumbent in patients with PA and upright levels are used during FST. We therefore hypothesized that seated SST (SSST) is more sensitive than RSST, especially for posture-responsive PA. Of 66 patients who underwent FST (upright plasma aldosterone levels measured at 10am basally and after 4 days fludrocortisone 0.1 mg 6-hourly and oral salt loading), 31 underwent SST (aldosterone levels measured basally at 8am and after infusion of 2 L normal saline over 4h) both recumbent and seated in randomized order and at least 2 weeks apart. FST confirmed PA in 23 of 31 patients (day 4 upright aldosterone level >165 pmol/L), excluded PA in three and was originally "inconclusive" in five. However, one with "inconclusive" FST had PA confirmed by lateralizing AVS and was reclassified "unilateral PA". Of 24 with confirmed PA (eight unilateral, 11 bilateral, and five undetermined subtype), 23 (96%) tested positive by SSST (4-h aldosterone level >165 pmol/L) compared with 8 (33%) by RSST (4-h plasma aldosterone level >140 pmol/L) (P < .001). RSST missed one unilateral, all bilateral, and four with as-yet undetermined subtype. RSST was positive in 7 of 10 (70%) posture-unresponsive vs one of 14 (7.1%) posture-responsive patients (P < .005). These preliminary results suggest that seated SST may be superior to recumbent SST in terms of sensitivity for detecting PA, especially posture-responsive forms, and may represent a reliable alternative to FST.

Simultaneous multi-depth assessment of tissue oxygen saturation in thenar and forearm using near-infrared spectroscopy during a simple cardiovascular challenge

PubMed Central

2009-01-01

Introduction Hypovolemia and hypovolemic shock are life-threatening conditions that occur in numerous clinical scenarios. Near-infrared spectroscopy (NIRS) has been widely explored, successfully and unsuccessfully, in an attempt to use it as an early detector of hypovolemia by measuring tissue oxygen saturation (StO2). In order to investigate the measurement site dependence and probe dependence of NIRS in response to hemodynamic changes, such as hypovolemia, we applied a simple cardiovascular challenge: a posture change from supine to upright, causing a decrease in stroke volume (as in hypovolemia) and a heart rate increase in combination with peripheral vasoconstriction to maintain adequate blood pressure. Methods Multi-depth NIRS was used in nine healthy volunteers to assess changes in StO2 in the thenar and forearm in response to the hemodynamic changes associated with a posture change from supine to upright. Results A posture change from supine to upright resulted in a significant increase (P < 0.001) in heart rate. Thenar StO2 did not respond to the hemodynamic changes following the posture change, whereas forearm StO2 did. Forearm StO2 was significantly lower (P < 0.001) in the upright position compared to supine for all probing depths. Conclusions The primary findings in this study were that forearm StO2 is a more sensitive parameter to hemodynamic changes than thenar StO2 and that the depth at which StO2 is measured is of minor influence. Our data support the use of forearm StO2 as a sensitive parameter for the detection of central hypovolemia and hypovolemic shock in (trauma) patients. PMID:19951389

Effect of epidural blood injection on upright posture intolerance in patients with headaches due to intracranial hypotension: A prospective study.

PubMed

Qureshi, Adnan I; Kherani, Danish; Waqas, Muhammad A; Qureshi, Mushtaq H; Raja, Faisal M; Wallery, Shawn S

2018-06-19

We performed a prospective study to quantify changes in various aspects of upright posture intolerance in patients with intracranial hypotension. Six patients were provided a standard questionnaire before, immediately after epidural blood patch injection and at follow-up visit within 1 month after epidural blood injection inquiring: (a) How long can they stand straight without any support? (b) Do they feel any sense of sickness when they sit or lie down after standing? (c) How long do they have to wait before they are comfortable standing again after they have stood straight? (d) How effectively and fast can they get up from sitting or lying position to stand straight? and (e) Rate their activities in upright posture without support on a standard vertical visual analogue scale between 100 (can do everything) and 0 (cannot do anything). All patients responded that they could not stand straight for ≥30 min (four responding <5 min) on pretreatment evaluation. All patients reported improvement in this measure immediately postprocedure with two reporting ≥30 min. At follow-up, three patients reported further improvement and one patient reported worsening in this measure. The magnitude of improvement ranged from 10 to 80 points increase immediately postprocedure in their ability to perform activities, while they are standing without any support on visual analogue scale. At follow-up, four patient reported additional improvement in their ability to perform activities, while they are standing without any support (ranged from 10 to 20 points increase compared with immediately postprocedure rating). We present semiquantitative data on various aspects of upright posture intolerance in patients with intracranial hypotension before and after epidural blood injection. © 2018 The Authors. Brain and Behavior published by Wiley Periodicals, Inc.

On the importance of body posture and skin modelling with respect to in situ electric field strengths in magnetic field exposure scenarios

NASA Astrophysics Data System (ADS)

Schmid, Gernot; Hirtl, Rene

2016-06-01

The reference levels and maximum permissible exposure values for magnetic fields that are currently used have been derived from basic restrictions under the assumption of upright standing body models in a standard posture, i.e. with arms laterally down and without contact with metallic objects. Moreover, if anatomical modelling of the body was used at all, the skin was represented as a single homogeneous tissue layer. In the present paper we addressed the possible impacts of posture and skin modelling in scenarios of exposure to a 50 Hz uniform magnetic field on the in situ electric field strength in peripheral tissues, which must be limited in order to avoid peripheral nerve stimulation. We considered different body postures including situations where body parts form large induction loops (e.g. clasped hands) with skin-to-skin and skin-to-metal contact spots and compared the results obtained with a homogeneous single-layer skin model to results obtained with a more realistic two-layer skin representation consisting of a low-conductivity stratum corneum layer on top of a combined layer for the cellular epidermis and dermis. Our results clearly indicated that postures with loops formed of body parts may lead to substantially higher maximum values of induced in situ electric field strengths than in the case of standard postures due to a highly concentrated current density and in situ electric field strength in the skin-to-skin and skin-to-metal contact regions. With a homogeneous single-layer skin, as is used for even the most recent anatomical body models in exposure assessment, the in situ electric field strength may exceed the basic restrictions in such situations, even when the reference levels and maximum permissible exposure values are not exceeded. However, when using the more realistic two-layer skin model the obtained in situ electric field strengths were substantially lower and no violations of the basic restrictions occurred, which can be explained by the current-limiting effect of the low-conductivity stratum corneum layer.

A radiographic assessment of lumbar spine posture in four different upright standing positions.

PubMed

Gallagher, Kaitlin M; Sehl, Michael; Callaghan, Jack P

2016-08-01

Approximately 50% of a sample population will develop prolonged standing induced low back pain. The cause of this pain may be due to their lumbar spine posture. The purpose of this study was to investigate differences in lumbar posture between 17 participants categorized as a pain or non-pain developers during level ground standing. A secondary purpose was to evaluate the influence of two standing aids (an elevated surface to act as a foot rest and declined sloped surface) on lumbopelvic posture. Four sagittal plane radiographs were taken: a normal standing position on level ground, when using an elevated foot rest, using a declined sloped surface, and maximum lumbar spine extension as a reference posture. Lumbosacral lordosis, total lumbar lordosis, and L1/L2 and L5/S1 intervertebral joint angles were measured on each radiograph. There was a significant difference between the lumbosacral lordosis angle and L5/S1 angles in upright versus maximum extension; however, this was independent of pain group. The elevated surface was most effective at causing lumbosacral spine flexion. Potentially successful postures for eliminating low back pain during prolonged standing mainly influence the lower lumbar lordosis. Future work should assess the influence of hip posture on low back pain development during standing. Copyright © 2016 Elsevier Ltd. All rights reserved.

Elbow joint adductor moment arm as an indicator of forelimb posture in extinct quadrupedal tetrapods

PubMed Central

Fujiwara, Shin-ichi; Hutchinson, John R.

2012-01-01

Forelimb posture has been a controversial aspect of reconstructing locomotor behaviour in extinct quadrupedal tetrapods. This is partly owing to the qualitative and subjective nature of typical methods, which focus on bony articulations that are often ambiguous and unvalidated postural indicators. Here we outline a new, quantitatively based forelimb posture index that is applicable to a majority of extant tetrapods. By determining the degree of elbow joint adduction/abduction mobility in several tetrapods, the carpal flexor muscles were determined to also play a role as elbow adductors. Such adduction may play a major role during the stance phase in sprawling postures. This role is different from those of upright/sagittal and sloth-like creeping postures, which, respectively, depend more on elbow extensors and flexors. Our measurements of elbow muscle moment arms in 318 extant tetrapod skeletons (Lissamphibia, Synapsida and Reptilia: 33 major clades and 263 genera) revealed that sprawling, sagittal and creeping tetrapods, respectively, emphasize elbow adductor, extensor and flexor muscles. Furthermore, scansorial and non-scansorial taxa, respectively, emphasize flexors and extensors. Thus, forelimb postures of extinct tetrapods can be qualitatively classified based on our quantitative index. Using this method, we find that Triceratops (Ceratopsidae), Anhanguera (Pterosauria) and desmostylian mammals are categorized as upright/sagittally locomoting taxa. PMID:22357261

Evolution of seahorses' upright posture was linked to Oligocene expansion of seagrass habitats

PubMed Central

Teske, Peter R.; Beheregaray, Luciano B.

2009-01-01

Seahorses (Syngnathidae: Hippocampus) are iconic marine teleosts that are readily identifiable by their upright posture. The fossil record is inadequate to shed light on the evolution of this trait because it lacks transitional forms. There are, however, extant syngnathid species (the pygmy pipehorses) that look like horizontally swimming seahorses and that might represent a surviving evolutionary link between the benthic seahorses and other, free-swimming members of the family Syngnathidae. Using sequence data from five nuclear loci, we confirm the sister taxon relationship between seahorses and pygmy pipehorses. Molecular dating indicates that the two taxa diverged during the Late Oligocene. During this time, tectonic events in the Indo-West Pacific resulted in the formation of vast amounts of new shallow-water areas and associated expansion of seagrass habitats that would have favoured the seahorses’ upright posture by improving their camouflage while not affecting their manoeuvrability negatively. The molecular techniques employed here provide new insights into the evolution of a taxon whose fossil record is incomplete, but whose evolutionary history is so recent that the major stages of morphological evolution are still represented in extant species. PMID:19451164

The Effect of Working Position on Trunk Posture and Exertion for Routine Nursing Tasks: An Experimental Study

PubMed Central

Freitag, Sonja

2014-01-01

Objectives: To examine the influence of the two following factors on the proportion of time that nurses spend in a forward-bending trunk posture: (i) the bed height during basic care activities at the bedside and (ii) the work method during basic care activities in the bathroom. A further aim was to examine the connection between the proportion of time spent in a forward-bending posture and the perceived exertion. Methods: Twelve nurses in a geriatric nursing home each performed a standardized care routine at the bedside and in the bathroom. The CUELA (German abbreviation for ‘computer-assisted recording and long-term analysis of musculoskeletal loads’) measuring system was used to record all trunk inclinations. Each participant conducted three tests with the bed at different heights (knee height, thigh height, and hip height) and in the bathroom, three tests were performed with different work methods (standing, kneeling, and sitting). After each test, participants rated their perceived exertion on the 15-point Borg scale (6 = no exertion at all and 20 = exhaustion). Results: If the bed was raised from knee to thigh level, the proportion of time spent in an upright position increased by 8.2% points. However, the effect was not significant (P = 0.193). Only when the bed was raised to hip height, there was a significant increase of 19.8% points (reference: thigh level; P = 0.003) and 28.0% points (reference: knee height; P < 0.001). Bathroom tests: compared with the standing work method, the kneeling and sitting work methods led to a significant increase in the proportion of time spent in an upright posture, by 19.4% points (P = 0.003) and 25.7% points (P < 0.001), respectively. The greater the proportion of time spent in an upright position, the lower the Borg rating (P < 0.001) awarded. Conclusions: The higher the proportion of time that nursing personnel work in an upright position, the less strenuous they perceive the work to be. Raising the bed to hip height and using a stool in the bathroom significantly increase the proportion of time that nursing personnel work in an upright position. Nursing staff can spend a considerably greater proportion of their time in an ergonomic posture if stools and height-adjustable beds are provided in healthcare institutions. PMID:24371043

The effect of working position on trunk posture and exertion for routine nursing tasks: an experimental study.

PubMed

Freitag, Sonja; Seddouki, Rachida; Dulon, Madeleine; Kersten, Jan Felix; Larsson, Tore J; Nienhaus, Albert

2014-04-01

To examine the influence of the two following factors on the proportion of time that nurses spend in a forward-bending trunk posture: (i) the bed height during basic care activities at the bedside and (ii) the work method during basic care activities in the bathroom. A further aim was to examine the connection between the proportion of time spent in a forward-bending posture and the perceived exertion. Twelve nurses in a geriatric nursing home each performed a standardized care routine at the bedside and in the bathroom. The CUELA (German abbreviation for 'computer-assisted recording and long-term analysis of musculoskeletal loads') measuring system was used to record all trunk inclinations. Each participant conducted three tests with the bed at different heights (knee height, thigh height, and hip height) and in the bathroom, three tests were performed with different work methods (standing, kneeling, and sitting). After each test, participants rated their perceived exertion on the 15-point Borg scale (6 = no exertion at all and 20 = exhaustion). If the bed was raised from knee to thigh level, the proportion of time spent in an upright position increased by 8.2% points. However, the effect was not significant (P = 0.193). Only when the bed was raised to hip height, there was a significant increase of 19.8% points (reference: thigh level; P = 0.003) and 28.0% points (reference: knee height; P < 0.001). Bathroom tests: compared with the standing work method, the kneeling and sitting work methods led to a significant increase in the proportion of time spent in an upright posture, by 19.4% points (P = 0.003) and 25.7% points (P < 0.001), respectively. The greater the proportion of time spent in an upright position, the lower the Borg rating (P < 0.001) awarded. The higher the proportion of time that nursing personnel work in an upright position, the less strenuous they perceive the work to be. Raising the bed to hip height and using a stool in the bathroom significantly increase the proportion of time that nursing personnel work in an upright position. Nursing staff can spend a considerably greater proportion of their time in an ergonomic posture if stools and height-adjustable beds are provided in healthcare institutions.

Water-level representation by men and women as a function of rod-and-frame test proficiency and visual and postural information.

PubMed

Robert, M; Ohlmann, T

1994-01-01

In the water-level task, it has been repeatedly shown that, compared with men, women more often fail to represent the surface of a liquid as horizontal regardless of the tilt of the container. An attempt was made to reduce this robust gender gap through the manipulation of relevant upright references conveyed both by the position of the stimuli and the posture of the subject. It was reasoned that bringing the women to focus on such gravitational references through postural adjustment might help their performance equal that of men, thus shedding some light on the nature of the difficulty they experience in the standard setting. A lesser effect was anticipated among men. However, the results showed that, even after controlling for proficiency in the correlated visuospatial situation of the rod-and-frame test, the performance of men always surpassed that of women. Irrespective of gender, water-level representation on vertical sheets was unaffected by the subject's posture, whereas it improved when horizontal sheets were coupled with the most unstable posture. Whereas the persistence of the yet-unaccounted-for gender difference was underscored, the contributions of visual and postural cues issued at arm and full-body levels were discussed.

Postural control and ventilatory drive during voluntary hyperventilation and carbon dioxide rebreathing.

PubMed

David, Pascal; Laval, David; Terrien, Jérémy; Petitjean, Michel

2012-01-01

The present study sought to establish links between hyperventilation and postural stability. Eight university students were asked to stand upright under two hyperventilation conditions applied randomly: (1) a metabolic hyperventilation induced by 5 min of hypercapnic-hyperoxic rebreathing (CO(2)-R); and, (2) a voluntary hyperventilation (VH) of 3 min imposed by a metronome set at 25 cycles per min. Recordings were obtained with eyes open, with the subjects standing on a force plate over 20-s periods. Ventilatory response, displacements in the centre of pressure in both the frontal and sagittal planes and fluctuations in the three planes of the ground reaction force were monitored in the time and frequency domains. Postural changes related to respiratory variations were quantified by coherence analysis. Myoelectric activities of the calf muscles were recorded using surface electromyography. Force plate measurements revealed a reduction in postural stability during both CO(2)-R and VH conditions, mainly in the sagittal plane. Coherence analysis provided evidence of a ventilatory origin in the vertical ground reaction force fluctuations during VH. Electromyographic analyses showed different leg muscles strategies, assuming the existence of links between the control of respiration and the control of posture. Our results suggest that the greater disturbing effects caused by voluntary hyperventilation on body balance are more compensated when respiration is under automatic control. These findings may have implications for understanding the organisation of postural and respiratory activities and suggest that stability of the body may be compromised in situations in which respiratory demand increases and requires voluntary control.

Acute alcohol intoxication impairs segmental body alignment in upright standing.

PubMed

Hafstrom, A; Patel, M; Modig, F; Magnusson, M; Fransson, P A

2014-01-01

Balance control when standing upright is a complex process requiring input from several partly independent mechanisms such as coordination, feedback and feedforward control, and adaptation. Acute alcohol intoxication from ethanol is recognized as a major contributor to accidental falls requiring medical care. This study aimed to investigate if intoxication at 0.06 and 0.10% blood alcohol concentration affected body alignment. Mean angular positions of the head, shoulder, hip, and knee were measured with 3D-motion analysis and compared with the ankle position in 25 healthy adults during standing with or without perturbations, and with eyes open or closed. Alcohol intoxication had significant effects on body alignment during perturbed and unperturbed stance, and on adaptation to perturbations. It induced a significantly more posterior alignment of the knees and shoulders, and a tendency for a more posterior and left deviated head alignment in perturbed stance than when sober. The impact of alcohol intoxication was most apparent on the knee alignment, where availability of visual information deteriorated the adaptation to perturbations. Thus, acute alcohol intoxication resulted in inadequate balance control strategies with increased postural rigidity and impaired adaptation to perturbations. These factors probably contribute to the increased risk of falling when intoxicated with alcohol.

The dynamic representation of gravity is suspended when the idiotropic vector is misaligned with gravity.

PubMed

De Sá Teixeira, Nuno Alexandre; Hecht, Heiko

2014-01-01

When people are asked to indicate the vanishing location of a moving target, errors in the direction of motion (representational momentum) and in the direction of gravity (representational gravity) are usually found. These errors possess a temporal course wherein the memory for the location of the target drifts downwards with increasing temporal intervals between target's disappearance and participant's responses (representational trajectory). To assess if representational trajectory is a body-referenced or a world-referenced phenomenon. A behavioral localization method was employed with retention times between 0 and 1400 ms systematically imposed after the target's disappearance. The target could move horizontally (rightwards or leftwards) or vertically (upwards or downwards). Body posture was varied in a counterbalanced order between sitting upright and lying on the side (left lateral decubitus position). In the upright task, the memory for target location drifted downwards with time in the direction of gravity. This time course did not emerge for the decubitus task, where idiotropic dominance was found. The dynamic visual representation of gravity is neither purely body-referenced nor world-referenced. It seems to be modulated instead by the relationship between the idiotropic vector and physical gravity.

The effect of spinal position on sciatic nerve excursion during seated neural mobilisation exercises: an in vivo study using ultrasound imaging

PubMed Central

Ellis, Richard; Osborne, Samantha; Whitfield, Janessa; Parmar, Priya; Hing, Wayne

2017-01-01

Objectives Research has established that the amount of inherent tension a peripheral nerve tract is exposed to influences nerve excursion and joint range of movement (ROM). The effect that spinal posture has on sciatic nerve excursion during neural mobilisation exercises has yet to be determined. The purpose of this research was to examine the influence of different sitting positions (slump-sitting versus upright-sitting) on the amount of longitudinal sciatic nerve movement during different neural mobilisation exercises commonly used in clinical practice. Methods High-resolution ultrasound imaging followed by frame-by-frame cross-correlation analysis was used to assess sciatic nerve excursion. Thirty-four healthy participants each performed three different neural mobilisation exercises in slump-sitting and upright-sitting. Means comparisons were used to examine the influence of sitting position on sciatic nerve excursion for the three mobilisation exercises. Linear regression analysis was used to determine whether any of the demographic data represented predictive variables for longitudinal sciatic nerve excursion. Results There was no significant difference in sciatic nerve excursion (across all neural mobilisation exercises) observed between upright-sitting and slump-sitting positions (P = 0.26). Although greater body mass index, greater knee ROM and younger age were associated with higher levels of sciatic nerve excursion, this model of variables offered weak predictability (R2 = 0.22). Discussion Following this study, there is no evidence that, in healthy people, longitudinal sciatic nerve excursion differs significantly with regards to the spinal posture (slump-sitting and upright-sitting). Furthermore, although some demographic variables are weak predictors, the high variance suggests that there are other unknown variables that may predict sciatic nerve excursion. It can be inferred from this research that clinicians can individualise the design of seated neural mobilisation exercises, using different seated positions, based upon patient comfort and minimisation of neural mechanosensitivity with the knowledge that sciatic nerve excursion will not be significantly influenced. PMID:28559669

What triggers the continuous muscle activity during upright standing?

PubMed

Masani, Kei; Sayenko, Dimitry G; Vette, Albert H

2013-01-01

The ankle extensors play a dominant role in controlling the equilibrium during bipedal quiet standing. Their primary role is to resist the gravity toppling torque that pulls the body forward. The purpose of this study was to investigate whether the continuous muscle activity of the anti-gravity muscles during standing is triggered by the joint torque requirement for opposing the gravity toppling torque, rather than by the vertical load on the lower limbs. Healthy adults subjects stood on a force plate. The ankle torque, ankle angle, and electromyograms from the right lower leg muscles were measured. A ground-fixed support device was used to support the subject at his/her knees, without changing the posture from the free standing one. During the supported condition, which eliminates the ankle torque requirement while maintaining both the vertical load on the lower limbs and the natural upright standing posture, the plantarflexor activity was attenuated to the resting level. Also, this attenuated plantarflexor activity was found only in one side when the ipsilateral leg was supported. Our results suggest that the vertical load on the lower limb is not determinant for inducing the continuous muscle activity in the anti-gravity muscles, but that it depends on the required joint torque to oppose the gravity toppling torque. Copyright © 2012 Elsevier B.V. All rights reserved.

Effect of antigravity suit inflation on cardiovascular, PRA, and PVP responses in humans. [Plasma Renin Activity and Plasma VasoPressin

NASA Technical Reports Server (NTRS)

Kravik, S. E.; Keil, L. C.; Geelen, G.; Wade, C. E.; Barnes, P. R.

1986-01-01

The effects of lower body and abdominal pressure, produced by antigravity suit inflation, on blood pressure, pulse rate, fluid and electrolyte shift, plasma vasopressin and plasma renin activity in humans in upright postures were studied. Five men and two women stood upright for 3 hr with the suit being either inflated or uninflated. In the control tests, the suit was inflated only during the latter part of the trials. Monitoring was carried out with a sphygnomanometer, with sensors for pulse rates, and using a photometer and osmometer to measure blood serum characteristics. The tests confirmed earlier findings that the anti-g suit eliminates increases in plasma renin activity. Also, the headward redistribution of blood obtained in the tests commends the anti-g suit as an alternative to water immersion or bed rest for initial weightlessness studies.

Characterizing Postural Sway during Quiet Stance Based on the Intermittent Control Hypothesis

NASA Astrophysics Data System (ADS)

Nomura, Taishin; Nakamura, Toru; Fukada, Kei; Sakoda, Saburo

2007-07-01

This article illustrates a signal processing methodology for the time series of postural sway and accompanied electromyographs from the lower limb muscles during quiet stance. It was shown that the proposed methodology was capable of identifying the underlying postural control mechanisms. A preliminary application of the methodology provided evidence that supports the intermittent control hypothesis alternative to the conventional stiffness control hypothesis during human quiet upright stance.

PARKINSON'S DISEASE PATIENTS WITH DOMINANT HEMIBODY AFFECTED BY THE DISEASE RELY MORE ON VISION TO MAINTAIN UPRIGHT POSTURAL CONTROL.

PubMed

Lahr, Juliana; Pereira, Marcelo Pinto; Pelicioni, Paulo Henrique Silva; De Morais, Luana Carolina; Gobbi, Lilian Teresa Bucken

2015-12-01

This study assesses the association between disease onset side (dominant or non-dominant) and vision on postural control of Parkinson's disease patients. Patient volunteers composed two groups, according to the onset side affected: Dominant group (n=9; M age=66.1 yr., SD=7.2; 6 women, 3 men) and Non-dominant group (n=9; M age=67.4 yr., SD=6.4; 6 women, 3 men). The groups' postural control was assessed by posturography during quiet upright stance in two conditions, Eyes open and Eyes closed. Two-way analyses of variance (ANOVAs; group×condition) with repeated measures for the second factor assessed the differences associated with affected hemibody and vision on postural control. Analyses indicated that patients with the dominant side affected also presented significantly greater variation in center of pressure than those with the non-dominant side affected, mainly in the Eyes closed condition. The results demonstrate a higher reliance on vision in the dominant side, possibly to compensate somatosensory system impairments. These results also highlight the importance of analyzing the hemibody affected by the disease when postural control is assessed in this population.

Use of motor abundance in old adults in the regulation of a narrow-based stance.

PubMed

Hsu, Wei-Li; Lin, Kwan-Hwa; Yang, Rong-Sen; Cheng, Chih-Hsiu

2014-02-01

The ability to maintain stable balance while standing decreases with age. The body must coordinate multiple joints using "freeze" or "free" strategy, or a combination of both to ensure balance stability. The purpose of this study was to examine age-related changes in the use of motor abundance during upright stance on a narrow base without visual input. Uncontrolled manifold (UCM) analysis was used to decompose the movement variability of joints into goal-equivalent variability (GEV) and non-goal-equivalent variability (NGEV). The ratio between GEV and NGEV (UCM(ratio)) quantifies the joint coordination related to postural stability, and a high UCM(ratio) value indicates flexible control of joints. To perform balance tests, participants in this study (healthy young and old adults, 20 each) were asked to stand on a flat platform and on narrow wooden blocks with their eyes open and then eyes closed. In upright balance tests, both old and young adults maintained postural stability. GEV was greater than NGEV across all participants and conditions. However, GEV was higher in the young adults than in the old adults, whereas NGEV was higher in the old adults than in the young adults. Therefore, the old adults exhibited a lower UCM(ratio) than the young adults. The old adults were unable to exploit motor abundance and used a less flexible multi-joint coordination pattern to achieve stable balance. The UCM(ratio) value reflects the quality of postural control and can be used for assessing joint coordination in balance disorders.

Spatial orientation and balance control changes induced by altered gravitoinertial force vectors

NASA Technical Reports Server (NTRS)

Kaufman, G. D.; Wood, S. J.; Gianna, C. C.; Black, F. O.; Paloski, W. H.

2001-01-01

To better understand the mechanisms of human adaptation to rotating environments, we exposed 19 healthy subjects and 8 vestibular-deficient subjects ("abnormal"; four bilateral and four unilateral lesions) to an interaural centripetal acceleration of 1 g (resultant 45 degrees roll-tilt of 1.4 g) on a 0.8-m-radius centrifuge for periods of 90 min. The subjects sat upright (body z-axis parallel to centrifuge rotation axis) in the dark with head stationary, except during 4 min of every 10 min, when they performed head saccades toward visual targets switched on at 3- to 5-s intervals at random locations (within +/- 30 degrees) in the earth-horizontal plane. Eight of the normal subjects also performed the head saccade protocol in a stationary chair adjusted to a static roll-tilt angle of 45 degrees for 90 min (reproducing the change in orientation but not the magnitude of the gravitoinertial force on the centrifuge). Eye movements, including voluntary saccades directed along perceived earth- and head-referenced planes, were recorded before, during, and immediately after centrifugation. Postural center of pressure (COP) and multisegment body kinematics were also gathered before and within 10 min after centrifugation. Normal subjects overestimated roll-tilt during centrifugation and revealed errors in perception of head-vertical provided by directed saccades. Errors in this perceptual response tended to increase with time and became significant after approximately 30 min. Motion-sickness symptoms caused approximately 25% of normal subjects to limit their head movements during centrifugation and led three normal subjects to stop the test early. Immediately after centrifugation, subjects reported feeling tilted 10 degrees in the opposite direction, which was in agreement with the direction of their earth-referenced directed saccades. Postural COP, segmental body motion amplitude, and hip-sway frequency increased significantly after centrifugation. These postural effects were short-lived, however, with a recovery time of several postural test trials (minutes). There were also asymmetries in the direction of postcentrifugation COP and head tilt which depended on the subject's orientation during the centrifugation adaptation period (left ear or right ear out). The amount of total head movements during centrifugation correlated poorly or inversely with postcentrifugation postural stability, and the most unstable subject made no head movements. There was no decrease in postural stability after static tilt, although these subjects also reported a perceived tilt briefly after return to upright, and they also had COP asymmetries. Abnormal subjects underestimated roll-tilt during centrifugation, and their directed saccades revealed permanent spatial distortions. Bilateral abnormal subjects started out with poor postural control, but showed no postural decrements after centrifugation, while unilateral abnormal subjects had varying degrees of postural decrement, both in their everyday function and as a result of experiencing the centrifugation. In addition, three unilateral, abnormal subjects, who rode twice in opposite orientations, revealed a consistent orthogonal pattern of COP offsets after centrifugation. These results suggest that both orientation and magnitude of the gravitoinertial vector are used by the central nervous system for calibration of multiple orientation systems. A change in the background gravitoinertial force (otolith input) can rapidly initiate postural and perceptual adaptation in several sensorimotor systems, independent of a structured visual surround.

Spatial orientation and balance control changes induced by altered gravitoinertial force vectors.

PubMed

Kaufman, G D; Wood, S J; Gianna, C C; Black, F O; Paloski, W H

2001-04-01

To better understand the mechanisms of human adaptation to rotating environments, we exposed 19 healthy subjects and 8 vestibular-deficient subjects ("abnormal"; four bilateral and four unilateral lesions) to an interaural centripetal acceleration of 1 g (resultant 45 degrees roll-tilt of 1.4 g) on a 0.8-m-radius centrifuge for periods of 90 min. The subjects sat upright (body z-axis parallel to centrifuge rotation axis) in the dark with head stationary, except during 4 min of every 10 min, when they performed head saccades toward visual targets switched on at 3- to 5-s intervals at random locations (within +/- 30 degrees) in the earth-horizontal plane. Eight of the normal subjects also performed the head saccade protocol in a stationary chair adjusted to a static roll-tilt angle of 45 degrees for 90 min (reproducing the change in orientation but not the magnitude of the gravitoinertial force on the centrifuge). Eye movements, including voluntary saccades directed along perceived earth- and head-referenced planes, were recorded before, during, and immediately after centrifugation. Postural center of pressure (COP) and multisegment body kinematics were also gathered before and within 10 min after centrifugation. Normal subjects overestimated roll-tilt during centrifugation and revealed errors in perception of head-vertical provided by directed saccades. Errors in this perceptual response tended to increase with time and became significant after approximately 30 min. Motion-sickness symptoms caused approximately 25% of normal subjects to limit their head movements during centrifugation and led three normal subjects to stop the test early. Immediately after centrifugation, subjects reported feeling tilted 10 degrees in the opposite direction, which was in agreement with the direction of their earth-referenced directed saccades. Postural COP, segmental body motion amplitude, and hip-sway frequency increased significantly after centrifugation. These postural effects were short-lived, however, with a recovery time of several postural test trials (minutes). There were also asymmetries in the direction of postcentrifugation COP and head tilt which depended on the subject's orientation during the centrifugation adaptation period (left ear or right ear out). The amount of total head movements during centrifugation correlated poorly or inversely with postcentrifugation postural stability, and the most unstable subject made no head movements. There was no decrease in postural stability after static tilt, although these subjects also reported a perceived tilt briefly after return to upright, and they also had COP asymmetries. Abnormal subjects underestimated roll-tilt during centrifugation, and their directed saccades revealed permanent spatial distortions. Bilateral abnormal subjects started out with poor postural control, but showed no postural decrements after centrifugation, while unilateral abnormal subjects had varying degrees of postural decrement, both in their everyday function and as a result of experiencing the centrifugation. In addition, three unilateral, abnormal subjects, who rode twice in opposite orientations, revealed a consistent orthogonal pattern of COP offsets after centrifugation. These results suggest that both orientation and magnitude of the gravitoinertial vector are used by the central nervous system for calibration of multiple orientation systems. A change in the background gravitoinertial force (otolith input) can rapidly initiate postural and perceptual adaptation in several sensorimotor systems, independent of a structured visual surround.

Tai Chi training reduced coupling between respiration and postural control.

PubMed

Holmes, Matthew L; Manor, Brad; Hsieh, Wan-hsin; Hu, Kun; Lipsitz, Lewis A; Li, Li

2016-01-01

In order to maintain stable upright stance, the postural control system must account for the continuous perturbations to the body's center-of-mass including those caused by spontaneous respiration. Both aging and disease increase "posturo-respiratory synchronization;" which reflects the degree to which respiration affects postural sway fluctuations over time. Tai Chi training emphasizes the coordination of respiration and bodily movements and may therefore optimize the functional interaction between these two systems. The purpose of the project was to examine the effect of Tai Chi training on the interaction between respiration and postural control in older adults. We hypothesized that Tai Chi training would improve the ability of the postural control system to compensate for respiratory perturbations and thus, reduce posturo-respiratory synchronization. Participants were recruited from supportive housing facilities and randomized to a 12-week Tai Chi intervention (n=28; 86 ± 5 yrs) or educational-control program (n=34, 85 ± 6 yrs). Standing postural sway and respiration were simultaneously recorded with a force plate and respiratory belt under eyes-open and eyes-closed conditions. Posturo-respiratory synchronization was determined by quantifying the variation of the phase relationship between the dominant oscillatory mode of respiration and corresponding oscillations within postural sway. Groups were similar in age, gender distribution, height, body mass, and intervention compliance. Neither intervention altered average sway speed, sway magnitude or respiratory rate. As compared to the education-control group, however, Tai Chi training reduced posturo-respiratory synchronization when standing with eyes open or closed (p<0.001). Tai Chi training did not affect traditional parameters of standing postural control or respiration, yet reduced the coupling between respiration and postural control. The beneficial effects of Tai Chi training may therefore stem in part from optimization of this multi-system interaction. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Effect of low-dose scopolamine on autonomic control of the heart

NASA Technical Reports Server (NTRS)

Raeder, E. A.; Stys, A.; Cohen, R. J.

1997-01-01

Background: In low doses, scopolamine paradoxically enhances parasympathetic outflow to the heart. The mechanisms which mediate this action are not fully understood. Moreover, there are conflicting data regarding the potential role of sympathetic activity. This study in 17 healthy individuals was designed to characterize the influence of low dose transdermal scopolamine on the gain of the baroreflex and respiratory heart rate reflex and to determine the role of sympathetic activity. Methods: The effect of scopolamine was analyzed in the time and frequency domain by computing heart rate variability indices. The gains of the respiratory heart rate reflex and the baroreflex were estimated simultaneously by means of a cardiovascular system identification approach using an optimized autoregressive moving average algorithm. Measurements were repeated in the upright posture to assess the influence of enhanced sympathetic activity. In six subjects ambulatory ECGs were recorded to determine whether there are diurnal variations of the effect of scopolamine. Results: Scopolamine enhances vagal modulation of heart rate through both the respiratory-heart rate reflex and the baroreflex, as the gains of both were augmented by the drug in the supine and in the upright postures. Conclusions: Scopolamine increases parasympathetic cardiac control by augmenting the gain of the respiratory-heart rate and baroreflex. This action is not attenuated in the upright posture when sympathetic tone is increased.

Postural Compensation for Unilateral Vestibular Loss

PubMed Central

Peterka, Robert J.; Statler, Kennyn D.; Wrisley, Diane M.; Horak, Fay B.

2011-01-01

Postural control of upright stance was investigated in well-compensated, unilateral vestibular loss (UVL) subjects compared to age-matched control subjects. The goal was to determine how sensory weighting for postural control in UVL subjects differed from control subjects, and how sensory weighting related to UVL subjects’ functional compensation, as assessed by standardized balance and dizziness questionnaires. Postural control mechanisms were identified using a model-based interpretation of medial–lateral center-of-mass body-sway evoked by support-surface rotational stimuli during eyes-closed stance. The surface-tilt stimuli consisted of continuous pseudorandom rotations presented at four different amplitudes. Parameters of a feedback control model were obtained that accounted for each subject’s sway response to the surface-tilt stimuli. Sensory weighting factors quantified the relative contributions to stance control of vestibular sensory information, signaling body-sway relative to earth-vertical, and proprioceptive information, signaling body-sway relative to the surface. Results showed that UVL subjects made significantly greater use of proprioceptive, and therefore less use of vestibular, orientation information on all tests. There was relatively little overlap in the distributions of sensory weights measured in UVL and control subjects, although UVL subjects varied widely in the amount they could use their remaining vestibular function. Increased reliance on proprioceptive information by UVL subjects was associated with their balance being more disturbed by the surface-tilt perturbations than control subjects, thus indicating a deficiency of balance control even in well-compensated UVL subjects. Furthermore, there was some tendency for UVL subjects who were less able to utilize remaining vestibular information to also indicate worse functional compensation on questionnaires. PMID:21922014

The effect of resistance level and stability demands on recruitment patterns and internal loading of spine in dynamic flexion and extension using a simple trunk model.

PubMed

Zeinali-Davarani, Shahrokh; Shirazi-Adl, Aboulfazl; Dariush, Behzad; Hemami, Hooshang; Parnianpour, Mohamad

2011-07-01

The effects of external resistance on the recruitment of trunk muscles in sagittal movements and the coactivation mechanism to maintain spinal stability were investigated using a simple computational model of iso-resistive spine sagittal movements. Neural excitation of muscles was attained based on inverse dynamics approach along with a stability-based optimisation. The trunk flexion and extension movements between 60° flexion and the upright posture against various resistance levels were simulated. Incorporation of the stability constraint in the optimisation algorithm required higher antagonistic activities for all resistance levels mostly close to the upright position. Extension movements showed higher coactivation with higher resistance, whereas flexion movements demonstrated lower coactivation indicating a greater stability demand in backward extension movements against higher resistance at the neighbourhood of the upright posture. Optimal extension profiles based on minimum jerk, work and power had distinct kinematics profiles which led to recruitment patterns with different timing and amplitude of activation.

Neck posture and muscle activity are different when upside down: a human volunteer study.

PubMed

Newell, Robyn S; Blouin, Jean-Sébastien; Street, John; Cripton, Peter A; Siegmund, Gunter P

2013-11-15

Rollover crashes are dynamic and complex events in which head impacts with the roof can cause catastrophic neck injuries. Ex vivo and computational models are valuable in understanding, and ultimately preventing, these injuries. Although neck posture and muscle activity influence the resulting injury, there is currently no in vivo data describing these parameters immediately prior to a head-first impact. The specific objectives of this study were to determine the in vivo neck vertebral alignment and muscle activation levels when upside down, a condition that occurs during a rollover. Eleven human subjects (6F, 5M) were tested while seated upright and inverted in a custom-built apparatus. Vertebral alignment was measured using fluoroscopy and muscle activity was recorded using surface and indwelling electrodes in eight superficial and deep neck muscles. In vivo vertebral alignment and muscle activation levels differed between the upright and inverted conditions. When inverted and relaxed, the neck was more lordotic, C1 was aligned posterior to C7, the Frankfort plane was extended, and the activity of six muscles increased compared to upright and relaxed. When inverted subjects were asked to look forward to eliminate head extension, flexor muscle activity increased, C7 was more flexed, and C1 was aligned anterior to C7 versus upright and relaxed. Combined with the large inter-subject variability observed, these findings indicate that cadaveric or computational models designed to study injuries and prevention devices while inverted need to consider a variety of postures and muscle conditions to be relevant to the in vivo situation. © 2013 Elsevier Ltd. All rights reserved.

Clinical physiology of bed rest

NASA Technical Reports Server (NTRS)

Greenleaf, John E.

1993-01-01

Maintenance of optimal health in humans requires the proper balance between exercise, rest, and sleep as well as time in the upright position. About one-third of a lifetime is spent sleeping; and it is no coincidence that sleeping is performed in the horizontal position, the position in which gravitational influence on the body is minimal. Although enforced bed rest is necessary for the treatment of some ailments, in some cases it has probably been used unwisely. In addition to the lower hydrostatic pressure with the normally dependent regions of the cardiovascular system, body fuid compartments during bed rest in the horizontal body position, and virtual elimination of compression on the long bones of the skeletal system during bed rest (hypogravia), there is often reduction in energy metabolism due to the relative confinement (hypodynamia) and alteration of ambulatory circadian variations in metabolism, body temperature, and many hormonal systems. If patients are also moved to unfamiliar surroundings, they probably experience some feelings of anxiety and some sociopsychological problems. Adaptive physiological responses during bed rest are normal for that environment. They are attempts by the body to reduce unnecessary energy expenditure, to optimize its function, and to enhance its survival potential. Many of the deconditioning responses begin within the first day or two of bed rest; these early responses have prompted physicians to insist upon early resumption of the upright posture and ambulation of bedridden patients.

Postural control model interpretation of stabilogram diffusion analysis

NASA Technical Reports Server (NTRS)

Peterka, R. J.

2000-01-01

Collins and De Luca [Collins JJ. De Luca CJ (1993) Exp Brain Res 95: 308-318] introduced a new method known as stabilogram diffusion analysis that provides a quantitative statistical measure of the apparently random variations of center-of-pressure (COP) trajectories recorded during quiet upright stance in humans. This analysis generates a stabilogram diffusion function (SDF) that summarizes the mean square COP displacement as a function of the time interval between COP comparisons. SDFs have a characteristic two-part form that suggests the presence of two different control regimes: a short-term open-loop control behavior and a longer-term closed-loop behavior. This paper demonstrates that a very simple closed-loop control model of upright stance can generate realistic SDFs. The model consists of an inverted pendulum body with torque applied at the ankle joint. This torque includes a random disturbance torque and a control torque. The control torque is a function of the deviation (error signal) between the desired upright body position and the actual body position, and is generated in proportion to the error signal, the derivative of the error signal, and the integral of the error signal [i.e. a proportional, integral and derivative (PID) neural controller]. The control torque is applied with a time delay representing conduction, processing, and muscle activation delays. Variations in the PID parameters and the time delay generate variations in SDFs that mimic real experimental SDFs. This model analysis allows one to interpret experimentally observed changes in SDFs in terms of variations in neural controller and time delay parameters rather than in terms of open-loop versus closed-loop behavior.

Dynamic Determinants of the Uncontrolled Manifold during Human Quiet Stance

PubMed Central

Suzuki, Yasuyuki; Morimoto, Hiroki; Kiyono, Ken; Morasso, Pietro G.; Nomura, Taishin

2016-01-01

Human postural sway during stance arises from coordinated multi-joint movements. Thus, a sway trajectory represented by a time-varying postural vector in the multiple-joint-angle-space tends to be constrained to a low-dimensional subspace. It has been proposed that the subspace corresponds to a manifold defined by a kinematic constraint, such that the position of the center of mass (CoM) of the whole body is constant in time, referred to as the kinematic uncontrolled manifold (kinematic-UCM). A control strategy related to this hypothesis (CoM-control-strategy) claims that the central nervous system (CNS) aims to keep the posture close to the kinematic-UCM using a continuous feedback controller, leading to sway patterns that mostly occur within the kinematic-UCM, where no corrective control is exerted. An alternative strategy proposed by the authors (intermittent control-strategy) claims that the CNS stabilizes posture by intermittently suspending the active feedback controller, in such a way to allow the CNS to exploit a stable manifold of the saddle-type upright equilibrium in the state-space of the system, referred to as the dynamic-UCM, when the state point is on or near the manifold. Although the mathematical definitions of the kinematic- and dynamic-UCM are completely different, both UCMs play similar roles in the stabilization of multi-joint upright posture. The purpose of this study was to compare the dynamic performance of the two control strategies. In particular, we considered a double-inverted-pendulum-model of postural control, and analyzed the two UCMs defined above. We first showed that the geometric configurations of the two UCMs are almost identical. We then investigated whether the UCM-component of experimental sway could be considered as passive dynamics with no active control, and showed that such UCM-component mainly consists of high frequency oscillations above 1 Hz, corresponding to anti-phase coordination between the ankle and hip. We also showed that this result can be better characterized by an eigenfrequency associated with the dynamic-UCM. In summary, our analysis highlights the close relationship between the two control strategies, namely their ability to simultaneously establish small CoM variations and postural stability, but also make it clear that the intermittent control hypothesis better explains the spectral characteristics of sway. PMID:27999535

Dynamic Determinants of the Uncontrolled Manifold during Human Quiet Stance.

PubMed

Suzuki, Yasuyuki; Morimoto, Hiroki; Kiyono, Ken; Morasso, Pietro G; Nomura, Taishin

2016-01-01

Human postural sway during stance arises from coordinated multi-joint movements. Thus, a sway trajectory represented by a time-varying postural vector in the multiple-joint-angle-space tends to be constrained to a low-dimensional subspace. It has been proposed that the subspace corresponds to a manifold defined by a kinematic constraint, such that the position of the center of mass (CoM) of the whole body is constant in time, referred to as the kinematic uncontrolled manifold ( kinematic-UCM ). A control strategy related to this hypothesis ( CoM-control-strategy ) claims that the central nervous system (CNS) aims to keep the posture close to the kinematic-UCM using a continuous feedback controller, leading to sway patterns that mostly occur within the kinematic-UCM, where no corrective control is exerted. An alternative strategy proposed by the authors ( intermittent control-strategy ) claims that the CNS stabilizes posture by intermittently suspending the active feedback controller, in such a way to allow the CNS to exploit a stable manifold of the saddle-type upright equilibrium in the state-space of the system, referred to as the dynamic-UCM , when the state point is on or near the manifold. Although the mathematical definitions of the kinematic- and dynamic-UCM are completely different, both UCMs play similar roles in the stabilization of multi-joint upright posture. The purpose of this study was to compare the dynamic performance of the two control strategies. In particular, we considered a double-inverted-pendulum-model of postural control, and analyzed the two UCMs defined above. We first showed that the geometric configurations of the two UCMs are almost identical. We then investigated whether the UCM-component of experimental sway could be considered as passive dynamics with no active control, and showed that such UCM-component mainly consists of high frequency oscillations above 1 Hz, corresponding to anti-phase coordination between the ankle and hip. We also showed that this result can be better characterized by an eigenfrequency associated with the dynamic-UCM. In summary, our analysis highlights the close relationship between the two control strategies, namely their ability to simultaneously establish small CoM variations and postural stability, but also make it clear that the intermittent control hypothesis better explains the spectral characteristics of sway.

Assessing Somatosensory Utilization during Unipedal Postural Control.

PubMed

Goel, Rahul; De Dios, Yiri E; Gadd, Nichole E; Caldwell, Erin E; Peters, Brian T; Reschke, Millard F; Bloomberg, Jacob J; Oddsson, Lars I E; Mulavara, Ajitkumar P

2017-01-01

Multisensory-visual, vestibular and somatosensory information is integrated for appropriate postural control. The primary goal of this study was to assess somatosensory utilization during a functional motor task of unipedal postural control, in normal healthy adults. Assessing individual bias in the utilization of individual sensory contributions during postural control may help customization of rehabilitation protocols. In this study, a test paradigm of unipedal stance control in supine orientation with and without vision was assessed. Postural control in this test paradigm was hypothesized to utilize predominantly contributions of somatosensory information from the feet and ankle joint, with minimal vestibular input. Fourteen healthy subjects "stood" supine on their dominant leg while strapped to a backpack frame that was freely moving on air-bearings, to remove available otolith tilt cues with respect to gravity that influences postural control when standing upright. The backpack was attached through a cable to a pneumatic cylinder that provided a gravity-like load. Subjects performed three trials each with Eyes-open (EO) and Eyes-closed (EC) while loaded with 60% body weight. There was no difference in unipedal stance time (UST) across the two conditions with EC condition challenging the postural control system greater than the EO condition. Stabilogram-diffusion analysis (SDA) indicated that the critical mean square displacement was significantly different between the two conditions. Vestibular cues, both in terms of magnitude and the duration for which relevant information was available for postural control in this test paradigm, were minimized. These results support our hypothesis that maintaining unipedal stance in supine orientation without vision, minimizes vestibular contribution and thus predominantly utilizes somatosensory information for postural control.

Assessing Somatosensory Utilization during Unipedal Postural Control

PubMed Central

Goel, Rahul; De Dios, Yiri E.; Gadd, Nichole E.; Caldwell, Erin E.; Peters, Brian T.; Reschke, Millard F.; Bloomberg, Jacob J.; Oddsson, Lars I. E.; Mulavara, Ajitkumar P.

2017-01-01

Multisensory—visual, vestibular and somatosensory information is integrated for appropriate postural control. The primary goal of this study was to assess somatosensory utilization during a functional motor task of unipedal postural control, in normal healthy adults. Assessing individual bias in the utilization of individual sensory contributions during postural control may help customization of rehabilitation protocols. In this study, a test paradigm of unipedal stance control in supine orientation with and without vision was assessed. Postural control in this test paradigm was hypothesized to utilize predominantly contributions of somatosensory information from the feet and ankle joint, with minimal vestibular input. Fourteen healthy subjects “stood” supine on their dominant leg while strapped to a backpack frame that was freely moving on air-bearings, to remove available otolith tilt cues with respect to gravity that influences postural control when standing upright. The backpack was attached through a cable to a pneumatic cylinder that provided a gravity-like load. Subjects performed three trials each with Eyes-open (EO) and Eyes-closed (EC) while loaded with 60% body weight. There was no difference in unipedal stance time (UST) across the two conditions with EC condition challenging the postural control system greater than the EO condition. Stabilogram-diffusion analysis (SDA) indicated that the critical mean square displacement was significantly different between the two conditions. Vestibular cues, both in terms of magnitude and the duration for which relevant information was available for postural control in this test paradigm, were minimized. These results support our hypothesis that maintaining unipedal stance in supine orientation without vision, minimizes vestibular contribution and thus predominantly utilizes somatosensory information for postural control. PMID:28443004

Rambling and trembling in response to body loading.

PubMed

Tahayor, Behdad; Riley, Zachary A; Mahmoudian, Armaghan; Koceja, David M; Hong, Siang Lee

2012-04-01

Various studies have suggested that postural sway is controlled by at least two subsystems. Rambling-Trembling analysis is a widely accepted methodology to dissociate the signals generated by these two hypothetical subsystems. The core assumption of this method is based on the equilibrium point hypothesis which suggests that the central nervous system preserves upright standing by transiently shifting the center of pressure (COP) from one equilibrium point to another. The trajectory generated by this shifting is referred to as rambling and its difference from the original COP signal is referred to as trembling. In this study we showed that these two components of COP are differentially affected when standing with external loads. Using Detrended Fluctuation analysis, we compared the pattern of these two signals in different configurations of body loading. Our findings suggest that by applying an external load, the dynamics of the trembling component is altered independently of the area of postural sway and also independently of the rambling component. The dynamics of rambling changed only during the backloading condition in which the postural sway area also substantially increased. It can be suggested that during loaded standing, the trembling mechanism (which is suggested to be activated by peripheral mechanisms and reflexes) is altered without affecting the central influence on the shifts of the equilibrium point.

Stance control is not affected by paresis and reflex hyperexcitability: the case of spastic patients

PubMed Central

Nardone, A; Galante, M; Lucas, B; Schieppati, M

2001-01-01

OBJECTIVES—Spastic patients were studied to understand whether stance unsteadiness is associated with changes in the control of voluntary force, muscle tone, or reflex excitability, rather than to abnormal posture connected to the motor deficit itself.
METHODS—Twenty four normal subjects, 12 patients affected by amyotrophic lateral sclerosis (ALS), seven by spastic paraparesis, and 14 by hemiparesis were studied. All patients featured various degrees of spasticity and paresis but were free from clinically evident sensory deficits. Body sway during quiet upright stance was assessed through a stabilometric platform under both eyes open (EO) and eyes closed (EC) conditions. The sudden rotation of a supporting platform, in a toe up and toe down direction respectively, evoked short (SLR) and medium latency (MLR) reflex responses to stretch of the soleus or the tibialis anterior (TA) muscle.
RESULTS—No relation was found between clinical findings (tone, muscle strength, tendon reflexes, plantar response, and duration of disease) and body sway. On average, all patient groups exhibited a forward shift of the centre of foot pressure (CFP) with respect to normal subjects; in addition, paraparetic and to a much larger extent hemiparetic patients showed a lateral shift of CFP. Body sway area was significantly increased only in the hemiparetic patients. No relation was found between position of the CFP and sway within any patient group. Soleus SLR was increased in all patients with respect to normal subjects. TA SLR was often seen in both patients with ALS and paraparetic patients, but only rarely in normal subjects and hemiparetic patients. However, no relation was found between amplitude of soleus or TA SLRs and stabilometric variables. The frequency and size of soleus MLR and TA MLR were decreased in all patients. These responses were decreased in size and not modulated by background EMG in the affected leg of hemiparetic patients, suggesting a disturbed control of spinal reflexes fed by spindle group II afferent fibres.
CONCLUSIONS—It is proposed that body posture, paresis, or monosynaptic reflex hyperexcitability do not affect the control of equilibrium during quiet upright stance. In hemiparetic patients, the decreased amplitude of MLRs might be the main cause of the large postural instability. The results are congruent with the hypothesis of a role for group II afferent input in the reflex control of equilibrium.

 PMID:11309458

Intermittent control with ankle, hip, and mixed strategies during quiet standing: a theoretical proposal based on a double inverted pendulum model.

PubMed

Suzuki, Yasuyuki; Nomura, Taishin; Casadio, Maura; Morasso, Pietro

2012-10-07

Human upright posture, as a mechanical system, is characterized by an instability of saddle type, involving both stable and unstable dynamic modes. The brain stabilizes such system by generating active joint torques, according to a time-delayed neural feedback control. What is still unsolved is a clear understanding of the control strategies and the control mechanisms that are used by the central nervous system in order to stabilize the unstable posture in a robust way while maintaining flexibility. Most studies in this direction have been limited to the single inverted pendulum model, which is useful for formalizing fundamental mechanical aspects but insufficient for addressing more general issues concerning neural control strategies. Here we consider a double inverted pendulum model in the sagittal plane with small passive viscoelasticity at the ankle and hip joints. Despite difficulties in stabilizing the double pendulum model in the presence of the large feedback delay, we show that robust and flexible stabilization of the upright posture can be established by an intermittent control mechanism that achieves the goal of stabilizing the body posture according to a "divide and conquer strategy", which switches among different controllers in different parts of the state space of the double inverted pendulum. Remarkably, it is shown that a global, robust stability is achieved even if the individual controllers are unstable and the information exploited for switching from one controller to another is severely delayed, as it happens in biological reality. Moreover, the intermittent controller can automatically resolve coordination among multiple active torques associated with the muscle synergy, leading to the emergence of distinct temporally coordinated active torque patterns, referred to as the intermittent ankle, hip, and mixed strategies during quiet standing, depending on the passive elasticity at the hip joint. Copyright © 2012 Elsevier Ltd. All rights reserved.

Glaucoma patients demonstrate faulty autoregulation of ocular blood flow during posture change

PubMed Central

Evans, D.; Harris, A.; Garrett, M.; Chung, H. S.; Kagemann, L.

1999-01-01

BACKGROUND/AIMS—Autoregulation of blood flow during posture change is important to ensure consistent organ circulation. The purpose of this study was to compare the change in retrobulbar ocular blood flow in glaucoma patients with normal subjects during supine and upright posture.
METHODS—20 open angle glaucoma patients and 20 normal subjects, similar in age and sex distribution, were evaluated. Blood pressure, intraocular pressure, and retrobulbar blood velocity were tested after 30 minutes of sitting and again after 30 minutes of lying. Retrobulbar haemodynamic measures of peak systolic velocity (PSV), end diastolic velocity (EDV), and resistance index (RI) were obtained in the ophthalmic and central retinal arteries using colour Doppler imaging (CDI).
RESULTS—When changing from the upright to supine posture, normal subjects demonstrated a significant increase in OA EDV (p = 0.016) and significant decrease in OA RI (p = 0.0006) and CRA RI (p = 0.016). Glaucoma patients demonstrated similar changes in OA measures of EDV (p = 0.02) and RI (p = 0.04), but no change in CRA measures.
CONCLUSION—Glaucoma patients exhibit faulty autoregulation of central retinal artery blood flow during posture change.

 PMID:10381668

Improved ambulation and speech production in an adolescent post-traumatic brain injury through a therapeutic intervention to increase postural control.

PubMed

Reinthal, Ann Karas; Mansour, Linda Moeller; Greenwald, Glenna

2004-01-01

This case study examined the effectiveness of a programme designed to improve anticipatory postural control in an adolescent over years 2 and 3 post-traumatic brain injury (TBI). It was hypothesized that her difficulty in walking and talking simultaneously was caused by excessive co-activation of extremity, trunk, and oral musculature during upright activities. The participant was treated weekly by physical and speech therapy. Treatment focussed on improving anticipatory postural control during gross motor activities in conjunction with oral-motor function. Initially, the participant walked using a walker at a speed of 23 cm s(-1). Two years later, she could walk without a device at 53 cm s(-1). Initial laryngoscopic examination showed minimal movement of the velum or pharyngeal walls; full movement was present after treatment. The measure of intelligibility improved from no single word intelligible utterances to 85% intelligible utterances after 2 years. The results suggest that less compensatory rigidification of oral musculature was needed to maintain an upright position against gravity as postural control improved. An adolescent 1-year post-TBI was followed as she underwent additional rehabilitation focussed on improving anticipatory postural control. The functional goal of simultaneously talking while walking was achieved through this intervention.

Comparison of 2 recommendations for adjusting the working height in milking parlors.

PubMed

Jakob, Martina C; Liebers, Falk

2017-08-01

Milking cows is one of the major labor inputs on dairy farms. Modern parlors allow upright working positions, but pain and disorders among parlor workers are still very prevalent. The platform height in the parlors is important for the body posture of the workers. Based on a large set of data containing parlor-specific measures, anthropometrics, and bovimetrics, a simulation of 2 recommendations published in the literature was carried out. This article presents and discusses the results of 2 formulas for determining the appropriate pit depth. The shoulder and body height of the worker and the distance between the udder and the floor influence the adjustment of the pit depth. If work at shoulder level is favored, autotandem parlors offer the most suitable pit depths, whereas side-by-side parlors are too deep in all cases. Due to the variation in anthropometrics and bovimetrics, a good parlor design can reduce the extent of unfavorable body postures, but more technical measures are necessary to completely eliminate them. Actions that reduce the workload and the prevalence of musculoskeletal pain and disorders should be considered. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Human bipedalism and body-mass index.

PubMed

Yi, Su Do; Noh, Jae Dong; Minnhagen, Petter; Song, Mi-Young; Chon, Tae-Soo; Kim, Beom Jun

2017-06-16

Body-mass index, abbreviated as BMI and given by M/H 2 with the mass M and the height H, has been widely used as a useful proxy to measure a general health status of a human individual. We generalise BMI in the form of M/H p and pursue to answer the question of the value of p for populations of animal species including human. We compare values of p for several different datasets for human populations with the ones obtained for other animal populations of fish, whales, and land mammals. All animal populations but humans analyzed in our work are shown to have p ≈ 3 unanimously. In contrast, human populations are different: As young infants grow to become toddlers and keep growing, the sudden change of p is observed at about one year after birth. Infants younger than one year old exhibit significantly larger value of p than two, while children between one and five years old show p ≈ 2, sharply different from other animal species. The observation implies the importance of the upright posture of human individuals. We also propose a simple mechanical model for a human body and suggest that standing and walking upright should put a clear division between bipedal human (p ≈ 2) and other animals (p ≈ 3).

Comparison of form in potential functions while maintaining upright posture during exposure to stereoscopic video clips.

PubMed

Kutsuna, Kenichiro; Matsuura, Yasuyuki; Fujikake, Kazuhiro; Miyao, Masaru; Takada, Hiroki

2013-01-01

Visually induced motion sickness (VIMS) is caused by sensory conflict, the disagreement between vergence and visual accommodation while observing stereoscopic images. VIMS can be measured by psychological and physiological methods. We propose a mathematical methodology to measure the effect of three-dimensional (3D) images on the equilibrium function. In this study, body sway in the resting state is compared with that during exposure to 3D video clips on a liquid crystal display (LCD) and on a head mounted display (HMD). In addition, the Simulator Sickness Questionnaire (SSQ) was completed immediately afterward. Based on the statistical analysis of the SSQ subscores and each index for stabilograms, we succeeded in determining the quantity of the VIMS during exposure to the stereoscopic images. Moreover, we discuss the metamorphism in the potential functions to control the standing posture during the exposure to stereoscopic video clips.

Etiology of lumbar lordosis and its pathophysiology: a review of the evolution of lumbar lordosis, and the mechanics and biology of lumbar degeneration.

PubMed

Sparrey, Carolyn J; Bailey, Jeannie F; Safaee, Michael; Clark, Aaron J; Lafage, Virginie; Schwab, Frank; Smith, Justin S; Ames, Christopher P

2014-05-01

The goal of this review is to discuss the mechanisms of postural degeneration, particularly the loss of lumbar lordosis commonly observed in the elderly in the context of evolution, mechanical, and biological studies of the human spine and to synthesize recent research findings to clinical management of postural malalignment. Lumbar lordosis is unique to the human spine and is necessary to facilitate our upright posture. However, decreased lumbar lordosis and increased thoracic kyphosis are hallmarks of an aging human spinal column. The unique upright posture and lordotic lumbar curvature of the human spine suggest that an understanding of the evolution of the human spinal column, and the unique anatomical features that support lumbar lordosis may provide insight into spine health and degeneration. Considering evolution of the skeleton in isolation from other scientific studies provides a limited picture for clinicians. The evolution and development of human lumbar lordosis highlight the interdependence of pelvic structure and lumbar lordosis. Studies of fossils of human lineage demonstrate a convergence on the degree of lumbar lordosis and the number of lumbar vertebrae in modern Homo sapiens. Evolution and spine mechanics research show that lumbar lordosis is dictated by pelvic incidence, spinal musculature, vertebral wedging, and disc health. The evolution, mechanics, and biology research all point to the importance of spinal posture and flexibility in supporting optimal health. However, surgical management of postural deformity has focused on restoring posture at the expense of flexibility. It is possible that the need for complex and costly spinal fixation can be eliminated by developing tools for early identification of patients at risk for postural deformities through patient history (genetics, mechanics, and environmental exposure) and tracking postural changes over time.

Effect of gravity and microgravity on intracranial pressure

PubMed Central

Lawley, Justin S.; Petersen, Lonnie G.; Howden, Erin J.; Sarma, Satyam; Cornwell, William K.; Zhang, Rong; Whitworth, Louis A.; Williams, Michael A.

2017-01-01

Key Points Astronauts have recently been discovered to have impaired vision, with a presentation that resembles syndromes of elevated intracranial pressure on Earth.Gravity has a profound effect on fluid distribution and pressure within the human circulation. In contrast to prevailing theory, we observed that microgravity reduces central venous and intracranial pressure.This being said, intracranial pressure is not reduced to the levels observed in the 90 deg seated upright posture on Earth. Thus, over 24 h in zero gravity, pressure in the brain is slightly above that observed on Earth, which may explain remodelling of the eye in astronauts. Abstract Astronauts have recently been discovered to have impaired vision, with a presentation that resembles syndromes of elevated intracranial pressure (ICP). This syndrome is considered the most mission‐critical medical problem identified in the past decade of manned spaceflight. We recruited five men and three women who had an Ommaya reservoir inserted for the delivery of prophylactic CNS chemotherapy, but were free of their malignant disease for at least 1 year. ICP was assessed by placing a fluid‐filled 25 gauge butterfly needle into the Ommaya reservoir. Subjects were studied in the upright and supine position, during acute zero gravity (parabolic flight) and prolonged simulated microgravity (6 deg head‐down tilt bedrest). icp was lower when seated in the 90 deg upright posture compared to lying supine (seated, 4 ± 1 vs. supine, 15 ± 2 mmHg). Whilst lying in the supine posture, central venous pressure (supine, 7 ± 3 vs. microgravity, 4 ± 2 mmHg) and ICP (supine, 17 ± 2 vs. microgravity, 13 ± 2 mmHg) were reduced in acute zero gravity, although not to the levels observed in the 90 deg seated upright posture on Earth. Prolonged periods of simulated microgravity did not cause progressive elevations in ICP (supine, 15 ± 2 vs. 24 h head‐down tilt, 15 ± 4 mmHg). Complete removal of gravity does not pathologically elevate ICP but does prevent the normal lowering of ICP when upright. These findings suggest the human brain is protected by the daily circadian cycles in regional ICPs, without which pathology may occur. PMID:28092926

Effect of gravity and microgravity on intracranial pressure.

PubMed

Lawley, Justin S; Petersen, Lonnie G; Howden, Erin J; Sarma, Satyam; Cornwell, William K; Zhang, Rong; Whitworth, Louis A; Williams, Michael A; Levine, Benjamin D

2017-03-15

Astronauts have recently been discovered to have impaired vision, with a presentation that resembles syndromes of elevated intracranial pressure on Earth. Gravity has a profound effect on fluid distribution and pressure within the human circulation. In contrast to prevailing theory, we observed that microgravity reduces central venous and intracranial pressure. This being said, intracranial pressure is not reduced to the levels observed in the 90 deg seated upright posture on Earth. Thus, over 24 h in zero gravity, pressure in the brain is slightly above that observed on Earth, which may explain remodelling of the eye in astronauts. Astronauts have recently been discovered to have impaired vision, with a presentation that resembles syndromes of elevated intracranial pressure (ICP). This syndrome is considered the most mission-critical medical problem identified in the past decade of manned spaceflight. We recruited five men and three women who had an Ommaya reservoir inserted for the delivery of prophylactic CNS chemotherapy, but were free of their malignant disease for at least 1 year. ICP was assessed by placing a fluid-filled 25 gauge butterfly needle into the Ommaya reservoir. Subjects were studied in the upright and supine position, during acute zero gravity (parabolic flight) and prolonged simulated microgravity (6 deg head-down tilt bedrest). ICP was lower when seated in the 90 deg upright posture compared to lying supine (seated, 4 ± 1 vs. supine, 15 ± 2 mmHg). Whilst lying in the supine posture, central venous pressure (supine, 7 ± 3 vs. microgravity, 4 ± 2 mmHg) and ICP (supine, 17 ± 2 vs. microgravity, 13 ± 2 mmHg) were reduced in acute zero gravity, although not to the levels observed in the 90 deg seated upright posture on Earth. Prolonged periods of simulated microgravity did not cause progressive elevations in ICP (supine, 15 ± 2 vs. 24 h head-down tilt, 15 ± 4 mmHg). Complete removal of gravity does not pathologically elevate ICP but does prevent the normal lowering of ICP when upright. These findings suggest the human brain is protected by the daily circadian cycles in regional ICPs, without which pathology may occur. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

Effects of nanotechnologies-based devices on postural control in healthy subjects.

PubMed

Malchiodi Albedi, Giovanna; Corna, Stefano; Aspesi, Valentina; Clerici, Daniela; Parisio, Cinzia; Seitanidis, Jonathan; Cau, Nicola; Brugliera, Luigia; Capodaglio, Paolo

2017-09-05

The aim of the present preliminary randomized controlled study was to ascertain whether the use of newly developed nanotechnologies-based patches can influence posture control of healthy subjects. Thirty healthy female subjects (age 39.4 years, BMI 22.74 kg/m2) were randomly assigned to two groups: one with active patches and a control group with sham patches. Two patches were applied with a tape: one on the subject's sternum and the other on the C7 apophysis. Body sway during quiet upright stance was recorded with a dynamometric platform. Each subject was tested under two visual conditions, eyes open and closed. We used a blocked stratified randomization procedure conducted by a third party. Subjects wearing the sham patches showed a significant increase of the centre of pressure sway area after 4 hours when they performed the habitual moderate-intensity work activities. In the active patch group, a decrease of the sway path was evident, providing evidence of an enhanced balance control. Our preliminary findings on healthy subjects indicate that nanotechnological devices generating ultra-low electromagnetic fields can improve posture control.

Postural responses of head and foot cutaneous microvascular flow and their sensitivity to bed rest

NASA Technical Reports Server (NTRS)

Aratow, Michael; Hargens, Alan R.; Meyer, J.-UWE; Arnaud, Sara B.

1991-01-01

To explore the mechanism for facial puffiness, headache, and nasal congestion associated with microgravity and cephalad fluid shifts, the postural responses of the cutaneous microcirculation (CMC) in the forehead and dorsum of the foot of eight healthy men were studied by changing body position on a tilt table and measuring blood flows with a laser Doppler flowmeter. Increasing arterial pressure in the feet by moving from a -6-deg head-down tilt to a 60-deg head-up posture decreased foot CMC by 46.5 + or - 12.0 percent. Raising arterial pressure in the head increased forehead CMC by 25.5 + or - 0.7 percent (p less than 0.05). To investigate the possibility that these opposite responses could be modified by simulated microgravity, tilt test were repeated after 7 d of -6-deg head-down-tilt bed rest. The responses were not significantly different from those recorded before bed rest. Therefore, CMC in the feet is well regulated to prevent edema when shifting to an upright position, whereas there is less regulation in the head CMC.

Human cerebral venous outflow pathway depends on posture and central venous pressure

PubMed Central

Gisolf, J; van Lieshout, J J; van Heusden, K; Pott, F; Stok, W J; Karemaker, J M

2004-01-01

Internal jugular veins are the major cerebral venous outflow pathway in supine humans. In upright humans the positioning of these veins above heart level causes them to collapse. An alternative cerebral outflow pathway is the vertebral venous plexus. We set out to determine the effect of posture and central venous pressure (CVP) on the distribution of cerebral outflow over the internal jugular veins and the vertebral plexus, using a mathematical model. Input to the model was a data set of beat-to-beat cerebral blood flow velocity and CVP measurements in 10 healthy subjects, during baseline rest and a Valsalva manoeuvre in the supine and standing position. The model, consisting of 2 jugular veins, each a chain of 10 units containing nonlinear resistances and capacitors, and a vertebral plexus containing a resistance, showed blood flow mainly through the internal jugular veins in the supine position, but mainly through the vertebral plexus in the upright position. A Valsalva manoeuvre while standing completely re-opened the jugular veins. Results of ultrasound imaging of the right internal jugular vein cross-sectional area at the level of the laryngeal prominence in six healthy subjects, before and during a Valsalva manoeuvre in both body positions, correlate highly with model simulation of the jugular cross-sectional area (R2 = 0.97). The results suggest that the cerebral venous flow distribution depends on posture and CVP: in supine humans the internal jugular veins are the primary pathway. The internal jugular veins are collapsed in the standing position and blood is shunted to an alternative venous pathway, but a marked increase in CVP while standing completely re-opens the jugular veins. PMID:15284348

Coordination between posture and movement: interaction between postural and accuracy constraints.

PubMed

Berrigan, Félix; Simoneau, Martin; Martin, Olivier; Teasdale, Normand

2006-04-01

We examined the interaction between the control of posture and an aiming movement. Balance control was varied by having subjects aim at a target from a seated or a standing position. The aiming difficulty was varied using a Fitts'-like paradigm (movement amplitude=30 cm; target widths=0.5, 1.0, 2.5 and 5 cm). For both postural conditions, all targets were within the reaching space in front of the subjects and kept at a fixed relative position with respect to the subjects' body. Hence, for a given target size, the aiming was differentiated only by the postural context (seated vs. upright standing). For both postural conditions, movement time (MT) followed the well-known Fitts' law, that is, it increased with a decreasing target size. For the smallest target width, however, the increased MT was greater when subjects were standing than when they were seated suggesting that the difficulty of the aiming task could not be determined solely by the target size. When standing, a coordination between the trunk and the arm was observed. Also, as the target size decreased, the center of pressure (CP) displacement increased without any increase in CP speed suggesting that the subjects were regulating their CP to provide a controlled referential to assist the hand movement. When seated, the CP kinematics was scaled with the hand movement kinematics. Increasing the index of difficulty led to a strong correlation between the hand speed and CP displacement and speed. The complex organization between posture and movement was revealed only by examining the specific interactions between speed-accuracy and postural constraints.

Using impedance cardiography to assess left ventricular systolic function via postural change in patients with heart failure.

PubMed

DeMarzo, Arthur P; Calvin, James E; Kelly, Russell F; Stamos, Thomas D

2005-01-01

For the diagnosis and management of heart failure, it would be useful to have a simple point-of-care test for assessing ventricular function that could be performed by a nurse. An impedance cardiography (ICG) parameter called systolic amplitude (SA) can serve as an indicator of left ventricular systolic function (LVSF). This study tested the hypothesis that patients with normal LVSF should have a significant increase in SA in response to an increase in end-diastolic volume caused by postural change from sitting upright to supine, while patients with depressed LVSF associated with heart failure should have a minimal increase or a decrease in SA from upright to supine. ICG data were obtained in 12 patients without heart disease and with normal LVSF and 18 patients with clinically diagnosed heart failure. Consistent with the hypothesis, patients with normal LVSF had a significant increase in SA from upright to supine, whereas heart failure patients had a minimal increase or a decrease in SA from upright to supine. This ICG procedure may be useful for monitoring the trend of patient response to titration of beta blockers and other medications. ICG potentially could be used to detect worsening LVSF and provide a means of measurement for adjusting treatment.

The Physiology of Bed Rest. Chapter 39

NASA Technical Reports Server (NTRS)

Fortney, Suzanne M.; Schneider, Victor S.; Greenleaf, John E.

1996-01-01

Prolonged rest in bed has been utilized by physicians and other health-care workers to immobilize and confine patients for rehabilitation and restoration of health since time immemorial. The sitting or horizontal position is sought by the body to relieve the strain of the upright or vertical postures, for example during syncopal situations, bone fractures, muscle injuries, fatigue, and probably also to reduce energy expenditure. Most health-care personnel are aware that adaptive responses occurring during bed rest proceed concomitantly with the healing process; signs and symptoms associated with the former should be differentiated from those of the latter. Not all illnesses and infirmities benefit from prolonged bed rest. Considerations in prescribing bed rest for patients-including duration, body position, mode and duration of exercise, light-dark cycles, temperature, and humidity-have not been investigated adequately. More recently, adaptive physiological responses have been measured in normal, healthy subjects in the horizontal or slightly head-down postures during prolonged bed rest as analogs for the adaptive responses of astronauts exposed to the microgravity environment of outer and bed-rest research.

Impairments in central cardiovascular function contribute to attenuated reflex vasodilation in aged skin

PubMed Central

Stanhewicz, Anna E.; Proctor, David N.; Alexander, Lacy M.; Kenney, W. Larry

2015-01-01

During supine passive heating, increases in skin blood flow (SkBF) and cardiac output (Qc) are both blunted in older adults. The aim here was to determine the effect of acutely correcting the peripheral vasodilatory capacity of aged skin on the integrated cardiovascular responses to passive heating. A secondary aim was to examine the SkBF-Qc relation during hyperthermia in the presence (upright posture) and absence (dynamic exercise) of challenges to central venous pressure. We hypothesized that greater increases in SkBF would be accompanied by greater increases in Qc. Eleven healthy older adults (69 ± 3 yr) underwent supine passive heating (0.8°C rise in core temperature; water-perfused suit) after ingesting sapropterin (BH4, a nitric oxide synthase cofactor; 10 mg/kg) or placebo (randomized double-blind crossover design). Twelve young (24 ± 1 yr) subjects served as a comparison group. SkBF (laser-Doppler flowmetry) and Qc (open-circuit acetylene wash-in) were measured during supine heating, heating + upright posture, and heating + dynamic exercise. Throughout supine and upright heating, sapropterin fully restored the SkBF response of older adults to that of young adults but Qc remained blunted. During heat + upright posture, SkBF failed to decrease in untreated older subjects. There were no age- or treatment-related differences in SkBF-Qc during dynamic exercise. The principal finding of this study was that the blunted Qc response to passive heat stress is directly related to age as opposed to the blunted peripheral vasodilatory capacity of aged skin. Furthermore, peripheral impairments to SkBF in the aged may contribute to inapposite responses during challenges to central venous pressure during hyperthermia. PMID:26494450

Reliability of Upright and Supine Power Measurements Using an Inertial Load Cycle Ergometer

NASA Technical Reports Server (NTRS)

Wickwire, P. J.; Leach, M.; Ryder, J.; Ploutz-Snyder, R.; Ploutz-Snyder, L.

2011-01-01

Practical, reliable, and time efficient methods of measuring muscular power are desirable for both research and applied testing situations. The inertial-load cycling method (ILC; Power/Cycle, Austin, TX) requires subjects to pedal as fast as possible against the inertial load of a flywheel for only 3-5 seconds, which could help reduce the time and effort required for maximal power testing. PURPOSE: 1) To test the intramachine reliability of ILC over 3 separate sessions, 2) to compare postural stance (upright vs. supine) during testing, and 3) to compare the maximal power (Pmax) output measured using ILC to that obtained from traditional isokinetic and leg press testing. METHODS: Subjects (n = 12) were tested on 4 non-consecutive days. The following tests were done on the first day of testing: isometric knee extension, isokinetic knee extension at several speeds, isokinetic power/endurance at 180/sec (Biodex System 4), leg press maximal isometric force, and leg press power/endurance. The other 3 days consisted exclusively of ILC testing. Subjects performed 6 ILC tests in an upright position and 6 ILC tests in a supine position on each day. The starting position was counterbalanced. Mixed-effects linear modeling was used to determine if any differences existed between testing days and between upright and supine for Pmax and revolutions per minute at Pmax (RPMpk). Mixed-modeling was also used to calculate intraclass correlation coefficients (ICC) to determine the reliability of the ILC on each testing day for Pmax and RPMpk (ICCs were calculated separately for upright and supine). gKendall fs Tau a h was used to determine the association between ILC Pmax and isokinetic and leg press data. RESULTS: For Pmax, significant differences were found between days 1 and 2 (upright: p = 0.018; supine: p = 0.014) and between days 1 and 3 (upright: p = 0.001; supine: p = 0.002), but not between days 2 and 3 (upright: p = 0.422; supine: p = 0.501). Pmax ICC values were greater than or equal to 0.97 for all days in both positions. Also, no significant differences between upright and supine postures were found for Pmax. No significant differences between days were found for RPMpk; however, there was a significant posture effect (upright greater than supine). Moderate correlations were observed between ILC Pmax and isokinetic and leg press tests (upright: 0.64-0.79, supine: 0.52-0.82). CONCLUSIONS: Overall, ILC is a very reliable test. Since a significant difference was found between day 1 and the other ILC testing days, it is suggested that day 1 of ILC testing should be used as a familiarization session to allow for subject learning. No significant difference in Pmax was seen from test 3 to test 6. However, an increase of 1.3% was observed from test 4 to test 6. Therefore, although 4 tests may be sufficient for most subjects to produce Pmax, in some cases 6 tests may be required. PRACTICAL APPLICATIONS: No differences were seen in Pmax between upright and supine positions despite differing RPMpk. This suggests that ILC testing can be used to provide reliable testing both in an upright position (appropriate for athletes) and in research (e.g., bed rest) or rehabilitation settings where supine testing is necessary. Future research should evaluate whether peak power measurements obtained with the ILC are sensitive to changes such as that observed with training and de-training.

Attentional cueing: fearful body postures capture attention with saccades.

PubMed

Bannerman, Rachel L; Milders, Maarten; Sahraie, Arash

2010-05-01

According to theories of attention and emotion, threat-related stimuli (e.g., negative facial expressions) capture and hold attention. Despite these theories, previous examination of attentional cueing by threat showed no enhanced capture at brief durations. One explanation for the absence of attentional capture effects may be related to the sensitivity of the manual response measure employed. Here we extended beyond facial expressions and investigated the time course of orienting attention towards fearful body postures in the exogenous cueing task. Cue duration (20, 40, 60, or 100 ms), orientation (upright or inverted), and response mode (saccadic eye movement or manual keypress) were manipulated across three experiments. In the saccade mode, both enhanced attentional capture and impaired disengagement from fearful bodies were evident and limited to rapid cue durations (20 and 40 ms), suggesting that saccadic cueing effects emerge rapidly and are short lived. In the manual mode, fearful bodies impacted only upon the disengagement component of attention at 100 ms, suggesting that manual cueing effects emerge over longer periods of time. No cueing modulation was found for inverted presentation, suggesting that valence, not low-level image confounds, was responsible for the cueing effects. Importantly, saccades could reveal threat biases at brief cue durations consistent with current theories of emotion and attention.

The Steps to Perfect Posture

ERIC Educational Resources Information Center

Chappell, Jon

2007-01-01

Many people have memories of being told to "stop slouching" while seated at the piano bench. But the reality is that good piano posture is not as simple as bolting upright on the bench when the teacher barks. According to Eric Sutz, a Chicago-area piano teacher and performer, one should see a natural curve in his/her lower lumbar area and should…

The Posture of "Tyrannosaurus rex": Why Do Student Views Lag behind the Science?

ERIC Educational Resources Information Center

Ross, Robert M.; Duggan-Haas, Don; Allmon, Warren D.

2013-01-01

Today's students were born well after the dramatic scientific reinterpretations of theropod dinosaur stance and metabolism of the late 1960s and early 1970s. Yet, if asked to draw a picture of "Tyrannosaurus rex," most of these students will likely draw an animal with an upright, tail-dragging posture, remarkably like the original 1905…

Control of paraplegic ankle joint stiffness using FES while standing.

PubMed

Hunt, K J; Gollee, H; Jaime, R P

2001-10-01

The goal of this work was to investigate the feasibility of ankle stiffness control using functional electrical stimulation (FES) while standing, as relevant to the development of feedback systems for balance control in paraplegia. The work was carried out using apparatus in which the subject stands with all joints above the ankles braced, and where ankle moment is provided via FES of the ankle flexor and extensor muscles. A feedback control strategy for ankle stiffness control is proposed in which the ankle moment is controlled to a reference value equal to the product of the desired stiffness and the measured ankle angle. Two subjects participated in the study: one neurologically-intact person, and one paraplegic person with a complete thoracic spinal cord lesion. The results show that during forward-leaning postures, when the plantarflexor muscles are stimulated, relatively high ankle moments of up to 60 Nm can be generated and accurate moment tracking is achieved. As a consequence, ankle stiffness is close to the desired value. During backward lean, on the other hand, the dorsiflexor muscles are stimulated. These muscles are relatively weak and only modest ankle moments of up to around 15 Nm can be produced. As a result, dorsiflexor stimulation readily saturates giving poor stiffness control. It was further observed that when the desired stiffness is higher more external force has to be applied to perturb the body away from the neutral (upright) position. We conclude that: (i) accurate ankle stiffness control, up to the fundamental strength limits of the muscles, can be achieved with controlled FES; (ii) ankle stiffness control using FES in paraplegia has the potential to ease the task of stabilising upright posture by application of additional upper-body forces.

Interaction between postural asymmetry and visual feedback effects in undisturbed upright stance control in healthy adults.

PubMed

Rougier, Patrice R; Boudrahem, Samir

2017-09-01

The technique of additional visual feedback has been shown to significantly decrease the center of pressure (CP) displacements of a standing subject. Body-weight asymmetry is known to increase postural instability due to difficulties in coordinating the reaction forces exerted under each foot and is often a cardinal feature of various neurological and traumatic diseases. To examine the possible interactions between additional visual feedback and body-weight asymmetry effects, healthy adults were recruited in a protocol with and without additional visual feedback, with different levels of body-weight asymmetry. CP displacements under each foot were recorded and used to compute the resultant CP displacements (CP Res ) and to estimate vertically projected center of gravity (CG v ) and CP Res -CG v displacements. Overall, six conditions were randomly proposed combining two factors: asymmetry with three BW percentage distributions (50/50, 35/65 and 20/80; left/right leg) and feedback (with or without additional VFB). The additional visual feedback technique principally reduces CG v displacements, whereas asymmetry increases CP Res -CG v displacements along the mediolateral axis. Some effects on plantar CP displacements were also observed, but only under the unloaded foot. Interestingly, no interaction between additional visual feedback and body-weight asymmetry was reported. These results suggest that the various postural effects that ensue from manipulating additional visual feedback parameters, shown previously in healthy subjects in various studies, could also apply independently of the level of asymmetry. Visual feedback effects could be observed in patients presenting weight-bearing asymmetries. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

A rehabilitation tool for functional balance using altered gravity and virtual reality.

PubMed

Oddsson, Lars I E; Karlsson, Robin; Konrad, Janusz; Ince, Serdar; Williams, Steve R; Zemkova, Erika

2007-07-10

There is a need for effective and early functional rehabilitation of patients with gait and balance problems including those with spinal cord injury, neurological diseases and recovering from hip fractures, a common consequence of falls especially in the elderly population. Gait training in these patients using partial body weight support (BWS) on a treadmill, a technique that involves unloading the subject through a harness, improves walking better than training with full weight bearing. One problem with this technique not commonly acknowledged is that the harness provides external support that essentially eliminates associated postural adjustments (APAs) required for independent gait. We have developed a device to address this issue and conducted a training study for proof of concept of efficacy. We present a tool that can enhance the concept of BWS training by allowing natural APAs to occur mediolaterally. While in a supine position in a 90 deg tilted environment built around a modified hospital bed, subjects wear a backpack frame that is freely moving on air-bearings (cf. puck on an air hockey table) and attached through a cable to a pneumatic cylinder that provides a load that can be set to emulate various G-like loads. Veridical visual input is provided through two 3-D automultiscopic displays that allow glasses free 3-D vision representing a virtual surrounding environment that may be acquired from sites chosen by the patient. Two groups of 12 healthy subjects were exposed to either strength training alone or a combination of strength and balance training in such a tilted environment over a period of four weeks. Isokinetic strength measured during upright squat extension improved similarly in both groups. Measures of balance assessed in upright showed statistically significant improvements only when balance was part of the training in the tilted environment. Postural measures indicated less reliance on visual and/or increased use of somatosensory cues after training. Upright balance function can be improved following balance specific training performed in a supine position in an environment providing the perception of an upright position with respect to gravity. Future studies will implement this concept in patients.

Development of a Protocol to Test Proprioceptive Utilization as a Predictor for Sensorimotor Adaptability

NASA Technical Reports Server (NTRS)

Goel, R.; De Dios, Y. E.; Gadd, N. E.; Caldwell, E. E.; Peters, B. T.; Bloomberg, J. J.; Oddsson, L. I. E.; Mulavara, A. P.

2016-01-01

Astronauts returning from space flight show significant inter-subject variations in their abilities to readapt to a gravitational environment because of their innate sensory weighting. The ability to predict the manner and degree to which each individual astronaut will be affected would improve the effectiveness of countermeasure training programs designed to enhance sensorimotor adaptability. We hypothesize participant's ability to utilize individual sensory information (vision, proprioception and vestibular) influences adaptation in sensorimotor performance after space flight. The goal of this study is to develop a reliable protocol to test proprioceptive utilization in a functional postural control task. Subjects "stand" in a supine position while strapped to a backpack frame holding a friction-free device using air-bearings that allow the subject to move freely in the frontal plane, similar to when in upright standing. The frame is attached to a pneumatic cylinder, which can provide different levels of a gravity-like force that the subject must balance against to remain "upright". The supine posture with eyes closed ensures reduced vestibular and visual contribution to postural control suggesting somatosensory and/or non-otolith vestibular inputs will provide relevant information for maintaining balance control in this task. This setup is called the gravity bed. Fourteen healthy subjects carried out three trials each with eyes open alternated with eyes closed, "standing" on their dominant leg in the gravity bed environment while loaded with 60 percent of their body weight. Subjects were instructed to: "use your sense of sway about the ankle and pressure changes under the foot to maintain balance." Maximum length of a trial was 45 seconds. A force plate underneath the foot recorded forces and moments during the trial and an inertial measurement unit (IMU) attached on the backpack's frame near the center of mass of the subject recorded upper body postural responses. Series of linear and non-linear analyses were carried out on several force plate and IMU data including stabilogram diffusion analysis on the center of pressure (COP) to find a subset of parameters that were sensitive to detect differences in postural performance between eyes open and closed conditions. Results revealed that seven parameters (root mean square (RMS) of medio-lateral (ML) COP, range of ML COP, RMS of roll moment, range of trunk roll, minimum time-to-boundary (TTB), integrated TTB, and critical mean square planar displacement (delta r (sup 2) (sub c)) were significantly different between eyes open and closed conditions. We will present data to show the efficacy of using performance in single leg stance with eyes closed on the gravity bed to assess individuals' ability to utilize proprioceptive information in a functional postural control task to predict re-adaptation for sensorimotor and functional performance.

Tai Chi training reduced coupling between respiration and postural control

PubMed Central

Holmes, Matthew L; Manor, Brad; Hsieh, Wan-hsin; Hu, Kun; Lipsitz, Lewis A; Li, Li

2015-01-01

In order to maintain stable upright stance, the postural control system must account for the continuous perturbations to the body’s center-of-mass including those caused by spontaneous respiration. Both aging and disease increase “posturo-respiratory synchronization;” which reflects the degree to which respiration affects postural sway fluctuations over time. Tai Chi training emphasizes the coordination of respiration and bodily movements and may therefore optimize the functional interaction between these two systems. The purpose of the project was to examine the effect of Tai Chi training on the interaction between respiration and postural control in older adults. We hypothesized that Tai Chi training would improve the ability of the postural control system to compensate for respiratory perturbations and thus, reduce posturo-respiratory synchronization. Participants were recruited from supportive housing facilities and randomized to a 12-week Tai Chi intervention (n=28; 86±5yrs) or educational-control program (n=34, 85±6yrs). Standing postural sway and respiration were simultaneously recorded with a force plate and respiratory belt under eyes-open and eyes-closed conditions. Posturo-respiratory synchronization was determined by quantifying the variation of the phase relationship between the dominant oscillatory mode of respiration and corresponding oscillations within postural sway. Groups were similar in age, gender distribution, height, body mass, and intervention compliance. Neither intervention altered average sway speed, sway magnitude or respiratory rate. As compared to the education-control group, however, Tai Chi training reduced posturo-respiratory synchronization when standing with eyes open or closed (p<0.001). Tai Chi training did not affect traditional parameters of standing postural control or respiration, yet reduced the coupling between respiration and postural control. The beneficial effects of Tai Chi training may therefore stem in part from optimization of this multi-system interaction. PMID:26518241

Decreasing internal focus of attention improves postural control during quiet standing in young healthy adults.

PubMed

Nafati, Gilel; Vuillerme, Nicolas

2011-12-01

This experiment was designed to investigate whether and how decreasing the amount of attentional focus invested in postural control could affect bipedal postural control. Twelve participants were asked to stand upright as immobile as possible on a force platform in one control condition and one cognitive condition. In the latter condition, they performed a short-term digit-span memory task. Decreased center-of-gravity displacements and decreased center-of-foot-pressure displacements minus center-of-gravity displacements were observed in the cognitive condition relative to the control condition. These results suggest that shifting the attentional focus away from postural control by executing a concurrent attention-demanding task could increase postural performance and postural efficiency.

Weight-Bearing MR Imaging as an Option in the Study of Gravitational Effects on the Vocal Tract of Untrained Subjects in Singing Phonation

PubMed Central

Traser, Louisa; Burdumy, Michael; Richter, Bernhard; Vicari, Marco; Echternach, Matthias

2014-01-01

Magnetic Resonance Imaging (MRI) of subjects in a supine position can be used to evaluate the configuration of the vocal tract during phonation. However, studies of speech phonation have shown that gravity can affect vocal tract shape and bias measurements. This is one of the reasons that MRI studies of singing phonation have used professionally trained singers as subjects, because they are generally considered to be less affected by the supine body position and environmental distractions. A study of untrained singers might not only contribute to the understanding of intuitive singing function and aid the evaluation of potential hazards for vocal health, but also provide insights into the effect of the supine position on singers in general. In the present study, an open configuration 0.25 T MRI system with a rotatable examination bed was used to study the effect of body position in 20 vocally untrained subjects. The subjects were asked to sing sustained tones in both supine and upright body positions on different pitches and in different register conditions. Morphometric measurements were taken from the acquired images of a sagittal slice depicting the vocal tract. The analysis concerning the vocal tract configuration in the two body positions revealed differences in 5 out of 10 measured articulatory parameters. In the upright position the jaw was less protruded, the uvula was elongated, the larynx more tilted and the tongue was positioned more to the front of the mouth than in the supine position. The findings presented are in agreement with several studies on gravitational effects in speech phonation, but contrast with the results of a previous study on professional singers of our group where only minor differences between upright and supine body posture were observed. The present study demonstrates that imaging of the vocal tract using weight-bearing MR imaging is a feasible tool for the study of sustained phonation in singing for vocally untrained subjects. PMID:25379885

Weight-bearing MR imaging as an option in the study of gravitational effects on the vocal tract of untrained subjects in singing phonation.

PubMed

Traser, Louisa; Burdumy, Michael; Richter, Bernhard; Vicari, Marco; Echternach, Matthias

2014-01-01

Magnetic Resonance Imaging (MRI) of subjects in a supine position can be used to evaluate the configuration of the vocal tract during phonation. However, studies of speech phonation have shown that gravity can affect vocal tract shape and bias measurements. This is one of the reasons that MRI studies of singing phonation have used professionally trained singers as subjects, because they are generally considered to be less affected by the supine body position and environmental distractions. A study of untrained singers might not only contribute to the understanding of intuitive singing function and aid the evaluation of potential hazards for vocal health, but also provide insights into the effect of the supine position on singers in general. In the present study, an open configuration 0.25 T MRI system with a rotatable examination bed was used to study the effect of body position in 20 vocally untrained subjects. The subjects were asked to sing sustained tones in both supine and upright body positions on different pitches and in different register conditions. Morphometric measurements were taken from the acquired images of a sagittal slice depicting the vocal tract. The analysis concerning the vocal tract configuration in the two body positions revealed differences in 5 out of 10 measured articulatory parameters. In the upright position the jaw was less protruded, the uvula was elongated, the larynx more tilted and the tongue was positioned more to the front of the mouth than in the supine position. The findings presented are in agreement with several studies on gravitational effects in speech phonation, but contrast with the results of a previous study on professional singers of our group where only minor differences between upright and supine body posture were observed. The present study demonstrates that imaging of the vocal tract using weight-bearing MR imaging is a feasible tool for the study of sustained phonation in singing for vocally untrained subjects.

Effects of Changing Body Weight Distribution on Mediolateral Stability Control during Gait Initiation

PubMed Central

Caderby, Teddy; Yiou, Eric; Peyrot, Nicolas; de Viviés, Xavier; Bonazzi, Bruno; Dalleau, Georges

2017-01-01

During gait initiation, anticipatory postural adjustments (APA) precede the execution of the first step. It is generally acknowledged that these APA contribute to forward progression but also serve to stabilize the whole body in the mediolateral direction during step execution. Although previous studies have shown that changes in the distribution of body weight between both legs influence motor performance during gait initiation, it is not known whether and how such changes affect a person’s postural stability during this task. The aim of this study was to investigate the effects of changing initial body weight distribution between legs on mediolateral postural stability during gait initiation. Changes in body weight distribution were induced under experimental conditions by modifying the frontal plane distribution of an external load located at the participants’ waists. Fifteen healthy adults performed a gait initiation series at a similar speed under three conditions: with the overload evenly distributed over both legs; with the overload strictly distributed over the swing-limb side; and with the overload strictly distributed over the stance-leg side. Our results showed that the mediolateral location of center-of-mass (CoM) during the initial upright posture differed between the experimental conditions, indicating modifications in the initial distribution of body weight between the legs according to the load distribution. While the parameters related to the forward progression remained unchanged, the alterations in body weight distribution elicited adaptive changes in the amplitude of APA in the mediolateral direction (i.e., maximal mediolateral shift of the center of pressure (CoP)), without variation in their duration. Specifically, it was observed that the amplitude of APA was modulated in such a way that mediolateral dynamic stability at swing foot-contact, quantified by the margin of stability (i.e., the distance between the base of support boundary and the extrapolated CoM position), did not vary between the conditions. These findings suggest that APA seem to be scaled as a function of the initial body weight distribution between both legs so as to maintain optimal conditions of stability during gait initiation. PMID:28396629

Mental rotation of letters, body parts and scenes during whole-body tilt: role of a body-centered versus a gravitational reference frame.

PubMed

Bock, Otmar L; Dalecki, Marc

2015-04-01

It is known that in mental-rotation tasks, subjects mentally transform the displayed material until it appears "upright" and then make a judgment. Here we evaluate, by using three typical mental rotation tasks with different degrees of embodiment, whether "upright" is coded to a gravitational or egocentric reference frame, or a combination of both. Observers stood erect or were whole-body tilted by 60°, with their left ear down. In either posture, they saw stimuli presented at different orientation angles in their frontal plane: in condition LETTER, they judged whether the stimuli were normal or mirror-reversed letters, in condition HAND whether they represented a left or a right hand, and in condition SCENE whether a weapon laid left or right in front of a displayed person. Data confirm that reaction times are modulated by stimulus orientation angle, and the modulation curve in LETTER and HAND differs from that in SCENE. More importantly, during 60° body tilt, the modulation curve shifted 12° away from the gravitational towards the egocentric vertical reference; this shift was comparable in all three conditions and independent of the degree of embodiment. We conclude that mental rotation in all conditions relied on a similar spatial reference, which seems to be a weighted average of the gravitational and the egocentric vertical, with a higher weight given to the former. Copyright © 2015 Elsevier B.V. All rights reserved.

Assisting People with Multiple Disabilities by Actively Keeping the Head in an Upright Position with a Nintendo Wii Remote Controller through the Control of an Environmental Stimulation

ERIC Educational Resources Information Center

Shih, Ching-Hsiang; Shih, Chia-Ju; Shih, Ching-Tien

2011-01-01

The latest researches have adopted software technology by applying the Nintendo Wii Remote Controller to the correction of hyperactive limb behavior. This study extended Wii Remote Controller functionality for improper head position (posture) correction (i.e. actively adjusting abnormal head posture) to assess whether two people with multiple…

An active balance board system with real-time control of stiffness and time-delay to assess mechanisms of postural stability.

PubMed

Cruise, Denise R; Chagdes, James R; Liddy, Joshua J; Rietdyk, Shirley; Haddad, Jeffrey M; Zelaznik, Howard N; Raman, Arvind

2017-07-26

Increased time-delay in the neuromuscular system caused by neurological disorders, concussions, or advancing age is an important factor contributing to balance loss (Chagdes et al., 2013, 2016a,b). We present the design and fabrication of an active balance board system that allows for a systematic study of stiffness and time-delay induced instabilities in standing posture. Although current commercial balance boards allow for variable stiffness, they do not allow for manipulation of time-delay. Having two controllable parameters can more accurately determine the cause of balance deficiencies, and allows us to induce instabilities even in healthy populations. An inverted pendulum model of human posture on such an active balance board predicts that reduced board rotational stiffness destabilizes upright posture through board tipping, and limit cycle oscillations about the upright position emerge as feedback time-delay is increased. We validate these two mechanisms of instability on the designed balance board, showing that rotational stiffness and board time-delay induced the predicted postural instabilities in healthy, young adults. Although current commercial balance boards utilize control of rotational stiffness, real-time control of both stiffness and time-delay on an active balance board is a novel and innovative manipulation to reveal balance deficiencies and potentially improve individualized balance training by targeting multiple dimensions contributing to standing balance. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparison of photon organ and effective dose coefficients for PIMAL stylized phantom in bent positions in standard irradiation geometries.

PubMed

Dewji, Shaheen; Reed, K Lisa; Hiller, Mauritius

2017-08-01

Computational phantoms with articulated arms and legs have been constructed to enable the estimation of radiation dose in different postures. Through a graphical user interface, the Phantom wIth Moving Arms and Legs (PIMAL) version 4.1.0 software can be employed to articulate the posture of a phantom and generate a corresponding input deck for the Monte Carlo N-Particle (MCNP) radiation transport code. In this work, photon fluence-to-dose coefficients were computed using PIMAL to compare organ and effective doses for a stylized phantom in the standard upright position with those for phantoms in realistic work postures. The articulated phantoms represent working positions including fully and half bent torsos with extended arms for both the male and female reference adults. Dose coefficients are compared for both the upright and bent positions across monoenergetic photon energies: 0.05, 0.1, 0.5, 1.0, and 5.0 MeV. Additionally, the organ doses are compared across the International Commission on Radiological Protection's standard external radiation exposure geometries: antero-posterior, postero-anterior, left and right lateral, and isotropic (AP, PA, LLAT, RLAT, and ISO). For the AP and PA irradiation geometries, differences in organ doses compared to the upright phantom become more profound with increasing bending angles and have doses largely overestimated for all organs except the brain in AP and bladder in PA. In LLAT and RLAT irradiation geometries, energy deposition for organs is more likely to be underestimated compared to the upright phantom, with no overall change despite increased bending angle. The ISO source geometry did not cause a significant difference in absorbed organ dose between the different phantoms, regardless of position. Organ and effective fluence-to-dose coefficients are tabulated. In the AP geometry, the effective dose at the 45° bent position is overestimated compared to the upright phantom below 1 MeV by as much as 27% and 82% in the 90° position. The effective dose in the 45° bent position was comparable to that in the 90° bent position for the LLAT and RLAT irradiation geometries. However, the upright phantom underestimates the effective dose to PIMAL in the LLAT and RLAT geometries by as much as 30% at 50 keV.

Three-flat test with plates in horizontal posture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vannoni, Maurizio; Molesini, Giuseppe

2008-04-20

Measuring flats in the horizontal posture with interferometers is analyzed in detail, taking into account the sag produced by gravity. A mathematical expression of the bending is provided for a plate supported at three unevenly spaced locations along the edge. It is shown that the azimuthal terms of the deformation can be recovered from a three-flat measuring procedure, while the pure radial terms can only be estimated. The effectiveness of the iterative algorithm for data processing is also demonstrated. Experimental comparison on a set of three flats in horizontal and upright posture is provided.

Effect of upright tilt on ventricular/vascular coupling in chronically instrumented primates

NASA Technical Reports Server (NTRS)

Tran, C. C.; Latham, R. D.; Self, D. A.; Fanton, J. W.; White, C. D.; Owens, R. W.

1993-01-01

Studies of the hydraulic loading conditions on the heart in humans, especially pulsatile load, have primarily been limited to the supine state. Therefore, we have chosen a nonhuman primate model, the baboon, to assess left ventricular/vascular coupling in both supine and upright positions. Primate subjects were studied by catheterization under sedation and then after surgical implantation of transducers. This allowed the evaluation of postural stress in the chronically instrumented conscious baboon and then after light dissociative doses of ketamine. Basic hemodynamic variables were evaluated for baboons in supine and upright positions. Fourier analysis was applied to aortic pressure and flow to obtain input and characteristic impedance and the ratio of pulsatile (Wp) to total (Wt) left ventricular power (Wp/Wt). The aortic reflected, or backward, pressure was also calculated. Peripheral resistance increased (P = 0.01) and reflected pressure decreased (17.74 +/- 1.50 vs. 15.21 +/- 2 mmHg; P < 0.01) in upright subjects. Characteristic impedance and Wp/Wt were unchanged. Postoperatively, peripheral resistance increased (2,651 +/- 311 vs. 3,667 +/- 276; P < 0.05) and mean power and Wt decreased (P < 0.01) without changes in reflected pressure. All variables were unchanged after light dissociative doses of ketamine. Thus there is no significant change in efficiency of left ventricular/vascular coupling formulated in terms of Wp/Wt or input impedance with postural stress.

Clinical, Biomechanical, and Physiological Translational Interpretations of Human Resting Myofascial Tone or Tension

PubMed Central

Masi, Alfonse T.; Nair, Kalyani; Evans, Tyler; Ghandour, Yousef

2010-01-01

Background Myofascial tissues generate integrated webs and networks of passive and active tensional forces that provide stabilizing support and that control movement in the body. Passive [central nervous system (CNS)–independent] resting myofascial tension is present in the body and provides a low-level stabilizing component to help maintain balanced postures. This property was recently called “human resting myofascial tone” (HRMT). The HRMT model evolved from electromyography (EMG) research in the 1950s that showed lumbar muscles usually to be EMG-silent in relaxed gravity-neutral upright postures. Methods Biomechanical, clinical, and physiological studies were reviewed to interpret the passive stiffness properties of HRMT that help to stabilize various relaxed functions such as quiet balanced standing. Biomechanical analyses and experimental studies of the lumbar multifidus were reviewed to interpret its passive stiffness properties. The lumbar multifidus was illustrated as the major core stabilizing muscle of the spine, serving an important passive biomechanical role in the body. Results Research into muscle physiology suggests that passive resting tension (CNS-independent) is generated in sarcomeres by the molecular elasticity of low-level cycling cross-bridges between the actomyosin filaments. In turn, tension is complexly transmitted to intimately enveloping fascial matrix fibrils and other molecular elements in connective tissue, which, collectively, constitute the myofascial unit. Postural myofascial tonus varies with age and sex. Also, individuals in the population are proposed to vary in a polymorphism of postural HRMT. A few people are expected to have outlier degrees of innate postural hypotonicity or hypertonicity. Such biomechanical variations likely predispose to greater risk of related musculoskeletal disorders, a situation that deserves greater attention in clinical practice and research. Axial myofascial hypertonicity was hypothesized to predispose to ankylosing spondylitis. This often-progressive deforming condition of vertebrae and sacroiliac joints is characterized by stiffness features and particular localization of bony lesions at entheseal sites. Such unique features imply concentrations and transmissions of excessive force, leading to tissue micro-injury and maladaptive repair reactions. Conclusions The HRMT model is now expanded and translated for clinical relevance to therapists. Its passive role in helping to maintain balanced postures is supported by biomechanical principles of myofascial elasticity, tension, stress, stiffness, and tensegrity. Further research is needed to determine the molecular basis of HRMT in sarcomeres, the transmission of tension by the enveloping fascial elements, and the means by which the myofascia helps to maintain efficient passive postural balance in the body. Significant deficiencies or excesses of postural HRMT may predispose to symptomatic or pathologic musculoskeletal disorders whose mechanisms are currently unexplained. PMID:21589685

Higher order balance control: Distinct effects between cognitive task and manual steadiness constraint on automatic postural responses.

PubMed

Coelho, Daniel Boari; Bourlinova, Catarina; Teixeira, Luis Augusto

2016-12-01

In the present experiment, we aimed to evaluate the interactive effect of performing a cognitive task simultaneously with a manual task requiring either high or low steadiness on APRs. Young volunteers performed the task of recovering upright balance following a mechanical perturbation provoked by unanticipatedly releasing a load pulling the participant's body backwards. The postural task was performed while holding a cylinder steadily on a tray. One group performed that task under high (cylinder' round side down) and another one under low (cylinder' flat side down) manual steadiness constraint. Those tasks were evaluated in the conditions of performing concurrently a cognitive numeric subtraction task and under no cognitive task. Analysis showed that performance of the cognitive task led to increased body and tray displacement, associated with higher displacement at the hip and upper trunk, and lower magnitude of activation of the GM muscle in response to the perturbation. Conversely, high manual steadiness constraint led to reduced tray velocity in association with lower values of trunk displacement, and decreased rotation amplitude at the ankle and hip joints. We found no interactions between the effects of the cognitive and manual tasks on APRs, suggesting that they were processed in parallel in the generation of responses for balance recovery. Modulation of postural responses from the manual and cognitive tasks indicates participation of higher order neural structures in the generation of APRs, with postural responses being affected by multiple mental processes occurring in parallel. Copyright © 2016 Elsevier B.V. All rights reserved.

A systematic review of the relationship between physical activities in sports or daily life and postural sway in upright stance.

PubMed

Kiers, Henri; van Dieën, Jaap; Dekkers, Henk; Wittink, Harriët; Vanhees, Luc

2013-11-01

In many sports, maintaining balance is necessary to compete at a high level. Also, in many health problems, balance is impaired. Postural sway (PS) is often used as an indicator of upright balance control, and physical activity (PA) might enhance balance control. However, the relationship between PS and PA has never been systematically reviewed. Our objective was to summarize the evidence regarding the relationship between PS in upright bipedal and unipedal standing and PA. We conducted a literature search in MEDLINE, EmBase, CINAHL, the Cochrane Database, and PEDro, up to March 2012, with no limit on the starting date. Characteristics and methodological aspects of each article were extracted by two reviewers. We used centre of pressure (CoP) velocity, and variables related to the CoP area, to compare studies. A total of 39 articles were reviewed from an initial yield of 2,058. Of these 39 studies, 37 used a comparative design, one was a cohort study, and one was a randomized controlled trial. The main conclusion was that in general, sport practitioners sway less than controls, and high-level athletes sway less than low-level athletes. Additionally, we identified specific effects dependent on the use of vision, sport-specific postures, and frequency and duration of the (sports) activity. PS in unperturbed bipedal stance appears to have limited sensitivity to detect subtle differences between groups of healthy people.

Foot force direction control during a pedaling task in individuals post-stroke

PubMed Central

2014-01-01

Background Appropriate magnitude and directional control of foot-forces is required for successful execution of locomotor tasks. Earlier evidence suggested, following stroke, there is a potential impairment in foot-force control capabilities both during stationary force generation and locomotion. The purpose of this study was to investigate the foot-pedal surface interaction force components, in non-neurologically-impaired and stroke-impaired individuals, in order to determine how fore/aft shear-directed foot/pedal forces are controlled. Methods Sixteen individuals with chronic post-stroke hemiplegia and 10 age-similar non-neurologically-impaired controls performed a foot placement maintenance task under a stationary and a pedaling condition, achieving a target normal pedal force. Electromyography and force profiles were recorded. We expected generation of unduly large magnitude shear pedal forces and reduced participation of multiple muscles that can contribute forces in appropriate directions in individuals post-stroke. Results We found lower force output, inconsistent modulation of muscle activity and reduced ability to change foot force direction in the paretic limbs, but we did not observe unduly large magnitude shear pedal surface forces by the paretic limbs as we hypothesized. Conclusion These findings suggested the preservation of foot-force control capabilities post-stroke under minimal upright postural control requirements. Further research must be conducted to determine whether inappropriate shear force generation will be revealed under non-seated, postural demanding conditions, where subjects have to actively control for upright body suspension. PMID:24739234

Postural hypocapnic hyperventilation is associated with enhanced peripheral vasoconstriction in postural tachycardia syndrome with normal supine blood flow

PubMed Central

Stewart, Julian M.; Medow, Marvin S.; Cherniack, Neil S.; Natelson, Benjamin H.

2015-01-01

Previous investigations have demonstrated a subset of postural tachycardia syndrome (POTS) patients characterized by normal peripheral resistance and blood volume while supine but thoracic hypovolemia and splanchnic blood pooling while upright secondary to splanchnic hyperemia. Such “normal-flow” POTS patients often demonstrate hypocapnia during orthostatic stress. We studied 20 POTS patients (14–23 yr of age) and compared them with 10 comparably aged healthy volunteers. We measured changes in heart rate, blood pressure, heart rate and blood pressure variability, arm and leg strain-gauge occlusion plethysmography, respiratory impedance plethysmography calibrated against pneumotachography, end-tidal partial pressure of carbon dioxide (PetCO2), and impedance plethysmographic indexes of blood volume and blood flow within the thoracic, splanchnic, pelvic (upper leg), and lower leg regional circulations while supine and during upright tilt to 70°. Ten POTS patients demonstrated significant hyperventilation and hypocapnia (POTSHC) while 10 were normocapnic with minimal increase in postural ventilation, comparable to control. While relative splanchnic hypervolemia and hyperemia occurred in both POTS groups compared with controls, marked enhancement in peripheral vasoconstriction occurred only in POTSHC and was related to thoracic blood flow. Variability indexes suggested enhanced sympathetic activation in POTSHC compared with other subjects. The data suggest enhanced cardiac and peripheral sympathetic excitation in POTSHC. PMID:16565300

Dynamic genetic linkage of intermediate blood pressure phenotypes during postural adaptations in a founder population

PubMed Central

Arenas, I. A.; Tremblay, J.; Deslauriers, B.; Sandoval, J.; Šeda, O.; Gaudet, D.; Merlo, E.; Kotchen, T.; Cowley, A. W.

2013-01-01

Blood pressure (BP) is a dynamic phenotype that varies rapidly to adjust to changing environmental conditions. Standing upright is a recent evolutionary trait, and genetic factors that influence postural adaptations may contribute to BP variability. We studied the effect of posture on the genetics of BP and intermediate BP phenotypes. We included 384 sib-pairs in 64 sib-ships from families ascertained by early-onset hypertension and dyslipidemia. Blood pressure, three hemodynamic and seven neuroendocrine intermediate BP phenotypes were measured with subjects lying supine and standing upright. The effect of posture on estimates of heritability and genetic covariance was investigated in full pedigrees. Linkage was conducted on 196 candidate genes by sib-pair analyses, and empirical estimates of significance were obtained. A permutation algorithm was implemented to study the postural effect on linkage. ADRA1A, APO, CAST, CORIN, CRHR1, EDNRB, FGF2, GC, GJA1, KCNB2, MMP3, NPY, NR3C2, PLN, TGFBR2, TNFRSF6, and TRHR showed evidence of linkage with any phenotype in the supine position and not upon standing, whereas AKR1B1, CD36, EDNRA, F5, MMP9, PKD2, PON1, PPARG, PPARGC1A, PRKCA, and RET were specifically linked to standing phenotypes. Genetic profiling was undertaken to show genetic interactions among intermediate BP phenotypes and genes specific to each posture. When investigators perform genetic studies exclusively on a single posture, important genetic components of BP are missed. Supine and standing BPs have distinct genetic signatures. Standardized maneuvers influence the results of genetic investigations into BP, thus reflecting its dynamic regulation. PMID:23269701

Modulation of weight off-loading level over body-weight supported locomotion training.

PubMed

Wang, Ping; Low, K H; Lim, Peter A C; McGregor, A H

2011-01-01

With the evolution of robotic systems to facilitate overground walking rehabilitation, it is important to understand the effect of robotic-aided body-weight supported loading on lower limb muscle activity, if we are to optimize neuromotor recovery. To achieve this objective, we have collected and studied electromyography (EMG) data from key muscles in the lower extremity from healthy subjects walking over a wide range of body-weight off-loading levels as provided by a bespoke gait robot. By examining the impact of body-weight off-loading, it was found that muscle activation patterns were sensitive to the level of off-loading. In addition, a large off-loading might introduce disturbance of muscle activation pattern, led to a wider range of motion in terms of dorsiflexion/plantarflexion. Therefore, any future overground training machine should be enhanced to exclude unnecessary effect of body off-loading in securing the sustaining upright posture and providing assist-as-needed BWS over gait rehabilitation. © 2011 IEEE

Altered oscillatory cerebral blood flow velocity and autoregulation in postural tachycardia syndrome.

PubMed

Medow, Marvin S; Del Pozzi, Andrew T; Messer, Zachary R; Terilli, Courtney; Stewart, Julian M

2014-01-01

Decreased upright cerebral blood flow (CBF) with hyperpnea and hypocapnia is seen in a minority of patients with postural tachycardia syndrome (POTS). More often, CBF is not decreased despite upright neurocognitive dysfunction. This may result from time-dependent changes in CBF. We hypothesized that increased oscillations in CBF occurs in POTS (N = 12) compared to healthy controls (N = 9), and tested by measuring CBF velocity (CBFv) by transcranial Doppler ultrasound of the middle cerebral artery, mean arterial pressure (MAP) and related parameters, supine and during 70° upright tilt. Autospectra for mean CBFv and MAP, and transfer function analysis were obtained over the frequency range of 0.0078-0.4 Hz. Upright HR was increased in POTS (125 ± 8 vs. 86 ± 2 bpm), as was diastolic BP (74 ± 3 vs. 65 ± 3 mmHg) compared to control, while peripheral resistance, cardiac output, and mean CBFv increased similarly with tilt. Upright BP variability (BPV), low frequency (LF) power (0.04-0.13 Hz), and peak frequency of BPV were increased in POTS (24.3 ± 4.1, and 18.4 ± 4.1 mmHg(2)/Hz at 0.091 Hz vs. 11.8 ± 3.3, and 8.8 ± 2 mmHg(2)/Hz c at 0.071 Hz), as was upright overall CBFv variability, low frequency power and peak frequency of CBFv variability (29.3 ± 4.7, and 22.1 ± 2.7 [cm/s](2)/Hz at.092 Hz vs. 14.7 ± 2.6, and 6.7 ± 1.2 [cm/s](2)/Hz at 0.077Hz). Autospectra were sharply peaked in POTS. LF phase was decreased in POTS (-14 ± 4 vs. -25 ± 10 degrees) while upright. LF gain was increased (1.51 ± 0.09 vs. 0.86 ± 0.12 [cm/s]/ mmHg) while coherence was increased (0.96 ± 0.01 vs. 0.80 ± 0.04). Increased oscillatory BP in upright POTS patients is closely coupled to oscillatory CBFv over a narrow bandwidth corresponding to the Mayer wave frequency. Therefore combined increased oscillatory BP and increased LF gain markedly increases CBFv oscillations in a narrow bandwidth. This close coupling of CBF to MAP indicates impaired cerebral autoregulation that may underlie upright neurocognitive dysfunction in POTS.

Linking the evolution of body shape and locomotor biomechanics in bird-line archosaurs.

PubMed

Allen, Vivian; Bates, Karl T; Li, Zhiheng; Hutchinson, John R

2013-05-02

Locomotion in living birds (Neornithes) has two remarkable features: feather-assisted flight, and the use of unusually crouched hindlimbs for bipedal support and movement. When and how these defining functional traits evolved remains controversial. However, the advent of computer modelling approaches and the discoveries of exceptionally preserved key specimens now make it possible to use quantitative data on whole-body morphology to address the biomechanics underlying this issue. Here we use digital body reconstructions to quantify evolutionary trends in locomotor biomechanics (whole-body proportions and centre-of-mass position) across the clade Archosauria. We use three-dimensional digital reconstruction to estimate body shape from skeletal dimensions for 17 archosaurs along the ancestral bird line, including the exceptionally preserved, feathered taxa Microraptor, Archaeopteryx, Pengornis and Yixianornis, which represent key stages in the evolution of the avian body plan. Rather than a discrete transition from more-upright postures in the basal-most birds (Avialae) and their immediate outgroup deinonychosauria, our results support hypotheses of a gradual, stepwise acquisition of more-crouched limb postures across much of theropod evolution, although we find evidence of an accelerated change within the clade Maniraptora (birds and their closest relatives, such as deinonychosaurs). In addition, whereas reduction of the tail is widely accepted to be the primary morphological factor correlated with centre-of-mass position and, hence, evolution of hindlimb posture, we instead find that enlargement of the pectoral limb and several associated trends have a much stronger influence. Intriguingly, our support for the onset of accelerated morpho-functional trends within Maniraptora is closely correlated with the evolution of flight. Because we find that the evolution of enlarged forelimbs is strongly linked, via whole-body centre of mass, to hindlimb function during terrestrial locomotion, we suggest that the evolution of avian flight is linked to anatomical novelties in the pelvic limb as well as the pectoral.

Effects of upright and supine position on cardiac rest and exercise response in aortic regurgitation.

PubMed

Shen, W F; Roubin, G S; Fletcher, P J; Choong, C Y; Hutton, B F; Harris, P J; Kelly, D T

1985-02-01

The effects of upright and supine position on cardiac response to exercise were assessed by radionuclide ventriculography in 15 patients with moderate to severe aortic regurgitation (AR) and in 10 control subjects. In patients with AR, heart rate was higher during upright exercise, but systolic and diastolic blood pressure and left ventricular (LV) output were similar during both forms of exercise. LV stroke volume and end-diastolic volume were not altered during supine exercise. LV end-systolic volume increased and ejection fraction decreased during supine exercise, but both were unchanged during upright exercise. Of 15 patients, 5 in the upright and 12 in the supine position had an abnormal LV ejection fraction response to exercise (p less than 0.01). Right ventricular ejection fraction increased and regurgitant index decreased with both forms of exercise and was not significantly different between the 2 positions. Thus, posture is important in determining LV response to exercise in patients with moderate to severe AR.

Idiopathic orthostatic intolerance and postural tachycardia syndromes

NASA Technical Reports Server (NTRS)

Jacob, G.; Biaggioni, I.; Robertson, D. (Principal Investigator)

1999-01-01

Upright posture imposes a substantial gravitational stress on the body, for which we are able to compensate, in large part because of the autonomic nervous system. Alteration in autonomic function, therefore, may lead to orthostatic intolerance. On one extreme, patients with autonomic failure caused by degenerative loss of autonomic function are severely disabled by orthostatic hypotension and may faint whenever they stand up. Fortunately, such patients are relatively rare. On the other hand, disabling orthostatic intolerance can develop in otherwise normal young people. These patients can be severely impaired by symptoms of fatigue, tachycardia, and shortness of breath when they stand up. The actual incidence of this disorder is unknown, but these patients make up the largest group of patients referred to centers that specialize in autonomic disorders. We will review recent advances made in the understanding of this condition, potential pathophysiological mechanisms that contribute to orthostatic intolerance, therapeutic alternatives currently available for the management of these patients, and areas in which more research is needed.

The influence of an auditory-memory attention-demanding task on postural control in blind persons.

PubMed

Melzer, Itshak; Damry, Elad; Landau, Anat; Yagev, Ronit

2011-05-01

In order to evaluate the effect of an auditory-memory attention-demanding task on balance control, nine blind adults were compared to nine age-gender-matched sighted controls. This issue is particularly relevant for the blind population in which functional assessment of postural control has to be revealed through "real life" motor and cognitive function. The study aimed to explore whether an auditory-memory attention-demanding cognitive task would influence postural control in blind persons and compare this with blindfolded sighted persons. Subjects were instructed to minimize body sway during narrow base upright standing on a single force platform under two conditions: 1) standing still (single task); 2) as in 1) while performing an auditory-memory attention-demanding cognitive task (dual task). Subjects in both groups were required to stand blindfolded with their eyes closed. Center of Pressure displacement data were collected and analyzed using summary statistics and stabilogram-diffusion analysis. Blind and sighted subjects had similar postural sway in eyes closed condition. However, for dual compared to single task, sighted subjects show significant decrease in postural sway while blind subjects did not. The auditory-memory attention-demanding cognitive task had no interference effect on balance control on blind subjects. It seems that sighted individuals used auditory cues to compensate for momentary loss of vision, whereas blind subjects did not. This may suggest that blind and sighted people use different sensorimotor strategies to achieve stability. Copyright © 2010 Elsevier Ltd. All rights reserved.

Whiplash-associated disorders affect postural reactions to antero-posterior support surface translations during sitting.

PubMed

Côté, Julie N; Patenaude, Isabelle; St-Onge, Nancy; Fung, Joyce

2009-06-01

Previous studies have shown that individuals with WAD display decreased postural stability during standing and walking tasks. However, their ability to maintain seated upright posture has never been investigated. The objective of this study was to characterize kinematic and electromyographic postural stabilization patterns in individuals with chronic WAD and to compare these patterns with those in an able-bodied control group. Ten individuals with WAD and an age- and gender-matched group of healthy individuals were exposed to sudden forward and backward support surface translations while they were seated. Neck and trunk muscle activity and angular displacements as well as centers of mass (COMs) linear displacements at four levels of the head and trunk were computed. The displacement onset of the combined head, arms and trunk COM was significantly delayed in persons with WAD. However, their peak trunk angles were smaller and were reached sooner. In the WAD group, the activation onset of the lumbar erector spinae was less affected by perturbation direction and the sternocleidomastoid muscle, a neck flexor, showed a trend towards being activated later, compared to the healthy group. These results suggest that individuals with WAD may alter stretch reflex threshold and/or elicit a learned response for pain avoidance that may be direction-specific. Such findings highlight the importance of assessing both spatial and temporal characteristics across different levels of the spinal musculoskeletal system to evaluate multidirectional postural responses in WAD individuals.

Sport-specific balance.

PubMed

Zemková, Erika

2014-05-01

This review includes the latest findings based on experimental studies addressing sport-specific balance, an area of research that has grown dramatically in recent years. The main objectives of this work were to investigate the postural sway response to different forms of exercise under laboratory and sport-specific conditions, to examine how this effect can vary with expertise, and to provide examples of the association of impaired balance with sport performance and/or increasing risk of injury. In doing so, sports where body balance is one of the limiting factors of performance were analyzed. While there are no significant differences in postural stability between athletes of different specializations and physically active individuals during standing in a standard upright position (e.g., bipedal stance), they have a better ability to maintain balance in specific conditions (e.g., while standing on a narrow area of support). Differences in magnitude of balance impairment after specific exercises (rebound jumps, repeated rotations, etc.) and mainly in speed of its readjustment to baseline are also observed. Besides some evidence on an association of greater postural sway with the increasing risk of injuries, there are many myths related to the negative influence of impaired balance on sport performance. Though this may be true for shooting or archery, findings have shown that in many other sports, highly skilled athletes are able to perform successfully in spite of increased postural sway. These findings may contribute to better understanding of the postural control system under various performance requirements. It may provide useful knowledge for designing training programs for specific sports.

Active ocular vergence improves postural control in elderly as close viewing distance with or without a single cognitive task.

PubMed

Matheron, Eric; Yang, Qing; Delpit-Baraut, Vincent; Dailly, Olivier; Kapoula, Zoï

2016-01-01

Performance of the vestibular, visual, and somatosensory systems decreases with age, reducing the capacity of postural control, and increasing the risk of falling. The purpose of this study is to measure the effects of vision, active vergence eye movements, viewing distance/vergence angle and a simple cognitive task on postural control during an upright stance, in completely autonomous elderly individuals. Participated in the study, 23 elderly subjects (73.4 ± 6.8 years) who were enrolled in a center dedicated to the prevention of falling. Their body oscillations were measured with the DynaPort(®) device, with three accelerometers, placed at the lumbosacral level, near the center of mass. The conditions were the following: eyes open fixating on LED at 20 cm or 150 cm (vergence angle 17.0° and 2.3° respectively) with or without additional cognitive tasks (counting down from one hundred), performing active vergence by alternating the fixation between the far and the near LED (convergence and divergence), eyes closed after having fixated the far LED. The results showed that the postural stability significantly decreased when fixating on the LED at a far distance (weak convergence angle) with or without cognitive tasks; active convergence-divergence between the LEDs improved the postural stability while eye closure decreased it. The privilege of proximity (with increased convergence at near), previously established with foot posturography, is shown here to be valid for accelerometry with the center of mass in elderly. Another major result is the beneficial contribution of active vergence eye movements to better postural stability. The results bring new perspectives for the role of eye movement training to preserve postural control and autonomy in elderly. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

A slouched body posture decreases arm mobility and changes muscle recruitment in the neck and shoulder region.

PubMed

Malmström, Eva-Maj; Olsson, Joakim; Baldetorp, Johan; Fransson, Per-Anders

2015-12-01

Long-term use of unfavorable postures, congenital deformations and degenerative processes associated with aging or disease may generate an increased thoracic curvature resulting in pain and disability. We wanted to examine whether a slouched postural alignment with increased thoracic kyphosis changes the shoulder kinematics and muscle activity in upper trapezius (UT), lower trapezius (LT) and serratus anterior (SA) during arm elevation. The aim was to determine if a slouched posture influences range of motion, muscle activation patterns, maximal muscle activity and the total muscle work required when performing arm elevations. Twelve male subjects (23.3 ± 1.5 years) performed maximum arm elevations in upright and slouched postures. A combined 3D movement and EMG system recorded arm movements and spine curvature simultaneously with EMG activity in the UT, LT and SA. Slouched posture affected the biomechanical conditions by significantly decreasing maximum arm elevation by ~15° (p < 0.001) and decreasing arm movement velocity by ~8 % during movements upwards (p < 0.001) and downwards (p = 0.034). The peak muscle activity increased in all muscles: UT (p = 0.034, +32.3 %), LT (p = 0.001, +48.6 %) and SA (p = 0.007, +20.9 %). The total muscle work increased significantly in the slouched posture during movements upwards: UT (p = 0.003, +36.6 %), LT (p < 0.001, +89.0 %), SA (p = 0.002, +19.4 %) and downwards: UT (p = 0.012, +29.8 %) and LT (p < 0.001, +122.5 %). An increased thoracic kyphosis was found associated with marked increased physical costs when performing arm movements. Hence, patients suffering from neck-shoulder pain and disability should be investigated and treated for defective thoracic curvature issues.

Effect of postural changes on aldosterone to plasma renin ratio in patients with suspected secondary hypertension.

PubMed

Barigou, M; Ah-Kang, F; Orloff, E; Amar, J; Chamontin, B; Bouhanick, B

2015-06-01

To study the influence of postural changes on aldosterone to renin ratio (ARR) in patients with suspected secondary hypertension and to evaluate the sensitivity and specificity of the recommended seated ARR compared to supine and upright ARR for primary aldosteronism screening. Fifty-three hypertensive patients were prospectively hospitalized for secondary hypertension exploration (age: 51 ± 12, 66% males). After withdrawal of drugs interfering with renin angiotensin system, plasma aldosterone and direct renin concentration were measured in the morning, at bed after an overnight supine position, then out of bed after 1 hour of upright position and finally 2 hours later after 15 minutes of seating. Minimal renin value was set at 5 μUI/mL. Referring to ARR cut-off of 23 pg/μUI, the sensitivity of seated ARR was 57.1% and specificity was 92.3%. The negative and positive predictive values were 95.1% and 45.2% respectively. Compared to these results, a cut-off of 19 improved sensitivity to 85.7% with a specificity of 89.7%. Negative and positive predictive values were 98.3% and 41.1% respectively. Seated ARR mean value was lower than supine and upright ARR mean values, due to an overall increase in renin at seating compared to the supine position by factor 1.9 while aldosterone just slightly increased by factor 1.2. Seated ARR correlated to supine and upright ARR: correlation coefficients (r) 0.90 and 0.93 respectively (P<0.001). Current recommended measurement of ARR in the seating position is fairly correlated to supine and upright ARR. A suggested cut-off value of 19 instead of 23 pg/μUI increased the discriminating power of this test. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Hemodynamics, renal function, plasma renin, and aldosterone in man after 5 to 14 days of bedrest

NASA Technical Reports Server (NTRS)

Melada, G. A.; Goldman, R. H.; Luetscher, J. A.; Zager, P. G.

1975-01-01

Continuous bedrest for 5 to 14 days had no significant effect on resting heart rate, blood pressure, or cardiac output in six normal men. Head-up tilt induced greater tachycardia in 5 of 6 patients after bed rest than in the control period. Propranolol diminished both tachycardia and the incidence of hypotension and faintness in upright posture. Plasma volume fell, extracellular fluid volume increased, and plasma renin activity was significantly elevated following bedrest. Unusually large increases in plasma renin followed head-up tilt or administration of isoproterenol during bedrest and after resuming normal activity. During bedrest, plasma aldosterone was often increased in the early morning. It is concluded that after bedrest, upright posture evokes strong beta-adrenergic activity as well as exaggerated metabolic and circulatory responses which can be reduced or abolished by the beta-adrenergic blocker, propranolol.

Light touch compensates peripheral somatosensory degradation in postural control of older adults.

PubMed

Barela, Ana M F; Caporicci, Sarah; de Freitas, Paulo Barbosa; Jeka, John J; Barela, José A

2018-06-05

The present study aimed to investigate the sensitivity of detecting lower limb passive motion and use of additional sensory information from fingertip light touch for the postural control of older adults in comparison with young adults. A total of 11 older and 11 young adults (aged 68.1 ± 5.2 and 24.2 ± 2.2 years, respectively) underwent two tasks. We evaluated their sensitivity to passive ankle joint movement while seated in the first task. Participants then stood quietly on a force plate in a semi-tandem stance, for 30 s under two fingertip contact force conditions (no touch and light touch limited to 1 N). The results showed that the threshold of passive ankle displacement and body sway is higher in older adults than in young adults. The body sway reduced for both older and young adults with the addition of light touch at the fingertips. The maximum cross-correlation coefficient and time lags between body sway and fingertip light touch center of pressure was similar between both groups, suggesting that older adults used light touch to reduce body sway, similar to young adults. A higher threshold in detecting passive ankle joint movement may contribute to the increased body sway observed in older adults. These deficits may be compensated by additional sensory cues that would provide enhanced information used to control the upright stance. Copyright © 2018. Published by Elsevier B.V.

The role of load-carrying in the evolution of modern body proportions.

PubMed

Wang, W-J; Crompton, R H

2004-05-01

The first unquestionably bipedal early human ancestors, the species Australopithecus afarensis, were markedly different to ourselves in body proportions, having a long trunk and short legs. Some have argued that 'chimpanzee-like' features such as these suggest a 'bent-hip, bent-knee' (BHBK) posture would have been adopted during gait. Computer modelling studies, however, indicate that this early human ancestor could have walked in a reasonably efficient upright posture, whereas BHBK posture would have nearly doubled the mechanical energy cost of locomotion, as it does the physiological cost of locomotion in ourselves. More modern body proportions first appear at around 1.8-1.5 Ma, with Homo ergaster (early African Homo erectus), represented by the Nariokotome skeleton KNM-WT 15000, in which the legs were considerably longer in relation to the trunk than they are in human adults, although this skeleton represents an adolescent. Several authors have suggested that this morphology would have allowed faster, more endurant walking. But during the same period, the archaeological record indicates a sharp rise in distances over which stone tools or raw materials are transported. Is this coincidental, or can load-carrying also be implicated in selection for a more modern morphology? Computer simulations of loaded walking, verified against kinetic data for humans, show that BHBK gait is even more ineffective while load-carrying. However, walking erect, the Nariokotome individual could have carried loads of 10-15% body mass for less cost, relative to body size, than AL 288-1 walking erect but unloaded. In fact, to the extent that our sample of humans is typical, KNM-WT 15000 would have had better mechanical effectiveness in bearing light loads on the back than modern human adults. Thus, selection for effectiveness in load-carrying, as well as in endurant walking, is indeed likely to have been implicated in the evolution of modern body proportions.

The role of load-carrying in the evolution of modern body proportions

PubMed Central

Wang, W -J; Crompton, R H

2004-01-01

The first unquestionably bipedal early human ancestors, the species Australopithecus afarensis, were markedly different to ourselves in body proportions, having a long trunk and short legs. Some have argued that ′chimpanzee-like′ features such as these suggest a ‘bent-hip, bent-knee’ (BHBK) posture would have been adopted during gait. Computer modelling studies, however, indicate that this early human ancestor could have walked in a reasonably efficient upright posture, whereas BHBK posture would have nearly doubled the mechanical energy cost of locomotion, as it does the physiological cost of locomotion in ourselves. More modern body proportions first appear at around 1.8–1.5 Ma, with Homo ergaster (early African Homo erectus), represented by the Nariokotome skeleton KNM-WT 15000, in which the legs were considerably longer in relation to the trunk than they are in human adults, although this skeleton represents an adolescent. Several authors have suggested that this morphology would have allowed faster, more endurant walking. But during the same period, the archaeological record indicates a sharp rise in distances over which stone tools or raw materials are transported. Is this coincidental, or can load-carrying also be implicated in selection for a more modern morphology? Computer simulations of loaded walking, verified against kinetic data for humans, show that BHBK gait is even more ineffective while load-carrying. However, walking erect, the Nariokotome individual could have carried loads of 10–15% body mass for less cost, relative to body size, than AL 288-1 walking erect but unloaded. In fact, to the extent that our sample of humans is typical, KNM-WT 15000 would have had better mechanical effectiveness in bearing light loads on the back than modern human adults. Thus, selection for effectiveness in load-carrying, as well as in endurant walking, is indeed likely to have been implicated in the evolution of modern body proportions. PMID:15198704

Postural strategies in Prader-Willi and Down syndrome patients.

PubMed

Cimolin, Veronica; Galli, Manuela; Grugni, Graziano; Vismara, Luca; Precilios, Helmer; Albertini, Giorgio; Rigoldi, Chiara; Capodaglio, Paolo

2011-01-01

Patients affected by Down (DS) and Prader-Willi syndrome (PWS) are characterised by some common clinical and functional features including gait disorders and reduced postural control. The aim of our study was to quantitatively compare postural control in adult PWS and DS. We studied 12 PWS and 19 DS adult patients matched for age, height, weight and body mass index. They were instructed to maintain an upright standing position on a force platform for 30s with open eyes (OE) and we calculated the range of center of pressure (CoP) displacement in the A/P direction (RANGE(AP)) and in the M/L direction (RANGE(ML)) and the total CoP trajectory length during quiet stance (Sway Path, SP). The range of oscillations in PWS and DS in both AP and ML direction were higher than in controls. PWS and DS were statistically different for RANGE(AP), with PWS showing higher mean values. Our results confirm a reduced capacity of both PWS and DS in maintaining postural stability. This appears to be in some respect different in PWS and DS, with PWS showing poorer control in AP. DS and, particularly, PWS should be encouraged to undergo specific balance training and strengthening of the ankle muscles as part of a comprehensive rehabilitation program to enhance daily functioning and quality of life. Copyright © 2010 Elsevier Ltd. All rights reserved.

Second-order motor planning in children: insights from a cup-manipulation-task.

PubMed

Wunsch, Kathrin; Weiss, Daniel J; Schack, Thomas; Weigelt, Matthias

2015-07-01

The present study examined the development of anticipatory motor planning in an object manipulation task that has been used to successfully demonstrate motor planning in non-human primates (Weiss et al. in Psychol Sci 18:1063-1068, 2007). Seventy-five participants from four different age groups participated in a cup-manipulation task. One group was preschool children (average age of 5.1 years), two groups were primary school children (7.7 and 9.8 years old respectively) and the final group was comprised of adults. The experimental task entailed reaching for a plastic cup that was vertically suspended in an apparatus in either upright or inverted orientation, removing the cup by its stem and then retrieving a small toy from the inside of the cup. When the cup was inverted in the apparatus, evidence for anticipatory motor planning could be achieved by initially gripping the stem using an inverted (thumb-down) grip posture. We found that when the cup was in upright orientation, all participants reached for the cup using an upright grip (i.e., thumb-up posture). However, when the cup was inverted in the apparatus, only adults consistently used an inverted grasping posture, though the percentage of inverted grips among participants did increase with age. These results suggest a protracted development for anticipatory motor planning abilities in children. Surprisingly, the performance of adults on this task more closely resembles the performance of several nonhuman primate species as opposed to children even at approximately 10 years of age. We discuss how morphological constraints on flexibility may help account for these findings.

How providing more or less time to solve a cognitive task interferes with upright stance control; a posturographic analysis on healthy young adults.

PubMed

Rougier, Patrice R; Bonnet, Cédrick T

2016-06-01

Contrasted postural effects have been reported in dual-task protocols associating balance control and cognitive task that could be explained by the nature and the relative difficulty of the cognitive task and the biomechanical significance of the force platform data. To better assess their respective role, eleven healthy young adults were required to stand upright quietly on a force platform while concomitantly solving mental-calculation or mental-navigation cognitive tasks. Various levels of difficulty were applied by adjusting the velocity rate at which the instructions were provided to the subject according to his/her maximal capacities measured beforehand. A condition without any concomitant cognitive task was added to constitute a baseline behavior. Two basic components, the horizontal center-of-gravity movements and the horizontal difference between center-of-gravity and center-of-pressures were computed from the complex center-of-pressure recorded movements. It was hypothesized that increasing the delay should infer less interaction between postural control and task solution. The results indicate that both mental-calculation and mental-navigation tasks induce reduced amplitudes for the center-of-pressure minus center-of-gravity movements, only along the mediolateral axis, whereas center-of-gravity movements were not affected, suggesting that different circuits are involved in the central nervous system to control these two movements. Moreover, increasing the delays task does not infer any effect for both movements. Since center-of-pressure minus center-of-gravity expresses the horizontal acceleration communicated to the center-of-gravity, one may assume that the control of the latter should be facilitated in dual-tasks conditions, inferring reduced center-of-gravity movements, which is not seen in our results. This lack of effect should be thus interpreted as a modification in the control of these center-of-gravity movements. Taken together, these results emphasized how undisturbed upright stance control can be impacted by mental tasks requiring attention, whatever their nature (calculation or navigation) and their relative difficulty. Depending on the provided instructions, i.e. focusing our attention on body movements or on the opposite diverting this attention toward other objectives, the evaluation of upright stance control capacities might be drastically altered. Copyright © 2016. Published by Elsevier B.V.

[Posture and aging. Current fundamental studies and management concepts].

PubMed

Mourey, F; Camus, A; Pfitzenmeyer, P

2000-02-19

FUNDAMENTAL IMPORTANCE OF POSTURE: In the elderly subject, preservation of posture is fundamental to maintaining functional independence. In recent years, there has been much progress in our understanding of the mechanisms underlying strategies used to control equilibrium in the upright position. Physiological aging, associated with diverse disease states, dangerously alters the postural function, particularly anticipated adjustments which allow an adaptation of posture to movement. CLINICAL ASSESSMENT OF POSTURE: Several tests have been developed to assess posture in the elderly subject, particularly the time it takes to start walking. We selected certain tests which can be used in everyday practice to predict falls: the stance test, the improved Romberg test, the "timed get up and go test", measurement of walking cadence, assessment of balance reactions, sitting-standing and standing-sitting movements and capacity to get up off the floor. PATIENT CARE: Elderly patients with equilibrium disorders can benefit from specific personalized rehabilitation protocols. Different techniques have been developed for multiple afferential stimulation, reprogramming postural strategies, and correcting for deficient motor automatisms.

Specificity of foot configuration during bipedal stance in ballet dancers.

PubMed

Casabona, Antonino; Leonardi, Giuseppa; Aimola, Ettore; La Grua, Giovanni; Polizzi, Cristina Maria; Cioni, Matteo; Valle, Maria Stella

2016-05-01

Learning highly specialized upright postures may be of benefit for more common as well as for novel stances. In this study, we asked whether this generalization occurs with foot configurations previously trained or depends on a generic increase in balance difficulty. We also explored the possibility that the benefit may concern not only the level of postural performance but also the structural organization of the upright standing. Ten elite professional ballet dancers were compared to ten untrained subjects, measuring the motion of the center of pressure (COP) across a set of five stances with different foot configurations. The balance stability was measured computing the area, the sway path, and the root mean square of the COP motion, whereas the structure of the postural control was assessed by compute approximate entropy, fractal dimension and the mean power frequency. The foot position included common and challenging stances, with the level of difficulty changed across the configurations. Among these conditions, only one foot configuration was familiar to the dancers. Statistically significant differences between the two groups, for all the parameters, were observed only for the stance with the foot position familiar to the dancers. Stability and structural parameters exhibited comparable differences. We concluded that the benefit from classical ballet is limited to a specific foot configuration, regardless of the level of stance difficulty or the component of postural control. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of Lifetime Occupational Pesticide Exposure on Postural Control Among Farmworkers and Non-Farmworkers.

PubMed

Sunwook, Kim; Nussbaum, Maury A; Quandt, Sara A; Laurienti, Paul J; Arcury, Thomas A

2016-02-01

The aim of the study was to assess potential chronic effects of pesticide exposure on postural control, by examining postural balance of farmworkers and non-farmworkers diverse self-reported lifetime exposures. Balance was assessed during quiet upright stance under four experimental conditions (2 visual × 2 cognitive difficulty). Significant differences in baseline balance performance (eyes open without cognitive task) between occupational groups were apparent in postural sway complexity. When adding a cognitive task to the eyes open condition, the influence of lifetime exposure on complexity ratios appeared different between occupational groups. Removing visual information revealed a negative association of lifetime exposure with complexity ratios. Farmworkers and non-farmworkers may use different postural control strategies even when controlling for the level of lifetime pesticide exposure. Long-term exposure can affect somatosensory/vestibular sensory systems and the central processing of sensory information for postural control.

Effects of lifetime occupational pesticide exposure on postural control among farmworkers and non-farmworkers

PubMed Central

Sunwook, Kim; Nussbaum, Maury A.; Quandt, Sara A.; Laurienti, Paul J.; Arcury, Thomas A.

2015-01-01

Objective Assess potential chronic effects of pesticide exposure on postural control, by examining postural balance of farmworkers and non-farmworkers diverse self-reported lifetime exposures. Methods Balance was assessed during quiet upright stance under four experimental conditions (2 visual × 2 cognitive difficulty). Results Significant differences in baseline balance performance (eyes open without cognitive task) between occupational groups were apparent in postural sway complexity. When adding a cognitive task to the eyes open condition, the influence of lifetime exposure on complexity ratios appeared different between occupational groups. Removing visual information revealed a negative association of lifetime exposure with complexity ratios. Conclusions Farmworkers and non-farmworkers may use different postural control strategies even when controlling for the level of lifetime pesticide exposure. Long-term exposure can affect somatosensory/vestibular sensory systems and the central processing of sensory information for postural control. PMID:26849257

Quantification of cardiorespiratory interactions based on joint symbolic dynamics.

PubMed

Kabir, Muammar M; Saint, David A; Nalivaiko, Eugene; Abbott, Derek; Voss, Andreas; Baumert, Mathias

2011-10-01

Cardiac and respiratory rhythms are highly nonlinear and nonstationary. As a result traditional time-domain techniques are often inadequate to characterize their complex dynamics. In this article, we introduce a novel technique to investigate the interactions between R-R intervals and respiratory phases based on their joint symbolic dynamics. To evaluate the technique, electrocardiograms (ECG) and respiratory signals were recorded in 13 healthy subjects in different body postures during spontaneous and controlled breathing. Herein, the R-R time series were extracted from ECG and respiratory phases were obtained from abdomen impedance belts using the Hilbert transform. Both time series were transformed into ternary symbol vectors based on the changes between two successive R-R intervals or respiratory phases. Subsequently, words of different symbol lengths were formed and the correspondence between the two series of words was determined to quantify the interaction between cardiac and respiratory cycles. To validate our results, respiratory sinus arrhythmia (RSA) was further studied using the phase-averaged characterization of the RSA pattern. The percentage of similarity of the sequence of symbols, between the respective words of the two series determined by joint symbolic dynamics, was significantly reduced in the upright position compared to the supine position (26.4 ± 4.7 vs. 20.5 ± 5.4%, p < 0.01). Similarly, RSA was also reduced during upright posture, but the difference was less significant (0.11 ± 0.02 vs. 0.08 ± 0.01 s, p < 0.05). In conclusion, joint symbolic dynamics provides a new efficient technique for the analysis of cardiorespiratory interaction that is highly sensitive to the effects of orthostatic challenge.

50 CFR 14.161 - Primary enclosures.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Wild Mammals and Birds to the United States Specifications for Other Terrestrial Mammals § 14.161... primary enclosure shall provide adequate space for the animal to stand upright in a normal posture with... lie in a full prone position. Specifications for Birds ...

Locomotor sensory organization test: a novel paradigm for the assessment of sensory contributions in gait.

PubMed

Chien, Jung Hung; Eikema, Diderik-Jan Anthony; Mukherjee, Mukul; Stergiou, Nicholas

2014-12-01

Feedback based balance control requires the integration of visual, proprioceptive and vestibular input to detect the body's movement within the environment. When the accuracy of sensory signals is compromised, the system reorganizes the relative contributions through a process of sensory recalibration, for upright postural stability to be maintained. Whereas this process has been studied extensively in standing using the Sensory Organization Test (SOT), less is known about these processes in more dynamic tasks such as locomotion. In the present study, ten healthy young adults performed the six conditions of the traditional SOT to quantify standing postural control when exposed to sensory conflict. The same subjects performed these six conditions using a novel experimental paradigm, the Locomotor SOT (LSOT), to study dynamic postural control during walking under similar types of sensory conflict. To quantify postural control during walking, the net Center of Pressure sway variability was used. This corresponds to the Performance Index of the center of pressure trajectory, which is used to quantify postural control during standing. Our results indicate that dynamic balance control during locomotion in healthy individuals is affected by the systematic manipulation of multisensory inputs. The sway variability patterns observed during locomotion reflect similar balance performance with standing posture, indicating that similar feedback processes may be involved. However, the contribution of visual input is significantly increased during locomotion, compared to standing in similar sensory conflict conditions. The increased visual gain in the LSOT conditions reflects the importance of visual input for the control of locomotion. Since balance perturbations tend to occur in dynamic tasks and in response to environmental constraints not present during the SOT, the LSOT may provide additional information for clinical evaluation on healthy and deficient sensory processing.

Current physical activity improves balance control during sensory conflicting conditions in older adults.

PubMed

Buatois, S; Gauchard, G C; Aubry, C; Benetos, A; Perrin, P

2007-01-01

Aging process is characterized by difficulties in ensuring balance control, especially in conditions of reduced or conflicting sensory information, leading to an increased risk of falling. Conversely, the practise of physical activities (PA) has been recognized as a good approach to improve the quality of balance control. This study aimed to investigate the influence of current and/or past PA on balance-related neurosensorial organization in older adults on the maintenance of the upright stance, especially during sensory conflicting situations. Postural control was evaluated by means of the Sensory Organization Test on 130 healthy noninstitutionalized volunteers aged over 65, split into four groups according to the presence or absence of PA before or after retirement. Subjects who practised PA for a long time (Gr1) and subjects who started PA after retirement (Gr2) displayed the best postural performances and better managed sensory conflicting situations compared to subjects who had stopped PA for many years (Gr3) and subjects who had never practised PA (Gr4). Multiple regression analyses revealed that current PA was the major determinant for postural parameters during sensorial conflict compared to age, gender, body mass index and past PA. Regular PA, even when started late in life, allows appropriate reorganization of the different components of postural control during sensory conflicting situations. Indeed, active subjects were more able to compensate for suppressed or perturbed sensory information by an increased usage of another referential and so to correct their posture by adopting a more appropriate balance strategy. Thus, PA counteracts the age-related decline of postural control and could consequently reduce the risk of falling.

Application of postured human model for SAR measurements

NASA Astrophysics Data System (ADS)

Vuchkovikj, M.; Munteanu, I.; Weiland, T.

2013-07-01

In the last two decades, the increasing number of electronic devices used in day-to-day life led to a growing interest in the study of the electromagnetic field interaction with biological tissues. The design of medical devices and wireless communication devices such as mobile phones benefits a lot from the bio-electromagnetic simulations in which digital human models are used. The digital human models currently available have an upright position which limits the research activities in realistic scenarios, where postured human bodies must be considered. For this reason, a software application called "BodyFlex for CST STUDIO SUITE" was developed. In its current version, this application can deform the voxel-based human model named HUGO (Dipp GmbH, 2010) to allow the generation of common postures that people use in normal life, ensuring the continuity of tissues and conserving the mass to an acceptable level. This paper describes the enhancement of the "BodyFlex" application, which is related to the movements of the forearm and the wrist of a digital human model. One of the electromagnetic applications in which the forearm and the wrist movement of a voxel based human model has a significant meaning is the measurement of the specific absorption rate (SAR) when a model is exposed to a radio frequency electromagnetic field produced by a mobile phone. Current SAR measurements of the exposure from mobile phones are performed with the SAM (Specific Anthropomorphic Mannequin) phantom which is filled with a dispersive but homogeneous material. We are interested what happens with the SAR values if a realistic inhomogeneous human model is used. To this aim, two human models, a homogeneous and an inhomogeneous one, in two simulation scenarios are used, in order to examine and observe the differences in the results for the SAR values.

Letter to the Editor: On "Advantages and disadvantages of stiffness instructions when studying postural control" by C.T. Bonnet: You just can't win: Advantages and disadvantages of the postural stability requirement.

PubMed

Lajoie, Y; Richer, N; Jehu, D A; Polskaia, N; Saunders, D

2016-05-01

In the examination of postural control, instructions to stand as still as possible are common and promote a relatively unnatural sway pattern. The validity of the stability requirement is discussed in the present commentary in response to the discussion initiated by Cedrick T. Bonnet. The advantages of using the stability requirement include: evaluating unbiased postural control, reducing variability in postural sway, manipulating focus of attention, examining the ability to maintain an upright stance, and ecological validity of testing. The disadvantages include: constraining natural postural sway, increasing the complexity of the control condition, promoting an internal focus of attention, and reducing the ability to detect exploratory behaviour. After evaluating the aforementioned advantages and disadvantages, the present commentary suggests that researchers should strive to provide specific instructions to maintain feet, arm and eye position without specifically requiring participants to reduce their postural sway. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of the SORRI-BAURU Posterior Walker.

PubMed

Nicholl, Anthony R J; Busnardo, Renato G; da Silva, Luciana M; Rodrigues, Ana Cláudia T; Luz, Fernanda R C; Bentim, Claudia C G; Medola, Fausto O; Paschoarelli, Luis C

2015-01-01

This study aimed to report on the design and development of a low cost Reverse Walker through a participative development cycle with people undergoing rehabilitation. The creation and fundamentals of the concept are described, as well as the development of prototypes and their provision to subjects with mobility problems. The Reverse Walker benefits the user by promoting a more upright posture and favoring the development of postural balance. Enhancing the mobility of people with disabilities may benefit their independence, social participation and quality of life.

Optimal handgrip height of four-wheeled walker on various road conditions to reduce muscular load for elderly users with steady walking.

PubMed

Takanokura, Masato

2010-03-22

A four-wheeled walker is a valuable tool for assisting elderly persons with walking. The handgrip height is one of the most important factor determining the usefulness of the walker. However, the optimal handgrip height for elderly users has not been considered from a biomechanical viewpoint. In this study, the handgrip height was optimized by a two-dimensional mechanical model to reduce muscular loads in the lower body as well as in the upper body with various road conditions during steady walking. A critical height of the handgrip existed at 48% of the body height for the user regardless of gender and body dimension. A lower handgrip relieved muscular load for stooping users with a lower standing height. The stooping user pushed the handgrip strongly in the perpendicular direction by leaning the upper body on the walker. However, upright users with a higher standing height should use a four-wheeled walker with a higher handgrip for maintaining his or her upright posture. For downhill movement, the optimal handgrip height depended on the slope angle and the friction coefficient between the road and the wheels of the walker. On a low-friction downhill such as asphalt with a steeper slope angle, the user was required to maintain an erect trunk with a higher handgrip and to press on the handgrip strongly in the perpendicular direction. Movement on a low-friction road was easier for users on a flat road and an uphill road, but it compelled distinct effort from users when moving downhill. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Neural Control of the Cardiovascular System in Space

NASA Technical Reports Server (NTRS)

Levine, Benjamin D.; Pawelczyk, James A.; Zuckerman, Julie; Zhang, Rong; Fu, Qi; Iwasaki, Kenichi; Ray, Chet; Blomqvist, C. Gunnar; Lane, Lynda D.; Giller, Cole A.

2003-01-01

During the acute transition from lying supine to standing upright, a large volume of blood suddenly moves from the chest into the legs. To prevent fainting, the blood pressure control system senses this change immediately, and rapidly adjusts flow (by increasing heart rate) and resistance to flow (by constricting the blood vessels) to restore blood pressure and maintain brain blood flow. If this system is inadequate, the brain has a backup plan. Blood vessels in the brain can adjust their diameter to keep blood flow constant. If blood pressure drops, the brain blood vessels dilate; if blood pressure increases, the brain blood vessels constrict. This process, which is called autoregulation, allows the brain to maintain a steady stream of oxygen, even when blood pressure changes. We examined what changes in the blood pressure control system or cerebral autoregulation contribute to the blood pressure control problems seen after spaceflight. We asked: (1) does the adaptation to spaceflight cause an adaptation in the blood pressure control system that impairs the ability of the system to constrict blood vessels on return to Earth?; (2) if such a defect exists, could we pinpoint the neural pathways involved?; and (3) does cerebral autoregulation become abnormal during spaceflight, impairing the body s ability to maintain constant brain blood flow when standing upright on Earth? We stressed the blood pressure control system using lower body negative pressure, upright tilt, handgrip exercise, and cold stimulation of the hand. Standard cardiovascular parameters were measured along with sympathetic nerve activity (the nerve activity causing blood vessels to constrict) and brain blood flow. We confirmed that the primary cardiovascular effect of spaceflight was a postflight reduction in upright stroke volume (the amount of blood the heart pumps per beat). Heart rate increased appropriately for the reduction in stroke volume, thereby showing that changes in heart rate regulation alone cannot be responsible for orthostatic hypotension after spaceflight. All of the astronauts in our study had an increase in sympathetic nerve activity during upright tilting on Earth postflight. This increase was well calibrated for the reduction in stroke volume induced by the upright posture. The results obtained from stimulating the sympathetic nervous system using handgrip exercise or cold stress were also entirely normal during and after spaceflight. No astronaut had reduced cerebral blood flow during upright tilt, and cerebral autoregulation was normal or even enhanced inflight. These experiments show that the cardiovascular adaptation to spaceflight does not lead to a defect in the regulation of blood vessel constriction via sympathetic nerve activity. In addition, cerebral autoregulation is well-maintained. It is possible that despite the increased sympathetic nerve activity, blood vessels did not respond with a greater degree of constriction than occurred preflight, possibly uncovering a limit of vasoconstrictor reserve.

Can supine recovery mitigate the exercise intensity dependent attenuation of post-exercise heat loss responses?

PubMed

Kenny, Glen P; Gagnon, Daniel; Jay, Ollie; McInnis, Natalie H; Journeay, W Shane; Reardon, Francis D

2008-08-01

Cutaneous vascular conductance (CVC) and sweat rate are subject to non-thermal baroreflex-mediated attenuation post-exercise. Various recovery modalities have been effective in attenuating these decreases in CVC and sweat rate post-exercise. However, the interaction of recovery posture and preceding exercise intensity on post-exercise thermoregulation remains unresolved. We evaluated the combined effect of supine recovery and exercise intensity on post-exercise cardiovascular and thermal responses relative to an upright seated posture. Seven females performed 15 min of cycling ergometry at low- (LIE, 55% maximal oxygen consumption) or high-(HIE, 85% maximal oxygen consumption) intensity followed by 60 min of recovery in either an upright seated or supine posture. Esophageal temperature, CVC, sweat rate, cardiac output, stroke volume, heart rate, total peripheral resistance, and mean arterial pressure (MAP) were measured at baseline, at end-exercise, and at 2, 5, 12, 20, and every 10 min thereafter until the end of recovery. MAP and stroke volume were maintained during supine recovery to a greater extent relative to an upright seated recovery following HIE (p

Perfusion Controlled Mobilization after Lower Extremity Free Flaps-Pushing the Limits of Time and Intensity.

PubMed

Dornseifer, Ulf; Kleeberger, Charlotte; Kargl, Lukas; Schönberger, Markus; Rohde, Daniel; Ninkovic, Milomir; Schilling, Arndt

2017-03-01

Background  The current standard to gradually adapt the fragile perfusion in lower extremity free flaps to an upright posture is the dangling maneuver. This type of flap training neither fits the orthostatic target load of an upright posture, nor does it assist in mobilizing the patients effectively. In this study, we quantitatively analyzed training effects of an early and full mobilization on flap perfusion. Methods  A total of 15 patients with gracilis flaps for distal lower extremity reconstruction were included. Flap training was performed daily by mobilizing the patients on a tilt table into a fully upright posture for 5 minutes between the third and fifth postop days (PODs). Changes in micro- and macrocirculation were analyzed by laser Doppler flowmetry, remission spectroscopy, and an implanted Doppler probe. Results  All flaps healed without complications. Yet, in three patients, the increased orthostatic load required an adjustment of the training duration due to a critical blood flow. The others showed an increasing compensation in the microcirculation. When tilting the patients, blood flow and oxygen saturation dropped significantly less on POD5 than on POD3. Furthermore, a significant increase of the blood flow was noted after an initial decrease during the mobilization on all days. An increasing compensation in the macrocirculation could not be determined. Conclusion  Full mobilization of patients with lower extremity free flaps can be performed safely under perfusion monitoring, already starting on POD3. Additionally, monitoring allows a consideration of the individual orthostatic competence and therefore, exploitation of the maximum mobilization potential. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Virtual animation of victim-specific 3D models obtained from CT scans for forensic reconstructions: Living and dead subjects.

PubMed

Villa, C; Olsen, K B; Hansen, S H

2017-09-01

Post-mortem CT scanning (PMCT) has been introduced at several forensic medical institutions many years ago and has proved to be a useful tool. 3D models of bones, skin, internal organs and bullet paths can rapidly be generated using post-processing software. These 3D models reflect the individual physiognomics and can be used to create whole-body 3D virtual animations. In such way, virtual reconstructions of the probable ante-mortem postures of victims can be constructed and contribute to understand the sequence of events. This procedure is demonstrated in two victims of gunshot injuries. Case #1 was a man showing three perforating gunshot wounds, who died due to the injuries of the incident. Whole-body PMCT was performed and 3D reconstructions of bones, relevant internal organs and bullet paths were generated. Using 3ds Max software and a human anatomy 3D model, a virtual animated body was built and probable ante-mortem postures visualized. Case #2 was a man presenting three perforating gunshot wounds, who survived the incident: one in the left arm and two in the thorax. Only CT scans of the thorax, abdomen and the injured arm were provided by the hospital. Therefore, a whole-body 3D model reflecting the anatomical proportions of the patient was made combining the actual bones of the victim with those obtained from the human anatomy 3D model. The resulted 3D model was used for the animation process. Several probable postures were also visualized in this case. It has be shown that in Case #1 the lesions and the bullet path were not consistent with an upright standing position; instead, the victim was slightly bent forward, i.e. he was sitting or running when he was shot. In Case #2, one of the bullets could have passed through the arm and continued into the thorax. In conclusion, specialized 3D modelling and animation techniques allow for the reconstruction of ante-mortem postures based on both PMCT and clinical CT. Copyright © 2017 Elsevier B.V. All rights reserved.

Classifying prosthetic use via accelerometry in persons with transtibial amputations.

PubMed

Redfield, Morgan T; Cagle, John C; Hafner, Brian J; Sanders, Joan E

2013-01-01

Knowledge of how persons with amputation use their prostheses and how this use changes over time may facilitate effective rehabilitation practices and enhance understanding of prosthesis functionality. Perpetual monitoring and classification of prosthesis use may also increase the health and quality of life for prosthetic users. Existing monitoring and classification systems are often limited in that they require the subject to manipulate the sensor (e.g., attach, remove, or reset a sensor), record data over relatively short time periods, and/or classify a limited number of activities and body postures of interest. In this study, a commercially available three-axis accelerometer (ActiLife ActiGraph GT3X+) was used to characterize the activities and body postures of individuals with transtibial amputation. Accelerometers were mounted on prosthetic pylons of 10 persons with transtibial amputation as they performed a preset routine of actions. Accelerometer data was postprocessed using a binary decision tree to identify when the prosthesis was being worn and to classify periods of use as movement (i.e., leg motion such as walking or stair climbing), standing (i.e., standing upright with limited leg motion), or sitting (i.e., seated with limited leg motion). Classifications were compared to visual observation by study researchers. The classifier achieved a mean +/- standard deviation accuracy of 96.6% +/- 3.0%.

Classifying Prosthetic Use via Accelerometry in Persons with Trans-Tibial Amputations

PubMed Central

Redfield, Morgan T.; Cagle, John C.; Hafner, Brian J.; Sanders, Joan E.

2014-01-01

Knowledge of how persons with amputation use their prostheses and how this use changes over time may facilitate effective rehabilitation practices and enhance understanding of prosthesis functionality. Perpetual monitoring and classification of prosthesis use may also increase the health and quality of life for prosthetic users. Existing monitoring and classification systems are often limited in that they require the subject to manipulate the sensor (e.g., attach, remove, or reset a sensor), record data over relatively short time periods, and/or classify a limited number of activities and body postures of interest. In this study, a commercially-available three-axis accelerometer (ActiLife ActiGraph GT3X+) was used to characterize the activities and body postures of individuals with trans-tibial amputation. Accelerometers were mounted on prosthetic pylons of ten persons with trans-tibial amputation as they performed a preset routine of actions. Accelerometer data was post-processed using a Binary Decision Tree to identify when the prosthesis was being worn and to classify periods of use as movement (i.e., leg motion like walking or stair climbing), standing (i.e., standing upright with limited leg motion), or sitting (i.e., seated with limited leg motion). Classifications were compared to visual observation by study researchers. The classifier achieved a mean accuracy of 96.6% (SD=3.0%). PMID:24458961

Fat King Penguins Are Less Steady on Their Feet

PubMed Central

Willener, Astrid S. T.; Handrich, Yves; Halsey, Lewis G.; Strike, Siobhán

2016-01-01

Returning to the shore after a feeding sojourn at sea, king penguins often undertake a relatively long terrestrial journey to the breeding colony carrying a heavy, mostly frontal, accumulation of fat along with food in the stomach for chick-provisioning. There they must survive a fasting period of up to a month in duration, during which their complete reliance on endogenous energy stores results in a dramatic loss in body mass. Our aim was to determine if the king penguin’s walking gait changes with variations in body mass. We investigated this by walking king penguins on a treadmill while instrumented with an acceleration data logger. The stride frequency, dynamic body acceleration (DBA) and posture of fat (pre-fasting; 13.2 kg) and slim (post fasting; 11 kg) king penguins were assessed while they walked at the same speed (1.4km/h) on a treadmill. Paired statistical tests indicated no evidence for a difference in dynamic body acceleration or stride frequency between the two body masses however there was substantially less variability in both leaning angle and the leaning amplitude of the body when the birds were slimmer. Furthermore, there was some evidence that the slimmer birds exhibited a decrease in waddling amplitude. We suggest the increase in variability of both leaning angle and amplitude, as well as a possibly greater variability in the waddling amplitude, is likely to result from the frontal fat accumulation when the birds are heavier, which may move the centre of mass anteriorly, resulting in a less stable upright posture. This study is the first to use accelerometry to better understand the gait of a species within a specific ecological context: the considerable body mass change exhibited by king penguins. PMID:26886216

Fat King Penguins Are Less Steady on Their Feet.

PubMed

Willener, Astrid S T; Handrich, Yves; Halsey, Lewis G; Strike, Siobhán

2016-01-01

Returning to the shore after a feeding sojourn at sea, king penguins often undertake a relatively long terrestrial journey to the breeding colony carrying a heavy, mostly frontal, accumulation of fat along with food in the stomach for chick-provisioning. There they must survive a fasting period of up to a month in duration, during which their complete reliance on endogenous energy stores results in a dramatic loss in body mass. Our aim was to determine if the king penguin's walking gait changes with variations in body mass. We investigated this by walking king penguins on a treadmill while instrumented with an acceleration data logger. The stride frequency, dynamic body acceleration (DBA) and posture of fat (pre-fasting; 13.2 kg) and slim (post fasting; 11 kg) king penguins were assessed while they walked at the same speed (1.4 km/h) on a treadmill. Paired statistical tests indicated no evidence for a difference in dynamic body acceleration or stride frequency between the two body masses however there was substantially less variability in both leaning angle and the leaning amplitude of the body when the birds were slimmer. Furthermore, there was some evidence that the slimmer birds exhibited a decrease in waddling amplitude. We suggest the increase in variability of both leaning angle and amplitude, as well as a possibly greater variability in the waddling amplitude, is likely to result from the frontal fat accumulation when the birds are heavier, which may move the centre of mass anteriorly, resulting in a less stable upright posture. This study is the first to use accelerometry to better understand the gait of a species within a specific ecological context: the considerable body mass change exhibited by king penguins.

Dehydration-induced drinking in humans

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.

1982-01-01

The human tendency to experience a delay in rehydration (involuntary dehydration) after fluid loss is considered. The two primary factors contributing to involuntary dehydration are probably upright posture, and extracellular fluid and electrolyte loss by sweating from exercise and heat exposure. First, as the plasma sodium and osmotic concentrations remain virtually unchanged for supine to upright postural changes, the major stimuli for drinking appear to be associated with the hypovolemia and increase in the renin-angiotension system. Second, voluntary drinking during the heat experiments was 146% greater than in cool experiments; drinking increased by 109% with prior dehydration as opposed to normal hydration conditions; and drinking was increased by 41% after exercise as compared with the resting condition. Finally, it is concluded that the rate of sweating and the rate of voluntary fluid intake are highly correlated, and that the dispogenic factors of plasma volume, osmolality, and plasma renin activity are unrelated to sweat rate, but are likely to induce drinking in humans.

Stability and Control of Human Trunk Movement During Walking.

PubMed

Wu, Q.; Sepehri, N.; Thornton-Trump, A. B.; Alexander, M.

1998-01-01

A mathematical model has been developed to study the control mechanisms of human trunk movement during walking. The trunk is modeled as a base-excited inverted pendulum with two-degrees of rotational freedom. The base point, corresponding to the bony landmark of the sacrum, can move in three-dimensional space in a general way. Since the stability of upright posture is essential for human walking, a controller has been designed such that the stability of the pendulum about the upright position is guaranteed. The control laws are developed based on Lyapunov's stability theory and include feedforward and linear feedback components. It is found that the feedforward component plays a critical role in keeping postural stability, and the linear feedback component, (resulting from viscoelastic function of the musculoskeletal system) can effectively duplicate the pattern of trunk movement. The mathematical model is validated by comparing the simulation results with those based on gait measurements performed in the Biomechanics Laboratory at the University of Manitoba.

Assessment of Prone Positioning of Restrained, Seated Crewmembers in a Post Landing Stable 2 Orion Configuration

NASA Technical Reports Server (NTRS)

Barr, Yael; Fogarty, Jennifer

2010-01-01

During the Orion landing and recovery subsystem design review, June 2009, it was noted that the human system and various vehicle systems, the environmental control and life support (ECLSS) and guidance, navigation and control (GN&C) systems for example, are negatively affected by Orion assuming a stable 2 (upside down; Figure A) configuration post landing. The stable 2 configuration is predicted to occur about 50% of the time based on Apollo landing data and modeling of the current capsule. The stable 2 configuration will be countered by an active up-righting system (crew module up-righting system; CMUS). Post landing balloons will deploy and inflate causing the vehicle to assume or maintain the stable 1 (up-right; Figure B) configuration. During the design review it was proposed that the up-righting system could be capable of righting the vehicle within 60 seconds. However, this time limit posed a series of constraints on the design which made it less robust than desired. The landing and recovery subsystem team requested an analysis of Orion vehicle systems as well as the human system with regard to the effect of stable 2 in order to determine if an up-righting response time greater than 60 seconds could be tolerated. The following report focuses on the assessment of the human system in the posture assumed when Orion is in the stable 2 configuration. Stable 2 will place suited, seated, and restrained crewmembers in a prone (facedown), head-up position for a period of time dependent on the functionality of the up-righting systems, ability of the crew to release themselves from the seat and restraints, and/or time to arrival of rescue forces. Given that the Orion seat and restraint system design is not complete and therefore, not available for evaluation, Space Medicine assessed how long a healthy but deconditioned crewmember could stay in this prone, restrained position and the physiological consequences of this posture by researching terrestrial analogs and considered the known physiological alterations and deconditioning experienced by long duration crewmembers.

Femoral loading mechanics in the Virginia opossum, Didelphis virginiana: torsion and mediolateral bending in mammalian locomotion.

PubMed

Gosnell, W Casey; Butcher, Michael T; Maie, Takashi; Blob, Richard W

2011-10-15

Studies of limb bone loading in terrestrial mammals have typically found anteroposterior bending to be the primary loading regime, with torsion contributing minimally. However, previous studies have focused on large, cursorial eutherian species in which the limbs are held essentially upright. Recent in vivo strain data from the Virginia opossum (Didelphis virginiana), a marsupial that uses a crouched rather than an upright limb posture, have indicated that its femur experiences appreciable torsion during locomotion as well as strong mediolateral bending. The elevated femoral torsion and strong mediolateral bending observed in D. virginiana might result from external forces such as a medial inclination of the ground reaction force (GRF), internal forces deriving from a crouched limb posture, or a combination of these factors. To evaluate the mechanism underlying the loading regime of opossum femora, we filmed D. virginiana running over a force platform, allowing us to measure the magnitude of the GRF and its three-dimensional orientation relative to the limb, facilitating estimates of limb bone stresses. This three-dimensional analysis also allows evaluations of muscular forces, particularly those of hip adductor muscles, in the appropriate anatomical plane to a greater degree than previous two-dimensional analyses. At peak GRF and stress magnitudes, the GRF is oriented nearly vertically, inducing a strong abductor moment at the hip that is countered by adductor muscles on the medial aspect of the femur that place this surface in compression and induce mediolateral bending, corroborating and explaining loading patterns that were identified in strain analyses. The crouched orientation of the femur during stance in opossums also contributes to levels of femoral torsion as high as those seen in many reptilian taxa. Femoral safety factors were as high as those of non-avian reptiles and greater than those of upright, cursorial mammals, primarily because the load magnitudes experienced by opossums are lower than those of most mammals. Thus, the evolutionary transition from crouched to upright posture in mammalian ancestors may have been accompanied by an increase in limb bone load magnitudes.

Beat-by-beat analysis of cardiac output and blood pressure responses to short-term barostimulation in different body positions

NASA Astrophysics Data System (ADS)

Hildebrandt, Wulf; Schütze, Harald; Stegemann, J.

Rapid quantification of the human baro-reflex control of heart rate has been achieved on a beat-by-beat basis using a neck-chamber with quick ECG-triggered pressure changes. Referring to recent findings on heart rate and stroke volume, the present study uses this technique to compare cardiac output as well as blood pressure changes in supine and upright position to investigate feedback effects and to confirm postural reflex modifications not revealed by RR-interval changes. A suction profile starting at +40 mmHg and running 7 steps of pressure decrease down to -65 mmHg was examined in 0° and 90° tilting position while beat-by-beat recordings were done of heart rate, stroke volume (impedance-cardiography) and blood pressure (Finapres tm) (n=16). The percentual heart rate decrease failed to be significantly different between positions. A suction-induced stroke volume increase led to a cardiac output almost maintained when supine and significantly increased when upright. A decrease in all blood pressure values was found during suction, except for systolic values in upright position which increased. Conclusively, (a) it is confirmed that different inotropy accounts for the seen gravitational effect on the cardiac output not represented by heart rate; (b) identical suction levels in different positions lead to different stimuli at the carotid receptor. This interference has to be considered in microgravity studies by beat-by-beat measurement of cardiac output and blood pressure.

The mechanical effect of anterior pelvic tilt taping on slump sitting by seated workers.

PubMed

Lee, Jung-Hoon; Yoo, Won-Gyu

2011-01-01

The objectives of this study were to determine whether there is a change in the pelvic inclination after about 30 min of slump sitting by seated workers, and if so, to determine whether these changes can be prevented by the application of anterior pelvic tilt taping (APTT). The subjects who consented to participate in the experiment were randomly allocated to two groups: no-APTT group and APTT group. The no-APTT group performed slump sitting for 30 min, and the both pelvic inclinations were remeasured. In the APTT group, the both pelvic inclinations were measured immediately after the application of the APTT, and then again after 30 min of slump sitting. The both pelvic inclinations in the no-APTT group were significantly decreased (p<0.05) after they returned to the upright standing posture. The both pelvic inclinations in the APTT group were significantly increased immediately after the APTT (p<0.05), and this increase was maintained when returning to the upright standing posture after 30 min of slump sitting (p>0.05). We suggest that APTT can be applied as an auxiliary treatment method for preventing changes in pelvic inclination and musculoskeletal problems of low back area by awkward sitting posture in the seated worker.

The effects of prosthetic foot type and visual alteration on postural steadiness in below-knee amputees

PubMed Central

2014-01-01

Background Achieving independent upright posture has known to be one of the main goals in rehabilitation following lower limb amputation. The purpose of this study was to compare postural steadiness of below knee amputees with visual alterations while wearing three different prosthetic feet. Methods Ten male below-knee amputees were instructed to stand quietly on the Biodex® balance platform while wearing solid ankle cushion heel (SACH), single axis (SA) and energy storage and release (ESAR) prosthetic foot under different visual input conditions (eyes-opened and eyes-closed). The overall stability index (OSI), anterior- posterior stability index (APSI), and medial-lateral stability index (MLSI) were computed. Perceived balance assessment of each foot was evaluated using Activities-specific Balance Confidence (ABC) score. Results The findings highlights that SACH showed lowest overall stability index (indicating less body sway) during eyes-opened (OSI: SACH = 1.09, SA = 1.58, ESAR = 1.59) and SA showed lowest overall stability index during eyes-closed (OSI: SACH = 2.52, SA = 2.30, ESAR = 2.76) condition. However, overall stability indexes between foot types did not differ significantly during eyes-opened or eyes-closed (p = 0.651). There was a trend of instability which occurred more in medial-lateral compared to anterior-posterior direction for all foot types, with significant result in ESAR foot(eyes-opened: MLSI = 1.59, APSI = 0.65, p = 0.034; eyes-closed: MLSI = 2.76, APSI = 1.80, p = 0.017, respectively). When comparing between visual conditions, stability score was significantly higher during eyes-closed compared to eyes-opened situations for SACH and ESAR foot (eyes-closed vs opened; SACH OSI: 3.43 vs 1.71, p = 0.018 and MLSI: 3.43 vs 1.71, p = 0.018; ESAR OSI: 3.58 vs 1.86, p = 0.043 and APSI: 1.80 vs 0.65, p = 0.027). Conclusions The results of this study suggested postural steadiness in below-knee amputees was not affected by the types of prosthetic foot during quiet upright standing, but was significantly affected when visual cues was absent. PMID:24597518

The influence of changes in trunk and pelvic posture during single leg standing on hip and thigh muscle activation in a pain free population.

PubMed

Prior, Simon; Mitchell, Tim; Whiteley, Rod; O'Sullivan, Peter; Williams, Benjamin K; Racinais, Sebastien; Farooq, Abdulaziz

2014-03-27

Thigh muscle injuries commonly occur during single leg loading tasks and patterns of muscle activation are thought to contribute to these injuries. The influence trunk and pelvis posture has on hip and thigh muscle activation during single leg stance is unknown and was investigated in a pain free population to determine if changes in body posture result in consistent patterns of changes in muscle activation. Hip and thigh muscle activation patterns were compared in 22 asymptomatic, male subjects (20-45 years old) in paired functionally relevant single leg standing test postures: Anterior vs. Posterior Trunk Sway; Anterior vs. Posterior Pelvic Rotation; Left vs. Right Trunk Shift; and Pelvic Drop vs. Raise. Surface EMG was collected from eight hip and thigh muscles calculating Root Mean Square. EMG was normalized to an "upright standing" reference posture. Repeated measures ANOVA was performed along with associated F tests to determine if there were significant differences in muscle activation between paired test postures. In right leg stance, Anterior Trunk Sway (compared to Posterior Sway) increased activity in posterior sagittal plane muscles, with a concurrent deactivation of anterior sagittal plane muscles (p: 0.016 - <0.001). Lateral hip abductor muscles increased activation during Left Trunk Shift (compared to Right) (p :≤ 0.001). Lateral Pelvic Drop (compared to Raise) decreased activity in hip abductors and increased hamstring, adductor longus and vastus lateralis activity (p: 0.037 - <0.001). Changes in both trunk and pelvic posture during single leg stance generally resulted in large, predictable changes in hip and thigh muscle activation in asymptomatic young males. Changes in trunk position in the sagittal plane and pelvis position in the frontal plane had the greatest effect on muscle activation. Investigation of these activation patterns in clinical populations such as hip and thigh muscle injuries may provide important insights into injury mechanisms and inform rehabilitation strategies.

Learning an Intermittent Control Strategy for Postural Balancing Using an EMG-Based Human-Computer Interface

PubMed Central

Asai, Yoshiyuki; Tateyama, Shota; Nomura, Taishin

2013-01-01

It has been considered that the brain stabilizes unstable body dynamics by regulating co-activation levels of antagonist muscles. Here we critically reexamined this established theory of impedance control in a postural balancing task using a novel EMG-based human-computer interface, in which subjects were asked to balance a virtual inverted pendulum using visual feedback information on the pendulum's position. The pendulum was actuated by a pair of antagonist joint torques determined in real-time by activations of the corresponding pair of antagonist ankle muscles of subjects standing upright. This motor-task raises a frustrated environment; a large feedback time delay in the sensorimotor loop, as a source of instability, might favor adopting the non-reactive, preprogrammed impedance control, but the ankle muscles are relatively hard to co-activate, which hinders subjects from adopting the impedance control. This study aimed at discovering how experimental subjects resolved this frustrated environment through motor learning. One third of subjects adapted to the balancing task in a way of the impedance-like control. It was remarkable, however, that the majority of subjects did not adopt the impedance control. Instead, they acquired a smart and energetically efficient strategy, in which two muscles were inactivated simultaneously at a sequence of optimal timings, leading to intermittent appearance of periods of time during which the pendulum was not actively actuated. Characterizations of muscle inactivations and the pendulum¡Çs sway showed that the strategy adopted by those subjects was a type of intermittent control that utilizes a stable manifold of saddle-type unstable upright equilibrium that appeared in the state space of the pendulum when the active actuation was turned off. PMID:23717398

Effects of external loads on balance control during upright stance: experimental results and model-based predictions.

PubMed

Qu, Xingda; Nussbaum, Maury A

2009-01-01

The purpose of this study was to identify the effects of external loads on balance control during upright stance, and to examine the ability of a new balance control model to predict these effects. External loads were applied to 12 young, healthy participants, and effects on balance control were characterized by center-of-pressure (COP) based measures. Several loading conditions were studied, involving combinations of load mass (10% and 20% of individual body mass) and height (at or 15% of stature above the whole-body COM). A balance control model based on an optimal control strategy was used to predict COP time series. It was assumed that a given individual would adopt the same neural optimal control mechanisms, identified in a no-load condition, under diverse external loading conditions. With the application of external loads, COP mean velocity in the anterior-posterior direction and RMS distance in the medial-lateral direction increased 8.1% and 10.4%, respectively. Predicted COP mean velocity and RMS distance in the anterior-posterior direction also increased with external loading, by 11.1% and 2.9%, respectively. Both experimental COP data and model-based predictions provided the same general conclusion, that application of larger external loads and loads more superior to the whole body center of mass lead to less effective postural control and perhaps a greater risk of loss of balance or falls. Thus, it can be concluded that the assumption about consistency in control mechanisms was partially supported, and it is the mechanical changes induced by external loads that primarily affect balance control.

Validity and reliability of the activPAL3 for measuring posture and stepping in adults and young people.

PubMed

Sellers, Ceri; Dall, Philippa; Grant, Margaret; Stansfield, Ben

2016-01-01

Characterisation of free-living physical activity requires the use of validated and reliable monitors. This study reports an evaluation of the validity and reliability of the activPAL3 monitor for the detection of posture and stepping in both adults and young people. Twenty adults (median 27.6y; IQR22.6y) and 8 young people (12.0y; IQR4.1y) performed standardised activities and activities of daily living (ADL) incorporating sedentary, upright and stepping activity. Agreement, specificity and positive predictive value were calculated between activPAL3 outcomes and the gold-standard of video observation. Inter-device reliability was calculated between 4 monitors. Sedentary and upright times for standardised activities were within ±5% of video observation as was step count (excluding jogging) for both adults and young people. Jogging step detection accuracy reduced with increasing cadence >150stepsmin(-1). For ADLs, sensitivity to stepping was very low for adults (40.4%) but higher for young people (76.1%). Inter-device reliability was either good (ICC(1,1)>0.75) or excellent (ICC(1,1)>0.90) for all outcomes. An excellent level of detection of standardised postures was demonstrated by the activPAL3. Postures such as seat-perching, kneeling and crouching were misclassified when compared to video observation. The activPAL3 appeared to accurately detect 'purposeful' stepping during ADL, but detection of smaller stepping movements was poor. Small variations in outcomes between monitors indicated that differences in monitor placement or hardware may affect outcomes. In general, the detection of posture and purposeful stepping with the activPAL3 was excellent indicating that it is a suitable monitor for characterising free-living posture and purposeful stepping activity in healthy adults and young people. Copyright © 2015 Elsevier B.V. All rights reserved.

Acute Cutaneous Microvascular Flow Responses to Whole-Body Tilting in Humans

NASA Technical Reports Server (NTRS)

Breit, Gregory A.; Watenpaugh, Donald E.; Ballard, Richard E.; Hargens, Alan R.

1993-01-01

The transition from upright to head-down tilt (HDT) posture in humans increases blood pressure superior to the heart and decreases pressure inferior to the heart. Consequently, above heart level, myogenic arteriolar tone probably increases with HDT, in opposition to the withdrawal of baroreceptor-mediated sympathetic tone. We hypothesized that due to antagonism between central and local controls, the response of the facial cutaneous micro- circulation to acute postural change will be weaker than that in the leg, where these two mechanisms reinforce each other. Cutaneous microvascular flow was measured by laser Doppler flowmetry simultaneously at the shin and the neck of 7 male and 3 female subjects. Subjects underwent a stepwise tilt protocol from standing control to 54 deg head-up tilt (HUT), 30 deg, 12 deg, 0 deg, -6 deg (HDT), -12 deg, -6 deg, 0 deg, 12 deg, 30 deg, 54 deg, and standing, for 30-sec periods with 10-sec transitions between postures. Flows at the shin and the neck increased significantly (P < 0.05) from standing baseline to 12 deg HUT (252 +/- 55 and 126 +/- 9% (bar-X +/- SE) of baseline, respectively). From 12 deg to -12 deg tilt, flows continued to increase at the shin (509 +/- 71% of baseline) but decreased at the neck to baseline levels (100 +/- 15% of baseline). Cutaneous microvascular flow recovered at both sites during the return to standing posture with significant hysteresis. Flow increases from standing to near-supine posture are attributed at both sites to baroreceptor-mediated vasodilation. The great dissimilarity in flow response magnitudes at the two measurement sites may be indicative of central/local regulatory antagonism above heart level and reinforcement below heart level.

Acute Cutaneous Microvascular Flow Responses to Whole-Body Tilting in Humans

NASA Technical Reports Server (NTRS)

Breit, Gregory A.; Watenpaugh, Donald E.; Ballard, Richard E.; Hargens, Alan R.

1993-01-01

The transition from upright to head-down tilt (HDT) posture in humans increases blood pressure superior to the heart and decreases pressure inferior to the heart. Consequently, above heart level, myogenic arteriolar tone probably increases with HDT, in opposition to the withdrawal of baroreceptor-mediated sympathetic tone. We hypothesized that due to antagonism between central and local controls, the response of the facial cutaneous microcirculation to acute postural change will be weaker than that in the leg, where these two mechanisms reinforce each other. Cutaneous microvascular flow was measured by laser Doppler flowmetry simultaneously at the shin and the neck of 7 male and 3 female subjects. Subjects underwent a stepwise tilt protocol from standing control to 54 deg head-up tilt (HUT), 30 deg, 12 deg, O deg, -6 deg (HDT), -12 deg, -6 deg, O deg, 12 deg, 30 deg, 54 deg, and standing, for 30-sec periods with 10-sec transitions between postures. Flows at the shin and the neck increased significantly (P less than 0.05) from standing baseline to 12 deg HUT (252 +/- 55 and 126 +/- 9% (bar X +/- SE) of baseline, respectively). From 12 deg to -12 deg tilt, flows continued to increase at the shin (509 +/- 71% of baseline) but decreased at the neck to baseline levels (100 +/- 15% of baseline). Cutaneous microvascular flow recovered at both sites during the return to standing posture with significant hysteresis. Flow increases from standing to near-supine posture are attributed at both sites to baroreceptor-mediated vasodilation. The great dissimilarity in flow response magnitudes at the two measurement sites may be indicative of central/local regulatory antagonism above heart level and reinforcement below heart level.

Effects of orthostatic hypotension on cognition in Parkinson disease

PubMed Central

Centi, Justin; Freeman, Roy; Gibbons, Christopher H.; Neargarder, Sandy; Canova, Alexander O.

2017-01-01

Objective: To investigate the relation between orthostatic hypotension (OH) and posture-mediated cognitive impairment in Parkinson disease (PD) using a cross-sectional and within-group design. Methods: Individuals without dementia with idiopathic PD included 18 with OH (PDOH) and 19 without OH; 18 control participants were also included. Neuropsychological tests were conducted in supine and upright-tilted positions. Blood pressure was assessed in each posture. Results: The PD groups performed similarly while supine, demonstrating executive dysfunction in sustained attention and response inhibition, and reduced semantic fluency and verbal memory (encoding and retention). Upright posture exacerbated and broadened these deficits in the PDOH group to include phonemic fluency, psychomotor speed, and auditory working memory. When group-specific supine scores were used as baseline anchors, both PD groups showed cognitive changes following tilt, with the PDOH group exhibiting a wider range of deficits in executive function and memory as well as significant changes in visuospatial function. Conclusions: Cognitive deficits in PD have been widely reported with assessments performed in the supine position, as seen in both our PD groups. Here we demonstrated that those with PDOH had transient, posture-mediated changes in excess of those found in PD without OH. These observed changes suggest an acute, reversible effect. Understanding the effects of OH due to autonomic failure on cognition is desirable, particularly as neuroimaging and clinical assessments collect data only in the supine or seated positions. Identification of a distinct neuropsychological profile in PD with OH has quality of life implications, and OH presents itself as a possible target for intervention in cognitive disturbance. PMID:27903817

Optimum Design of Anti-Siphon Device used to Prevent Cerebrospinal Fluid from Overdraining

NASA Astrophysics Data System (ADS)

Jang, Jong Yun; Lee, Chong Sun; Suh, Chang Min

The present study investigated design parameters of an anti-siphon device used with shunt valves to treat patients with hydrocephalus. Structural analyses were performed to understand roles of design variables and optimize performance of the diaphragm-type anti-siphon device (hereafter referred to as the ASD). Experiments were performed on the lab-made product and showed good agreements with the numerical simulations. Using the simulations, we were able to design a more physiological ASD which gave equal opening pressures in both supine and upright postures. Tissue encapsulization phenomenon was also simulated and the results indicated underdrainage of CSF in the upright position of the patient.

Beat by beat stroke volume assessment by PDE in upright and supine exercise

NASA Technical Reports Server (NTRS)

1980-01-01

A 3.0 MHz pulse Doppler echocardiograph was used to estimate instantaneous stroke volume and cardiac output in 8 men during steady state supine and upright exercise at 300 kpm/min which were compared with other studies utilizing invasive procedures. The mean transients in heart rate and stroke volume and cardiac output for the first 20 sec of exercise in each posture were then determined. Centerline blood velocities were obtained in the ascending aorta with the transducer positioned manually in the suprasternal notch. Mean supine values for stroke volume and cardiac output at rest and exercise were 111 (6.4) and 112 ml (9.7 L/min), respectively, for supine. The corresponding results for upright were 76 (5.6) and 92 ml (8.4 L/min). These values compare favorably with prior studies. The transient response of cardiac output following the onset of upright was about twice as fast as in S because of the rapid and almost immediate upsurge in stroke volume. In supine, only heart rate served to augment cardiac output as stroke volume initially fell. The faster initial aortic flow in upright must represent the rapid mobilization of pooled venous blood from the leg veins which more than accounts for the additional volume (184 ml) of blood passing through the aorta during upright compared with supine in the first 20 sec.

Forelimb preferences in quadrupedal marsupials and their implications for laterality evolution in mammals.

PubMed

Giljov, Andrey; Karenina, Karina; Malashichev, Yegor

2013-03-06

Acquisition of upright posture in evolution has been argued to facilitate manual laterality in primates. Owing to the high variety of postural habits marsupials can serve as a suitable model to test whether the species-typical body posture shapes forelimb preferences in non-primates or this phenomenon emerged only in the course of primate evolution. In the present study we aimed to explore manual laterality in marsupial quadrupeds and compare them with the results in the previously studied bipedal species. Forelimb preferences were assessed in captive grey short-tailed opossum (Monodelphis domestica) and sugar glider (Petaurus breviceps) in four different types of unimanual behaviour per species, which was not artificially evoked. We examined the possible effects of sex, age and task, because these factors have been reported to affect motor laterality in placental mammals. In both species the direction of forelimb preferences was strongly sex-related. Male grey short-tailed opossums showed right-forelimb preference in most of the observed unimanual behaviours, while male sugar gliders displayed only a slight, not significant rightward tendency. In contrast, females in both species exhibited consistent group-level preference of the left forelimb. We failed to reveal significant differences in manual preferences between tasks of potentially differing complexity: reaching a stable food item and catching live insects, as well as between the body support and food manipulation. No influence of subjects' age on limb preferences was found. The direction of sex-related differences in the manual preferences found in quadrupedal marsupials seems to be not typical for placental mammals. We suggest that the alternative way of interhemispheric connection in absence of corpus callosum may result in a fundamentally distinct mechanism of sex effect on limb preferences in marsupials compared to placentals. Our data confirm the idea that non-primate mammals differ from primates in sensitivity to task complexity. Comparison of marsupial species studied to date indicate that the vertical body orientation and the bipedalism favor the expression of individual- and population-level forelimb preferences in marsupials much like it does in primates. Our findings give the first evidence for the effect of species-typical posture on the manual laterality in non-primate mammals.

Does Bipedality Predict the Group-Level Manual Laterality in Mammals?

PubMed Central

Giljov, Andrey; Karenina, Karina; Malashichev, Yegor

2012-01-01

Background Factors determining patterns of laterality manifestation in mammals remain unclear. In primates, the upright posture favours the expression of manual laterality across species, but may have little influence within a species. Whether the bipedalism acts the same in non-primate mammals is unknown. Our recent findings in bipedal and quadrupedal marsupials suggested that differences in laterality pattern, as well as emergence of manual specialization in evolution might depend on species-specific body posture. Here, we evaluated the hypothesis that the postural characteristics are the key variable shaping the manual laterality expression across mammalian species. Methodology/Principal Findings We studied forelimb preferences in a most bipedal marsupial, brush-tailed bettong, Bettongia penicillata in four different types of unimanual behavior. The significant left-forelimb preference at the group level was found in all behaviours studied. In unimanual feeding on non-living food, catching live prey and nest-material collecting, all or most subjects were lateralized, and among lateralized bettongs a significant majority displayed left-forelimb bias. Only in unimanual supporting of the body in the tripedal stance the distribution of lateralized and non-lateralized individuals did not differ from chance. Individual preferences were consistent across all types of behaviour. The direction or the strength of forelimb preferences were not affected by the animals’ sex. Conclusions/Significance Our findings support the hypothesis that the expression of manual laterality depends on the species-typical postural habit. The interspecies comparison illustrates that in marsupials the increase of bipedality corresponds with the increase of the degree of group-level forelimb preference in a species. Thus, bipedalism can predict pronounced manual laterality at both intra- and interspecific levels in mammals. We also conclude that quadrupedal position in biped species can slightly hinder the expression of manual laterality, but the evoked biped position in quadrupedal species does not necessarily lead to the enhanced manifestation of manual laterality. PMID:23251583

Does bipedality predict the group-level manual laterality in mammals?

PubMed

Giljov, Andrey; Karenina, Karina; Malashichev, Yegor

2012-01-01

Factors determining patterns of laterality manifestation in mammals remain unclear. In primates, the upright posture favours the expression of manual laterality across species, but may have little influence within a species. Whether the bipedalism acts the same in non-primate mammals is unknown. Our recent findings in bipedal and quadrupedal marsupials suggested that differences in laterality pattern, as well as emergence of manual specialization in evolution might depend on species-specific body posture. Here, we evaluated the hypothesis that the postural characteristics are the key variable shaping the manual laterality expression across mammalian species. We studied forelimb preferences in a most bipedal marsupial, brush-tailed bettong, Bettongia penicillata in four different types of unimanual behavior. The significant left-forelimb preference at the group level was found in all behaviours studied. In unimanual feeding on non-living food, catching live prey and nest-material collecting, all or most subjects were lateralized, and among lateralized bettongs a significant majority displayed left-forelimb bias. Only in unimanual supporting of the body in the tripedal stance the distribution of lateralized and non-lateralized individuals did not differ from chance. Individual preferences were consistent across all types of behaviour. The direction or the strength of forelimb preferences were not affected by the animals' sex. Our findings support the hypothesis that the expression of manual laterality depends on the species-typical postural habit. The interspecies comparison illustrates that in marsupials the increase of bipedality corresponds with the increase of the degree of group-level forelimb preference in a species. Thus, bipedalism can predict pronounced manual laterality at both intra- and interspecific levels in mammals. We also conclude that quadrupedal position in biped species can slightly hinder the expression of manual laterality, but the evoked biped position in quadrupedal species does not necessarily lead to the enhanced manifestation of manual laterality.

How Much Gravity Is Needed to Establish the Perceptual Upright?

PubMed Central

Harris, Laurence R.; Herpers, Rainer; Hofhammer, Thomas; Jenkin, Michael

2014-01-01

Might the gravity levels found on other planets and on the moon be sufficient to provide an adequate perception of upright for astronauts? Can the amount of gravity required be predicted from the physiological threshold for linear acceleration? The perception of upright is determined not only by gravity but also visual information when available and assumptions about the orientation of the body. Here, we used a human centrifuge to simulate gravity levels from zero to earth gravity along the long-axis of the body and measured observers' perception of upright using the Oriented Character Recognition Test (OCHART) with and without visual cues arranged to indicate a direction of gravity that differed from the body's long axis. This procedure allowed us to assess the relative contribution of the added gravity in determining the perceptual upright. Control experiments off the centrifuge allowed us to measure the relative contributions of normal gravity, vision, and body orientation for each participant. We found that the influence of 1 g in determining the perceptual upright did not depend on whether the acceleration was created by lying on the centrifuge or by normal gravity. The 50% threshold for centrifuge-simulated gravity's ability to influence the perceptual upright was at around 0.15 g, close to the level of moon gravity but much higher than the threshold for detecting linear acceleration along the long axis of the body. This observation may partially explain the instability of moonwalkers but is good news for future missions to Mars. PMID:25184481

How much gravity is needed to establish the perceptual upright?

PubMed

Harris, Laurence R; Herpers, Rainer; Hofhammer, Thomas; Jenkin, Michael

2014-01-01

Might the gravity levels found on other planets and on the moon be sufficient to provide an adequate perception of upright for astronauts? Can the amount of gravity required be predicted from the physiological threshold for linear acceleration? The perception of upright is determined not only by gravity but also visual information when available and assumptions about the orientation of the body. Here, we used a human centrifuge to simulate gravity levels from zero to earth gravity along the long-axis of the body and measured observers' perception of upright using the Oriented Character Recognition Test (OCHART) with and without visual cues arranged to indicate a direction of gravity that differed from the body's long axis. This procedure allowed us to assess the relative contribution of the added gravity in determining the perceptual upright. Control experiments off the centrifuge allowed us to measure the relative contributions of normal gravity, vision, and body orientation for each participant. We found that the influence of 1 g in determining the perceptual upright did not depend on whether the acceleration was created by lying on the centrifuge or by normal gravity. The 50% threshold for centrifuge-simulated gravity's ability to influence the perceptual upright was at around 0.15 g, close to the level of moon gravity but much higher than the threshold for detecting linear acceleration along the long axis of the body. This observation may partially explain the instability of moonwalkers but is good news for future missions to Mars.

Impaired limb reaction to displacement of center of gravity in rats with unilateral striatal ischemic injury.

PubMed

Nobile, Cameron W; Palmateer, Julie M; Kane, Jackie; Hurn, Patricia D; Schallert, Timothy; Adkins, DeAnna L

2014-10-01

Clinical stroke often results in impaired balance and increased vulnerability to severe injuries due to falling. To evaluate potential preclinical treatments that might target these deficits, it will be important to include tests capable of assessing these impairments chronically in animal models. Previously, we developed a postural instability test (PIT) that revealed chronic, unilateral impairments in postural stability in rat models of hemi-Parkinson's disease (PD) and of unilateral cervical spinal cord injury. Here, we investigated whether this test was also capable of revealing long-term stroke-induced impairments in postural support in rats. Additionally, we examined the ability of more common tests of sensorimotor function to detect chronic impairments. We found that the PIT detected chronic deficits in postural stability/balance enduring for up to 6 weeks post-stroke, outlasting impairments detected in other tests of forelimb sensorimotor function, including asymmetries in upright postural support (cylinder test) and vibrissae-evoked forelimb placing.

How proprioceptive impairments affect quiet standing in patients with multiple sclerosis.

PubMed

Rougier, P; Faucher, M; Cantalloube, S; Lamotte, D; Vinti, M; Thoumie, P

2007-01-01

To assess if multiple sclerosis patients with proprioceptive impairment are specifically affected during quiet standing with eyes open and how they can develop motor compensatory processes, 56 patients, classified from sensory clinical tests as ataxo-spastic (MS-AS) or only having spasticity (MS-S), were compared to 23 healthy adults matched for age. The postural strategies were assessed from the centre-of-pressure trajectories (CP), measured from a force platform in the eyes open standing condition for a single trial lasting 51.2 s. The vertical projection of the centre of gravity (CGv) and its vertical difference from the CP (CP-CGv) were then estimated through a biomechanical relationship. These two movements permit the characterization of the postural performance and the horizontal acceleration communicated to the CG and from that, the global energy expenditure, respectively. Both MS-AS and MS-S groups demonstrate larger CGv and CP-CGv movements than healthy individuals of the same age. Whilst similar CGv values are noticed in both MS subgroups, suggesting similar postural performances, statistically significant differences are observed for the CP-CGv component. Biomechanically, this feature expresses the necessity for the MS-AS group to develop augmented neuro-muscular means to control their body movements, as compared to the MS-S group. By demonstrating for both groups of patients similar postural performance accompanied by a varying degree of energy expenditure to maintain undisturbed upright stance, this study reveals that MS-AS patients which are affected by proprioceptive loss can compensate for this deficit with more efficient control strategies, when standing still with their eyes open.

Immediate effects of plantar inputs on the upper half muscles and upright posture: a preliminary study.

PubMed

Ciuffolo, Fabio; Ferritto, Anna L; Muratore, Filippo; Tecco, Simona; Testa, Mauro; D'Attilio, Michele; Festa, Felice

2006-01-01

This purpose of this study was to investigate the immediate effects of plantar inputs on both the upper half muscle activity (anterior temporal, masseter, digastric, sternocleidomastoid, upper and lower trapezius, cervical) and the body posture, by means of electromyography (EMG) and vertical force platform, respectively. Twenty four (24) healthy adults, between the ages of 24 and 31 years (25.3 +/- 1.9), with no history of craniomandibular disorder or systemic musculoskeletal dysfunction, were randomly divided into two groups: test group (fourteen subjects) and control group (ten subjects). A first recording session (TO) measured the baseline EMG and postural patterns of both groups. After this session, the test group wore test shoes with insoles that stimulated the plantar surfaces, while the control group wore placebo shoes. After one hour, a second set of measurements (T1) were performed. Significant differences between the groups at baseline were observed in the left anterior temporal, left cervical, and left upper trapezius, as well as at T1 in the left anterior temporal and right upper trapezius (p < 0.05). Within-test group analysis showed a significant increase of the right upper trapezius activity (p < 0.05), whereas no changes were found by within-control group analysis. Lower risk of asymmetric muscle patterns and postural blindness in the test group compared to the control group was observed. Further studies are warranted to investigate the short and long-term effects of this type of insole, in patients with both craniomandibular-cervical and lower extremity disorders.

Effects of 30-, 60-, and 90-Day Bed Rest on Postural Control in Men and Women

NASA Technical Reports Server (NTRS)

Esteves, Julie; Taylor, Laura C.; Vanya, Robert D.; Dean, S. Lance; Wood, Scott J.

2011-01-01

INTRODUCTION Head-down-tilt bed rest (HDT) has been used as a safe gr ound-based analog to mimic and develop countermeasures for the physiological effects of spaceflight, including decrements in postural stability. The purpose of this investigation was to characterize the effects of 30-, 60-, and 90-day bed rest on postural control in men and women. METHODS Twenty-nine subjects (18M,11F) underwent 13 days of ambula tory acclimatization and were placed in 6? HDT for 30 (n=12), 60 (n=8), or 90 (n=9) days, followed by 14 days of ambulatory recovery. Computerized dynamic posturography (CDP) was used to assess changes in sensory and motor components of postural control, and recovery after HDT. Sensory Organization Tests (SOTs) objectively evaluate one?s ability to effectively use or suppress visual, vestibular, and proprioceptive information for postural control. Stability during the SOTs was assessed using peak-to-peak sway and convergence toward stability limits to derive an equilibrium score. Motor Control Tests (MCTs) evaluate one?s ability to recover from unexpected support surface perturbations, with performance determined by center-of-pressure path length. Whole-body kinematic data were collected to determine body-sway strategy used to maintain stability during each condition. Baselines were determined pre-HDT. Recovery was tracked post-HDT on days 0, 1, 2, and 4. RESULTS Immediately after HDT, subjects showed decreased performance on most SOTs, primarily on sway-referenced support conditions, typically returning to baseline levels within 4 days. MCT performance was not significantly affected. There were no significant gender or duration differences in performance. Kinematic data revealed a tendency to use ankle strategy to maintain an upright stance during most SOT conditions. Interestingly, six subjects (2M,4F) experienced orthostatic intolerance and were unable to complete day 0 testing. CONCLUSION HDT mimics some un loading mechanisms of spaceflight and elicits orthostatic issues present post-spaceflight (contributing to instability); however, it does not sufficiently address the vestibular dysfunction which occurs post-spaceflight.

Renin stimulation by passive tilting: the influence of an anti-gravity suit on postural changes in plasma renin activity, plasma noradrenaline concentration and kidney function in normal man.

PubMed

Hesse, B; Ring-Larsen, H; Nielsen, I; Christensen, N J

1978-04-01

Plasma renin activity (PRA), plasma noradrenaline concentration, heart rate, blood pressure, and clearances of para-aminohippurate and inulin were measured in twelve normal subjects (clearances in only three subjects) before and after 40 min of 60 degrees upright tilting. The tilting experiments were repeated after inflation of an anti-gravity suit to 60 mmHg on the lower extremities. Inflation of the anti-gravity suit caused an abolition of the postural PRA increase, a marked reduction of the postural increases in plasma noradrenaline and heart rate, and elimination of the decreases in pulse pressure, inulin and para-aminohippurate clearances and sodium excretion. The results suggest a decisive role of the sympathetic nervous system for postural renin increase, probably mainly activated by stretch receptors in the low-pressure cardiopulmoanry area.

The effects of actuator selection on non-volitional postural responses to torso-based vibrotactile stimulation

PubMed Central

2013-01-01

Background Torso-based vibrotactile feedback may significantly reduce postural sway in balance-compromised adults during quiet standing or in response to perturbations. However, natural non-volitional postural responses to vibrotactile stimulation applied to the torso remain unknown. Methods The primary goal of this study was to determine, for two types of actuators (tactors) and in the absence of instruction, whether vibrotactile stimulation induces a directional postural shift as a function of stimulation location. Eleven healthy young adults (20 – 29 years old) were asked to maintain an upright erect posture with feet hip-width apart and eyes closed. Two types of tactors, Tactaid and C2, which differ in design and stimulation strength, were placed on the skin over the right and left external oblique, internal oblique, and erector spinae muscles in a horizontal plane corresponding approximately to the L4/L5 level. Each tactor of the same type was activated twice randomly for each individual location and twice simultaneously for all locations at a frequency of 250 Hz for a period of 5 s. Results Vibration applied over the internal oblique and erector spinae muscle locations induced a postural shift in the direction of the stimulation regardless of the tactor type. For the aforementioned four locations, the root-mean-square (RMS) and power spectral density (PSD) of the body sway in both the A/P and M/L directions were also significantly greater during the vibration than before or after, and were greater for the C2 tactors than for the Tactaid tactors. However, simultaneous activation of all tactors or those over the external oblique muscle locations did not produce significant postural responses regardless of the tactor type. Conclusion The results suggest that the use of a torso-based vibrotactile sensory augmentation display should carefully consider the tactor type as well as the instruction of corrective movements. Attractive instructional cues (“move in the direction of the vibration”) are compatible with the observed non-volitional response to stimulation and may facilitate postural adjustments during vibrotactile biofeedback balance applications. PMID:23406013

Stance Postural Strategies in Patients with Chronic Inflammatory Demyelinating Polyradiculoneuropathy

PubMed Central

Missori, Paolo; Trompetto, Carlo; Fattapposta, Francesco

2016-01-01

Introduction Polyneuropathy leads to postural instability and an increased risk of falling. We investigated how impaired motor impairment and proprioceptive input due to neuropathy influences postural strategies. Methods Platformless bisegmental posturography data were recorded in healthy subjects and patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Each subject stood on the floor, wore a head and a hip electromagnetic tracker. Sway amplitude and velocity were recorded and the mean direction difference (MDD) in the velocity vector between trackers was calculated as a flexibility index. Results Head and hip postural sway increased more in patients with CIDP than in healthy controls. MDD values reflecting hip strategies also increased more in patients than in controls. In the eyes closed condition MDD values in healthy subjects decreased but in patients remained unchanged. Discussion Sensori-motor impairment changes the balance between postural strategies that patients adopt to maintain upright quiet stance. Motor impairment leads to hip postural strategy overweight (eyes open), and prevents strategy re-balancing when the sensory context predominantly relies on proprioceptive input (eyes closed). PMID:26977594

Leisure sports and postural control: can a black belt protect your balance from aging?

PubMed

Krampe, Ralf T; Smolders, Caroline; Doumas, Michail

2014-03-01

To determine potential benefits of intensive leisure sports for age-related changes in postural control, we tested 3 activity groups comprising 70 young (M = 21.67 years, SD = 2.80) and 73 older (M = 62.60 years, SD = 5.19) men. Activity groups were martial artists, who held at least 1st Dan (black belt), sportive individuals exercising sports without explicit balance components, and nonsportive controls. Martial artists had an advantage over sportive individuals in dynamic posture tasks (upright stance on a sway-referenced platform), and these 2 active groups showed better postural control than nonsportive participants. Age-related differences in postural control were larger in nonsportive men compared with the 2 active groups, who were similar in this respect. In contrast, negative age differences in other sensorimotor and cognitive functions did not differ between activity groups. We concluded that individuals engaging in intensive recreational sports have long-term advantages in postural control. However, even in older martial artists with years of practice in their sports, we observed considerable differences favoring the young. (c) 2014 APA, all rights reserved.

Influence of gymnastics training on the development of postural control.

PubMed

Garcia, Claudia; Barela, José Angelo; Viana, André Rocha; Barela, Ana Maria Forti

2011-03-29

This study investigated the influence of gymnastics training on the postural control of children with and without the use of visual information. Two age groups, aged 5-7 and 9-11 years old, of gymnasts and nongymnasts were asked to maintain an upright and quiet stance on a force platform with eyes open (EO) and eyes closed (EC) for 30s. Area of the stabilogram (AOS) and mean velocity of the center of pressure (COP) in anterior-posterior (AP) and medial-lateral (ML) directions were calculated and used to investigate the effects of gymnastics training, age, and visual information. Younger gymnasts presented greater postural control compared to younger nongymnasts while visual information did not improve postural control in younger nongymnasts. Younger gymnasts displayed improved postural control with EO compared to EC. The mean velocity of the COP in the ML direction was: less for younger gymnasts than younger nongymnasts with EO. These results suggest that gymnastics training promotes improvements in postural control of younger children only, which results from their use of visual information when available. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

The validity of the first and second generation Microsoft Kinect™ for identifying joint center locations during static postures.

PubMed

Xu, Xu; McGorry, Raymond W

2015-07-01

The Kinect™ sensor released by Microsoft is a low-cost, portable, and marker-less motion tracking system for the video game industry. Since the first generation Kinect sensor was released in 2010, many studies have been conducted to examine the validity of this sensor when used to measure body movement in different research areas. In 2014, Microsoft released the computer-used second generation Kinect sensor with a better resolution for the depth sensor. However, very few studies have performed a direct comparison between all the Kinect sensor-identified joint center locations and their corresponding motion tracking system-identified counterparts, the result of which may provide some insight into the error of the Kinect-identified segment length, joint angles, as well as the feasibility of adapting inverse dynamics to Kinect-identified joint centers. The purpose of the current study is to first propose a method to align the coordinate system of the Kinect sensor with respect to the global coordinate system of a motion tracking system, and then to examine the accuracy of the Kinect sensor-identified coordinates of joint locations during 8 standing and 8 sitting postures of daily activities. The results indicate the proposed alignment method can effectively align the Kinect sensor with respect to the motion tracking system. The accuracy level of the Kinect-identified joint center location is posture-dependent and joint-dependent. For upright standing posture, the average error across all the participants and all Kinect-identified joint centers is 76 mm and 87 mm for the first and second generation Kinect sensor, respectively. In general, standing postures can be identified with better accuracy than sitting postures, and the identification accuracy of the joints of the upper extremities is better than for the lower extremities. This result may provide some information regarding the feasibility of using the Kinect sensor in future studies. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Apparent mass of the human body in the vertical direction: Effect of a footrest and a steering wheel

NASA Astrophysics Data System (ADS)

Toward, M. G. R.; Griffin, M. J.

2010-04-01

The apparent mass of the seated human body influences the vibration transmitted through a car seat. The apparent mass of the body is known to be influenced by sitting posture but the influence of the position of the hands and the feet is not well understood. This study was designed to quantify the influence of steering wheel location and the position of a footrest on the vertical apparent mass of the human body. The influences of the forces applied by the hands to a steering wheel and by the feet to a footrest were also investigated. Twelve subjects were exposed to whole-body vertical random vibration (1.0 m s -2 rms over the frequency range 0.13-40.0 Hz) while supported by a rigid seat with a backrest reclined to 15°. The apparent mass of the body was measured with five horizontal positions and three vertical positions of a steering wheel and also with hands in the lap, and with five horizontal positions of a footrest. The influence of five forward forces (0, 50, 100, 150, 200 N) applied separately to the 'steering wheel' and the footrest were also investigated as well as a 'no backrest' condition. With their hands in their laps, subjects exhibited a resonance around 6.7 Hz, compared to 4.8 Hz when sitting upright with no backrest. In the same posture holding a steering wheel, the mass supported on the seat surface decreased and there was an additional resonance at 4 Hz. Moving the steering wheel away from the body reduced the apparent mass at the primary resonance frequency and increased the apparent mass around the 4 Hz resonance. As the feet moved forward, the mass supported on the seat surface decreased, indicating that the backrest and footrest supported a greater proportion of the subject weight. Applying force to either the steering wheel or the footrest reduced the apparent mass at resonance and decreased the mass supported on the seat surface. It is concluded that the positions and contact conditions of the hands and the feet affect the biodynamic response of the body in a car driving posture. As the biodynamic response influences the vibration transmitted through seats, these factors should be considered in dynamic models of vehicle seating.

A comparison of head motion and prefrontal haemodynamics during upright and recumbent cycling exercise.

PubMed

Tempest, Gavin D; Eston, Roger G; Parfitt, Gaynor

2017-11-01

The aim of this observational study was to compare head motion and prefrontal haemodynamics during exercise using three commercial cycling ergometers. Participants (n = 12) completed an incremental exercise test to exhaustion during upright, recumbent and semi-recumbent cycling. Head motion (using accelerometry), physiological data (oxygen uptake, end-tidal carbon dioxide [P ET CO 2 ] and heart rate) and changes in prefrontal haemodynamics (oxygenation, deoxygenation and blood volume using near infrared spectroscopy [NIRS]) were recorded. Despite no difference in oxygen uptake and heart rate, head motion was higher and P ET CO 2 was lower during upright cycling at maximal exercise (P<0·05). Analyses of covariance (covariates: head motion P>0·05; P ET CO 2 , P<0·01) revealed that prefrontal oxygenation was higher during semi-recumbent than recumbent cycling and deoxygenation and blood volume were higher during upright than recumbent and semi-recumbent cycling (respectively; P<0·05). This work highlights the robustness of the utility of NIRS to head motion and describes the potential postural effects upon the prefrontal haemodynamic response during upright and recumbent cycling exercise. © 2016 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Physiology of prolonged bed rest

NASA Technical Reports Server (NTRS)

Greenleaf, J. E.

1988-01-01

Bed rest has been a normal procedure used by physicians for centuries in the treatment of injury and disease. Exposure of patients to prolonged bed rest in the horizontal position induces adaptive deconditioning responses. While deconditioning responses are appropriate for patients or test subjects in the horizontal position, they usually result in adverse physiological responses (fainting, muscular weakness) when the patient assume the upright posture. These deconditioning responses result from reduction in hydrostatic pressure within the cardiovascular system, virtual elimination of longitudinal pressure on the long bones, some decrease in total body metabolism, changes in diet, and perhaps psychological impact from the different environment. Almost every system in the body is affected. An early stimulus is the cephalic shift of fluid from the legs which increases atrial pressure and induces compensatory responses for fluid and electrolyte redistribution. Without countermeasures, deterioration in strength and muscle function occurs within 1 wk while increased calcium loss may continue for months. Research should also focus on drug and carbohydrate metabolism.

Balance Training Reduces Brain Activity during Motor Simulation of a Challenging Balance Task in Older Adults: An fMRI Study

PubMed Central

Ruffieux, Jan; Mouthon, Audrey; Keller, Martin; Mouthon, Michaël; Annoni, Jean-Marie; Taube, Wolfgang

2018-01-01

Aging is associated with a shift from an automatic to a more cortical postural control strategy, which goes along with deteriorations in postural stability. Although balance training has been shown to effectively counteract these behavioral deteriorations, little is known about the effect of balance training on brain activity during postural tasks in older adults. We, therefore, assessed postural stability and brain activity using fMRI during motor imagery alone (MI) and in combination with action observation (AO; i.e., AO+MI) of a challenging balance task in older adults before and after 5 weeks of balance training. Results showed a nonsignificant trend toward improvements in postural stability after balance training, accompanied by reductions in brain activity during AO+MI of the balance task in areas relevant for postural control, which have been shown to be over-activated in older adults during (simulation of) motor performance, including motor, premotor, and multisensory vestibular areas. This suggests that balance training may reverse the age-related cortical over-activations and lead to changes in the control of upright posture toward the one observed in young adults. PMID:29472847

Postural control in man: the phylogenetic perspective.

PubMed

Gramsbergen, Albert

2005-01-01

Erect posture in man is a recent affordance from an evolutionary perspective. About eight million years ago, the stock from which modern humans derived split off from the ape family, and from around sixty-thousand years ago, modern man developed. Upright gait and manipulations while standing pose intricate cybernetic problems for postural control. The trunk, having an older evolutionary history than the extremities, is innervated by medially descending motor systems and extremity muscles by the more recent, laterally descending systems. Movements obviously require concerted actions from both systems. Research in rats has demonstrated the interdependencies between postural control and the development of fluent walking. Only 15 days after birth, adult-like fluent locomotion emerges and is critically dependent upon postural development. Vesttibular deprivation induces a retardation in postural development and, consequently, a retarded development of adult-like locomotion. The cerebellum obviously has an important role in mutual adjustments in postural control and extremity movements, or, in coupling the phylogenetic older and newer structures. In the human, the cerebellum develops partly after birth and therefore is vulnerable to adverse perinatal influences. Such vulnerability seems to justify focusing our scientific research efforts onto the development of this structure.

Balance Training Reduces Brain Activity during Motor Simulation of a Challenging Balance Task in Older Adults: An fMRI Study.

PubMed

Ruffieux, Jan; Mouthon, Audrey; Keller, Martin; Mouthon, Michaël; Annoni, Jean-Marie; Taube, Wolfgang

2018-01-01

Aging is associated with a shift from an automatic to a more cortical postural control strategy, which goes along with deteriorations in postural stability. Although balance training has been shown to effectively counteract these behavioral deteriorations, little is known about the effect of balance training on brain activity during postural tasks in older adults. We, therefore, assessed postural stability and brain activity using fMRI during motor imagery alone (MI) and in combination with action observation (AO; i.e., AO+MI) of a challenging balance task in older adults before and after 5 weeks of balance training. Results showed a nonsignificant trend toward improvements in postural stability after balance training, accompanied by reductions in brain activity during AO+MI of the balance task in areas relevant for postural control, which have been shown to be over-activated in older adults during (simulation of) motor performance, including motor, premotor, and multisensory vestibular areas. This suggests that balance training may reverse the age-related cortical over-activations and lead to changes in the control of upright posture toward the one observed in young adults.

Cortical mechanisms underlying sensorimotor enhancement promoted by walking with haptic inputs in a virtual environment.

PubMed

Sangani, Samir; Lamontagne, Anouk; Fung, Joyce

2015-01-01

Sensorimotor integration is a complex process in the central nervous system that produces task-specific motor output based on selective and rapid integration of sensory information from multiple sources. This chapter reviews briefly the role of haptic cues in postural control during tandem stance and locomotion, focusing on sensorimotor enhancement of locomotion post stroke. The use of mixed-reality systems incorporating both haptic cues and virtual reality technology in gait rehabilitation post stroke is discussed. Over the last decade, researchers and clinicians have shown evidence of cerebral reorganization that underlies functional recovery after stroke based on results from neuroimaging techniques such as positron emission tomography and functional magnetic resonance imaging. These imaging modalities are however limited in their capacity to measure cortical changes during extensive body motions in upright stance. Functional near-infrared spectroscopy (fNIRS) on the other hand provides a unique opportunity to measure cortical activity associated with postural control during locomotion. Evidence of cortical changes associated with sensorimotor enhancement induced by haptic touch during locomotion is revealed through fNIRS in a pilot study involving healthy individuals and a case study involving a chronic stroke patient. © 2015 Elsevier B.V. All rights reserved.

Renin-angiotensin-aldosterone system in normal and hypertensive pregnancy. Response to postural stimuli.

PubMed

Fagundes, V G; Lamas, C C; Francischetti, E A

1992-02-01

Most studies that have attempted to distinguish pregnancy-induced hypertension from chronic hypertension in pregnancy include arbitrary clinical definitions and morphological reports based on renal biopsy. To evaluate whether these conditions have different responses to stimuli to the renin-angiotensin-aldosterone system, we studied four normal nonpregnant women, eight normal pregnant women, 10 women with pregnancy-induced hypertension, and 14 with chronic hypertension in pregnancy, in the third trimester of pregnancy, after they had sequentially adopted the supine, the left lateral recumbent, and the orthostatic positions for 90 minutes each. Postural maneuvers did not significantly change mean arterial pressure in pregnancy-induced hypertensive or in normal pregnant women, although in chronic hypertensive women, a significant reduction in this parameter was observed in left lateral recumbency. The renin-angiotensin-aldosterone system was significantly less activated with women in the supine position in pregnancy-induced hypertensive and chronic hypertensive women; however, as opposed to pregnancy-induced hypertensive women, those with chronic hypertension reassumed their humoral response to upright posture, which was accompanied by a significant reduction in sodium excretion. The parallelism between plasma renin activity and aldosterone levels, absent in normal pregnancy, returned in pregnancy-induced hypertensive and chronic hypertensive women in the erect posture (r = 0.73, p less than 0.01; r = 0.68, p less than 0.01, respectively). These data suggest that the adoption of the left lateral recumbent position in pregnancy reduces mean arterial pressure only in chronic hypertensive women. Moreover, in chronic hypertension, the upright position provoked a significant response of the renin-angiotensin-aldosterone system. This effect was not observed in women with pregnancy-induced hypertension.

An adaptive technique for multiscale approximate entropy (MAEbin) threshold (r) selection: application to heart rate variability (HRV) and systolic blood pressure variability (SBPV) under postural stress.

PubMed

Singh, Amritpal; Saini, Barjinder Singh; Singh, Dilbag

2016-06-01

Multiscale approximate entropy (MAE) is used to quantify the complexity of a time series as a function of time scale τ. Approximate entropy (ApEn) tolerance threshold selection 'r' is based on either: (1) arbitrary selection in the recommended range (0.1-0.25) times standard deviation of time series (2) or finding maximum ApEn (ApEnmax) i.e., the point where self-matches start to prevail over other matches and choosing the corresponding 'r' (rmax) as threshold (3) or computing rchon by empirically finding the relation between rmax, SD1/SD2 ratio and N using curve fitting, where, SD1 and SD2 are short-term and long-term variability of a time series respectively. None of these methods is gold standard for selection of 'r'. In our previous study [1], an adaptive procedure for selection of 'r' is proposed for approximate entropy (ApEn). In this paper, this is extended to multiple time scales using MAEbin and multiscale cross-MAEbin (XMAEbin). We applied this to simulations i.e. 50 realizations (n = 50) of random number series, fractional Brownian motion (fBm) and MIX (P) [1] series of data length of N = 300 and short term recordings of HRV and SBPV performed under postural stress from supine to standing. MAEbin and XMAEbin analysis was performed on laboratory recorded data of 50 healthy young subjects experiencing postural stress from supine to upright. The study showed that (i) ApEnbin of HRV is more than SBPV in supine position but is lower than SBPV in upright position (ii) ApEnbin of HRV decreases from supine i.e. 1.7324 ± 0.112 (mean ± SD) to upright 1.4916 ± 0.108 due to vagal inhibition (iii) ApEnbin of SBPV increases from supine i.e. 1.5535 ± 0.098 to upright i.e. 1.6241 ± 0.101 due sympathetic activation (iv) individual and cross complexities of RRi and systolic blood pressure (SBP) series depend on time scale under consideration (v) XMAEbin calculated using ApEnmax is correlated with cross-MAE calculated using ApEn (0.1-0.26) in steps of 0.02 at each time scale in supine and upright position and is concluded that ApEn0.26 has highest correlation at most scales (vi) choice of 'r' is critical in interpreting interactions between RRi and SBP and in ascertaining true complexity of the individual RRi and SBP series.

[What compensatory motor strategies do patients with multiple sclerosis develop for balance control?].

PubMed

Rougier, P; Thoumie, P; Cantalloube, S; Lamotte, D

2007-11-01

One of the main features of multiple sclerosis (MS) is the deterioration of motor pathway axons, and in some cases, sensory system axons. Consequently, experimental sensori-motor testing with the undisturbed upright stance paradigm might be useful. It can be hypothesized that the postural strategies could be differently affected depending on the degree of dysfunction of both sensory and motor tracts. Twelve and fifteen patients, classified from sensory clinical tests as ataxo-spastic (SEP-AS) or only spastic (SEP-S), respectively were included in this study and compared to 12 healthy adults matched for age. The postural strategies were assessed from the centre of pressure trajectories (CP), measured from the force platform on which the subjects were instructed to stand upright eyes open for a trial lasting 51.2 s. biomechanical modelling was applied to these trajectories to compute the movements of the centre of gravity (CG) and consequently, the vertical difference between the CP and then the CP-CG, two elementary movements known to characterize postural performance movements for CGv and horizontal acceleration communicated to the CG for the CP-CG movements, and consequently overall neuro-muscular activity. To estimate the relative contribution of each of these elementary movements, an analysis based on frequency parameters (RMS and MF) was conducted. Both SEP-AS and SEP-S groups demonstrate larger CG and CP-CG movements than the age paired individuals. However, some statistically significant differences has to be emphasised between the two MS subgroups but only for the CP-CG component: the RMS of these movements are largely increased for the SEP-AS group, as compared to the SEP-S one. Biomechanically, this feature expresses the necessity for these very patients to produce exaggerated horizontal forces, and thus an increased energy expenditure, to handle the CG movements. The lack of effect observed for the CG movements underlines the capacity for the SEP-AS group to set appropriate control mechanisms for counteracting these less favourable initial conditions. By demonstrating specific trends in the postural organisation aimed at controlling undisturbed upright stance maintenance, this study can be of interest for the practitioner by legitimating this experimental paradigm as a simple and non invasive way to diagnose appropriately the sensori-motor deficiency.

Sensorimotor integration in human postural control

NASA Technical Reports Server (NTRS)

Peterka, R. J.

2002-01-01

It is generally accepted that human bipedal upright stance is achieved by feedback mechanisms that generate an appropriate corrective torque based on body-sway motion detected primarily by visual, vestibular, and proprioceptive sensory systems. Because orientation information from the various senses is not always available (eyes closed) or accurate (compliant support surface), the postural control system must somehow adjust to maintain stance in a wide variety of environmental conditions. This is the sensorimotor integration problem that we investigated by evoking anterior-posterior (AP) body sway using pseudorandom rotation of the visual surround and/or support surface (amplitudes 0.5-8 degrees ) in both normal subjects and subjects with severe bilateral vestibular loss (VL). AP rotation of body center-of-mass (COM) was measured in response to six conditions offering different combinations of available sensory information. Stimulus-response data were analyzed using spectral analysis to compute transfer functions and coherence functions over a frequency range from 0.017 to 2.23 Hz. Stimulus-response data were quite linear for any given condition and amplitude. However, overall behavior in normal subjects was nonlinear because gain decreased and phase functions sometimes changed with increasing stimulus amplitude. "Sensory channel reweighting" could account for this nonlinear behavior with subjects showing increasing reliance on vestibular cues as stimulus amplitudes increased. VL subjects could not perform this reweighting, and their stimulus-response behavior remained quite linear. Transfer function curve fits based on a simple feedback control model provided estimates of postural stiffness, damping, and feedback time delay. There were only small changes in these parameters with increasing visual stimulus amplitude. However, stiffness increased as much as 60% with increasing support surface amplitude. To maintain postural stability and avoid resonant behavior, an increase in stiffness should be accompanied by a corresponding increase in damping. Increased damping was achieved primarily by decreasing the apparent time delay of feedback control rather than by changing the damping coefficient (i.e., corrective torque related to body-sway velocity). In normal subjects, stiffness and damping were highly correlated with body mass and moment of inertia, with stiffness always about 1/3 larger than necessary to resist the destabilizing torque due to gravity. The stiffness parameter in some VL subjects was larger compared with normal subjects, suggesting that they may use increased stiffness to help compensate for their loss. Overall results show that the simple act of standing quietly depends on a remarkably complex sensorimotor control system.

Familial orthostatic tachycardia due to norepinephrine transporter deficiency

NASA Technical Reports Server (NTRS)

Robertson, D.; Flattem, N.; Tellioglu, T.; Carson, R.; Garland, E.; Shannon, J. R.; Jordan, J.; Jacob, G.; Blakely, R. D.; Biaggioni, I.

2001-01-01

Orthostatic intolerance (OI) or postural tachycardia syndrome (POTS) is a syndrome primarily affecting young females, and is characterized by lightheadedness, palpitations, fatigue, altered mentation, and syncope primarily occurring with upright posture and being relieved by lying down. There is typically tachycardia and raised plasma norepinephrine levels on upright posture, but little or no orthostatic hypotension. The pathophysiology of OI is believed to be very heterogeneous. Most studies of the syndrome have focused on abnormalities in norepinephrine release. Here the hypothesis that abnormal norepinephrine transporter (NET) function might contribute to the pathophysiology in some patients with OI was tested. In a proband with significant orthostatic symptoms and tachycardia, disproportionately elevated plasma norepinephrine with standing, impaired systemic, and local clearance of infused tritiated norepinephrine, impaired tyramine responsiveness, and a dissociation between stimulated plasma norepinephrine and DHPG elevation were found. Studies of NET gene structure in the proband revealed a coding mutation that converts a highly conserved transmembrane domain Ala residue to Pro. Analysis of the protein produced by the mutant cDNA in transfected cells demonstrated greater than 98% reduction in activity relative to normal. NE, DHPG/NE, and heart rate correlated with the mutant allele in this family. CONCLUSION: These results represent the first identification of a specific genetic defect in OI and the first disease linked to a coding alteration in a Na+/Cl(-)-dependent neurotransmitter transporter. Identification of this mechanism may facilitate our understanding of genetic causes of OI and lead to the development of more effective therapeutic modalities.

[Effects of vibrotherapy on postural control, functionality and fatigue in multiple sclerosis patients. A randomised clinical trial].

PubMed

Alguacil Diego, I M; Pedrero Hernández, C; Molina Rueda, F; Cano de la Cuerda, R

2012-04-01

Postural and balance disorders, functionality impairment and fatigue, are the most incapacitating problems in multiple sclerosis (MS) patients. Whole Body Vibration (WBV), through the transmission of mechanical stimuli, appears to be a useful therapeutic tool in the treatment of neurological diseases. The objective of this study is to assess the effect of the WBV on postural control, balance, functionality and fatigue in patients with MS. A total of 34 patients with mild-moderate MS were randomised into a control group and an intervention group. For the intervention group, the protocol consisted of 5 consecutive days, daily series of 5 periods of 1 minute of duration of WBV at a frequency of 6 Hz. Posturographic assessment using the Sensory Organization Test (SOT) and Motor Control Test (MCT), the Timed Get Up and Go Test, 10 metres Test, the Berg Balance Scale and Krupp's Fatigue Severity Scale were used before and after intervention. The analysis showed improvements in the intervention group for conditions SOT 1, SOT 3 and latency in MCT. In the comparison between groups, only the latency or reaction time in MCT improved significantly in favour of the intervention group (from 173.78±12.46 to 161.25±13.64 ms; P=.04). No side-effects were found. The results of this pilot study show that WBV can improve, in the short-term, the time of response to recover the uprightness after sudden disturbances, appearing as a possible therapeutic tool maintaining balance and posture. Copyright © 2011 Sociedad Española de Neurología. Published by Elsevier Espana. All rights reserved.

Role of gravity-based information on the orientation and localization of the perceived body midline.

PubMed

Ceyte, Hadrien; Cian, Corinne; Nougier, Vincent; Olivier, Isabelle; Trousselard, Marion

2007-01-01

The present study focused on the influence of gravity-based information on the orientation and localization of the perceived body midline. The orientation was investigated by the rolling adjustment of a rod on the subjects' Z-axis and the localization by the horizontal adjustment of a visual dot as being straight ahead. Experiment 1 investigated the effect of the dissociation between the Z-axis and the direction of gravity by placing subjects in roll tilt and supine postures. In roll tilt, the perception of the body midline orientation was deviated in the direction of body tilt and the perception of its localization was deviated in the opposite direction. In the supine body orientation, estimates of the Z-axis and straight-ahead remained veridical as when the body was upright. Experiment 2 highlighted the relative importance of the otolithic and tactile information using diffuse pressure stimulation. The estimation of body midline orientation was modified contrarily to the estimation of its localization. Thus, subjects had no absolute representation of their egocentric space. The main hypothesis regarding the dissociation between the orientation and localization of the body midline may be related to a difference in the integration of sensory information. It can be suggested that the horizontal component of the vestibulo-ocular reflex (VOR) contributed to the perceived localization of the body midline, whereas its orientation was mainly influenced by tactile information.

Immediate Beneficial Effects of Mental Rotation Using Foot Stimuli on Upright Postural Stability in Healthy Participants

PubMed Central

Kawasaki, Tsubasa

2013-01-01

The present study was designed to investigate whether an intervention during which participants were involved in mental rotation (MR) of a foot stimulus would have immediate beneficial effects on postural stability (Experiment 1) and to confirm whether it was the involvement of MR of the foot, rather than simply viewing foot stimuli, that could improve postural stability (Experiment 2). Two different groups of participants (n = 16 in each group) performed MR intervention of foot stimuli in each of the two experiments. Pre- and postmeasurements of postural stability during unipedal and bipedal standing were made using a force plate for the intervention. Consistently, postural sway values for unipedal standing, but not for bipedal standing, were decreased immediately after the MR intervention using the foot stimuli. Such beneficial effects were not observed after the MR intervention using car stimuli (Experiment 1) or when participants observed the same foot stimuli during a simple reaction task (Experiment 2). These findings suggest that the MR intervention using the foot stimuli could contribute to improving postural stability, at least when it was measured immediately after the intervention, under a challenging standing condition (i.e., unipedal standing). PMID:24459588

Force direction patterns promote whole body stability even in hip-flexed walking, but not upper body stability in human upright walking

NASA Astrophysics Data System (ADS)

Müller, Roy; Rode, Christian; Aminiaghdam, Soran; Vielemeyer, Johanna; Blickhan, Reinhard

2017-11-01

Directing the ground reaction forces to a focal point above the centre of mass of the whole body promotes whole body stability in human and animal gaits similar to a physical pendulum. Here we show that this is the case in human hip-flexed walking as well. For all upper body orientations (upright, 25°, 50°, maximum), the focal point was well above the centre of mass of the whole body, suggesting its general relevance for walking. Deviations of the forces' lines of action from the focal point increased with upper body inclination from 25 to 43 mm root mean square deviation (RMSD). With respect to the upper body in upright gait, the resulting force also passed near a focal point (17 mm RMSD between the net forces' lines of action and focal point), but this point was 18 cm below its centre of mass. While this behaviour mimics an unstable inverted pendulum, it leads to resulting torques of alternating sign in accordance with periodic upper body motion and probably provides for low metabolic cost of upright gait by keeping hip torques small. Stabilization of the upper body is a consequence of other mechanisms, e.g. hip reflexes or muscle preflexes.

Intermittent Feedback-Control Strategy for Stabilizing Inverted Pendulum on Manually Controlled Cart as Analogy to Human Stick Balancing

PubMed Central

Yoshikawa, Naoya; Suzuki, Yasuyuki; Kiyono, Ken; Nomura, Taishin

2016-01-01

The stabilization of an inverted pendulum on a manually controlled cart (cart-inverted-pendulum; CIP) in an upright position, which is analogous to balancing a stick on a fingertip, is considered in order to investigate how the human central nervous system (CNS) stabilizes unstable dynamics due to mechanical instability and time delays in neural feedback control. We explore the possibility that a type of intermittent time-delayed feedback control, which has been proposed for human postural control during quiet standing, is also a promising strategy for the CIP task and stick balancing on a fingertip. Such a strategy hypothesizes that the CNS exploits transient contracting dynamics along a stable manifold of a saddle-type unstable upright equilibrium of the inverted pendulum in the absence of control by inactivating neural feedback control intermittently for compensating delay-induced instability. To this end, the motions of a CIP stabilized by human subjects were experimentally acquired, and computational models of the system were employed to characterize the experimental behaviors. We first confirmed fat-tailed non-Gaussian temporal fluctuation in the acceleration distribution of the pendulum, as well as the power-law distributions of corrective cart movements for skilled subjects, which was previously reported for stick balancing. We then showed that the experimental behaviors could be better described by the models with an intermittent delayed feedback controller than by those with the conventional continuous delayed feedback controller, suggesting that the human CNS stabilizes the upright posture of the pendulum by utilizing the intermittent delayed feedback-control strategy. PMID:27148031

Intermittent Feedback-Control Strategy for Stabilizing Inverted Pendulum on Manually Controlled Cart as Analogy to Human Stick Balancing.

PubMed

Yoshikawa, Naoya; Suzuki, Yasuyuki; Kiyono, Ken; Nomura, Taishin

2016-01-01

The stabilization of an inverted pendulum on a manually controlled cart (cart-inverted-pendulum; CIP) in an upright position, which is analogous to balancing a stick on a fingertip, is considered in order to investigate how the human central nervous system (CNS) stabilizes unstable dynamics due to mechanical instability and time delays in neural feedback control. We explore the possibility that a type of intermittent time-delayed feedback control, which has been proposed for human postural control during quiet standing, is also a promising strategy for the CIP task and stick balancing on a fingertip. Such a strategy hypothesizes that the CNS exploits transient contracting dynamics along a stable manifold of a saddle-type unstable upright equilibrium of the inverted pendulum in the absence of control by inactivating neural feedback control intermittently for compensating delay-induced instability. To this end, the motions of a CIP stabilized by human subjects were experimentally acquired, and computational models of the system were employed to characterize the experimental behaviors. We first confirmed fat-tailed non-Gaussian temporal fluctuation in the acceleration distribution of the pendulum, as well as the power-law distributions of corrective cart movements for skilled subjects, which was previously reported for stick balancing. We then showed that the experimental behaviors could be better described by the models with an intermittent delayed feedback controller than by those with the conventional continuous delayed feedback controller, suggesting that the human CNS stabilizes the upright posture of the pendulum by utilizing the intermittent delayed feedback-control strategy.

[A study on the relation between stomatognathic system and the systemic condition, concerning the influence of experimental occlusal interference on upright posture, particularly on gravity fluctuation and the antigravity muscles].

PubMed

Miyata, T

1990-06-01

The purpose of this study is to reveal the relation between stomatognathic system and the systemic condition. In the present study, experimental occlusal interference was given to the first molar on main mastication side of 6 healthy subjects and the influence on the upright posture was evaluated through simultaneous measurements of changes in activity of antigravity muscles via electromyography, other than the measurement of loci of the gravity fluctuation for stabilograph before and after the interference was provided. The following results were obtained, 1. Loci of gravity fluctuation 1) All parameters tended increase 24 hours after the interference was provided. 2) The decreasing trend was noted 24 hours after the interference was removed. 3) At one week after the interference was removed all analysis items tended to restore to the normal range. 2. Activity of antigravity muscles In some of the subjects, the muscular activity showed the same trend as the changes of analysis items of gravity fluctuation. 3. The above results suggest that the evaluation of the loci of the gravity fluctuation may be helpful to assess the therapeutic effect of malocclusion.

Incidence of vertical phoria on postural control during binocular vision: what perspective for prevention to nonspecific chronic pain management?

PubMed

Matheron, Eric; Kapoula, Zoï

2015-01-01

Vertical heterophoria (VH) is the latent vertical misalignment of the eyes when the retinal images are dissociated, vertical orthophoria (VO) when there is no misalignment. Studies on postural control, during binocular vision in upright stance, reported that healthy subjects with small VH vs. VO are less stable, but the experimental cancellation of VH with an appropriate prism improves postural stability. The same behavior was recorded in nonspecific chronic back pain subjects, all with VH. It was hypothesized that, without refraction problems, VH indicates a perturbation of the somaesthetic cues required in the sensorimotor loops involved in postural control and the capacity of the CNS to optimally integrate these cues, suggesting prevention possibilities. Sensorimotor conflict can induce pain and modify sensory perception in some healthy subjects; some nonspecific pain or chronic pain could result from such prolonged conflict in which VH could be a sign, with new theoretical and clinical implications.

A biomechanical and physiological study of office seat and tablet device interaction.

PubMed

Weston, Eric; Le, Peter; Marras, William S

2017-07-01

Twenty subjects performed typing tasks on a desktop computer and touch-screen tablet in two chairs for an hour each, and the effects of chair, device, and their interactions on each dependent measure were recorded. Biomechanical measures of muscle force, spinal load, and posture were examined, while discomfort was measured via heart rate variability (HRV) and subjective reports. HRV was sensitive enough to differentiate between chair and device interactions. Biomechanically, a lack of seat back mobility forced individuals to maintain an upright seating posture with increased extensor muscle forces and increased spinal compression. Effects were exacerbated by forward flexion upon interaction with a tablet device or by slouching. Office chairs should be designed with both the human and workplace task in mind and allow for reclined postures to off-load the spine. The degree of recline should be limited, however, to prevent decreased lumbar lordosis resulting from posterior hip rotation in highly reclined postures. Copyright © 2017 Elsevier Ltd. All rights reserved.

Proprioceptive impairments in high fall risk older adults: the effect of mechanical calf vibration on postural balance.

PubMed

Toosizadeh, Nima; Ehsani, Hossein; Miramonte, Marco; Mohler, Jane

2018-05-02

Impairments in proprioceptive mechanism with aging has been observed and associated with fall risk. The purpose of the current study was to assess proprioceptive deficits among high fall risk individuals in comparison with healthy participants, when postural performance was disturbed using low-frequency mechanical gastrocnemius vibratory stimulation. Three groups of participants were recruited: healthy young (n = 10; age = 23 ± 2 years), healthy elders (n = 10; age = 73 ± 3 years), and high fall risk elders (n = 10; age = 84 ± 9 years). Eyes-open and eyes-closed upright standing balance performance was measured with no vibration, and 30 and 40 Hz vibration of both calves. Vibration-induced changes in balance behaviors, compared to baseline (no vibratory stimulation) were compared between three groups using multivariable repeated measures analysis of variance models. Overall, similar results were observed for two vibration frequencies. However, changes in body sway due to vibration were more obvious within the eyes-closed condition, and in the medial-lateral direction. Within the eyes-closed condition high fall risk participants showed 83% less vibration-induced change in medial-lateral body sway, and 58% less sway velocity, when compared to healthy participants (p < 0.001; effect size = 0.45-0.64). The observed differences in vibration effects on balance performance may be explained by reduced sensitivity in peripheral nervous system among older adults with impaired balance.

Postural control system influences intrinsic alerting state.

PubMed

Barra, Julien; Auclair, Laurent; Charvillat, Agnès; Vidal, Manuel; Pérennou, Dominic

2015-03-01

Numerous studies using dual-task paradigms (postural and cognitive) have shown that postural control requires cognitive resources. However, the influence of postural control on attention components has never been directly addressed. Using the attention network test (ANT), which assesses specifically each of the 3 components of attention-alertness, orientation, and executive control-within a single paradigm, we investigated the effect of postural balance demand on these 3 components. Forty-two participants completed the ANT in 3 postural conditions: (a) supine, a very stable position; (b) sitting on a chair, an intermediate position; and (c) standing with feet lined up heel to toe, a very instable position known as the Romberg position. Our results revealed that the difficulty of postural control does modulate alerting in such a way that it improves with the level of instability of the position. Regarding the orienting and executive control components of attention, performance was not different when participants were standing upright or seated, whereas in the supine position, performance dropped. The strong and specific interaction between postural control and the alerting system suggests that these mechanisms may share parts of the underlying neural circuits. We discuss the possible implication of the locus coeruleus, known to be involved in both postural balance and alerting. Also, our findings concerning orienting and executive control systems suggest that supine posture could have a specific effect on cognitive activities. These effects are discussed in terms of particularities resulting from the supine position. PsycINFO Database Record (c) 2015 APA, all rights reserved.

Clinician-Focused Overview of Bionic Exoskeleton Use After Spinal Cord Injury.

PubMed

Palermo, Anne E; Maher, Jennifer L; Baunsgaard, Carsten Bach; Nash, Mark S

2017-01-01

Spinal cord injury (SCI) resulting in paralysis of lower limbs and trunk restricts daily upright activity, work capacity, and ambulation ability, putting persons with an injury at greater risk of developing a myriad of secondary medical issues. Time spent in the upright posture has been shown to decrease the risk of these complications in SCI. Unfortunately, the majority of ambulation assistive technologies are limited by inefficiencies such as high energy demand, lengthy donning and doffing time, and poor gait pattern precluding widespread use. These limitations spurred the development of bionic exoskeletons. These devices are currently being used in rehabilitation settings for gait retraining, and some have been approved for home use. This overview will address the current state of available devices and their utility.

Forelimb preferences in quadrupedal marsupials and their implications for laterality evolution in mammals

PubMed Central

2013-01-01

Background Acquisition of upright posture in evolution has been argued to facilitate manual laterality in primates. Owing to the high variety of postural habits marsupials can serve as a suitable model to test whether the species-typical body posture shapes forelimb preferences in non-primates or this phenomenon emerged only in the course of primate evolution. In the present study we aimed to explore manual laterality in marsupial quadrupeds and compare them with the results in the previously studied bipedal species. Forelimb preferences were assessed in captive grey short-tailed opossum (Monodelphis domestica) and sugar glider (Petaurus breviceps) in four different types of unimanual behaviour per species, which was not artificially evoked. We examined the possible effects of sex, age and task, because these factors have been reported to affect motor laterality in placental mammals. Results In both species the direction of forelimb preferences was strongly sex-related. Male grey short-tailed opossums showed right-forelimb preference in most of the observed unimanual behaviours, while male sugar gliders displayed only a slight, not significant rightward tendency. In contrast, females in both species exhibited consistent group-level preference of the left forelimb. We failed to reveal significant differences in manual preferences between tasks of potentially differing complexity: reaching a stable food item and catching live insects, as well as between the body support and food manipulation. No influence of subjects’ age on limb preferences was found. Conclusions The direction of sex-related differences in the manual preferences found in quadrupedal marsupials seems to be not typical for placental mammals. We suggest that the alternative way of interhemispheric connection in absence of corpus callosum may result in a fundamentally distinct mechanism of sex effect on limb preferences in marsupials compared to placentals. Our data confirm the idea that non-primate mammals differ from primates in sensitivity to task complexity. Comparison of marsupial species studied to date indicate that the vertical body orientation and the bipedalism favor the expression of individual– and population–level forelimb preferences in marsupials much like it does in primates. Our findings give the first evidence for the effect of species-typical posture on the manual laterality in non-primate mammals. PMID:23497116

Postural stability is altered by the stimulation of pain but not warm receptors in humans.

PubMed

Blouin, Jean-Sébastien; Corbeil, Philippe; Teasdale, Normand

2003-10-17

It is now recognized that large diameter myelinated afferents provide the primary source of lower limb proprioceptive information for maintaining an upright standing position. Small diameter afferents transmitting noxious stimuli, however, can also influence motor behaviors. Despite the possible influence of pain on motor behaviors, the effects of pain on the postural control system have not been well documented. Two cutaneous heat stimulations (experiment 1: non-noxious 40 degrees C; experiment 2: noxious 45 degrees C) were applied bilaterally on the calves of the subject with two thermal grills to stimulate A delta and C warm receptors and nociceptors in order to examine their effects on postural stability. The non-noxious stimulation induced a gentle sensation of warmth and the noxious stimulation induced a perception of heat pain (visual analogue scores of 0 and 46 mm, respectively). For both experiments, ten healthy young adults were tested with and without heat stimulations of the lower limbs while standing upright on a force platform with eyes open, eyes closed and eyes closed with tendon co-vibration of tibialis anterior and triceps surae muscles. The center of pressure displacements were analyzed to examine how both stimulations affected the regulation of quiet standing and if the effects were exacerbated when vision was removed or ankle proprioception perturbed. The stimulation of the warm receptors (40 degrees C) did not induce any postural deterioration. With pain (45 degrees C), subjects showed a significant increase in standard deviation, range and mean velocity of postural oscillations as well as standard deviation of the center of pressure velocity. The effects of heat pain were exacerbated when subjects had both their eyes closed and ankle tendons vibrated (increased standard deviation of the center of pressure velocity and mean velocity of the center of pressure). A non-noxious stimulation (40 degrees C) of the small diameter afferents is not a sufficiently intense sensory stimulation to alter the control of posture. A painful stimulation (45 degrees C) of the skin thermoreceptors, however, yielded a deterioration of the postural control system. The observed deteriorating effects of the combined stimulation of nociceptors and Ia afferents (when ankle tendons were vibrated) could result from the convergence of these afferents at the spinal level. This could certainly lead to the hypothesis that individuals suffering from lower limb pain present alterations of the postural control mechanisms; especially populations already at risk of falling (for example, frail elderly) or populations suffering from concomitant lower limb pain and sensory deficits (for example, diabetic polyneuropathy).

Perception of Upright: Multisensory Convergence and the Role of Temporo-Parietal Cortex

PubMed Central

Kheradmand, Amir; Winnick, Ariel

2017-01-01

We inherently maintain a stable perception of the world despite frequent changes in the head, eye, and body positions. Such “orientation constancy” is a prerequisite for coherent spatial perception and sensorimotor planning. As a multimodal sensory reference, perception of upright represents neural processes that subserve orientation constancy through integration of sensory information encoding the eye, head, and body positions. Although perception of upright is distinct from perception of body orientation, they share similar neural substrates within the cerebral cortical networks involved in perception of spatial orientation. These cortical networks, mainly within the temporo-parietal junction, are crucial for multisensory processing and integration that generate sensory reference frames for coherent perception of self-position and extrapersonal space transformations. In this review, we focus on these neural mechanisms and discuss (i) neurobehavioral aspects of orientation constancy, (ii) sensory models that address the neurophysiology underlying perception of upright, and (iii) the current evidence for the role of cerebral cortex in perception of upright and orientation constancy, including findings from the neurological disorders that affect cortical function. PMID:29118736

Influence of different body positions in vital capacity in patients on postoperative upper abdominal.

PubMed

Martinez, Bruno Prata; Silva, Joilma Ribeiro; Silva, Vanessa Salgado; Gomes Neto, Mansueto; Forgiarini Júnior, Luiz Alberto

2015-01-01

The changes in body position can cause changes in lung function, and it is necessary to understand them, especially in the postoperative upper abdominal surgery, since these patients are susceptible to postoperative pulmonary complications. To assess the vital capacity in the supine position (head at 0° and 45°), sitting and standing positions in patients in the postoperative upper abdominal surgery. A cross-sectional study conducted between August 2008 and January 2009 in a hospital in Salvador/BA. The instrument used to measure vital capacity was analogic spirometer, the choice of the sequence of positions followed a random order obtained from the draw of the four positions. Secondary data were collected from the medical records of each patient. The sample consisted of 30 subjects with a mean age of 45.2 ± 11.2 years, BMI 20.2 ± 1.0 kg/m(2). The position on orthostasis showed higher values of vital capacity regarding standing (mean change: 0.15 ± 0.03 L; p=0.001), the supine to 45 (average difference: 0.32 ± 0.04 L; p = 0.001) and 0° (0.50 ± 0.05 L; p = 0.001). There was a positive trend between the values of forced vital capacity supine to upright posture (1.68 ± 0.47; 1.86 ± 0.48; 2.02 ± 0.48 and 2.18 ± 0.52 L; respectively). Body position affects the values of vital capacity in patients in the postoperative upper abdominal surgery, increasing in postures where the chest is vertical. Copyright © 2014 Sociedade Brasileira de Anestesiologia. Published by Elsevier Editora Ltda. All rights reserved.

Postural orthostatic tachycardia syndrome: Dental treatment considerations.

PubMed

Brooks, John K; Francis, Laurie A P

2006-04-01

Postural orthostatic tachycardia syndrome (POTS) is a chronic, relatively common autonomic disorder typically affecting younger females. It is distinguished by a dramatic increase in heart rate on the assumption of an upright posture from the supine position. The authors provide an overview of the demographics, clinical assessment, diagnostic features, differential diagnoses, pathogeneses and medical treatment of patients with POTS, with an emphasis on the clinical treatment of the dental patient affected by the syndrome. Patients frequently exhibit symptoms of lightheadedness, fatigue, palpitations and syncope. Patients with POTS may have Ehlers-Danlos syndrome, mitral valve prolapse, chronic fatigue syndrome or, rarely, the Brugada syndrome. Despite widespread dissemination of information regarding POTS in the medical literature, scant information on it has appeared in dental publications. Dentists need to be familiar with the clinical features of POTS and be prepared to treat patients at risk of developing syncope.

Comparison of upright LBPP and supine LBNP in terms of cardiovascular and biomechanical parameters to simulate 1/6-G (lunar gravity) and 3/8-G (Martian gravity) activities

NASA Astrophysics Data System (ADS)

Schlabs, Thomas; Rosales-Velderrain, Armando; Ruckstuhl, Heidi; Richardson, Sara E.; Hargens, Alan

Background: Missions of astronauts to Moon and Mars may be planned in the future. From over 40 years of manned spaceflight it is known that the human body experiences cardiovascular and musculoskeletal losses and a decrease in aerobic fitness while exposed to reduced gravity. Because future missions will be much longer than before, further research is needed to improve Earth-based simulations of reduced gravity. Among others, two methods are capable of simu-lating fractional gravity on Earth: upright Lower Body Positive Pressure (LBPP) and supine Lower Body Negative Pressure (LBNP). No previous study has directly compared these two methods to determine which method is better suited to simulate both the biomechanical and cardiovascular responses of performing activity in lunar (1/6-G) and Martian (3/8-G) gravities. Taken previous studies into account and considering the fact that supine posture is closer to the established 10 head-up-tilt lunar simulation, we hypothesized that exercise performed in supine LBNP better simulates the cardiovascular conditions that occur in lunar and Martian gravities. Methods: 12 healthy normal subjects underwent a protocol consisting of resting and walking (0.25 Froude) with LBNP and LBPP. Each protocol was performed in simulated 1/6-G and 3/8-G. Heart-rate (HR), blood pressure, oxygen consumption (VO2), vertical component of the ground reaction force, comfort of the subject and perceived exertion of the subject (Borg Scale) were assessed. The obtained parameters were compared to predicted values for lunar and Martian gravity conditions in order to determine the method that shows the best level of agreement. Results: There was no difference in gait parameters between LBPP and LBNP simulation of lunar and Martian gravity (cadence: P=0.427, normalized stride length: P=0.373, duty fac-tor: P=0.302, and normalized vertical peak force (P=0.064). Mean blood pressure (P=0.398), comfort (P=0.832) and BORG rating (P=0.186) did not differ between the two methods. How-ever, we found that the heart rate (P=0.022) and VO2 (P=0.038) were significantly higher during LBPP (HRM oon =74±3 bpm, HRM ars =80±3 bpm, VO2M oon =4.6±0.22 l*kg-1 *min-1 , VO2M ars =6.17±0.38 l*kg-1 *min-1 ) than in LBNP (HRM oon =72±3 bpm, HRM ars =77±3 bpm, VO2M oon =4.66±0.43 l*kg-1 *min-1 , VO2M ars =5.66±0.42 l*kg-1 *min-1 ). A further analysis of deviation from the predicted parameters (HRM oon =77 bpm, HRM ars =84 bpm, VO2M oon =5.40 l*kg-1 *min-1 , VO2M ars =7.14 l*kg-1 *min-1 ) revealed a smaller deviation for LBPP (∆HR=4 bpm, ∆VO2=0.89 l*kg-1 *min-1 ) as compared to LBNP (∆HR=6 bpm, ∆VO2=1.11 l*kg-1 *min-1 ). Discussion: We conclude that biomechanical characteristics of gait are not different between supine LBNP and upright LBPP. In terms of cardiovascular parameters there are only differ-ences in heart rate and VO2. The higher heart rate during upright LBPP is probably due to a lower preload of the heart; as venous return is attenuated when the subject is positioned upright instead of supine. The higher VO2 during upright LBPP reflects the increased activity of anti-gravity muscles working to keep the upper body in balance without body suspension. Most skeletal muscles are not used when lying at rest in supine LBNP. Considering that values for heart rate and VO2 produced with the LBPP simulation had a smaller deviation from the predicted values than with the LBNP simulation, we conclude that upright LBPP is obviously better suited to simulate both lunar and Martian activities.

The influence of aging and attentional demands on recovery from postural instability.

PubMed

Stelmach, G E; Zelaznik, H N; Lowe, D

1990-06-01

It is well known that the risk of a debilitating injury from a fall is much higher for elderly than for young individuals. In addition, it is well documented that healthy elderly subjects exhibit increased postural sway during normal stance tasks. In the present experiment, we explored the notion that control of minor postural instability in elderly subjects is attention demanding. Postural sway of eight elderly (mean age = 70.0 years) and eight young (mean age = 20.0 years) subjects was measured under two different secondary demands during stable and mildly unstable upright stance. There were two types of work loads. Either a cognitive (math task) or motor (hand-squeeze) task was performed during the second segment of a 50-second standing trial. The effect of these work loads on mean velocity, range, and variability of range of center of foot pressure was measured during the destabilizing activity of arm swinging and subsequent recovery period. Following seven seconds of 1 Hz arm-swinging activity, elderly subjects showed a marked increase in recovery time to normal stance when concurrently performing an arithmetic task. This result suggests that recovery from a posturally destabilizing activity, involving proprioceptive and vestibular information, places increased attentional demands on the postural support system of the elderly.

MRI Evaluation of Spinal Length and Vertebral Body Angle During Loading with a Spinal Compression Harness

NASA Technical Reports Server (NTRS)

Campbell, James A.; Hargens, Alan R.; Murthy, G.; Ballard, R. E.; Watenpaugh, D. E.; Hargens, Alan, R.; Sanchez, E.; Yang, C.; Mitsui, I.; Schwandt, D.;

Relationship between Spectral Characteristics of Spontaneous Postural Sway and Motion Sickness Susceptibility.

PubMed

Laboissière, Rafael; Letievant, Jean-Charles; Ionescu, Eugen; Barraud, Pierre-Alain; Mazzuca, Michel; Cian, Corinne

2015-01-01

Motion sickness (MS) usually occurs for a narrow band of frequencies of the imposed oscillation. It happens that this frequency band is close to that which are spontaneously produced by postural sway during natural stance. This study examined the relationship between reported susceptibility to motion sickness and postural control. The hypothesis is that the level of MS can be inferred from the shape of the Power Spectral Density (PSD) profile of spontaneous sway, as measured by the displacement of the center of mass during stationary, upright stance. In Experiment 1, postural fluctuations while standing quietly were related to MS history for inertial motion. In Experiment 2, postural stability measures registered before the onset of a visual roll movement were related to MS symptoms following the visual stimulation. Study of spectral characteristics in postural control showed differences in the distribution of energy along the power spectrum of the antero-posterior sway signal. Participants with MS history provoked by exposure to inertial motion showed a stronger contribution of the high frequency components of the sway signal. When MS was visually triggered, sick participants showed more postural sway in the low frequency range. The results suggest that subject-specific PSD details may be a predictor of the MS level. Furthermore, the analysis of the sway frequency spectrum provided insight into the intersubject differences in the use of postural control subsystems. The relationship observed between MS susceptibility and spontaneous posture is discussed in terms of postural sensory weighting and in relation to the nature of the provocative stimulus.

Effects of m-xylene on human equilibrium measured with a quantitative method.

PubMed

Savolainen, K; Linnavuo, M

1979-04-01

Swaying during normal upright posture in 17 young males and the effects of m-xylene exposure on the body sway of six of the 17 has been studied by a quantitative Romberg test, conducted with an equipment consisting of a strain gauge transducer platform and of an electronic unit. The exposures were conducted in a dynamic exposure chamber. The sway of the 17 subjects was larger when their eyes were closed than when they were open (P less than 0.001) indicating the importance of vision in the control of body balance. Exposure to a time-weighted average (TWA) concentration of 100 p.p.m. (4.1 mumol/l) of xylene with 200 p.p.m. (8.2 mumol/l) peaks had no observable effect on the body balance of the six subjects. Exposure to a TWA concentration of 200 p.p.m. of xylene with 400 p.p.m. (16.4 mumol/l) peaks--the corresponding mean concentration of xylene in venous blood being 29.1 +/- 3.2 mumol/l--clearly impaired the body balance of the six subjects. The impairment was most pronounced with the eyes closed (P = 0.016). The results suggest that human equilibrium is rather sensitive to effects of exposure to xylene.

Effect of long-duration spaceflight on postural control during self-generated perturbations

NASA Technical Reports Server (NTRS)

Layne, C. S.; Mulavara, A. P.; McDonald, P. V.; Pruett, C. J.; Kozlovskaya, I. B.; Bloomberg, J. J.

2001-01-01

This report is the first systematic evaluation of the effects of prolonged weightlessness on the bipedal postural control processes during self-generated perturbations produced by voluntary upper limb movements. Spaceflight impacts humans in a variety of ways, one of which is compromised postflight postural control. We examined the neuromuscular activation characteristics and center of pressure (COP) motion associated with arm movement of eight subjects who experienced long-duration spaceflight (3--6 mo) aboard the Mir space station. Surface electromyography, arm acceleration, and COP motion were collected while astronauts performed rapid unilateral shoulder flexions before and after spaceflight. Subjects generally displayed compromised postural control after flight, as evidenced by modified COP peak-to-peak anterior-posterior and mediolateral excursion, and pathlength relative to preflight values. These changes were associated with disrupted neuromuscular activation characteristics, particularly after the completion of arm acceleration (i.e., when subjects were attempting to maintain upright posture in response to self-generated perturbations). These findings suggest that, although the subjects were able to assemble coordination modes that enabled them to generate rapid arm movements, the subtle control necessary to maintain bipedal equilibrium evident in their preflight performance is compromised after long-duration spaceflight.

The effect of Kinesio Taping on postural control in subjects with non-specific chronic low back pain.

PubMed

Abbasi, Soheila; Rojhani-Shirazi, Zahra; Shokri, Esmaeil; García-Muro San José, Francisco

2018-04-01

The aim of this study was to investigate the possible alterations in postural control during upright standing in subjects with non-specific chronic low back pain and the effect of Kinesio taping on the postural control. Twenty subjects with non-specific chronic low back pain and twenty healthy subjects participated in this study. The center of pressure excursion was evaluated before the intervention for both groups, and immediately after intervention for the low back pain group. Independent sample t-test, Mann-Whitney test and repeated measure ANOVA were used for the statistical analysis of the data. There were significant differences in the center of pressure excursion between the low back pain group versus the healthy group. The results of the ANOVA demonstrated a statistically significant difference in the mean COP displacement and velocity before Kinesio Taping, immediately after, and 24 h after in the low back pain group. There are poor postural control mechanisms in subjects with non-specific chronic low back pain. Kinesio taping seems to change postural control immediately and have lasting effects until the day after. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of Long-Duration Spaceflight on Postural Control During Self-Generated Perturbations

NASA Technical Reports Server (NTRS)

Layne, Charles S.; Mulavera, Ajitkumar P.; McDonald, P. Vernon; Pruett, Casey J.; Kozlovskaya, Innessa B.; Bloomberg, Jacob J.

2001-01-01

This report is the first systematic evaluation of the effects of prolonged weightlessness on the bipedal postural control processes during self-generated perturbations produced by voluntary upper limb movements. Spaceflight impacts humans in a variety of ways, one of which is compromised postflight postural control. We examined the neuromuscular activation characteristics and center of pressure motion (COP) associated with arm movement of eight subjects who experienced long duration spaceflight (3-6 months) aboard the Mir space station. Surface electromyography (EMG), arm acceleration, and COP motion were collected while astronauts performed rapid unilateral shoulder flexions prior to and after spaceflight. Subjects displayed compromised postural control after flight as evidenced by modified peak-to-peak COP anterior-posterior and medio-lateral motion and COP pathlength relative to preflight values. These changes were associated with disrupted neuromuscular activation characteristics, particularly after the completion of arm acceleration (i.e. when subjects were attempting to maintain their upright posture). These findings suggest that although the subjects were able to assemble coordination modes that enabled them to generate rapid arm movements, the subtle control necessary to maintain bipedal equilibrium evident in their preflight performance is compromised after long duration spaceflight.

The influence of peripheral neuropathy, gender, and obesity on the postural stability of patients with type 2 diabetes mellitus.

PubMed

Herrera-Rangel, Aline; Aranda-Moreno, Catalina; Mantilla-Ochoa, Teresa; Zainos-Saucedo, Lylia; Jáuregui-Renaud, Kathrine

2014-01-01

To assess the influence of peripheral neuropathy, gender, and obesity on the postural stability of patients with type 2 diabetes mellitus. 151 patients with no history of otology, neurology, or orthopaedic or balance disorders accepted to participate in the study. After a clinical interview and neuropathy assessment, postural stability was evaluated by static posturography (eyes open/closed on hard/soft surface) and the "Up & Go" test. During static posturography, on hard surface, the length of sway was related to peripheral neuropathy, gender, age, and obesity; on soft surface, the length of sway was related to peripheral neuropathy, gender, and age, the influence of neuropathy was larger in males than in females, and closing the eyes increased further the difference between genders. The mean time to perform the "Up & Go" test was 11.6 ± 2.2 sec, with influence of peripheral neuropathy, gender, and age. In order to preserve the control of static upright posture during conditions with deficient sensory input, male patients with type 2 diabetes mellitus with no history of balance disorders may be more vulnerable than females, and obesity may decrease the static postural control in both males and females.

Design and Validation of a Low-Cost Portable Device to Quantify Postural Stability.

PubMed

Zhu, Yong

2017-03-18

Measurement of the displacement of the center-of-pressure (COP) is an important tool used in biomechanics to assess postural stability and human balance. The goal of this research was to design and validate a low-cost portable device that can offer a quick indication of the state of postural stability and human balance related conditions. Approximate entropy (ApEn) values reflecting the amount of irregularity hiding in COP oscillations were used to calculate the index. The prototype adopted a portable design using the measurements of the load cells located at the four corners of a low-cost force platform. The test subject was asked to stand on the device in a quiet, normal, upright stance for 30 s with eyes open and subsequently for 30 s with eyes closed. Based on the COP displacement signals, the ApEn values were calculated. The results indicated that the prototype device was capable of capturing the increase in regularity of postural control in the visual-deprivation conditions. It was also able to decipher the subtle postural control differences along anterior-posterior and medial-lateral directions. The data analysis demonstrated that the prototype would enable the quantification of postural stability and thus provide a low-cost portable device to assess many conditions related to postural stability and human balance such as aging and pathologies.

Cardiovascular and Postural Control Interactions during Hypergravity: Effects on Cerebral Autoregulation in Males and Females

NASA Astrophysics Data System (ADS)

Goswami, Nandu; Blaber, Andrew; Bareille, Marie-Pierre; Beck, Arnaud; Avan, Paul; Bruner, Michelle; Hinghofer-Szalkay, Helmut

2012-07-01

Orthostatic intolerance remains a problem upon return to Earth from the microgravity environment of spaceflight. A variety of conditions including hypovolemia, cerebral vasoconstriction, cerebral or peripheral vascular disease, or cardiac arrhythmias may result in syncope if the person remains upright. Current research indicates that there is a greater dependence on visual and somatosensory information at the beginning of space flight with a decreased otolith gain during prolonged space flight (Herault et al., 2002). The goal of the research is to further our understanding of the fundamental adaptive homeostatic mechanisms involved in gravity related changes in cardiovascular and postural function. Cardiovascular, cerebrovascular, and postural sensory motor control systems in male and female participants before, during, and after exposure to graded levels of hyper-G were investigated. Hypotheses: 1) Activation of skeletal muscle pump will be directly related to the degree of orthostatic stress. 2) Simultaneous measurement of heart rate, blood pressure and postural sway will predict cardio-postural stability. Blood pressure and heart rate (means and variability), postural sway, center of pressure (COP), baroreflex function, calf blood flow, middle cerebral artery blood flow, non-invasive intracranial pressure measurements, and two-breath CO2 were measured. Results from the study will be used to provide an integrated insight into mechanisms of cardio-postural control and cerebral autoregulation, which are important aspects of human health in flights to Moon, Mars and distant planets.

Compliant Walker

NASA Technical Reports Server (NTRS)

Kerley, James J.; Eklund, Wayne; Crane, Alan

1992-01-01

Walker supports person with limited use of legs and back. Enables person to stand upright, move with minimum load, and rest at will taking weight off legs. Consists of wheeled frame with body harness connected compliantly to side structures. Harness supports wearer upright when wearer relaxes and takes weight off lower extremities. Assumes partial to full body weight at user's discretion.

Effects of immersion water temperature on whole-body fluid distribution in humans.

PubMed

Stocks, J M; Patterson, M J; Hyde, D E; Jenkins, A B; Mittleman, K D; Taylor, N A S

2004-09-01

In this study, we quantified acute changes in the intracellular and extracellular fluid compartments during upright neutral- and cold-water immersion. We hypothesized that, during short-term cold immersion, fluid shifts would be wholly restricted to the extracellular space. Seven males were immersed 30 days apart: control (33.3 degrees SD 0.6 degrees C); and cold (18.1 degrees SD 0.3 degrees C). Posture was controlled for 4 h prior to a 60-min seated immersion. Significant reductions in terminal oesophageal (36.9 degrees +/- 0.1 degrees -36.3 degrees +/- 0.1 degrees C) and mean skin temperatures (30.3 degrees +/- 0.3 degrees -23.0 degrees +/- 0.3 degrees C) were observed during the cold, but not the control immersion. Both immersions elicited a reduction in intracellular fluid [20.17 +/- 6.02 mL kg(-1) (control) vs. 22.72 +/- 9.90 mL kg(-1)], while total body water (TBW) remained stable. However, significant plasma volume (PV) divergence was apparent between the trials at 60 min [12.5 +/- 1.0% (control) vs. 6.1 +/- 3.1%; P < 0.05], along with a significant haemodilution in the control state (P < 0.05). Plasma atrial natriuretic peptide concentration increased from 18.0 +/- 1.6 to 58.7 +/- 15.1 ng L(-1) (P < 0.05) during cold immersion, consistent with its role in PV regulation. We observed that, regardless of the direction of the PV change, both upright immersions elicited reductions in intracellular fluid. These observations have two implications. First, one cannot assume that PV changes reflect those of the entire extracellular compartment. Second, since immersion also increases interstitial fluid pressure, fluid leaving the interstitium must have been rapidly replaced by intracellular water.

Noninvasive Intracranial Pressure and Tissue Oxygen Measurements for Space and Earth

NASA Technical Reports Server (NTRS)

Hargens, A. R.; Ballard, R. E.; Murthy, G.; Watenpaugh, D. E.

1994-01-01

The paper discusses the following: Increasing intracranial pressure in humans during simulated microgravity. and near-infrared monitoring of model chronic compartment syndrome in exercising skeletal muscle. Compared to upright-seated posture, 0 deg. supine, 6 deg. HDT, and 15 deg. HDT produced TMD changes of 317 +/- 112, 403 +/- 114, and 474 +/- 112 n1 (means +/- S.E.), respectively. Furthermore, postural transitions from 0 deg. supine to 6 deg. HDT and from 6 deg. to 15 deg. HDT generated significant TMD changes (p less than 0.05). There was no hysteresis when postural transitions to HDT were compared to reciprocal transitions toward upright seated posture. Currently, diagnosis of chronic compartment syndrome (CCS) depends on measurement of intramuscular pressure by invasive catheterization. We hypothesized that this syndrome can be detected noninvasively by near-infrared (NIR) spectroscopy, which tracks variations in muscle hemoglobin/myoglobin oxygen saturation. CCS was simulated in the tibialis anterior muscle of 7 male and 3 female subjects by gradual inflation of a cuff placed around the leg to 40 mmHg during 14 minutes of cyclic isokinetic dorsiflexion exercise. On a separate day, subjects underwent the identical exercise protocol with no external compression. In both cases, tissue oxygenation (T(sub O2) was measured in the tibialis anterior by NIR spectroscopy and normalized to a percentage scale between baseline and a T(sub O2) nadir reached during exercise to ischemic exhaustion. Over the course of exercise, T(sub O2) declined at a rate of 1.4 +/- 0.3% per minute with model CCS, yet did not decrease during control exercise. Post-exercise recovery of T(sub O2) was slower with model CCS (2.5 +/- 0.6 min) than in control (1.3 +/- 0.2 min). These results demonstrate that NIR spectroscopy can detect muscle deoxygenation caused by pathologically elevated intramuscular pressure in exercising skeletal muscle. Consequently, this technique shows promise as a noninvasive diagnostic tool for CCS.

[The changes in renin-angiotensin-aldosterone-system in different subtypes of Cushing's syndrome].

PubMed

Cui, Jia; Dou, Jingtao; Yang, Guoqing; Zang, Li; Jin, Nan; Chen, Kang; Du, Jin; Gu, Weijun; Wang, Xianling; Yang, Lijuan; Lyu, Zhaohui; Ba, Jianming; Mu, Yiming; Lu, Juming; Li, Jiangyuan; Pan, Changyu

2015-07-01

Cushing's syndrome is a clinical condition resulting from chronic exposure to excess glucocorticoid. As a consequence, long-term hypercortisolism contributes significantly to the development of systemic disorders by direct and/or indirect effects. The present study was to analyze the changes of renin-angiotensin-aldosterone-system in different subtypes of Cushing's syndrome on the standard posture test. We retrospectively reviewed 150 patients with histologically confirmed Cushing's syndrome treated at the PLA General Hospital between 2002 and 2014. Among them, 128 patients were diagnosed as adreno-cortico-tropic-hormone (ACTH)-independent Cushing's syndrome, and 22 were ACTH-dependent Cushing's syndrome. All patients were undertaken the posture test. Plasma renin activity (PRA), angiotensin II, plasma aldosterone concertration (PAC) levels were measured before and after the test. Basal plasma PRA [0.5 (0.2,1.3)µg·L(-1)·h(-1), angiotensin II [(48.9±20.1) ng/L] and PAC [(285.0±128.1) pmol/L] levels were within the normal range in supine position. Compared with the subjects with ACTH-independent Cushing's syndrome, the basal PAC levels were higher in subjects with ACTH-dependent Cushing's syndrome [(348.0±130.4) pmol/L vs (274.2±125.0) pmol/L, P<0.05]. However, the PAC response in subjects with ACTH-dependent Cushing's syndrome [(49.7±26.4)%] was significantly lower than that in those with ACTH-independent Cushing's syndrome [(81.2±69.3)%] upon upright posture stimulation (P<0.05). There were no statistical significances in PRA and angiotensin II levels between the two groups. The basal PAC and PRA levels were positively correlated with ACTH, whereas PAC response was negatively correlated with ACTH. The renin-angiotensin-aldosterone-system activity in subjects with Cushing's syndrome was similar to that in normal control. The basal PAC level and its response to upright posture are differently associated with ACTH level in Cushing's syndrome.

Performance Based Design of a New Virtual Locomotion Control

DTIC Science & Technology

2000-11-01

constraints on movements, caloric energy expenditure , etc.). (2) The control action should interact with other actions (looking, manipulation, posturing...velocity, natural cadence, caloric expenditure , etc.) but it is unlikely that one set of tuning parameters will satisfy all criteria. Experimental...tethered for safety. OSIRIS, developed by the US Army’s Night Vision Laboratory, is a stair -stepper device that can only be used upright [Lorenzo et al

Spaceflight Did Not Impair Cardiovascular Responses to Upright Posture in an Elderly Astronaut

NASA Technical Reports Server (NTRS)

Rossum, Alfred C.; Ziegler, Michael G.; Meck, Janice V.

2001-01-01

Some of the cardiovascular changes associated with spaceflight have similarities to those associated with aging. We studied the neuroendocrine and hemodynamic responses to upright posture in a 77 year old astronaut before and after spaceflight and compared them to those of a group of 20 younger (41 plus or minus 1 years) astronauts. While arterial pressure responses to standing were similar between the young and old astronauts, hemodynamic profiles were quite different. The elderly astronaut achieved adequate standing arterial pressure primarily by maintaining stroke volume and thus cardiac output. In spite of very high norepinephrine release, he had very little increase in heart rate or total peripheral resistance. This pattern persisted on all test occasions. These responses suggest high sympathetic responses, down-regulated adrenergic receptors and decreased venous compliance typical of aging. In contrast, younger astronauts did not maintain stroke volume or cardiac output with standing, but had significant increases in heart rate and resistance. These results suggest that this elderly subject had cardiovascular responses to standing that are expected in an aged person. These responses were not deleteriously affected by spaceflight. We suggest that healthy, fit elderly individuals are able to withstand the stresses of extreme environments and are not necessarily limited in their activities simply due to their chronological age.

Lean production design using value stream mapping and ergonomics approach for waste elimination on buffing panel upright process

NASA Astrophysics Data System (ADS)

Suryoputro, M. R.; Sari, A. D.; Burhanudin, R.; Sugarindra, M.

2017-12-01

This study discussed the implementation of ergonomics and value stream mapping issues to reduce the existing waste in the process of buffing upright panel in the XYZ music manufacturing company. Aimed to identify the 9 waste based on the identification in terms of production processes and ergonomic factors, namely environmental health and safety, defects, overproduction, waiting, not utilizing employee knowledge skill and ability, transportation, inventory, motion, and excess process. In addition, ergonomics factors were identified, for example posture using REBA, job safety analysis, and physical workload. This study results indicated that the process is having 21.4% of the potential dangers that could not be accepted and thus potentially lead to lost time. Continued with the physical workload, the score of % cardiovascular load value is still below 30%, which means that the physical workload is normal and allows the addition of work. Meanwhile, in the calculation of posture investigation, the REBA resulted that there was a motion waste identified on the edge buff machine and ryoto with the score of 10 and 8. In conclusion, the results shown that there were 20 overall waste produced, then thus waste were reduced based on the identification and discussion of proposed improvements.

Metabolic rate measurements comparing supine with upright upper-body exercises

NASA Technical Reports Server (NTRS)

Fortney, Suzanne M.; Greenisen, Michael C.; Loftin, Karin C.; Beene, Donya; Freeman-Perez, Sondra; Hnatt, Linda

1993-01-01

The ground-based study that tested the hypothesis that metabolic rates during supine and upright upper-body exercises are similar (mean value of 200 kcal/h) is presented. Six subjects each performed supine or upright exercise at three exercise stations, a hand-cycle ergometer, a rope-pull device, and a torque wrench. After a baseline measurement of the metabolic rate at rest, the metabolic rate was measured twice at each exercise station. The mean metabolic rates (kcal/h) during supine (n = 6) and upright control (n = 4) exercise stations were not significantly different except for the rope-pull station, 153.5 +/- 16.6 (supine) as compared to 247.0 +/- 21.7 (upright), p is less than 0.05. This difference may be due in part to an increased mechanical efficiency of supine exercises (15.0 +/- 0.7 percent) as compared to that of upright exercises (11.0 +/- 1.08 percent), p is less than 0.05. The net energy input was significantly smaller for the supine rope-pull exercise (64 +/- 18) as compared to upright (176 +/- 20). The relationship between best-rest exercises, metabolic rates, and the incidence of decompression sickness (DCS) should be examined to determine the true risk of DCS in spaceflight extravehicular activities.

Assessment of body posture in 12- and 13-year-olds attending primary schools in Pabianice.

PubMed

Motylewski, Sławomir; Zientala, Aleksandra; Pawlicka-Lisowska, Agnieszka; Poziomska-Piątkowska, Elżbieta

2015-12-01

of study was to estimate the body posture in children finishing primary schools. This is the last moment to make any improvement in body posture needed, because after the end of the child's growth the correction of postural defects is practically impossible. The study was conducted on 236 pupils aged 12-13 years attending primary schools number 3, 5 and 17 in Pabianice. To evaluate body posture Kasperczyk's points method was used. It is a commonly applied method for screening purposes. Over 50% of studied children had poor body posture and just under 6% of pupils' posture was assessed as very good. In the study population of children finishing primary schools the occurrence of faulty posture was shown to be very high. The most common defect in body posture among pupils was an uneven alignment of shoulders and shoulder blades. The results obtained in this study indicate the need to undertake action reducing the occurrence of faulty posture among children in Pabianice. © 2015 MEDPRESS.

Correlation between lumbar dysfunction and fat infiltration in lumbar multifidus muscles in patients with low back pain.

PubMed

Hildebrandt, Markus; Fankhauser, Gabriela; Meichtry, André; Luomajoki, Hannu

2017-01-10

Lumbar multifidus muscles (LMM) are important for spinal motion and stability. Low back pain (LBP) is often associated with fat infiltration in LMM. An increasing fat infiltration of LMM may lead to lumbar dysfunction. The purpose of this study was to investigate whether there is a correlation between the severity of lumbar dysfunction and the severity of fat infiltration of LMM. In a cross-sectional study, 42 patients with acute or chronic LBP were recruited. Their MRI findings were visually rated and graded using three criteria for fat accumulation in LMM: Grade 0 (0-10%), Grade 1 (10-50%) and Grade 2 (>50%). Lumbar sagittal range of motion, dynamic upright and seated posture control, sagittal movement control, body awareness and self-assessed functional disability were measured to determine the patients' low back dysfunction. The main result of this study was that increased severity of fat infiltration in the lumbar multifidus muscles correlated significantly with decreased range of motion of lumbar flexion (p = 0.032). No significant correlation was found between the severity of fat infiltration in LMM and impaired movement control, posture control, body awareness or self-assessed functional disability. This is the first study investigating the relationship between the severity of fat infiltration in LMM and the severity of lumbar dysfunction. The results of this study will contribute to the understanding of the mechanisms leading to fat infiltration of LMM and its relation to spinal function. Further studies should investigate whether specific treatment strategies are effective in reducing or preventing fat infiltration of LMM.

Sex differences in gait utilization and energy metabolism during terrestrial locomotion in two varieties of chicken (Gallus gallus domesticus) selected for different body size

PubMed Central

Rose, Kayleigh A.; Nudds, Robert L.; Butler, Patrick J.; Codd, Jonathan R.

2015-01-01

ABSTRACT In leghorn chickens (Gallus gallus domesticus) of standard breed (large) and bantam (small) varieties, artificial selection has led to females being permanently gravid and sexual selection has led to male-biased size dimorphism. Using respirometry, videography and morphological measurements, sex and variety differences in metabolic cost of locomotion, gait utilisation and maximum sustainable speed (Umax) were investigated during treadmill locomotion. Males were capable of greater Umax than females and used a grounded running gait at high speeds, which was only observed in a few bantam females and no standard breed females. Body mass accounted for variation in the incremental increase in metabolic power with speed between the varieties, but not the sexes. For the first time in an avian species, a greater mass-specific incremental cost of locomotion, and minimum measured cost of transport (CoTmin) were found in males than in females. Furthermore, in both varieties, the female CoTmin was lower than predicted from interspecific allometry. Even when compared at equivalent speeds (using Froude number), CoT decreased more rapidly in females than in males. These trends were common to both varieties despite a more upright limb in females than in males in the standard breed, and a lack of dimorphism in posture in the bantam variety. Females may possess compensatory adaptations for metabolic efficiency during gravidity (e.g. in muscle specialization/posture/kinematics). Furthermore, the elevated power at faster speeds in males may be linked to their muscle properties being suited to inter-male aggressive combat. PMID:26405047

Chronic renin inhibition lowers blood pressure and reduces upright muscle sympathetic nerve activity in hypertensive seniors

PubMed Central

Okada, Yoshiyuki; Jarvis, Sara S; Best, Stuart A; Bivens, Tiffany B; Adams-Huet, Beverley; Levine, Benjamin D; Fu, Qi

2013-01-01

Cardiovascular risk remains high in patients with hypertension even with adequate blood pressure (BP) control. One possible mechanism may be sympathetic activation via the baroreflex. We tested the hypothesis that chronic inhibition of renin reduces BP without sympathetic activation, but diuresis augments sympathetic activity in elderly hypertensives. Fourteen patients with stage-I hypertension (66 ± 5 (SD) years) were treated with a direct renin inhibitor, aliskiren (n= 7), or a diuretic, hydrochlorothiazide (n= 7), for 6 months. Muscle sympathetic nerve activity (MSNA), BP, direct renin and aldosterone were measured during supine and a graded head-up tilt (HUT; 5 min 30° and 20 min 60°), before and after treatment. Sympathetic baroreflex sensitivity (BRS) was assessed. Both groups had similar BP reductions after treatment (all P < 0.01), while MSNA responses were different between hydrochlorothiazide and aliskiren (P= 0.006 pre/post × drug). Both supine and upright MSNA became greater after hydrochlorothiazide treatment (supine, 72 ± 18 post vs. 64 ± 15 bursts (100 beats)−1 pre; 60° HUT, 83 ± 10 vs. 78 ± 13 bursts (100 beats)−1; P= 0.002). After aliskiren treatment, supine MSNA remained unchanged (69 ± 13 vs. 64 ± 8 bursts (100 beats)−1), but upright MSNA was lower (74 ± 15 vs. 85 ± 10 bursts (100 beats)−1; P= 0.012 for pre/post × posture). Direct renin was greater after both treatments (both P < 0.05), while upright aldosterone was greater after hydrochlorothiazide only (P= 0.002). The change in upright MSNA by the treatment was correlated with the change of aldosterone (r= 0.74, P= 0.002). Upright sympathetic BRS remained unchanged after either treatment. Thus, chronic renin inhibition may reduce upright MSNA through suppressed renin activity, while diuresis may evoke sympathetic activation via the upregulated renin–angiotensin–aldosterone system, without changing intrinsic sympathetic baroreflex function in elderly hypertensive patients. PMID:24060993

Impact of body position on central and peripheral hemodynamic contributions to movement-induced hyperemia: implications for rehabilitative medicine

PubMed Central

McDaniel, John; Venturelli, Massimo; Fjeldstad, Anette S.; Ives, Stephen J.; Witman, Melissa A. H.; Barrett-O'Keefe, Zachary; Amann, Markus; Wray, D. Walter; Richardson, Russell S.

2011-01-01

This study used alterations in body position to identify differences in hemodynamic responses to passive exercise. Central and peripheral hemodynamics were noninvasively measured during 2 min of passive knee extension in 14 subjects, whereas perfusion pressure (PP) was directly measured in a subset of 6 subjects. Movement-induced increases in leg blood flow (LBF) and leg vascular conductance (LVC) were more than twofold greater in the upright compared with supine positions (LBF, supine: 462 ± 6, and upright: 1,084 ± 159 ml/min, P < 0.001; and LVC, supine: 5.3 ± 1.2, and upright: 11.8 ± 2.8 ml·min−1·mmHg−1, P < 0.002). The change in heart rate (HR) from baseline to peak was not different between positions (supine: 8 ± 1, and upright: 10 ± 1 beats/min, P = 0.22); however, the elevated HR was maintained for a longer duration when upright. Stroke volume contributed to the increase in cardiac output (CO) during the upright movement only. CO increased in both positions; however, the magnitude and duration of the CO response were greater in the upright position. Mean arterial pressure and PP were higher at baseline and throughout passive movement when upright. Thus exaggerated central hemodynamic responses characterized by an increase in stroke volume and a sustained HR response combined to yield a greater increase in CO during upright movement. This greater central response coupled with the increased PP and LVC explains the twofold greater and more sustained increase in movement-induced hyperemia in the upright compared with supine position and has clinical implications for rehabilitative medicine. PMID:21357514

Impact of body position on central and peripheral hemodynamic contributions to movement-induced hyperemia: implications for rehabilitative medicine.

PubMed

Trinity, Joel D; McDaniel, John; Venturelli, Massimo; Fjeldstad, Anette S; Ives, Stephen J; Witman, Melissa A H; Barrett-O'Keefe, Zachary; Amann, Markus; Wray, D Walter; Richardson, Russell S

2011-05-01

This study used alterations in body position to identify differences in hemodynamic responses to passive exercise. Central and peripheral hemodynamics were noninvasively measured during 2 min of passive knee extension in 14 subjects, whereas perfusion pressure (PP) was directly measured in a subset of 6 subjects. Movement-induced increases in leg blood flow (LBF) and leg vascular conductance (LVC) were more than twofold greater in the upright compared with supine positions (LBF, supine: 462 ± 6, and upright: 1,084 ± 159 ml/min, P < 0.001; and LVC, supine: 5.3 ± 1.2, and upright: 11.8 ± 2.8 ml·min⁻¹ ·mmHg⁻¹, P < 0.002). The change in heart rate (HR) from baseline to peak was not different between positions (supine: 8 ± 1, and upright: 10 ± 1 beats/min, P = 0.22); however, the elevated HR was maintained for a longer duration when upright. Stroke volume contributed to the increase in cardiac output (CO) during the upright movement only. CO increased in both positions; however, the magnitude and duration of the CO response were greater in the upright position. Mean arterial pressure and PP were higher at baseline and throughout passive movement when upright. Thus exaggerated central hemodynamic responses characterized by an increase in stroke volume and a sustained HR response combined to yield a greater increase in CO during upright movement. This greater central response coupled with the increased PP and LVC explains the twofold greater and more sustained increase in movement-induced hyperemia in the upright compared with supine position and has clinical implications for rehabilitative medicine.

Compliant walker

NASA Technical Reports Server (NTRS)

Kerley, James J. (Inventor); Eklund, Wayne D. (Inventor); Crane, J. Allen (Inventor)

1992-01-01

A compliant walker is provided for humans having limited use of their legs and lower back. It includes an upright wheel frame which at least partially surrounds an upright user wearing a partial body harness. It is attached to the frame by means of cable compliant apparatus consisting of sets of cable segments and angle bracket members connected between opposite side members of the frame and adjacent side portions of the harness. Novelty is believed to exist in the combination of a wheeled frame including a side support structure, a body harness, and compliance means connecting the body harness to the side support structure for flexibility holding and supporting a person in a substantially upright position when the user sags in the frame when taking weight off the lower extremities.

Vertical Heterophoria and Postural Control in Nonspecific Chronic Low Back Pain

PubMed Central

Matheron, Eric; Kapoula, Zoï

2011-01-01

The purpose of this study was to test postural control during quiet standing in nonspecific chronic low back pain (LBP) subjects with vertical heterophoria (VH) before and after cancellation of VH; also to compare with healthy subjects with, and without VH. Fourteen subjects with LBP took part in this study. The postural performance was measured through the center of pressure displacements with a force platform while the subjects fixated on a target placed at either 40 or 200 cm, before and after VH cancellation with an appropriate prism. Their postural performance was compared to that of 14 healthy subjects with VH and 12 without VH (i.e. vertical orthophoria) studied previously in similar conditions. For LBP subjects, cancellation of VH with a prism improved postural performance. With respect to control subjects (with or without VH), the variance of speed of the center of pressure was higher, suggesting more energy was needed to stabilize their posture in quiet upright stance. Similarly to controls, LBP subjects showed higher postural sway when they were looking at a target at a far distance than at a close distance. The most important finding is that LBP subjects with VH can improve their performance after prism-cancellation of their VH. We suggest that VH reflects mild conflict between sensory and motor inputs involved in postural control i.e. a non optimal integration of the various signals. This could affect the performance of postural control and perhaps lead to pain. Nonspecific chronic back pain may results from such prolonged conflict. PMID:21479210

Abdominal Organ Location, Morphology, and Rib Coverage for the 5(th), 50(th), and 95(th) Percentile Males and Females in the Supine and Seated Posture using Multi-Modality Imaging.

PubMed

Hayes, Ashley R; Gayzik, F Scott; Moreno, Daniel P; Martin, R Shayn; Stitzel, Joel D

The purpose of this study was to use data from a multi-modality image set of males and females representing the 5(th), 50(th), and 95(th) percentile (n=6) to examine abdominal organ location, morphology, and rib coverage variations between supine and seated postures. Medical images were acquired from volunteers in three image modalities including Computed Tomography (CT), Magnetic Resonance Imaging (MRI), and upright MRI (uMRI). A manual and semi-automated segmentation method was used to acquire data and a registration technique was employed to conduct a comparative analysis between abdominal organs (liver, spleen, and kidneys) in both postures. Location of abdominal organs, defined by center of gravity movement, varied between postures and was found to be significant (p=0.002 to p=0.04) in multiple directions for each organ. In addition, morphology changes, including compression and expansion, were seen in each organ as a result of postural changes. Rib coverage, defined as the projected area of the ribs onto the abdominal organs, was measured in frontal, lateral, and posterior projections, and also varied between postures. A significant change in rib coverage between postures was measured for the spleen and right kidney (p=0.03 and p=0.02). The results indicate that posture affects the location, morphology and rib coverage area of abdominal organs and these implications should be noted in computational modeling efforts focused on a seated posture.

Body posture modulates action perception.

PubMed

Zimmermann, Marius; Toni, Ivan; de Lange, Floris P

2013-04-03

Recent studies have highlighted cognitive and neural similarities between planning and perceiving actions. Given that action planning involves a simulation of potential action plans that depends on the actor's body posture, we reasoned that perceiving actions may also be influenced by one's body posture. Here, we test whether and how this influence occurs by measuring behavioral and cerebral (fMRI) responses in human participants predicting goals of observed actions, while manipulating postural congruency between their own body posture and postures of the observed agents. Behaviorally, predicting action goals is facilitated when the body posture of the observer matches the posture achieved by the observed agent at the end of his action (action's goal posture). Cerebrally, this perceptual postural congruency effect modulates activity in a portion of the left intraparietal sulcus that has previously been shown to be involved in updating neural representations of one's own limb posture during action planning. This intraparietal area showed stronger responses when the goal posture of the observed action did not match the current body posture of the observer. These results add two novel elements to the notion that perceiving actions relies on the same predictive mechanism as planning actions. First, the predictions implemented by this mechanism are based on the current physical configuration of the body. Second, during both action planning and action observation, these predictions pertain to the goal state of the action.

Dynamic Simulation and Analysis of Human Walking Mechanism

NASA Astrophysics Data System (ADS)

Azahari, Athirah; Siswanto, W. A.; Ngali, M. Z.; Salleh, S. Md.; Yusup, Eliza M.

2017-01-01

Behaviour such as gait or posture may affect a person with the physiological condition during daily activities. The characteristic of human gait cycle phase is one of the important parameter which used to described the human movement whether it is in normal gait or abnormal gait. This research investigates four types of crouch walking (upright, interpolated, crouched and severe) by simulation approach. The assessment are conducting by looking the parameters of hamstring muscle joint, knee joint and ankle joint. The analysis results show that based on gait analysis approach, the crouch walking have a weak pattern of walking and postures. Short hamstring and knee joint is the most influence factor contributing to the crouch walking due to excessive hip flexion that typically accompanies knee flexion.

First-Person Perspective Virtual Body Posture Influences Stress: A Virtual Reality Body Ownership Study

PubMed Central

Bergström, Ilias; Kilteni, Konstantina; Slater, Mel

2016-01-01

In immersive virtual reality (IVR) it is possible to replace a person’s real body by a life-sized virtual body that is seen from first person perspective to visually substitute their own. Multisensory feedback from the virtual to the real body (such as the correspondence of touch and also movement) can also be present. Under these conditions participants typically experience a subjective body ownership illusion (BOI) over the virtual body, even though they know that it is not their real one. In most studies and applications the posture of the real and virtual bodies are as similar as possible. Here we were interested in whether the BOI is diminished when there are gross discrepancies between the real and virtual body postures. We also explored whether a comfortable or uncomfortable virtual body posture would induce feelings and physiological responses commensurate with the posture. We carried out an experiment with 31 participants in IVR realized with a wide field-of-view head-mounted display. All participants were comfortably seated. Sixteen of them were embodied in a virtual body designed to be in a comfortable posture, and the remainder in an uncomfortable posture. The results suggest that the uncomfortable body posture led to lesser subjective BOI than the comfortable one, but that participants in the uncomfortable posture experienced greater awareness of their autonomic physiological responses. Moreover their heart rate, heart rate variability, and the number of mistakes in a cognitive task were associated with the strength of their BOI in the uncomfortable posture: greater heart rate, lower heart rate variability and more mistakes were associated with higher levels of the BOI. These findings point in a consistent direction—that the BOI over a body that is in an uncomfortable posture can lead to subjective, physiological and cognitive effects consistent with discomfort that do not occur with the BOI over a body in a comfortable posture. PMID:26828365

A rapid rotation to an inverted seated posture inhibits muscle force, activation, heart rate and blood pressure.

PubMed

Johar, Pramod; Grover, Varun; DiSanto, Mario C; Button, Duane C; Behm, David G

2013-08-01

Although previous studies have demonstrated neuromuscular and cardiovascular changes with slow inversion rates, emergencies, such as overturned vehicles and helicopters can occur rapidly. The purpose of this study was to investigate changes in neuromuscular and cardiovascular responses with rapid (1 s) and slower (3 s) transitions from upright to inverted seated positions. Twenty-two subjects performed separate and concurrent unilateral elbow flexion and leg extension maximal voluntary contractions (MVCs) for 6 s in an upright seated position and when inverted with 1 and 3 s rotations. Elbow flexion and leg extension force; biceps, triceps, quadriceps and hamstrings electromyographic (EMG) activity, heart rate (HR), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured. Whether the elbow flexion or leg extension contractions occurred concurrently or individually, significant (p < 0.05) decreases in MVC force and EMG activity were found when inverted within 1 and 3 s rotations as compared to upright. Triceps and hamstrings EMG activity (p < 0.05) decreased when inverted within 1 s rotation as compared to upright. Following rotation, the maintenance of the inverted position (3-6 s timepoint) resulted in a significant (p < 0.05) increase in leg extension MVC as compared to the initial second of rotation to inversion. HR, SBP and DBP demonstrated (p < 0.001) decreases when inverted within 1 and 3 s rotations as compared to upright. In conclusion, this is the first study to show that irrespective of rotation speed, inversion inhibited neuromuscular and cardiovascular responses, similar to the more deliberate, slower rotation of previous inversion studies.

Bubble and macroaggregate methods differ in detection of blood flow through intrapulmonary arteriovenous anastomoses in upright and supine hypoxia in humans.

PubMed

Duke, Joseph W; Elliott, Jonathan E; Laurie, Steven S; Voelkel, Thomas; Gladstone, Igor M; Fish, Mathews B; Lovering, Andrew T

2017-12-01

Blood flow through intrapulmonary arteriovenous anastomoses (Q̇ IPAVA ) increases in healthy humans breathing hypoxic gas and is potentially dependent on body position. Previous work in subjects breathing room air has shown an effect of body position when Q̇ IPAVA is detected with transthoracic saline contrast echocardiography (TTSCE). However, the potential effect of body position on Q̇ IPAVA has not been investigated when subjects are breathing hypoxic gas or with a technique capable of quantifying Q̇ IPAVA . Thus the purpose of this study was to quantify the effect of body position on Q̇ IPAVA when breathing normoxic and hypoxic gas at rest. We studied Q̇ IPAVA with TTSCE and quantified Q̇ IPAVA with filtered technetium-99m-labeled macroaggregates of albumin ( 99m Tc-MAA) in seven healthy men breathing normoxic and hypoxic (12% O 2 ) gas at rest while supine and upright. On the basis of previous work using TTSCE, we hypothesized that the quantified Q̇ IPAVA would be greatest with hypoxia in the supine position. We found that Q̇ IPAVA quantified with 99m Tc-MAA significantly increased while subjects breathed hypoxic gas in both supine and upright body positions (ΔQ̇ IPAVA  = 0.7 ± 0.4 vs. 2.5 ± 1.1% of cardiac output, respectively). Q̇ IPAVA detected with TTSCE increased from normoxia in supine hypoxia but not in upright hypoxia (median hypoxia bubble score of 2 vs. 0, respectively). Surprisingly, Q̇ IPAVA magnitude was greatest in upright hypoxia, when Q̇ IPAVA was undetectable with TTSCE. These findings suggest that the relationship between TTSCE and 99m Tc-MAA is more complex than previously appreciated, perhaps because of the different physical properties of bubbles and MAA in solution. NEW & NOTEWORTHY Using saline contrast bubbles and radiolabeled macroaggregrates (MAA), we detected and quantified, respectively, hypoxia-induced blood flow through intrapulmonary arteriovenous anastomoses (Q̇ IPAVA ) in supine and upright body positions in healthy men. Upright hypoxia resulted in the largest magnitude of Q̇ IPAVA quantified with MAA but the lowest Q̇ IPAVA detected with saline contrast bubbles. These surprising results suggest that the differences in physical properties between saline contrast bubbles and MAA in blood may affect their behavior in vivo.

Regional Blood Volume and Peripheral Blood Flow in the Postural Tachycardia Syndrome

PubMed Central

Stewart, Julian M.; Montgomery, Leslie D.

2015-01-01

Variants of postural tachycardia syndrome (POTS) are associated with increased (“high flow” POTS, HFP), decreased (“low flow POTS”, LFP) and normal (“normal flow POTS”, NFP) blood flow measured in the lower extremities while supine. We propose that postural tachycardia is related to thoracic hypovolemia during orthostasis but that the patterns of peripheral blood flow relate to different mechanisms for thoracic hypovolemia. We studied 37 POTS patients aged 14-21 years: 14 LFP, 15 NFP and 8 HFP patients and 12 healthy control subjects. Peripheral blood flow was measured supine by venous occlusion strain gauge plethysmography of the forearm and calf in order to subgroup patients. Using indocyanine green techniques we showed decreased cardiac index (CI) and increased total peripheral resistance (TPR) in LFP, increased CI and decreased TPR in HFP, and unchanged CI and TPR in NFP while supine compared to control subjects. Blood volume tended to be decreased in LFP compared to control subjects. We used impedance plethysmography to assess regional blood volume redistribution during upright tilt. Thoracic blood volume decreased while splanchnic, pelvic and leg blood volumes increased for all subjects during orthostasis, but were markedly lower than control for all POTS groups. Splanchnic volume was increased in NFP and LFP. Pelvic blood volume was increased in HFP only. Calf volume was increased above control in HFP and LFP. The results support the hypothesis of [at least] three pathophysiologic variants of POTS distinguished by peripheral blood flow related to characteristic changes in regional circulations. The data demonstrate enhanced thoracic hypovolemia during upright tilt and confirm that POTS is related to inadequate cardiac venous return during orthostasis. PMID:15117717

Response of the upper esophageal sphincter to esophageal distension is affected by posture, velocity, volume, and composition of the infusate.

PubMed

Babaei, Arash; Dua, Kulwinder; Naini, Sohrab Rahimi; Lee, Justin; Katib, Omar; Yan, Ke; Hoffmann, Raymond; Shaker, Reza

2012-04-01

Studies of the pressure response of the upper esophageal sphincter (UES) to simulated or spontaneous gastroesophageal reflux have shown conflicting results. These discrepancies could result from uncontrolled influence of variables such as posture, volume, and velocity of distension. We characterized in humans the effects of these variables on UES pressure response to esophageal distension. We studied 12 healthy volunteers (average, 27 ± 5 years old; 6 male) using concurrent esophageal infusion and high-resolution manometry to determine UES, lower esophageal sphincter, and intraesophageal pressure values. Reflux events were simulated by distal esophageal injections of room temperature air and water (5, 10, 20, and 50 mL) in individuals in 3 positions (upright, supine, and semisupine). Frequencies of various UES responses were compared using χ(2) analysis. Multinomial logistical regression analysis was used to identify factors that determine the UES response. UES contraction and relaxation were the overriding responses to esophageal water and air distension, respectively, in a volume-dependent fashion (P < .001). Water-induced UES contraction and air-induced UES relaxation were the predominant responses among individuals in supine and upright positions, respectively (P < .001). The prevalence of their respective predominant response significantly decreased in the opposite position. Proximal esophageal dp/dt significantly and independently differentiated the UES response to infusion with water or air. The UES response to esophageal distension is affected by combined effects of posture (spatial orientation of the esophagus), physical properties, and volume of refluxate, as well as the magnitude and rate of increase in intraesophageal pressure. The UES response to esophageal distension can be predicted using a model that incorporates these factors. Copyright © 2012 AGA Institute. Published by Elsevier Inc. All rights reserved.

The Design and Use of Animal Models for Translational Research in Bone Tissue Engineering and Regenerative Medicine

DTIC Science & Technology

2010-01-07

many domains: mechanical load bearing and force transmission, immunogologic function (leukogenesis and lymphogenesis), mass transport (erythrogenesis...models including NHPs) does not reproduce upright posture of bipedal humans with respect to axial compression and rotational loading in the human lumbar...Schell, M. Mehta, M. A. Schuetz, G. N. Duda, D. W. Hutmacher. 2012. A Tissue Engineering Solution for Segmental Defect Regeneration in Load - Bearing

Are automatic postural responses in patients with Parkinson's disease abnormal due to their stooped posture?

PubMed

Bloem, B R; Beckley, D J; van Dijk, J G

1999-02-01

Abnormal automatic postural responses are thought to contribute to balance impairment in Parkinson's disease. However, because postural responses are modifiable by stance, we have speculated that some postural abnormalities in patients with Parkinson's disease are secondary to their stooped stance. We have studied this assumption by assessing automatic postural responses in 30 healthy subjects who were instructed either to stand upright or to assume a typical parkinsonian posture. During both conditions, subjects received 20 serial 4 degrees 'toe-up' rotational perturbations from a supporting forceplate. We recorded short-latency (SL) and medium-latency (ML) responses from stretched gastrocnemius muscles and long-latency (LL) responses from shortened tibialis anterior muscles. We also assessed changes in the center of foot pressure (CFP) and the center of gravity (COG). The results were qualitatively compared to a previously described group of patients with Parkinson's disease who, under these circumstances, typically have large ML responses, small LL responses and insufficient voluntary postural corrections, accompanied by a slow rate of backward CFP displacement and an increased posterior COG displacement. The stooped posture resulted in unloading of medial gastrocnemius muscles and loading of tibialis anterior muscles. Onset latencies of stretch responses in gastrocnemius muscles were delayed in stooped subjects, but the onset of LL responses was markedly reduced. Amplitudes of both ML and LL responses were reduced in stooped subjects. Prestimulus COG and, to a lesser extent, CFP were shifted forwards in stooped subjects. Posterior COG displacement and the rate of backward CFP displacement were diminished in stooped subjects. Voluntary postural corrections were unchanged while standing stooped. These results indicate that some postural abnormalities of patients with Parkinson's disease (most notably the reduced LL responses) can be reproduced in healthy subjects mimicking a stooped parkinsonian posture. Other postural abnormalities (most notably the increased ML responses and insufficient voluntary responses) did not appear in stooped controls and may contribute to balance impairment in Parkinson's disease.

Control of vertical posture while elevating one foot to avoid a real or virtual obstacle.

PubMed

Ida, Hirofumi; Mohapatra, Sambit; Aruin, Alexander

2017-06-01

The purpose of this study is to investigate the control of vertical posture during obstacle avoidance in a real versus a virtual reality (VR) environment. Ten healthy participants stood upright and lifted one leg to avoid colliding with a real obstacle sliding on the floor toward a participant and with its virtual image. Virtual obstacles were delivered by a head mounted display (HMD) or a 3D projector. The acceleration of the foot, center of pressure, and electrical activity of the leg and trunk muscles were measured and analyzed during the time intervals typical for early postural adjustments (EPAs), anticipatory postural adjustments (APAs), and compensatory postural adjustments (CPAs). The results showed that the peak acceleration of foot elevation in the HMD condition decreased significantly when compared with that of the real and 3D projector conditions. Reduced activity of the leg and trunk muscles was seen when dealing with virtual obstacles (HMD and 3D projector) as compared with that seen when dealing with real obstacles. These effects were more pronounced during APAs and CPAs. The onsets of muscle activities in the supporting limb were seen during EPAs and APAs. The observed modulation of muscle activity and altered patterns of movement seen while avoiding a virtual obstacle should be considered when designing virtual rehabilitation protocols.

Lumbar posture and trunk muscle activation during a typing task when sitting on a novel dynamic ergonomic chair.

PubMed

O'Sullivan, Kieran; McCarthy, Raymond; White, Alison; O'Sullivan, Leonard; Dankaerts, Wim

2012-01-01

Low back pain (LBP) is a common musculoskeletal disorder and prolonged sitting often aggravates LBP. A novel dynamic ergonomic chair ('Back App'), which facilitates less hip flexion while sitting on an unstable base has been developed. This study compared lumbar posture and trunk muscle activation on this novel chair with a standard backless office chair. Twelve painfree participants completed a typing task on both chairs. Lumbar posture and trunk muscle activation were collected simultaneously and were analysed using paired t-tests. Sitting on the novel dynamic chair significantly (p < 0.05) reduced both lumbar flexion and the activation of one back muscle (Iliocostalis Lumborum pars Thoracis). The discomfort experienced was mild and was similar (p > 0.05) between chairs. Maintaining lordosis with less muscle activation during prolonged sitting could reduce the fatigue associated with upright sitting postures. Studies with longer sitting durations, and in people with LBP, are required. Sitting on a novel dynamic chair resulted in less lumbar flexion and less back muscle activation than sitting on a standard backless office chair during a typing task among pain-free participants. Facilitating lordotic sitting with less muscle activation may reduce the fatigue and discomfort often associated with lordotic sitting postures.

Computerized back postural assessment in physiotherapy practice: Intra-rater and inter-rater reliability of the MIDAS system.

PubMed

McAlpine, R T; Bettany-Saltikov, J A; Warren, J G

2009-01-01

Assessment of spinal posture during physiotherapy practice is routine, yet few objective measures exist to this end. The Middlesbrough Integrated Digital Assessment System (MIDAS) is a low cost portable system able to record 3D information on posture. The purpose of this study was to assess both the intra-rater and inter-rater reliability of the MIDAS system. Twenty-five healthy subjects were recruited. A repeated measures design was used to record fifteen pre-palpated landmarks on the back of each subject. To limit the sources of variability, the principal researcher palpated the landmarks for each subject. Each of three raters took two measurements on each subject in a standardized upright posture. X (medio-lateral), Y (antero-posterior) and Z (height) landmark positions were recorded via a computer interface. Both intra-rater agreement (mean ICCs - rater 1 r=0.970, rater 2 r=0.965 and rater 3 r=0.965, p< 0.001) and inter-rater agreement (mean ICCs r=0.967, p< 0.001) was very high between repeated measures and between markers. Error values for the z-axis (height) were the lowest. The MIDAS demonstrated both high inter-rater and intra-rater reliability and provides an objective method for the assessment of posture in physiotherapy practice.

Head movements and postures as pain behavior

PubMed Central

Al-Hamadi, Ayoub; Limbrecht-Ecklundt, Kerstin; Walter, Steffen; Traue, Harald C.

2018-01-01

Pain assessment can benefit from observation of pain behaviors, such as guarding or facial expression, and observational pain scales are widely used in clinical practice with nonverbal patients. However, little is known about head movements and postures in the context of pain. In this regard, we analyze videos of three publically available datasets. The BioVid dataset was recorded with healthy participants subjected to painful heat stimuli. In the BP4D dataset, healthy participants performed a cold-pressor test and several other tasks (meant to elicit emotion). The UNBC dataset videos show shoulder pain patients during range-of-motion tests to their affected and unaffected limbs. In all videos, participants were sitting in an upright position. We studied head movements and postures that occurred during the painful and control trials by measuring head orientation from video over time, followed by analyzing posture and movement summary statistics and occurrence frequencies of typical postures and movements. We found significant differences between pain and control trials with analyses of variance and binomial tests. In BioVid and BP4D, pain was accompanied by head movements and postures that tend to be oriented downwards or towards the pain site. We also found differences in movement range and speed in all three datasets. The results suggest that head movements and postures should be considered for pain assessment and research. As additional pain indicators, they possibly might improve pain management whenever behavior is assessed, especially in nonverbal individuals such as infants or patients with dementia. However, in advance more research is needed to identify specific head movements and postures in pain patients. PMID:29444153

Temporal patterns of physical activity in Olympic dinghy racing.

PubMed

Legg, S; Mackie, H; Smith, P

1999-12-01

The objective of the present study was to determine the temporal patterns of physical activity in four classes of Olympic racing dinghy. Descriptive. A field (on-water) study. Nineteen elite New Zealand sailors (fifteen male and four female). Not applicable. The temporal pattern (duration and frequency) and nature of the physical activities of each sailor during each leg of simulated races were recorded on video tape and subsequently systematically quantified and categorised using notational analysis. The accumulated percentage of total leg time spent sitting (upright or leaning backwards), hiking (upright or fully extended) whilst trimming and whilst pumping the mainsheet and for the time spent on rig adjustments, tacking and gybing were calculated for both up-wind and off-wind sailing. When sailing up-wind, the most time was spent hiking upright (average 29-66% of total leg time) while trimming the mainsheet. During off-wind sailing, sailors spent the most time sitting upright while trimming the mainsheet (average 29-55% total leg time). Hiking upright while trimming the mainsheet was executed the greatest number of times (average 15.8-23.9) when sailing up-wind and sitting upright while trimming was executed the most times (average 3.5-7.4) when sailing off-wind. The most lengthy continuous activity was hiking upright while trimming the mainsheet when sailing up-wind (9-18 seconds) and sitting upright while trimming the mainsheet when sailing off-wind (17-34 seconds). The most physically demanding aspect of Olympic yacht racing is hiking. It occurs for the majority of up-wind legs when the wind starts to exceed approximately 8 knots. The only respite that the sailor gets from hiking is during tacking, rig adjustments or sitting in-board for brief periods when the wind is low. Sustained hiking tends to last for no more than approximately 20 seconds before the sailor changes to either a more extended or more upright hiking posture. The physical demands during off-wind sailing are generally less, except for a greater requirement for power in the arms and shoulders to pump the mainsheet in order to assist the dinghy in accelerating down waves. The findings of the present study are directly applicable to the design of sailing specific physical conditioning programmes for Olympic class sailors.

Prevalence of incorrect body posture in children and adolescents with overweight and obesity.

PubMed

Maciałczyk-Paprocka, Katarzyna; Stawińska-Witoszyńska, Barbara; Kotwicki, Tomasz; Sowińska, Anna; Krzyżaniak, Alicja; Walkowiak, Jarosław; Krzywińska-Wiewiorowska, Małgorzata

2017-05-01

The ever increasing epidemics of overweight and obesity in school children may be one of the reasons of the growing numbers of children with incorrect body posture. The purpose of the study was the assessment of the prevalence of incorrect body posture in children and adolescents with overweight and obesity in Poznań, Poland. The population subject to study consisted of 2732 boys and girls aged 3-18 with obesity, overweight, and standard body mass. The assessment of body mass was performed based on BMI, adopting Cole's cutoff values. The evaluation of body posture was performed according to the postural error chart based on criteria complied by professor Dega. The prevalence rates of postural errors were significantly higher among children and adolescents with overweight and obesity than among the group with standard body mass. In the overweight group, it amounted to 69.2% and in the obese group to 78.6%.  The most common postural deviations in obese children and adolescents were valgus knees and flat feet. Overweight and obesity in children and adolescents, predisposing to higher incidence of some types of postural errors, call for prevention programs addressing both health problems. What is Known: • The increase in the prevalence of overweight and obesity among children and adolescents has drawn attention to additional health complications which may occur in this population such as occurrence of incorrect body posture. What is New: • The modified chart of postural errors proved to be an effective tool in the assessment of incorrect body posture. • This chart may be used in the assessment of posture during screening tests and prevention actions at school.

The head and neck discomfort of autonomic failure: an unrecognized aetiology of headache

NASA Technical Reports Server (NTRS)

Robertson, D.; Kincaid, D. W.; Haile, V.; Robertson, R. M.

1994-01-01

Information concerning the frequency, severity, character, location, duration, diurnal pattern of headache and ancillary symptoms were obtained in 25 patients with autonomic failure and 44 control subjects. Precipitating and ameliorating factors were identified. Autonomic failure patients had more head and neck discomfort than controls. Their discomfort was much more likely to localize in the occiput, nape of the neck and shoulder, compared with controls. There was a greater tendency for the discomfort to occur in the morning and after meals. It was sometimes less than 5 min in duration and was often associated with dimming, blurring, or tunnelling of vision. It was provoked by upright posture and relieved by lying down. Patients with severe autonomic failure and orthostatic hypotension often present with a posture-dependent headache or neck pain. Because the relationship of these symptoms to posture is often not recognized, the fact that these findings may signal an underlying autonomic disorder is underappreciated, and the opportunity to consider this aetiology for the headache may be missed.

Static body postural misalignment in individuals with temporomandibular disorders: a systematic review

PubMed Central

Chaves, Thaís C.; Turci, Aline M.; Pinheiro, Carina F.; Sousa, Letícia M.; Grossi, Débora B.

2014-01-01

BACKGROUND: The association between body postural changes and temporomandibular disorders (TMD) has been widely discussed in the literature, however, there is little evidence to support this association. OBJECTIVES: The aim of the present study was to conduct a systematic review to assess the evidence concerning the association between static body postural misalignment and TMD. METHOD: A search was conducted in the PubMed/Medline, Embase, Lilacs, Scielo, Cochrane, and Scopus databases including studies published in English between 1950 and March 2012. Cross-sectional, cohort, case control, and survey studies that assessed body posture in TMD patients were selected. Two reviewers performed each step independently. A methodological checklist was used to evaluate the quality of the selected articles. RESULTS: Twenty studies were analyzed for their methodological quality. Only one study was classified as a moderate quality study and two were classified as strong quality studies. Among all studies considered, only 12 included craniocervical postural assessment, 2 included assessment of craniocervical and shoulder postures,, and 6 included global assessment of body posture. CONCLUSION: There is strong evidence of craniocervical postural changes in myogenous TMD, moderate evidence of cervical postural misalignment in arthrogenous TMD, and no evidence of absence of craniocervical postural misalignment in mixed TMD patients or of global body postural misalignment in patients with TMD. It is important to note the poor methodological quality of the studies, particularly those regarding global body postural misalignment in TMD patients. PMID:25590441

Relationship between body composition and postural control in prepubertal overweight/obese children: A cross-sectional study.

PubMed

Villarrasa-Sapiña, Israel; Álvarez-Pitti, Julio; Cabeza-Ruiz, Ruth; Redón, Pau; Lurbe, Empar; García-Massó, Xavier

2018-02-01

Excess body weight during childhood causes reduced motor functionality and problems in postural control, a negative influence which has been reported in the literature. Nevertheless, no information regarding the effect of body composition on the postural control of overweight and obese children is available. The objective of this study was therefore to establish these relationships. A cross-sectional design was used to establish relationships between body composition and postural control variables obtained in bipedal eyes-open and eyes-closed conditions in twenty-two children. Centre of pressure signals were analysed in the temporal and frequency domains. Pearson correlations were applied to establish relationships between variables. Principal component analysis was applied to the body composition variables to avoid potential multicollinearity in the regression models. These principal components were used to perform a multiple linear regression analysis, from which regression models were obtained to predict postural control. Height and leg mass were the body composition variables that showed the highest correlation with postural control. Multiple regression models were also obtained and several of these models showed a higher correlation coefficient in predicting postural control than simple correlations. These models revealed that leg and trunk mass were good predictors of postural control. More equations were found in the eyes-open than eyes-closed condition. Body weight and height are negatively correlated with postural control. However, leg and trunk mass are better postural control predictors than arm or body mass. Finally, body composition variables are more useful in predicting postural control when the eyes are open. Copyright © 2017 Elsevier Ltd. All rights reserved.

The effect of embodied emotive states on cognitive categorization.

PubMed

Price, Tom F; Harmon-Jones, Eddie

2010-12-01

Research has uncovered that positive affect broadens cognitive categorization. The motivational dimensional model, however, posits that positive affect is not a unitary construct with only one cognitive consequence. Instead, this model puts forth that there are different positive affects varying in approach motivational intensity. According to this model, only positive affects lower in motivational intensity should broaden cognitive processes, whereas positive affects higher in motivational intensity should narrow cognitive processes. Consistent with these predictions, high approach positive affect has been shown to narrow attention, whereas low approach positive affect has been shown to broaden it (Gable & Harmon-Jones, 2008). High approach positive affect, therefore, might narrow categorization. Two experiments investigated this possibility by having participants respond to cognitive categorization tasks in 3 body postures designed to elicit different levels of approach motivation: reclining backward, which should evoke low approach motivation; sitting upright, which should evoke moderate approach motivation; and leaning forward, which should evoke high approach motivation. Participants smiled while in each posture in order to experience positive affect. Experiment 1 provided initial support for the idea that high approach positive affect narrows categorization and low approach positive affect broadens categorization. Experiment 2 replicated these findings with improved smiling instructions. These results extend previous work by showing that the motivational model's predictions hold for basic attentional processes as well as higher level cognitive processes such as categorization.

Mammalian spinal biomechanics: postural support in seated macaques.

PubMed

Gal, Julianna

2002-06-01

The aim of this study was to investigate whether the ligamentous lumbar vertebral column of a macaque could potentially provide passive mechanical support to the weight of the head, upper body and forelimbs during upright sitting. The seated flexed curvature of the lumbar spine of Macaca sylvana was estimated from a photograph and was partitioned equally among the lumbar-lumbar intervertebral joints. This flexed curvature was compared with the hyper-extended profile of the unloaded excised ligamentous spine of a related species (Macaca fascicularis) and used to calculate changes in intervertebral angle from the unloaded excised state to the loaded in vivo state. Changes in intervertebral angle were then used to calculate the net flexion moment required to bend the spine from the unloaded curvature to the seated curvature. The moment arm of the ventrally displaced weight of the head, upper body and forelimbs was estimated and used to calculate a corresponding net force. It was found that this force corresponded to approximately 18 % of the total body weight of the 2.34 kg sample animal. This compares with a likely fractional body weight of approximately 30-40 % for the head, upper body and forelimbs of these primates. Therefore, approximately half of the ventral flexion moment associated with the combined weight of the head, upper body and forelimbs during sitting in these animals may be supported by the passive mechanical properties associated with the ligamentous lumbar spine. This represents a potential means of relieving muscular effort and saving metabolic energy.

REVIEW: Restoring standing capabilities with feedback control of functional neuromuscular stimulation following spinal cord injury

PubMed Central

Nataraj, Raviraj; Audu, Musa L.; Triolo, Ronald J.

2017-01-01

This paper reviews the field of feedback control for neuroprosthesis systems that restore advanced standing function to individuals with spinal cord injury. Investigations into closed-loop control of standing by functional neuromuscular stimulation (FNS) have spanned three decades. The ultimate goal for FNS standing control systems is to facilitate hands free standing and enabling the user to perform manual functions at self-selected leaning positions. However, most clinical systems for home usage currently only provide basic upright standing using preprogrammed stimulation patterns. To date, online modulation of stimulation to produce advanced standing functions such as balance against postural disturbances or the ability to assume leaning postures have been limited to simulation and laboratory investigations. While great technological advances have been made in biomechanical sensing and interfaces for neuromuscular stimulation, further progress is still required for finer motor control by FNS. Another major challenge is the development of sophisticated control schemes that produce the necessary postural adjustments, adapt against accelerating muscle fatigue, and consider volitional actions of the intact upper-body of the user. Model-based development for novel control schemes are proven and sensible approaches to prototype and test the basic operating efficacy of potentially complex and multi-faceted control systems. The major considerations for further innovation of such systems are summarized in this paper prior to describing the evolution of closed-loop FNS control of standing from previous works. Finally, necessary emerging technologies to for implementing FNS feedback control systems for standing are identified. These technological advancements include novel electrodes that more completely and selectively activate paralyzed musculature and implantable sensors and stimulation modules for flexible neuroprosthesis system deployment. PMID:28215399

Restoring standing capabilities with feedback control of functional neuromuscular stimulation following spinal cord injury.

PubMed

Nataraj, Raviraj; Audu, Musa L; Triolo, Ronald J

2017-04-01

This paper reviews the field of feedback control for neuroprosthesis systems that restore advanced standing function to individuals with spinal cord injury. Investigations into closed-loop control of standing by functional neuromuscular stimulation (FNS) have spanned three decades. The ultimate goal for FNS standing control systems is to facilitate hands free standing and enabling the user to perform manual functions at self-selected leaning positions. However, most clinical systems for home usage currently only provide basic upright standing using preprogrammed stimulation patterns. To date, online modulation of stimulation to produce advanced standing functions such as balance against postural disturbances or the ability to assume leaning postures have been limited to simulation and laboratory investigations. While great technological advances have been made in biomechanical sensing and interfaces for neuromuscular stimulation, further progress is still required for finer motor control by FNS. Another major challenge is the development of sophisticated control schemes that produce the necessary postural adjustments, adapt against accelerating muscle fatigue, and consider volitional actions of the intact upper-body of the user. Model-based development for novel control schemes are proven and sensible approaches to prototype and test the basic operating efficacy of potentially complex and multi-faceted control systems. The major considerations for further innovation of such systems are summarized in this paper prior to describing the evolution of closed-loop FNS control of standing from previous works. Finally, necessary emerging technologies to for implementing FNS feedback control systems for standing are identified. These technological advancements include novel electrodes that more completely and selectively activate paralyzed musculature and implantable sensors and stimulation modules for flexible neuroprosthesis system deployment. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Vibration-related extrusion of capillary blood from the calf musculature depends upon directions of vibration of the leg and of the gravity vector.

PubMed

Çakar, Halil Ibrahim; Doğan, Serfiraz; Kara, Sadık; Rittweger, Jörn; Rawer, Rainer; Zange, Jochen

2017-06-01

In this study, we investigated the effects of vibration of the whole lower leg on the content and the oxygenation of hemoglobin in the unloaded relaxed lateral gastrocnemius muscle. Vibration was applied orthogonal to and in parallel with leg axis to examine whether the extrusion of blood depends on an alignment of main vessel direction, axis of vibration and gravity. The blood volume in the muscles was altered by horizontal and 30° upright body posture. Fifteen male subjects were exposed to 4 sets of experiments with both vibration directions and both tilt angles applied in permutated order. The absence of voluntary muscular activity and the potential occurrence of compound action potentials by stretch reflexes were monitored using electromyography. Total hemoglobin and tissue saturation index were measured with near infrared spectroscopy. Changes of lower leg circumference were measured with strain gauge system placed around the calf. Vibration caused decrease in tHb and increase in TSI indicating extrusion of predominantly venous blood from the muscle. In 30° tilted position, muscles contained more blood at baseline and vibration ejected more blood from the muscle compared with horizontal posture (p < 0.01). At 30° tilting deeper drop in tHb and steeper increase in TSI (p < 0.01) were observed when vibration was applied in parallel with the length axis of muscle. It is concluded that the vibration extrudes more blood in 30° head up posture and the vibration applied in parallel with the length axis of the muscle is more effective than orthogonal vibration.

Relation of blood volume and blood pressure in orthostatic intolerance

NASA Technical Reports Server (NTRS)

Jacob, G.; Biaggioni, I.; Mosqueda-Garcia, R.; Robertson, R. M.; Robertson, D.

1998-01-01

A complex but crucial relationship exists between blood volume and blood pressure in human subjects; it has been recognized that in essential hypertension, renovascular hypertension, and pheochromocytoma, the relationship between plasma volume and diastolic blood pressure is an inverse one. This phenomenon has not been studied in individuals with low normal and reduced blood pressures. Orthostatic intolerance is a commonly encountered abnormality in blood pressure regulation often associated with tachycardia in the standing position. Most of these patients have varying degrees of reduced blood volume. We tested the hypothesis that the relationship previously found between plasma volume and diastolic blood pressure in pressor states would also hold in orthostatic intolerance. We studied 16 patients with a history of symptomatic orthostatic intolerance associated with an elevation in plasma norepinephrine in the upright posture and hypovolemia in 9 patients and normovolemia in 7 patients. Our studies demonstrate an inverse relationship between plasma volume and diastolic blood pressure in patients with orthostatic intolerance. This finding also holds for the change in diastolic blood pressure in response to upright posture. In this relationship, patients with orthostatic intolerance with high plasma norepinephrine resemble those with essential hypertension, renovascular hypertension, and pheochromocytoma. We conclude that in a variety of conditions at both ends of the blood pressure spectrum, the seemingly paradoxical association of hypovolemia and diastolic blood pressure is preserved.

Estimation of Radiation Dose for a Sitting Phantom Using PIMAL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akkurt, Hatice; Eckerman, Keith F

2007-01-01

To assess the radiation dose in different configurations when needed (e.g., occupational exposure or public exposure in a radiologically significant event), the mathematical phantom has recently been revised to enable freely moving abilities for arms and legs. The revised phantom is called PIMAL: Phantom with Moving Arms and Legs. Additionally, a graphical user interface has been developed to assist the analyst with input preparation and output manipulation. To investigate the impact of the phantom configuration on the estimated organ doses, PIMAL has been used in a different posture than the standard vertical-upright position. In this paper, the estimated organ andmore » effective dose values for a representative posture, the phantom in a sitting position, compared with those for the phantom in standing position, are presented.« less

[Postural tachycardia syndrome (PoTS): An up-to-date].

PubMed

Astudillo, L; Laure, A; Fabry, V; Pugnet, G; Maury, P; Labrunée, M; Sailler, L; Pavy-Le Traon, A

2018-06-13

Postural tachycardia syndrome (PoTS) is a multifactorial syndrome defined by an increase in heart rate ≥30bpm, within 10minutes of standing (or during a head up tilt test to at least 60°), in absence of orthostatic hypotension. It is associated with symptoms of cerebral hypoperfusion that are worse when upright and improve in supine position. Patients have an intense fatigue with a high incidence on quality of life. This syndrome can be explained by many pathophysiological mechanisms. It can be associated with Ehlers-Danlos disease and some autoimmune disorders. The treatment is based on nonpharmacological measures and treatment with propranolol, fludrocortisone or midodrine. Copyright © 2018 Société Nationale Française de Médecine Interne (SNFMI). Published by Elsevier Masson SAS. All rights reserved.

Dental occlusion, body posture and temporomandibular disorders: where we are now and where we are heading for.

PubMed

Manfredini, D; Castroflorio, T; Perinetti, G; Guarda-Nardini, L

2012-06-01

The aim of this investigation was to perform a review of the literature dealing with the issue of relationships between dental occlusion, body posture and temporomandibular disorders (TMD). A search of the available literature was performed to determine what the current evidence is regarding: (i) The physiology of the dental occlusion-body posture relationship, (ii) The relationship of these two topics with TMD and (iii) The validity of the available clinical and instrumental devices (surface electromyography, kinesiography and postural platforms) to measure the dental occlusion-body posture-TMD relationship. The available posturographic techniques and devices have not consistently found any association between body posture and dental occlusion. This outcome is most likely due to the many compensation mechanisms occurring within the neuromuscular system regulating body balance. Furthermore, the literature shows that TMD are not often related to specific occlusal conditions, and they also do not have any detectable relationships with head and body posture. The use of clinical and instrumental approaches for assessing body posture is not supported by the wide majority of the literature, mainly because of wide variations in the measurable variables of posture. In conclusion, there is no evidence for the existence of a predictable relationship between occlusal and postural features, and it is clear that the presence of TMD pain is not related with the existence of measurable occluso-postural abnormalities. Therefore, the use instruments and techniques aiming to measure purported occlusal, electromyographic, kinesiographic or posturographic abnormalities cannot be justified in the evidence-based TMD practice. © 2012 Blackwell Publishing Ltd.

The effect of vision on postural strategies in Prader-Willi patients.

PubMed

Cimolin, Veronica; Galli, Manuela; Vismara, Luca; Grugni, Graziano; Priano, Lorenzo; Capodaglio, Paolo

2011-01-01

The aim of this study was to quantify the role of visual contribution in patients with Prader-Willi syndrome (PWS) on balance maintenance using a force platform. We enrolled 14 individuals with PWS free from conditions associated with impaired balance, 44 obese (OG) and 20 healthy controls (CG). Postural sway was measured for 60s while standing on a force platform (Kistler, CH; acquisition frequency: 500 Hz) integrated with a video system. Patients maintained an upright standing position with Open Eyes (OE) and then with Closed Eyes (CE). The ratio between the value of the parameter under OE and CE conditions was measured. Under OE condition PWS and OG were characterized by higher postural instability than CG, with the PWS group showing poorer balance capacity than OG. The Romberg ratio showed that while OG and CG had lower balance without vision, PWS maintained the same performance changing from OE to CE. The integration of different sensory inputs appears similar in OG and CG with higher postural stability under OE than CE. Balance in PWS is not influenced by the elimination of visual input. Copyright © 2011 Elsevier Ltd. All rights reserved.

The addition of body armor diminishes dynamic postural stability in military soldiers.

PubMed

Sell, Timothy C; Pederson, Jonathan J; Abt, John P; Nagai, Takashi; Deluzio, Jennifer; Wirt, Michael D; McCord, Larry J; Lephart, Scott M

2013-01-01

Poor postural stability has been identified as a risk factor for lower extremity musculoskeletal injury. The additional weight of body armor carried by Soldiers alters static postural stability and may predispose Soldiers to lower extremity musculoskeletal injuries. However, static postural stability tasks poorly replicate the dynamic military environment, which places considerable stress on the postural control system during tactical training and combat. Therefore, the purpose of this study was to examine the effects of body armor on dynamic postural stability during single-leg jump landings. Thirty-six 101st Airborne Division (Air Assault) Soldiers performed single-leg jump landings in the anterior direction with and without wearing body armor. The dynamic postural stability index and the individual stability indices (medial-lateral stability index, anterior-posterior stability index, and vertical stability index) were calculated for each condition. Paired sample t-tests were performed to determine differences between conditions. Significant differences existed for the medial-lateral stability index, anterior-posterior stability index, vertical stability index, and dynamic postural stability index (p < 0.05). The addition of body armor resulted in diminished dynamic postural stability, which may result in increased lower extremity injuries. Training programs should address the altered dynamic postural stability while wearing body armor in attempts to promote adaptations that will result in safer performance during dynamic tasks.

Undisturbed upright stance control in the elderly: Part 2. Postural-control impairments of elderly fallers.

PubMed

Berger, L; Chuzel, M; Buisson, G; Rougier, P

2005-09-01

A common way of predicting falling risks in elderly people can be to study center of pressure (CP) trajectories during undisturbed upright stance maintenance. By estimating the difference between CP and center of gravity (CG) motions (CP - CGv), one can estimate the neuromuscular activity. The results of this study, which included 34 sedentary elderly persons aged over 75 years (21 fallers and 13 nonfallers), demonstrated significantly increased CGh and CP - CGv motions in both axes for the fallers. In addition, the fallers presented larger CGh motions in the mediolateral axis, suggesting an enlarged loading-unloading mechanism, which could have reflected the adoption of a step-initiating strategy. As highlighted by fractional Brownian motion modeling, the distance covered by the CP - CGv motions before the successive control mechanisms switched was enhanced for the fallers in both axes, therefore increasing the risk that the CG would be outside of the base of support.

Age-related disappearance of Mayer-like heart rate waves

NASA Technical Reports Server (NTRS)

Jarisch, W. R.; Ferguson, J. J.; Shannon, R. P.; Wei, J. Y.; Goldberger, A. L.

1987-01-01

The effect of age on the principal spectral components of heart rate obtained immediately after passive upright tilt was investigated in human subjects who underwent a 60-deg tilt over 9 sec. Two groups were examined, the first of which consisting of healthy male subjects aged 22-26 years, while the second was comprised of subjects aged 65-84 years on no medication; radiograms were recorded continuously beginning just prior to tilt until 3 min posttilt. The results of spectral analysis showed that elderly subjects did not exhibit the Mayer-like heart rate waves (the 0.07-0.09 Hz oscillations) that were present in the spectra of young subjects immediately after passive upright tilt. The findings are consistent with the concept of a 'dysautonomia of aging'. It is suggested that postural stress testing with spectral analysis of heart rate fluctuations may provide a useful way of assessing physiologic vs chronologic age.

A new method for sudden mechanical perturbation with axial load, to assess postural control in sitting and standing.

PubMed

Claus, Andrew P; Verrel, Julius; Pounds, Paul E I; Shaw, Renee C; Brady, Niamh; Chew, Min T; Dekkers, Thomas A; Hodges, Paul W

2016-05-03

Sudden application of load along a sagittal or coronal axis has been used to study trunk stiffness, but not axial (vertical) load. This study introduces a new method for sudden-release axial load perturbation. Prima facie validity was supported by comparison with standard mechanical systems. We report the response of the human body to axial perturbation in sitting and standing and within-day repeatability of measures. Load of 20% of body weight was released from light contact onto the shoulders of 22 healthy participants (10 males). Force input was measured via force transducers at shoulders, output via a force plate below the participant, and kinematics via 3-D motion capture. System identification was used to fit data from the time of load release to time of peak load-displacement, fitting with a 2nd-order mass-spring-damper system with a delay term. At peak load-displacement, the mean (SD) effective stiffness measured with this device for participants in sitting was 12.0(3.4)N/mm, and in standing was 13.3(4.2)N/mm. Peak force output exceeded input by 44.8 (10.0)% in sitting and by 30.4(7.9)% in standing. Intra-class correlation coefficients for within-day repeatability of axial stiffness were 0.58 (CI: -0.03 to 0.83) in sitting and 0.82(0.57-0.93) in standing. Despite greater degrees of freedom in standing than sitting, standing involved lesser time, downward displacement, peak output force and was more repeatable in defending upright postural control against the same axial loads. This method provides a foundation for future studies of neuromuscular control with axial perturbation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Assessment of effects of differences in trunk posture during Fowler’s position on hemodynamics and cardiovascular regulation in older and younger subjects

PubMed Central

Kubota, Satoshi; Endo, Yutaka; Kubota, Mitsue; Shigemasa, Tomohiko

2017-01-01

Background Downward shifts in blood volume with changing position generally cause tachycardic responses. Age-related decreases in vagal nerve activity could contribute to orthostatic hypotension in older individuals. Fowler’s position is a reclined position with the back between 30° and 60°, used to facilitate breathing, eating, and other routine daily activities in frail and elderly patients. Objective This study examined whether stroke volume (SV) was higher and heart rate (HR) lower in Fowler’s position with an upright upper trunk than in Fowler’s position with the whole trunk upright in both older and younger subjects, based on the assumption that lower HR would result from reduced sympathetic activation in older individuals. Methods We assessed hemodynamics and HR variability from electrocardiography, noninvasive arterial pressure and impedance cardiography in 11 younger male subjects (age range, 20–22 years) and 11 older male subjects (age range, 64–79 years), using three positions: supine, or Fowler’s positions with either 30° of lower trunk inclination and 60° of upper trunk inclination (UT60) or 60° of whole trunk inclination (WT60). Comparisons were then made between age groups and between positions. Results Reductions in SV and tachycardic response were smaller with UT60 than with WT60, in both younger and older subjects. In addition, reduced tachycardic response with upright upper trunk appeared attributable to decreased vagal withdrawal in younger subjects and to reduced sympathetic activation in older subjects. Conclusion Our findings indicate that an upright upper trunk during Fowler’s position allowed maintenance of SV and inhibited tachycardic response compared to an upright whole trunk regardless of age, although the autonomic mechanisms underlying tachycardic responses differed between younger and older adults. An upright upper trunk in Fowler’s position might help to reduce orthostatic stress and facilitate routine activities and conversation in frail patients. PMID:28408809

Assessment of effects of differences in trunk posture during Fowler's position on hemodynamics and cardiovascular regulation in older and younger subjects.

PubMed

Kubota, Satoshi; Endo, Yutaka; Kubota, Mitsue; Shigemasa, Tomohiko

2017-01-01

Downward shifts in blood volume with changing position generally cause tachycardic responses. Age-related decreases in vagal nerve activity could contribute to orthostatic hypotension in older individuals. Fowler's position is a reclined position with the back between 30° and 60°, used to facilitate breathing, eating, and other routine daily activities in frail and elderly patients. This study examined whether stroke volume (SV) was higher and heart rate (HR) lower in Fowler's position with an upright upper trunk than in Fowler's position with the whole trunk upright in both older and younger subjects, based on the assumption that lower HR would result from reduced sympathetic activation in older individuals. We assessed hemodynamics and HR variability from electrocardiography, noninvasive arterial pressure and impedance cardiography in 11 younger male subjects (age range, 20-22 years) and 11 older male subjects (age range, 64-79 years), using three positions: supine, or Fowler's positions with either 30° of lower trunk inclination and 60° of upper trunk inclination (UT60) or 60° of whole trunk inclination (WT60). Comparisons were then made between age groups and between positions. Reductions in SV and tachycardic response were smaller with UT60 than with WT60, in both younger and older subjects. In addition, reduced tachycardic response with upright upper trunk appeared attributable to decreased vagal withdrawal in younger subjects and to reduced sympathetic activation in older subjects. Our findings indicate that an upright upper trunk during Fowler's position allowed maintenance of SV and inhibited tachycardic response compared to an upright whole trunk regardless of age, although the autonomic mechanisms underlying tachycardic responses differed between younger and older adults. An upright upper trunk in Fowler's position might help to reduce orthostatic stress and facilitate routine activities and conversation in frail patients.

Response of the kallikrein-kinin and renin-angiotensin systems to saline infusion and upright posture.

PubMed Central

Wong, P Y; Talamo, R C; Williams, G H; Colman, R W

1975-01-01

The possibility that bradykinin, a potent vasodilator, might be a physiological antagonist of the renin-angiotensin system was investigated. 11 norman subjects, ranging in age from 21 to 33 yr were studied. Seven of the subjects were given a 10 meq sodium, 100 meq potassium, 2500 ml isocaloric diet. After metabolic balance was achieved, they were infused with either 1 liter of 5 per cent glucose over 2 h or 2 liters of 0.9 per cent saline over 4 h. During the infusions, plasma renin activity (PRA), angiotensin II (A II), prekallikrein, bradykinin, and aldosterone levels were frequently determined. Plasma prekallikrein and kallikrein inhibitor did not change during the infusion of either glucose or saline. In subjects receiving saline, plasma bradykinin fell from 3.9 plus or minus 1.5 (SEM) ng/ml at 0 min to 0.93 plus or minus 0.2 at 30 min and 0.95 plus or minus 0.3 at 120 min. These changes paralleled the decrease in PRA over the same period (7.9 plus or minus 1.3 ng/ml/h to 5.6 plus or minus 0.8 at 30 min and 3.5 plus or minus 0.7 at 120 min). Similarly, A II fell from 113 plus or minus 12 pg/ml to 62 plus or minus 10 and 48 plus or minus 5, respectively, at 30 and 120 min. In contrast, the control group infused with glucose showed no change in bradykinin, A II, or PRA. Another four subjects were given a constant 200 meq sodium/100 meq potassium isocaloric diet. After metabolic balance was achieved, they were kept supine and fasting overnight. At 9 a.m. they assumed an upright position and began walking a fixed distance (200 ft) at a normal rate (3-4 ft/s). Plasma prekallikrein and kallikrein inhibitor did not change during the posture study. The plasma bradykinin rose from a base line of 0.54 plus or minus 0.01 (SEM) ng/ml to 0.96 plus or minus 0.13 at 20 min. 0.77 plus or minus 0.18 at 60 min, and 0.96 plus or minus 0.07 at 120 min. These changes parallel the increase in PRA over the same period (1.65 plus or minus 3.3 ng/ml/h to 3.6 plus or minus 0.85 at 20 min, 5.3 plus or minus 0.9 at 60 min, and 5.35 plus or minus 0.55 at 120 min). Likewise, the A II rose from 32.5 plus or minus 1.82 pg/ml to 50.8 plus or minus 3.6 at 20 min, 54.3 plus or minus 3.2 at 60 min, and 61.3 plus or minus 5.9 at 120 min. Thus, in sodium-depleted individuals, saline infusion produces a rapid fall of plasma bradykinin at a rate similar to that observed for a II and PRA. Conversely, in sodium-loaded individuals, assumption of upright posture leads to a parallel rise in A II, TPRA, and bradykinin. These studies indicate that there is a close correlation of bradykinin levels with renin activity and angiotensin II, in both acute sodium loading and assumption of upright posture, suggesting that these two systems may be physiologically interrelated. PMID:235559

Emotional and movement-related body postures modulate visual processing

PubMed Central

Borhani, Khatereh; Làdavas, Elisabetta; Maier, Martin E.; Avenanti, Alessio

2015-01-01

Human body postures convey useful information for understanding others’ emotions and intentions. To investigate at which stage of visual processing emotional and movement-related information conveyed by bodies is discriminated, we examined event-related potentials elicited by laterally presented images of bodies with static postures and implied-motion body images with neutral, fearful or happy expressions. At the early stage of visual structural encoding (N190), we found a difference in the sensitivity of the two hemispheres to observed body postures. Specifically, the right hemisphere showed a N190 modulation both for the motion content (i.e. all the observed postures implying body movements elicited greater N190 amplitudes compared with static postures) and for the emotional content (i.e. fearful postures elicited the largest N190 amplitude), while the left hemisphere showed a modulation only for the motion content. In contrast, at a later stage of perceptual representation, reflecting selective attention to salient stimuli, an increased early posterior negativity was observed for fearful stimuli in both hemispheres, suggesting an enhanced processing of motivationally relevant stimuli. The observed modulations, both at the early stage of structural encoding and at the later processing stage, suggest the existence of a specialized perceptual mechanism tuned to emotion- and action-related information conveyed by human body postures. PMID:25556213

Cognition and balance control: does processing of explicit contextual cues of impending perturbations modulate automatic postural responses?

PubMed

Coelho, Daniel Boari; Teixeira, Luis Augusto

2017-08-01

Processing of predictive contextual cues of an impending perturbation is thought to induce adaptive postural responses. Cueing in previous research has been provided through repeated perturbations with a constant foreperiod. This experimental strategy confounds explicit predictive cueing with adaptation and non-specific properties of temporal cueing. Two experiments were performed to assess those factors separately. To perturb upright balance, the base of support was suddenly displaced backwards in three amplitudes: 5, 10 and 15 cm. In Experiment 1, we tested the effect of cueing the amplitude of the impending postural perturbation by means of visual signals, and the effect of adaptation to repeated exposures by comparing block versus random sequences of perturbation. In Experiment 2, we evaluated separately the effects of cueing the characteristics of an impending balance perturbation and cueing the timing of perturbation onset. Results from Experiment 1 showed that the block sequence of perturbations led to increased stability of automatic postural responses, and modulation of magnitude and onset latency of muscular responses. Results from Experiment 2 showed that only the condition cueing timing of platform translation onset led to increased balance stability and modulation of onset latency of muscular responses. Conversely, cueing platform displacement amplitude failed to induce any effects on automatic postural responses in both experiments. Our findings support the interpretation of improved postural responses via optimized sensorimotor processes, at the same time that cast doubt on the notion that cognitive processing of explicit contextual cues advancing the magnitude of an impending perturbation can preset adaptive postural responses.

Acute effects of Dry Immersion on kinematic characteristics of postural corrective responses

NASA Astrophysics Data System (ADS)

Sayenko, D. G.; Miller, T. F.; Melnik, K. A.; Netreba, A. I.; Khusnutdinova, D. R.; Kitov, V. V.; Tomilovskaya, E. S.; Reschke, M. F.; Gerasimenko, Y. P.; Kozlovskaya, I. B.

2016-04-01

Impairments in balance control are inevitable following exposure to microgravity. However, the role of particular sensory system in postural disorders at different stages of the exposure to microgravity still remains unknown. We used a method called Dry Immersion (DI), as a ground-based model of microgravity, to elucidate the effects of 6-h of load-related afferent inputs on kinematic characteristics of postural corrective responses evoked by pushes to the chest of different intensities during upright standing. The structure of postural corrective responses was altered following exposure to DI, which was manifested by: (1) an increase of the ankle and knee flexion during perturbations of medium intensity, (2) the lack of the compensatory hip extension, as well as diminished knee and ankle flexion with a further increase of the perturbation intensity to submaximal level. We suggest that the lack of weight-bearing increases the reactivity of the balance control system, whereas the ability to scale the responses proportionally to the perturbation intensity decreases. Disrupted neuromuscular coordination of postural corrective responses following DI can be attributed to adaptive neural modifications on the spinal and cortical levels. The present study provides evidence that even a short-term lack of load-related afferent inputs alters kinematic patterns of postural corrective responses, and can result in decreased balance control. Because vestibular input is not primarily affected during the DI exposure, our results indicate that activity and the state of the load-related afferents play critical roles in balance control following real or simulated microgravity.

A wrist-walker exhibiting no "Uner Tan Syndrome": a theory for possible mechanisms of human devolution toward the atavistic walking patterns.

PubMed

Tan, Uner

2007-01-01

After discovering two families with handicapped children exhibiting the "Uner Tan syndrome," the author discovered a man exhibiting only wrist-walking with no primitive mental abilities including language. According to his mother, he had an infectious disease with high fever as a three months old baby; as a result, the left leg had been paralyzed after a penicilline injection. This paralysis most probably resulted from a viral disease, possibly poliomyelitis. He is now (2006) 36 years old; the left leg is flaccid and atrophic, with no tendon reflexes; however, sensation is normal. The boy never stood up on his feet while maturing. The father forced him to walk upright using physical devices and making due exercises, but the child always rejected standing upright and walking in erect posture; he always preferred wrist-walking; he expresses that wrist-walking is much more comfortable for him than upright-walking. He is very strong now, making daily body building exercises, and walking quite fast using a "three legs," although he cannot stand upright. Mental status, including the language and conscious experience, is quite normal. There was no intra-familiar marriage as in the two families mentioned earlier, and there is no wrist-walking in his family and relatives. There were no cerebellar signs and symptoms upon neurological examination. The brain-MRI was normal; there was no atrophy in cerebellum and vermis. It was concluded that there may be sporadic wrist-walkers exhibiting no "Uner Tan Syndrome." The results suggest that the cerebellum has nothing to do with human wrist-walking, which may rather be an atavistic trait appearing from time to time in normal individuals, indicating a live model for human reverse evolution. It was concluded that pure quadrupeds may sporadically appear due to random fluctuations in genotypes and/or environmental factors (hormonal or nutritional); the human development following the human evolution may be stopped in the stage of transition from quadrupedality to bipedality. That is, the activity of the philogenetically youngest supraspinal centers for bipedal walking responsible for suppression of the older supraspinal centers for quadrupedal gait may be interrupted at the atavistic level due to genetic and/or environmental factors. Consequently, it is assumed that these individuals prefer their natural wrist-walking to move around more quickly and efficiently.

Embodying animals: Body-part compatibility in mammalian, reptile and aves classes.

PubMed

Pacione, Sandra M; Welsh, Timothy N

2015-09-01

The purpose of the present study was to determine how humans code homologous body parts of nonhuman mammal, reptilian, and aves animals with respect to the representation of the human body. To this end, participants completed body-part compatibility tasks in which responses were executed to colored targets that were superimposed over the upper limbs, lower limbs or head of different animals in different postures. In Experiment 1, the images were of meekats and lizards in bipedal and quadrupedal postures. In Experiment 2, the images were of a human, a penguin, and an owl in a bipedal posture with upper limbs stretched out. Overall, the results revealed that the limbs of nonhuman mammals (meerkat and human) were consistently mapped onto the homologous human body parts only when the mammals were in a bipedal posture. Specifically, body-part compatibility effects emerged for the human and the meerkat in a bipedal posture, but not the meerkat in the quadrupedal posture. Further, consistent body-part compatibility effects were not observed for the lizard in the quadrupedal posture or for the lizard, penguin, or owl in a bipedal posture. The pattern of results suggests that the human bipedal body representation may distinguish taxonomical classes and is most highly engaged when viewing homologous body parts of mammalian animals. Copyright © 2015 Elsevier B.V. All rights reserved.

Scan posture definition and hip girth measurement: the impact on clothing design and body scanning.

PubMed

Gill, Simeon; Parker, Christopher J

2017-08-01

Ergonomic measurement is central to product design and development; especially for body worn products and clothing. However, there is a large variation in measurement definitions, complicated by new body scanning technology that captures measurements in a posture different to traditional manual methods. Investigations of hip measurement definitions in current clothing measurement practices supports analysis of the effect of scan posture and hip measurement definition on the circumferences of the hip. Here, the hip girth is a key clothing measurement that is not defined in current body scanning measurement standards. Sixty-four participants were scanned in the standard scan posture of a [TC] 2 body scanner, and also in a natural posture similar to that of traditional manual measurement collection. Results indicate that scan posture affects hip girth circumferences, and that some current clothing measurement practices may not define the largest lower body circumference. Recommendations are made concerning how the hip is defined in measurement practice and within body scanning for clothing product development. Practitioner Summary: The hip girth is an important measurement in garment design, yet its measurement protocol is not currently defined. We demonstrate that body posture during body scanning affects hip circumferences, and that current clothing measurement practices may not define the largest lower body circumference. This paper also provides future measurement practice recommendations.

Platypnea-orthodeoxia due to fat embolism.

PubMed

Gourgiotis, Stavros; Aloizos, Stavros; Gakis, Christos; Salemis, Nikolaos S

2011-01-01

Platypnea-orthodeoxia is an uncommon syndrome that is characterized by dyspnea relieved by recumbency and deoxygenation following a change from a recumbent to an upright posture. We herein describe a case of platypnea-orthodeoxia in a 75-year-old man after a surgical restoration of a bitrochanteric fracture of his right femur. However, in this extremely rare case, none of the current known anatomical or functional conditions which can cause platypnea-orthodeoxia had been diagnosed. We strongly believe that this syndrome could be also the result of fat embolism.

Suspected lead toxicosis in a bald eagle

USGS Publications Warehouse

Jacobson, E.; Carpenter, J.W.; Novilla, M.

1977-01-01

An immature bald eagle (Haliaeetus leucocephalus) was submitted to the University of Maryland, College Park, for clinical examination. The bird was thin, had green watery feces, and was unable to maintain itself in upright posture. Following radiography, the bird went into respiratory distress and died. Numerous lead shot were recovered from the gizzard, and chemical analysis of liver and kidney tissue revealed 22.9 and 11.3 ppm lead, respectively. The clinical signs, necropsy findings, and chemical analysis of the eagle were compatible with lead toxicosis.

Body-Earth Mover's Distance: A Matching-Based Approach for Sleep Posture Recognition.

PubMed

Xu, Xiaowei; Lin, Feng; Wang, Aosen; Hu, Yu; Huang, Ming-Chun; Xu, Wenyao

2016-10-01

Sleep posture is a key component in sleep quality assessment and pressure ulcer prevention. Currently, body pressure analysis has been a popular method for sleep posture recognition. In this paper, a matching-based approach, Body-Earth Mover's Distance (BEMD), for sleep posture recognition is proposed. BEMD treats pressure images as weighted 2D shapes, and combines EMD and Euclidean distance for similarity measure. Compared with existing work, sleep posture recognition is achieved with posture similarity rather than multiple features for specific postures. A pilot study is performed with 14 persons for six different postures. The experimental results show that the proposed BEMD can achieve 91.21% accuracy, which outperforms the previous method with an improvement of 8.01%.

Subjects with temporomandibular joint disc displacement do not feature any peculiar changes in body posture.

PubMed

Rocha, T; Castro, M A; Guarda-Nardini, L; Manfredini, D

2017-02-01

The presence of body posture changes among patients with temporomandibular disorders (TMD) has been a controversial topic in dentistry. Based on that, the aim of this study was to assess postural features of pain-free subjects with internal derangement of the temporomandibular joint (TMJ), viz. disc displacement, when compared to subjects with normal disc position. A total of 21 subjects with unilateral, pain-free TMJ disc displacement (DD) and 21 subjects without any TMD signs of symptoms were assessed for body posture changes by means of posturographic evaluation of several body segments and postural balance reactions through the centre of mass during jaw movements using a balance platform. Posturographic measurements showed the absence of any significant differences between the two groups in any of the outcome parameters. Similarly, all balance platform responses to mandibular movements were not different between groups. There are no significant differences in body posture between subjects with and without unilateral disc displacement in the temporomandibular joint. Such observations, indicating a well-preserved postural balance in the presence of TMJ internal derangement, put into serious question the potential influence of TMJ disorders on whole body posture and viceversa. © 2016 John Wiley & Sons Ltd.

Body size and lower limb posture during walking in humans.

PubMed

Hora, Martin; Soumar, Libor; Pontzer, Herman; Sládek, Vladimír

2017-01-01

We test whether locomotor posture is associated with body mass and lower limb length in humans and explore how body size and posture affect net joint moments during walking. We acquired gait data for 24 females and 25 males using a three-dimensional motion capture system and pressure-measuring insoles. We employed the general linear model and commonality analysis to assess the independent effect of body mass and lower limb length on flexion angles at the hip, knee, and ankle while controlling for sex and velocity. In addition, we used inverse dynamics to model the effect of size and posture on net joint moments. At early stance, body mass has a negative effect on knee flexion (p < 0.01), whereas lower limb length has a negative effect on hip flexion (p < 0.05). Body mass uniquely explains 15.8% of the variance in knee flexion, whereas lower limb length uniquely explains 5.4% of the variance in hip flexion. Both of the detected relationships between body size and posture are consistent with the moment moderating postural adjustments predicted by our model. At late stance, no significant relationship between body size and posture was detected. Humans of greater body size reduce the flexion of the hip and knee at early stance, which results in the moderation of net moments at these joints.

Dynamic multi-segmental postural control in patients with chronic non-specific low back pain compared to pain-free controls: A cross-sectional study.

PubMed

McCaskey, Michael A; Wirth, Brigitte; Schuster-Amft, Corina; de Bruin, Eling D

2018-01-01

Reduced postural control is thought to contribute to the development and persistence of chronic non-specific low back pain (CNLBP). It is therefore frequently assessed in affected patients and commonly reported as the average amount of postural sway while standing upright under a variety of sensory conditions. These averaged linear outcomes, such as mean centre of pressure (CP) displacement or mean CP surface areas, may not reflect the true postural status. Adding nonlinear outcomes and multi-segmental kinematic analysis has been reported to better reflect the complexity of postural control and may detect subtler postural differences. In this cross-sectional study, a combination of linear and nonlinear postural parameters were assessed in patients with CNLBP (n = 24, 24-75 years, 9 females) and compared to symptom-free controls (CG, n = 34, 22-67 years, 11 females). Primary outcome was postural control measured by variance of joint configurations (uncontrolled manifold index, UI), confidence ellipse surface areas (CEA) and approximate entropy (ApEn) of CP dispersion during the response phase of a perturbed postural control task on a swaying platform. Secondary outcomes were segment excursions and clinical outcome correlates for pain and function. Non-parametric tests for group comparison with P-adjustment for multiple comparisons were conducted. Principal component analysis was applied to identify patterns of segmental contribution in both groups. CNLBP and CG performed similarly with respect to the primary outcomes. Comparison of joint kinematics revealed significant differences of hip (P < .001) and neck (P < .025) angular excursion, representing medium to large group effects (r's = .36 - .51). Significant (P's < .05), but moderate correlations of ApEn (r = -.42) and UI (r = -.46) with the health-related outcomes were observed. These findings lend further support to the notion that averaged linear outcomes do not suffice to describe subtle postural differences in CNLBP patients with low to moderate pain status.

Feasibility of magnetic resonance imaging (MRI) in obtaining nucleus pulposus (NP) water content with changing postures.

PubMed

Nazari, Jalil; Pope, Malcolm H; Graveling, Richard A

2015-05-01

Opportunities to evaluate spinal loading in vivo are limited and a large majority of studies on the mechanical functions of the spine have been in vitro cadaveric studies and/or models based on many assumptions that are difficult to validate. The purpose of this study was to investigate the feasibility of magnetic resonance imaging (MRI) in obtaining nucleus pulposus (NP) water content measurements with changing postures. MRI studies were conducted on 25 healthy males with no history of low back pain (age 20-38). The L1 to S1 intradiscal levels were imaged in supine, sitting and standing postures using an upright 0.6 Tesla magnet, where a set of H2O: D2O7 phantoms were mounted on the back of the subjects. A calibration curve, provided from these phantoms, was applied to the absolute proton density image, yielding a pixel-by-pixel map of the water content of the NP. The NP at all levels showed a highly significant water loss (p<0.001) in sitting and standing postures compared with the supine posture. A trend towards higher levels of water was observed at all levels in the standing posture relative to sitting postures, however statistically significant differences were found only at L4-L5 and L5-S1 levels. This study demonstrates that variations in water content of the NP in different postures are in agreement with those determined from published invasive disc pressure measurements. The result of study demonstrates the feasibility of using MRI to determine the water content of the NP with changing postures and to use these data to evaluate spinal loading in these postures. This measurement method of water content by quantitative MR imaging could become a powerful tool for both clinical and ergonomic applications. The proposed methodology does not require invasive pressure measurement techniques. Copyright © 2015 Elsevier Inc. All rights reserved.

Postural orientation in microgravity depends on straightening up movement performed

NASA Astrophysics Data System (ADS)

Vaugoyeau, Marianne; Assaiante, Christine

2009-08-01

Whether the vertical body orientation depends on the initial posture and/or the type of straightening up movement is the main question raised in this paper. Another objective was to specify the compensatory role of visual input while adopting an erected posture during microgravity. The final body orientation was analysed in microgravity during parabolic flights. After either (1) straightening up movement from a crouching or (2) a sitting posture, with and without vision. The main results are the following: (1) a vertical erected final posture is correctly achieved after sit to stand movement, whereas all subjects were tilted forward after straightening up from a crouching posture and (2) vision may contribute to correct final posture. These results suggest the existence of a re-weighting of the remaining sensory information, visual information, contact cutaneous cues and proprioceptive information under microgravity condition. We can put forward the alternative hypothesis that the control of body orientation under microgravity condition may also be achieved on the basis of a postural body scheme, that seems to be dependant on the type of movement and/ or the initial position of the whole body.

Evaluation of Neutral Body Posture on Shuttle Mission STS-57 (SPACEHAB-1). Revision

NASA Technical Reports Server (NTRS)

Mount, Frances E.; Whitmore, Mihriban; Stealey, Sheryl L.

2003-01-01

Research has shown that the space environment induces physiological changes in the human body, such as fluid shifts in the upper body and chest cavity, spinal lengthening, muscular atrophy, space motion sickness, cardiopulmonary deconditioning, and bone mass loss, as well as some changes in visual perception. These require a period of adaptation and can substantially affect both crew member performance and posture. These physiological effects, when work activities are conducted, have been known to impact the body's center of gravity, reach, flexibility, and dexterity. All these aspects of posture must be considered to safely and efficiently design space systems and hardware. NASA has documented its microgravity body posture in the Man-Systems Integration Standards (MSIS); the space community uses the MSIS posture to design workstations and tools for space application. However, the microgravity body posture should be further investigated for several reasons, including small sample size in previous studies, possible imprecision, and lack of detail. JSC undertook this study to investigate human body posture exhibited under microgravity conditions. STS-57 crew members were instructed to assume a relaxed posture that was not oriented to any work area or task. Crew members were asked to don shorts and tank tops and to be blindfolded while data were recorded. Video data were acquired once during the mission from each of the six crew members. No one crew member exhibited the typical NBP called out in the MSIS; one composite posture is not adequate. A range of postures may be more constructive for design purposes. Future evaluations should define precise posture requirements for workstation, glove box, maintenance, foot-restraint, and handhold activities.

Postural abnormalities and contraversive pushing following right hemisphere brain damage.

PubMed

Lafosse, C; Kerckhofs, E; Vereeck, L; Troch, M; Van Hoydonck, G; Moeremans, M; Sneyers, C; Broeckx, J; Dereymaeker, L

2007-06-01

We investigated the presence of postural abnormalities in a consecutive sample of stroke patients, with either left or right brain damage, in relation to their perceived body position in space. The presence or absence of posture-related symptoms was judged by two trained therapists and subsequently analysed by hierarchical classes analysis (HICLAS). The subject classes resulting from the HICLAS model were further validated with respect to posture-related measurements, such as centre of gravity position and head position, as well as measurements related to the postural body scheme, such as the perception of postural and visual verticality. The results of the classification analysis clearly demonstrated a relation between the presence of right brain damage and abnormalities in body geometry. The HICLAS model revealed three classes of subjects: The first class contained almost all the patients without neglect and without any signs of contraversive pushing. They were mainly characterised by a normal body axis in any position. The second class were all neglect patients but predominantly without any contraversive pushing. The third class contained right brain damaged patients, all showing neglect and mostly exhibiting contraversive pushing. The patients in the third class showed a clear resistance to bringing the weight over to the ipsilesional side when the therapist attempted to make the subject achieve a vertical posture across the midline. The clear correspondence between abnormalities of the observed body geometry and the tilt of the subjective postural and visual vertical suggests that a patient's postural body geometry is characterised by leaning towards the side of space where he/she feels aligned with an altered postural body scheme. The presence of contraversive pushing after right brain damage points in to a spatial higher-order processing deficit underlying the higher frequency and severity of the axial postural abnormalities found after right brain lesions.

Hearts, neck posture and metabolic intensity of sauropod dinosaurs.

PubMed Central

Seymour, R S; Lillywhite, H B

2000-01-01

Hypothesized upright neck postures in sauropod dinosaurs require systemic arterial blood pressures reaching 700 mmHg at the heart. Recent data on ventricular wall stress indicate that their left ventricles would have weighed 15 times those of similarly sized whales. Such dimensionally, energetically and mechanically disadvantageous ventricles were highly unlikely in an endothermic sauropod. Accessory hearts or a siphon mechanism, with sub-atmospheric blood pressures in the head, were also not feasible. If the blood flow requirements of sauropods were typical of ectotherms, the left-ventricular blood volume and mass would have been smaller; nevertheless, the heart would have suffered the serious mechanical disadvantage of thick walls. It is doubtful that any large sauropod could have raised its neck vertically and endured high arterial blood pressure, and it certainly could not if it had high metabolic rates characteristic of endotherms. PMID:11052540

Turning Configural Processing Upside Down: Part and Whole Body Postures

ERIC Educational Resources Information Center

Reed, Catherine L.; Stone, Valerie E.; Grubb, Jefferson D.; McGoldrick, John E.

2006-01-01

Like faces, body postures are susceptible to an inversion effect in untrained viewers. The inversion effect may be indicative of configural processing, but what kind of configural processing is used for the recognition of body postures must be specified. The information available in the body stimulus was manipulated. The presence and magnitude of…

Reversibility after inhaling salbutamol in different body postures in asthmatic children: a pilot study.

PubMed

Visser, R; van der Palen, J; de Jongh, F H C; Thio, B J

2015-04-01

Pulmonary medication is mostly delivered in the form of medical aerosols to minimize systemic side effects. A major drawback of inhaled medication is that the majority of inhaled particles impacts in the oropharynx at the sharp bend of the airway. Stretching the airway by a forward leaning body posture with the neck extended ("sniffing position") may improve pulmonary deposition and clinical effects. 41 asthmatic children who were planned for standard reversibility testing at the pulmonary function lab, alternately inhaled 200 μgr salbutamol with an Autohaler(®) in the standard or in the forward leaning body posture. Forced Expiratory Volume in 1 s (FEV1), Forced Vital Capacity (FVC), Peak Expiratory Flow (PEF), Mean Expiratory Flow at 25% of vital capacity (MEF25) and Mean Expiratory Flow at 75% of vital capacity (MEF75) were analysed. The children in the forward leaning body posture group showed a significantly higher mean FEV1 reversibility than the control group after inhalation of 200 μgr salbutamol (10.2% versus 4.1%, p = 0.019). Additionally, mean MEF75 was significantly more reversible in the forward leaning body posture group versus the standard body posture group (32.2% resp. 8.9%, p = 0.013). This pilot study showed a higher reversibility of FEV1 and MEF75 after inhaling salbutamol in a forward leaning body posture compared to the standard body posture in asthmatic children. This suggests that pulmonary effects of salbutamol can be improved by inhaling in a forward leaning body posture with the neck extended. This effect is possibly due to a higher pulmonary deposition of salbutamol and should be confirmed in a randomized controlled trial. Copyright © 2015 Elsevier Ltd. All rights reserved.

Postural control and low back pain in elite athletes comparison of static balance in elite athletes with and without low back pain.

PubMed

Oyarzo, Claudio A; Villagrán, Claudio R; Silvestre, Rony E; Carpintero, Pedro; Berral, Francisco J

2014-01-01

Although current research findings suggest that postural control or static balance is impaired in subjects with low back pain, few studies have specifically addressed the effect of low back pain on static balance in elite athletes. Forty-four athletes belonging to Chilean national teams took part in this study; 20 had low back pain and the remaining 24 were healthy controls. Displacement of the centre of pressure was analyzed by computerized platform posturography, using a standardized protocol; subjects were required to stand upright on both feet, with eyes first open then closed. The results showed that, athletes with low back pain used significantly more energy (p< 0.0182) and had a greater displacement of the centre of pressure (p< 0.005) with open eyes to control posture than healthy athletes. It may be concluded that static balance is impaired in elite athletes with low back pain and that analysis of two-footed stance provides a sensitive assessment of static balance in athletes.

Evolution of the hominoid vertebral column: The long and the short of it.

PubMed

Williams, Scott A; Russo, Gabrielle A

2015-01-01

The postcranial axial skeleton exhibits considerable morphological and functional diversity among living primates. Particularly striking are the derived features in hominoids that distinguish them from most other primates and mammals. In contrast to the primitive catarrhine morphotype, which presumably possessed an external (protruding) tail and emphasized more pronograde trunk posture, all living hominoids are characterized by the absence of an external tail and adaptations to orthograde trunk posture. Moreover, modern humans evolved unique vertebral features that satisfy the demands of balancing an upright torso over the hind limbs during habitual terrestrial bipedalism. Our ability to identify the evolutionary timing and understand the functional and phylogenetic significance of these fundamental changes in postcranial axial skeletal anatomy in the hominoid fossil record is key to reconstructing ancestral hominoid patterns and retracing the evolutionary pathways that led to living apes and modern humans. Here, we provide an overview of what is known about evolution of the hominoid vertebral column, focusing on the currently available anatomical evidence of three major transitions: tail loss and adaptations to orthograde posture and bipedal locomotion. © 2015 Wiley Periodicals, Inc.

Experimental neck muscle pain impairs standing balance in humans.

PubMed

Vuillerme, Nicolas; Pinsault, Nicolas

2009-02-01

Impaired postural control has been reported in patients with chronic neck pain of both traumatic and non-traumatic etiologies, but whether painful stimulation of neck muscle per se can affect balance control during quiet standing in humans remains unclear. The purpose of the present experiment was thus to investigate the effect of experimental neck muscle pain on standing balance in young healthy adults. To achieve this goal, 16 male university students were asked to stand upright as still as possible on a force platform with their eyes closed in two conditions of No pain and Pain of the neck muscles elicited by experimental painful electrical stimulation. Postural control and postural performance were assessed by the displacements of the center of foot pressure (CoP) and of the center of mass (CoM), respectively. The results showed increased CoP and CoM displacements variance, range, mean velocity, and mean and median frequencies in the Pain relative to the No pain condition. The present findings emphasize the destabilizing effect of experimental neck muscle pain per se, and more largely stress the importance of intact neck neuromuscular function on standing balance.

Evaluation of work posture and quantification of fatigue by Rapid Entire Body Assessment (REBA)

NASA Astrophysics Data System (ADS)

Rizkya, I.; Syahputri, K.; Sari, R. M.; Anizar; Siregar, I.

2018-02-01

Work related musculoskeletal disorders (MSDs), poor body postures, and low back injuries are the most common problems occurring in many industries including small-medium industries. This study presents assessment and evaluation of ergonomic postures of material handling worker. That evaluation was carried out using REBA (Rapid Entire Body Assessment). REBA is a technique to quantize the fatigue experienced by the worker while manually lifting loads. Fatigue due to abnormal work posture leads to complaints of labor-perceived pain. REBA methods were used to an assessment of working postures for the existing process by a procedural analysis of body postures involved. This study shows that parts of the body have a high risk of work are the back, neck, and upper arms with REBA score 9, so action should be taken as soon as possible. Controlling actions were implemented to those process with high risk then substantial risk reduction was achieved.

Evaluation of body posture in individuals with internal temporomandibular joint derangement.

PubMed

Munhoz, Wagner Cesar; Marques, Amélia Pasqual; de Siqueira, José Tadeu Tesseroli

2005-10-01

Temporomandibular dysfunctions (TMD) comprise a great number of disruptions that may affect the temporomandibular joint (TMJ), the masticatory muscles, or both. TMJ internal derangement is a specific type of TMD, of which the etiology and physiopathology are broadly unknown, but have been suggested to be linked to head, neck, and body posture factors. This study aimed at verifying possible relationships between body posture and TMJ internal derangements (TMJ-id), by comparing 30 subjects presenting typical TMJ-id signs to 20 healthy subjects. Subjects' clinical evaluations included anamnesis, stomatognatic system evaluation, and plotting analysis on body posture photographs. No statistically significant differences were found between the groups. Results do not support the assertion that body posture plays a role in causing or enhancing TMD; however, these results should be cautiously considered because of the small number of subjects evaluated and the many posture variables submitted to statistical procedures that lead to high standard deviations.

Effect of body position on vocal tract acoustics: Acoustic pharyngometry and vowel formants.

PubMed

Vorperian, Houri K; Kurtzweil, Sara L; Fourakis, Marios; Kent, Ray D; Tillman, Katelyn K; Austin, Diane

2015-08-01

The anatomic basis and articulatory features of speech production are often studied with imaging studies that are typically acquired in the supine body position. It is important to determine if changes in body orientation to the gravitational field alter vocal tract dimensions and speech acoustics. The purpose of this study was to assess the effect of body position (upright versus supine) on (1) oral and pharyngeal measurements derived from acoustic pharyngometry and (2) acoustic measurements of fundamental frequency (F0) and the first four formant frequencies (F1-F4) for the quadrilateral point vowels. Data were obtained for 27 male and female participants, aged 17 to 35 yrs. Acoustic pharyngometry showed a statistically significant effect of body position on volumetric measurements, with smaller values in the supine than upright position, but no changes in length measurements. Acoustic analyses of vowels showed significantly larger values in the supine than upright position for the variables of F0, F3, and the Euclidean distance from the centroid to each corner vowel in the F1-F2-F3 space. Changes in body position affected measurements of vocal tract volume but not length. Body position also affected the aforementioned acoustic variables, but the main vowel formants were preserved.

Using a System Identification Approach to Investigate Subtask Control during Human Locomotion

PubMed Central

Logan, David; Kiemel, Tim; Jeka, John J.

2017-01-01

Here we apply a control theoretic view of movement to the behavior of human locomotion with the goal of using perturbations to learn about subtask control. Controlling one's speed and maintaining upright posture are two critical subtasks, or underlying functions, of human locomotion. How the nervous system simultaneously controls these two subtasks was investigated in this study. Continuous visual and mechanical perturbations were applied concurrently to subjects (n = 20) as probes to investigate these two subtasks during treadmill walking. Novel application of harmonic transfer function (HTF) analysis to human motor behavior was used, and these HTFs were converted to the time-domain based representation of phase-dependent impulse response functions (ϕIRFs). These ϕIRFs were used to identify the mapping from perturbation inputs to kinematic and electromyographic (EMG) outputs throughout the phases of the gait cycle. Mechanical perturbations caused an initial, passive change in trunk orientation and, at some phases of stimulus presentation, a corrective trunk EMG and orientation response. Visual perturbations elicited a trunk EMG response prior to a trunk orientation response, which was subsequently followed by an anterior-posterior displacement response. This finding supports the notion that there is a temporal hierarchy of functional subtasks during locomotion in which the control of upper-body posture precedes other subtasks. Moreover, the novel analysis we apply has the potential to probe a broad range of rhythmic behaviors to better understand their neural control. PMID:28123365

Effect of administration method, animal weight and age on the intranasal delivery of drugs to the brain.

PubMed

Krishnan, Jishnu K S; Arun, Peethambaran; Chembukave, Bhadra; Appu, Abhilash P; Vijayakumar, Nivetha; Moffett, John R; Puthillathu, Narayanan; Namboodiri, Aryan M A

2017-07-15

The intranasal route of administration has proven to be an effective method for bypassing the blood brain barrier and avoiding first pass hepatic metabolism when targeting drugs to the brain. Most small molecules gain rapid access to CNS parenchyma when administered intranasally. However, bioavailability is affected by various factors ranging from the molecular weight of the drug to the mode of intranasal delivery. We examined the effects of animal posture, intranasal application method and animal weight and age on the delivery of radiolabeled pralidoxime ( 3 H-2-PAM) to the brain of rats. We found that using upright vs. supine posture did not significantly affect 3 H-2-PAM concentrations in different brain regions. Older animals with higher weights required increased doses to achieve the same drug concentration throughout the brain when compared to young animals with lower body weights. The use of an intranasal aerosol propelled delivery device mainly increased bioavailability in the olfactory bulbs, but did not reliably increase delivery of the drug to various other brain regions, and in some regions of the brain delivered less of the drug than simple pipette administration. In view of the emerging interest in the use of intranasal delivery of drugs to combat cognitive decline in old age, we tested effectiveness in very old rats and found the method to be as effective in the older rats. Copyright © 2017 Elsevier B.V. All rights reserved.

Posturography of ataxia induced by Coriolis- and Purkinje-effects.

PubMed

Fitger, C; Brandt, T

1982-02-01

Vestibular Coriolis- and Purkinje-effect, which are known to induce vertigo, were investigated with respect to body posture. One aim of this investigation was to provide information concerning clinical vertigo symptoms. Standing on a rotatable stabilometer, 25 healthy subjects had to execute lateral head tilts during (Coriolis), or after (Purkinje), rotation varied with different constant velocities. The conditions were varied with respect to eyes open vs. eyes closed, head upright vs. head tilt to the right and left, direction of rotation clockwise vs. counterclockwise, active vs. passive head tilt, and active vs. passive body rotation. The results supported the expectation that destabilization was less severe with open than with closed eyes and that sway amplitudes were increased after head tilt as well as with a higher velocity of rotation. The direction of the induced body shift was, as expected, opposite to the initial vestibular stimulus. A forward shift after stop without head tilt was frequently found, being independent of the previous direction of rotation. Reported perceptions coincided mostly not with the initial vestibular signal but rather with the actual movement of compensation. Active instead of passive movements did not produce clearly different effects. The Purkinje experiment appeared to be equivalent to the situation when a patient with an acute lesion of a horizontal vestibular canal bends his head. The stabilogram under this condition may allow a prediction of the side of the lesion.

Body size and lower limb posture during walking in humans

PubMed Central

Hora, Martin; Soumar, Libor; Pontzer, Herman; Sládek, Vladimír

2017-01-01

We test whether locomotor posture is associated with body mass and lower limb length in humans and explore how body size and posture affect net joint moments during walking. We acquired gait data for 24 females and 25 males using a three-dimensional motion capture system and pressure-measuring insoles. We employed the general linear model and commonality analysis to assess the independent effect of body mass and lower limb length on flexion angles at the hip, knee, and ankle while controlling for sex and velocity. In addition, we used inverse dynamics to model the effect of size and posture on net joint moments. At early stance, body mass has a negative effect on knee flexion (p < 0.01), whereas lower limb length has a negative effect on hip flexion (p < 0.05). Body mass uniquely explains 15.8% of the variance in knee flexion, whereas lower limb length uniquely explains 5.4% of the variance in hip flexion. Both of the detected relationships between body size and posture are consistent with the moment moderating postural adjustments predicted by our model. At late stance, no significant relationship between body size and posture was detected. Humans of greater body size reduce the flexion of the hip and knee at early stance, which results in the moderation of net moments at these joints. PMID:28192522

Orthostatic intolerance and motion sickness after parabolic flight

NASA Technical Reports Server (NTRS)

Schlegel, T. T.; Brown, T. E.; Wood, S. J.; Benavides, E. W.; Bondar, R. L.; Stein, F.; Moradshahi, P.; Harm, D. L.; Fritsch-Yelle, J. M.; Low, P. A.

2001-01-01

Because it is not clear that the induction of orthostatic intolerance in returning astronauts always requires prolonged exposure to microgravity, we investigated orthostatic tolerance and autonomic cardiovascular function in 16 healthy subjects before and after the brief micro- and hypergravity of parabolic flight. Concomitantly, we investigated the effect of parabolic flight-induced vomiting on orthostatic tolerance, R-wave-R-wave interval and arterial pressure power spectra, and carotid-cardiac baroreflex and Valsalva responses. After parabolic flight 1) 8 of 16 subjects could not tolerate 30 min of upright tilt (compared to 2 of 16 before flight); 2) 6 of 16 subjects vomited; 3) new intolerance to upright tilt was associated with exaggerated falls in total peripheral resistance, whereas vomiting was associated with increased R-wave-R-wave interval variability and carotid-cardiac baroreflex responsiveness; and 4) the proximate mode of new orthostatic failure differed in subjects who did and did not vomit, with vomiters experiencing comparatively isolated upright hypocapnia and cerebral vasoconstriction and nonvomiters experiencing signs and symptoms reminiscent of the clinical postural tachycardia syndrome. Results suggest, first, that syndromes of orthostatic intolerance resembling those developing after space flight can develop after a brief (i.e., 2-h) parabolic flight and, second, that recent vomiting can influence the results of tests of autonomic cardiovascular function commonly utilized in returning astronauts.

The effects of concurrent cognitive tasks on postural sway in healthy subjects.

PubMed

Mujdeci, Banu; Turkyilmaz, Didem; Yagcioglu, Suha; Aksoy, Songul

2016-01-01

Keeping balance of the upright stance is a highly practiced daily task for healthy adults and is effectively performed without overt attentional control in most. The purpose of this study was to examine the influence of concurrent cognitive tasks on postural sway in healthy participants. This was a prospective study. 20 healthy volunteer subjects were included. The cognitive and balance tasks were performed separately and then, concurrently. Postural control task consisted of 6 conditions (C) of the Sensory Organization Test. The cognitive task consisted of digit rehearsal task of varying presentation and varying levels of difficulty. A statistically significant difference was noted between dual task and no task for C1, C2, C3 and C4 Sensory Organization Test scores (p<0.05). There was no statistically significant difference between dual task versus non-task for C5, C6 and combined Sensory Organization Test scores (p>0.05). During dual task, increase has been determined in postural sway for C1, C2, C3 and C4 for all presentation modes and difficulty levels of the cognitive tasks. Copyright © 2015 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

Can Tai Chi and Qigong Postures Shape Our Mood? Toward an Embodied Cognition Framework for Mind-Body Research

PubMed Central

Osypiuk, Kamila; Thompson, Evan; Wayne, Peter M.

2018-01-01

Dynamic and static body postures are a defining characteristic of mind-body practices such as Tai Chi and Qigong (TCQ). A growing body of evidence supports the hypothesis that TCQ may be beneficial for psychological health, including management and prevention of depression and anxiety. Although a variety of causal factors have been identified as potential mediators of such health benefits, physical posture, despite its visible prominence, has been largely overlooked. We hypothesize that body posture while standing and/or moving may be a key therapeutic element mediating the influence of TCQ on psychological health. In the present paper, we summarize existing experimental and observational evidence that suggests a bi-directional relationship between body posture and mental states. Drawing from embodied cognitive science, we provide a theoretical framework for further investigation into this interrelationship. We discuss the challenges involved in such an investigation and propose suggestions for future studies. Despite theoretical and practical challenges, we propose that the role of posture in mind-body exercises such as TCQ should be considered in future research. PMID:29765313

Can Tai Chi and Qigong Postures Shape Our Mood? Toward an Embodied Cognition Framework for Mind-Body Research.

PubMed

Osypiuk, Kamila; Thompson, Evan; Wayne, Peter M

2018-01-01

Dynamic and static body postures are a defining characteristic of mind-body practices such as Tai Chi and Qigong (TCQ). A growing body of evidence supports the hypothesis that TCQ may be beneficial for psychological health, including management and prevention of depression and anxiety. Although a variety of causal factors have been identified as potential mediators of such health benefits, physical posture, despite its visible prominence, has been largely overlooked. We hypothesize that body posture while standing and/or moving may be a key therapeutic element mediating the influence of TCQ on psychological health. In the present paper, we summarize existing experimental and observational evidence that suggests a bi-directional relationship between body posture and mental states. Drawing from embodied cognitive science, we provide a theoretical framework for further investigation into this interrelationship. We discuss the challenges involved in such an investigation and propose suggestions for future studies. Despite theoretical and practical challenges, we propose that the role of posture in mind-body exercises such as TCQ should be considered in future research.

The personification of animals: coding of human and nonhuman body parts based on posture and function.

PubMed

Welsh, Timothy N; McDougall, Laura; Paulson, Stephanie

2014-09-01

The purpose of the present research was to determine how humans represent the bodies and limbs of nonhuman mammals based on anatomical and functional properties. To this end, participants completed a series of body-part compatibility tasks in which they responded with a thumb or foot response to the color of a stimulus (red or blue, respectively) presented on different limbs of several animals. Across the studies, this compatibility task was conducted with images of human and nonhuman animals (bears, cows, and monkeys) in bipedal or quadrupedal postures. The results revealed that the coding of the limbs of nonhuman animals is strongly influenced by the posture of the body, but not the functional capacity of the limb. Specifically, body-part compatibility effects were present for both human and nonhuman animals when the figures were in a bipedal posture, but were not present when the animals were in a quadrupedal stance (Experiments 1a-c). Experiments 2a and 2b revealed that the posture-based body-part compatibility effects were not simply a vertical spatial compatibility effect or due to a mismatch between the posture of the body in the image and the participant. These data indicate that nonhuman animals in a bipedal posture are coded with respect to the "human" body representation, whereas nonhuman animals in a quadrupedal posture are not mapped to the human body representation. Overall, these studies provide new insight into the processes through which humans understand, mimic, and learn from the actions of nonhuman animals. Copyright © 2014 Elsevier B.V. All rights reserved.

The relationship between energy expenditure and speed during pedestrian locomotion in birds: a morphological basis for the elevated y-intercept?

PubMed

Halsey, Lewis G

2013-06-01

The slope of the typically linear relationship between metabolic rate and walking speed represents the net cost of transport (NCOT). The extrapolated y-intercept is often greater than resting metabolic rate, thus representing a fixed cost associated with pedestrian transport including body maintenance costs. The full cause of the elevated y-intercept remains elusive and it could simply represent experimental stresses. The present literature-based study compares the mass-independent energetic cost of pedestrian locomotion in birds (excluding those with an upright posture, i.e. penguins), represented by the y-intercept, to a known predictor of cost of transport, hip height. Both phylogenetically informed and non-phylogenetically informed analyses were undertaken to determine if patterns of association between hip height, body mass, and the y-intercept are robust with respect to the method of analysis. Body mass and hip height were significant predictors of the y-intercept in the best phylogenetically-informed and non-phylogenetically informed models. Thus there is evidence that, in birds at least, the elevated y-intercept is a legitimate component of locomotion energy expenditure. Hip height is probably a good proxy of effective limb length and thus perhaps birds with greater hip heights have lower y-intercepts because their longer legs more efficiently accommodate body motion and/or because their limbs are more aligned with the ground reaction forces. Copyright © 2013 Elsevier Inc. All rights reserved.

An analytic model of the in-line and cross-axis apparent mass of the seated human body exposed to vertical vibration with and without a backrest

NASA Astrophysics Data System (ADS)

Zheng, Guangtai; Qiu, Yi; Griffin, Michael J.

2011-12-01

During vertical excitation of the seated human body there are vertical and fore-and-aft forces at the seat that are influenced by contact with a backrest, so it is desirable to take into account the effect of a backrest when developing models of the seated human body. Initially, a seven degree-of-freedom multi-body dynamic model was developed for the human body sitting with an upright posture unsupported by a backrest and exposed to vertical vibration. The model was optimized to fit the vertical apparent mass and the fore-and-aft cross-axis apparent mass measured on a seat. The model was then extended by the addition of vertical and fore-and-aft reaction forces to the upper lumbar spine to model the interaction between the human body and a backrest. By minimizing the least square error between experimental data and the analytical solution of the apparent masses on the seat and at the back, the human body model was able to represent both the vertical apparent mass and the fore-and-aft cross-axis apparent mass on the seat and at the back. Parameter sensitivity studies showed that the vertical apparent mass and the fore-and-aft cross-axis apparent mass on the seat and the backrest were all highly sensitive to the axial stiffness of the tissue beneath the pelvis. Pitch motion of the upper-body contributed to the vertical apparent mass and the fore-and-aft cross-axis apparent mass on the seat. The apparent mass at the back was more sensitive to the stiffness and damping of the lower back than the properties of the upper back.

Postural disorders and spatial neglect in stroke patients: a strong association.

PubMed

Pérennou, Dominic

2006-01-01

In this paper we analyse the arguments for a strong association between spatial neglect and postural disorders and attempt to better understand the mechanisms which underlie that. We first provide a general overview of the available tools for a rational assessment of postural control in a clinical context. We then analyse the arguments in favour of a close relationship, although not necessarily causal, between spatial neglect and: 1) body orientation with respect to gravity (including verticality perception i.e. the visual vertical, the haptic vertical, and the postural vertical); 2) body stabilisation with respect to the base of support; 3) posturographic features of stroke patients; 4) and finally their postural disability in daily life. This second part of the paper is based both on the literature review and on results of our current research. Neglect patients show a dramatic postural disability, due both to problems in body orientation with respect to gravity and to problems in body stabilisation. It might be that these problems are partly caused by a neglect phenomenon bearing on graviceptive (somaesthetic > vestibular) and visual information serving postural control. This could correspond to a kind of postural neglect involving both the bodily and nonbodily domains of spatial neglect. The existence of distorsion(s) in the body scheme are also probably involved, especially to explain the weight-bearing asymmetry in standing, and probably an impaired multisegmental postural coordination leading to an impaired body stabilisation. The present paper explains why neglect patients show longer/worse recovery of postural-walking autonomy than other stroke patients.

Characteristics of balance control in older persons who fall with injury--a prospective study.

PubMed

Kurz, Ilan; Oddsson, Lars; Melzer, Itshak

2013-08-01

Older adults who have recently fallen demonstrate increased postural sway compared with non-fallers. However, the differences in postural control between older adults who were seriously injured (SI) as a result of a fall, compared with those who fell but were not injured (NSI) and non-fallers (NFs), has not been investigated. The objective of the present study was to investigate the underlying postural control mechanisms related to injuries resulting from a fall. Both traditional postural sway measures of foot center-of-pressure (CoP) displacements and fractal measures, the Stabilogram-Diffusion Analysis (SDA), were used to characterize the postural control. One hundred older adults aged 65-91years were tested during narrow base upright stance in eyes closed condition; falls were monitored over a 1-year period. Forty-nine older adults fell during the 1-year follow-up, 13 were seriously injured as a result of a fall (SI), 36 were not injured (NSI), and 49 were non-fallers (NFs); two passed away. The SDA showed significantly higher short-term diffusion coefficients and critical displacements in SI in the anterior-posterior direction compared with both NSI and NF. However, in the medio-lateral direction there were no statistically significant differences between groups. For the traditional measures of sway, the average anterior-posterior CoP range was also larger in SI individuals. This work suggests that older fallers with a deterioration of anterior-posterior postural control may be at higher risk of serious injury following fall events. Copyright © 2013 Elsevier Ltd. All rights reserved.

Biomechanical effects of sitting with adjustable ischial and lumbar support on occupational low back pain: evaluation of sitting load and back muscle activity

PubMed Central

Makhsous, Mohsen; Lin, Fang; Bankard, James; Hendrix, Ronald W; Hepler, Matthew; Press, Joel

2009-01-01

Background Compared to standing posture, sitting decreases lumbar lordosis, increases low back muscle activity, disc pressure, and pressure on the ischium, which are associated with occupational LBP. A sitting device that reduces spinal load and low back muscle activities may help increase sitting comfort and reduce LBP risk. The objective of this study is to investigate the biomechanical effect of sitting with a reduced ischial support and an enhanced lumbar support (Off-Loading) on load, interface pressure and muscle activities. Methods A laboratory test in low back pain (LBP) and asymptomatic subjects was designed to test the biomechanical effect of using the Off-Loading sitting posture. The load and interface pressure on seat and the backrest, and back muscle activities associated with usual and this Off-Loading posture were recorded and compared between the two postures. Results Compared with Normal (sitting upright with full support of the seat and flat backrest) posture, sitting in Off-Loading posture significantly shifted the center of the force and the peak pressure on the seat anteriorly towards the thighs. It also significantly decreased the contact area on the seat and increased that on the backrest. It decreased the lumbar muscle activities significantly. These effects are similar in individuals with and without LBP. Conclusion Sitting with reduced ischial support and enhanced lumbar support resulted in reduced sitting load on the lumbar spine and reduced the lumbar muscular activity, which may potentially reduce sitting-related LBP. PMID:19193245

Postural stability and the influence of concurrent muscle activation--Beneficial effects of jaw and fist clenching.

PubMed

Ringhof, Steffen; Leibold, Timo; Hellmann, Daniel; Stein, Thorsten

2015-10-01

Recent studies reported on the potential benefits of submaximum clenching of the jaw on human postural control in upright unperturbed stance. However, it remained unclear whether these effects might also be observed among active controls. The purpose of the present study, therefore, was to comparatively examine the influence of concurrent muscle activation in terms of submaximum clenching of the jaw and submaximum clenching of the fists on postural stability. Posturographic analyses were conducted with 17 healthy young adults on firm and foam surfaces while either clenching the jaw (JAW) or clenching the fists (FIST), whereas habitual standing served as the control condition (CON). Both submaximum tasks were performed at 25% maximum voluntary contraction, assessed, and visualized in real time by means of electromyography. Statistical analyses revealed that center of pressure (COP) displacements were significantly reduced during JAW and FIST, but with no differences between both concurrent clenching activities. Further, a significant increase in COP displacements was observed for the foam as compared to the firm condition. The results showed that concurrent muscle activation significantly improved postural stability compared with habitual standing, and thus emphasize the beneficial effects of jaw and fist clenching for static postural control. It is suggested that concurrent activities contribute to the facilitation of human motor excitability, finally increasing the neural drive to the distal muscles. Future studies should evaluate whether elderly or patients with compromised postural control might benefit from these physiological responses, e.g., in the form of a reduced risk of falling. Copyright © 2015 Elsevier B.V. All rights reserved.

The Relationship Between the Stomatognathic System and Body Posture

PubMed Central

Cuccia, Antonino; Caradonna, Carola

2009-01-01

In recent years, many researchers have investigated the various factors that can influence body posture: mood states, anxiety, head and neck positions, oral functions (respiration, swallowing), oculomotor and visual systems, and the inner ear. Recent studies indicate a role for trigeminal afferents on body posture, but this has not yet been demonstrated conclusively. The present study aims to review the papers that have shown a relationship between the stomatognathic system and body posture. These studies suggest that tension in the stomatognathic system can contribute to impaired neural control of posture. Numerous anatomical connections between the stomatognathic system’s proprioceptive inputs and nervous structures are implicated in posture (cerebellum, vestibular and oculomotor nuclei, superior colliculus). If the proprioceptive information of the stomatognathic system is inaccurate, then head control and body position may be affected. In addition, the present review discusses the role the myofascial system plays in posture. If confirmed by further research, these considerations can improve our understanding and treatment of muscular-skeletal disorders that are associated with temporomandibular joint disorders, occlusal changes, and tooth loss. PMID:19142553

Mechanisms of postspaceflight orthostatic hypotension: low alpha1-adrenergic receptor responses before flight and central autonomic dysregulation postflight

NASA Technical Reports Server (NTRS)

Meck, Janice V.; Waters, Wendy W.; Ziegler, Michael G.; deBlock, Heidi F.; Mills, Paul J.; Robertson, David; Huang, Paul L.

2004-01-01

Although all astronauts experience symptoms of orthostatic intolerance after short-duration spaceflight, only approximately 20% actually experience presyncope during upright posture on landing day. The presyncopal group is characterized by low vascular resistance before and after flight and low norepinephrine release during orthostatic stress on landing day. Our purpose was to determine the mechanisms of the differences between presyncopal and nonpresyncopal groups. We studied 23 astronauts 10 days before launch, on landing day, and 3 days after landing. We measured pressor responses to phenylephrine injections; norepinephrine release with tyramine injections; plasma volumes; resting plasma levels of chromogranin A (a marker of sympathetic nerve terminal release), endothelin, dihydroxyphenylglycol (DHPG, an intracellular metabolite of norepinephrine); and lymphocyte beta(2)-adrenergic receptors. We then measured hemodynamic and neurohumoral responses to upright tilt. Astronauts were separated into two groups according to their ability to complete 10 min of upright tilt on landing day. Compared with astronauts who were not presyncopal on landing day, presyncopal astronauts had 1). significantly smaller pressor responses to phenylephrine both before and after flight; 2). significantly smaller baseline norepinephrine, but significantly greater DHPG levels, on landing day; 3). significantly greater norepinephrine release with tyramine on landing day; and 4). significantly smaller norepinephrine release, but significantly greater epinephrine and arginine vasopressin release, with upright tilt on landing day. These data suggest that the etiology of orthostatic hypotension and presyncope after spaceflight includes low alpha(1)-adrenergic receptor responsiveness before flight and a remodeling of the central nervous system during spaceflight such that sympathetic responses to baroreceptor input become impaired.

Mechanisms of postspaceflight orthostatic hypotension: low alpha1-adrenergic receptor responses before flight and central autonomic dysregulation postflight.

PubMed

Meck, Janice V; Waters, Wendy W; Ziegler, Michael G; deBlock, Heidi F; Mills, Paul J; Robertson, David; Huang, Paul L

2004-04-01

Although all astronauts experience symptoms of orthostatic intolerance after short-duration spaceflight, only approximately 20% actually experience presyncope during upright posture on landing day. The presyncopal group is characterized by low vascular resistance before and after flight and low norepinephrine release during orthostatic stress on landing day. Our purpose was to determine the mechanisms of the differences between presyncopal and nonpresyncopal groups. We studied 23 astronauts 10 days before launch, on landing day, and 3 days after landing. We measured pressor responses to phenylephrine injections; norepinephrine release with tyramine injections; plasma volumes; resting plasma levels of chromogranin A (a marker of sympathetic nerve terminal release), endothelin, dihydroxyphenylglycol (DHPG, an intracellular metabolite of norepinephrine); and lymphocyte beta(2)-adrenergic receptors. We then measured hemodynamic and neurohumoral responses to upright tilt. Astronauts were separated into two groups according to their ability to complete 10 min of upright tilt on landing day. Compared with astronauts who were not presyncopal on landing day, presyncopal astronauts had 1). significantly smaller pressor responses to phenylephrine both before and after flight; 2). significantly smaller baseline norepinephrine, but significantly greater DHPG levels, on landing day; 3). significantly greater norepinephrine release with tyramine on landing day; and 4). significantly smaller norepinephrine release, but significantly greater epinephrine and arginine vasopressin release, with upright tilt on landing day. These data suggest that the etiology of orthostatic hypotension and presyncope after spaceflight includes low alpha(1)-adrenergic receptor responsiveness before flight and a remodeling of the central nervous system during spaceflight such that sympathetic responses to baroreceptor input become impaired.

A method to quantify the "cone of economy".

PubMed

Haddas, Ram; Lieberman, Isador H

2018-05-01

A non-randomized, prospective, concurrent control cohort study. The purpose of this study is to develop and evaluate a method to quantify the dimensions of the cone of economy (COE) and the energy expenditure associated with maintaining a balanced posture within the COE, scoliosis patients and compare them to matched non-scoliotic controls in a group of adult degenerative. Balance is defined as the ability of the human body to maintain its center of mass (COM) within the base of support with minimal postural sway. The cone of economy refers to the stable region of upright standing posture. The underlying assumption is that deviating outside one's individual cone challenges the balance mechanisms. Adult degenerative scoliosis (ADS) patients exhibit a variety of postural changes within their COE, involving the spine, pelvis and lower extremities, in their effort to compensate for the altered posture. Ten ADS patients and ten non-scoliotic volunteers performed a series of functional balance tests. The dimensions of the COE and the energy expenditure related to maintaining balance within the COE were measured using a human motion video capture system and dynamic surface electromyography. ADS patients presented more COM sway in the sagittal (ADS: 1.59 cm vs. H: 0.61 cm; p = 0.049) and coronal (ADS: 2.84 cm vs. H: 1.72 cm; p = 0.046) directions in comparison to the non-scoliotic control. ADS patients presented with more COM (ADS: 33.30 cm vs. H: 19.13 cm; p = 0.039) and head (ADS: 31.06 cm vs. H: 19.13 cm; p = 0.013) displacements in comparison to the non-scoliotic controls. Scoliosis patients expended more muscle activity to maintain static standing, as manifest by increased muscle activity in their erector spinae (ADS: 37.16 mV vs. H: 20.31 mV; p = 0.050), and gluteus maximus (ADS: 33.12 mV vs. H: 12.09 mV; p = 0.001) muscles. We were able to develop and evaluate a method that quantifies the COE boundaries, COM displacement, and amount of sway within the COE along with the energy expenditure for a specific patient. This method of COE measurement will enable spine care practitioners to objectively evaluate their patients in an effort to determine the most appropriate treatment options, and in objectively documenting the effectiveness of their intervention.

Supine Lower Body Negative Pressure Exercise Maintains Upright Exercise Capacity in Male Twins during 30 Days of Bed Rest

NASA Technical Reports Server (NTRS)

Lee, Stuart M. C.; Schneider, Suzanne M.; Boda, Wanda L.; Watenpaugh, Donald E.; Macias, Brandon R.; Meyer, R. Scott; Hargens, Alan R.

2006-01-01

Exercise capacity is reduced following both short and long duration exposures to microgravity. We have shown previously that supine lower body negative pressure with exercise (LBNP(sub ex) maintains upright exercise capacity in men after 5d and 15d bed rest, as a simulation of microgravity. We hypothesized that LBNP(sub ex) would protect upright exercise capacity (VO2pk) and sprint performance in eight sets of identical male twins during a 30-d bed rest. Twins within each set were randomly assigned to either a control group (CON) who performed no exercise or to an exercise group (EX) who performed a 40-min interval (40-80% pre-BR VO2pk) LBNP(sub ex) (55+/-4 mmHg) exercise protocol, plus 5 min of resting LBNP, 6 d/wk. LBNP produced footward force equivalent to 1.0- 1.2 times body weight. Pre- and post-bed rest, subjects completed an upright graded exercise test to volitional fatigue and sprint test of 30.5 m. After bed rest, VO2pk was maintained in the EX subjects (-3+/-3%), but was significantly decreased in the CON subjects (-24+/-4%). Sprint time also was increased in the CON subjects (24+/-8%), but maintained in the EX group (8+/-2%). The performance of a supine, interval exercise protocol with LBNP maintains upright exercise capacity and sprint performance during 30 d of bed rest. This exercise countermeasure protocol may help prevent microgravity-induced deconditioning during long duration space flight.

Powerful postures versus powerful roles: which is the proximate correlate of thought and behavior?

PubMed

Huang, Li; Galinsky, Adam D; Gruenfeld, Deborah H; Guillory, Lucia E

2011-01-01

Three experiments explored whether hierarchical role and body posture have independent or interactive effects on the main outcomes associated with power: action in behavior and abstraction in thought. Although past research has found that being in a powerful role and adopting an expansive body posture can each enhance a sense of power, two experiments showed that when individuals were placed in high- or low-power roles while adopting an expansive or constricted posture, only posture affected the implicit activation of power, the taking of action, and abstraction. However, even though role had a smaller effect on the downstream consequences of power, it had a stronger effect than posture on self-reported sense of power. A final experiment found that posture also had a larger effect on action than recalling an experience of high or low power. We discuss body postures as one of the most proximate correlates of the manifestations of power.

Postural Responses Following Space Flight and Ground Based Analogs

NASA Technical Reports Server (NTRS)

Kofman, Igor S.; Reschke, Millard F.; Cerisano, Jody M.; Fisher, Elizabeth A.; Tomilovskaya, Elena V.; Kozlovskaya, Inessa B.; Bloomberg, Jacob B.

2013-01-01

With the transition from the Shuttle program to the International Space Station (ISS), the opportunity to fly sensorimotor experiments in a weightless environment has become increasingly more difficult to obtain. As a result, more investigations have turned to ground-based analogs as a way of evaluating an experiment's viability. The two primary analogs available to most investigators are 6deg head down bed rest (HDBR) and dry immersion (DI). For the time being, HDBR investigations have been associated with studies conducted in the United States while the Russians and several other European Union states have concentrated their efforts on using DI as the space flight analog of choice. While either model may be viable for cardiovascular, bone and other system changes, vestibular and sensorimotor investigators have retained serious reservations of either analog's potential to serve as a replacement for a true weightless environment. These reservations have merit, but it is worthwhile to consider that not all changes associated with sensorimotor function during space flight are the result of top-down modifications, but may also be due to the lack, or change, of appropriate support surfaces applying force to the bottom of the feet. To this end we have compared quiet stance postural responses between short duration Space Shuttle flights, long duration ISS flights and HDBR of varying duration. Using these three platforms, representing different modifications of support we investigated postural ataxia using a quiet stance model. Quiet stance was obtained by asking the subjects to stand upright on a force plate, eyes open, arms at the side of the body for three min. From the force plate we obtained average sway velocity in two axes as well as length of line (stabilogram). These parameters were then related to EMG activity recorded from the medial gastrocnemius and lateral tibialis. It is significant to note that postural ataxia measured as quiet stance shows analogous changes between HDBR and space flight. Primary differences across short duration, long duration space flight and HDBR are related to the length of exposure associated with both space flight and HDBR.

Body measurements and the variability of sitting postures at preschool age as preconditions for an optimal adjustment of chairs and tables.

PubMed

Voigt, Andrea; Greil, Holle

2009-03-01

Preschool age is a biological stage of intensive longitudinal growth with high plasticity of the growing body and of body postures. It is the period where children learn to persist in a sitting posture for a longer time and to use furniture like chairs or other body supporting systems. The growing body shows a special sensitivity for the manifestation of inappropriate postures. In this study the development of body measurements and sitting behaviour of preschool age children is investigated as a precondition for an optimal adjustment of seats and desks to the growing body. Accordingly to the instructions of Knussmann (1988) and Jiirgens (1988) 6 body measurements were taken from 122 German children aged 3 to 7 years from Potsdam, Province Brandenburg. Additionally, every child was videotaped for 10 minutes while crayoning in a sitting position of its own choice using a chair and a desk. To analyse the tapes, the software Noldus Observer was used and examined, picture by picture, to define the different types of sitting postures as well as the duration of persistence in a posture and the number of changes of postures. The used chairs and desks were also measured. Furthermore, the data of the furniture guideline DIN ISO 5970 (DIN, 1981), which regulates the dimensions of furniture for sitting in educational institutions, were compared with the results of the body measurements and with the dimensions of the furniture used by the children.

The effect of body postures on the distribution of air gap thickness and contact area.

PubMed

Mert, Emel; Psikuta, Agnes; Bueno, Marie-Ange; Rossi, René M

2017-02-01

The heat and mass transfer in clothing is predominantly dependent on the thickness of air layer and the magnitude of contact area between the body and the garment. The air gap thickness and magnitude of the contact area can be affected by the posture of the human body. Therefore, in this study, the distribution of the air gap and the contact area were investigated for different body postures of a flexible manikin. In addition, the effect of the garment fit (regular and loose) and style (t-shirts, sweatpants, jacket and trousers) were analysed for the interaction between the body postures and the garment properties. A flexible manikin was scanned using a three-dimensional (3D) body scanning technique, and the scans were post-processed in dedicated software. The body posture had a strong effect on the air gap thickness and the contact area for regions where the garment had a certain distance from the body. Furthermore, a mathematical model was proposed to estimate the possible heat transfer coefficient for the observed air layers and their change with posture. The outcome of this study can be used to improve the design of the protective and functional garments and predict their effect on the human body.

Postural headache in marfan syndrome associated with spinal cysts and liquor hypotension.

PubMed

Voermans, N C; Dijk, K G J van; Bos, M M; Geus-Oei, L-F de; Verrips, A; Lindert, E J van

2009-08-01

We here report a 13-year-old Marfan patient who suffered from severe, medication-resistant, intermittent headache, which was provoked when getting into an upright position and immediately relieved by lying down or after intravenous rehydration. The postural benefit and the sudden relief after intravenous hydration suggested (intermittent) intracranial hypotension, although a normal opening pressure on lumbar punction was observed and no cerebrospinal fluid (CSF) leakage was identified. Imaging studies revealed severe dural ectasia at lumbosacral level, and two intradural cysts and two extradural presacral cysts were detected. Most likely, altered hydrodynamics in intra- and extracranial spinal meningeal cysts caused intermittent CSF hypotension above these cysts, resulting in intermittent intracranial hypotension. Surgical marsupialisation of the intradural cysts proved to be effective. This resulted in a significant reduction of the headache during the clinical follow-up of eight years. Georg Thieme Verlag KG Stuttgart New York.

Rapid adaptation of multisensory integration in vestibular pathways

PubMed Central

Carriot, Jerome; Jamali, Mohsen; Cullen, Kathleen E.

2015-01-01

Sensing gravity is vital for our perception of spatial orientation, the control of upright posture, and generation of our everyday activities. When an astronaut transitions to microgravity or returns to earth, the vestibular input arising from self-motion will not match the brain's expectation. Our recent neurophysiological studies have provided insight into how the nervous system rapidly reorganizes when vestibular input becomes unreliable by both (1) updating its internal model of the sensory consequences of motion and (2) up-weighting more reliable extra-vestibular information. These neural strategies, in turn, are linked to improvements in sensorimotor performance (e.g., gaze and postural stability, locomotion, orienting) and perception characterized by similar time courses. We suggest that furthering our understanding of the neural mechanisms that underlie sensorimotor adaptation will have important implications for optimizing training programs for astronauts before and after space exploration missions and for the design of goal-oriented rehabilitation for patients. PMID:25932009

Powered AFO for Achilles tendon rupture.

PubMed

Yoshizawa, Nobuyuki

2008-01-01

This paper proposes a powered ankle foot orthosis (AFO) for the treatment of a ruptured Achilles tendon. Usually, conservative orthosis treatment requires about two months, and a motionless ankle degrades activities of daily living (ADL). It is difficult to go to school or work on foot, and a pair of crutches is needed to go up and down stairs. In order to improve the ADL, an electric powered AFO has been designed to improve the ability to walk with a fixed ankle joint. The sole of the proposed AFO is equipped with an electric actuator. The prototype actuator consists of Nd magnets and electromagnets and is lightweight and battery driven. The actuator can switch the upright posture and the stepped forward posture of the patient. In an experiment, the use of this electric AFO made it possible to walk and to ascend and descend stairs with a fixed ankle joint.

Nonplantigrade Foot Posture: A Constraint on Dinosaur Body Size

PubMed Central

Kubo, Tai; Kubo, Mugino O.

2016-01-01

Dinosaurs had functionally digitigrade or sub-unguligrade foot postures. With their immediate ancestors, dinosaurs were the only terrestrial nonplantigrades during the Mesozoic. Extant terrestrial mammals have different optimal body sizes according to their foot posture (plantigrade, digitigrade, and unguligrade), yet the relationship of nonplantigrade foot posture with dinosaur body size has never been investigated, even though the body size of dinosaurs has been studied intensively. According to a large dataset presented in this study, the body sizes of all nonplantigrades (including nonvolant dinosaurs, nonvolant terrestrial birds, extant mammals, and extinct Nearctic mammals) are above 500 g, except for macroscelid mammals (i.e., elephant shrew), a few alvarezsauroid dinosaurs, and nondinosaur ornithodirans (i.e., the immediate ancestors of dinosaurs). When nonplantigrade tetrapods evolved from plantigrade ancestors, lineages with nonplantigrade foot posture exhibited a steady increase in body size following Cope’s rule. In contrast, contemporaneous plantigrade lineages exhibited no trend in body size evolution and were largely constrained to small body sizes. This evolutionary pattern of body size specific to foot posture occurred repeatedly during both the Mesozoic and the Cenozoic eras. Although disturbed by the end-Cretaceous extinction, species of mid to large body size have predominantly been nonplantigrade animals from the Jurassic until the present; conversely, species with small body size have been exclusively composed of plantigrades in the nonvolant terrestrial tetrapod fauna. PMID:26790003

Nonplantigrade Foot Posture: A Constraint on Dinosaur Body Size.

PubMed

Kubo, Tai; Kubo, Mugino O

2016-01-01

Dinosaurs had functionally digitigrade or sub-unguligrade foot postures. With their immediate ancestors, dinosaurs were the only terrestrial nonplantigrades during the Mesozoic. Extant terrestrial mammals have different optimal body sizes according to their foot posture (plantigrade, digitigrade, and unguligrade), yet the relationship of nonplantigrade foot posture with dinosaur body size has never been investigated, even though the body size of dinosaurs has been studied intensively. According to a large dataset presented in this study, the body sizes of all nonplantigrades (including nonvolant dinosaurs, nonvolant terrestrial birds, extant mammals, and extinct Nearctic mammals) are above 500 g, except for macroscelid mammals (i.e., elephant shrew), a few alvarezsauroid dinosaurs, and nondinosaur ornithodirans (i.e., the immediate ancestors of dinosaurs). When nonplantigrade tetrapods evolved from plantigrade ancestors, lineages with nonplantigrade foot posture exhibited a steady increase in body size following Cope's rule. In contrast, contemporaneous plantigrade lineages exhibited no trend in body size evolution and were largely constrained to small body sizes. This evolutionary pattern of body size specific to foot posture occurred repeatedly during both the Mesozoic and the Cenozoic eras. Although disturbed by the end-Cretaceous extinction, species of mid to large body size have predominantly been nonplantigrade animals from the Jurassic until the present; conversely, species with small body size have been exclusively composed of plantigrades in the nonvolant terrestrial tetrapod fauna.

Undisturbed upright stance control in the elderly: Part 1. Age-related changes in undisturbed upright stance control.

PubMed

Berger, L; Chuzel, M; Buisson, G; Rougier, P

2005-09-01

The authors investigated age-related changes in postural control in 33 healthy young adults (18-31 years), 29 seniors (62-75 years), and 22 elderly people (75-96 years). A force platform recorded the results. The horizontal motions of the center of gravity (CGh) and their difference in the plane of support CP - CGv were deduced from the complex center of pressure (CP) trajectories. With fractional Brownian modeling, one can establish that the aging process seems to induce a transition phase in which seniors take more time to initiate the corrective process in the mediolateral (ML) axis than do younger people. The elderly develop a new strategy characterized by the mobilization of higher neuromuscular energy to maintain equilibrium. In the ML axis, the larger displacements could be caused mainly by a hip strategy that could facilitate step initiation. In the anteroposterior (AP) axis, seniors and elderly individuals maintain a relative ability to stabilize their CG into the base of support compared with younger people.

Practice of Contemporary Dance Promotes Stochastic Postural Control in Aging

PubMed Central

Ferrufino, Lena; Bril, Blandine; Dietrich, Gilles; Nonaka, Tetsushi; Coubard, Olivier A.

2011-01-01

As society ages and the frequency of falls increases, counteracting gait and posture decline is a challenging issue for countries of the developed world. Previous studies have shown that exercise and hazard management help to improve balance and/or decrease the risks for falling in normal aging. Motor activity based on motor-skill learning, particularly dance, can also benefit balance and decreases falls with age. Recent studies have suggested that older dancers have better balance, posture, or gait than non-dancers. Additionally, clinical or laboratory measures have shown improvements in some aspects of balance after dance interventions in elderly trainees. This study examined the impact of contemporary dance (CD) and of fall prevention (FP) programs on postural control of older adults. Posturography of quiet upright stance was performed in 41 participants aged 59–86 years before and after 4.4-month training in either CD or FP once a week. Though classical statistic scores failed to show any effect, dynamic analyses of the center-of-pressure displacements revealed significant changes after training. Specifically, practice of CD enhanced the critical time interval in diffusion analysis, and reduced recurrence and mathematical stability in recurrence quantification analysis, whereas practice of FP induced or tended to induce the reverse patterns. Such effects were obtained only in the eyes open condition. We suggest that CD training based on motor improvisation favored stochastic posture inducing plasticity in motor control, while FP training based on more stereotyped behaviors did not. PMID:22232582

Platypnea-orthodeoxia due to fat embolism

PubMed Central

Gourgiotis, Stavros; Aloizos, Stavros; Gakis, Christos; Salemis, Nikolaos S.

2011-01-01

Platypnea-orthodeoxia is an uncommon syndrome that is characterized by dyspnea relieved by recumbency and deoxygenation following a change from a recumbent to an upright posture. We herein describe a case of platypnea-orthodeoxia in a 75-year-old man after a surgical restoration of a bitrochanteric fracture of his right femur. However, in this extremely rare case, none of the current known anatomical or functional conditions which can cause platypnea-orthodeoxia had been diagnosed. We strongly believe that this syndrome could be also the result of fat embolism. PMID:22096710

[Analysis of potential for research on giving birth in an upright position in German hospitals].

PubMed

Mattern, Elke; Voigt-Radloff, Sebastian; Ayerle, Gertrud M

2014-01-01

In German hospitals, three quarters of all low-risk pregnant women give birth in the supine position, despite the fact that German, British and WHO guidelines do not recommend a supine birthing position which is associated with a higher risk to the health of both mother and fetus. Based on 22 RCTs with 7,280 participants, a systematic Cochrane review (Gupta et al., 2012) revealed that an upright position - compared with a supine or lithotomy position - (1) has a positive impact on fetal heart rate patterns, (2) reduces the requirement for analgesic or anaesthetic medications in the second stage of labour, and (3) results in fewer episiotomies and (4) fewer instrumental deliveries. There is a lack of evidence regarding perceived maternal autonomy, self-efficacy and anxiety when giving birth. Furthermore, evidence on long-term effects is absent. Some studies indicate that the choice of an upright birthing position might be boosted by a supporting physical and social environment and by specially trained midwives. There is a need for a feasibility study and a subsequent cluster RCT in the German healthcare context in order to investigate the effects of the upright posture for birthing on perceived maternal autonomy, self-efficacy and anxiety, on the reduction of perinatal complications and on long-term complaints. The complex experimental intervention consists of (1) evidence-based and user-friendly information for women and their partners, (2) facilitating the choice for an upright labour position by special training for midwives and (3) providing a supportive physical and social environment. Within the first study phase, the exploration of feasibility in terms of access to the target group and acceptance of the intervention by pregnant women, their partners and midwives is recommended. Thereby, the implementation of guidelines for upright labour and birth, the documentation and collection of outcome and cost data could be evaluated. Non-German instruments for measuring benefits, harms and long-term effects could be adapted to and validated for the German context. Copyright © 2014. Published by Elsevier GmbH.

Human muscle sympathetic neural and haemodynamic responses to tilt following spaceflight

NASA Technical Reports Server (NTRS)

Levine, Benjamin D.; Pawelczyk, James A.; Ertl, Andrew C.; Cox, James F.; Zuckerman, Julie H.; Diedrich, Andre; Biaggioni, Italo; Ray, Chester A.; Smith, Michael L.; Iwase, Satoshi;

Human muscle sympathetic neural and haemodynamic responses to tilt following spaceflight

PubMed Central

Levine, Benjamin D; Pawelczyk, James A; Ertl, Andrew C; Cox, James F; Zuckerman, Julie H; Diedrich, André; Biaggioni, Italo; Ray, Chester A; Smith, Michael L; Iwase, Satoshi; Saito, Mitsuru; Sugiyama, Yoshiki; Mano, Tadaaki; Zhang, Rong; Iwasaki, Kenichi; Lane, Lynda D; Buckey, Jay C; Cooke, William H; Baisch, Friedhelm J; Robertson, David; Eckberg, Dwain L; Blomqvist, C Gunnar

2002-01-01

Orthostatic intolerance is common when astronauts return to Earth: after brief spaceflight, up to two-thirds are unable to remain standing for 10 min. Previous research suggests that susceptible individuals are unable to increase their systemic vascular resistance and plasma noradrenaline concentrations above pre-flight upright levels. In this study, we tested the hypothesis that adaptation to the microgravity of space impairs sympathetic neural responses to upright posture on Earth. We studied six astronauts ∼72 and 23 days before and on landing day after the 16 day Neurolab space shuttle mission. We measured heart rate, arterial pressure and cardiac output, and calculated stroke volume and total peripheral resistance, during supine rest and 10 min of 60 deg upright tilt. Muscle sympathetic nerve activity was recorded in five subjects, as a direct measure of sympathetic nervous system responses. As in previous studies, mean (± s.e.m.) stroke volume was lower (46 ± 5 vs. 76 ± 3 ml, P = 0.017) and heart rate was higher (93 ± 1 vs. 74 ± 4 beats min−1, P = 0.002) during tilt after spaceflight than before spaceflight. Total peripheral resistance during tilt post flight was higher in some, but not all astronauts (1674 ± 256 vs. 1372 ± 62 dynes s cm−5, P = 0.32). No crew member exhibited orthostatic hypotension or presyncopal symptoms during the 10 min of postflight tilting. Muscle sympathetic nerve activity was higher post flight in all subjects, in supine (27 ± 4 vs. 17 ± 2 bursts min−1, P = 0.04) and tilted (46 ± 4 vs. 38 ± 3 bursts min−1, P = 0.01) positions. A strong (r2 = 0.91–1.00) linear correlation between left ventricular stroke volume and muscle sympathetic nerve activity suggested that sympathetic responses were appropriate for the haemodynamic challenge of upright tilt and were unaffected by spaceflight. We conclude that after 16 days of spaceflight, muscle sympathetic nerve responses to upright tilt are normal. PMID:11773340

[Self-evaluation of posture by elderly people with or without thoracic kyphosis].

PubMed

Gasparotto, Lívia Pimenta Renó; Reis, Camila Costa Ibiapina; Ramos, Luiz Roberto; Santos, José Francisco Quirino Dos

2012-03-01

This article lists the differences between self-perception of body posture among the elderly suffering from postural alterations or not, in order to ascertain whether self-evaluation of posture can lead to preventive measures. Eighteen cases from the elderly population participated in the EPIDOSO project at UNIFESP and were subjected to postural evaluation. Postures were photographed and copies given to the participants and their subsequent comments were analyzed by the qualitative method. The narratives were taped and cataloguedusingthe technique of theoretical axial and selective coding from the perspective of symbolic interactionism. A passive attitude was identified among the elderly in relation to postural alterations. There is a distortion of body image by those with postural deviation. Participants with adequate spinal alignment were more conscious about body posture and the importance of this being assimilated in the phases prior to aging. The adoption of postural self-care seems to occur in the earlier stages of aging and preventive measures should be implemented at this stage. Lack of concern about posture is linked to the concept of the elderly regarding the notion that aging is, in itself, the accumulation of inevitably simultaneous or successive dysfunctions.

Sad or Fearful? The Influence of Body Posture on Adults' and Children's Perception of Facial Displays of Emotion

ERIC Educational Resources Information Center

Mondloch, Catherine J.

2012-01-01

The current research investigated the influence of body posture on adults' and children's perception of facial displays of emotion. In each of two experiments, participants categorized facial expressions that were presented on a body posture that was congruent (e.g., a sad face on a body posing sadness) or incongruent (e.g., a sad face on a body…

Daily Supine LBNP Treadmill Exercise Maintains Upright Exercise Capacity During 14 Days of Bed Rest

NASA Technical Reports Server (NTRS)

Ertl, Andy C.; Watenpaugh, D. E.; Hargens, Alan R.; Fortney, S. M.; Lee, S. M. C.; Ballard, R. E.; William, J. M.

1996-01-01

Exposure to microgravity or bed rest reduces upright exercise capacity. Exercise modes, durations, and intensities which will effectively and efficiently counteract such deconditioning are presently unresolved. We that daily supine treadmill interval training with lower body negative pressure (LBNP) would prevent reduction in upright exercise capacity during 14 days of 6 deg. head-down bed rest (BR). Eight healthy male subjects underwent two 14 day BR protocols separated by 3 months. In a crossover design, subjects either remained at strict BR or performed 40 min of daily exercise consisting of supine walking and running at intensities varying from 40-80% of pre-BR upright peak oxygen uptake (VO2). LBNP during supine exercise was used to provide 1.0 to 1.2 times body weight of footward force. An incremental upright treadmill test to measure submaximal and peak exercise responses was given pre- and post-BR. In the non-exercise condition, peak VO2 and time to exhaustion were reduced 16 +/- 4% and 10 +/- 1% (p less than 0.05), respectively, from pre-BR. With LBNP exercise these variables were not significantly different (NS) from pre-BR. During submaximal treadmill speeds after BR, heart rate was higher (11 +/- 11 bpm, p less than 0.05) and respiratory exchange ratio was elevated (p less than 0.05) in the no exercise condition. Both were maintained at pre-BR levels in the LBNP exercise condition (NS from pre-BR). Since this supine treadmill interval training with addition of LBNP maintained upright exercise responses and capacity during BR, this countermeasure may also be effective during space flight.

One month of contemporary dance modulates fractal posture in aging

PubMed Central

Coubard, Olivier A.; Ferrufino, Lena; Nonaka, Tetsushi; Zelada, Oscar; Bril, Blandine; Dietrich, Gilles

2013-01-01

Understanding the human aging of postural control and how physical or motor activity improves balance and gait is challenging for both clinicians and researchers. Previous studies have evidenced that physical and sporting activity focusing on cardiovascular and strength conditioning help older adults develop their balance and gait and/or decrease their frequency of falls. Motor activity based on motor-skill learning has also been put forward as an alternative to develop balance and/or prevent falls in aging. Specifically dance has been advocated as a promising program to boost motor control. In this study, we examined the effects of contemporary dance (CD) on postural control of older adults. Upright stance posturography was performed in 38 participants aged 54–89 years before and after the intervention period, during which one half of the randomly assigned participants was trained to CD and the other half was not trained at all (no dance, ND). CD training lasted 4 weeks, 3 times a week. We performed classical statistic scores of postural signal and dynamic analyses, namely signal diffusion analysis (SDA), recurrence quantification analysis (RQA), and detrended fluctuation analysis (DFA). CD modulated postural control in older trainees, as revealed in the eyes closed condition by a decrease in fractal dimension and an increase in DFA alpha component in the mediolateral plane. The ND group showed an increase in length and mean velocity of postural signal, and the eyes open a decrease in RQA maximal diagonal line in the anteroposterior plane and an increase in DFA alpha component in the mediolateral plane. No change was found in SDA in either group. We suggest that such a massed practice of CD reduced the quantity of exchange between the subject and the environment by increasing their postural confidence. Since CD has low-physical but high-motor impact, we conclude that it may be recommended as a useful program to rehabilitate posture in aging. PMID:24611047

Modeling of Cardiovascular Response to Weightlessness

NASA Technical Reports Server (NTRS)

Sharp, M. Keith

1999-01-01

It was the hypothesis of this Project that the Simple lack of hydrostatic pressure in microgravity generates several purely physical reactions that underlie and may explain, in part, the cardiovascular response to weightlessness. For instance, hydrostatic pressure within the ventricles of the heart may improve cardiac performance by promoting expansion of ventricular volume during diastole. The lack of hydrostatic pressure in microgravity might, therefore, reduce diastolic filling and cardiac performance. The change in transmural pressure is possible due to the difference in hydrostatic pressure gradients between the blood inside the ventricle and the lung tissue surrounding the ventricle due to their different densities. On the other hand, hydrostatic pressure within the vasculature may reduce cardiac inlet pressures because of the typical location of the heart above the hydrostatic indifference level (the level at which pressure remains constant throughout changes in gravity). Additional physical responses of the body to changing gravitational conditions may influence cardiovascular performance. For instance, fluid shifts from the lower body to the thorax in microgravity may serve to increase central venous pressure (CVP) and boost cardiac output (CO). The concurrent release of gravitational force on the rib cage may tend to increase chest girth and decrease pedcardial pressure, augmenting ventricular filling. The lack of gravity on pulmonary tissue may allow an upward shifting of lung mass, causing a further decrease in pericardial pressure and increased CO. Additional effects include diuresis early in the flight, interstitial fluid shifts, gradual spinal extension and movement of abdominal mass, and redistribution of circulatory impedance because of venous distention in the upper body and the collapse of veins in the lower body. In this project, the cardiovascular responses to changes in intraventricular hydrostatic pressure, in intravascular hydrostatic pressure and, to a limited extent, in extravascular and pedcardial hydrostatic pressure were investigated. A complete hydraulic model of the cardiovascular system was built and flown aboard the NASA KC-135 and a computer model was developed and tested in simulated microgravity. Results obtained with these models have confirmed that a simple lack of hydrostatic pressure within an artificial ventricle causes a decrease in stroke volume. When combined with the acute increase in ventricular pressure associated with the elimination of hydrostatic pressure within the vasculature and the resultant cephalad fluid shift with the models in the upright position, however, stroke volume increased in the models. Imposition of a decreased pedcardial pressure in the computer model and in a simplified hydraulic model increased stroke volume. Physiologic regional fluid shifting was also demonstrated by the models. The unifying parameter characterizing of cardiac response was diastolic ventricular transmural pressure (DVDELTAP) The elimination of intraventricular hydrostatic pressure in O-G decreased DVDELTAP stroke volume, while the elimination of intravascular hydrostatic pressure increased DVDELTAP and stroke volume in the upright posture, but reduced DVDELTAP and stroke volume in the launch posture. The release of gravity on the chest wall and its associated influence on intrathoracic pressure, simulated by a drop in extraventricular pressure4, increased DVDELTAP ans stroke volume.

Prospective dynamic functional evaluation of gait and spinal balance following spinal fusion in adolescent idiopathic scoliosis.

PubMed

Lenke, L G; Engsberg, J R; Ross, S A; Reitenbach, A; Blanke, K; Bridwell, K H

2001-07-15

Prospective evaluation of gait and spinal-pelvic balance parameters in patients with adolescent idiopathic scoliosis undergoing a spinal fusion. To evaluate changes in gait and three-dimensional alignment and balance of the spine relative to the pelvis as a consequence of spinal fusion. Preoperative and postoperative spinal radiographs have been the major forms of outcome analysis of adolescent idiopathic scoliosis fusions. The use of optoelectronic analysis for posture and gait has gained acceptance recently. However, there is a paucity of data quantifying, comparing, and correlating structural and functional changes in patients undergoing scoliosis fusion surgery including upright posture and gait. Thirty patients with adolescent idiopathic scoliosis undergoing an instrumented spinal fusion were prospectively evaluated. Coronal and sagittal vertical alignment was evaluated on radiographs (CVA-R, SVA-R), during upright posture (CVA-P and SVA-P), and during gait (CVA-G, SVA-G). Transverse plane alignment was evaluated by the acromion-pelvis angle during gait. Gait speed was significantly decreased (P < 0.05) between preoperative (129 +/- 16 cm/sec) and 2-year postoperative (119 +/- 16 cm/sec) testing sessions. Decreasing gait speed was the result of significantly reduced cadence and decreased stride length. There were no significant differences for lower extremity kinematics over the entire gait cycle. Spinal-pelvic balance parameters showed significant improvement in mean CVA-R, CVA-G (P < 0.05), then unchanged CVA-P at 2 years postoperation. CVA-P was relatively unchanged while the mean CVA-G also showed significant improvement from preoperation (2.2 +/- 2.4 cm) to 2 years postoperation (1.3 +/- 1.3 cm)(P < 0.05). The mean SVA-R, SVA-P, and SVA-G were unchanged at 2 years postoperation (P > 0.05). The acromion-pelvis angle during gait at maximum shoulder rotation was statistically improved at 1 year (P = 0.002) and 2 years (P = 0.001) after surgery. Importantly, CVA-P correlated with CVA-G, and SVA-P correlated with SVA-G to the P < 0.05 level. Patients with adolescent idiopathic scoliosis undergoing spinal fusion show slightly decreased gait speed at 2 years postoperation without any change in lower extremity kinematics. Spinal-pelvic balance parameters are improved in the coronal plane and unchanged in the sagittal plane radiographically and during standing posture and gait. Transverse plane parameters also are improved at maximum shoulder rotation during gait.

Expand your body when you look at yourself: The role of the posture in a mirror exposure task

PubMed Central

Etchemendy, Ernestina; Cebolla, Ausiàs; Rodríguez, Víctor; Medrano, Carlos; Baños, Rosa María

2018-01-01

Mirror exposure (ME) is one of the main components of the treatment of patients with eating disorders symptomatology and it has shown its effectiveness in improving several outcomes (e.g., body dissatisfaction). However, the study as to what body posture should be adopted to maximize its effectiveness has been neglected. From embodied cognition and emotion theories, the adoption of an expansive (vs. contractive) body posture has been associated with positive changes in cognitive and emotional responses. The objective of this study was to analyze the effect of adopting an expansive (vs. contractive) posture before an ME task on body-related emotions and cognitions, as well as to analyze the possible moderator and mediator variables of these relationships. The sample was composed of 68 women (age: M = 21.74, SD = 3.12) with high scores on body dissatisfaction. Participants were randomly assigned to the expansive or contractive condition, where the openness of the arms/legs and the back position were manipulated. Posture was monitored by an electronic device and participants filled out several self-reported measures. ANCOVAs, moderation, mediation, and moderated mediated analyses were performed. Results showed that women in the expansive condition showed higher positive emotions after the ME. Moreover, exploratory analyses showed that adopting an expansive posture improved positive emotions, leading to improvements in negative emotions, body image satisfaction, and appraisal of the person’s own body. Psychological interventions should explore the value of holding an expansive posture before the ME in women with body dissatisfaction. PMID:29570729

Expand your body when you look at yourself: The role of the posture in a mirror exposure task.

PubMed

Miragall, Marta; Etchemendy, Ernestina; Cebolla, Ausiàs; Rodríguez, Víctor; Medrano, Carlos; Baños, Rosa María

2018-01-01

Mirror exposure (ME) is one of the main components of the treatment of patients with eating disorders symptomatology and it has shown its effectiveness in improving several outcomes (e.g., body dissatisfaction). However, the study as to what body posture should be adopted to maximize its effectiveness has been neglected. From embodied cognition and emotion theories, the adoption of an expansive (vs. contractive) body posture has been associated with positive changes in cognitive and emotional responses. The objective of this study was to analyze the effect of adopting an expansive (vs. contractive) posture before an ME task on body-related emotions and cognitions, as well as to analyze the possible moderator and mediator variables of these relationships. The sample was composed of 68 women (age: M = 21.74, SD = 3.12) with high scores on body dissatisfaction. Participants were randomly assigned to the expansive or contractive condition, where the openness of the arms/legs and the back position were manipulated. Posture was monitored by an electronic device and participants filled out several self-reported measures. ANCOVAs, moderation, mediation, and moderated mediated analyses were performed. Results showed that women in the expansive condition showed higher positive emotions after the ME. Moreover, exploratory analyses showed that adopting an expansive posture improved positive emotions, leading to improvements in negative emotions, body image satisfaction, and appraisal of the person's own body. Psychological interventions should explore the value of holding an expansive posture before the ME in women with body dissatisfaction.

Whole-body vibration and postural stress among operators of construction equipment: a literature review.

PubMed

Kittusamy, N Kumar; Buchholz, Bryan

2004-01-01

Operators of construction equipment perform various duties at work that expose them to a variety of risk factors that may lead to health problems. A few of the health hazards among operators of construction equipment are: (a) whole-body vibration, (b) awkward postural requirements (including static sitting), (c) dust, (d) noise, (e) temperature extremes, and (f) shift work. It has been suggested that operating engineers (OEs) are exposed to two important risk factors for the development of musculoskeletal disorders: whole-body vibration and non-neutral body postures. This review evaluates selected papers that have studied exposure to whole-body vibration and awkward posture among operators of mobile equipment. There have been only few studies that have specifically examined exposure of these risk factors among operators of construction equipment. Thus other studies from related industry and equipment were reviewed as applicable. In order to better understand whole-body vibration and postural stress among OEs, it is recommended that future studies are needed in evaluating these risk factors among OEs.

Understanding the pusher behavior of some stroke patients with spatial deficits: a pilot study.

PubMed

Pérennou, Dominic Alain; Amblard, Bernard; Laassel, El Mostafa; Benaim, Charles; Hérisson, Christian; Pélissier, Jacques

2002-04-01

To investigate whether pusher behavior (ie, a tendency among stroke patients with spatial deficits to actively push away from the nonparalyzed side and to resist any attempt to hold a more upright posture) affects only the trunk, for which gravitational feedback is given by somesthetic information, or the head as well, whose gravitational information is mainly given by the vestibular system (without vision). Description and measurement of clinical features. Rehabilitation center research laboratory. Eight healthy subjects age matched to 14 patients with left hemiplegia resulting from right-hemisphere stroke (3 pushers showing a severe spatial neglect, 11 without pusher behavior). All participants were asked to actively maintain an erect posture while sitting for 8 seconds on a rocking, laterally unstable platform. The task was performed with (in light) and without (in darkness) vision. The number of trials needed to succeed in the task was monitored. In successful trials, head, shoulders, thoracolumbar spine, and pelvis orientation in roll were measured by means of an automated, optical television image processor. Compared with other patients and healthy subjects, the 3 pushers missed many more trials and displayed a contralesional tilt of the pelvis but kept a correct head orientation. This tilt was especially pronounced without vision. Spatial neglect was a key factor, explaining 56% of patients' misorientation behavior with vision and 61% without vision. This pilot kinematic analysis shows that pusher behavior does not result from disrupted processing of vestibular information (eg, caused by a lesion involving the vestibular cortex); rather, it results from a high-order disruption in the processing of somesthetic information originating in the left hemibody, which could be graviceptive neglect (extinction). This disruption leads pushers to actively adjust their body posture to a subjective vertical biased to the side opposite the cerebral lesion. Copyright 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Alterations in Postural Control during the World's Most Challenging Mountain Ultra-Marathon

PubMed Central

Degache, Francis; Van Zaen, Jérôme; Oehen, Lukas; Guex, Kenny; Trabucchi, Pietro; Millet, Gégoire

2014-01-01

We investigated postural control (PC) effects of a mountain ultra-marathon (MUM): a 330-km trail run with 24000 m of positive and negative change in elevation. PC was assessed prior to (PRE), during (MID) and after (POST) the MUM in experienced ultra-marathon runners (n = 18; finish time = 126±16 h) and in a control group (n = 8) with a similar level of sleep deprivation. Subjects were instructed to stand upright on a posturographic platform over a period of 51.2 seconds using a double-leg stance under two test conditions: eyes open (EO) and eyes closed (EC). Traditional measures of postural stability (center of pressure trajectory analysis) and stabilogram-diffusion analysis (SDA) parameters were analysed. For the SDA, a significantly greater short-term effective diffusion was found at POST compared with PRE in the medio-lateral (ML; Dxs) and antero-posterior (AP) directions (Dys) in runners (p<0.05) The critical time interval (Ctx) in the ML direction was significantly higher at MID (p<0.001) and POST (p<0.05) than at PRE in runners. At MID (p<0.001) and POST (p<0.05), there was a significant difference between the two groups. The critical displacement (Cdx) in the ML was significantly higher at MID and at POST (p<0.001) compared with PRE for runners. A significant difference in Cdx was observed between groups in EO at MID (p<0.05) and POST (p<0.005) in the ML direction and in EC at POST in the ML and AP directions (p<0.05). Our findings revealed significant effects of fatigue on PC in runners, including, a significant increase in Ctx (critical time in ML plan) in EO and EC conditions. Thus, runners take longer to stabilise their body at POST than at MID. It is likely that the mountainous characteristics of MUM (unstable ground, primarily uphill/downhill running, and altitude) increase this fatigue, leading to difficulty in maintaining balance. PMID:24465417

Stereotypes and prejudice affect the recognition of emotional body postures.

PubMed

Bijlstra, Gijsbert; Holland, Rob W; Dotsch, Ron; Wigboldus, Daniel H J

2018-03-26

Most research on emotion recognition focuses on facial expressions. However, people communicate emotional information through bodily cues as well. Prior research on facial expressions has demonstrated that emotion recognition is modulated by top-down processes. Here, we tested whether this top-down modulation generalizes to the recognition of emotions from body postures. We report three studies demonstrating that stereotypes and prejudice about men and women may affect how fast people classify various emotional body postures. Our results suggest that gender cues activate gender associations, which affect the recognition of emotions from body postures in a top-down fashion. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Day/Night Variability in Blood Pressure: Influence of Posture and Physical Activity

PubMed Central

2013-01-01

BACKGROUND Blood pressure (BP) is highest during the day and lowest at night. Absence of this rhythm is a predictor of cardiovascular morbidity and mortality. Contributions of changes in posture and physical activity to the 24-hour day/night rhythm in BP are not well understood. We hypothesized that postural changes and physical activity contribute substantially to the day/night rhythm in BP. METHODS Fourteen healthy, sedentary, nonobese, normotensive men (aged 19–50 years) each completed an ambulatory and a bed rest condition during which BP was measured every 30–60 minutes for 24 hours. When ambulatory, subjects followed their usual routines without restrictions to capture the “normal” condition. During bed rest, subjects were constantly confined to bed in a 6-degree head-down position; therefore posture was constant, and physical activity was minimized. Two subjects were excluded from analysis because of irregular sleep timing. RESULTS The systolic and diastolic BP reduction during the sleep period was similar in ambulatory (−11±2mmHg/−8±1mmHg) and bed rest conditions (−8±3mmHg/−4±2mmHg; P = 0.38/P = 0.12). The morning surge in diastolic BP was attenuated during bed rest (P = 0.001), and there was a statistical trend for the same effect in systolic BP (P = 0.06). CONCLUSIONS A substantial proportion of the 24-hour BP rhythm remained during bed rest, indicating that typical daily changes in posture and/or physical activity do not entirely explain 24-hour BP variation under normal ambulatory conditions. However, the morning BP increase was attenuated during bed rest, suggesting that the adoption of an upright posture and/or physical activity in the morning contributes to the morning BP surge. PMID:23535155

Interaction of the vestibular system and baroreflexes on sympathetic nerve activity in humans

NASA Technical Reports Server (NTRS)

Ray, C. A.

2000-01-01

Muscle sympathetic nerve activity (MSNA) is altered by vestibular otolith stimulation. This study examined interactive effects of the vestibular system and baroreflexes on MSNA in humans. In study 1, MSNA was measured during 4 min of lower body negative pressure (LBNP) at either -10 or -30 mmHg with subjects in prone posture. During the 3rd min of LBNP, subjects lowered their head over the end of a table (head-down rotation, HDR) to engage the otolith organs. The head was returned to baseline upright position during the 4th min. LBNP increased MSNA above baseline during both trials with greater increases during the -30-mmHg trial. HDR increased MSNA further during the 3rd min of LBNP at -10 and -30 mmHg (Delta32% and Delta34%, respectively; P < 0.01). MSNA returned to pre-HDR levels during the 4th min of LBNP when the head was returned upright. In study 2, MSNA was measured during HDR, LBNP, and simultaneously performed HDR and LBNP. The sum of MSNA responses during individual HDR and LBNP trials was not significantly different from that observed during HDR and LBNP performed together (Delta131 +/- 28 vs. Delta118 +/- 47 units and Delta340 +/- 77 vs. Delta380 +/- 90 units for the -10 and -30 trials, respectively). These results demonstrate that vestibular otolith stimulation can increase MSNA during unloading of the cardiopulmonary and arterial baroreflexes. Also, the interaction between the vestibulosympathetic reflex and baroreflexes is additive in humans. These studies indicate that the vestibulosympathetic reflex may help defend against orthostatic challenges in humans by increasing sympathetic outflow.

Fluid Shifts

NASA Technical Reports Server (NTRS)

Stenger, M. B.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Laurie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Lui, J.;

Transcapillary fluid shifts in head and neck tissues during and after simulated microgravity

NASA Technical Reports Server (NTRS)

Parazynski, S. E.; Hargens, Alan R.; Tucker, B.; Aratow, M.; Styf, J.; Crenshaw, A.

1991-01-01

To understand the mechanism, magnitude, and time course of facial puffiness that occurs in microgravity, seven male subjects were tilted 6 degrees head down for 8 hr, and all four Starling transcapillary pressures were directly measured before, during, and after tilt. Head-down tilt (HDT) caused facial edema and a significant elevation of microvascular pressures measured in the lower lip: capillary pressures increased from 27.2 +/- 5 mm Hg pre-HDT to 33.9 +/- 1.7 mm Hg by the end of tilt. Subcutaneous and intramuscular interstitial fluid pressures in the neck also increased as a result of HDT, while interstitial fluid colloid osmotic pressures remained unchanged. Plasma colloid osmotic pressures dropped significantly after 4 hr of HDT, suggesting a transition from fluid filtration to absorption in capillary beds between the heart and feet during HDT. After 4 hr of seated recovery from HDT, microvascular pressures remained significantly elevated by 5 to 8 mm Hg above baseline values, despite a significant HDT diuresis and the orthostatic challenge of an upright, seated posture. During the control (baseline) period, urine output was 46.7 ml/hr; during HDT, it was 126.5 ml/hr. These results indicate that facial edema resulting from HDT is primarily caused by elevated capillary pressures and decreased plasma colloid osmotic pressures. Elevation of cephalic capillary pressures sustained for 4 hr after HDT suggests that there is a compensatory vasodilation to maintain microvascular perfusion. The negativity of interstitial fluid pressures above heart level also has implications for the maintenance of tissue fluid balance in upright posture.

The Human Shoulder Suspension Apparatus: A Causal Explanation for Bilateral Asymmetry and a Fresh Look at the Evolution of Human Bipedality.

PubMed

Osborn, Michelle L; Homberger, Dominique G

2015-09-01

The combination of large mastoid processes and clavicles is unique to humans, but the biomechanical and evolutionary significance of their special configuration is poorly understood. As part of the newly conceptualized shoulder suspension apparatus, the mastoid processes and clavicles are shaped by forces exerted by the musculo-fascial components of the cleidomastoid and clavotrapezius muscles as they suspend the shoulders from the head. Because both skeletal elements develop during infancy in tandem with the attainment of an upright posture, increased manual dexterity, and the capacity for walking, we hypothesized that the same forces would have shaped them as the shoulder suspension apparatus evolved in ancestral humans in tandem with an upright posture, increased manual dexterity, and bipedality with swinging arms. Because the shoulder suspension apparatus is subjected to asymmetrical forces from handedness, we predicted that its skeletal features would grow asymmetrically. We used this prediction to test our hypothesis in a natural experiment to correlate the size of the skeletal features with the forces exerted on them. We (1) measured biomechanically relevant bony features within the shoulder suspension apparatus in 101 male human specimens (62 of known handedness); and (2) modeled and analyzed the forces within the shoulder suspension apparatus from X-ray CT data. We identified eight right-handed characters and demonstrated the causal relationship between these right-handed characters and the magnitude and direction of forces acting on them. Our data suggest that the presence of the shoulder suspension apparatus in humans was a necessary precondition for human bipedality. © 2015 Wiley Periodicals, Inc.

An investigation of rugby scrimmaging posture and individual maximum pushing force.

PubMed

Wu, Wen-Lan; Chang, Jyh-Jong; Wu, Jia-Hroung; Guo, Lan-Yuen

2007-02-01

Although rugby is a popular contact sport and the isokinetic muscle torque assessment has recently found widespread application in the field of sports medicine, little research has examined the factors associated with the performance of game-specific skills directly by using the isokinetic-type rugby scrimmaging machine. This study is designed to (a) measure and observe the differences in the maximum individual pushing forward force produced by scrimmaging in different body postures (3 body heights x 2 foot positions) with a self-developed rugby scrimmaging machine and (b) observe the variations in hip, knee, and ankle angles at different body postures and explore the relationship between these angle values and the individual maximum pushing force. Ten national rugby players were invited to participate in the examination. The experimental equipment included a self-developed rugby scrimmaging machine and a 3-dimensional motion analysis system. Our results showed that the foot positions (parallel and nonparallel foot positions) do not affect the maximum pushing force; however, the maximum pushing force was significantly lower in posture I (36% body height) than in posture II (38%) and posture III (40%). The maximum forward force in posture III (40% body height) was also slightly greater than for the scrum in posture II (38% body height). In addition, it was determined that hip, knee, and ankle angles under parallel feet positioning are factors that are closely negatively related in terms of affecting maximum pushing force in scrimmaging. In cross-feet postures, there was a positive correlation between individual forward force and hip angle of the rear leg. From our results, we can conclude that if the player stands in an appropriate starting position at the early stage of scrimmaging, it will benefit the forward force production.

Body Context and Posture Affect Mental Imagery of Hands

PubMed Central

Ionta, Silvio; Perruchoud, David; Draganski, Bogdan; Blanke, Olaf

2012-01-01

Different visual stimuli have been shown to recruit different mental imagery strategies. However the role of specific visual stimuli properties related to body context and posture in mental imagery is still under debate. Aiming to dissociate the behavioural correlates of mental processing of visual stimuli characterized by different body context, in the present study we investigated whether the mental rotation of stimuli showing either hands as attached to a body (hands-on-body) or not (hands-only), would be based on different mechanisms. We further examined the effects of postural changes on the mental rotation of both stimuli. Thirty healthy volunteers verbally judged the laterality of rotated hands-only and hands-on-body stimuli presented from the dorsum- or the palm-view, while positioning their hands on their knees (front postural condition) or behind their back (back postural condition). Mental rotation of hands-only, but not of hands-on-body, was modulated by the stimulus view and orientation. Additionally, only the hands-only stimuli were mentally rotated at different speeds according to the postural conditions. This indicates that different stimulus-related mechanisms are recruited in mental rotation by changing the bodily context in which a particular body part is presented. The present data suggest that, with respect to hands-only, mental rotation of hands-on-body is less dependent on biomechanical constraints and proprioceptive input. We interpret our results as evidence for preferential processing of visual- rather than kinesthetic-based mechanisms during mental transformation of hands-on-body and hands-only, respectively. PMID:22479618

[Development of Patient Transfer Techniques based on Postural-stability Principles for the Care Helpers in Nursing Homes and Evaluation of Effectiveness].

PubMed

Ma, Ryewon; Jung, Dukyoo

2016-02-01

This study was done to develop a postural-stability patient transfer technique for care helpers in nursing homes and to evaluate its effectiveness. Four types of patient transfer techniques (Lifting towards the head board of the bed, turning to the lateral position, sitting upright on the bed, transferring from wheel chair to bed) were practiced in accordance with the following three methods; Care helpers habitually used transfer methods (Method 1), patient transfer methods according to care helper standard textbooks (Method 2), and a method developed by the author ensuring postural-stability (Method 3). The care helpers' muscle activity and four joint angles were measured. The collected data were analyzed using the program SPSS Statistic 21.0. To differentiate the muscle activity and joint angle, the Friedman test was executed and the post-hoc analysis was conducted using the Wilcoxon Signed Rank test. Muscle activity was significantly lower during Method 3 compared to Methods 1 and 2. In addition, the joint angle was significantly lower for the knee and shoulder joint angle while performing Method 3 compared to Methods 1 and 2. Findings indicate that using postural-stability patient transfer techniques can contribute to the prevention of musculoskeletal disease which care helpers suffer from due to physically demanding patient care in nursing homes.

The effects of muscle hypotonia and weakness on balance: a study on Prader-Willi and Ehlers-Danlos syndrome patients.

PubMed

Galli, Manuela; Cimolin, Veronica; Vismara, Luca; Grugni, Graziano; Camerota, Filippo; Celletti, Claudia; Albertini, Giorgio; Rigoldi, Chiara; Capodaglio, Paolo

2011-01-01

Prader-Willi syndrome (PWS) and Ehlers-Danlos syndrome (EDS) are two different genetical disorders both characterized, among other features, by muscular hypotonia. Postural control seems to be impaired in both conditions. The aim of the present study was to quantitatively compare postural control in adult PWS and EDS using stabilometric platform to unveil possible common determinants of impaired balance. We enrolled 11 PWS and 21 EDS adult patients and 20 age-matched controls. They were instructed to maintain an upright standing position for 30s with open eyes (OEs) focusing on a 6 cm black circle positioned at a distance of 1.5m. Both PWS and EDS patients were characterized by higher RANGEML, RANGEAP and trajectory length of CoP values as compared to CG. No statistically differences were found between PWS and EDS in terms of any of these parameters. The results demonstrated that both PWS and EDS are characterized by a severe postural instability. Muscle hypotonia and weakness may account for reduced balance capacity. Quantitative characterization of instability is important to identify, develop and enhance rehabilitation interventions. Copyright © 2011 Elsevier Ltd. All rights reserved.

[Adaptation of control mechanisms involved in upright undisturbed stance maintenance during prolonged darkness].

PubMed

Rougier, P

2003-04-01

To assess to which extent the non visual somato-sensorial information may, through a recalibration process, induce a reorganisation by the central nervous system to control undisturbed upright stance. Ten healthy adults were placed in complete darkness for a 24 min period. Their postural performance was recorded through a force platform on which they were required to stand still at regular intervals. Centre of Pressure (CP) displacements, recorded from the platform, were modelled as fractional brownian motion. Through this analysis, one may objectively assess from which distance and for how long the corrective process is initiated with the aim of slowing and retrace its steps. In addition, the degree to which the CP trajectories are successively controlled was determined. Once in complete darkness, an increase of the mean time intervals (Delta(t)) before the corrective process intervenes was observed, the effect being mostly significant for the mediolateral direction. In parallel, the mean distances covered at this Delta(t) were slightly affected for both mediolateral and anteroposterior directions. Lastly, the degree to which the CP trajectories are controlled tended to decrease. These data suggest a reorganisation of the control mechanisms called into play for maintaining an undisturbed upright stance, thus implying participation of the central nervous system. This short-term adaptation is discussed on the basis of our knowledge of long term adaptations previously observed in blind individuals, and also in a rehabilitation perspective.

The effects of whole body vibration combined biofeedback postural control training on the balance ability and gait ability in stroke patients.

PubMed

Uhm, Yo-Han; Yang, Dae-Jung

2017-11-01

[Purpose] The purpose of this study was to examine the effect of biofeedback postural control training using whole body vibration in acute stroke patients on balance and gait ability. [Subjects and Methods] Thirty stroke patients participated in this study and were divided into a group of 10, a group for biofeedback postural control training combined with a whole body vibration, one for biofeedback postural control training combined with an aero-step, and one for biofeedback postural control training. Biorescue was used to measure the limits of stability, balance ability, and Lukotronic was used to measure step length, gait ability. [Results] In the comparison of balance ability and gait ability between the groups for before and after intervention, Group I showed a significant difference in balance ability and gait ability compared to Groups II and III. [Conclusion] This study showed that biofeedback postural control training using whole body vibration is effective for improving balance ability and gait ability in stroke patients.

Delayed Compensatory Postural Adjustments After Lateral Perturbations Contribute to the Reduced Ability of Older Adults to Control Body Balance.

PubMed

Claudino, Renato; Dos Santos, Marcio José; Mazo, Giovana Zarpellon

2017-10-01

The goal of this study was to investigate the timing of compensatory postural adjustments in older adults during body perturbations in the mediolateral direction, circumstances that increase their risk of falls. The latencies of leg and trunk muscle activation to body perturbations at the shoulder level and variables of center of pressure excursion, which characterize postural stability, were analyzed in 40 older adults (nonfallers and fallers evenly split) and in 20 young participants. The older adults exhibited longer latencies of muscular activation in eight out of 15 postural muscles as compared with young participants; for three muscles, the latencies were longer for the older fallers than nonfallers. Simultaneously, the time for the center of pressure displacement reached its peak after the perturbation was significant longer in both groups of older adults. The observed delays in compensatory postural adjustments may affect the older adults' ability to prompt control body balance after postural disturbances and predispose them to falls.

Compression asphyxia in upright suspended position.

PubMed

Tumram, Nilesh Keshav; Ambade, Vipul Namdeorao; Dixit, Pradeep Gangadhar

2014-06-01

In compression asphyxia, the respiration is prevented by external pressure on the body. It is usually due to external force compressing the trunk due to heavy weight over chest/abdomen and is associated with internal injuries. In the present case, the victim was suspended in an upright position owing to wedging of the chest and the abdomen in the gap between 2 parallel bridges undergoing construction. There was neither any heavy weight over the body, nor was any external force applied over the trunk. Moreover, there was neither any severe blunt force injury nor any significant pathological natural disease contributing to the cause of death. The body was wedged in the gap between 2 static hard surfaces. The victim was unable to extricate himself from the position owing to impairment of cognitive responses and coordination due to influence of alcohol. The victim died as a result of "static" asphyxia due to compression of the chest and the abdomen. Compression asphyxia in upright suspended position under this circumstance is very rare and not reported previously to the best of our knowledge.

Physics-based Simulation of Human Posture Using 3D Whole Body Scanning Technology for Astronaut Space Suit Evaluation

NASA Technical Reports Server (NTRS)

Kim, Kyu-Jung

2005-01-01

Over the past few years high precision three-dimensional (3D) full body laser scanners have been developed to be used as a powerful anthropometry tool for quantification of the morphology of the human body. The full body scanner can quickly extract body characteristics in non-contact fashion. It is required for the Anthropometry and Biomechanics Facility (ABF) to have capabilities for kinematics simulation of a digital human at various postures whereas the laser scanner only allows capturing a single static posture at each time. During this summer fellowship period a theoretical study has been conducted to estimate an arbitrary posture with a series of example postures through finite element (FE) approximation and found that four-point isoparametric FE approximation would result in reasonable maximum position errors less than 5%. Subsequent pilot scan experiments demonstrated that a bead marker with a nominal size of 6 mm could be used as a marker for digitizing 3-D coordinates of anatomical landmarks for further kinematic analysis. Two sessions of human subject testing were conducted for reconstruction of an arbitrary postures from a set of example postures for each joint motion for the forearm/hand complex and the whole upper extremity.

The oblique effect is both allocentric and egocentric

PubMed Central

Mikellidou, Kyriaki; Cicchini, Guido Marco; Thompson, Peter G.; Burr, David C.

2016-01-01

Despite continuous movements of the head, humans maintain a stable representation of the visual world, which seems to remain always upright. The mechanisms behind this stability are largely unknown. To gain some insight on how head tilt affects visual perception, we investigate whether a well-known orientation-dependent visual phenomenon, the oblique effect—superior performance for stimuli at cardinal orientations (0° and 90°) compared with oblique orientations (45°)—is anchored in egocentric or allocentric coordinates. To this aim, we measured orientation discrimination thresholds at various orientations for different head positions both in body upright and in supine positions. We report that, in the body upright position, the oblique effect remains anchored in allocentric coordinates irrespective of head position. When lying supine, gravitational effects in the plane orthogonal to gravity are discounted. Under these conditions, the oblique effect was less marked than when upright, and anchored in egocentric coordinates. The results are well explained by a simple “compulsory fusion” model in which the head-based and the gravity-based signals are combined with different weightings (30% and 70%, respectively), even when this leads to reduced sensitivity in orientation discrimination. PMID:26129862

The Contribution of Pre-impact Spine Posture on Human Body Model Response in Whole-body Side Impact.

PubMed

Poulard, David; Subit, Damien; Donlon, John-Paul; Lessley, David J; Kim, Taewung; Park, Gwansik; Kent, Richard W

2014-11-01

The objective of the study was to analyze independently the contribution of pre-impact spine posture on impact response by subjecting a finite element human body model (HBM) to whole-body, lateral impacts. Seven postured models were created from the original HBM: one matching the standard driving posture and six matching pre-impact posture measured for each of six subjects tested in previously published experiments. The same measurements as those obtained during the experiments were calculated from the simulations, and biofidelity metrics based on signals correlation were established to compare the response of HBM to that of the cadavers. HBM responses showed good correlation with the subject response for the reaction forces, the rib strain (correlation score=0.8) and the overall kinematics. The pre-impact posture was found to greatly alter the reaction forces, deflections and the strain time histories mainly in terms of time delay. By modifying only the posture of HBM, the variability in the impact response was found to be equivalent to that observed in the experiments performed with cadavers with different anthropometries. The patterns observed in the responses of the postured HBM indicate that the inclination of the spine in the frontal plane plays a major role. The postured HBM sustained from 2 to 5 bone fractures, including the scapula in some cases, confirming that the pre-impact posture influences the injury outcome predicted by the simulation.

Functional Neuroanatomy for Posture and Gait Control

PubMed Central

Takakusaki, Kaoru

2017-01-01

Here we argue functional neuroanatomy for posture-gait control. Multi-sensory information such as somatosensory, visual and vestibular sensation act on various areas of the brain so that adaptable posture-gait control can be achieved. Automatic process of gait, which is steady-state stepping movements associating with postural reflexes including headeye coordination accompanied by appropriate alignment of body segments and optimal level of postural muscle tone, is mediated by the descending pathways from the brainstem to the spinal cord. Particularly, reticulospinal pathways arising from the lateral part of the mesopontine tegmentum and spinal locomotor network contribute to this process. On the other hand, walking in unfamiliar circumstance requires cognitive process of postural control, which depends on knowledges of self-body, such as body schema and body motion in space. The cognitive information is produced at the temporoparietal association cortex, and is fundamental to sustention of vertical posture and construction of motor programs. The programs in the motor cortical areas run to execute anticipatory postural adjustment that is optimal for achievement of goal-directed movements. The basal ganglia and cerebellum may affect both the automatic and cognitive processes of posturegait control through reciprocal connections with the brainstem and cerebral cortex, respectively. Consequently, impairments in cognitive function by damages in the cerebral cortex, basal ganglia and cerebellum may disturb posture-gait control, resulting in falling. PMID:28122432

Nonlinear Variability of Body Sway in Patients with Phobic Postural Vertigo

PubMed Central

Schniepp, Roman; Wuehr, Max; Pradhan, Cauchy; Novozhilov, Sergej; Krafczyk, Siegbert; Brandt, Thomas; Jahn, Klaus

2013-01-01

Background: Subjective postural imbalance is a key symptom in the somatoform phobic postural vertigo (PPV). It has been assumed that more attentional control of body posture and / or co-contraction of leg muscles during standing is used to minimize the physiological body sway in PPV. Here we analyze nonlinear variability of body sway in patients with PPV in order to disclose changes in postural control strategy associated with PPV. Methods: Twenty patients with PPV and 20 age-matched healthy subjects (HS) were recorded on a stabilometer platform with eyes open (EO), eyes closed (EC), and while standing on a foam rubber with eyes closed (ECF). Spatio-temporal changes of the center of pressure (CoP) displacement were analyzed to assess the structure of postural variability by computing the scaling exponent α and the sample entropy (SEn) of the time series. Results: With EO on firm ground α and SEn of CoP displacement were significantly lower in patients (p < 0.001). For more difficult conditions (EC, ECF) postural variability in PPV assimilated to that of HS. Conclusion: Postural control in PPV patients differs from HS under normal stance condition. It is characterized by a reduced scaling behavior and higher regularity. These changes in the structure of postural variability might suggest an inappropriate attentional involvement with stabilizing strategies, which are used by HS only for more demanding balance tasks. PMID:23966974

The Subjective Postural Vertical Determined in Patients with Pusher Behavior During Standing.

PubMed

Bergmann, Jeannine; Krewer, Carmen; Selge, Charlotte; Müller, Friedemann; Jahn, Klaus

2016-06-01

The subjective postural vertical (SPV), i.e., the perceived upright orientation of the body in relation to gravity, is disturbed in patients with pusher behavior. So far, the SPV has been measured only when these patients were sitting, and the results were contradictory as regards the side of the SPV deviation. The objective was to investigate the SPV in patients with different degrees of severity of pusher behavior while standing. Eight stroke patients with pusher behavior, ten age-matched stroke patients without pusher behavior, and ten age-matched healthy control subjects were included. The SPV (SPV error, SPV range) was assessed in the pitch and the roll planes. Pusher behavior was classified with the Burke Lateropulsion Scale (BLS). In the pitch plane, the SPV range was significantly larger in pusher patients than in patients without pusher behavior or healthy controls. The SPV error was similar for groups. In the roll plane, the SPV error and the SPV range were significantly larger and more ipsilesionally tilted in the pusher group than in the other two groups. There was a significant correlation between the SPV error in the roll plane and the BLS score. The study revealed that patients with pusher behavior had an ipsilesional SPV tilt that decreased with decreasing severity of the behavior. The large uncertainty in verticality estimation in both planes indicates that their sensitivity for the perception of verticality in space is generally disturbed. These findings emphasize the importance of specific rehabilitation approaches to recalibrate the impaired inner model of verticality.

Positional Change in Displacement of Midshaft Clavicle Fractures: An Aid to Initial Evaluation.

PubMed

Malik, Awais; Jazini, Ehsan; Song, Xuyang; Johal, Herman; OʼHara, Nathan; Slobogean, Gerard; Abzug, Joshua M

2017-01-01

To determine how change in position affects displacement of midshaft clavicle fractures. Retrospective review. Level I Trauma Center. Eighty patients with displaced midshaft clavicle fractures and presence of supine and semiupright or upright chest radiographs taken within 2 weeks of each other. Supine, semiupright, and upright chest radiographs. Fracture shortening and vertical displacement on supine, semiupright, and upright radiographs. Mean vertical displacement was 9.42 mm [95% confidence interval (95% CI), 8.07-10.77 mm], 11.78 mm (95% CI, 10.25-13.32 mm), and 15.72 mm (95% CI, 13.71-17.72 mm) in supine, semiupright, and upright positions, respectively. Fracture shortening was -0.41 mm (95% CI, -2.53 to 1.70 mm), 2.11 mm (95% CI, -0.84 to 5.07), and 4.86 mm (95% CI, 1.66-8.06 mm) in supine, semiupright, and upright positions, respectively. Change in position from supine to upright significantly increased both vertical displacement and fracture shortening (P < 0.001). In the upright position, the proportion of patients who met operative indications (fracture shortening >20 mm) was 3 times greater when compared with that in the supine position (upright 17.65%; supine 5.88%, P = 0.06). Positional changes in fracture displacement were not associated with body mass index, age, or gender. Patient position is associated with significant changes in fracture displacement. Over 3 times more patients meet operative indications when placed in the upright versus supine position. An upright chest radiograph should be obtained to evaluate midshaft clavicle fracture displacement, as it represents the physiologic stress across the fracture when considering nonoperative management. Prognostic level IV. See Instructions for Authors for a complete description of levels of evidence.

Remote monitoring of soldier safety through body posture identification using wearable sensor networks

NASA Astrophysics Data System (ADS)

Biswas, Subir; Quwaider, Muhannad

2008-04-01

The physical safety and well being of the soldiers in a battlefield is the highest priority of Incident Commanders. Currently, the ability to track and monitor soldiers rely on visual and verbal communication which can be somewhat limited in scenarios where the soldiers are deployed inside buildings and enclosed areas that are out of visual range of the commanders. Also, the need for being stealth can often prevent a battling soldier to send verbal clues to a commander about his or her physical well being. Sensor technologies can remotely provide various data about the soldiers including physiological monitoring and personal alert safety system functionality. This paper presents a networked sensing solution in which a body area wireless network of multi-modal sensors can monitor the body movement and other physiological parameters for statistical identification of a soldier's body posture, which can then be indicative of the physical conditions and safety alerts of the soldier in question. The specific concept is to leverage on-body proximity sensing and a Hidden Markov Model (HMM) based mechanism that can be applied for stochastic identification of human body postures using a wearable sensor network. The key idea is to collect relative proximity information between wireless sensors that are strategically placed over a subject's body to monitor the relative movements of the body segments, and then to process that using HMM in order to identify the subject's body postures. The key novelty of this approach is a departure from the traditional accelerometry based approaches in which the individual body segment movements, rather than their relative proximity, is used for activity monitoring and posture detection. Through experiments with body mounted sensors we demonstrate that while the accelerometry based approaches can be used for differentiating activity intensive postures such as walking and running, they are not very effective for identification and differentiation between low activity postures such as sitting and standing. We develop a wearable sensor network that monitors relative proximity using Radio Signal Strength indication (RSSI), and then construct a HMM system for posture identification in the presence of sensing errors. Controlled experiments using human subjects were carried out for evaluating the accuracy of the HMM identified postures compared to a naÃve threshold based mechanism, and its variations over different human subjects. A large spectrum of target human postures, including lie down, sit (straight and reclined), stand, walk, run, sprint and stair climbing, are used for validating the proposed system.

Transient cardio-respiratory responses to visually induced tilt illusions

NASA Technical Reports Server (NTRS)

Wood, S. J.; Ramsdell, C. D.; Mullen, T. J.; Oman, C. M.; Harm, D. L.; Paloski, W. H.

2000-01-01

Although the orthostatic cardio-respiratory response is primarily mediated by the baroreflex, studies have shown that vestibular cues also contribute in both humans and animals. We have demonstrated a visually mediated response to illusory tilt in some human subjects. Blood pressure, heart and respiration rate, and lung volume were monitored in 16 supine human subjects during two types of visual stimulation, and compared with responses to real passive whole body tilt from supine to head 80 degrees upright. Visual tilt stimuli consisted of either a static scene from an overhead mirror or constant velocity scene motion along different body axes generated by an ultra-wide dome projection system. Visual vertical cues were initially aligned with the longitudinal body axis. Subjective tilt and self-motion were reported verbally. Although significant changes in cardio-respiratory parameters to illusory tilts could not be demonstrated for the entire group, several subjects showed significant transient decreases in mean blood pressure resembling their initial response to passive head-up tilt. Changes in pulse pressure and a slight elevation in heart rate were noted. These transient responses are consistent with the hypothesis that visual-vestibular input contributes to the initial cardiovascular adjustment to a change in posture in humans. On average the static scene elicited perceived tilt without rotation. Dome scene pitch and yaw elicited perceived tilt and rotation, and dome roll motion elicited perceived rotation without tilt. A significant correlation between the magnitude of physiological and subjective reports could not be demonstrated.

The Efficacy of the Upright Position on Gastro-Esophageal Reflux and Reflux-Related Respiratory Symptoms in Infants With Chronic Respiratory Symptoms

PubMed Central

Jung, Woo Jin; Yang, Hyeon Jong; Min, Taek Ki; Jeon, You Hoon; Lee, Hae Won; Lee, Jun Sung

2012-01-01

Purpose Gastro-esophageal reflux (GER), particularly non-acid reflux, is common in infants and is a known cause of chronic respiratory symptoms in infancy. Recent guidelines recommended empirical acid suppression therapy and the head-up position in patients with suspected GER. However, the efficacy of the upright position in relieving GER and reflux-related respiratory symptoms in infants is unclear. We conducted this study to investigate the efficacy of the upright position on GER and reflux-related respiratory symptoms in infants with chronic respiratory symptoms. Methods Thirty-two infants (21 male; median age, 5 months; range, 0 to 19 months) with unexplained chronic respiratory symptoms underwent multi-channel intraluminal esophageal impedance and pH monitoring. We retrospectively compared the frequencies of GER and reflux-related symptoms according to body position. Results A mean of 3.30 episodes of reflux per hour was detected. Overall, refluxes were more frequent during the postprandial period than the emptying period (3.77 vs. 2.79 episodes/hour, respectively; P=0.01). Although there was no significant difference in the total refluxes per hour between the upright and recumbent positions (6.12 vs. 3.77 episodes, P=0.10), reflux-related respiratory symptoms per reflux were significantly fewer in infants kept in an upright position than in a recumbent position during the postprandial period (3.07% vs. 14.75%, P=0.016). Non-acid reflux was the predominant type of reflux in infants, regardless of body position or meal time. Conclusions The upright position may reduce reflux-related respiratory symptoms, rather than reflux frequency. Thus, it may be a useful non-pharmacological treatment for infantile GER disease resistant to acid suppressants. PMID:22211166

The efficacy of the upright position on gastro-esophageal reflux and reflux-related respiratory symptoms in infants with chronic respiratory symptoms.

PubMed

Jung, Woo Jin; Yang, Hyeon Jong; Min, Taek Ki; Jeon, You Hoon; Lee, Hae Won; Lee, Jun Sung; Pyun, Bok Yang

2012-01-01

Gastro-esophageal reflux (GER), particularly non-acid reflux, is common in infants and is a known cause of chronic respiratory symptoms in infancy. Recent guidelines recommended empirical acid suppression therapy and the head-up position in patients with suspected GER. However, the efficacy of the upright position in relieving GER and reflux-related respiratory symptoms in infants is unclear. We conducted this study to investigate the efficacy of the upright position on GER and reflux-related respiratory symptoms in infants with chronic respiratory symptoms. Thirty-two infants (21 male; median age, 5 months; range, 0 to 19 months) with unexplained chronic respiratory symptoms underwent multi-channel intraluminal esophageal impedance and pH monitoring. We retrospectively compared the frequencies of GER and reflux-related symptoms according to body position. A mean of 3.30 episodes of reflux per hour was detected. Overall, refluxes were more frequent during the postprandial period than the emptying period (3.77 vs. 2.79 episodes/hour, respectively; P=0.01). Although there was no significant difference in the total refluxes per hour between the upright and recumbent positions (6.12 vs. 3.77 episodes, P=0.10), reflux-related respiratory symptoms per reflux were significantly fewer in infants kept in an upright position than in a recumbent position during the postprandial period (3.07% vs. 14.75%, P=0.016). Non-acid reflux was the predominant type of reflux in infants, regardless of body position or meal time. The upright position may reduce reflux-related respiratory symptoms, rather than reflux frequency. Thus, it may be a useful non-pharmacological treatment for infantile GER disease resistant to acid suppressants.

Concepts on the pathogenesis of adolescent idiopathic scoliosis. Bone growth and mass, vertebral column, spinal cord, brain, skull, extra-spinal left-right skeletal length asymmetries, disproportions and molecular pathogenesis.

PubMed

Burwell, R Geoffrey; Dangerfield, Peter H; Freeman, Brian J C

2008-01-01

There is no generally accepted scientific theory for the causes of adolescent idiopathic scoliosis (AIS). Encouraging advances thought to be related to AIS pathogenesis have recently been made in several fields including anthropometry of bone growth, bone mass, spinal growth modulation, extra-spinal left-right skeletal length asymmetries and disproportions, magnetic resonance imaging of vertebral column, spinal cord, brain, skull, and molecular pathogenesis. These advances are leading to the evaluation of new treatments including attempts at minimally invasive surgery on the spine and peri-apical ribs. Several concepts of AIS are outlined indicating their clinical applications but not their research potential. The concepts, by derivation morphological, molecular and mathematical, are addressed in 15 sections: 1) initiating and progressive factors; 2) relative anterior spinal overgrowth; 3) dorsal shear forces that create axial rotational instability; 4) rotational preconstraint; 5) uncoupled, or asynchronous, spinal neuro-osseous growth; 6) brain, nervous system and skull; 7) a novel neuro-osseous escalator concept based on a putative abnormality of two normal polarized processes namely, a) increasing skeletal dimensions, and b) the CNS body schema - both contained within a neuro-osseous timing of maturation (NOTOM) concept; 8) transverse plane pelvic rotation, skeletal asymmetries and developmental theory; 9) thoraco-spinal concept; 10) origin in contracture at the hips; 11) osteopenia; 12) melatonin deficiency; 13) systemic melatonin-signaling pathway dysfunction; 14) platelet calmodulin dysfunction; and 15) biomechanical spinal growth modulation. From these concepts, a collective model for AIS pathogenesis is formulated. The central concept of this model includes the body schema of the neural systems, widely-studied in adults, that control normal posture and coordinated movements with frames of reference in the posterior parietal cortex. The escalator concept has implications for the normal development of upright posture, and the evolution in humans of neural control, the trunk and unique bipedal gait.

Effects of Vestibular Loss on Orthostatic Responses to Tilts in the Pitch Plane

NASA Technical Reports Server (NTRS)

Wood, Scott J.; Serrador, Jorge M.; Black, F. Owen; Rupert,Angus H.; Schlegel, Todd T.

2004-01-01

The purpose of this study was to determine the extent to which vestibular loss might impair orthostatic responses to passive tilts in the pitch plane in human subjects. Data were obtained from six subjects having chronic bilateral vestibular loss and six healthy individuals matched for age, gender, and body mass index. Vestibular loss was assessed with a comprehensive battery including dynamic posturography, vestibulo-ocular and optokinetic reflexes, vestibular evoked myogenic potentials, and ocular counterrolling. Head up tilt tests were conducted using a motorized two-axis table that allowed subjects to be tilted in the pitch plane from either a supine or prone body orientation at a slow rate (8 deg/s). The sessions consisted of three tilts, each consisting of20 min rest in a horizontal position, tilt to 80 deg upright for 10 min, and then return to the horizontal position for 5 min. The tilts were performed in darkness (supine and prone) or in light (supine only). Background music was used to mask auditory orientation cues. Autonomic measurements included beat-to-beat recordings of blood pressure (Finapres), heart rate (ECG), cerebral blood flow velocity in the middle cerebral artery (transcranial Doppler), end tidal CO2, respiratory rate and volume (Respritrace), and stroke volume (impedance cardiography). For both patients and control subjects, cerebral blood flow appeared to exhibit the most rapid adjustment following transient changes in posture. Outside of a greater cerebral hypoperfusion in patients during the later stages of tilt, responses did not differ dramatically between the vestibular loss and control subjects, or between tilts performed in light and dark room conditions. Thus, with the 'exception of cerebrovascular regulation, we conclude that orthostatic responses during slow postural tilts are not substantially impaired in humans following chronic loss of vestibular function, a result that might reflect compensation by nonvisual graviceptor inputs (e.g., somatosensory) or other circulatory reflex mechanisms.

Effects of body position on the ventilatory response following an impulse exercise in humans.

PubMed

Haouzi, Philippe; Chenuel, Bruno; Chalon, Bernard

2002-04-01

The aim of this study was to identify some of the mechanisms that could be involved in blunted ventilatory response (VE) to exercise in the supine (S) position. The contribution of the recruitment of different muscle groups, the activity of the cardiac mechanoreceptors, the level of arterial baroreceptor stimulation, and the hemodynamic effects of gravity on the exercising muscles was analyzed during upright (U) and S exercise. Delayed rise in VE and pulmonary gas exchange following an impulselike change in work rate (supramaximal leg cycling at 240 W for 12 s) was measured in seven healthy subjects and six heart transplant patients both in U and S positions. This approach allows study of the relationship between the rise in VE and O2 uptake (VO2) without the confounding effects of contractions of different muscle groups. These responses were compared with those triggered by an impulselike change in work rate produced by the arms, which were positioned at the same level as the heart in S and U positions to separate effects of gravity on postexercising muscles from those on the rest of the body. Despite superimposable VO2 and CO2 output responses, the delayed VE response after leg exercise was significantly lower in the S posture than in the U position for each control subject and cardiac-transplant patient (-2.58 +/- 0.44 l and -3.52 +/- 1.11 l/min, respectively). In contrast, when impulse exercise was performed with the arms, reduction of ventilatory response in the S posture reached, at best, one-third of the deficit after leg exercise and was always associated with a reduction in VO2 of a similar magnitude. We concluded that reduction in VE response to exercise in the S position is independent of the types (groups) of muscles recruited and is not critically dependent on afferent signals originating from the heart but seems to rely on some of the effects of gravity on postexercising muscles.

Spatial acoustic radiation of respiratory sounds for sleep evaluation.

PubMed

Shabtai, Noam R; Zigel, Yaniv

2017-09-01

Body posture has an effect on sleeping quality and breathing disorders and therefore it is important to be recognized for the completion of the sleep evaluation process. Since humans have a directional acoustic radiation pattern, it is hypothesized that microphone arrays can be used to recognize different body postures, which is highly practical for sleep evaluation applications that already measure respiratory sounds using distant microphones. Furthermore, body posture may have an effect on distant microphone measurement; hence, the measurement can be compensated if the body posture is correctly recognized. A spherical harmonics decomposition approach to the spatial acoustic radiation is presented, assuming an array of eight microphones in a medium-sized audiology booth. The spatial sampling and reconstruction of the radiation pattern is discussed, and a final setup for the microphone array is recommended. A case study is shown using recorded segments of snoring and breathing sounds of three human subjects in three body postures in a silent but not anechoic audiology booth.

Body Posture Facilitates Retrieval of Autobiographical Memories

ERIC Educational Resources Information Center

Dijkstra, Katinka; Kaschak, Michael P.; Zwaan, Rolf A.

2007-01-01

We assessed potential facilitation of congruent body posture on access to and retention of autobiographical memories in younger and older adults. Response times were shorter when body positions during prompted retrieval of autobiographical events were similar to the body positions in the original events than when body position was incongruent.…

"Stand up straight": notes toward a history of posture.

PubMed

Gilman, Sander L

2014-03-01

The essay presents a set of interlinked claims about posture in modern culture. Over the past two centuries it has come to define a wide range of assumptions in the West from what makes human beings human (from Lamarck to Darwin and beyond) to the efficacy of the body in warfare (from Dutch drill manuals in the 17th century to German military medical studies of soldiers in the 19th century). Dance and sport both are forms of posture training in terms of their own claims. Posture separates 'primitive' from 'advanced' peoples and the 'ill' from the 'healthy.' Indeed an entire medical sub-specialty developed in which gymnastics defined and recuperated the body. But all of these claims were also part of a Western attempt to use posture (and the means of altering it) as the litmus test for the healthy modern body of the perfect citizen. Focusing on the centrality of posture in two oddly linked moments of modern thought--modern Zionist thought and Nationalism in early 20th century China--in terms of bodily reform, we show how "posture" brings all of the earlier debates together to reform the body.

Effects of experimental insoles on body posture, mandibular kinematics and masticatory muscles activity. A pilot study in healthy volunteers.

PubMed

Marini, Ida; Alessandri Bonetti, Giulio; Bortolotti, Francesco; Bartolucci, Maria Lavinia; Gatto, Maria Rosaria; Michelotti, Ambra

2015-06-01

It has been hypothesized that different plantar sensory inputs could influence the whole body posture and dental occlusion but there is a lack of evidence on this possible association. To investigate the effects of experimental insoles redistributing plantar pressure on body posture, mandibular kinematics and electromyographic (EMG) activity of masticatory muscles on healthy subjects. A pilot study was conducted on 19 healthy volunteers that wore custom-made insoles normalizing the plantar pressure distribution for 2 weeks. Body posture parameters were measured by means of an optoelectronic stereophotogrammetric analysis; mandibular kinematics was analyzed by means of gothic arch tracings; superficial EMG activity of head and neck muscles was performed. Measurements were carried out 10 days before the insertion of the insoles, immediately before the insertion, the day after, 7 and 14 days after, in four different exteroceptive conditions. The outcomes of the present study show that insoles do not modify significantly over time the parameters of body posture, SEMG activity of head and neck muscles and mandibular kinematics. In this pilot study the experimental insoles did not significantly influence the body posture, the mandibular kinematics and the activity of masticatory muscles during a 14-day follow up period. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of mat pilates exercise on postural alignment and body composition of middle-aged women.

PubMed

Lee, Hyo Taek; Oh, Hyun Ok; Han, Hui Seung; Jin, Kwang Youn; Roh, Hyo Lyun

2016-06-01

[Purpose] This study attempted to examine whether Pilates is an effective exercise for improving the postural alignment and health of middle-aged women. [Subjects and Methods] The participants in this study were 36 middle-aged women (20 in the experimental group, 16 in the control group). The experimental group participated in Pilates exercise sessions three times a week for 12 weeks. Body alignment and composition measurements before and after applying the Pilates exercise program were performed with a body composition analyzer and a three-dimensional scanner. [Results] Postural alignment in the sagittal and horizontal planes was enhanced in the Pilates exercise group. Trunk alignment showed correlations with body fat and muscle mass. [Conclusion] The Pilates exercises are performed symmetrically and strengthen the deep muscles. Moreover, the results showed that muscle mass was correlated with trunk postural alignment and that the proper amount of muscle is critical in maintaining trunk postural alignment.

Pelvic morphology, body posture and standing balance characteristics of adolescent able-bodied and idiopathic scoliosis girls.

PubMed

Stylianides, Georgios A; Dalleau, Georges; Begon, Mickaël; Rivard, Charles-Hilaire; Allard, Paul

2013-01-01

The purpose of this study was to determine how pelvic morphology, body posture, and standing balance variables of scoliotic girls differ from those of able-bodied girls, and to classify neuro-biomechanical variables in terms of a lower number of unobserved variables. Twenty-eight scoliotic and twenty-five non-scoliotic able-bodied girls participated in this study. 3D coordinates of ten anatomic body landmarks were used to describe pelvic morphology and trunk posture using a Flock of Birds system. Standing balance was measured using a force plate to identify the center of pressure (COP), and its anteroposterior (AP) and mediolateral (ML) displacements. A multivariate analysis of variance (MANOVA) was performed to determine differences between the two groups. A factor analysis was used to identify factors that best describe both groups. Statistical differences were identified between the groups for each of the parameter types. While spatial orientation of the pelvis was similar in both groups, five of the eight trunk postural variables of the scoliotic group were significantly different that the able-bodied group. Also, five out of the seven standing balance variables were higher in the scoliotic girls. Approximately 60% of the variation is supported by 4 factors that can be associated with a set of variables; standing balance variables (factor 1), body posture variables (factor 2), and pelvic morphology variables (factors 3 and 4). Pelvic distortion, body posture asymmetry, and standing imbalance are more pronounced in scoliotic girls, when compared to able-bodied girls. These findings may be beneficial when addressing balance and ankle proprioception exercises for the scoliotic population.

Effect of an Ergonomics-Based Educational Intervention Based on Transtheoretical Model in Adopting Correct Body Posture Among Operating Room Nurses

PubMed Central

Moazzami, Zeinab; Dehdari, Tahere; Taghdisi, Mohammad Hosein; Soltanian, Alireza

2016-01-01

Background: One of the preventive strategies for chronic low back pain among operating room nurses is instructing proper body mechanics and postural behavior, for which the use of the Transtheoretical Model (TTM) has been recommended. Methods: Eighty two nurses who were in the contemplation and preparation stages for adopting correct body posture were randomly selected (control group = 40, intervention group = 42). TTM variables and body posture were measured at baseline and again after 1 and 6 months after the intervention. A four-week ergonomics educational intervention based on TTM variables was designed and conducted for the nurses in the intervention group. Results: Following the intervention, a higher proportion of nurses in the intervention group moved into the action stage (p < 0.05). Mean scores of self-efficacy, pros, experimental processes and correct body posture were also significantly higher in the intervention group (p < 0.05). No significant differences were found in the cons and behavioral processes, except for self-liberation, between the two groups (p > 0.05) after the intervention. Conclusions: The TTM provides a suitable framework for developing stage-based ergonomics interventions for postural behavior. PMID:26925897

Effect of an Ergonomics-Based Educational Intervention Based on Transtheoretical Model in Adopting Correct Body Posture Among Operating Room Nurses.

PubMed

Moazzami, Zeinab; Dehdari, Tahere; Taghdisi, Mohammad Hosein; Soltanian, Alireza

2015-11-03

One of the preventive strategies for chronic low back pain among operating room nurses is instructing proper body mechanics and postural behavior, for which the use of the Transtheoretical Model (TTM) has been recommended. Eighty two nurses who were in the contemplation and preparation stages for adopting correct body posture were randomly selected (control group = 40, intervention group = 42). TTM variables and body posture were measured at baseline and again after 1 and 6 months after the intervention. A four-week ergonomics educational intervention based on TTM variables was designed and conducted for the nurses in the intervention group. Following the intervention, a higher proportion of nurses in the intervention group moved into the action stage (p < 0.05). Mean scores of self-efficacy, pros, experimental processes and correct body posture were also significantly higher in the intervention group (p < 0.05). No significant differences were found in the cons and behavioral processes, except for self-liberation, between the two groups (p > 0.05) after the intervention. The TTM provides a suitable framework for developing stage-based ergonomics interventions for postural behavior.

Reducing musculoskeletal disorders among computer operators: comparison between ergonomics interventions at the workplace.

PubMed

Levanon, Yafa; Gefen, Amit; Lerman, Yehuda; Givon, Uri; Ratzon, Navah Z

2012-01-01

Typing is associated with musculoskeletal disorders (MSDs) caused by multiple risk factors. This control study aimed to evaluate the efficacy of a workplace intervention for reducing MSDs among computer workers. Sixty-six subjects with and without MSD were assigned consecutively to one of three groups: ergonomics intervention (work site and body posture adjustments, muscle activity training and exercises) accompanied with biofeedback training, the same ergonomics intervention without biofeedback and a control group. Evaluation of MSDs, body posture, psychosocial status, upper extremity (UE) kinematics and muscle surface electromyography were carried out before and after the intervention in the workplace and the motion lab. Our main hypothesis that significant differences in the reduction of MSDs will exist between subjects in the study groups and controls was confirmed (χ(2) = 13.3; p = 0.001). Significant changes were found in UE kinematics and posture as well. Both ergonomics interventions effectively reduced MSD and improved body posture. This study aimed to test the efficacy of an individual workplace intervention programme among computer workers by evaluating musculoskeletal disorders (MSDs), body posture, upper extremity kinematics, muscle activity and psychosocial factors were tested. The proposed ergonomics interventions effectively reduced MSDs and improved body posture.

Implication of Posture Analysing Software to Evaluate the Postural Changes after Corrective Exercise Strategy on Subjects with Upper Body Dysfunction-A Randomized Controlled Trial

PubMed Central

Sudhakar, S; Porcelvan, S; Francis, T.G. Tilak; Rathnamala, D; Radhakrishnan, R

2017-01-01

Introduction The postural adaptation is very common now a days in school going children, office desk oriented job, computer users and frequent mobile users, and in all major industrial workers. Several studies have documented a high incidence of postural abnormalities in a given population; however, methods of postural measurement were poorly defined. The implication of postural pro software to analyse the postural imbalance of upper body dysfunction is very rare and literature studies says that the kinematic changes in particular segment will produce pain/discomfort and thereby lesser productivity of subjects. Aim To evaluate the postural changes in subjects with upper body dysfunction after a corrective exercise strategy using postural analysis software and pectoralis minor muscle length testing. Materials and Methods After explaining the procedure and benefits, informed consent was taken from the participating subjects (age 25-55 years). Subjects with upper body dysfunction were randomly allocated into two groups (each group 30 subjects). The Group–A received the corrective exercise strategy and Group-B received the conventional exercise for eight weeks of study duration (15 reps each exercise, total duration of 40 min; four days/week. Pre and Post posture analysis were analysed using posture pro software along with flexibility of pectoralis minor was assessed using ruler scale method. Results After interpretation of data, both the group showed the postural alteration and pectoralis minor muscle length changes, p-value (p<0.01) of both group showed highly significant changes. But comparing the both groups, the subjects who received the corrective exercise strategy shown more percentage of improvement in posture alteration (56.25%), pectoralis minor muscle length changes (68.69%) than the conventional exercise received subjects in posture alteration (24.86%) and pectoralis minor muscle length changes (21.9%). Conclusion Altered postural changes and pectoralis minor muscle flexibility before and after the corrective exercise strategy evaluated by postural analysis software method shown to be a significant tool in clinical practice, which is easier and reproducible method. PMID:28893030

Analysis of Relationship between the Body Mass Composition and Physical Activity with Body Posture in Children

PubMed Central

Baran, Joanna; Czenczek-Lewandowska, Ewelina; Leszczak, Justyna; Mazur, Artur

2016-01-01

Introduction. Excessive body mass in turn may contribute to the development of many health disorders including disorders of musculoskeletal system, which still develops intensively at that time. Aim. The aim of this study was to assess the relationship between children's body mass composition and body posture. The relationship between physical activity level of children and the parameters characterizing their posture was also evaluated. Material and Methods. 120 school age children between 11 and 13 years were enrolled in the study, including 61 girls and 59 boys. Each study participant had the posture evaluated with the photogrammetric method using the projection moiré phenomenon. Moreover, body mass composition and the level of physical activity were evaluated. Results. Children with the lowest content of muscle tissue showed the highest difference in the height of the inferior angles of the scapulas in the coronal plane. Children with excessive body fat had less slope of the thoracic-lumbar spine, greater difference in the depth of the inferior angles of the scapula, and greater angle of the shoulder line. The individuals with higher level of physical activity have a smaller angle of body inclination. Conclusion. The content of muscle tissue, adipose tissue, and physical activity level determines the variability of the parameter characterizing the body posture. PMID:27761467

Effects of the removal of vision on body sway during different postures in elite gymnasts.

PubMed

Asseman, F; Caron, O; Crémieux, J

2005-03-01

The aim of this study was to analyse the effects of the removal of vision on postural performance and postural control in function of the difficulty and specificity of the posture. Twelve elite gymnasts were instructed to be as stable as possible with eyes open and eyes closed in three postures: bipedal, unipedal, and handstand ranked from the less difficult and less specific to the more difficult and more specific. The ratios eyes closed on eyes open, computed on CP surface and CP mean velocity, which respectively represents postural performance and postural control, were similar in the bipedal and handstand postures. They were highly increased in the unipedal one. The effect of the removal of vision and so the role of vision on body sway was not directly linked to the difficulty or specificity of the posture; other tasks' characteristics like the segments configuration also played a role.

Ergonomic Evaluation of Dental Professionals as Determined by Rapid Entire Body Assessment Method in 2014

PubMed Central

Jahanimoghadam, Fatemeh; Horri, Azadeh; Hasheminejad, Naimeh; Hashemi Nejad, Naser; Baneshi, Mohammad Reza

2018-01-01

Statement of the Problem: In dentistry, incorrect working posture is the most important cause of musculoskeletal disorders. Purpose: The aim of this research was to evaluate the work postures of general dentists and specialists using rapid entire body assessment (REBA) method. Materials and Method: In this cross-sectional study, work postures were assessed in 90 dentists by employing REBA method. Stratified sampling method was used. Data were analyzed by analysis of variance (ANOVA), Independent t-test and Pearson’s correlation test in SPSS 19. Results: The results showed that work postures of 90% of dentists were at moderate- to high-risk levels. Among the specialists, periodontists, pedodontists and oral and maxillofacial surgeons had the worst body postures. Conclusion: In general, dentists’ working postures need improvement and consequently, a more comprehensive ergonomic training and promotion is required in dentistry curriculum at Universities. PMID:29854890

Predictive discomfort in single- and combined-axis whole-body vibration considering different seated postures.

PubMed

DeShaw, Jonathan; Rahmatalla, Salam

2014-08-01

The aim of this study was to develop a predictive discomfort model in single-axis, 3-D, and 6-D combined-axis whole-body vibrations of seated occupants considering different postures. Non-neutral postures in seated whole-body vibration play a significant role in the resulting level of perceived discomfort and potential long-term injury. The current international standards address contact points but not postures. The proposed model computes discomfort on the basis of static deviation of human joints from their neutral positions and how fast humans rotate their joints under vibration. Four seated postures were investigated. For practical implications, the coefficients of the predictive discomfort model were changed into the Borg scale with psychophysical data from 12 volunteers in different vibration conditions (single-axis random fore-aft, lateral, and vertical and two magnitudes of 3-D). The model was tested under two magnitudes of 6-D vibration. Significant correlations (R = .93) were found between the predictive discomfort model and the reported discomfort with different postures and vibrations. The ISO 2631-1 correlated very well with discomfort (R2 = .89) but was not able to predict the effect of posture. Human discomfort in seated whole-body vibration with different non-neutral postures can be closely predicted by a combination of static posture and the angular velocities of the joint. The predictive discomfort model can assist ergonomists and human factors researchers design safer environments for seated operators under vibration. The model can be integrated with advanced computer biomechanical models to investigate the complex interaction between posture and vibration.

DTN routing in body sensor networks with dynamic postural partitioning.

PubMed

Quwaider, Muhannad; Biswas, Subir

2010-11-01

This paper presents novel store-and-forward packet routing algorithms for Wireless Body Area Networks ( WBAN ) with frequent postural partitioning. A prototype WBAN has been constructed for experimentally characterizing on-body topology disconnections in the presence of ultra short range radio links, unpredictable RF attenuation, and human postural mobility. On-body DTN routing protocols are then developed using a stochastic link cost formulation, capturing multi-scale topological localities in human postural movements. Performance of the proposed protocols are evaluated experimentally and via simulation, and are compared with a number of existing single-copy DTN routing protocols and an on-body packet flooding mechanism that serves as a performance benchmark with delay lower-bound. It is shown that via multi-scale modeling of the spatio-temporal locality of on-body link disconnection patterns, the proposed algorithms can provide better routing performance compared to a number of existing probabilistic, opportunistic, and utility-based DTN routing protocols in the literature.

Postural Variables in Girls Practicing Volleyball

ERIC Educational Resources Information Center

Grabara, Malgorzata; Hadzik, Andrzej

2009-01-01

Study aim: To assess body posture of young female volleyball players in relation to their untrained mates. Material and methods: A group of 42 volleyball players and another of 43 untrained girls, all aged 13-16 years were studied with respect to their body posture indices by using computer posturography. Spinal angles and curvatures were…

The effects of whole body vibration combined computerized postural control training on the lower extremity muscle activity and cerebral cortex activity in stroke patients.

PubMed

Uhm, Yo-Han; Yang, Dae-Jung

2018-02-01

[Purpose] The purpose of this study was to examine the effect of computerized postural control training using whole body vibration on lower limb muscle activity and cerebral cortical activation in acute stroke patients. [Subjects and Methods] Thirty stroke patients participated and were divided into groups of 10, a group of the computerized postural control training using whole body vibration (Group I), the computerized postural control training combined with aero step (Group II) and computerized postural control training (Group III). MP100 was used to measure lower limb muscle activity, and QEEG-8 was used to measure cerebral cortical activation. [Results] Comparison of muscle activity and cerebral cortical activation before and after intervention between groups showed that Group I had significant differences in lower limb muscle activity and cerebral cortical activation compared to Groups II and III. [Conclusion] This study showed that whole body vibration combined computerized postural control training is effective for improving muscle activity and cerebral cortex activity in stroke patients.

Body posture in children with obesity - the relationship to physical activity (PA).

PubMed

Brzęk, Anna; Sołtys, Jacek; Gallert-Kopyto, Weronika; Gwizdek, Katarzyna; Plinta, Ryszard

2016-01-01

The modern world of electronic devices offers children and young people various forms of leisure activities, while reducing the need for natural movement, necessary for normal psychomotor development. Sedentary life contributes to an increased body weight and, thereby, to the development of body posture abnormalities. The aim of the study was to evaluate body posture, leisure activities, and the number of hours spent using electronic devices among children with obesity. The study involved 51 children with obesity (BMI above 95 percentile) - A group, and 69 children with normal body weight at the age of 9-13 years (10.98 ± 1.29) - B group (control). Body posture has been evaluated with the scoliometer, the digital inclinometer and the plumb line. The hump ratio has been calculated on the basis of SOSORT recommendations. Time spent in front of electronic devices based on a questionnaire results has also been calculated. Children with obesity have more body posture defects in the sagittal plane than children with normal z-scores (p<0.001). 46.8% of children in group A have distorted depth of the two curvatures of the spine. In the control group, the majority of deviations have been observed in the evaluation of the ATR (Angle Trunk Rotation) at the lumbar spine (p<0.05), while in group A, at the level of the thoracic spine (40.42% vs. 23.07%). Both groups of respondents use electronic devices at least 3 days a week (p>0.05). Obese children often use mobile devices, while children with normal body weight often use desktop equipment. Definitely more body posture abnormalities are found in the group of obese children. Children use electronic devices regardless of weight. It is worth to expand educational activities with programs that improve the quality of body posture through a daily change of abnormal patterns. © Polish Society for Pediatric Endocrinology and Diabetology.

Orthostatic Intolerance and Motion Sickness After Parabolic Flight

NASA Technical Reports Server (NTRS)

Schlegel, Todd T.; Brown, Troy E.; Wood, Scott J.; Benavides, Edgar W.; Bondar, Roberta L.; Stein, Flo; Moradshahi, Peyman; Harm, Deborah L.; Low, Phillip A.

1999-01-01

Orthostatic intolerance is common in astronauts after prolonged space flight. However, the "push-pull effect" in military aviators suggests that brief exposures to transitions between hypo- and hypergravity are sufficient to induce untoward autonomic cardiovascular physiology in susceptible individuals. We therefore investigated orthostatic tolerance and autonomic cardiovascular function in 16 healthy test subjects before and after a seated 2-hr parabolic flight. At the same time, we also investigated relationships between parabolic flight-induced vomiting and changes in orthostatic and autonomic cardiovascular function. After parabolic flight, 8 of 16 subjects could not tolerate a 30-min upright tilt test, compared to 2 of 16 before flight. Whereas new intolerance in non-Vomiters resembled the clinical postural tachycardia syndrome (POTS), new intolerance in Vomiters was characterized by comparatively isolated upright hypocapnia and cerebral vasoconstriction. As a group, Vomiters also had evidence for increased postflight fluctuations in efferent vagal-cardiac nerve traffic occurring independently of any superimposed change in respiration. Results suggest that syndromes of orthostatic intolerance resembling those occurring after space flight can occur after a brief (i.e., 2-hr) parabolic flight.

Individual differences in bodily freezing predict emotional biases in decision making

PubMed Central

Ly, Verena; Huys, Quentin J. M.; Stins, John F.; Roelofs, Karin; Cools, Roshan

2014-01-01

Instrumental decision making has long been argued to be vulnerable to emotional responses. Literature on multiple decision making systems suggests that this emotional biasing might reflect effects of a system that regulates innately specified, evolutionarily preprogrammed responses. To test this hypothesis directly, we investigated whether effects of emotional faces on instrumental action can be predicted by effects of emotional faces on bodily freezing, an innately specified response to aversive relative to appetitive cues. We tested 43 women using a novel emotional decision making task combined with posturography, which involves a force platform to detect small oscillations of the body to accurately quantify postural control in upright stance. On the platform, participants learned whole body approach-avoidance actions based on monetary feedback, while being primed by emotional faces (angry/happy). Our data evidence an emotional biasing of instrumental action. Thus, angry relative to happy faces slowed instrumental approach relative to avoidance responses. Critically, individual differences in this emotional biasing effect were predicted by individual differences in bodily freezing. This result suggests that emotional biasing of instrumental action involves interaction with a system that controls innately specified responses. Furthermore, our findings help bridge (animal and human) decision making and emotion research to advance our mechanistic understanding of decision making anomalies in daily encounters as well as in a wide range of psychopathology. PMID:25071491

The effects of brief swaying on postural control.

PubMed

Pagé, Sara; Maheu, Maxime; Landry, Simon P; Champoux, François

2017-12-06

Postural control can be improved with balance training. However, the nature and duration of the training required to enhance posture remains unclear. We studied the effects of 5 min of a self-initiated balance exercise along a single axis on postural control in healthy individuals. Postural control was measured before and after a 5-min period where members of the experimental group were asked to lean their entire body forward and backward and members of the control group were asked to remain seated. A significant improvement for sway velocity, a postural control variable significantly associated with an increased risk of falls, was found in the experimental group following the body sway exercise. These data suggest that a basic exercise can rapidly improve postural control and reduce the risk of falls.

Using impedance cardiography with postural change to stratify patients with hypertension.

PubMed

DeMarzo, Arthur P

2011-06-01

Early detection of cardiovascular disease in patients with hypertension could initiate appropriate treatment to control blood pressure and prevent the progression of cardiovascular disease. The goal of this study was to show how impedance cardiography waveform analysis with postural change can be used to detect subclinical cardiovascular disease in patients with high blood pressure. Patients with high blood pressure had impedance cardiography data obtained in two positions, standing upright and supine. In 50 adults, impedance cardiography indicated that all patients had abnormal data, with 44 (88%) having multiple abnormalities. Impedance cardiography showed 32 (64%) had ventricular dysfunction, 48 (96%) had vascular load abnormalities, 34 (68%) had hemodynamic abnormalities, 2 (4%) had hypovolemia, and 3 (6%) had hypervolemia. Hypertensive patients have diverse cardiovascular abnormalities that can be quantified by impedance cardiography. By stratifying patients with ventricular, vascular, and hemodynamic abnormalities, treatment could be customized based on the abnormal underlying mechanisms with the potential to rapidly control blood pressure, prevent progression of cardiovascular disease, and possibly reverse remodeling.

Intracranial and Intraocular Pressure at the Lamina Cribrosa: Gradient Effects.

PubMed

Jóhannesson, Gauti; Eklund, Anders; Lindén, Christina

2018-04-12

A pressure difference between the intraocular and intracranial compartments at the site of the lamina cribrosa has been hypothesized to have a pathophysiological role in several optic nerve head diseases. This paper reviews the current literature on the translamina cribrosa pressure difference (TLCPD), the associated pressure gradient, and its potential pathophysiological role, as well as the methodology to assess TLCPD. For normal-tension glaucoma (NTG), initial studies indicated low intracranial pressure (ICP) while recent findings indicate that a reduced ICP is not mandatory. Data from studies on the elevated TLCPD as a pathophysiological factor of NTG are equivocal. From the identification of potential postural effects on the cerebrospinal fluid (CSF) communication between the intracranial and retrolaminar space, we hypothesize that the missing link could be a dysfunction of an occlusion mechanism of the optic nerve sheath around the optic nerve. In upright posture, this could cause an elevated TLCPD even with normal ICP and we suggest that this should be investigated as a pathophysiological component in NTG patients.

On the Other Hand: Overflow Movements of Infants’ Hands and Legs During Unimanual Object Exploration

PubMed Central

Soska, Kasey C.; Galeon, Margaret A.; Adolph, Karen E.

2011-01-01

Motor overflow is extraneous movement in a limb not involved in a motor action. Typically, overflow is observed in people with neurological impairments and in healthy children and adults during strenuous and attention-demanding tasks. In the current study, we found that young infants produce vast amounts of motor overflow, corroborating claims of symmetry being the default state of the motor system. While manipulating an object with one hand, all 27 of the typically-developing 4.5- to 7.5-month-old infants who we observed displayed overflow movements of the free hand (on 4/5 of unimanual actions). Mirror-image movements of the hands occurred on 1/8 of unimanual actions, and the hands and legs moved in synchrony on 1/3 of unimanual acts. Motor overflow was less frequent when infants were in a sitting posture and when infants watched their acting hand, suggesting that upright posture and visual examination may help to alleviate overflow and break obligatory symmetry in healthy infants. PMID:22487940

Auditory event perception: the source-perception loop for posture in human gait.

PubMed

Pastore, Richard E; Flint, Jesse D; Gaston, Jeremy R; Solomon, Matthew J

2008-01-01

There is a small but growing literature on the perception of natural acoustic events, but few attempts have been made to investigate complex sounds not systematically controlled within a laboratory setting. The present study investigates listeners' ability to make judgments about the posture (upright-stooped) of the walker who generated acoustic stimuli contrasted on each trial. We use a comprehensive three-stage approach to event perception, in which we develop a solid understanding of the source event and its sound properties, as well as the relationships between these two event stages. Developing this understanding helps both to identify the limitations of common statistical procedures and to develop effective new procedures for investigating not only the two information stages above, but also the decision strategies employed by listeners in making source judgments from sound. The result is a comprehensive, ultimately logical, but not necessarily expected picture of both the source-sound-perception loop and the utility of alternative research tools.

Pelvic Morphology, Body Posture and Standing Balance Characteristics of Adolescent Able-Bodied and Idiopathic Scoliosis Girls

PubMed Central

Stylianides, Georgios A.; Dalleau, Georges; Begon, Mickaël; Rivard, Charles-Hilaire; Allard, Paul

2013-01-01

The purpose of this study was to determine how pelvic morphology, body posture, and standing balance variables of scoliotic girls differ from those of able-bodied girls, and to classify neuro-biomechanical variables in terms of a lower number of unobserved variables. Twenty-eight scoliotic and twenty-five non-scoliotic able-bodied girls participated in this study. 3D coordinates of ten anatomic body landmarks were used to describe pelvic morphology and trunk posture using a Flock of Birds system. Standing balance was measured using a force plate to identify the center of pressure (COP), and its anteroposterior (AP) and mediolateral (ML) displacements. A multivariate analysis of variance (MANOVA) was performed to determine differences between the two groups. A factor analysis was used to identify factors that best describe both groups. Statistical differences were identified between the groups for each of the parameter types. While spatial orientation of the pelvis was similar in both groups, five of the eight trunk postural variables of the scoliotic group were significantly different that the able-bodied group. Also, five out of the seven standing balance variables were higher in the scoliotic girls. Approximately 60% of the variation is supported by 4 factors that can be associated with a set of variables; standing balance variables (factor 1), body posture variables (factor 2), and pelvic morphology variables (factors 3 and 4). Pelvic distortion, body posture asymmetry, and standing imbalance are more pronounced in scoliotic girls, when compared to able-bodied girls. These findings may be beneficial when addressing balance and ankle proprioception exercises for the scoliotic population. PMID:23875021

Posture in dentists: Sitting vs. standing positions during dentistry work--An EMG study.

PubMed

Pejcić, Natasa; Jovicić, Milica Đurić; Miljković, Nadica; Popović, Dejan B; Petrović, Vanja

2016-01-01

Adequate working posture is important for overall health. Inappropriate posture may increase fatigue, decrease efficiency, and eventually lead to injuries. The purpose was to examine posture positions used during dentistry work. In order to quantify different posture positions, we recorded muscle activity and positions of body segments. The position (inclination) data of the back was used to assess two postures: sitting and standing during standard dental interventions. During standard interventions, whether sitting or standing, a tilt of less than 20 degrees was most prevalent in the forward and lateral flexion directions. Amplitude of electromyography signals corresponding to the level of muscle activity were higher in sitting compared with the electromyography in standing position for all muscle groups on the left and right side of the body. Significant difference between muscle activity in two working postures was evident in splenius capitis muscle on the left (p = 0.032), on the right side of the body (p = 0.049) and in muscle activity of mastoid muscle on the left side (p = 0.029). These findings show that risk for increased fatigue and possible injures can be reduced by combining the sitting and standing occupational postures.

Comparison of Biodynamic Responses in Standing and Seated Human Bodies

NASA Astrophysics Data System (ADS)

MATSUMOTO, Y.; GRIFFIN, M. J.

2000-12-01

The dynamic responses of the human body in a standing position and in a sitting position have been compared. The apparent mass and transmissibilities to the head, six locations along the spine, and the pelvis were measured with eight male subjects exposed to vertical whole-body vibration. In both postures, the principal resonance in the apparent mass occurred in the range 5-6 Hz, with slightly higher frequencies and lower apparent mass in the standing posture. There was greater transmission of vertical vibration to the pelvis and the lower spine and greater relative motion within the lower spine in the standing posture than in the sitting posture at the principal resonance and at higher frequencies. Transmissibilities from the supporting surface (floor or seat) to the thoracic region had similar magnitudes for both standing and sitting subjects. The lumbar spine has less lordosis and may be more compressed and less flexible in the sitting posture than in the standing posture. This may have reduced the relative motions between lumbar vertebrae and both the supporting vibrating surface and the other vertebrae in the sitting posture. The characteristics of the vibration transmitted to the pelvis may have differed in the two postures due to different transmission paths. Increased forward rotation of the pelvis in the standing posture may have caused the differences in responses of the pelvis and the lower spine that were observed between the two postures.

Care Practice #5: Spontaneous Pushing in Upright or Gravity-Neutral Positions

PubMed Central

DiFranco, Joyce T.; Romano, Amy M.; Keen, Ruth

2007-01-01

This updated edition of Care Practice Paper #5 presents the evidence for the benefits of spontaneous pushing in upright or gravity-neutral positions during labor. Various pushing positions and techniques are described, and the advantages and disadvantages are reviewed. Women are encouraged to push when and how their bodies tell them to and to choose the positions for birth that are the most comfortable. PMID:18566649

Enhancing creativity: Proper body posture meets proper emotion.

PubMed

Hao, Ning; Xue, Hua; Yuan, Huan; Wang, Qing; Runco, Mark A

2017-02-01

This study tested whether compatibility or incompatibility between body posture and emotion was beneficial for creativity. In Study 1, participants were asked to solve the Alternative Uses Task (AUT) problems when performing open or closed body posture in positive or negative emotional state respectively. The results showed that originality of AUT performance was higher in the compatible conditions (i.e., open-positive and closed-negative) than in the incompatible conditions (i.e., closed-positive and open-negative). In Study 2, the compatibility effect was replicated in both the AUT and the Realistic Presented Problem test (i.e., RPP). Moreover, it was revealed that participants exhibited the highest associative flexibility in the open-positive condition, and the highest persistence in the closed-negative condition. These findings indicate that compatibility between body posture and emotion is beneficial for creativity. This may be because when the implicit emotions elicited by body posture match explicit emotions, the effects of emotions on creativity are enhanced, therefore promoting creativity through the flexibility or the persistence pathway respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

The time-delayed inverted pendulum: Implications for human balance control

NASA Astrophysics Data System (ADS)

Milton, John; Cabrera, Juan Luis; Ohira, Toru; Tajima, Shigeru; Tonosaki, Yukinori; Eurich, Christian W.; Campbell, Sue Ann

2009-06-01

The inverted pendulum is frequently used as a starting point for discussions of how human balance is maintained during standing and locomotion. Here we examine three experimental paradigms of time-delayed balance control: (1) mechanical inverted time-delayed pendulum, (2) stick balancing at the fingertip, and (3) human postural sway during quiet standing. Measurements of the transfer function (mechanical stick balancing) and the two-point correlation function (Hurst exponent) for the movements of the fingertip (real stick balancing) and the fluctuations in the center of pressure (postural sway) demonstrate that the upright fixed point is unstable in all three paradigms. These observations imply that the balanced state represents a more complex and bounded time-dependent state than a fixed-point attractor. Although mathematical models indicate that a sufficient condition for instability is for the time delay to make a corrective movement, τn, be greater than a critical delay τc that is proportional to the length of the pendulum, this condition is satisfied only in the case of human stick balancing at the fingertip. Thus it is suggested that a common cause of instability in all three paradigms stems from the difficulty of controlling both the angle of the inverted pendulum and the position of the controller simultaneously using time-delayed feedback. Considerations of the problematic nature of control in the presence of delay and random perturbations ("noise") suggest that neural control for the upright position likely resembles an adaptive-type controller in which the displacement angle is allowed to drift for small displacements with active corrections made only when θ exceeds a threshold. This mechanism draws attention to an overlooked type of passive control that arises from the interplay between retarded variables and noise.

Transmitted cardiovascular pulsations on high resolution esophageal impedance manometry, and their significance in dysphagia.

PubMed

Chaudhry, Naueen A; Zahid, Kamran; Keihanian, Sara; Dai, Yunfeng; Zhang, Qing

2017-11-28

To investigate the behavior of pulsatile pressure zones (PPZ's) as noted on high resolution esophageal impedance manometry (HREIM), and determine their association with dysphagia. Retrospective, single center case control design screening HREIM studies for cases (dysphagia) and controls (no dysphagia). Thoracic radiology studies were reviewed further in cases for (thoracic cardiovascular) thoracic cardiovascular (TCV) structures in esophageal proximity to compare with HREIM findings. Manometric data was collected for number, location, axial length, PPZ pressure and esophageal clearance function (impedance). Among 317 screened patients, 56% cases and 64% controls had PPZ's. Fifty cases had an available thoracic radiology comparison. The distribution of PPZ's in these 50 cases and 59 controls was similar (average 1.4 PPZ/patient). Controls (mean 31.2 ± SD 12 years) were a significantly younger population than cases (mean 67.3 ± SD 14.9 years) with P < 0.0001. The upright posture PPZ pressure was higher in controls (15.7 ± 10.0 mmHg) than cases (10.8 ± 9.7 mmHg). Although statistically significant ( P = 0.005), it was a weak predictor using logistic regression and ROC model (AUC = 0.65). Three dysphagia patients had partial compression from external TCV on radiology (1 aberrant subclavian artery, 2 dilated left atrium). The posture (supine vs upright) with more prominent PPZ's impaired bolus clearance in 9 additional cases by > 20%. Transmitted TCV pulsations observed in HREIM bear no significant impact on swallowing. However, in older adults with dysphagia, evidence of impaired bolus clearance on impedance should be evaluated for external TCV compression. These associations have never been explored previously in literature, and are novel.

Effects of wheelchair cushions and pressure relief maneuvers on ischial interface pressure and blood flow in people with spinal cord injury.

PubMed

Sonenblum, Sharon E; Vonk, Teddie E; Janssen, Thomas W; Sprigle, Stephen H

2014-07-01

To investigate the effectiveness and interactions of 2 methods of pressure ulcer prevention, wheelchair cushions and pressure relief maneuvers, on interface pressure (IP) and blood flow of the buttocks. Within-subject repeated measures. Rehabilitation center. Wheelchair users with a spinal cord injury or disorder (N=17). Participants performed 3 forward leans and 2 sideward leans with different degrees of lean while seated on each of 3 different wheelchair cushions. IP measured with a custom sensor and blood flow measured with laser Doppler flowmetry were collected at the ischial tuberosity. Pressure relief maneuvers had a significant main effect on the ischial IP (P<.001); all maneuvers except for the small frontward lean resulted in a significant reduction in IP compared with upright sitting. Blood flow significantly varied across postures (P<.001) with flow during upright sitting and small forward leans being significantly lower than during the full and intermediate leans in both the forward and sideward directions. The results of the study highlight the importance of positioning wheelchair users in a manner that facilitates in-seat movement. Regardless of the cushion being used, the pressure relief maneuvers resulted in very large reductions in IPs and significant increases in buttock blood flow. Only the small frontward lean was shown to be ineffective in reducing pressure or increasing blood flow. Because these pressure relief maneuvers involved postural changes that can occur during functional activities, these pressure relief maneuvers can become a part of volitional pressure relief and functional weight shifts. Therefore, clinical instruction should cover both as a means to impart sitting behaviors that may lead to better tissue health. Copyright © 2014 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Orthostatic Intolerance in Older Persons: Etiology and Countermeasures

PubMed Central

Goswami, Nandu; Blaber, Andrew P.; Hinghofer-Szalkay, Helmut; Montani, Jean-Pierre

2017-01-01

Orthostatic challenge produced by upright posture may lead to syncope if the cardiovascular system is unable to maintain adequate brain perfusion. This review outlines orthostatic intolerance related to the aging process, long-term bedrest confinement, drugs, and disease. Aging-associated illness or injury due to falls often leads to hospitalization. Older patients spend up to 83% of hospital admission lying in bed and thus the consequences of bedrest confinement such as physiological deconditioning, functional decline, and orthostatic intolerance represent a central challenge in the care of the vulnerable older population. This review examines current scientific knowledge regarding orthostatic intolerance and how it comes about and provides a framework for understanding of (patho-) physiological concepts of cardiovascular (in-) stability in ambulatory and bedrest confined senior citizens as well as in individuals with disease conditions [e.g., orthostatic intolerance in patients with diabetes mellitus, multiple sclerosis, Parkinson's, spinal cord injury (SCI)] or those on multiple medications (polypharmacy). Understanding these aspects, along with cardio-postural interactions, is particularly important as blood pressure destabilization leading to orthostatic intolerance affects 3–4% of the general population, and in 4 out of 10 cases the exact cause remains elusive. Reviewed also are countermeasures to orthostatic intolerance such as exercise, water drinking, mental arithmetic, cognitive training, and respiration training in SCI patients. We speculate that optimally applied countermeasures such as mental challenge maintain sympathetic activity, and improve venous return, stroke volume, and consequently, blood pressure during upright standing. Finally, this paper emphasizes the importance of an active life style in old age and why early re-mobilization following bedrest confinement or bedrest is crucial in preventing orthostatic intolerance, falls and falls-related injuries in older persons. PMID:29163185

Transmitted cardiovascular pulsations on high resolution esophageal impedance manometry, and their significance in dysphagia

PubMed Central

Chaudhry, Naueen A; Zahid, Kamran; Keihanian, Sara; Dai, Yunfeng; Zhang, Qing

2017-01-01

AIM To investigate the behavior of pulsatile pressure zones (PPZ’s) as noted on high resolution esophageal impedance manometry (HREIM), and determine their association with dysphagia. METHODS Retrospective, single center case control design screening HREIM studies for cases (dysphagia) and controls (no dysphagia). Thoracic radiology studies were reviewed further in cases for (thoracic cardiovascular) thoracic cardiovascular (TCV) structures in esophageal proximity to compare with HREIM findings. Manometric data was collected for number, location, axial length, PPZ pressure and esophageal clearance function (impedance). RESULTS Among 317 screened patients, 56% cases and 64% controls had PPZ’s. Fifty cases had an available thoracic radiology comparison. The distribution of PPZ’s in these 50 cases and 59 controls was similar (average 1.4 PPZ/patient). Controls (mean 31.2 ± SD 12 years) were a significantly younger population than cases (mean 67.3 ± SD 14.9 years) with P < 0.0001. The upright posture PPZ pressure was higher in controls (15.7 ± 10.0 mmHg) than cases (10.8 ± 9.7 mmHg). Although statistically significant (P = 0.005), it was a weak predictor using logistic regression and ROC model (AUC = 0.65). Three dysphagia patients had partial compression from external TCV on radiology (1 aberrant subclavian artery, 2 dilated left atrium). The posture (supine vs upright) with more prominent PPZ’s impaired bolus clearance in 9 additional cases by > 20%. CONCLUSION Transmitted TCV pulsations observed in HREIM bear no significant impact on swallowing. However, in older adults with dysphagia, evidence of impaired bolus clearance on impedance should be evaluated for external TCV compression. These associations have never been explored previously in literature, and are novel. PMID:29209125

Human body modeling method to simulate the biodynamic characteristics of spine in vivo with different sitting postures.

PubMed

Dong, Rui-Chun; Guo, Li-Xin

2017-11-01

The aim of this study is to model the computational model of seated whole human body including skeleton, muscle, viscera, ligament, intervertebral disc, and skin to predict effect of the factors (sitting postures, muscle and skin, buttocks, viscera, arms, gravity, and boundary conditions) on the biodynamic characteristics of spine. Two finite element models of seated whole body and a large number of finite element models of different ligamentous motion segments were developed and validated. Static, modal, and transient dynamic analyses were performed. The predicted vertical resonant frequency of seated body model was in the range of vertical natural frequency of 4 to 7 Hz. Muscle, buttocks, viscera, and the boundary conditions of buttocks have influence on the vertical resonant frequency of spine. Muscle played a very important role in biodynamic response of spine. Compared with the vertical posture, the posture of lean forward or backward led to an increase in stress on anterior or lateral posterior of lumbar intervertebral discs. This indicated that keeping correct posture could reduce the injury of vibration on lumbar intervertebral disc under whole-body vibration. The driving posture not only reduced the load of spine but also increased the resonant frequency of spine. Copyright © 2017 John Wiley & Sons, Ltd.

Walking like dinosaurs: chickens with artificial tails provide clues about non-avian theropod locomotion.

PubMed

Grossi, Bruno; Iriarte-Díaz, José; Larach, Omar; Canals, Mauricio; Vásquez, Rodrigo A

2014-01-01

Birds still share many traits with their dinosaur ancestors, making them the best living group to reconstruct certain aspects of non-avian theropod biology. Bipedal, digitigrade locomotion and parasagittal hindlimb movement are some of those inherited traits. Living birds, however, maintain an unusually crouched hindlimb posture and locomotion powered by knee flexion, in contrast to the inferred primitive condition of non-avian theropods: more upright posture and limb movement powered by femur retraction. Such functional differences, which are associated with a gradual, anterior shift of the centre of mass in theropods along the bird line, make the use of extant birds to study non-avian theropod locomotion problematic. Here we show that, by experimentally manipulating the location of the centre of mass in living birds, it is possible to recreate limb posture and kinematics inferred for extinct bipedal dinosaurs. Chickens raised wearing artificial tails, and consequently with more posteriorly located centre of mass, showed a more vertical orientation of the femur during standing and increased femoral displacement during locomotion. Our results support the hypothesis that gradual changes in the location of the centre of mass resulted in more crouched hindlimb postures and a shift from hip-driven to knee-driven limb movements through theropod evolution. This study suggests that, through careful experimental manipulations during the growth phase of ontogeny, extant birds can potentially be used to gain important insights into previously unexplored aspects of bipedal non-avian theropod locomotion.

Regulation of dynamic postural control to attend manual steadiness constraints.

PubMed

Teixeira, Luis Augusto; Coutinho, Joane Figueiredo Serpa; Coelho, Daniel Boari

2018-05-02

In daily living activities, performance of spatially accurate manual movements in upright stance depends on postural stability. In the present investigation, we aimed to evaluate the effect of the required manual steadiness (task constraint) on the regulation of dynamic postural control. A single group of young participants (n=20) were evaluated in the performance of a dual posturo-manual task of balancing on a platform oscillating in sinusoidal translations at 0.4 Hz (low) or 1 Hz (high) frequencies while stabilizing a cylinder on a handheld tray. Manual task constraint was manipulated by comparing the conditions of keeping the cylinder stationary on its flat or round side, corresponding to low and high manual task constraints, respectively. Results showed that in the low oscillation frequency the high manual task constraint led to lower oscillation amplitudes of the head, center of mass, and tray, in addition to higher relative phase values between ankle/hip-shoulder oscillatory rotations and between center of mass/center of pressure-feet oscillations as compared to values observed in the low manual task constraint. Further analyses showed that the high manual task constraint also affected variables related to both postural (increased amplitudes of center of pressure oscillation) and manual (increased amplitude of shoulder rotations) task components in the high oscillation frequency. These results suggest that control of a dynamic posturo-manual task is modulated in distinct parameters to attend the required manual steadiness in a complex and flexible way.

Walking Like Dinosaurs: Chickens with Artificial Tails Provide Clues about Non-Avian Theropod Locomotion

PubMed Central

Grossi, Bruno; Iriarte-Díaz, José; Larach, Omar; Canals, Mauricio; Vásquez, Rodrigo A.

2014-01-01

Birds still share many traits with their dinosaur ancestors, making them the best living group to reconstruct certain aspects of non-avian theropod biology. Bipedal, digitigrade locomotion and parasagittal hindlimb movement are some of those inherited traits. Living birds, however, maintain an unusually crouched hindlimb posture and locomotion powered by knee flexion, in contrast to the inferred primitive condition of non-avian theropods: more upright posture and limb movement powered by femur retraction. Such functional differences, which are associated with a gradual, anterior shift of the centre of mass in theropods along the bird line, make the use of extant birds to study non-avian theropod locomotion problematic. Here we show that, by experimentally manipulating the location of the centre of mass in living birds, it is possible to recreate limb posture and kinematics inferred for extinct bipedal dinosaurs. Chickens raised wearing artificial tails, and consequently with more posteriorly located centre of mass, showed a more vertical orientation of the femur during standing and increased femoral displacement during locomotion. Our results support the hypothesis that gradual changes in the location of the centre of mass resulted in more crouched hindlimb postures and a shift from hip-driven to knee-driven limb movements through theropod evolution. This study suggests that, through careful experimental manipulations during the growth phase of ontogeny, extant birds can potentially be used to gain important insights into previously unexplored aspects of bipedal non-avian theropod locomotion. PMID:24505491