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Sample records for unipedal stance time

  1. Do Ankle Orthoses Improve Ankle Proprioceptive Thresholds or Unipedal Balance in Older Persons with Peripheral Neuropathy?

    PubMed Central

    Son, Jaebum; Ashton-Miller, James A.; Richardson, James K.

    2010-01-01

    Objective To determine whether ankle orthoses that provide medial and lateral support, and have been found to decrease gait variability in older persons with peripheral neuropathy, decrease (improve) frontal plane ankle proprioceptive thresholds or increase unipedal stance time in that same population. Design Observational study in which unipedal stance time was determined with a stopwatch, and frontal plane ankle (inversion and eversion) proprioceptive thresholds were quantified during bipedal stance with and without the ankle orthoses, in 11 older diabetic subjects with peripheral neuropathy (8 men; age 72 ± 7.1 years) using a foot cradle system which presented a series of 100 rotational stimuli. Results The subjects demonstrated no change in combined frontal plane (inversion + eversion) proprioceptive thresholds or unipedal stance time with versus without the orthoses (1.06 ± 0.56 versus 1.13 ± 0.39 degrees, respectively; p = 0.955 and 6.1 ± 6.5 versus 6.2 ± 5.4 seconds, respectively; p = 0.922). Conclusion Ankle orthoses which provide medial-lateral support do not appear to change ankle inversion/eversion proprioceptive thresholds or unipedal stance time in older persons with diabetic peripheral neuropathy. Previously identified improvements in gait variability using orthoses in this population are therefore likely related to an orthotically-induced stiffening of the ankle rather than a change in ankle afferent function. PMID:20407302

  2. Effects of focal ankle joint cooling on unipedal static balance in individuals with and without chronic ankle instability.

    PubMed

    Kim, Kyung-Min; Hart, Joseph M; Saliba, Susan A; Hertel, Jay

    2015-01-01

    Application of cryotherapy over an injured joint has been shown to improve muscle function, yet it is unknown how ankle cryotherapy affects postural control. Our purpose was to determine the effects of a 20-min focal ankle joint cooling on unipedal static stance in individuals with and without chronic ankle instability (CAI). Fifteen young subjects with CAI (9 males, 6 females) and 15 healthy gender-matched controls participated. All subjects underwent two intervention sessions on different days in which they had a 1.5L plastic bag filled with either crushed ice (active treatment) or candy corn (sham) applied to the ankle. Unipedal stance with eyes closed for 10s were assessed with a forceplate before and after each intervention. Center of pressure (COP) data were used to compute 10 specific dependent measures including velocity, area, standard deviation (SD), and percent range of COP excursions, and mean and SD of time-to-boundary (TTB) minima in the anterior-posterior (AP) and mediolateral directions. For each measure a three-way (Group-Intervention-Time) repeated ANOVAs found no significant interactions and main effects involving intervention (all Ps > 0.05). There were group main effects found for mean velocity (F(1,28) = 6.46, P = .017), area (F(1,28) = 12.83, P = .001), and mean of TTB minima in the AP direction (F(1,28) = 5.19, P = .031) indicating that the CAI group demonstrated greater postural instability compared to the healthy group. Postural control of unipedal stance was not significantly altered following focal ankle joint cooling in groups both with and without CAI. Ankle joint cryotherapy was neither beneficial nor harmful to single leg balance. PMID:25468685

  3. Stance time and step width variability have unique contributing impairments in older persons.

    PubMed

    Brach, Jennifer S; Studenski, Stephanie; Perera, Subashan; VanSwearingen, Jessie M; Newman, Anne B

    2008-04-01

    Gait variability may have multiple causes. We hypothesized that central nervous system (CNS) impairments would affect motor control and be manifested as increased stance time and step length variability, while sensory impairments would affect balance and be manifested as increased step width variability. Older adults (mean+/-standard deviation (S.D.) age=79.4+/-4.1, n=558) from the Pittsburgh site of the Cardiovascular Health Study participated. The S.D. across steps was the indicator of gait variability, determined for three gait measures, step length, stance time and step width, using a computerized walkway. Impairment measures included CNS function (modified mini-mental state examination, Trails A and B, Digit Symbol Substitution, finger tapping), sensory function (lower extremity (LE) vibration, vision), strength (grip strength, repeated chair stands), mood, and LE pain. Linear regression models were fit for the three gait variability characteristics using impairment measures as independent variables, adjusted for age, race, gender, and height. Analyses were repeated stratified by gait speed. All measures of CNS impairment were directly related to stance time variability (p<0.01), with increased CNS impairment associated with increased stance time variability. CNS impairments were not related to step length or width variability. Both sensory impairments were inversely related to step width (p<0.01) but not step length or stance time variability. CNS impairments affected stance time variability especially in slow walkers while sensory impairments affected step width variability in fast walkers. Specific patterns of gait variability may imply different underlying causes. Types of gait variability should be specified. Interventions may be targeted at specific types of gait variability. PMID:17632004

  4. Unipedal Postural Balance and Countermovement Jumps After a Warm-up and Plyometric Training Session: A Randomized Controlled Trial.

    PubMed

    Romero-Franco, Natalia; Jiménez-Reyes, Pedro

    2015-11-01

    The purpose of this study was to analyze the immediate effects of a plyometric training protocol on unipedal postural balance and countermovement jumps. In addition, we analyzed the effects of a warm-up on these parameters. Thirty-two amateur male sprinters (24.9 ± 4.1 years; 72.3 ± 10.7 kg; 1.78 ± 0.05 m; 22.6 ± 3.3 kg·m) were randomly sorted into a control group (n = 16) (they did not perform any physical activity) and a plyometric training group (n = 16) (they performed a 15-minute warm-up and a high-intensity plyometric protocol consisting of 10 sets of 15 vertical jumps). Before and after the warm-up, and immediately after and 5 minutes after the plyometric protocol, all athletes indicated the perceived exertion on calf and quad regions on a scale from 0 (no exertion) to 10 (maximum exertion). They also carried out a maximum countermovement jump and a unipedal postural balance test (athletes would remain as still as possible for 15 seconds in a left leg and right leg support stance). Results showed that, in the plyometric group, length and velocity of center-of-pressure movement in right leg support stance increased compared with baseline (p = 0.001 and p = 0.004, respectively) and to the control group (p = 0.035 and p = 0.029, respectively) immediately after the plyometric protocol. In addition, the countermovement jump height decreased right after the plyometric protocol (p < 0.001). The perceived exertion on calf and quad regions increased after the plyometry (p < 0.001). Five minutes later, these parameters remained deteriorated despite a slight recovery (length: p = 0.044; velocity: p = 0.05; countermovement jump height: p < 0.001; local exertion: p < 0.001). Data also showed that countermovement jump height improved after the warm-up (p = 0.021), but unipedal postural balance remained unaltered. As a conclusion, high-intensity plyometric exercises blunt unipedal postural balance and countermovement jump performance. The deterioration lasts at least

  5. Intensive Abdominal Drawing-In Maneuver After Unipedal Postural Stability in Nonathletes With Core Instability

    PubMed Central

    Lee, Nam G.; You, Joshua (Sung) H.; Kim, Tae H.; Choi, Bong S.

    2015-01-01

    Context: The exact neuromechanical nature and relative contribution of the abdominal drawing-in maneuver (ADIM) to postural instability warrants further investigation in uninjured and injured populations. Objective: To determine the effects of the ADIM on static core and unipedal postural stability in nonathletes with core instability. Design: Controlled laboratory study. Setting: University research laboratory. Patients or Other Participants: A total of 19 nonathletes (4 women: age = 22.3 ± 1.3 years, height = 164.0 ± 1.7 cm, mass = 56.0 ± 4.6 kg; 15 men: age = 24.6 ± 2.8 years, height = 172.6 ± 4.7 cm, mass = 66.8 ± 7.6 kg) with core instability. Intervention(s): Participants received ADIM training with visual feedback 20 minutes each day for 7 days each week over a 2-week period. Main Outcome Measures(s): Core instability was determined using a prone formal test and measured by a pressure biofeedback unit. Unipedal postural stability was determined by measuring the center-of-pressure sway and associated changes in the abdominal muscle-thickness ratios. Electromyographic activity was measured concurrently in the external oblique, erector spinae, gluteus medius, vastus medialis oblique, tibialis anterior, and medial gastrocnemius muscles. Results: All participants initially were unable to complete the formal test. However, after the 2-week ADIM training period, all participants were able to reduce the pressure biofeedback unit by a range of 4 to 10 mm Hg from an initial 70 mm Hg and maintain it at 60 to 66 mm Hg with minimal activation of the external oblique (t18 = 3.691, P = .002) and erector spinae (t18 = 2.823, P = .01) muscles. Monitoring of the pressure biofeedback unit and other muscle activations confirmed that the correct muscle contraction defining the ADIM was accomplished. This core stabilization was well maintained in the unipedal-stance position, as evidenced by a decrease in the center-of-pressure sway measures (t18 range, 3.953–5.775, P

  6. Lower extremity muscle activation onset times during the transition from double-leg stance to single-leg stance in anterior cruciate ligament injured subjects.

    PubMed

    Dingenen, Bart; Janssens, Luc; Luyckx, Thomas; Claes, Steven; Bellemans, Johan; Staes, Filip F

    2015-12-01

    The goal of this study was to evaluate muscle activation onset times (MAOT) of both legs during a transition task from double-leg stance (DLS) to single-leg stance (SLS) in anterior cruciate ligament injured (ACLI) (n=15) and non-injured control subjects (n=15) with eyes open and eyes closed. Significantly delayed MAOT were found in the ACLI group compared to the control group for vastus lateralis, vastus medialis obliquus, hamstrings medial, hamstrings lateral, tibialis anterior, peroneus longus and gastrocnemius in both vision conditions, for gluteus maximus and gluteus medius with eyes open and for tensor fascia latae with eyes closed. Within the ACLI group, delayed MAOT of tibialis anterior with eyes open and gastrocnemius with eyes closed were found in the injured leg compared to the non-injured leg. All other muscles were not significantly different between legs. In conclusion, the ACLI group showed delayed MAOT not only around the knee, but also at the hip and ankle muscles compared to the non-injured control group. No differences between both legs of the ACLI group were found, except for tibialis anterior and gastrocnemius. These findings indirectly support including central nervous system re-education training to target the underlying mechanisms of these altered MAOT after ACL injury. PMID:26409102

  7. Postural Performance and Strategy in the Unipedal Stance of Soccer Players at Different Levels of Competition

    PubMed Central

    Paillard, Thierry; Noé, Frédéric; Rivière, Terence; Marion, Vincent; Montoya, Richard; Dupui, Philippe

    2006-01-01

    Context: Sport training enhances the ability to use somatosensory and otolithic information, which improves postural capabilities. Postural changes are different according to the sport practiced, but few authors have analyzed subjects' postural performances to discriminate the expertise level among highly skilled athletes within a specific discipline. Objective: To compare the postural performance and the postural strategy between soccer players at different levels of competition (national and regional). Design: Repeated measures with 1 between-groups factor (level of competition: national or regional) and 1 within-groups factor (vision: eyes open or eyes closed). Dependent variables were center-of-pressure surface area and velocity; total spectral energy; and percentage of low-, medium-, and high-frequency band. Setting: Sports performance laboratory. Patients or Other Participants: Fifteen national male soccer players (age = 24 ± 3 years, height = 179 ± 5 cm, mass = 72 ± 3 kg) and 15 regional male soccer players (age = 23 ± 3 years, height = 174 ± 4 cm, mass = 68 ± 5 kg) participated in the study. Intervention(s): The subjects performed posturographic tests with eyes open and closed. Main Outcome Measure(s): While subjects performed static and dynamic posturographic tests, we measured the center of foot pressure on a force platform. Spatiotemporal center-of-pressure measurements were used to evaluate the postural performance, and a frequency analysis of the center-of-pressure excursions (fast Fourier transform) was conducted to estimate the postural strategy. Results: Within a laboratory task, national soccer players produced better postural performances than regional players and had a different postural strategy. The national players were more stable than the regional players and used proprioception and vision information differently. Conclusions: In the test conditions specific to playing soccer, level of playing experience influenced postural control performance measures and strategies. PMID:16791302

  8. 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. PMID:24954557

  9. Use of Stance Time Variability for Predicting Mobility Disability in Community-Dwelling Older Persons: A Prospective Study

    PubMed Central

    Brach, Jennifer S.; Wert, David; VanSwearingen, Jessie M.; Newman, Anne B.; Studenski, Stephanie A.

    2012-01-01

    Background and Purpose Mobility disability is a serious and frequent adverse health outcome associated with aging. Early identification of individuals at risk for mobility disability is important if interventions to prevent disability are to be instituted. The objectives of this prospective study were to: 1) determine the magnitude of stance time variability (STV) that discriminates individuals who currently have mobility disability (prevalent mobility disability) and 2) determine the magnitude of STV that predicts a new onset of mobility disability at one year (incident mobility disability). Methods 552 community-dwelling older adults were evaluated as part of the Cardiovascular Health Study, a longitudinal cohort study. Stance time, in milliseconds (ms), was determined from 2 passes on a 4-meter computerized walkway at self-selected walking speed, and STV was defined as the standard deviation (SD) from approximately 12 individual steps. Mobility disability was defined as self-reported difficulty walking a half mile. Receiver operating characteristic (ROC) curves were plotted to determine an optimal cutoff value for stance time variability for prevalent and incident mobility disability, and the area under the ROC curve was computed. Results The optimal cut-off score for STV (maximizing sensitivity and specificity) for prevalent mobility disability was 0.037 sec(sensitivity = 65%, specificity = 65%, AUC = 0.70) and for incident 1 year mobility disability was 0.034 sec(sensitivity = 61%, specificity = 60%, AUC = 0.65). The use of likelihood ratios demonstrated a gradient of risk across values of STV, with mobility risk increasing as values of STV increased. Discussion and Conclusion Values of STV may be useful in identifying older adults with mobility disability and at risk for future disability. We recommend the more conservative estimate for identifying risk, STV=0.034 s, which maximizes the sensitivity and minimizes false negatives. The relatively modest values

  10. Intraarticular injection of hyaluronan prevents cartilage erosion, periarticular fibrosis and mechanical allodynia and normalizes stance time in murine knee osteoarthritis

    PubMed Central

    2011-01-01

    Introduction Intraarticular hyaluronan (HA) is used clinically for symptomatic relief in patients with knee osteoarthritis (OA); however, the mechanism of action is unclear. In this study, we examined the effects of a single injection of HA on joint tissue pathology, mechanical allodynia and gait changes (measured by stride times) in a murine model of OA. Methods OA was induced in the right knee joint (stifle) of 12-week-old male C57BL/6 mice by transforming growth factor β1 (TGFβ1) injection and treadmill running for 14 days. Gait parameters were quantified by using TreadScan, mechanical allodynia was evaluated with von Frey filaments, and joint pathology was evaluated by scoring of macroscopic images for both cartilage erosion and periarticular fibrosis. HA or saline control was injected 1 day after TGFβ1 injection but before the start of treadmill running. Results OA development in this model was accompanied by significant (P < 0.01) enhancement of the stance and propulsion times of affected legs. HA injection (but not saline injection) blocked all gait changes and also protected joints from femoral cartilage erosion as well as tibial and femoral tissue fibrosis. Both HA injection and saline injection attenuated acute allodynia, but the HA effect was more pronounced and prolonged than the saline injection. Conclusions We conclude that videographic gait analysis is an objective, sensitive and reproducible means of monitoring joint pathology in experimental murine OA, since stance time appears to correlate directly with OA severity. A single injection of HA prevents acute and prolonged gait changes and ameliorates the cartilage erosion and periarticular fibrosis normally seen in this model. We speculate that the capacity of HA to prevent cartilage erosion results from its normalization of joint biomechanics and its inhibitory effects on periarticular cells, which are involved in tissue hyperplasia and fibrosis. This effect of exogenous HA appears to mimic the

  11. Time-dependent influence of sensorimotor set on automatic responses in perturbed stance

    NASA Technical Reports Server (NTRS)

    Chong, R. K.; Horak, F. B.; Woollacott, M. H.; Peterson, B. W. (Principal Investigator)

    1999-01-01

    These experiments tested the hypothesis that the ability to change sensorimotor set quickly for automatic responses depends on the time interval between successive surface perturbations. Sensorimotor set refers to the influence of prior experience or context on the state of the sensorimotor system. Sensorimotor set for postural responses was influenced by first giving subjects a block of identical backward translations of the support surface, causing forward sway and automatic gastrocnemius responses. The ability to change set quickly was inferred by measuring the suppression of the stretched antagonist gastrocnemius responses to toes-up rotations causing backward sway, following the translations. Responses were examined under short (10-14 s) and long (19-24 s) inter-trial intervals in young healthy subjects. The results showed that subjects in the long-interval group changed set immediately by suppressing gastrocnemius to 51% of translation responses within the first rotation and continued to suppress them over succeeding rotations. In contrast, subjects in the short-interval group did not change set immediately, but required two or more rotations to suppress gastrocnemius responses. By the last rotation, the short-interval group suppressed gastrocnemius responses to 33%, similar to the long-interval group of 29%. Associated surface plantarflexor torque resulting from these responses showed similar results. When rotation and translation perturbations alternated, however, the short-interval group was not able to suppress gastrocnemius responses to rotations as much as the long-interval group, although they did suppress more than in the first rotation trial after a series of translations. Set for automatic responses appears to linger, from one trial to the next. Specifically, sensorimotor set is more difficult to change when surface perturbations are given in close succession, making it appear as if set has become progressively stronger. A strong set does not mean

  12. Effects of changing stance conditions on anticipatory postural adjustment and reaction time to voluntary arm movement in humans.

    PubMed

    Dietz, V; Kowalewski, R; Nakazawa, K; Colombo, G

    2000-04-15

    1. The effect on reaction time (RT) and anticipatory postural adjustment (APA) of unexpectedly changing stance conditions was studied using a push or pull arm movement task. The aim was to evaluate the modifiability of RT and APA by an external perturbation associated with an automatic compensatory reaction. 2. Subjects standing on a moveable platform were asked to push or pull a rigid handle as quickly and as strongly as possible in response to the 'go-signal', a visual signal from a green or red light-emitting diode. Forward and backward translations of the platform were randomly induced at four time intervals after the go-signal. In some experiments to detect unspecific arousal there were no platform translations but an acoustic signal was given before the go-signal. Surface electromyographic activity (EMG) of upper arm and lower leg muscles was analysed. 3. During the push task both RT and the duration of APA (onset of APA till the force signal indicating hand action) were shorter during backward than during forward translation. During the pull task the effect of platform translations was the reverse. The delay between go-signal and onset of APA remained constant. Consequently, RT and APA became shorter when the platform was translated in the same direction as that in which the upper body was displaced by the push or pull movement, and longer when it was translated in the opposite direction. The effects were maximal when translations were induced 250 ms after the go-signal, but a difference was detected up to 375 ms. 4. Furthermore, with forward and backward platform translations RT was shorter when the translations were induced early rather than late after the go-signal. This was associated with a shortening of the delay between the go-signal and onset of APA, while APA duration remained constant. The shortened RT was in the range of that obtained when an acoustic signal was given just before the go-signal. 5. It is concluded that (i) both the RT and the

  13. Soccer players have a better standing balance in nondominant one-legged stance

    PubMed Central

    Barone, Rosario; Macaluso, Filippo; Traina, Marcello; Leonardi, Vincenza; Farina, Felicia; Di Felice, Valentina

    2011-01-01

    The purpose of this study was to analyze the differences in standing balance during dominant and nondominant one-legged stance among athletes of different sports and sedentary subjects. The right-footed subjects of four groups (sedentary, n = 20; soccer, n = 20; basketball, n = 20; windsurfer n = 20) underwent 5-sec unipedal (left and right foot) stabilometric analysis with open eyes and closed eyes to measure center of pressure (COP) sway path and COP velocity (mean value, anteroposterior, and laterolateral in millimeters per second). The soccer group showed better standing balance on the left leg than the sedentary group (P < 0.05). No other significant differences were observed within and amongst groups. The soccer players have a better standing balance on the nondominant leg because of soccer activity. PMID:24198563

  14. "The Road to Freedom": How One Salvadoran Youth Takes an Agentive Stance to Narrate the Self across Time and Space

    ERIC Educational Resources Information Center

    McGinnis, Theresa Ann; Garcia, Andrea

    2012-01-01

    In this article, we use narrative theory to analyze and discuss how one Salvadoran youth, Thomas, constructed three different yet overlapping narratives, including a digital story, on his family's movement across borders. We describe how each telling of his narratives is situated in time and space, where Thomas reveals his understandings of…

  15. 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

    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. PMID:26949920

  16. 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

  17. Feedforward ankle strategy of balance during quiet stance in adults

    PubMed Central

    Gatev, Plamen; Thomas, Sherry; Kepple, Thomas; Hallett, Mark

    1999-01-01

    We studied quiet stance investigating strategies for maintaining balance. Normal subjects stood with natural stance and with feet together, with eyes open or closed. Kinematic, kinetic and EMG data were evaluated and cross-correlated.Cross-correlation analysis revealed a high, positive, zero-phased correlation between anteroposterior motions of the centre of gravity (COG) and centre of pressure (COP), head and COG, and between linear motions of the shoulder and knee in both sagittal and frontal planes. There was a moderate, negative, zero-phased correlation between the anteroposterior motion of COP and ankle angular motion.Narrow stance width increased ankle angular motion, hip angular motion, mediolateral sway of the COG, and the correlation between linear motions of the shoulder and knee in the frontal plane. Correlations between COG and COP and linear motions of the shoulder and knee in the sagittal plane were decreased. The correlation between the hip angular sway in the sagittal and frontal planes was dependent on interaction between support and vision.Low, significant positive correlations with time lags of the maximum of cross-correlation of 250-300 ms were found between the EMG activity of the lateral gastrocnemius muscle and anteroposterior motions of the COG and COP during normal stance. Narrow stance width decreased both correlations whereas absence of vision increased the correlation with COP.Ankle mechanisms dominate during normal stance especially in the sagittal plane. Narrow stance width decreased the role of the ankle and increased the role of hip mechanisms in the sagittal plane, while in the frontal plane both increased.The modulation pattern of the lateral gastrocnemius muscle suggests a central program of control of the ankle joint stiffness working to predict the loading pattern. PMID:9882761

  18. Statistical analysis of quiet stance sway in 2-D

    PubMed Central

    DiZio, Paul; Lackner, James R.

    2014-01-01

    Subjects exposed to a rotating environment that perturbs their postural sway show adaptive changes in their voluntary spatially directed postural motion to restore accurate movement paths but do not exhibit any obvious learning during passive stance. We have found, however, that a variable known to characterize the degree of stochasticity in quiet stance can also reveal subtle learning phenomena in passive stance. We extended Chow and Collins (Phys Rev E 52(1):909–912, 1995) one-dimensional pinned-polymer model (PPM) to two dimensions (2-D) and then evaluated the model’s ability to make analytical predictions for 2-D quiet stance. To test the model, we tracked center of mass and centers of foot pressures, and compared and contrasted stance sway for the anterior–posterior versus medio-lateral directions before, during, and after exposure to rotation at 10 rpm. Sway of the body during rotation generated Coriolis forces that acted perpendicular to the direction of sway. We found significant adaptive changes for three characteristic features of the mean square displacement (MSD) function: the exponent of the power law defined at short time scales, the proportionality constant of the power law, and the saturation plateau value defined at longer time scales. The exponent of the power law of MSD at a short time scale lies within the bounds predicted by the 2-D PPM. The change in MSD during exposure to rotation also had a power-law exponent in the range predicted by the theoretical model. We discuss the Coriolis force paradigm for studying postural and movement control and the applicability of the PPM model in 2-D for studying postural adaptation. PMID:24477760

  19. Statistical analysis of quiet stance sway in 2-D.

    PubMed

    Bakshi, Avijit; DiZio, Paul; Lackner, James R

    2014-04-01

    Subjects exposed to a rotating environment that perturbs their postural sway show adaptive changes in their voluntary spatially directed postural motion to restore accurate movement paths but do not exhibit any obvious learning during passive stance. We have found, however, that a variable known to characterize the degree of stochasticity in quiet stance can also reveal subtle learning phenomena in passive stance. We extended Chow and Collins (Phys Rev E 52(1):909-912, 1995) one-dimensional pinned-polymer model (PPM) to two dimensions (2-D) and then evaluated the model's ability to make analytical predictions for 2-D quiet stance. To test the model, we tracked center of mass and centers of foot pressures, and compared and contrasted stance sway for the anterior-posterior versus medio-lateral directions before, during, and after exposure to rotation at 10 rpm. Sway of the body during rotation generated Coriolis forces that acted perpendicular to the direction of sway. We found significant adaptive changes for three characteristic features of the mean square displacement (MSD) function: the exponent of the power law defined at short time scales, the proportionality constant of the power law, and the saturation plateau value defined at longer time scales. The exponent of the power law of MSD at a short time scale lies within the bounds predicted by the 2-D PPM. The change in MSD during exposure to rotation also had a power-law exponent in the range predicted by the theoretical model. We discuss the Coriolis force paradigm for studying postural and movement control and the applicability of the PPM model in 2-D for studying postural adaptation. PMID:24477760

  20. Stance-Taking and Stance-Support in Students' Online Forum Discussion

    ERIC Educational Resources Information Center

    Chandrasegaran, Antonia; Kong, Kah Mun Clara

    2006-01-01

    Stance-taking and stance-support are two discourse behaviours that define the expository/argumentative essay genre, the mastery of which is the key to academic success in higher education. The aim of this study is to discover the extent to which a group of high school students from a non-native English-speaking background are capable of engaging…

  1. Using a Stance Corpus to Learn about Effective Authorial Stance-Taking: A Textlinguistic Approach

    ERIC Educational Resources Information Center

    Chang, Peichin

    2012-01-01

    Presenting a persuasive authorial stance is a major challenge for second language (L2) writers in writing academic research. Failure to present an effective authorial stance often results in poor evaluation, which compromises a writer's research potential. This study proposes a "textlinguistic" approach to advanced academic writing to complement a…

  2. Stability of a double inverted pendulum model during human quiet stance with continuous delay feedback control.

    PubMed

    Suzuki, Yasuyuki; Nomura, Taishin; Morasso, Pietro

    2011-01-01

    Recent debate about neural mechanisms for stabilizing human upright quiet stance focuses on whether the active and time delay neural feedback control generating muscle torque is continuous or intermittent. A single inverted pendulum controlled by the active torque actuating the ankle joint has often been used for the debate on the presumption of well-known ankle strategy hypothesis claiming that the upright quiet stance can be stabilized mostly by the ankle torque. However, detailed measurements are showing that the hip joint angle exhibits amount of fluctuations comparable with the ankle joint angle during natural postural sway. Here we analyze a double inverted pendulum model during human quiet stance to demonstrate that the conventional proportional and derivative delay feedback control, i.e., the continuous delay PD control with gains in the physiologically plausible range is far from adequate as the neural mechanism for stabilizing human upright quiet stance. PMID:22256061

  3. Narrative Stance in the Douglass Autobiographies.

    ERIC Educational Resources Information Center

    Davidson, Phebe

    To consider Frederick Douglass as an autobiographer, it is useful to examine each of his three autobiographical texts with a view to drawing some conclusion about their relation to one another, and about the relation of the author to each one. It seems likely that the shifting of Douglass' narrative stance is an index of his intellectual…

  4. Authorial Stance in Thai Students' Doctoral Dissertation

    ERIC Educational Resources Information Center

    Getkham, Kunyarut

    2016-01-01

    This study investigates how linguistic devices are used to convey authorial stance in 36 Introduction sections and 36 Discussion sections of doctoral dissertations written in English by Thai students graduated in language education from different universities in the United States during the period 2008 to 2013. It also compares the use of…

  5. Five Stances That Have Got to Go

    ERIC Educational Resources Information Center

    Zeigler, Earle F.

    1973-01-01

    The five stances in physical education that have to go are as follows: a) the shotgun approach'' to professional preparation; b) the athletics uber alles approach''; c) the women are all right in their place approach''; d) the body of knowledge approach'' and the password is treadmill' approach.''

  6. Effects of stance angle on postural stability and performance with national-standard air pistol competitors.

    PubMed

    Hawkins, Richard Nelson

    2013-01-01

    The effects of stance angle on postural stability and shooting processes were studied using eight national-standard male air-pistol shooters. Each shooter performed 60 shots each in four stance angles (0°, 15°, 30° and 45° from the line of fire). Postural stability was determined by measuring change in centre of pressure with a dual-force platform system assessing centre-of-pressure (COP) excursion (average difference of the centre of pressure from the mean) and COP speed (total COP path divided by time). Shooting process measures were determined by using a NOPTEL ST-2000 optoelectronic system. Score was assessed with a Sius Ascor S10 electronic scoring system. The results revealed no significant difference among the various stance angles; COP excursion or COP speed, p>0.05. Results indicated a significant stance angle effect with the shooting process measure, hit fine (percentage of hold within an area the size of the 10-ring when centred over the actual shot; p = 0.025) and the shooting performance measure adjusted score (raw score adjusted for true zero; p=0.008). Moreover, best overall performance was with a stance angle of 15°. These findings suggest that stance angle may affect pistol stability and performance in air-pistol athletes. PMID:24050465

  7. Reviewer Stances and Writer Perceptions in EFL Peer Review Training

    ERIC Educational Resources Information Center

    Min, Hui-Tzu

    2008-01-01

    Research has shown that reviewers' stances can impact the efficacy of peer response/review and subsequent revision. The purpose of this classroom-based study was to compare reviewer stances and writer perceptions of/and attitudes toward these stances prior to and after peer review training in an EFL writing class. Eighteen intermediate EFL writers…

  8. A study on effects of and stance over tuition fees

    PubMed Central

    Karay, Yassin; Matthes, Jan

    2016-01-01

    Aim: Regarding tuition fees (that in Germany already have been abrogated) putative drawbacks like prolonged study duration have been suspected while benefits are not clearly proven. We investigated whether tuition fees (500 Euro per semester) affected the course of studies of Cologne medical students and asked for students’ stance over tuition fees. Methods: Of 1,324 students we analyzed the rate of those passing their first medical exam (“Physikum”) within minimum time and students’ discontinuation rate, respectively. Regression analysis tested for putative influences of tuition fees and demographic factors. In an additional online survey 400 students answered questions regarding the load by and their stance over tuition fees. Results: We find that fees did not affect rate of Cologne students passing their first medical exam within minimum time or students’ discontinuation rate. According to the online survey, at times of tuition fees significantly more students did not attend courses as scheduled. Time spent on earning money was significantly increased. 51% of students who had to pay tuition fees and 71% of those who never had to stated tuition fees to be not justified. More than two thirds of students did not recognize any lasting benefit from tuition fees. Conclusion: Tuition fees did not affect discontinuation rate or study duration of Cologne medical students. However, they obviously influenced the study course due to an increased need to pursue a sideline. Cologne medical students rather refused tuition fees and did not recognize their advantages in terms of enhanced quality of studies. PMID:26958654

  9. Interpreting the Need for Initial Support to Perform Tandem Stance Tests of Balance

    PubMed Central

    Brach, Jennifer S.; Perera, Subashan; Wert, David M.; VanSwearingen, Jessie M.; Studenski, Stephanie A.

    2012-01-01

    Background Geriatric rehabilitation reimbursement increasingly requires documented deficits on standardized measures. Tandem stance performance can characterize balance, but protocols are not standardized. Objective The purpose of this study was to explore the impact of: (1) initial support to stabilize in position and (2) maximum hold time on tandem stance tests of balance in older adults. Design A cross-sectional secondary analysis of observational cohort data was conducted. Methods One hundred seventeen community-dwelling older adults (71% female, 12% black) were assigned to 1 of 3 groups based on the need for initial support to perform tandem stance: (1) unable even with support, (2) able only with support, and (3) able without support. The able without support group was further stratified on hold time in seconds: (1) <10 (low), (2) 10 to 29, (medium), and (3) 30 (high). Groups were compared on primary outcomes (gait speed, Timed “Up & Go” Test performance, and balance confidence) using analysis of variance. Results Twelve participants were unable to perform tandem stance, 14 performed tandem stance only with support, and 91 performed tandem stance without support. Compared with the able without support group, the able with support group had statistically or clinically worse performance and balance confidence. No significant differences were found between the able with support group and the unable even with support group on these same measures. Extending the hold time to 30 seconds in a protocol without initial support eliminated ceiling effects for 16% of the study sample. Limitations Small comparison groups, use of a secondary analysis, and lack of generalizability of results were limitations of the study. Conclusions Requiring initial support to stabilize in tandem stance appears to reflect meaningful deficits in balance-related mobility measures, so failing to consider support may inflate balance estimates and confound hold time comparisons

  10. Stance, Navigation, and Reader Response in Expository Hypertext

    ERIC Educational Resources Information Center

    McEneaney, John E.; Li, Ledong; Allen, Kris; Guzniczak, Lizabeth

    2009-01-01

    This article reports on two studies investigating reader stance, navigation, and response in expository hypertext. Subjects in the studies included 69 and 147 adult readers prompted to adopt either an efferent or aesthetic stance when reading a 36-node expository hypertext. Reading was followed by recall and essay writing tasks. Results of the…

  11. Soleus H-reflex modulation during receive stance in badminton players in the receive stance

    PubMed Central

    Masu, Yujiro; Muramatsu, Ken

    2015-01-01

    [Purpose] This study aimed to clarify the characteristics of motor neuron excitability by examining the soleus H-reflex in the ready position adopted immediately before making a return during badminton games. [Subjects] Sixteen individuals with (badminton group) and 16 without (control group) experience of playing badminton were studied. [Methods] Each subject was instructed to take up various stances for returning a shuttlecock to measure the H- and M-waves in the soleus. [Results] The H-wave was significantly decreased when gripping a racket was held in the dominant hand than compared to just standing in the badminton group. In contrast, in the control group, no significant differences were observed between when standing and the other stances. [Conclusion] Based on these results, the excitability of spinal motor neurons may have been reduced (H-wave suppression) by badminton training to increase the instantaneous force (power training). PMID:25642054

  12. Soleus H-reflex modulation during receive stance in badminton players in the receive stance.

    PubMed

    Masu, Yujiro; Muramatsu, Ken

    2015-01-01

    [Purpose] This study aimed to clarify the characteristics of motor neuron excitability by examining the soleus H-reflex in the ready position adopted immediately before making a return during badminton games. [Subjects] Sixteen individuals with (badminton group) and 16 without (control group) experience of playing badminton were studied. [Methods] Each subject was instructed to take up various stances for returning a shuttlecock to measure the H- and M-waves in the soleus. [Results] The H-wave was significantly decreased when gripping a racket was held in the dominant hand than compared to just standing in the badminton group. In contrast, in the control group, no significant differences were observed between when standing and the other stances. [Conclusion] Based on these results, the excitability of spinal motor neurons may have been reduced (H-wave suppression) by badminton training to increase the instantaneous force (power training). PMID:25642054

  13. Effect of stance width on multidirectional postural responses

    NASA Technical Reports Server (NTRS)

    Henry, S. M.; Fung, J.; Horak, F. B.; Peterson, B. W. (Principal Investigator)

    2001-01-01

    The effect of stance width on postural responses to 12 different directions of surface translations was examined. Postural responses were characterized by recording 11 lower limb and trunk muscles, body kinematics, and forces exerted under each foot of 7 healthy subjects while they were subjected to horizontal surface translations in 12 different, randomly presented directions. A quasi-static approach of force analysis was done, examining force integrals in three different epochs (background, passive, and active periods). The latency and amplitude of muscle responses were quantified for each direction, and muscle tuning curves were used to determine the spatial activation patterns for each muscle. The results demonstrate that the horizontal force constraint exerted at the ground was lessened in the wide, compared with narrow, stance for humans, a similar finding to that reported by Macpherson for cats. Despite more trunk displacement in narrow stance, there were no significant changes in body center of mass (CoM) displacement due to large changes in center of pressure (CoP), especially in response to lateral translations. Electromyographic (EMG) magnitude decreased for all directions in wide stance, particularly for the more proximal muscles, whereas latencies remained the same from narrow to wide stance. Equilibrium control in narrow stance was more of an active postural strategy that included regulating the loading/unloading of the limbs and the direction of horizontal force vectors. In wide stance, equilibrium control relied more on an increase in passive stiffness resulting from changes in limb geometry. The selective latency modulation of the proximal muscles with translation direction suggests that the trunk was being actively controlled in all directions. The similar EMG latencies for both narrow and wide stance, with modulation of only the muscle activation magnitude as stance width changed, suggest that the same postural synergy was only slightly modified

  14. Postural Stability During Single-Leg Stance: A Preliminary Evaluation of Noncontact Lower Extremity Injury Risk.

    PubMed

    Dingenen, Bart; Malfait, Bart; Nijs, Stefaan; Peers, Koen H E; Vereecken, Styn; Verschueren, Sabine M P; Janssens, Luc; Staes, Filip F

    2016-08-01

    Study Design Controlled laboratory study with a prospective cohort design. Background Postural stability deficits during single-leg stance have been reported in persons with anterior cruciate ligament (ACL) injury, ACL reconstruction, and chronic ankle instability. It remains unclear whether impaired postural stability is a consequence or cause of these injuries. Objectives To prospectively investigate whether postural stability deficits during single-leg stance predict noncontact lower extremity injuries. Methods Fifty injury-free female athletes performed a transition task from double-leg stance to single-leg stance with eyes closed. Center-of-pressure displacement, the main outcome variable, was measured during the first 3 seconds after the time to a new stability point was reached during single-leg stance. Noncontact lower extremity injuries were recorded at a 1-year follow-up. Results Six participants sustained a noncontact ACL injury or ankle sprain. Center-of-pressure displacement during the first 3 seconds after the time to a new stability point was significantly increased in the injured (P = .030) and noninjured legs (P = .009) of the injured group compared to the respective matched legs of the noninjured group. The area under the receiver operating characteristic curve (AUC) analysis revealed significant discriminative accuracy between groups for the center-of-pressure displacement during the first 3 seconds after the time to a new stability point of the injured (AUC = 0.814, P = .015) and noninjured legs (AUC = 0.897, P = .004) of the injured group compared to the matched legs of the noninjured group. Conclusion This preliminary study suggests that postural stability measurements during the single-leg stance phase of the double- to single-leg stance transition task may be a useful predictor of increased risk of noncontact lower extremity injury. Further research is indicated. Level of Evidence Prognosis, level 4. J Orthop Sports PhysTher 2016

  15. Body stability and muscle and motor cortex activity during walking with wide stance.

    PubMed

    Farrell, Brad J; Bulgakova, Margarita A; Beloozerova, Irina N; Sirota, Mikhail G; Prilutsky, Boris I

    2014-08-01

    Biomechanical and neural mechanisms of balance control during walking are still poorly understood. In this study, we examined the body dynamic stability, activity of limb muscles, and activity of motor cortex neurons [primarily pyramidal tract neurons (PTNs)] in the cat during unconstrained walking and walking with a wide base of support (wide-stance walking). By recording three-dimensional full-body kinematics we found for the first time that during unconstrained walking the cat is dynamically unstable in the forward direction during stride phases when only two diagonal limbs support the body. In contrast to standing, an increased lateral between-paw distance during walking dramatically decreased the cat's body dynamic stability in double-support phases and prompted the cat to spend more time in three-legged support phases. Muscles contributing to abduction-adduction actions had higher activity during stance, while flexor muscles had higher activity during swing of wide-stance walking. The overwhelming majority of neurons in layer V of the motor cortex, 82% and 83% in the forelimb and hindlimb representation areas, respectively, were active differently during wide-stance walking compared with unconstrained condition, most often by having a different depth of stride-related frequency modulation along with a different mean discharge rate and/or preferred activity phase. Upon transition from unconstrained to wide-stance walking, proximal limb-related neuronal groups subtly but statistically significantly shifted their activity toward the swing phase, the stride phase where most of body instability occurs during this task. The data suggest that the motor cortex participates in maintenance of body dynamic stability during locomotion. PMID:24790167

  16. Body stability and muscle and motor cortex activity during walking with wide stance

    PubMed Central

    Farrell, Brad J.; Bulgakova, Margarita A.; Beloozerova, Irina N.; Sirota, Mikhail G.

    2014-01-01

    Biomechanical and neural mechanisms of balance control during walking are still poorly understood. In this study, we examined the body dynamic stability, activity of limb muscles, and activity of motor cortex neurons [primarily pyramidal tract neurons (PTNs)] in the cat during unconstrained walking and walking with a wide base of support (wide-stance walking). By recording three-dimensional full-body kinematics we found for the first time that during unconstrained walking the cat is dynamically unstable in the forward direction during stride phases when only two diagonal limbs support the body. In contrast to standing, an increased lateral between-paw distance during walking dramatically decreased the cat's body dynamic stability in double-support phases and prompted the cat to spend more time in three-legged support phases. Muscles contributing to abduction-adduction actions had higher activity during stance, while flexor muscles had higher activity during swing of wide-stance walking. The overwhelming majority of neurons in layer V of the motor cortex, 82% and 83% in the forelimb and hindlimb representation areas, respectively, were active differently during wide-stance walking compared with unconstrained condition, most often by having a different depth of stride-related frequency modulation along with a different mean discharge rate and/or preferred activity phase. Upon transition from unconstrained to wide-stance walking, proximal limb-related neuronal groups subtly but statistically significantly shifted their activity toward the swing phase, the stride phase where most of body instability occurs during this task. The data suggest that the motor cortex participates in maintenance of body dynamic stability during locomotion. PMID:24790167

  17. Modeling sensorimotor control of human upright stance.

    PubMed

    Mergner, Thomas

    2007-01-01

    We model human postural control of upright stance during external disturbances and voluntary lean. Our focus is on how data from various sensors are combined to estimate these disturbances. Whereas most current engineering models of multisensory estimation rely on "internal observers" and complex processing, we compute our estimates by simple sensor fusion mechanisms, i.e., weighted sums of sensory signals combined with thresholds. We show with simulations that this simple device mimics human-like postural behavior in a wide range of situations and diseases. We have now embodied our mechanism in a biped humanoid robot to show that it works in the real world with complex, noisy, and imperfectly known sensors and effectors. On the other hand, we find that the more complex, internal-observer approach, when applied to bipedal posture, can also yield human-like behavior. We suggest that humans use both mechanisms: simple, fast sensor fusions with thresholding for automatic reactions (default mechanism), and more complex methods for voluntary movements. We suggest also that the fusion with thresholding mechanisms are optimized during phylogenesis but are mainly hardwired in any one organism, whereas sensorimotor learning and optimization is mainly a domain of the internal observers. PMID:17925253

  18. Negotiating treatment preferences: Physicians' formulations of patients' stance.

    PubMed

    Landmark, Anne Marie Dalby; Svennevig, Jan; Gulbrandsen, Pål

    2016-01-01

    Eliciting patients' values and treatment preferences is an essential element in models of shared decision making, yet few studies have investigated the interactional realizations of how physicians do this in authentic encounters. Drawing on video-recorded encounters from Norwegian secondary care, the present study uses the fine-grained empirical methodology of conversation analysis (CA) to identify one conversational practice physicians use, namely, formulations of patients' stance, in which physicians summarize or paraphrase their understanding of the patient's stance towards treatment. The purpose of this study is twofold: (1) to explore what objectives formulations of patients' stance achieve while negotiating treatment and (2) to discuss these objectives in relation to core requirements in shared decision making. Our analysis demonstrates that formulating the patient's stance is a practice physicians use in order to elicit, check, and establish patients' attitudes towards treatment. This practice is in line with general recommendations for making shared decisions, such as exploring and checking patients' preferences and values. However, the formulations may function as a device for doing more than merely checking and establishing common ground and bringing up patients' preferences and views: Accompanied by subtle deprecating expressions, they work to delegitimize the patients' stances and indirectly convey the physicians' opposing stance. Once established, these positions can be used as a basis for challenging and potentially altering the patient's attitude towards the decision, thereby making it more congruent with the physician's view. Therefore, in addition to bringing up patients' views towards treatment, we argue that physicians may use formulations of patients' stance as a resource for directing the patient towards decisions that are congruent with the physician's stance in situations with potential disagreement, whilst (ostensibly) avoiding a more

  19. EMG responses to maintain stance during multidirectional surface translations

    NASA Technical Reports Server (NTRS)

    Henry, S. M.; Fung, J.; Horak, F. B.; Peterson, B. W. (Principal Investigator)

    1998-01-01

    To characterize muscle synergy organization underlying multidirectional control of stance posture, electromyographic activity was recorded from 11 lower limb and trunk muscles of 7 healthy subjects while they were subjected to horizontal surface translations in 12 different, randomly presented directions. The latency and amplitude of muscle responses were quantified for each perturbation direction. Tuning curves for each muscle were examined to relate the amplitude of the muscle response to the direction of surface translation. The latencies of responses for the shank and thigh muscles were constant, regardless of perturbation direction. In contrast, the latencies for another thigh [tensor fascia latae (TFL)] and two trunk muscles [rectus abdominis (RAB) and erector spinae (ESP)] were either early or late, depending on the perturbation direction. These three muscles with direction-specific latencies may play different roles in postural control as prime movers or as stabilizers for different translation directions, depending on the timing of recruitment. Most muscle tuning curves were within one quadrant, having one direction of maximal activity, generally in response to diagonal surface translations. Two trunk muscles (RAB and ESP) and two lower limb muscles (semimembranosus and peroneus longus) had bipolar tuning curves, with two different directions of maximal activity, suggesting that these muscle can play different roles as part of different synergies, depending on translation direction. Muscle tuning curves tended to group into one of three regions in response to 12 different directions of perturbations. Two muscles [rectus femoris (RFM) and TFL] were maximally active in response to lateral surface translations. The remaining muscles clustered into one of two diagonal regions. The diagonal regions corresponded to the two primary directions of active horizontal force vector responses. Two muscles (RFM and adductor longus) were maximally active orthogonal to

  20. Direct corticospinal pathways contribute to neuromuscular control of perturbed stance.

    PubMed

    Taube, Wolfgang; Schubert, Martin; Gruber, Markus; Beck, Sandra; Faist, Michael; Gollhofer, Albert

    2006-08-01

    The antigravity soleus muscle (Sol) is crucial for compensation of stance perturbation. A corticospinal contribution to the compensatory response of the Sol is under debate. The present study assessed spinal, corticospinal, and cortical excitability at the peaks of short- (SLR), medium- (MLR), and long-latency responses (LLR) after posterior translation of the feet. Transcranial magnetic stimulation (TMS) and peripheral nerve stimulation were individually adjusted so that the peaks of either motor evoked potential (MEP) or H reflex coincided with peaks of SLR, MLR, and LLR, respectively. The influence of specific, presumably direct, corticospinal pathways was investigated by H-reflex conditioning. When TMS was triggered so that the MEP arrived in the Sol at the same time as the peaks of SLR and MLR, EMG remained unaffected. Enhanced EMG was observed when the MEP coincided with the LLR peak (P < 0.001). Similarly, conditioning of the H reflex by subthreshold TMS facilitated H reflexes only at LLR (P < 0.001). The earliest facilitation after perturbation occurred after 86 ms. The TMS-induced H-reflex facilitation at LLR suggests that increased cortical excitability contributes to the augmentation of the LLR peaks. This provides evidence that the LLR in the Sol muscle is at least partly transcortical, involving direct corticospinal pathways. Additionally, these results demonstrate that approximately 86 ms after perturbation, postural compensatory responses are cortically mediated. PMID:16601305

  1. The Effect of Single-Leg Stance on Dancer and Control Group Static Balance

    PubMed Central

    KILROY, ELISABETH A.; CRABTREE, OLIVIA M.; CROSBY, BRITTANY; PARKER, AMANDA; BARFIELD, WILLIAM R.

    2016-01-01

    The purpose of this study was to compare kinetic differences of static balance between female dancers (D) with at least seven years of dance experience and female non-dancers (ND) who were typical college students. Participants were tested in single-leg stance. Both the dominant leg (DL) and non-dominant leg (NDL) were tested with the participants shod (S) and barefoot (BF). Kinetic variables (vertical, medio-lateral [ML], antero-posterior [AP] maximum ground reaction forces (GRF), and center of pressure (COP) ML and AP) were measured by a Bertec force platform at 1000 Hz with participants S and BF. Each subject’s stance was measured over 3 × 30-second intervals. No significant differences (p≥0.05) existed between groups for height, body mass, or age. Significant differences existed between groups for balance time, AP GRF in both BF and S conditions for both DL and NDL, and ML GRF in BF NDL and S DL and NDL conditions. D and ND in BF and S conditions with DL and NDL static stance demonstrate different AP and ML GRF when balancing over a 30-second time interval. Data may suggest that ND are more prone to lose their balance. Further investigation is warranted to understand whether individuals in the rehabilitative field and athletic populations can use dance therapy for injury prevention and rehabilitation. PMID:27293509

  2. Neural-mechanical feedback control scheme generates physiological ankle torque fluctuation during quiet stance.

    PubMed

    Vette, Albert H; Masani, Kei; Nakazawa, Kimitaka; Popovic, Milos R

    2010-02-01

    We have recently demonstrated in simulations and experiments that a proportional and derivative (PD) feedback controller can regulate the active ankle torque during quiet stance and stabilize the body despite a long sensory-motor time delay. The purpose of the present study was to: 1) model the active and passive ankle torque mechanisms and identify their contributions to the total ankle torque during standing and 2) investigate whether a neural-mechanical control scheme that implements the PD controller as the neural controller can successfully generate the total ankle torque as observed in healthy individuals during quiet stance. Fourteen young subjects were asked to stand still on a force platform to acquire data for model optimization and validation. During two trials of 30 s each, the fluctuation of the body angle, the electromyogram of the right soleus muscle, and the ankle torque were recorded. Using these data, the parameters of: 1) the active and passive torque mechanisms (Model I) and 2) the PD controller within the neural-mechanical control scheme (Model II) were optimized to achieve potential matching between the measured and predicted ankle torque. The performance of the two models was finally validated with a new set of data. Our results indicate that not only the passive, but also the active ankle torque mechanism contributes significantly to the total ankle torque and, hence, to body stabilization during quiet stance. In addition, we conclude that the proposed neural-mechanical control scheme successfully mimics the physiological control strategy during quiet stance and that a PD controller is a legitimate model for the strategy that the central nervous system applies to regulate the active ankle torque in spite of a long sensory-motor time delay. PMID:20071280

  3. Stance Taking and Passive Voice in Turkish Academic Discourse

    ERIC Educational Resources Information Center

    Emeksiz, Zeynep Erk

    2015-01-01

    This study aims at describing the functions of passive voice and how authors reflect their stance through those functions in Turkish academic discourse. Depending on the findings of a corpus based research, this study makes a counterpoint to functionalist views on the ground that passivization does not necessarily result in promoting agents in…

  4. Angular-velocity control approach for stance-control orthoses.

    PubMed

    Lemaire, Edward D; Goudreau, Louis; Yakimovich, Terris; Kofman, Jonathan

    2009-10-01

    Currently, stance-control knee orthoses require external control mechanisms to control knee flexion during stance and allow free knee motion during the swing phase of gait. A new angular-velocity control approach that uses a rotary-hydraulic device to resist knee flexion when the knee angular velocity passes a preset threshold is presented. This angular-velocity approach for orthotic stance control is based on the premise that knee-flexion angular velocity during a knee-collapse event, such as a stumble or fall, is greater than that during walking. The new hydraulic knee-flexion control device does not require an external control mechanism to switch from free motion to stance control mode. Functional test results demonstrated that the hydraulic angular-velocity activated knee joint provided free knee motion during walking, engaged upon knee collapse, and supported body weight while the end-user recovered to a safe body position. The joint was tested to 51.6 Nm in single loading tests and passed 200,000 repeated loading cycles with a peak load of 88 Nm per cycle. The hydraulic, angular velocity activation approach has potential to improve safety and security for people with lower extremity weakness or when recovering from joint trauma. PMID:19497821

  5. Change of Attitude? A Diachronic Study of Stance

    ERIC Educational Resources Information Center

    Hyland, Ken; Jiang, Feng

    2016-01-01

    Successful research writers construct texts by taking a novel point of view toward the issues they discuss while anticipating readers' imagined reactions to those views. This intersubjective positioning is encompassed by the term stance and, in various guises, has been a topic of interest to researchers of written communication and applied…

  6. Observational stance as a predictor of subjective and genital sexual arousal in men and women.

    PubMed

    Bossio, Jennifer A; Spape, Jessica; Lykins, Amy D; Chivers, Meredith L

    2014-01-01

    Observational stance refers to the perspective a person takes while viewing a sexual stimulus, either as a passive observer (observer stance) or an active participant (participant stance). The objective of the current study was to examine the relationship between observational stance and sexual arousal (subjective and genital) across a range of sexual stimuli that do or do not correspond with a participant's sexual attraction (preferred or nonpreferred stimuli, respectively). Regression analyses revealed that, for men (n = 44), participant stance significantly predicted subjective and genital arousal. Women's (n = 47) observer and participant stance predicted subjective arousal but not genital arousal. Analysis of variance showed that participant stance was greatest under preferred sexual stimuli conditions for all groups of participants, while observer stance scores revealed a less consistent pattern of response. This was particularly true for opposite-sex-attracted women, whose ratings of observer stance were lowest for preferred stimuli. Observational stance does not appear to account for gender differences in specificity of sexual arousal; for men, however, participant stance uniquely predicted genital response after controlling for sexual attractions. Similarities in the relationships between men's and women's observational stance and sexual responses challenge previous claims of gender differences in how men and women view erotica. PMID:23514448

  7. Balance in Astronauts Performing Jumps, Walking and Quiet Stance Following Spaceflight

    NASA Technical Reports Server (NTRS)

    Reschke, Millard F.; Bloomberg, J. J.; Wood, S. J.; Harm, D. L.

    2011-01-01

    Introduction: Both balance and locomotor ataxia is severe in astronauts returning from spaceflight with serious implications for unassisted landings. As a part of an ongoing effort to demonstrate the functional significance of the postflight ataxia problem our laboratory has evaluated jumping, walking heel-to-toe and quite stance balance immediately following spaceflight. Methods: Six astronauts from 12-16 day flights and three from 6-month flights were asked to perform three self-initiated two-footed jumps from a 30-cm-high platform, walking for 10 steps (three trials) placing the feet heel to toe in tandem, arms folded across the chest and the eyes closed, and lastly, recover from a simulated fall by standing from a prone position on the floor and with eyes open maintain a quiet stance for 3 min with arms relaxed along the side of the body and feet comfortably positioned on a force plate. Crewmembers were tested twice before flight, on landing day (short-duration), and days 1, 6, and 30 following all flight durations. Results/Conclusions: Many of astronauts tested fell on their first postflight jump but recovered by the third jump showing a rapid learning progression. Changes in take-off strategy were clearly evident in duration of time in the air between the platform and the ground (significant reduction in time to land), and also in increased asymmetry in foot latencies on take-off postflight. During the tandem heel-to-toe walking task there was a significant decrease in percentage of correct steps on landing day (short-duration crew) and on first day following landing (long-duration) with only partial recovery the following day. Astronauts for both short and long duration flight times appeared to be unaware of foot position relative to their bodies or the floor. During quite stance most of crewmembers tested exhibited increased stochastic activity (larger short-term COP diffusion coefficients postflight in all planes and increases in mean sway speed).

  8. Stance width changes how sensory feedback is used for multisegmental balance control.

    PubMed

    Goodworth, Adam D; Mellodge, Patricia; Peterka, Robert J

    2014-08-01

    A multilink sensorimotor integration model of frontal plane balance control was developed to determine how stance width influences the use of sensory feedback in healthy adults. Data used to estimate model parameters came from seven human participants who stood on a continuously rotating surface with three different stimulus amplitudes, with eyes open and closed, and at four different stance widths. Dependent variables included lower body (LB) and upper body (UB) sway quantified by frequency-response functions. Results showed that stance width had a major influence on how parameters varied across stimulus amplitude and between visual conditions. Active mechanisms dominated LB control. At narrower stances, with increasing stimulus amplitude, subjects used sensory reweighting to shift reliance from proprioceptive cues to vestibular and/or visual cues that oriented the LB more toward upright. When vision was available, subjects reduced reliance on proprioception and increased reliance on vision. At wider stances, LB control did not exhibit sensory reweighting. In the UB system, both active and passive mechanisms contributed and were dependent on stance width. UB control changed across stimulus amplitude most in wide stance (opposite of the pattern found in LB control). The strong influence of stance width on sensory integration and neural feedback control implies that rehabilitative therapies for balance disorders can target different aspects of balance control by using different stance widths. Rehabilitative strategies designed to assess or modify sensory reweighting will be most effective with the use of narrower stances, whereas wider stances present greater challenges to UB control. PMID:24760788

  9. Stance width changes how sensory feedback is used for multisegmental balance control

    PubMed Central

    Mellodge, Patricia; Peterka, Robert J.

    2014-01-01

    A multilink sensorimotor integration model of frontal plane balance control was developed to determine how stance width influences the use of sensory feedback in healthy adults. Data used to estimate model parameters came from seven human participants who stood on a continuously rotating surface with three different stimulus amplitudes, with eyes open and closed, and at four different stance widths. Dependent variables included lower body (LB) and upper body (UB) sway quantified by frequency-response functions. Results showed that stance width had a major influence on how parameters varied across stimulus amplitude and between visual conditions. Active mechanisms dominated LB control. At narrower stances, with increasing stimulus amplitude, subjects used sensory reweighting to shift reliance from proprioceptive cues to vestibular and/or visual cues that oriented the LB more toward upright. When vision was available, subjects reduced reliance on proprioception and increased reliance on vision. At wider stances, LB control did not exhibit sensory reweighting. In the UB system, both active and passive mechanisms contributed and were dependent on stance width. UB control changed across stimulus amplitude most in wide stance (opposite of the pattern found in LB control). The strong influence of stance width on sensory integration and neural feedback control implies that rehabilitative therapies for balance disorders can target different aspects of balance control by using different stance widths. Rehabilitative strategies designed to assess or modify sensory reweighting will be most effective with the use of narrower stances, whereas wider stances present greater challenges to UB control. PMID:24760788

  10. The cat vertebral column: stance configuration and range of motion

    NASA Technical Reports Server (NTRS)

    Macpherson, J. M.; Ye, Y.; Peterson, B. W. (Principal Investigator)

    1998-01-01

    This study examined the configuration of the vertebral column of the cat during independent stance and in various flexed positions. The range of motion in the sagittal plane is similar across most thoracic and lumbar joints, with the exception of a lesser range at the transition region from thoracic-type to lumbar-type vertebrae. The upper thoracic column exhibits most of its range in dorsiflexion and the lower thoracic and lumbar in ventroflexion. Lateral flexion is limited to less than 5 degrees at all segments. The range in torsion is almost 180 degrees and occurs primarily in the midthoracic region, T4-T11. Contrary to the depiction in most atlases, the standing cat exhibits several curvatures, including a mild dorsiflexion in the lower lumbar segments, a marked ventroflexion in the lower thoracic and upper lumbar segments, and a profound dorsiflexion in the upper thoracic (above T9) and cervical segments. The curvatures are not significantly changed by altering stance distance but are affected by head posture. During stance, the top of the scapula lies well above the spines of the thoracic vertebrae, and the glenohumeral joint is just below the bodies of vertebrae T3-T5. Using a simple static model of the vertebral column in the sagittal plane, it was estimated that the bending moment due to gravity is bimodal with a dorsiflexion moment in the lower thoracic and lumbar region and a ventroflexion moment in the upper thoracic and cervical region. Given the bending moments and the position of the scapula during stance, it is proposed that two groups of scapular muscles provide the major antigravity support for the head and anterior trunk. Levator scapulae and serratus ventralis form the lateral group, inserting on the lateral processes of cervical vertebrae and on the ribs. The major and minor rhomboids form the medial group, inserting on the spinous tips of vertebrae from C4 to T4. It is also proposed that the hypaxial muscles, psoas major, minor, and quadratus

  11. Cerebellar control of postural scaling and central set in stance.

    PubMed

    Horak, F B; Diener, H C

    1994-08-01

    1. The effects of cerebellar deficits in humans on scaling the magnitude of automatic postural responses based on sensory feedback and on predictive central set was investigated. Electromyographic (EMG) and surface reactive torques were compared in patients with anterior lobe cerebellar disorders and in normal healthy adults exposed to blocks of four velocities and five amplitudes of surface translations during stance. Correlations between the earliest postural responses (integrated EMG and initial rate of change of torque) and translation velocity provided a measure of postural magnitude scaling using sensory information from the current displacement. Correlations of responses with translation amplitude provided a measure of scaling dependent on predictive central set based on sequential experience with previous like displacements because the earliest postural responses occurred before completion of the displacements and because scaling to displacement amplitude disappeared when amplitudes were randomized in normal subjects. 2. Responses of cerebellar patients to forward body sway induced by backward surface displacements were hypermetric, that is, surface-reactive torque responses were two to three times larger than normal with longer muscle bursts resulting in overshooting of initial posture. Despite this postural hypermetria, the absolute and relative latencies of agonist muscle bursts at the ankle, knee, and hip were normal in cerebellar patients. 3. Although they were hypermetric, the earliest postural responses of cerebellar patients were scaled normally to platform displacement velocities using somatosensory feedback. Cerebellar patients, however, were unable to scale initial postural response magnitude to expected displacement amplitudes based on prior experience using central set. Randomization of displacement amplitudes eliminated the set effect of amplitude on initial responses in normal subjects, but responses to randomized and blocked trials were not

  12. The influence of ankle muscle activation on postural sway during quiet stance.

    PubMed

    Warnica, Meagan J; Weaver, Tyler B; Prentice, Stephen D; Laing, Andrew C

    2014-04-01

    Although balance during quiet standing is postulated to be influenced by multiple factors, including ankle stiffness, it is unclear how different mechanisms underlying increases in stiffness affect balance control. Accordingly, this study examined the influence of muscle activation and passive ankle stiffness increases on the magnitude and frequency of postural sway. Sixteen young adults participated in six quiet stance conditions including: relaxed standing, four muscle active conditions (10%, 20%, 30% and 40% maximum voluntary contraction (MVC)), and one passive condition wearing an ankle foot orthotic (AFO). Kinetics were collected from a force plate, while whole-body kinematics were collected with a 12-sensor motion capture system. Bilateral electromyographic signals were recorded from the tibialis anterior and medial gastrocnemius muscles. Quiet stance sway amplitude (range and root mean square) and frequency (mean frequency and velocity) in the sagittal plane were calculated from time-varying centre of gravity (COG) and centre of pressure (COP) data. Compared to the relaxed standing condition, metrics of sway amplitude were significantly increased (between 37.5 and 63.2%) at muscle activation levels of 30% and 40% MVC. Similarly, frequency measures increased between 30.5 and 154.2% in the 20-40% MVC conditions. In contrast, passive ankle stiffness, induced through the AFO, significantly decreased sway amplitude (by 23-26%), decreased COG velocity by 13.8%, and increased mean COP frequency by 24.9%. These results demonstrate that active co-contraction of ankle musculature (common in Parkinson's Disease patients) may have differential effects on quiet stance balance control compared to the use of an ankle foot orthotic (common for those recovering from stroke). PMID:24613374

  13. Limb-Bone Scaling Indicates Diverse Stance and Gait in Quadrupedal Ornithischian Dinosaurs

    PubMed Central

    Maidment, Susannah C. R.; Linton, Deborah H.; Upchurch, Paul; Barrett, Paul M.

    2012-01-01

    Background The most primitive ornithischian dinosaurs were small bipeds, but quadrupedality evolved three times independently in the clade. The transition to quadrupedality from bipedal ancestors is rare in the history of terrestrial vertebrate evolution, and extant analogues do not exist. Constraints imposed on quadrupedal ornithischians by their ancestral bipedal bauplan remain unexplored, and consequently, debate continues about their stance and gait. For example, it has been proposed that some ornithischians could run, while others consider that none were cursorial. Methodology/Principal Findings Drawing on biomechanical concepts of limb bone scaling and locomotor theory developed for extant taxa, we use the largest dataset of ornithischian postcranial measurements so far compiled to examine stance and gait in quadrupedal ornithischians. Differences in femoral midshaft eccentricity in hadrosaurs and ceratopsids may indicate that hadrosaurs placed their feet on the midline during locomotion, while ceratopsids placed their feet more laterally, under the hips. More robust humeri in the largest ceratopsids relative to smaller taxa may be due to positive allometry in skull size with body mass in ceratopsids, while slender humeri in the largest stegosaurs may be the result of differences in dermal armor distribution within the clade. Hadrosaurs are found to display the most cursorial morphologies of the quadrupedal ornithischian cades, indicating higher locomotor performance than in ceratopsids and thyreophorans. Conclusions/Significance Limb bone scaling indicates that a previously unrealised diversity of stances and gaits were employed by quadrupedal ornithischians despite apparent convergence in limb morphology. Grouping quadrupedal ornithischians together as a single functional group hides this disparity. Differences in limb proportions and scaling are likely due to the possession of display structures such as horns, frills and dermal armor that may have affected

  14. Stability and the maintenance of balance following a perturbation from quiet stance

    NASA Astrophysics Data System (ADS)

    Stirling, J. R.; Zakynthinaki, M. S.

    2004-03-01

    We investigate stability and the maintenance of balance with the use of tools from dynamical systems. In particular we investigate the application of such tools to the study of the ground reaction forces resulting from an athlete being perturbed from quiet stance. We develop a nonlinear model consisting of a set of coupled vector fields for the derivative with respect to time of the angles between the resultant ground reaction forces and the vertical in the anteroposterior and mediolateral directions. This model contains a basin of attraction bound by a closed curve which we call the critical curve. It is only inside this curve that perturbations can be corrected, with the orbit spiraling onto an attractor corresponding to quiet stance. We show how the critical curve and also the strength of the attractor found in the basin of attraction can be fit to model the experimental data (time series) for an individual athlete. We also discuss how our model can be used to identify nonsymmetric behavior caused by muscle imbalances and differences in the ranges of motion on either side of the body.

  15. Modelling 3D control of upright stance using an optimal control strategy.

    PubMed

    Qu, Xingda; Nussbaum, Maury A

    2012-01-01

    A 3D balance control model of quiet upright stance is presented, based on an optimal control strategy, and evaluated in terms of its ability to simulate postural sway in both the anterior-posterior and medial-lateral directions. The human body was represented as a two-segment inverted pendulum. Several assumptions were made to linearise body dynamics, for example, that there was no transverse rotation during upright stance. The neural controller was presumed to be an optimal controller that generates ankle control torque and hip control torque according to certain performance criteria. An optimisation procedure was used to determine the values of unspecified model parameters including random disturbance gains and sensory delay times. This model was used to simulate postural sway behaviours characterised by centre-of-pressure (COP)-based measures. Confidence intervals for all normalised COP-based measures contained unity, indicating no significant differences between any of the simulated COP-based measures and corresponding experimental references. In addition, mean normalised errors for the traditional measures were < 8%, and those for most statistical mechanics measures were ∼3-66%. On the basis these results, the proposed 3D balance control model appears to have the ability to accurately simulate 3D postural sway behaviours. PMID:21598131

  16. Climate Literacy for Kids: Finding Medium, Message, and Stance

    NASA Astrophysics Data System (ADS)

    Fisher, D. K.; Leon, N.; Jackson, R.; Greene, M. P.

    2011-12-01

    . Various recycling bins (glass, plastic, metal, and paper) are lined up on the left and right sides of the screen, with a trash bin at the bottom. As an item drops, the player must quickly decide what kind of material it is made of and whether it is recyclable, then guide it into the appropriate bin. As the rate of items entering play increases, any missed items fall into the trash and stay there for a length of time proportional to their decomposition time. If the trash bin gets full, the game is over. While enjoying the increasing challenge of the game, players learn to identify many items as recyclable that they may not have recognized as recyclable before. Another feature on Climate Kids is "Climate Tales," a slightly edgy animated cartoon series (two episodes so far) about the adventures of a blundering polar bear, a chirpy tamarin monkey, and a grumpy old fish as "accidental tourists" around the planet, observing and dealing with the environmental conditions they encounter. Fairly complex concepts (such as reasons and implications of the declining abundance of phytoplankton) are woven into the tales. Climate Kids is a fun site for kids, educational and realistic, and yet positive and hopeful-the only reasonable stance to present to this young audience.

  17. Stance and swing phase costs in human walking

    PubMed Central

    Umberger, Brian R.

    2010-01-01

    Leg swing in human walking has historically been viewed as a passive motion with little metabolic cost. Recent estimates of leg swing costs are equivocal, covering a range from 10 to 33 per cent of the net cost of walking. There has also been a debate as to whether the periods of double-limb support during the stance phase dominate the cost of walking. Part of this uncertainty is because of our inability to measure metabolic energy consumption in individual muscles during locomotion. Therefore, the purpose of this study was to investigate the metabolic cost of walking using a modelling approach that allowed instantaneous energy consumption rates in individual muscles to be estimated over the full gait cycle. At a typical walking speed and stride rate, leg swing represented 29 per cent of the total muscular cost. During the stance phase, the double-limb and single-limb support periods accounted for 27 and 44 per cent of the total cost, respectively. Performing step-to-step transitions, which encompasses more than just the double-support periods, represented 37 per cent of the total cost of walking. Increasing stride rate at a constant speed led to greater double-limb support costs, lower swing phase costs and no change in single-limb support costs. Together, these results provide unique insight as to how metabolic energy is expended over the human gait cycle. PMID:20356877

  18. Electrical noise to a knee joint stabilizes quiet bipedal stance.

    PubMed

    Kimura, Tetsuya; Kouzaki, Motoki

    2013-04-01

    Studies have shown that a minute, noise-like electrical stimulation (ES) of a lower limb joint stabilizes one-legged standing (OS), possibly due to the noise-enhanced joint proprioception. To demonstrate the practical utility of this finding, we assessed whether the bipedal stance (BS), relatively stable and generally employed in daily activities, is also stabilized by the same ES method. Twelve volunteers maintained quiet BS with or without an unperceivable, noise-like ES of a knee joint. The results showed that the average amplitude, peak-to-peak amplitude, and standard deviation of the foot center of pressure in the anteroposterior direction were significantly attenuated by the ES (P<0.05). These results indicate that the BS also can be stabilized by an unperceivable, noise-like ES of a knee joint. PMID:23044409

  19. A Cross-Cultural Analysis of Stance in Disaster News Reports

    ERIC Educational Resources Information Center

    Liu, Lian; Stevenson, Marie

    2013-01-01

    This study examines stance in cross-cultural media discourse by comparing disaster news reports on the Sichuan earthquake of May 2008 in a Chinese, an Australian Chinese, and an Australian newspaper. The stance taken in the news reports is examined using the Attitude sub-system of Martin and White's (2005) Appraisal framework. The analysis…

  20. Embracing the Inherent Tensions in Teaching Mathematics from an Equity Stance

    ERIC Educational Resources Information Center

    Gutierrez, Rochelle

    2009-01-01

    Rather than delineating a list of practices that are important for ensuring that mathematics prepares students for a more democratic citizenship, the author has outlined in this article three tensions in teaching that she argues are important in developing an equity stance in mathematics education. This focus on a "stance" suggests that the kinds…

  1. Brought-Along Identities and the Dynamics of Ideology: Accomplishing Bivalent Stances in a Multilingual Interaction

    ERIC Educational Resources Information Center

    Williams, Ashley M.

    2008-01-01

    This paper examines how the interconnected aspects of the stance triangle (Du Bois 2007) allow speakers to tap into multiple ideological layers as they take a stance and reveal intra-ethnic group tensions. Using a detailed interaction analysis of a Chinese American family's multilingual interaction, the paper explores how such ideological dynamics…

  2. "This Project Has Personally Affected Me": Developing a Critical Stance in Preservice English Teachers

    ERIC Educational Resources Information Center

    Scherff, Lisa

    2012-01-01

    This study draws from a number of researchers who push for critical literacy and a critical stance to question power, inequality, and the status quo; to understand scholars' own participation in power structures; and to reframe and retheorize scholars' beliefs and understandings. In this article, the author uses the critical stance framework to…

  3. Risk Taking in Late Adolescence: Relations between Sociomoral Reasoning, Risk Stance, and Behavior

    ERIC Educational Resources Information Center

    Shaw, Leigh A.; Amsel, Eric; Schillo, Joshua

    2011-01-01

    This study explored relations among late adolescents' sociomoral reasoning about risk taking, risk stance, and behavior. One-hundred and thirty-two participants (18-20-year-olds) were surveyed about their own risk stance (Avoidant, Opportunistic, Curious, Risk Seeking) and behavior in three realms (Alcohol Use, Drug Use, Reckless Driving), and…

  4. Signaling Organization and Stance: Academic Language Use in Middle Grade Persuasive Writing

    ERIC Educational Resources Information Center

    Dobbs, Christina L.

    2014-01-01

    Effective academic writing is accessible to readers because writers follow shared conventions for organization and signal their stance on particular topics; however, few specifics are known about how middle graders might develop knowledge of and use these academic language forms and functions to signal their organization and stance in persuasive…

  5. EFL Doctoral Students' Conceptions of Authorial Stance in Academic Research Writing: An Exploratory Study

    ERIC Educational Resources Information Center

    Chang, Peichin

    2016-01-01

    English as foreign language (EFL) writers are often found to have weaker control of their academic writing, among which presenting an effective authorial stance has been reported as particularly challenging (Hyland, 1998a; Schleppegrell, 2004). In particular, student writers tended to deploy a stronger stance and be less effective with tentative…

  6. Ninth Grade Students' Negotiation of Aesthetic, Efferent, and Critical Stances in Response to a Novel Set in Afghanistan

    ERIC Educational Resources Information Center

    Taliaferro, Cheryl

    2011-01-01

    This qualitative, action research study was guided by two primary research questions. First, how do students negotiate aesthetic, efferent, and critical stances when reading a novel set in Afghanistan? Second, how do aesthetic and efferent stances contribute to or hinder the adoption of a critical stance? A large body of research exists that…

  7. The stance phase of walking during late pregnancy: temporospatial and ground reaction force variables.

    PubMed

    Lymbery, Janelle K; Gilleard, Wendy

    2005-01-01

    The purpose of this study was to investigate temporospatial and ground reaction force variables in the stance phase of walking during late pregnancy. An eight-camera motion-analysis system was used to record 13 pregnant women at 38 weeks' gestation and again 8 weeks after birth. In late pregnancy, there was a wider step width, and mediolateral ground reaction force tended to be increased in a medial direction. The center of pressure moved more medially initially and less anteriorly at 100% of stance in late pregnancy. The differences suggest that women may adapt their gait to maximize stability in the stance phase of walking and to control mediolateral motion. PMID:15901811

  8. Stance limb kinetics of older male athletes endurance running performance.

    PubMed

    Diss, Ceri; Gittoes, Marianne J; Tong, Richard; Kerwin, David G

    2015-09-01

    The aim of this study was to examine the age-based, lower limb kinetics of running performances of endurance athletes. Six running trials were performed by 24 male athletes, who were distinguished by three age groupings (S35: 26-32 years, M50: 50-54 years, M60+: 60-68 years). Lower limb coordinate and ground reaction force data were collected using a nine camera infra-red system synchronised with a force plate. A slower anteroposterior (M ± SD S35 = 4.13 ± 0.54 m/s: M60+ = 3.34 ± 0.40 m/s, p < 0.05) running velocity was associated with significant (p < 0.05) decreases in step length and discrete vertical ground contact force between M60+and S35 athletes. The M60+athletes simultaneously generated a 32% and 42% reduction (p < 0.05) in ankle joint moment when compared to the M50 and S35 athletes and 72% (p < 0.05) reduction in knee joint stiffness when compared to S35 athletes. Age-based declines in running performance were associated with reduced stance phase force tolerance and generation that may be accounted for due to an inhibited force-velocity muscular function of the lower limb. Joint-specific coaching strategies customised to athlete age are warranted to maintain/enhance athletes' dynamic performance. PMID:26208084

  9. 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

  10. Influence of voluntary teeth clenching on the stabilization of postural stance disturbed by electrical stimulation of unilateral lower limb.

    PubMed

    Fujino, Sachiko; Takahashi, Toshiyuki; Ueno, Toshiaki

    2010-01-01

    Studies on the relationship between dental occlusion and body balance have suggested that occlusion status contributes to the maintenance of postural balance. However, little has been reported about the effects of voluntary teeth clenching on the stabilization of postural stance in novel environments. In the present study we investigated whether teeth clenching influenced adaptation to the perturbation introduced by electrical stimulation of a unilateral lower limb. Subjects (12 adults) stood on a force plate, from which motion data were obtained in the horizontal plane with and without voluntary teeth clenching and were instructed to maintain the position throughout the experiment. We evoked a novel environment by supramaximal percutaneous electrical stimulation of the common peroneal nerve. Electromyograms (EMG) were recorded from the masseter and the peroneus longus (PL) muscles with bipolar surface cup electrodes. When the disturbed postural stance was generated by electrical stimulation, the maximum reaction force in the anterior-posterior (A/P) direction with teeth clenching (CL) was significantly smaller than that without voluntary teeth clenching (control; CO) (p<0.05) and the peak time of the ground reaction force/body mass (GRF/BM) in the A/P direction occurred earlier in the CL condition than CO (p<0.05). There were no significant differences in the peak-to-peak amplitude of GRF/BM and the peak time of GRF/BM, in the M/L direction under both CL and CO conditions. Thus, the present study showed that voluntary teeth clenching contributed to stabilization of the postural stance perturbed transiently by electrical stimulation. We concluded that voluntary teeth clenching plays an important role in rapid postural adaptation to the anterior-posterior perturbation in the upright position. PMID:19879763

  11. Walking with wider steps increases stance phase gluteus medius activity

    PubMed Central

    Kubinski, Samantha N.; McQueen, Christina A.; Sittloh, Keir A.; Dean, Jesse C.

    2014-01-01

    Increases in step width have been reported for several clinical populations, including older adults and stroke survivors. These populations often also exhibit decreased hip abductor strength, suggesting that walking with wider steps may be an adaptive response in order to reduce the mechanical demands on the hip abductors. The purpose of this study was to quantify the relationship between step width and gluteus medius (GM) activity during walking. Fourteen young, uninjured adults walked on a treadmill at 1.25 m/s for four step width conditions (Normal, Narrow, Medium, and Wide) while step width and stance phase GM electromyographic (EMG) activity were quantified. We also measured hip abduction torque and GM activity during maximum voluntary isometric contractions (MVICs) at three hip angles (neutral, abducted 10°, and abducted 20°). During walking trials, GM activity was significantly (p<0.0001) influenced by step width; compared to Normal walking, GM activity was 47% higher with Wide steps and 24% lower with Narrow steps. We also observed a weak positive correlation (r=0.18±0.14) between step width and GM activity during Normal walking, as GM activity was higher with wider steps. These results cannot be attributed to changes in GM conformation under the recording electrode, as GM activity was not influenced by hip angle during MVICs. The increased GM activity with wider steps does not support the proposal that increasing step width would be a beneficial adaptation to weakened hip abductors. A likely alternative explanation is that increased step width is a response to decreased gait balance. PMID:25300241

  12. A quasi-passive compliant stance control Knee-Ankle-Foot Orthosis.

    PubMed

    Shamaei, Kamran; Napolitano, Paul C; Dollar, Aaron M

    2013-06-01

    In this paper, we present the design of a novel quasi-passive stance-control orthosis that implements a natural amount of knee compliance during the weight acceptance phase and potentially the entire stance phase of the gait, and allows for free motion during the rest of the gait. We explain that the unaffected knee behaves close to a linear torsional spring in stance and hypothesize that an assistive device that places a linear spring of appropriate stiffness in parallel with the knee can help restore the natural behavior of the joint in stance. We present the design of a friction-based latching mechanism and a control algorithm that engages the spring in parallel with the knee in stance and disengages it during the swing phase of gait, and explain how this module is implemented into a brace in order to create a novel class of compliant stance control orthosis. The device is quasi-passive in that a small actuator serves to lock and unlock the spring module, but the device otherwise requires no actuation and very little power, computation, and control to operate. PMID:24187288

  13. As Go the Feet … : On the Estimation of Attentional Focus from Stance

    PubMed Central

    Quek, Francis; Ehrich, Roger; Lockhart, Thurmon

    2010-01-01

    The estimation of the direction of visual attention is critical to a large number of interactive systems. This paper investigates the cross-modal relation of the position of one's feet (or standing stance) to the focus of gaze. The intuition is that while one CAN have a range of attentional foci from a particular stance, one may be MORE LIKELY to look in specific directions given an approach vector and stance. We posit that the cross-modal relationship is constrained by biomechanics and personal style. We define a stance vector that models the approach direction before stopping and the pose of a subject's feet. We present a study where the subjects' feet and approach vector are tracked. The subjects read aloud contents of note cards in 4 locations. The order of `visits' to the cards were randomized. Ten subjects read 40 lines of text each, yielding 400 stance vectors and gaze directions. We divided our data into 4 sets of 300 training and 100 test vectors and trained a neural net to estimate the gaze direction given the stance vector. Our results show that 31% our gaze orientation estimates were within 5°, 51% of our estimates were within 10°, and 60% were within 15°. Given the ability to track foot position, the procedure is minimally invasive. PMID:20830212

  14. Organization position statements and the stance of "studied neutrality" on euthanasia in palliative care.

    PubMed

    Johnstone, Megan-Jane

    2012-12-01

    In recent years, palliative care and related organizations have increasingly adopted a stance of "studied neutrality" on the question of whether euthanasia should be legalized as a bona fide medical regimen in palliative care contexts. This stance, however, has attracted criticism from both opponents and proponents of euthanasia. Pro-euthanasia activists see the stance as an official position of indecision that is fundamentally disrespectful of a patient's right to "choose death" when life has become unbearable. Some palliative care constituents, in turn, are opposed to the stance, contending that it reflects an attitude of "going soft" on euthanasia and as weakening the political resistance that has hitherto been successful in preventing euthanasia from becoming more widely legalized. In this article, attention is given to examining critically the notion and possible unintended consequences of adopting a stance of studied neutrality on euthanasia in palliative care. It is argued that although palliative care and related organizations have an obvious stake in the outcome of the euthanasia debate, it is neither unreasonable nor inconsistent for such organizations to be unwilling to take a definitive stance on the issue. It is further contended that, given the long-standing tenets of palliative care, palliative care organizations have both a right and a responsibility to defend the integrity of the principles and practice of palliative care and to resist demands for euthanasia to be positioned either as an integral part or logical extension of palliative care. PMID:22771130

  15. Effect of functional foot orthoses on first metatarsophalangeal joint dorsiflexion in stance and gait.

    PubMed

    Scherer, Paul R; Sanders, Jennifer; Eldredge, Denten E; Duffy, Susan J; Lee, Ryan Y

    2006-01-01

    Reduction in first metatarsophalangeal joint maximum degree of dorsiflexion with dorsiflexion of the first ray has been proposed to be the predominant cause of hallux abducto valgus and hallux rigidus. We sought to determine whether orthoses made from a cast with the first ray plantarflexed and a 4-mm medial skive could increase the maximum degree of dorsiflexion in patients with functional hallux limitus in stance and gait. Forty-eight feet of 27 subjects were casted for orthoses with the first ray plantarflexed and in the customary neutral rearfoot position with locked midtarsal joint. First metatarsophalangeal joint maximum dorsiflexion was measured with and without orthoses in stance, and subhallux pressure was measured with and without orthoses at heel-off. Changes in mean maximum dorsiflexion in stance and in mean maximum subhallux pressure in gait with orthoses were significant. We investigated the relationship between this increase in dorsiflexion and gender, shoe size, resting calcaneal stance position, and change in resting calcaneal stance position with the use of orthoses. These correlations were not statistically significant. The biomechanical implication of increasing limited first metatarsophalangeal joint dorsiflexion with orthoses is discussed and related to the clinical treatment of deformities, including hallux valgus and hallux rigidus. The use of orthoses to decrease subhallux pressure is also discussed. PMID:17114600

  16. Single stance stability and proprioceptive control in older adults living at home: gender and age differences.

    PubMed

    Riva, Dario; Mamo, Carlo; Fanì, Mara; Saccavino, Patrizia; Rocca, Flavio; Momenté, Manuel; Fratta, Marianna

    2013-01-01

    In developed countries, falls in older people represent a rising problem. As effective prevention should start before the risk becomes evident, an early predictor is needed. Single stance instability would appear as a major risk factor. Aims of the study were to describe single stance stability, its sensory components, and their correlation with age and gender. A random sample of 597 older adults (319 men, 278 women) living at home, aged 65-84, was studied. Stability tests were performed with an electronic postural station. The single stance test showed the impairment of single stance stability in older individuals (75-84 yrs). The significant decline of stability in the older subjects may be explained by the impairment of proprioceptive control together with the decrease in compensatory visual stabilization and emergency responses. Younger subjects (65-74 yrs) exhibited better, but still inadequate, proprioceptive control with compensatory visual stabilization. Gender differences appeared in older subjects: women were significantly less stable than men. The measurement of the sensory components of single stance stability could aid in the early detection of a decay in antigravity movements many years before the risk of falling becomes evident. Adequate proprioceptive control could mitigate the effects of all other risks of falling. PMID:23984068

  17. Effects of electrical noise to a knee joint on quiet bipedal stance and treadmill walking.

    PubMed

    Kimura, T; Taki, C; Shiozawa, N; Kouzaki, M

    2013-01-01

    The present study assessed whether an unperceivable, noise-like electrical stimulation of a knee joint enhances the stability of quiet bipedal stance and treadmill walking in young subjects. The results showed that the slow postural sway measures in quiet bipedal stance were significantly reduced by the electrical noise (P<0.05). In the treadmill walking, low frequency component (below 1 Hz) of mediolateral acceleration, measured at the third lumbar vertebra, significantly decreased with the electrical noise (P<0.05), while there were no changes in the anteroposterior and vertical directions. These results indicate that the electrical noise to a knee joint can be applied to enhance postural control in quiet bipedal stance and treadmill walking. PMID:24110917

  18. Motor strategies used by rats spinalized at birth to maintain stance in response to imposed perturbations

    PubMed Central

    Giszter, Simon F; Davies, Michelle R; Graziani, Virginia

    2010-01-01

    Some rats spinalized P1/P2 achieve autonomous weight supported locomotion and quiet stance as adults. We used force platforms and robot applied perturbations to test such spinalized rats (n=6) which exhibited both weight supporting locomotion and stance, and also normal rats (n=8). Ground reaction forces in individual limbs, and the animals’ center of pressure were examined. In normal rats, both forelimbs and hindlimbs participated actively to control horizontal components of ground reaction forces. Rostral perturbations increased forelimb ground reaction forces, and caudal perturbations increased hindlimb ground reaction forces. Operate rats carried 60% body weight on the forelimbs and had a more rostral center of pressure placement. Normal rats pattern was to carry significantly more weight on the hindlimbs in quiet stance (~60%). Operate rats strategy of compensation for perturbations was entirely in forelimbs; as a result, the hind-limbs were largely isolated from the perturbation. Stiffness magnitude of the whole body was measured: its magnitude was hourglass shaped, with the principal axis oriented rostrocaudally. Operate rats were significantly less stiff; only 60-75% of normal rats’ stiffness. The injured rats adopt a stance strategy that isolates the hindlimbs from perturbation and may thus prevent hindlimb loadings. Such loadings could initiate reflex stepping, which we observed. This might activate lumbar pattern generators used in their locomotion. Adult spinalized rats never achieve independent hindlimb weight supported stance. The stance strategy of the P1 spinalized rats differed strongly from the behavior of intact rats and may be difficult for rats spinalized as adults to master. PMID:17287444

  19. Constructing Language Normativity through the Animation of Stance in Spanish Language Medical Consultations

    PubMed Central

    Vickers, Caroline H.; Deckert, Sharon K.; Goble, Ryan

    2013-01-01

    The purpose of this study is to examine the construction of language normativity as medical providers interact with patients and animate stance within Spanish language medical consultations. The context of the study is a clinic in which providers use Spanish to communicate with monolingual Spanish-speaking patients. This clinic is in the United States, an English-speaking macro-societal context. Findings indicate that providers who are second language users of Spanish animate stance and interact with patients in ways that English is constructed as normative and Spanish as marked. Implications include the need to consider how the construction of language normativity within medical consultations affects health outcomes. PMID:24156518

  20. EFL Doctoral Students' Conceptions of Authorial Stance in Academic Knowledge Claims and the Tie to Epistemic Beliefs

    ERIC Educational Resources Information Center

    Chang, Peichin; Tsai, Chin-Chung

    2014-01-01

    Taking an effective authorial stance in research argumentation has been designated as both vitally important and challenging. The study investigated English as a foreign language (EFL) doctoral students' conceptions of authorial stance, the role of domains in affecting their conceptions, and the ties of the conceptions to the…

  1. Controlling Posture and Vergence Eye Movements in Quiet Stance: Effects of Thin Plantar Inserts

    PubMed Central

    Foisy, A.; Gaertner, C.; Matheron, E.; Kapoula, Z.

    2015-01-01

    The purpose of this study was to assess properties of vergence and saccade eye movements as well as posture in quiet stance, and the effects of thin plantar inserts upon postural and oculomotor control. The performances of 36 young healthy subjects were recorded by a force platform and an eye tracker in three testing conditions: without plantar stimulation, with a 3 millimetre-thick plantar insert, either a Medial or a Lateral Arch Support (MAS / LAS). The results showed a decrease of the Surface and Variance of Speed and a more posterior position of the CoP with either stimulation compared with the control condition. The fractal analysis showed a decrease with MAS. Wavelet analysis in the time-frequency domain revealed an increase in the Cancelling Time of the low frequency band with MAS. These results suggest a better stability for a lower energy cost. Concerning eye movements, the inserts influenced only vergence (not saccades): MAS caused an increase of the phasic amplitude of divergence, and conversely a decrease of the tonic amplitude. In contrast, LAS caused an increase of the tonic amplitude of convergence. Thus, MAS renders divergence less visually driven, while LAS renders convergence more visually driven. We conclude that the CNS uses the podal signal for both postural and vergence control via specific mechanisms. Plantar inserts have an influence upon posture and vergence movements in a different way according to the part of the foot sole being stimulated. These results can be useful to clinicians interested in foot or eye. PMID:26637132

  2. Knowledge Construction among Teachers within a Community Based on Inquiry as Stance

    ERIC Educational Resources Information Center

    So, Kyunghee

    2013-01-01

    This study explores the process of teachers' knowledge construction within a community designed based on the concept of inquiry as stance. Through close examination of three teachers' activities, the study investigates how teachers adapt and respond to such a community, whether their inquiry actually generates knowledge, and how it relates to…

  3. Effect of a Wide Stance on Block Start Performance in Sprint Running

    PubMed Central

    Otsuka, Mitsuo; Kurihara, Toshiyuki; Isaka, Tadao

    2015-01-01

    This study aimed to clarify the effect of widened stance width at the set position during the block start phase in sprint running on kinematics and kinetics at the hip joint and block-induced power. Fourteen male sprinters volunteered to participate in this study. They performed three block-start trials with a normal stance width (25 ± 1 cm, normal condition) and a widened stance width (45 ± 2 cm, widened condition) at the set position. The block start movements were recorded at 250 Hz with high-speed cameras and the ground reaction forces at 1250 Hz with force plates. During the block phase in the widened condition, the hip abduction and external rotation angles in both legs were significantly larger and smaller, respectively, than those in the normal condition. The positive peak value of the hip power in the rear leg was significantly greater in the widened condition than that in the normal condition. However, no significant difference was seen in the normalized block-induced power between the widened and normal conditions. We conclude that a widened stance width at the set position affects the hip-joint kinematics and rear hip power generation during the block start phase, but no effect on the block-induced power when considering sprinting performance during the whole block start phase. PMID:26544719

  4. Divergent Effects of Cognitive Load on Quiet Stance and Task-Linked Postural Coordination

    ERIC Educational Resources Information Center

    Mitra, Suvobrata; Knight, Alec; Munn, Alexandra

    2013-01-01

    Performing a cognitive task while maintaining upright stance can lead to increased or reduced body sway depending on tasks and experimental conditions. Because greater sway is commonly taken to indicate loosened postural control, and vice versa, the precise impact of cognitive load on postural stability has remained unclear. In much of the large…

  5. From Tununak to Beaufort: Taking a Critical Inquiry Stance as a First Year Teacher

    ERIC Educational Resources Information Center

    Fecho, Bob; Price, Kim; Read, Chris

    2004-01-01

    In this article, the authors show how two first year teachers a continent apart--Kim in the village of Tununak on the Bering Sea in Alaska and Chris in Beaufort, South Carolina, on the Atlantic Ocean--were able to take inquiry stances on their classrooms. In particular, through analysis of e-mails written in Chris' and Kim's first years of…

  6. Turkish Language Teachers' Stance Taking Movements in the Discourse on Globalization and Language

    ERIC Educational Resources Information Center

    Coskun, Ibrahim

    2013-01-01

    This study investigates how Turkish teachers take and give stances in the discourse on globalization and language by using linguistic resources. According to the findings obtained through the discourse analysis of the corpus that consisted of 36 h of recording of the discussion among 4 teachers with 5 to 10 years of teaching experience, the…

  7. Faith in Academia: Integrating Students' Faith Stance into Conceptions of Their Intellectual Development

    ERIC Educational Resources Information Center

    Sabri, Duna; Rowland, Christopher; Wyatt, Jonathan; Stavrakopoulou, Francesca; Cargas, Sarita; Hartley, Helenann

    2008-01-01

    This paper explores the interaction between religious faith and academic study. It presents findings from a small-scale qualitative study of how first year theology undergraduates at Oxford experienced the relationship between academic study and their faith stance. The findings suggest varied developments in the extent to which students adapted to…

  8. Stance and Engagement in Pure Mathematics Research Articles: Linking Discourse Features to Disciplinary Practices

    ERIC Educational Resources Information Center

    McGrath, Lisa; Kuteeva, Maria

    2012-01-01

    Recent ESP research into academic writing has shown how writers convey their stance and interact with readers across different disciplines. However, little research has been carried out into the disciplinary writing practices of the pure mathematics academic community from an ESP genre analysis perspective. This study begins to address this gap by…

  9. Stability of the human upright stance depending on the frequency of external disturbances.

    PubMed

    Ishida, Akimasa; Masuda, Tadashi; Inaoka, Hidenori; Fukuoka, Yutaka

    2008-03-01

    During an upright stance of humans, it is usually assumed that a stiffer ankle joint contributes to stabilize the stance. To show that under certain conditions a stiffer ankle joint can reduce the stability, the frequency responses of the moment and the angle of the ankle joint against external disturbances caused by random horizontal translations of the support surface were evaluated in ten healthy adult subjects by varying the difficulty of the task at four levels. When it was difficult to keep the upright stance, the subject tended to make the ankle joint stiffer. The transfer function relating the external disturbance moment to the ankle joint moment showed a larger gain in the high frequency range (>0.3 Hz) compared with the gains obtained under easier conditions. A simulation analysis based on a simple inverted pendulum model also reproduced this tendency. These results indicate that the stiffer ankle joint and the resulting higher ankle moment for high frequency external disturbances enhance the possibility that the center of pressure exceeds the limit arising from the size of the feet and can make the upright stance unstable. PMID:17929068

  10. Inquiry as Stance: Practitioner Research for the Next Generation. Practitioners Inquiry

    ERIC Educational Resources Information Center

    Cochran-Smith, Marilyn; Lytle, Susan L.

    2009-01-01

    In this long-awaited sequel to "Inside/Outside: Teacher Research and Knowledge", two leaders in the field of practitioner research offer a radically different view of the relationship of knowledge and practice and of the role of practitioners in educational change. In their new book, the authors put forward the notion of inquiry as stance as a…

  11. Communicating Epistemic Stance: How Speech and Gesture Patterns Reflect Epistemicity and Evidentiality

    ERIC Educational Resources Information Center

    Roseano, Paolo; González, Montserrat; Borràs-Comes, Joan; Prieto, Pilar

    2016-01-01

    This study investigates how epistemic stance is encoded and perceived in face-to-face communication when language is regarded as comprised by speech and gesture. Two studies were conducted with this goal in mind. The first study consisted of a production task in which participants performed opinion reports. Results showed that speakers communicate…

  12. Embodied Discourse: Using Tableau to Explore Preservice Teachers' Reflections and Activist Stances

    ERIC Educational Resources Information Center

    Branscombe, Margaret; Schneider, Jenifer Jasinski

    2013-01-01

    In the context of an arts-integration course in an elementary education program, preservice teachers used tableaux (i.e. frozen scenes) to portray field experience moments in two ways: (1) as remembered events, and (2) as projected possibilities. Using video and photographs of the tableaux, we traced the students' enactment of activist stances and…

  13. Pedagogical Stances of High School ESL Teachers: "Huelgas" in High School ESL Classrooms

    ERIC Educational Resources Information Center

    del Carmen Salazar, Maria

    2010-01-01

    This article presents a qualitative case study of the pedagogical stances of high school English as a Second Language (ESL) teachers, and the subsequent responses of resistance or conformity by their English Language Learners (ELLs). The participants include three high school ESL teachers and 60 high school ESL students of Mexican origin. Findings…

  14. Changing and Changed Stance toward Norm Selection in Philippine Universities: Its Pedagogical Implications

    ERIC Educational Resources Information Center

    Bernardo, Alejandro S.

    2014-01-01

    This paper reports the results of a survey which involved College English teachers from three leading universities in the Philippines. The results point to one conclusion--College English teachers now have a changing and changed stance toward norm selection in Philippine Universities. The results give the impression that a good number of College…

  15. Stylizing Voices, Stances, and Identities Related to Medium of Education in India

    ERIC Educational Resources Information Center

    Sandhu, Priti

    2015-01-01

    This study analyzes the narrative-based interview data of three Indian women to examine the manner in which they utilize stylization to construct identity-rich, ideological stances related to discriminatory discourses of Hindi and English medium education in the linguistically rich, albeit complex, present-day context of India. Stylization is…

  16. Reported Thought as a Stance-Taking Device in Korean Conversation

    ERIC Educational Resources Information Center

    Kim, Mary Shin

    2014-01-01

    Analyses of 34 cases of direct reported thought found in ordinary Korean conversations illustrate a routine practice in the use of reported thought-reenacting a prior thought to demonstrate how the speaker's current stance originated. Often, such thoughts are not simply momentary, isolated thoughts in passing but are consequential thoughts…

  17. The Construction of Stance in Reporting Clauses: A Cross-Disciplinary Study of Theses

    ERIC Educational Resources Information Center

    Charles, Maggie

    2006-01-01

    Using a corpus-based approach, this paper investigates the construction of stance in finite reporting clauses with "that"-clause complementation. The data are drawn from two corpora of theses in contrasting disciplines: a social science--politics--and a natural science--materials science. A network for the analysis of reporting clauses is…

  18. Argument or Evidence? Disciplinary Variation in the Use of the Noun "that" Pattern in Stance Construction

    ERIC Educational Resources Information Center

    Charles, Maggie

    2007-01-01

    This paper uses a corpus approach to investigate disciplinary variation in the construction of stance using nouns which are followed by "that" and a complement clause, "e.g. the argument that the Justices exhibit strategic behaviour..." Two corpora of theses written in English are examined: approximately 190,000 words in politics/international…

  19. Ethical Considerations for Psychologists Taking a Public Stance on Controversial Issues: The Balance Between Personal and Professional Life

    PubMed Central

    Haeny, Angela M.

    2014-01-01

    Previous literature has documented the general issues psychologists often face while balancing their personal and professional lives. The struggle stems from attempting to satisfy the need to maintain a life outside of work while having the professional obligation to follow the American Psychological Association’s (APA’s) Ethical Principles of Psychologists and Code of Conduct (Ethics Code) to prevent their personal lives from interfering with their professional roles and relationships. The present paper analyzes the subject of psychologists taking a public position on controversial public issues. Although the APA Ethics Code does not restrict how psychologists conduct themselves during their personal time, taking a public stance on a controversial issue could potentially strain professional relationships and inadvertently reflect negatively on the profession. The present paper examines ethical issues that a) should be taken into account before psychologists take a public position on a controversial issue, and b) are in conflict with APA’s Ethics Code or current research. PMID:25342876

  20. Ethical Considerations for Psychologists Taking a Public Stance on Controversial Issues: The Balance Between Personal and Professional Life.

    PubMed

    Haeny, Angela M

    2014-07-01

    Previous literature has documented the general issues psychologists often face while balancing their personal and professional lives. The struggle stems from attempting to satisfy the need to maintain a life outside of work while having the professional obligation to follow the American Psychological Association's (APA's) Ethical Principles of Psychologists and Code of Conduct (Ethics Code) to prevent their personal lives from interfering with their professional roles and relationships. The present paper analyzes the subject of psychologists taking a public position on controversial public issues. Although the APA Ethics Code does not restrict how psychologists conduct themselves during their personal time, taking a public stance on a controversial issue could potentially strain professional relationships and inadvertently reflect negatively on the profession. The present paper examines ethical issues that a) should be taken into account before psychologists take a public position on a controversial issue, and b) are in conflict with APA's Ethics Code or current research. PMID:25342876

  1. Ankle and Foot Kinematics Associated with Stage II PTTD During Stance

    PubMed Central

    Houck, Jeff R.; Neville, Christopher G.; Tome, Josh; Flemister, Adolph S.

    2010-01-01

    Background Subjects with stage II posterior tibial tendon dysfunction (PTTD) exhibit abnormal foot kinematics; however, how individual segment kinematics (hindfoot (HF) or first metatarsal (first MET) segments) influence global foot kinematics is unclear. The purpose of this study was to compare foot and ankle kinematics and sagittal plane HF and first MET segment kinematics between stage II PTTD and controls. Materials and Methods Thirty patients with stage II PTTD and 15 healthy controls were evaluated. Kinematic data from the tibia, calcaneus, and first MET were collected during walking using three dimensional motion analysis techniques. A threesegment foot model (HF, calcaneus; first MET, first metatarsal, and tibia) was used to calculate relative angles (ankle, HF relative to tibia; midfoot, first MET relative to HF) and segment angles (HF and first MET relative to the global). A mixed effect ANOVA model was utilized to compare angles between groups for each variable. Results Patients with PTTD showed greater ankle plantarflexion (p = 0.02) by 6.8 degrees to 8.4 degrees prior to or at 74% of stance; greater HF eversion (p < 0.01) across stance (mean difference = 4.5 degrees); and greater first MET dorsiflexion (p < 0.01) across stance (mean difference = 8.8 degrees). HF and first MET segment angles revealed greater HF dorsiflexion (p = 0.01) during early stance and greater first MET dorsiflexion (p = 0.001) across stance. Conclusion Abnormal HF and first MET segment kinematics separately influence both ankle and midfoot movement during walking in subjects with stage II PTTD. Clinical Relevance These abnormal kinematics may serve as another measure of response to clinical treatment and/or guide for clinical strategies (exercise, orthotics, and surgery) seeking to improve foot kinematics. PMID:19486631

  2. Neural Correlates of Task Cost for Stance Control with an Additional Motor Task: Phase-Locked Electroencephalogram Responses

    PubMed Central

    Hwang, Ing-Shiou; Huang, Cheng-Ya

    2016-01-01

    With appropriate reallocation of central resources, the ability to maintain an erect posture is not necessarily degraded by a concurrent motor task. This study investigated the neural control of a particular postural-suprapostural procedure involving brain mechanisms to solve crosstalk between posture and motor subtasks. Participants completed a single posture task and a dual-task while concurrently conducting force-matching and maintaining a tilted stabilometer stance at a target angle. Stabilometer movements and event-related potentials (ERPs) were recorded. The added force-matching task increased the irregularity of postural response rather than the size of postural response prior to force-matching. In addition, the added force-matching task during stabilometer stance led to marked topographic ERP modulation, with greater P2 positivity in the frontal and sensorimotor-parietal areas of the N1-P2 transitional phase and in the sensorimotor-parietal area of the late P2 phase. The time-frequency distribution of the ERP primary principal component revealed that the dual-task condition manifested more pronounced delta (1–4 Hz) and beta (13–35 Hz) synchronizations but suppressed theta activity (4–8 Hz) before force-matching. The dual-task condition also manifested coherent fronto-parietal delta activity in the P2 period. In addition to a decrease in postural regularity, this study reveals spatio-temporal and temporal-spectral reorganizations of ERPs in the fronto-sensorimotor-parietal network due to the added suprapostural motor task. For a particular set of postural-suprapostural task, the behavior and neural data suggest a facilitatory role of autonomous postural response and central resource expansion with increasing interregional interactions for task-shift and planning the motor-suprapostural task. PMID:27010634

  3. Neural Correlates of Task Cost for Stance Control with an Additional Motor Task: Phase-Locked Electroencephalogram Responses.

    PubMed

    Hwang, Ing-Shiou; Huang, Cheng-Ya

    2016-01-01

    With appropriate reallocation of central resources, the ability to maintain an erect posture is not necessarily degraded by a concurrent motor task. This study investigated the neural control of a particular postural-suprapostural procedure involving brain mechanisms to solve crosstalk between posture and motor subtasks. Participants completed a single posture task and a dual-task while concurrently conducting force-matching and maintaining a tilted stabilometer stance at a target angle. Stabilometer movements and event-related potentials (ERPs) were recorded. The added force-matching task increased the irregularity of postural response rather than the size of postural response prior to force-matching. In addition, the added force-matching task during stabilometer stance led to marked topographic ERP modulation, with greater P2 positivity in the frontal and sensorimotor-parietal areas of the N1-P2 transitional phase and in the sensorimotor-parietal area of the late P2 phase. The time-frequency distribution of the ERP primary principal component revealed that the dual-task condition manifested more pronounced delta (1-4 Hz) and beta (13-35 Hz) synchronizations but suppressed theta activity (4-8 Hz) before force-matching. The dual-task condition also manifested coherent fronto-parietal delta activity in the P2 period. In addition to a decrease in postural regularity, this study reveals spatio-temporal and temporal-spectral reorganizations of ERPs in the fronto-sensorimotor-parietal network due to the added suprapostural motor task. For a particular set of postural-suprapostural task, the behavior and neural data suggest a facilitatory role of autonomous postural response and central resource expansion with increasing interregional interactions for task-shift and planning the motor-suprapostural task. PMID:27010634

  4. Speaking "Common Sense" about the Soviet Threat: Reagan's Rhetorical Stance.

    ERIC Educational Resources Information Center

    Ivie, Robert L.

    Although for the 15 years preceding his election as President of the United States Ronald Reagan muted his anti-Soviet rhetoric in order to achieve political power, since his election he has returned to anti-Sovietism in an effort to redirect American foreign policy against the Soviets. At the same time, however, he employs a rhetorical strategy…

  5. Postural stability deficits during the transition from double-leg stance to single-leg stance in anterior cruciate ligament reconstructed subjects.

    PubMed

    Dingenen, Bart; Janssens, Luc; Claes, Steven; Bellemans, Johan; Staes, Filip F

    2015-06-01

    The goal of this study was to evaluate postural stability during the transition from double-leg stance (DLS) to single-leg stance (SLS) in anterior cruciate ligament reconstructed (ACLR) (n=20) and non-injured control subjects (n=20). All ACLR subjects had fully returned to their pre-injury sport participation. Both groups were similar for age, gender, height, weight, body mass index and activity level. Spatiotemporal center of pressure outcomes of both legs of each subject were measured during the transition from DLS to SLS in eyes open and eyes closed conditions. Movement speed was standardized. The center of pressure displacement after a new stability point was reached during the SLS phase was significantly increased in the ACLR group compared to the control group in the eyes closed condition (P=.001). No significant different postural stability outcomes were found between the operated and non-operated legs. In conclusion, the ACLR group showed postural stability deficits, indicating that these persons may have a decreased ability to stabilize their body after the internal postural perturbation created by the transition from DLS to SLS. The non-operated leg may not be the best reference when evaluating postural stability of the operated leg after ACLR, as no differences were found between legs. PMID:25744596

  6. Hamstring Musculotendon Dynamics during Stance and Swing Phases of High Speed Running

    PubMed Central

    Chumanov, Elizabeth S.; Heiderscheit, Bryan C.; Thelen, Darryl G.

    2011-01-01

    Introduction Hamstring strain injuries are common in sports that involve high speed running. It remains uncertain whether the hamstrings are susceptible to injury during late swing phase, when the hamstrings are active and lengthening, or during stance, when contact loads are present. In this study we used forward dynamic simulations to compare hamstring musculotendon stretch, loading and work done during stance and swing phases of high speed running gait cycles. Methods Whole body kinematics, EMG activities and ground reactions were collected as 12 subjects ran on an instrumented treadmill at speeds ranging from 80% to maximum (average of 7.8 m/s). Subject-specific simulations were then created using a whole body musculoskeletal model that included fifty-two Hill-type musculotendon units acting about the hip and knee. A computed muscle control algorithm was used to determine muscle excitation patterns that drove the limb to track measured hip and knee sagittal plane kinematics, with measured ground reactions applied to the limb. Results The hamstrings lengthened under load from 50% to 90% of the gait cycle (swing), and then shortened under load from late swing through stance. While peak hamstring stretch was invariant with speed, lateral hamstring (biceps femoris) loading increased significantly with speed, and was greatest during swing at the fastest speed. The biarticular hamstrings performed negative work on the system only during swing phase, with the amount of negative work increasing significantly with speed. Conclusion We concluded that the large inertial loads during high speed running appear to make the hamstrings most susceptible to injury during swing phase when compared to stance phase. This information is relevant for scientifically establishing effective muscle injury prevention and rehabilitation programs. PMID:20689454

  7. Implementation of a physiologically identified PD feedback controller for regulating the active ankle torque during quiet stance.

    PubMed

    Vette, Albert H; Masani, Kei; Popovic, Milos R

    2007-06-01

    Our studies have recently demonstrated that a proportional and derivative (PD) feedback controller, which takes advantage of the body's position and velocity information to regulate balance during quiet standing, can compensate for long neurological time delays and generate a control command that precedes body sway by 100-200 ms. Furthermore, PD gain pairs were identified that ensure a robust system behavior and at the same time generate dynamic responses as observed in quiet standing experiments with able-bodied subjects. The purpose of the present study was to experimentally verify that the PD controller identified in our previous study can: 1) regulate the active ankle torque to stabilize the body during quiet standing in spite of long neurological time delays and 2) generate system dynamics, i.e., a motor command and body sway fluctuation, that successfully mimic those of the physiologic system of quiet standing. Our real-time closed-loop feedback circuit consisted of a center of mass position sensor and a functional electrical stimulator that elicited contractions of the plantar flexors as determined by the aforementioned PD controller. The control system regulated upright stance of a subject who was partially de-afferented and de-efferented due to a neurological disorder called von Hippel-Lindau Syndrome (McCormick Grade III). While the subject was able to generate a motor command for the ankle joints, he could not regulate the resulting torque sufficiently due to a lack of sensory feedback and motor control. It is important to mention that a time delay was included in the closed-loop circuit of the PD controller to mimic the actual neurological time delay observed in able-bodied individuals. The experimental results of this case study suggest that the proposed PD controller in combination with a functional electrical stimulation system can regulate the active ankle torque during quiet stance and generate the same system dynamics as observed in healthy

  8. DOES RECTUS FEMORIS TRANSFER INCREASE KNEE FLEXION DURING STANCE PHASE IN CEREBRAL PALSY?

    PubMed Central

    de Morais, Mauro César; Blumetti, Francesco Camara; Kawamura, Cátia Miyuki; Lopes, José Augusto Fernandes; Neves, Daniella Lins; Cardoso, Michelle de Oliveira

    2016-01-01

    ABSTRACT Objective: To evaluate whether distal rectus femoris transfer (DRFT) is related to postoperative increase of knee flexion during the stance phase in cerebral palsy (CP). Methods: The inclusion criteria were Gross Motor Function Classification System (GMFCS) levels I-III, kinematic criteria for stiff-knee gait at baseline, and individuals who underwent orthopaedic surgery and had gait analyses performed before and after intervention. The patients included were divided into the following two groups: NO-DRFT (133 patients), which included patients who underwent orthopaedic surgery without DRFT, and DRFT (83 patients), which included patients who underwent orthopaedic surgery that included DRFT. The primary outcome was to evaluate in each group if minimum knee flexion in stance phase (FMJFA) changed after treatment. Results: The mean FMJFA increased from 13.19° to 16.74° (p=0.003) and from 10.60° to 14.80° (p=0.001) in Groups NO-DRFT and DRFT, respectively. The post-operative FMJFA was similar between groups NO-DRFT and DRFT (p=0.534). The increase of FMJFA during the second exam (from 13.01° to 22.51°) was higher among the GMFCS III patients in the DRFT group (p<0.001). Conclusion: In this study, DRFT did not generate additional increase of knee flexion during stance phase when compared to the control group. Level of Evidence III, Retrospective Comparative Study. PMID:26997910

  9. From relational ontology to transformative activist stance on development and learning: expanding Vygotsky's (CHAT) project

    NASA Astrophysics Data System (ADS)

    Stetsenko, Anna

    2008-07-01

    This paper offers steps towards overcoming current fragmentation within sociocultural approaches by expansively reconstructing a broad dialectical view on human development and learning (drawing on Vygotsky's project) underwritten by ideology of social justice. The common foundation for sociocultural approaches is developed by dialectically supplanting relational ontology with the notion that collaborative purposeful transformation of the world is the core of human nature and the principled grounding for learning and development. An activist transformative stance suggests that people come to know themselves and their world as well as ultimately come to be human in and through (not in addition to) the processes of collaboratively transforming the world in view of their goals. This means that all human activities (including psychological processes and the self) are instantiations of contributions to collaborative transformative practices that are contingent on both the past and the vision for the future and therefore are profoundly imbued with ideology, ethics, and values. And because acting, being, and knowing are seen from a transformative activist stance as all rooted in, derivative of, and instrumental within a collaborative historical becoming, this stance cuts across and bridges the gaps (a) between individual and social and (b) among ontological, epistemological, and moral-ethical (ideological) dimensions of activity.

  10. Differences in Postural Control During Single-Leg Stance Among Healthy Individuals With Different Foot Types.

    PubMed

    Hertel, Jay; Gay, Michael R; Denegar, Craig R

    2002-06-01

    OBJECTIVE: To identify differences in postural control among healthy individuals with different architectural foot types. DESIGN AND SETTING: We compared postural control during single-leg stance in healthy individuals with cavus, rectus, and planus foot types in our athletic training research laboratory. SUBJECTS: Thirty healthy, young adults (15 men, 15 women; age, 21.9 +/- 2.0 years; mass, 71.6 +/- 16.7 kg; height, 168.4 +/- 13.6 cm) had their feet categorized based on rearfoot and forefoot alignment measures. The right and left feet of a subject could be classified into different categories, and each foot was treated as a subject. There were 19 cavus, 23 rectus, and 18 planus feet. MEASUREMENTS: Subjects performed three 10-second trials of single-leg stance on each leg with eyes open while standing on a force platform. Dependent measures were center-of-pressure (COP) excursion area and velocity. RESULTS: Subjects with cavus feet used significantly larger COP excursion areas than did subjects with rectus feet. However, COP excursion velocities were not significantly different among foot types. CONCLUSIONS: Clinicians and researchers assessing postural control in single-leg stance with measures of COP excursion area must be cognizant of preexisting differences among foot types. If individuals' foot types are not taken into account, the results of clinical and research investigations assessing COP excursion area after injury may be confounded. PMID:12937424

  11. Variable stiffness actuated prosthetic knee to restore knee buckling during stance: a modeling study.

    PubMed

    Wentink, E C; Koopman, H F J M; Stramigioli, S; Rietman, J S; Veltink, P H

    2013-06-01

    Most modern intelligent knee prosthesis use dampers to modulate dynamic behavior and prevent excessive knee flexion, but they dissipate energy and do not assist in knee extension. Energy efficient variable stiffness control (VSA) can reduce the energy consumption yet effectively modulate the dynamic behavior and use stored energy during flexion to assist in subsequent extension. A principle design of energy efficient VSA in a prosthetic knee is proposed and analyzed for the specific case of rejection of a disturbed stance phase. The concept is based on the principle that the output stiffness of a spring can be changed without changing the energy stored in the elastic elements of the spring. The usability of this concept to control a prosthetic knee is evaluated using a model. Part of the stance phase of the human leg was modeled by a double pendulum. Specifically the rejection of a common disturbance of transfemoral prosthetic gait, an unlocked knee at heel strike, was evaluated. The ranges of spring stiffnesses were determined such that the angular characteristics of a normal stance phase were preserved, but disturbances could also be rejected. The simulations predicted that energy efficient VSA can be useful for the control of prosthetic knees. PMID:23000012

  12. Postural Instability Detection: Aging and the Complexity of Spatial-Temporal Distributional Patterns for Virtually Contacting the Stability Boundary in Human Stance

    PubMed Central

    Kilby, Melissa C.; Slobounov, Semyon M.; Newell, Karl M.

    2014-01-01

    Falls among the older population can severely restrict their functional mobility and even cause death. Therefore, it is crucial to understand the mechanisms and conditions that cause falls, for which it is important to develop a predictive model of falls. One critical quantity for postural instability detection and prediction is the instantaneous stability of quiet upright stance based on motion data. However, well-established measures in the field of motor control that quantify overall postural stability using center-of-pressure (COP) or center-of-mass (COM) fluctuations are inadequate predictors of instantaneous stability. For this reason, 2D COP/COM virtual-time-to-contact (VTC) is investigated to detect the postural stability deficits of healthy older people compared to young adults. VTC predicts the temporal safety margin to the functional stability boundary ( =  limits of the region of feasible COP or COM displacement) and, therefore, provides an index of the risk of losing postural stability. The spatial directions with increased instability were also determined using quantities of VTC that have not previously been considered. Further, Lempel-Ziv-Complexity (LZC), a measure suitable for on-line monitoring of stability/instability, was applied to explore the temporal structure or complexity of VTC and the predictability of future postural instability based on previous behavior. These features were examined as a function of age, vision and different load weighting on the legs. The primary findings showed that for old adults the stability boundary was contracted and VTC reduced. Furthermore, the complexity decreased with aging and the direction with highest postural instability also changed in aging compared to the young adults. The findings reveal the sensitivity of the time dependent properties of 2D VTC to the detection of postural instability in aging, availability of visual information and postural stance and potential applicability as a predictive

  13. Obesity Impact on the Attentional Cost for Controlling Posture

    PubMed Central

    Mignardot, Jean-Baptiste; Olivier, Isabelle; Promayon, Emmanuel; Nougier, Vincent

    2010-01-01

    Background This study investigated the effects of obesity on attentional resources allocated to postural control in seating and unipedal standing. Methods Ten non obese adults (BMI = 22.4±1.3, age = 42.4±15.1) and 10 obese adult patients (BMI = 35.2±2.8, age = 46.2±19.6) maintained postural stability on a force platform in two postural tasks (seated and unipedal). The two postural tasks were performed (1) alone and (2) in a dual-task paradigm in combination with an auditory reaction time task (RT). Performing the RT task together with the postural one was supposed to require some attentional resources that allowed estimating the attentional cost of postural control. 4 trials were performed in each condition for a total of 16 trials. Findings (1) Whereas seated non obese and obese patients exhibited similar centre of foot pressure oscillations (CoP), in the unipedal stance only obese patients strongly increased their CoP sway in comparison to controls. (2) Whatever the postural task, the additional RT task did not affect postural stability. (3) Seated, RT did not differ between the two groups. (4) RT strongly increased between the two postural conditions in the obese patients only, suggesting that body schema and the use of internal models was altered with obesity. Interpretation Obese patients needed more attentional resources to control postural stability during unipedal stance than non obese participants. This was not the case in a more simple posture such as seating. To reduce the risk of fall as indicated by the critical values of CoP displacement, obese patients must dedicate a strong large part of their attentional resources to postural control, to the detriment of non-postural events. Obese patients were not able to easily perform multitasking as healthy adults do, reflecting weakened psycho-motor abilities. PMID:21187914

  14. Influence of enhanced visual feedback on postural control and spinal reflex modulation during stance.

    PubMed

    Taube, Wolfgang; Leukel, Christian; Gollhofer, Albert

    2008-07-01

    The present study assessed the influence of visual feedback on stance stability and soleus H-reflex excitability. The centre of pressure (COP) displacement was measured in upright stance on a rigid surface (stable surface) and on a spinning top (unstable surface) while subjects either received "normal" visual feedback (without laser pointer = WLP) or pointed with a laser pointer on a target on the wall (LP). In order to verify that laser pointing influenced visual feedback, two additional experiments were conducted: (1) Subjects performed a finger reaction task which was thought to increase attention and cognitive demands without alteration of the visual feedback. (2) The effect of laser pointing on the wall was compared with pointing at a board, which was attached to the subjects themselves. In this case, the laser point could not serve as a reference for sway because the board moved in synchrony with the body. On stable and unstable surface, COP displacement was reduced in the LP compared to the WLP task (-17 cm +/- 6, P < 0.05; -14 cm +/- 6, P < 0.05). Conversely, H-reflexes were greater in the LP condition (stable: +20 microV +/- 30, not significant; unstable +115 microV +/- 40, P < 0.05). Stance stability and H-reflex modulation were negatively correlated (R(2) = -0.5; P < 0.001). The finger reaction task did neither influence COP displacement nor H-reflexes. Pointing at the body-fixed target did not alter COP displacement. These findings suggest that postural sway can be reduced by a handheld laser pointer targeting on an external reference point. It is argued that altered visual input was responsible for modulating the H-reflex. PMID:18421451

  15. The intentional stance as structure learning: a computational perspective on mindreading.

    PubMed

    Dindo, Haris; Donnarumma, Francesco; Chersi, Fabian; Pezzulo, Giovanni

    2015-10-01

    Recent theories of mindreading explain the recognition of action, intention, and belief of other agents in terms of generative architectures that model the causal relations between observables (e.g., observed movements) and their hidden causes (e.g., action goals and beliefs). Two kinds of probabilistic generative schemes have been proposed in cognitive science and robotics that link to a "theory theory" and "simulation theory" of mindreading, respectively. The former compares perceived actions to optimal plans derived from rationality principles and conceptual theories of others' minds. The latter reuses one's own internal (inverse and forward) models for action execution to perform a look-ahead mental simulation of perceived actions. Both theories, however, leave one question unanswered: how are the generative models - including task structure and parameters - learned in the first place? We start from Dennett's "intentional stance" proposal and characterize it within generative theories of action and intention recognition. We propose that humans use an intentional stance as a learning bias that sidesteps the (hard) structure learning problem and bootstraps the acquisition of generative models for others' actions. The intentional stance corresponds to a candidate structure in the generative scheme, which encodes a simplified belief-desire folk psychology and a hierarchical intention-to-action organization of behavior. This simple structure can be used as a proxy for the "true" generative structure of others' actions and intentions and is continuously grown and refined - via state and parameter learning - during interactions. In turn - as our computational simulations show - this can help solve mindreading problems and bootstrap the acquisition of useful causal models of both one's own and others' goal-directed actions. PMID:26168854

  16. Effect of walking velocity on hindlimb kinetics during stance in normal horses.

    PubMed

    Khumsap, S; Clayton, H M; Lanovaz, J L

    2001-04-01

    The objectives of this study were to measure the effect of walking velocity on net joint moments and joint powers in the hindlimb during stance and to use the data to predict these variables at different walking velocities. Videographic and force data were collected synchronously from 5 sound horses walking over a force plate at a range of velocities. Force and kinematic data from 56 trials were combined using an inverse dynamic solution to determine net joint moments and joint powers. Analysis by simple regression and correlation (P < 0.05, r2 > or = 0.30, r > 0.50) showed that, in early stance, there were significant velocity-dependent increases in the peak magnitudes of the following variables: extensor moment and positive power at the hip, flexor moment and positive power at the stifle, extensor moment, negative and positive power at the tarsus, and flexor moment and negative power at the fetlock. In late stance, there were significant velocity-dependent increases in the peak magnitudes of the following variables: flexor moment at the hip, negative power at the stifle and flexor moment and positive power at the tarsus. As velocity increased, the hip showed an increase in energy generation, whereas the tarsus showed increases in both energy generation and absorption. It is concluded that an increase in walking velocity is associated with increases in peak magnitudes of the net joint moments and joint powers in the hindlimb; and that energy generation at the hip makes the largest contribution to the increase in velocity. PMID:11721562

  17. The influence of sensory information on two-component coordination during quiet stance.

    PubMed

    Zhang, Yuanfen; Kiemel, Tim; Jeka, John

    2007-07-01

    When standing quietly, human upright stance is typically approximated as a single segment inverted pendulum. In contrast, investigations, which perturb upright stance with support, surface translations or visual driving stimuli have shown that the body behaves like a two-segment pendulum, displaying both in-phase and anti-phase patterns between the upper and lower body. We have recently shown that these patterns co-exist during quiet stance; in-phase and anti-phase for frequencies below and above 1 Hz, respectively. Here we investigated whether the characteristics of these basic patterns were influenced by the addition or removal of sensory information. Ten healthy young subjects stood upright on a rigid platform with different combinations of sensory information: eyes were open or closed with or without light touch contact (<1N) of the right index fingertip with a 5 cm diameter rigid force plate. The in-phase and anti-phase pattern co-exist in both the anterior-posterior (AP) and medial-lateral (ML) directions of sway. The real part of trunk-leg complex coherence decreased with the addition of vision and light touch, corresponding to a transition from the in-phase to anti-phase pattern at a lower frequency. In the AP direction, the decrease was only observed at frequencies below 1 Hz where the in-phase pattern predominates. Additional sensory information had no observable effect at sway frequencies above 1 Hz, where the anti-phase pattern predominates. Both patterns are clearly the result of a double-linked inverted pendulum dynamics, but the coherence of the in-phase pattern is more susceptible to modulation by sensory information than the anti-phase pattern. PMID:17046262

  18. Non-Gaussian center-of-pressure velocity distribution during quiet stance

    NASA Astrophysics Data System (ADS)

    Santos, E. S. D.; Picoli, S.; Deprá, P. P.; Mendes, R. S.

    2015-02-01

    In the present study, we investigate patterns in the postural sway that characterize the static balance in human beings. To measure the postural sway, sixteen healthy young subjects performed quiet stance tasks providing the center-of-pressure (COP) trajectories. From these trajectories, we obtained the COP velocities. We verified that the velocity distributions exhibit non-normal behavior and can be approximated by generalized Gaussians with fat tails. We also discuss possible implications of modeling COP velocity by using generalized Fokker-Planck equations related to Tsallis statistics and Richardson anomalous diffusion.

  19. TIBIOFEMORAL KINEMATICS AND CONDYLAR MOTION DURING THE STANCE PHASE OF GAIT

    PubMed Central

    Kozanek, Michal; Hosseini, Ali; Liu, Fang; Van de Velde, Samuel K.; Gill, Thomas J.; Rubash, Harry E.; Li, Guoan

    2009-01-01

    Accurate knowledge of the dynamic knee motion in vivo is instrumental for understanding normal and pathological function of the knee joint. However, interpreting motion of the knee joint during gait in other than the sagittal plane remains controversial. In this study, we utilized the dual fluoroscopic imaging technique to investigate the six-degree of freedom kinematics and condylar motion of the knee during the stance phase of treadmill gait in eight healthy volunteers at a speed of 0.67m/sec. We hypothesized that the 6DOF knee kinematics measured during gait will be different from those reported for non-weightbearing activities, especially with regards to the phenomenon of femoral rollback. In addition, we hypothesized that motion of the medial femoral condyle in the transverse plane is greater than that of the lateral femoral condyle during the stance phase of treadmill gait. The rotational motion and the anterior-posterior translation of the femur with respect to the tibia showed a clear relationship with the flexion-extension path of the knee during the stance phase. Additionally, we observed that the phenomenon of femoral rollback was reversed, with the femur noted to move posteriorly with extension and anteriorly with flexion. Furthermore, we noted that motion of the medial femoral condyle in the transverse plane was greater than that of the lateral femoral condyle during the stance phase of gait (17.4±2.0 mm vs. 7.4±6.1 mm, respectively; p<0.01). The trend was opposite to what has been observed during non-weightbearing flexion or single-leg lunge in previous studies. These data provide baseline knowledge for the understanding of normal physiology and for the analysis of pathological function of the knee joint during walking. These findings further demonstrate that knee kinematics is activity-dependent and motion patterns of one activity (non-weightbearing flexion or lunge) cannot be generalized to interpret a different one (gait). PMID:19497573

  20. Unexpected Fascicle Length Changes In Denervated Feline Soleus Muscle During Stance Phase Of Walking.

    PubMed

    Mehta, Ricky; Maas, Huub; Gregor, Robert J; Prilutsky, Boris I

    2015-01-01

    After surgical repair of traumatically severed peripheral nerves, associated muscles are paralyzed for weeks. Little is known about fascicle length changes in paralyzed muscles during locomotion. The aim of this study was to investigate to what extent, if any, muscle fascicles of denervated feline soleus (SO) change length during stance of walking when intact SO synergists are actively contracting. Hindlimb kinematics, SO fascicle and muscle-tendon unit (MTU) length, and EMG activity of SO, lateral gastrocnemius (LG) and medial gastrocnemius (MG) were measured during level and slope walking in adult cats. Measurements were taken before and 1-2 weeks following SO-LG denervation. Unexpectedly, SO fascicle lengthening and shortening during stance in all walking conditions were evident after denervation. The greatest SO fascicle shortening (17.3 ± 2.2% of a reference length) and least fascicle lengthening (1.5 ± 0.8%) after denervation were found during upslope walking, where MG EMG activity was greatest across slopes (P < 0.05) and greatest discrepancies between post denervation SO fascicle and MTU length changes occurred. These findings suggest that myofascial linkages between denervated SO and its active synergists might affect its fascicle length changes. Further studies are needed to directly test this suggestion. PMID:26635206

  1. Use of physical therapy in a dog with bilateral severe plantigrade stance.

    PubMed

    Ree, Jennifer; Hayashi, Kei; Woelz, Jacqueline; Kim, Sun Young

    2015-01-01

    A 3.5 yr old spayed female Staffordshire terrier weighing 25.5 kg was presented with a 7 wk history of bilateral plantigrade stance in the pelvic limbs directly following an ovariohysterectomy procedure. Upon presentation, the dog had bilateral atrophy of the distal pelvic limb muscles, enlarged popliteal lymph nodes, and ulcerative wounds on the dorsa of her rear paws. Orthopedic examination revealed intact calcaneal tendons bilaterally and neurologic examination localized the lesion to the distal sciatic nerve. A diagnosis of compressive and stretch neuropathy was made affecting the distal sciatic nerve branches. Physical therapy modalities included neuromuscular electrical stimulation, ultrasound, and low-level laser therapy. Other therapeutic modalities included the use of orthotics and progressive wound care. The dog had increased muscle mass, return of segmental reflexes, return of nociception, and the ability to walk on pelvic limbs with higher carriage of the hock 15 mo following presentation. The use of custom orthotics greatly increased the quality of life and other physical therapy modalities may have improved the prognosis in this dog with severe bilateral plantigrade stance due to neuropathy. PMID:25415214

  2. Unexpected Fascicle Length Changes In Denervated Feline Soleus Muscle During Stance Phase Of Walking

    PubMed Central

    Mehta, Ricky; Maas, Huub; Gregor, Robert J.; Prilutsky, Boris I.

    2015-01-01

    After surgical repair of traumatically severed peripheral nerves, associated muscles are paralyzed for weeks. Little is known about fascicle length changes in paralyzed muscles during locomotion. The aim of this study was to investigate to what extent, if any, muscle fascicles of denervated feline soleus (SO) change length during stance of walking when intact SO synergists are actively contracting. Hindlimb kinematics, SO fascicle and muscle-tendon unit (MTU) length, and EMG activity of SO, lateral gastrocnemius (LG) and medial gastrocnemius (MG) were measured during level and slope walking in adult cats. Measurements were taken before and 1–2 weeks following SO-LG denervation. Unexpectedly, SO fascicle lengthening and shortening during stance in all walking conditions were evident after denervation. The greatest SO fascicle shortening (17.3 ± 2.2% of a reference length) and least fascicle lengthening (1.5 ± 0.8%) after denervation were found during upslope walking, where MG EMG activity was greatest across slopes (P < 0.05) and greatest discrepancies between post denervation SO fascicle and MTU length changes occurred. These findings suggest that myofascial linkages between denervated SO and its active synergists might affect its fascicle length changes. Further studies are needed to directly test this suggestion. PMID:26635206

  3. 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. PMID:26810735

  4. Human stance control beyond steady state response and inverted pendulum simplification.

    PubMed

    Schweigart, G; Mergner, T

    2008-03-01

    Systems theory analyses have suggested that human upright stance can be modelled in terms of continuous multi-sensory feedback control. So far, these analyses have considered mainly steady-state responses to periodic stimuli and relied on a simplifying model of the body's mechanics in the form of an inverted pendulum. Therefore, they may have ignored relevant aspects of the postural behaviour. To prove a more general validity of a stance control model that we previously derived from such analyses, we now presented subjects with static-dynamic stimulus combinations and assessed response transients, anterior-posterior (a-p) response asymmetries, and possible deviations from the 'inverted pendulum' simplification (by measuring hip and knee bending). We presented normal subjects (Ns) and vestibular loss patients (Ps) with a-p support surface tilt on a motion platform under the instruction to maintain, with eyes closed, the body upright in space. In addition, subjects were to indicate perceived platform tilt with the help of pointers. We combined a fixed-amplitude sinusoidal tilt (0.1 Hz) with static tilts that were varied in amplitude and direction. We recorded upper body (shoulder) and lower body (hip) excursions in space and centre of pressure (COP) shift, and calculated the centre of mass (COM) angular excursion. We found that: (1) Immediately prior to stimulus onset (which was highly predictable), subjects showed a small anticipatory forward lean. (2) The subsequent transient response consisted of two parts. First, the body was moved along with the platform tilt and then, in the second part, the body excursion was braked by starting tilt compensation. Upon increasing tilt amplitude, the braking point showed a pronounced saturation with for-aft asymmetry. (3) During the following prolonged tilt, the tonic body excursions saturated with increasing static tilt amplitude. This saturation also showed a for-aft asymmetry (backwards saturation more pronounced). In

  5. Immediate effects of the trunk stabilizing exercise on static balance parameters in double-leg and one-leg stances

    PubMed Central

    Kim, Jwa-jun; Park, Se-yeon

    2016-01-01

    [Purpose] The purpose of this study was to evaluate the immediate effect of stabilizing exercise using the PNF technique on standing balance in one-leg and double-leg stances. [Subjects and Methods] The present study recruited 34 healthy participants from a local university. The Participants performed four balance tests (double-leg stance with and without vision, one-leg stance with and without vision), before and after exercise. The exercise consisted of exercises performed using PNF techniques (stabilizing reversal and rhythmic stabilization), which were applied to facilitate trunk musculature. To examine balance ability, total displacement of the center of pressure was measured during balance tests. [Results] The total anterior–posterior center of pressure displacement was significantly reduced after applying rhythmic stabilization compared before exercise regardless of the balance test conditions. [Conclusion] The present results suggest that trunk stability exercise using rhythmic stabilization could effectively enhance balance ability under one-leg and double-leg conditions. PMID:27390392

  6. Effect of vision and stance width on human body motion when standing: implications for afferent control of lateral sway.

    PubMed Central

    Day, B L; Steiger, M J; Thompson, P D; Marsden, C D

    1993-01-01

    1. Measurements of human upright body movements in three dimensions have been made on thirty-five male subjects attempting to stand still with various stance widths and with eyes closed or open. Body motion was inferred from movements of eight markers fixed to specific sites on the body from the shoulders to the ankles. Motion of these markers was recorded together with motion of the point of application of the resultant of the ground reaction forces (centre of pressure). 2. The speed of the body (average from eight sites) was increased by closing the eyes or narrowing the stance width and there was an interaction between these two factors such that vision reduced body speed more effectively when the feet were closer together. Similar relationships were found for components of velocity both in the frontal and sagittal planes although stance width exerted a much greater influence on the lateral velocity component. 3. Fluctuations in position of the body were also increased by eye closure or narrowing of stance width. Again, the effect of stance width was more potent for lateral than for anteroposterior movements. In contrast to the velocity measurements, there was no interaction between vision and stance width. 4. There was a progressive increase in the amplitude of position and velocity fluctuations from markers placed higher on the body. The fluctuations in the position of the centre of pressure were similar in magnitude to those of the markers placed near the hip. The fluctuations in velocity of centre of pressure, however, were greater than of any site on the body. 5. Analysis of the amplitude of angular motion between adjacent straight line segments joining the markers suggests that the inverted pendulum model of body sway is incomplete. Motion about the ankle joint was dominant only for lateral movement in the frontal plane with narrow stance widths (< 8 cm). For all other conditions most angular motion occurred between the trunk and leg. 6. The large

  7. The Effect of Continuous and Discretized Presentations of Concurrent Augmented Visual Biofeedback on Postural Control in Quiet Stance

    PubMed Central

    D’Anna, Carmen; Schmid, Maurizio; Bibbo, Daniele; Bertollo, Maurizio; Comani, Silvia; Conforto, Silvia

    2015-01-01

    The purpose of this study was to evaluate the effect of a continuous and a discretized Visual Biofeedback (VBF) on balance performance in upright stance. The coordinates of the Centre of Pressure (CoP), extracted from a force plate, were processed in real-time to implement the two VBFs, administered to two groups of 12 healthy participants. In the first group, a representation of the CoP was continuously shown, while in the second group, the discretized VBF was provided at an irregular frequency (that depended on the subject's performance) by displaying one out of a set of five different emoticons, each corresponding to a specific area covered by the current position of the CoP. In the first case, participants were asked to maintain a white spot within a given square area, whereas in the second case they were asked to keep the smiling emoticon on. Trials with no VBF were administered as control. The effect of the two VBFs on balance was studied through classical postural parameters and a subset of stabilogram diffusion coefficients. To quantify the amount of time spent in stable conditions, the percentage of time during which the CoP was inside the stability area was calculated. Both VBFs improved balance maintainance as compared to the absence of any VBF. As compared to the continuous VBF, in the discretized VBF a significant decrease of sway path, diffusion and Hurst coefficients was found. These results seem to indicate that a discretized VBF favours a more natural postural behaviour by promoting a natural intermittent postural control strategy. PMID:26196518

  8. Knowing When to Doubt: Developing a Critical Stance When Learning From Others

    PubMed Central

    Mills, Candice M.

    2013-01-01

    Children may be biased towards accepting information as true, but the fact remains that children are exposed to misinformation from many sources, and mastering the intricacies of doubt is necessary. The current article examines this issue, focusing on understanding developmental changes and consistencies in children’s ability to take a critical stance towards information. Research is reviewed on children’s ability to detect ignorance, inaccuracy, incompetence, deception, and distortion. Particular emphasis is placed on what this research indicates about how children are reasoning about when to trust and when to doubt. The remainder of the article proposes a framework to evaluate preexisting research and encourage further research, closing with a discussion of several other overarching questions that need to be considered in order to develop a model to explain developmental, individual, and situational differences in children’s ability to evaluate information. PMID:22889395

  9. Assessment of AK (Above Knee) Prosthesis with Different Ankle Assembly Using GRF Pattern in Stance Phase

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Min; Kim, Sung-Jae; Bae, Ha-Suk

    In this study, ground reaction force (GRF), absolute symmetry index (ASI) and coefficient of variation (CV) of fixed, single-axis and multi-axis prosthetic ankle assemblies were investigated by biomechanical evaluation of above knee amputees. In the experiments, 37 normal male volunteers, two male and two female Above Knee (AK) amputees GRF data were tested with fixed, single-axis and multi-axis prosthetic ankle assembly. A gait analysis was carried out to derive the ratio of GRF to weight as the percentage of total stance phase for ten points. The results showed that fixed-axis ankle assembly was superior to other two ankle assemblies for forwarding and braking forces. Multi-axis ankle was relatively superior to other two ankle assemblies for gait balancing and movement of the mass center. Single-axis ankle was relatively superior to the other two ankle assemblies for CV and ASI of GRF.

  10. Amputee walking training: a preliminary study of biomechanical measurements of stance and balance.

    PubMed

    Summers, G D; Morrison, J D; Cochrane, G M

    1988-01-01

    Biomechanical parameters of stance and balance were recorded in ten unilateral lower limb amputees at the beginning and end of walking training. Measurements were carried out using a Double Video Forceplate (DVF), a machine developed at University College, London, Bioengineering Centre, Roehampton. During free standing on the DVF there was a mean increase in weight-bearing under the prosthetic foot from 32% body weight (1st session) to 41% body weight (final session), p less than 0.01. Maximum weight-bearing during leaning as far as possible onto the prosthesis increased from a mean of 54% body weight to 63% body weight, p less than 0.01. These simple measurements of weight distribution between the feet can be of value during walking training to monitor progress and can accurately record improvement for research purposes. PMID:3391935

  11. Recovery from a Simulated Fall and Quiet Stance Stability After Long-Duration Space Flight

    NASA Technical Reports Server (NTRS)

    Kofman, I. S.; Reschke, M. F.; Cerisano, J. M.; Fisher, E. A.; May-Phillips, T. R.; Rukavishnikov, I. V.; Kitov, V. V.; Lysova, N. Yu; Lee, S. M. C.; Stenger, M. B.; Bloomberg, J. J.; Mulavara, A. P.; Tomilovskaya, E. S.; Kozlovskaya, I. B.

    2016-01-01

    Most of the ISS crew members who attempted the demanding RFF task within1-5 hours after landing were able to complete it and perform the remaining PFT tasks. This finding was important as it allowed us to transition from PFT to the full up Field Test study which includes all of PFT and several additional objectives. Long-duration spaceflight impairs crewmembers' locomotion and balance functions, which will significantly limit their abilities to perform complex tasks during the early adaptation period. Crewmember safety may also be affected if they have to spend additional 10-15 seconds to get up during an emergency egress, for example. Performance of the RFF task (both the transition and quiet stance parts) improves at a fast rate during the first day after flight. We believe that the PFT tasks performed by the crewmembers, actually accelerate the recovery of their sensorimotor function. Additional data mining and analysis will need to be conducted to confirm this hypothesis

  12. Feet distance and static postural balance: implication on the role of natural stance.

    PubMed

    Kim, Ji-Won; Kwon, Yuri; Jeon, Hyung-Min; Bang, Min-Jung; Jun, Jae-Hoon; Eom, Gwang-Moon; Lim, Do-Hyung

    2014-01-01

    The purpose of this study was to investigate 1) the effect of feet distance on static postural balance and 2) the location of natural feet distance and its possible role in the relationship of feet distance and postural balance. Static balance tests were performed on a force platform for 100 s with six different feet distances (0, 5, 10, 15, 20, 25 cm). Measures of postural balance included mean amplitude of horizontal ground reaction force (GRF) as well as the mean distance and velocity of the center of pressure (COP). All measures were discomposed into anterioposterior and mediolateral directions. ANOVA and post-hoc comparison were performed for all measures with feet distance as an independent factor. Also measured was the feet distance at the natural stance preferred by each subject. All measures significantly varied with feet distance (p<0.001). Mean distance of COP showed monotonic decrease with feet distance. Mean amplitude of horizontal GRF as well as mean velocity of COP showed U-shaped pattern (decrease followed by increase) with the minimum at the feet distance of 15 cm or 20 cm, near which the natural feet distance of 16.5 (SD 3.8) cm was located. COP is regarded to be an approximation of the center of mass (hence the resultant performance of postural control) in an inverted pendulum model with the horizontal GRF ignored. On the other hand, horizontal GRF is the direct cause of horizontal acceleration of a center of mass. The present result on horizontal GRF shows that the effort of postural control is minimized around the feet distance of natural standing and implies why the natural stance is preferred. PMID:25226972

  13. A longitudinal study of impact and early stance loads during gait following arthroscopic partial meniscectomy.

    PubMed

    Hall, Michelle; Wrigley, Tim V; Metcalf, Ben R; Hinman, Rana S; Dempsey, Alasdair R; Mills, Peter M; Cicuttini, Flavia M; Lloyd, David G; Bennell, Kim L

    2014-09-22

    People following arthroscopic partial medial meniscectomy (APM) are at increased risk of developing knee osteoarthritis. High impact loading and peak loading early in the stance phase of gait may play a role in the pathogenesis of knee osteoarthritis. This was a secondary analysis of longitudinal data to investigate loading-related indices at baseline in an APM group (3 months post-surgery) and a healthy control group, and again 2 years later (follow-up). At baseline, 82 participants with medial APM and 38 healthy controls were assessed, with 66 and 23 re-assessed at follow-up, respectively. Outcome measures included: (i) heel strike transient (HST) presence and magnitude, (ii) maximum loading rate, (iii) peak vertical force (Fz) during early stance. At baseline, maximum loading rate was lower in the operated leg (APM) and non-operated leg (non-APM leg) compared to controls (p ≤ 0.03) and peak Fz was lower in the APM leg compared to non-APM leg (p ≤ 0.01). Over 2 years, peak Fz increased in the APM leg compared to the non-APM leg and controls (p ≤ 0.01). Following recent APM, people may adapt their gait to protect the operated knee from excessive loads, as evidenced by a lower maximum loading rate in the APM leg compared to controls, and a reduced peak Fz in the APM leg compared to the non-APM leg. No differences at follow-up may suggest an eventual return to more typical gait. However, the increase in peak Fz in the APM leg may be of concern for long-term joint health given the compromised function of the meniscus. PMID:25169661

  14. Coordinated, multi-joint, fatigue-resistant feline stance produced with intrafascicular hind limb nerve stimulation

    NASA Astrophysics Data System (ADS)

    Normann, R. A.; Dowden, B. R.; Frankel, M. A.; Wilder, A. M.; Hiatt, S. D.; Ledbetter, N. M.; Warren, D. A.; Clark, G. A.

    2012-04-01

    The production of graceful skeletal movements requires coordinated activation of multiple muscles that produce torques around multiple joints. The work described herein is focused on one such movement, stance, that requires coordinated activation of extensor muscles acting around the hip, knee and ankle joints. The forces evoked in these muscles by external stimulation all have a complex dependence on muscle length and shortening velocities, and some of these muscles are biarticular. In order to recreate sit-to-stand maneuvers in the anesthetized feline, we excited the hind limb musculature using intrafascicular multielectrode stimulation (IFMS) of the muscular branch of the sciatic nerve, the femoral nerve and the main branch of the sciatic nerve. Stimulation was achieved with either acutely or chronically implanted Utah Slanted Electrode Arrays (USEAs) via subsets of electrodes (1) that activated motor units in the extensor muscles of the hip, knee and ankle joints, (2) that were able to evoke large extension forces and (3) that manifested minimal coactivation of the targeted motor units. Three hind limb force-generation strategies were investigated, including sequential activation of independent motor units to increase force, and interleaved or simultaneous IFMS of three sets of six or more USEA electrodes that excited the hip, knee and ankle extensors. All force-generation strategies evoked stance, but the interleaved IFMS strategy also reduced muscle fatigue produced by repeated sit-to-stand maneuvers compared with fatigue produced by simultaneous activation of different motor neuron pools. These results demonstrate the use of interleaved IFMS as a means to recreate coordinated, fatigue-resistant multi-joint muscle forces in the unilateral hind limb. This muscle activation paradigm could provide a promising neuroprosthetic approach for the restoration of sit-to-stand transitions in individuals who are paralyzed by spinal cord injury, stroke or disease.

  15. Postflight Quiet Stance Stability of Astronauts Following Recovery From a Simulated Fall

    NASA Technical Reports Server (NTRS)

    Reschke, M. F.; Kofman, I. S.; Fisher, E. A.; Cerisano, J. M.; Lawrence, E. L.; Peters, B. T.; Harm, D. L.; Kulecz, W.; Mulavara, A. P.; Fiedler, M. J.; Bloomberg, J. J.

    2010-01-01

    INTRODUCTION: Astronauts returning from space flight universally present with postural ataxia. Throughout the Space Shuttle Program, measurement of ataxia has concentrated on sway in the anterior-posterior plane. Implementation of an interdisciplinary pre- and postflight study (Functional Task Test, FTT) designed to evaluate both astronaut postflight functional performance and related physiological changes has allowed the investigation of postural instability by characterizing dynamic stabilographic sway patterns. METHODS: Six astronauts from short-duration (Shuttle) and three from long-duration (ISS) flights were required to recover from a simulated fall. Subjects with eyes open, wearing running shoes lay prone on the floor for 2 minutes and then quickly stood up, maintained a quiet stance for 3 minutes, arms relaxed along the side of the body, and feet comfortably placed on the force plate. Crewmembers were tested twice before flight, on landing day (Shuttle only), and 1, 6, and 30 days after flight. Anterior-posterior (AP) and medial-lateral (ML) center-of-pressure (COP) coordinates were calculated from the ground reaction forces collected at 500 Hz. The 3-minute quiet stance trial was broken into three 1-minute segments for stabilogram diffusion analysis. A mean sway speed (rate of change of COP displacement) was also calculated as an additional postural stability parameter. RESULTS/CONCLUSION: While there was considerable variation, most of crewmembers tested exhibited increased stochastic activity evidenced by larger short-term COP diffusion coefficients postflight in both the AP and ML planes, suggesting significant changes in postural control mechanisms, particularly control of lower limb muscle function. As expected, postural instability of ISS astronauts on the first day postflight was similar to that of Shuttle crewmembers on landing day. Recoveries of stochastic activity and mean sway speed to baseline levels were typically observed by the 30th day

  16. A simple new device to examine human stance: the totter-slab.

    PubMed

    Roth, Robin; Wank, Veit; Müller, Otto; Hochwald, Harald; Günther, Michael

    2010-02-01

    This article describes a new measuring device to investigate balancing strategies of human stance: the totter-slab, i.e., a standing plate suspended with steel cables to hooks on a steel frame. First, we analysed the physical properties of the device by recording free oscillations under different conditions [varying amplitude, mass and centre of mass (COM) height]. This allowed us to determine the eigenfrequency f and the damping coefficient D<1 Ns/m for each trial. The trials showed that the measured damped eigenfrequency of f is approximately 0.63 Hz is barely dependent on the mass loaded. The ratio D/M is approximately 0.015 1/s is a constant almost independent of the different conditions. Furthermore, we determined the stiffnesses of the suspending cables and their suspension points to check for potential energy storage capacity of the totter-slab. We found that the totter-slab is a useful, well-defined, reliable and developable measuring device for different non-rigid-ground stance conditions. In a second part of the investigation, we compared the frequency spectra of six subjects balancing on the totter-slab with their spectra while standing quietly on a force plate fixed to the ground. The totter-slab spectra showed two distinct, dominant peak regions at approximately 0.3 and 1.1 Hz. This finding enforces the double inverted pendulum to be an adequate model particularly for balancing on the totter-slab. Compared with the firm ground condition, these two peak regions were more pronounced when balancing on the totter-slab. However, there is a variety of frequencies in the region 0.2...1.5 Hz specific for an individual subject in both balancing conditions. PMID:20128743

  17. The role of vestibular and somatosensory systems in intersegmental control of upright stance

    PubMed Central

    Creath, Rob; Kiemel, Tim; Horak, Fay; Jeka, John J.

    2009-01-01

    Upright stance was perturbed using sinusoidal platform rotations to see how vestibular and somatosensory information are used to control segment and intersegmental dynamics in subjects with bilateral vestibular loss (BVL) and healthy controls (C). Subjects stood with eyes closed on a rotating platform (±1.2°) for frequencies ranging from 0.01–0.4 Hz in the presence and absence of light fingertip touch. Trunk movement relative to the platform of BVLs was higher than Cs at higher platform frequencies whereas leg movement relative to the platform was similar for both groups. With the addition of light touch, both groups showed similar trunk and leg segment movement relative to the platform. Trunk-leg coordination was in-phase for frequencies below 1 Hz and anti-phase above 1 Hz. Interestingly, BVLs showed evidence of a “legs-leading-trunk” relationship in the shift from in-phase to anti-phase around 1 Hz. Controls showed no preference for either segment to lead the coordinative shift from in- to anti-phase. The results suggest that the balance instability of BVL subjects stems from high variability of the trunk, rather than the legs. The high trunk variability may emerge from the “legs-leading” intersegmental relationship upon which BVLs rely. Because BVLs derive information about self-orientation primarily from the support surface when their eyes are closed, the legs initiate the shift to anti-phase trunk-leg coordination that is necessary for stable upright stance control. Higher trunk variability suggests that this strategy results in lower overall postural stability. Light touch substitutes for vestibular information, leading to lower trunk variability along with a trunk-leg phase shift similar to controls, without a preference for either segment to lead the shift. The results suggest that vestibulospinal control acts primarily to stabilize the trunk in space and to facilitate intersegmental dynamics. PMID:18776597

  18. Government Stance and Internal Diversity of Protest: A Comparative Study of Protest against the War in Iraq in Eight Countries

    ERIC Educational Resources Information Center

    Walgrave, Stefaan; Verhulst, Joris

    2009-01-01

    This study tackles the question to what extent the composition of protest events is determined by the stance of governments. Established contextual theories do not formulate propositions on how context affects individual protesters. The article engages in empirically testing whether the macro-context affects the internal diversity of the crowds…

  19. Reading Sacred Texts in the Classroom: The Alignment between Students and Their Teacher's Interpretive Stances When Reading the Hebrew Bible

    ERIC Educational Resources Information Center

    Hassenfeld, Ziva R.

    2016-01-01

    This study investigated the voices of students interpreting Hebrew Bible texts in one fourth-grade classroom. Through think-alouds on the Biblical text with each student, exit interviews, teacher interviews, and classroom observations, this study found that those students whose interpretive stances were more aligned with the teacher's were given…

  20. Control of propulsion and body lift during the first two stances of sprint running: a simulation study.

    PubMed

    Debaere, Sofie; Delecluse, Christophe; Aerenhouts, Dirk; Hagman, Friso; Jonkers, Ilse

    2015-01-01

    The aim of this study was to relate the contribution of lower limb joint moments and individual muscle forces to the body centre of mass (COM) vertical and horizontal acceleration during the initial two steps of sprint running. Start performance of seven well-trained sprinters was recorded using an optoelectronic motion analysis system and two force plates. Participant-specific torque-driven and muscle-driven simulations were conducted in OpenSim to quantify, respectively, the contributions of the individual joints and muscles to body propulsion and lift. The ankle is the major contributor to both actions during the first two stances, with an even larger contribution in the second compared to the first stance. Biarticular gastrocnemius is the main muscle contributor to propulsion in the second stance. The contribution of the hip and knee depends highly on the position of the athlete: During the first stance, where the athlete runs in a forward bending position, the knee contributes primarily to body lift and the hip contributes to propulsion and body lift. In conclusion, a small increase in ankle power generation seems to affect the body COM acceleration, whereas increases in hip and knee power generation tend to affect acceleration less. PMID:25798644

  1. Study of stress variations in single-stance and sideways fall using image-based finite element analysis.

    PubMed

    Faisal, Tanvir R; Luo, Yunhua

    2016-05-12

    Image-based finite element analysis (FEA) has been considered an effective computational tool to predict hip fracture risk. The patient specific FEA gives an insight into the inclusive effect of three-dimensional (3D) complex bone geometry, and the distribution of inhomogeneous isotropic material properties in conjunction with loading conditions. The neck region of a femur is primarily the weakest in which fracture is likely to happen, when someone falls. A sideways fall results in the development of greater tensile and compressive stresses, respectively, in the inferior and superior aspects of the femoral neck, whereas the state of stress is reversed in usual gait or stance configuration. Herein, the variations of stresses have been investigated at the femoral neck region considering both single-stance and sideways fall. Finite element models of ten human femora have been generated using Quantitative Computed Tomography (QCT) scan datasets and have been simulated with an equal magnitude of load applied to the aforementioned configurations. Fracture risk indicator, defined as the ratio of the maximum compressive or tensile stress computed at the superior and inferior surfaces to the corresponding yield stress, has been used in this work to measure the variations of fracture risk between single-stance and sideways fall. The average variations of the fracture risk indicators between the fall and stance are at least 24.3% and 8% at the superior and inferior surfaces, respectively. The differences may interpret why sideways fall is more dangerous for the elderly people, causing hip fracture. PMID:27175463

  2. Long-Term Adaptations to Unexpected Surface Perturbations: Postural Control During Stance and Gait in Train Conductors.

    PubMed

    Baumgart, Christian; Hoppe, Matthias Wilhelm; Freiwald, Jürgen

    2016-01-01

    The authors aimed to evaluate the differences in postural control during stance and gait between train conductors and controls. Twenty-one train conductors and 21 office workers performed 6 unilateral and bilateral balance tests on stable and unstable surfaces as well as a gait analysis. In the balance tests, the mean velocity of the center of pressure and unstable surface was measured. In the bilateral balance tests the selected stance width was measured. During gait the length, width, frequency, and velocity of the steps were calculated from the ground reaction forces. Train conductors showed a significantly greater step width during gait (15.4 ± 4.7 vs. 13.0 ± 3.4 cm; p = .035) and stance width during the bilateral stance on the unstable surface (21.0 ± 5.1 vs. 17.8 ± 3.7 cm; p = .026) than the office workers, while no differences were revealed in balance variables. The revealed differences between train conductors and office workers may represent task-specific feedforward control strategies, which increase the base of support and may be helpful to resist unexpected perturbations in trains. PMID:26730891

  3. Powerful Voices and Pens: Developing Critical Stance with Adolescent Literacy in Content-Area Pre-Service Teacher Education

    ERIC Educational Resources Information Center

    Soares, Lina B.

    2012-01-01

    This practitioner-research study investigated the effect critical literacy has on content area preservice teachers' abilities (N = 14) to perceive the sociocultural influences in text. The study further investigated how content area pre-service teachers engage in critical stance during situated reading practices that centered on discussions of…

  4. Epistemological and Interpersonal Stance in a Data Description Task: Findings from a Discipline-Specific Learner Corpus

    ERIC Educational Resources Information Center

    Wharton, Sue

    2012-01-01

    This article examines the stance options used by writers responding to a data description task in the discipline of Statistics. Based on a small learner corpus, it uses inductive qualitative content analysis to explore both the content propositions that students included in their writing, and the ways in which they expressed evaluative stance…

  5. Taking an Evaluative Stance to Decision-Making about Professional Development Options in Early Childhood Education and Care

    ERIC Educational Resources Information Center

    Brownlee, Joanne Lunn; Sumsion, Jennifer; Irvine, Susan; Berthelsen, Donna; Farrell, Ann; Walsh, Kerryann; Ryan, Sharon; Mulhearn, Gerry

    2015-01-01

    This article builds on our ongoing work in conceptualising an "evaluative stance" framework to assist in understanding how leaders in the field of early childhood education and care (ECEC) make decisions about the selection of professional development options for themselves and their staff. It introduces the notion that evaluative…

  6. The Transformative Power of Taking an Inquiry Stance on Practice: Practitioner Research as Narrative and Counter-Narrative

    ERIC Educational Resources Information Center

    Ravitch, Sharon M.

    2014-01-01

    Within the ever-developing, intersecting, and overlapping contexts of globalization, top-down policy, mandates, and standardization of public and higher education, many conceptualize and position practitioner research as a powerful stance and a tool of social, communal, and educational transformation, a set of methodological processes that…

  7. Participation in Peer Response as Activity: An Examination of Peer Response Stances from an Activity Theory Perspective

    ERIC Educational Resources Information Center

    Zhu, Wei; Mitchell, Deborah A.

    2012-01-01

    This article reports a case study that examined English as a Second Language students' peer response stances from an activity theory perspective. More specifically, the study was guided by the constructs of activity and motive/object in Leont'ev's theory. Multiple sources of data were collected from two native Spanish-speaking students enrolled in…

  8. Segment coupling and coordination variability analyses of the roundhouse kick in taekwondo relative to the initial stance position.

    PubMed

    Estevan, Isaac; Freedman Silvernail, Julia; Jandacka, Daniel; Falco, Coral

    2016-09-01

    The initial stance position (ISP) has been observed as a factor affecting the execution technique during taekwondo kicks. In the present study, authors aimed to analyse a roundhouse kick to the chest by measuring movement coordination and the variability of coordination and comparing this across the different ISP (0°, 45° and 90°). Eight experienced taekwondo athletes performed consecutive kicking trials in random order from every of the three relative positions. The execution was divided into three phases (stance, first swing and second swing phase). A motion capture system was used to measure athletes' angular displacement of pelvis and thigh. A modified vector coding technique was used to quantify the coordination of the segments which contributed to the overall movement. The variability of this coordination (CV) for each ISP was also calculated. Comparative analysis showed that during the stance phase in the transverse plane, athletes coordinated movement of the trunk and thigh with a higher frequency of in-phase and lower frequency of exclusive thigh rotation in the 0° stance than the 90° stance position (P < 0.05). CV was also influenced by the different ISP. During the first swing and the majority of the second swing phase, predominant in-phase coordination of the pelvis and thigh was observed. Including exercises that require in-phase movement could not only help athletes to acquire coordination stability but also efficiency. The existence of a constraint such as ISP implies an increase of the variability when the athletes have to kick from ISP they are not used to adopt (i.e., 0° and 90° ISP) as an evidence of adaptability in the athletes' execution technique. PMID:26805571

  9. Kinematics and Kinetics of Squat and Deadlift Exercises with Varying Stance Widths

    NASA Technical Reports Server (NTRS)

    DeWitt, John K.; Fincke, Renita S.; Logan, Rachel L.

    2011-01-01

    The primary motion of squat and deadlift exercise involves flexion and extension of the hips, knees, and ankles, but each exercise can be performed with variations in stance width. These variations may result in differing kinematics and ground reaction forces (GRF), which may in turn affect joint loading. PURPOSE: The purpose of this investigation was to compare ankle, knee, and hip kinematics and kinetics of normal squat (NS), wide-stance squat (WS), normal deadlift (ND), and sumo deadlift (SD). We hypothesized that hip joint kinematics and work at each joint would differ between exercise variations. METHODS: Six subjects (3 m/3 f; 70.0 plus or minus 13.7 kg; 168 plus or minus 9.9 cm) performed each lift in normal gravity on the ground-based version of the Advanced Resistive Exercise Device (ARED) used on the International Space Station. The ARED provided resistance with a combination vacuum tube/flywheel mechanism designed to replicate the gravitational and inertial forces of free weights. Subjects completed each lift with their 10-repetition maximum load. Kinematic data were collected at 250 Hz by a 12-camera motion-capture system (Smart-D, BTS Bioengineering, Milan, Italy), and GRF data were collected at 1000 Hz with independent force platforms for each leg (Model 9261, Kistler Instruments AG, Winterhur, Switzerland). All data were captured simultaneously on a single workstation. The right leg of a single lift for each motion was analyzed. Modeling software (OpenSim 2.2.0, Simbios, Palo Alto, CA) determined joint kinematics and net positive and negative work at each lower extremity joint. Total work was found as the sum of work across all joints and was normalized by system mass. Effect sizes and their 95% confidence intervals were computed between conditions. RESULTS: Peak GRF were similar for each lift. There were no differences between conditions in hip flexion range of motion (ROM). For hip adduction ROM, there were no differences between the NS, WS, and SD

  10. Multi-muscle control during bipedal stance: an EMG-EMG analysis approach.

    PubMed

    Danna-Dos-Santos, Alessander; Boonstra, Tjeerd W; Degani, Adriana M; Cardoso, Vinicius S; Magalhaes, Alessandra T; Mochizuki, Luis; Leonard, Charles T

    2014-01-01

    Posture and postural reactions to mechanical perturbations require the harmonic modulation of the activity of multiple muscles. This precision can become suboptimal in the presence of neuromuscular disorders and result in higher fall risk and associated levels of comorbidity. This study was designed to investigate neurophysiological principles related to the generation and distribution of inputs to skeletal muscles previously recognized as a synergistic group. Specifically, we investigated the current hypothesis that correlated neural inputs, as measured by intermuscular coherence, are the mechanism used by the central nervous system to coordinate the formation of postural muscle synergies. This hypothesis was investigated by analyzing the strength and distribution of correlated neural inputs to postural muscles during the execution of a quiet stance task. Nine participants, 4 females and 5 males, mean age 29.2 years old (±6.1 SD), performed the task of standing while holding a 5-kg barbell in front of their bodies at chest level. Subjects were asked to maintain a standing position for 10 s while the activity of three postural muscles was recorded by surface electrodes: soleus (SOL), biceps femoris (BF), and lumbar erector spinae (ERE). EMG-EMG coherence was estimated for three muscle pairs (SOL/BF, SOL/ERE, and BF/ERE). Our choice of studying these muscles was made based on the fact that they have been reported as components of a functional (synergistic) muscle group that emerges during the execution of bipedal stance. In addition, an isometric contraction can be easily induced in this muscle group by simply adding a weight to the body's anterior aspect. The experimental condition elicited a significant increase in muscle activation levels for all three muscles (p < 0.01 for all muscles). EMG-EMG coherence analysis revealed significant coherence within two distinct frequency bands, 0-5 and 5-20 Hz. Significant coherence within the later frequency band was also

  11. Dynamics of quiet human stance: computer simulations of a triple inverted pendulum model.

    PubMed

    Günther, Michael; Wagner, Heiko

    2016-01-01

    For decades, the biomechanical description of quiet human stance has been dominated by the single inverted pendulum (SIP) paradigm. However, in the past few years, the SIP model family has been falsified as an explanatory approach. Double inverted pendulum models have recently proven to be inappropriate. Human topology with three major leg joints suggests in a natural way to examine triple inverted pendulum (TIP) models as an appropriate approach. In this study, we focused on formulating a TIP model that can synthesise stable balancing attractors based on minimalistic sensor information and actuation complexity. The simulated TIP oscillation amplitudes are realistic in vertical direction. Along with the horizontal ankle, knee and hip positions, though, all simulated joint angle amplitudes still exceed the measured ones about threefold. It is likely that they could be eventually brought down to the physiological range by using more sensor information. The TIP systems' eigenfrequency spectra come out as another major result. The eigenfrequencies spread across about 0.1 Hz...20 Hz. Our main result is that joint stiffnesses can be reduced even below statically required values by using an active hip torque balancing strategy. When reducing mono- and bi-articular stiffnesses further down to levels threatening dynamic stability, the spectra indicate a change from torus-like (stable) to strange (chaotic) attractors. Spectra of measured ground reaction forces appear to be strange-attractor-like. We would conclude that TIP models are a suitable starting point to examine more deeply the dynamic character of and the essential structural properties behind quiet human stance. Abbreviations and technical terms Inverted pendulum body exposed to gravity and pivoting in a joint around position of unstable equilibrium (operating point) SIP single inverted pendulum: one rigid body pivoting around fixation to the ground (external joint) DIP double inverted pendulum: two bodies

  12. Comparison of ISO Standard and TKR Patient Axial Force Profiles during the Stance Phase of Gait

    PubMed Central

    Lundberg, Hannah J.; Ngai, Valentina; Wimmer, Markus A.

    2012-01-01

    Preclinical endurance testing of total knee replacements (TKRs) is performed using International Organization for Standardization (ISO) load and motion protocols. The standards are based on data from normal subjects and may not sufficiently mimic in vivo implant conditions. In this study, a mathematical model was used to calculate the axial force profile of 30 TKR patients with two current implant types, 22 with NexGen and eight with Miller-Galante II Cruciate-Retaining TKRs, and statistically compare the axial force specified by the ISO standard to the TKR patients. Significant differences were found between the axial forces of both groups of TKR patients and the ISO standard at local maxima and minima points in the first half of stance. The force impulse (area under the axial force curve, representing cumulative loading) was smaller for the ISO standard than the TKR patients, but only for those with NexGen implants. Waveform analysis using the coefficient of multiple correlation showed that the ISO and TKR patient axial force profiles were similar. The combined effect of ISO standard compressive load and motion differences from TKR patients could explain some of the differences between the wear scars on retrieved tibial components and those tested in total joint simulators. PMID:22558837

  13. Adopting the ritual stance: The role of opacity and context in ritual and everyday actions.

    PubMed

    Kapitány, Rohan; Nielsen, Mark

    2015-12-01

    Rituals are a pervasive and ubiquitous aspect of human culture, but when we naïvely observe an opaque set of ritual actions, how do we come to understand its significance? To investigate this, across two experiments we manipulated the degree to which actions were ritualistic or ordinary, and whether or not they were accompanied with context. In Experiment 1, 474 adult participants were presented with videos of novel rituals (causally opaque actions) or control actions (causally transparent) performed on a set of objects accompanied with neutral-valance written context. Experiment 2 presented the same video stimuli but with negative and aversive written context. In both experiments ritualized objects were rated as physically unchanged, but more 'special' and more 'desirable' than objects subjected to control actions, with context amplifying this effect. Results are discussed with reference to the Ritual Stance and the Social-Action hypothesis. Implications for both theories are discussed, as are methodological concerns regarding the empirical investigation of ritual cognition. We argue that causally opaque ritual actions guide the behavior of naïve viewers because such actions are perceived as socially normative, rather than with reference to supernatural intervention or causation. PMID:26298423

  14. Enhancing stance phase propulsion during level walking by combining FES with a powered exoskeleton for persons with paraplegia.

    PubMed

    Ha, Kevin H; Quintero, Hugo A; Farris, Ryan J; Goldfarb, Michael

    2012-01-01

    This paper describes the design and implementation of a cooperative controller that combines functional electrical stimulation (FES) with a powered lower limb exoskeleton to provide enhanced hip extension during the stance phase of walking in persons with paraplegia. The controller utilizes two sources of actuation: the electric motors of the powered exoskeleton and the user's machine (FSM), a set of FES. It consists of a finite-state machine (FSM), a set of proportional-derivative (PD) controllers for the exoskeleton and a cycle-to-cycle adaptive controller for muscle stimulation. Level ground walking is conducted on a single subject with complete T10 paraplegia. Results show a 34% reduction in electrical power requirements at the hip joints during the stance phase of the gait cycle with the cooperative controller compared to using electric motors alone. PMID:23365900

  15. Enhancing Stance Phase Propulsion during Level Walking by Combining FES with a Powered Exoskeleton for Persons with Paraplegia*

    PubMed Central

    Ha, Kevin H.; Quintero, Hugo A.; Farris, Ryan J.; Goldfarb, Michael

    2013-01-01

    This paper describes the design and implementation of a cooperative controller that combines functional electrical stimulation (FES) with a powered lower limb exoskeleton to provide enhanced hip extension during the stance phase of walking in persons with paraplegia. The controller utilizes two sources of actuation: the electric motors of the powered exoskeleton and the user’s hamstrings activated by FES. It consists of a finite-state machine (FSM), a set of proportional-derivative (PD) controllers for the exoskeleton and a cycle-to-cycle adaptive controller for muscle stimulation. Level ground walking is conducted on a single subject with complete T10 paraplegia. Results show a 34% reduction in electrical power requirements at the hip joints during the stance phase of the gait cycle with the cooperative controller compared to using electric motors alone. PMID:23365900

  16. Coordination of the head with respect to the trunk and pelvis in the roll and pitch planes during quiet stance.

    PubMed

    Honegger, F; van Spijker, G J; Allum, J H J

    2012-06-28

    This study examined the relationship between head and trunk sway during quiet stance and compared this relationship with that of the pelvis to the trunk. Sixteen younger and 14 elderly subjects participated, performing four different sensory tasks: standing quietly on a firm or foam support surface, with eyes open or closed. Roll and pitch angular velocities were recorded with six body-worn gyroscopes; a set of two mounted at the upper trunk, an identical set at the hips, and another set on a head band. Angle correlation analysis was performed in three frequency bands: below 0.7 Hz (LP), above 3 Hz (HP) and in between (BP) using the integrated angle velocity signals. Angular velocities were spectrally analysed. Greater head than trunk motion was observed in angle correlations, power spectral density (PSD) ratios, and transfer functions (TFs). Head on trunk motion could be divided for all sensory conditions into a low-frequency (<0.7 Hz) "head locked to trunk" inverted pendulum mode, a mid-frequency (ca. 3 Hz), resonant mode, and a slightly anti-phasic head motion on stabilised trunk, high-frequency (>3 Hz) mode. There was coherent motion between head and trunk but not between head and pelvis. Trunk and pelvis data were consistent with previously reported in-phase and anti-phase movements between these segments. Significant age differences were not found. These data indicate that during quiet stance body motion increases in the order of pelvis, trunk, head and quiet stance involves control of at least two separate links: trunk on pelvis and head on trunk dominated by head resonance. The head is locked to the trunk for low-frequency motion possibly because motion is just supra-vestibular threshold. The head is not stabilised in space during stance, rather the pelvis is. PMID:22521818

  17. Balance in single-limb stance after surgically treated ankle fractures: a 14-month follow-up

    PubMed Central

    Nilsson, Gertrud; Ageberg, Eva; Ekdahl, Charlotte; Eneroth, Magnus

    2006-01-01

    Background The maintenance of postural control is fundamental for different types of physical activity. This can be measured by having subjects stand on one leg on a force plate. Many studies assessing standing balance have previously been carried out in patients with ankle ligament injuries but not in patients with ankle fractures. The aim of this study was to evaluate whether patients operated on because of an ankle fracture had impaired postural control compared to an uninjured age- and gender-matched control group. Methods Fifty-four individuals (patients) operated on because of an ankle fracture were examined 14 months postoperatively. Muscle strength, ankle mobility, and single-limb stance on a force-platform were measured. Average speed of centre of pressure movements and number of movements exceeding 10 mm from the mean value of centre of pressure were registered in the frontal and sagittal planes on a force-platform. Fifty-four age- and gender-matched uninjured individuals (controls) were examined in the single-limb stance test only. The paired Student t-test was used for comparisons between patients' injured and uninjured legs and between side-matched legs within the controls. The independent Student t-test was used for comparisons between patients and controls. The Chi-square test, and when applicable, Fisher's exact test were used for comparisons between groups. Multiple logistic regression was performed to identify factors associated with belonging to the group unable to complete the single-limb stance test on the force-platform. Results Fourteen of the 54 patients (26%) did not manage to complete the single-limb stance test on the force-platform, whereas all controls managed this (p < 0.001). Age over 45 years was the only factor significantly associated with not managing the test. When not adjusted for age, decreased strength in the ankle plantar flexors and dorsiflexors was significantly associated with not managing the test. In the 40 patients who

  18. Estimation of Quasi-Stiffness of the Human Hip in the Stance Phase of Walking

    PubMed Central

    Shamaei, Kamran; Sawicki, Gregory S.; Dollar, Aaron M.

    2013-01-01

    This work presents a framework for selection of subject-specific quasi-stiffness of hip orthoses and exoskeletons, and other devices that are intended to emulate the biological performance of this joint during walking. The hip joint exhibits linear moment-angular excursion behavior in both the extension and flexion stages of the resilient loading-unloading phase that consists of terminal stance and initial swing phases. Here, we establish statistical models that can closely estimate the slope of linear fits to the moment-angle graph of the hip in this phase, termed as the quasi-stiffness of the hip. Employing an inverse dynamics analysis, we identify a series of parameters that can capture the nearly linear hip quasi-stiffnesses in the resilient loading phase. We then employ regression analysis on experimental moment-angle data of 216 gait trials across 26 human adults walking over a wide range of gait speeds (0.75–2.63 m/s) to obtain a set of general-form statistical models that estimate the hip quasi-stiffnesses using body weight and height, gait speed, and hip excursion. We show that the general-form models can closely estimate the hip quasi-stiffness in the extension (R2 = 92%) and flexion portions (R2 = 89%) of the resilient loading phase of the gait. We further simplify the general-form models and present a set of stature-based models that can estimate the hip quasi-stiffness for the preferred gait speed using only body weight and height with an average error of 27% for the extension stage and 37% for the flexion stage. PMID:24349136

  19. Reliability of the Achilles tendon tap reflex evoked during stance using a pendulum hammer.

    PubMed

    Mildren, Robyn L; Zaback, Martin; Adkin, Allan L; Frank, James S; Bent, Leah R

    2016-01-01

    The tendon tap reflex (T-reflex) is often evoked in relaxed muscles to assess spinal reflex circuitry. Factors contributing to reflex excitability are modulated to accommodate specific postural demands. Thus, there is a need to be able to assess this reflex in a state where spinal reflex circuitry is engaged in maintaining posture. The aim of this study was to determine whether a pendulum hammer could provide controlled stimuli to the Achilles tendon and evoke reliable muscle responses during normal stance. A second aim was to establish appropriate stimulus parameters for experimental use. Fifteen healthy young adults stood on a forceplate while taps were applied to the Achilles tendon under conditions in which postural sway was constrained (by providing centre of pressure feedback) or unconstrained (no feedback) from an invariant release angle (50°). Twelve participants repeated this testing approximately six months later. Within one experimental session, tap force and T-reflex amplitude were found to be reliable regardless of whether postural sway was constrained (tap force ICC=0.982; T-reflex ICC=0.979) or unconstrained (tap force ICC=0.968; T-reflex ICC=0.964). T-reflex amplitude was also reliable between experimental sessions (constrained ICC=0.894; unconstrained ICC=0.890). When a T-reflex recruitment curve was constructed, optimal mid-range responses were observed using a 50° release angle. These results demonstrate that reliable Achilles T-reflexes can be evoked in standing participants without the need to constrain posture. The pendulum hammer provides a simple method to allow researchers and clinicians to gather information about reflex circuitry in a state where it is involved in postural control. PMID:26454702

  20. Using Argument-Driven Inquiry to enhance students' argument sophistication when supporting a stance in the context of Socioscientific Issues

    NASA Astrophysics Data System (ADS)

    Grooms, Jonathon A.

    This quasi-experimental study assesses the extent to which the Argument-Driven Inquiry (ADI) instructional model enhances undergraduate students' abilities to generate quality arguments supporting their stance in the context of a Socioscientific Issue (SSI) as compared to students experiencing a traditional style of instruction. Enhancing the quality of undergraduate students' arguments in the context of SSI can serve as an indirect measure of their scientific literacy and their ability to make sound decisions on issues that are inherently scientific but also involve social implications. Data collected in this study suggest that the undergraduate students experiencing the ADI instruction more readily provide rationales in their arguments supporting their decisions regarding two SSI-tasks as compared to a group of undergraduate students experiencing traditional instruction. This improvement in argument quality and gain in scientific literacy was achieved despite the overall lower SSI related content knowledge of the ADI students. Furthermore, the gap between the argument quality of those students with high versus low SSI related content knowledge was closed within the ADI group, while the same gap persisted post-intervention within the traditional instruction students. The role of students' epistemological sophistication was also investigated, which showed that neither instructional strategy was effective at shifting students' epistemological sophistication toward an evaluativist stance. However, the multiplists within the ADI group were able to significantly increase the sophistication of their arguments whereas the traditional students were not. There were no differences between the quality of arguments generated by the evaluativist students with either the treatment or comparison groups. Finally, the nature of the justifications used by the students revealed that the students (both comparison and treatment groups) did not invoke science-based justifications when

  1. Gait modification strategies of trunk over left stance phase in patients with right anterior cruciate ligament deficiency

    PubMed Central

    Shi, Dongliang; Li, Nannan; Wang, Yubin; Jiang, Shuyun; Li, Jinglong; Zhu, Wenhui

    2015-01-01

    Purpose: To investigate the gait modification strategies of trunk over left stance phase in patients with right anterior cruciate ligament deficiency (ACL-D). Methods: Thirty-six patients with right ACL-D and thirty-six health subjects (control) were recruited to undergo a 3-dimensional (3D) gait analysis. Coordinate data from 26 reflective markers positioned on the body surface of participants were recorded with a 3D optical video motion capture system, as they walked on the ground, ascended and descended a custom-built staircase. Angle changes in the 3-planes under different walking conditions were analyzed. Results: There were statistically significant differences between the two groups in the trunk at the transverse plane angle in most measurements. With the walk pattern of stair descent, the trunk at all 3-plane angles, at the maximum value of the left knee sagittal/coronal/transverse plane moment, was significantly different between the two groups (P ≤ 0.03). Conclusions: Our findings suggested that special gait modification of trunk is apparent over stance of left (healthy) side in patients with right ACL-D. The results of this study may supply more insight with respect to improving the diagnosis and rehabilitation of ACL-D. This information may also be helpful for a better use of walk and stair tasks as part of a rehabilitation program and provide a safe guideline for the patients. PMID:26550279

  2. Effect of foot position on balance ability in single-leg stance with and without visual feedback.

    PubMed

    Schneiders, Anthony; Gregory, Kate; Karas, Steve; Mündermann, Annegret

    2016-06-14

    The purpose of this study was to determine the natural foot position and to quantify the effect of foot position on balance performance during single-leg stance. Forty healthy subjects participated in this study (age, 18 to 32 years; 24 female). Subjects were asked to perform single-leg balance trials on a balance force plate in their self-selected and four predetermined foot positions with their eyes open and closed. Sway distance, area and velocity were computed for each trial. There was significant interactions between visual conditions and foot position for all sway parameters (P<.001). With the eyes closed, sway parameters were greatest for the self-selected foot position compared to the other foot positions (P<.005). No differences in sway parameters between foot positions were detected for the eyes-open condition. Sway distance, area and velocity were 94%, 400% and 89% greater, respectively, for the eyes-closed than the eyes-open condition. Self-selected foot placement did not produce the most stable single-leg stance. The results of this study indicate that foot position is not important for protocols for assessing balance or for rehabilitation exercises using eyes-open conditions and that assessment protocols and rehabilitation exercises should clearly specify the foot position when using eyes-closed protocols. PMID:27156374

  3. Center of gravity motions and ankle joint stiffness control in upright undisturbed stance modeled through a fractional Brownian motion framework.

    PubMed

    Rougier, P; Caron, O

    2000-12-01

    The authors modeled the center of gravity vertical projection (CG(v)) and the difference, CP - CG(v), which, combined, constitute the center of pressure (CP) trajectory, as fractional Brownian motion in order to investigate their relative contributions and their spatiotemporal articulation. The results demonstrated that CG(v) and CP - CG(v) motions are both endowed in complementary fashion with strong stochastic and part-deterministic behaviors. In addition, if the temporal coordinates remain similar for all 3 trajectories by definition, the switch between the successive control mechanisms appears for shorter displacements for CP - CG(v) and CG(v) than for CP trajectories. Results deduced from both input (CG(v)) and muscular stiffness (CP - CG(v)) thus provide insight into the way the central nervous system regulates stance control and in particular how CG and CP - CG are controlled. PMID:11114233

  4. Restoration of Stance Phase Knee Flexion during Walking after Spinal Cord Injury using a Variable Impedance Orthosis

    PubMed Central

    Bulea, Thomas C.; Kobetic, Rudi; Triolo, Ronald. J.

    2013-01-01

    A hybrid neuroprosthesis (HNP) combines lower extremity bracing with functional neuromuscular stimulation (FNS) to restore walking function and enhance the efficiency of ambulation. This report details the development of a novel HNP containing a variable impedance knee mechanism (VIKM) capable of supporting the knee against collapse while allowing controlled stance phase knee flexion. The design of a closed loop, finite state controller for coordination of VIKM activity with FNS-driven gait is presented. The controller is verified in testing during able bodied gait. The improved functionality provided by this system has the potential to delay the onset of fatigue and to expand FNS driven gait to allow walking over uneven terrains and down stairs. PMID:22254383

  5. Gait modification strategies in trunk over right stance phase in patients with right anterior cruciate ligament deficiency.

    PubMed

    Shi, Dongliang; Li, Nannan; Wang, Yubin; Jiang, Shuyun; Lin, Jianping; Zhu, Wenhui

    2016-05-01

    This study aimed to investigate the gait modification strategies of trunk over right stance phase in patients with right anterior cruciate ligament deficiency (ACL-D). Thirty-six patients with right chronic ACL-D were recruited, as well as 36 controls. A 3D optical video motion capture system was used during gait and stair ambulation. Kinematic variables of the trunk and kinematic and kinetic variables of the knee were calculated. Patients with chronic right ACL-D exhibited many significant abnormalities compared with controls. Trunk rotation with right shoulder trailing over the right stance phase was lower in all five motion patterns (P<0.05). Compared with controls, trunk posterior lean was higher from descending stairs to walking when the knee sagittal plane moment ended (P<0.01). Trunk lateral flexion to the left was higher when ascending stairs at the start of right knee coronal plane moment (P=0.01), when descending stairs at the maximal knee coronal plane moment (P<0.01), and when descending stairs at the end of the knee coronal plane moment (P=0.03). Trunk rotation with right shoulder forward was higher at the minimal knee transverse plane moment (P<0.01) and when the knee transverse plane moment ended (P<0.01); during walking, trunk rotation with right shoulder trailing was lower at other knee moments during other walking patterns (all P<0.01). In conclusion, gait modification strategies of the trunk were apparent in patients with ACL-D. These results provide new insights about diagnosis and rehabilitation of chronic ACL-D (better use of walking and stair tasks as part of a rehabilitation program). PMID:27131179

  6. Talk and Conceptual Change at Work: Adequate Representation and Epistemic Stance in a Comparative Analysis of Statistical Consulting and Teacher Workgroups

    ERIC Educational Resources Information Center

    Hall, Rogers; Horn, Ilana Seidel

    2012-01-01

    In this article we ask how concepts that organize work in two professional disciplines change during moments of consultation, which represent concerted efforts by participants to work differently now and in the future. Our analysis compares structures of talk, the adequacy of representations of practice, and epistemic and moral stances deployed…

  7. "How Do I Do It if I Don't Like Writing?": Adolescents' Stances toward Writing across Disciplines

    ERIC Educational Resources Information Center

    Jeffery, Jill V.; Wilcox, Kristen

    2014-01-01

    This research embedded in the National Study of Writing Instruction examines higher- and lower-achieving adolescents' stances toward content-area writing through a qualitative discourse analysis of interviews with 40 students in California, Kentucky, New York, and Texas secondary schools. The study asked: (1) How do students' stances…

  8. Taking an Effective Authorial Stance in Academic Writing: Making the Linguistic Resources Explicit for L2 Writers in the Social Sciences

    ERIC Educational Resources Information Center

    Chang, Peichin; Schleppegrell, Mary

    2011-01-01

    Taking an assertive stance toward research being reviewed or reported is a challenging task for second language writers. This aspect of interpersonal meaning is especially difficult to address through direct instruction, as attention to particular grammatical and lexical choices outside of contexts of use is not enough to help students develop the…

  9. Comparison of Ball-And-Racket Impact Force in Two-Handed Backhand Stroke Stances for Different-Skill-Level Tennis Players

    PubMed Central

    Lo, Kuo-Cheng; Hsieh, Yung-Chun

    2016-01-01

    This study compared the kinetic roles of the upper extremities in racket impact force generation between the open stance (OS) and square stance (SS) for tennis players with different skill levels in two-handed backhand strokes. Twelve male tennis players were divided into an advanced group (AG) (L3-L2 skill level) and intermediate group (IG) (L7-L6 skill level), and their data were used in a three-dimensional kinetic analysis. Their motions were captured using 21 reflective markers attached to anatomic landmarks for two-handed backhand stroke motion data collection. During the acceleration phase, significant differences were not observed between both stances, but they were observed between the groups with different skill levels for the force of the upper extremities (p = 0.027). The joint forces were significantly lower in the AG than in the IG. Players performing the SS had significantly larger pronation and supination of the wrist joint moment than those in the OS (p = 0.032) during the acceleration phase, irrespective of the playing level. Higher internal rotation moment after impact was observed at each joint, particularly among young intermediate tennis players, regardless of their stance. The AG demonstrated a higher joint force and moment at every joint compared with the IG at impact. Moreover, the AG demonstrated superior stroke efficiency and effectively reduced joint moment after impact and sports injury. Key points Advanced players, regardless of open stance or square stance, have larger joint force and moment at each joint before ball impact resulting in better stroke efficiency and reduced chance of injury. Intermediate players, regardless of stance, have higher internal rotation moment at each joint instead of larger joint force as compared to advanced players before ball impact. The higher internal rotation moment will induce higher joint impact force which makes the player injury-prone. Young intermediate tennis players may want to avoid excessive

  10. Comparison of Ball-And-Racket Impact Force in Two-Handed Backhand Stroke Stances for Different-Skill-Level Tennis Players.

    PubMed

    Lo, Kuo-Cheng; Hsieh, Yung-Chun

    2016-06-01

    This study compared the kinetic roles of the upper extremities in racket impact force generation between the open stance (OS) and square stance (SS) for tennis players with different skill levels in two-handed backhand strokes. Twelve male tennis players were divided into an advanced group (AG) (L3-L2 skill level) and intermediate group (IG) (L7-L6 skill level), and their data were used in a three-dimensional kinetic analysis. Their motions were captured using 21 reflective markers attached to anatomic landmarks for two-handed backhand stroke motion data collection. During the acceleration phase, significant differences were not observed between both stances, but they were observed between the groups with different skill levels for the force of the upper extremities (p = 0.027). The joint forces were significantly lower in the AG than in the IG. Players performing the SS had significantly larger pronation and supination of the wrist joint moment than those in the OS (p = 0.032) during the acceleration phase, irrespective of the playing level. Higher internal rotation moment after impact was observed at each joint, particularly among young intermediate tennis players, regardless of their stance. The AG demonstrated a higher joint force and moment at every joint compared with the IG at impact. Moreover, the AG demonstrated superior stroke efficiency and effectively reduced joint moment after impact and sports injury. Key pointsAdvanced players, regardless of open stance or square stance, have larger joint force and moment at each joint before ball impact resulting in better stroke efficiency and reduced chance of injury.Intermediate players, regardless of stance, have higher internal rotation moment at each joint instead of larger joint force as compared to advanced players before ball impact. The higher internal rotation moment will induce higher joint impact force which makes the player injury-prone.Young intermediate tennis players may want to avoid excessive

  11. The Role of Knee Positioning and Range-of-Motion on the Closed-Stance Forehand Tennis Swing

    PubMed Central

    Nesbit, Steven M.; Serrano, Monika; Elzinga, Mike

    2008-01-01

    This paper discusses the role of knee positioning and range-of- motion on the closed-stance forehand tennis swing. The analyses of tennis swing mechanics were performed using a computer model comprised of a full-body model of a human and an inertial model of a racket. The model was driven by subject forehand swings (16 female college-level subjects) recorded with a high-speed digital motion analysis system. The study discovered that both initial knee positioning and range-of-motion were positively related to racket velocity and characteristic of more skilled players. The direct effects of knee positioning and range-of-motion on racket movement are minimal, however there are several indirect biomechanical effects on the forehand motion such as movement of the body mass center, work of the knee, hip and back joints, and the angular range-of-motion of the hips and torso. Some of these indirect effects were related to racket velocity and characteristic of more skilled players. Factors that influenced knee positioning and range-of-motion include years of playing, amount of coaching, and body style. Efforts to both increase and restrict the knee movements of the subjects resulted in substantially lower racket velocities (and other detrimental biomechanical effects) implying that there may be optimal knee positions and range-of-motion for a given subject. The most skilled subject exhibited a high degree of consistency of knee positioning and range-of-motion. This subject adjusted for varying ball height through modified initial knee positioning while maintaining fairly constant ranges-of-motion. Key pointsInitial knee positioning and range-of-motion were positively related to racket velocity and characteristic of more skilled players for the closed stance forehand motion.Knee positioning and range-of-motion had several indirect biomechanical effects on the forehand motion such as movement of the body mass center, work of the knee, hip and back joints, and the angular

  12. The influence of visual information on multi-muscle control during quiet stance: a spectral analysis approach.

    PubMed

    Danna-Dos-Santos, Alessander; Degani, Adriana M; Boonstra, Tjeerd W; Mochizuki, Luis; Harney, Allison M; Schmeckpeper, Megan M; Tabor, Lori C; Leonard, Charles T

    2015-02-01

    Standing upright requires the coordination of neural drives to a large set of muscles involved in controlling human bipedal stance (i.e., postural muscles). The coordination may deteriorate in situations where standing is performed under more challenging circumstances, such as standing on a smaller base of support or not having adequate visual information. The present study investigates the role of common neural inputs in the organization of multi-muscle synergies and the effects of visual input disruption to this mechanism of control. We analyzed the strength and distribution of correlated neural inputs (measured by intermuscular coherence) to six postural muscles previously recognized as components of synergistic groups involved in the maintenance of the body's vertical positioning. Two experimental conditions were studied: quiet bipedal stance performed with opened eyes (OEs) and closed eyes (CEs). Nine participants stood quietly for 30 s while the activity of the soleus, biceps femoris, lumbar erector spinae, tibialis anterior, rectus femoris, and rectus abdominis muscles were recorded using surface electrodes. Intermuscular (EMG-EMG) coherence was estimated for 12 muscle pairs formed by these muscles, including pairs formed solely by either posterior, anterior, or mixed (one posterior and one anterior) muscles. Intermuscular coherence was only found to be significant for muscle pairs formed solely by either posterior or anterior muscles, and no significant coherence was found for mixed muscle pairs. Significant intermuscular coherence was only found within a distinct frequency interval bounded between 1 and 10 Hz when visual input was available (OEs trials). The strength of correlated neural inputs was similar across muscle pairs located in different joints but executing a similar function (pushing body either backward or forward) suggesting that synergistic postural groups are likely formed based on their functional role instead of their anatomical location

  13. Evaluative Decision-Making for High-Quality Professional Development: Cultivating an Evaluative Stance

    ERIC Educational Resources Information Center

    Sumsion, Jennifer; Lunn Brownlee, Joanne; Ryan, Sharon; Walsh, Kerryann; Farrell, Ann; Irvine, Susan; Mulhearn, Gerry; Berthelsen, Donna

    2015-01-01

    Unprecedented policy attention to early childhood education internationally has highlighted the crucial need for a skilled early years workforce. Consequently, professional development of early years educators has become a global policy imperative. At the same time, many maintain that professional development research has reached an impasse. In…

  14. Time?

    NASA Astrophysics Data System (ADS)

    Amoroso, Richard L.

    2013-09-01

    The concept of time in the `clockwork' Newtonian world was irrelevant; and has generally been ignored until recently by several generations of physicists since the implementation of quantum mechanics. We will set aside the utility of time as a property relating to physical calculations of events relating to a metrics line element or as an aspect of the transformation of a particles motion/interaction in a coordinate system or in relation to thermodynamics etc., i.e. we will discard all the usual uses of time as a concept used to circularly define physical parameters in terms of other physical parameters; concentrating instead on time as an aspect of the fundamental cosmic topology of our virtual reality especially as it inseparably relates to the nature and role of the observer in natural science.

  15. Therapeutic Experience on Stance Control Knee-Ankle-Foot Orthosis With Electromagnetically Controlled Knee Joint System in Poliomyelitis

    PubMed Central

    Kim, Jung-Hwan; Ji, Sang-Goo; Jung, Kang-Jae

    2016-01-01

    A 54-year-old man with poliomyelitis had been using a conventional, passive knee-ankle-foot orthosis (KAFO) with a drop ring lock knee joint for about 40 years. A stance control KAFO (SCKAFO) with an electromagnetically controlled (E-MAG) knee joint system was prescribed. To correct his gait pattern, he also underwent rehabilitation therapy, which included muscle re-education, neuromuscular electrical stimulation, strengthening exercises for the lower extremities, and balance training twice a week for about 4 months. Both before and after rehabilitation, we conducted a gait analysis and assessed the physiological cost index in energy expended during walking in a locked-knee state and while he wore a SCKAFO with E-MAG. When compared with the pre-rehabilitation data, the velocity, step length, stride length, and knee kinematic data were improved after rehabilitation. Although the SCKAFO with E-MAG system facilitated the control of knee motion during ambulation, appropriate rehabilitative therapy was also needed to achieve a normal gait pattern. PMID:27152288

  16. Therapeutic Experience on Stance Control Knee-Ankle-Foot Orthosis With Electromagnetically Controlled Knee Joint System in Poliomyelitis.

    PubMed

    Kim, Jung-Hwan; Ji, Sang-Goo; Jung, Kang-Jae; Kim, Jae-Hyung

    2016-04-01

    A 54-year-old man with poliomyelitis had been using a conventional, passive knee-ankle-foot orthosis (KAFO) with a drop ring lock knee joint for about 40 years. A stance control KAFO (SCKAFO) with an electromagnetically controlled (E-MAG) knee joint system was prescribed. To correct his gait pattern, he also underwent rehabilitation therapy, which included muscle re-education, neuromuscular electrical stimulation, strengthening exercises for the lower extremities, and balance training twice a week for about 4 months. Both before and after rehabilitation, we conducted a gait analysis and assessed the physiological cost index in energy expended during walking in a locked-knee state and while he wore a SCKAFO with E-MAG. When compared with the pre-rehabilitation data, the velocity, step length, stride length, and knee kinematic data were improved after rehabilitation. Although the SCKAFO with E-MAG system facilitated the control of knee motion during ambulation, appropriate rehabilitative therapy was also needed to achieve a normal gait pattern. PMID:27152288

  17. The effects of dual-channel functional electrical stimulation on stance phase sagittal kinematics in patients with hemiparesis.

    PubMed

    Springer, Shmuel; Vatine, Jean-Jacques; Wolf, Alon; Laufer, Yocheved

    2013-04-01

    Sixteen subjects (aged 54.2 ± 14.1 years) with hemiparesis (7.9 ± 7.1 years since diagnosis) demonstrating a foot-drop and hamstrings muscle weakness were fitted with a dual-channel functional electrical stimulation (FES) system activating the dorsiflexors and hamstrings muscles. Measurements of gait performance were collected after a conditioning period of 6 weeks, during which the subjects used the system throughout the day. Gait was assessed with and without the dual-channel FES system, as well as with peroneal stimulation alone. Outcomes included lower limb kinematics and the step length taken with the non-paretic leg. Results with the dual-channel FES indicate that in the subgroup of subjects who demonstrated reduced hip extension but no knee hyperextension (n = 9), hamstrings FES increased hip extension during terminal stance without affecting the knee. Similarly, in the subgroup of subjects who demonstrated knee hyperextension but no limitation in hip extension (n = 7), FES restrained knee hyperextension without having an impact on hip movement. Additionally, step length was increased in all subjects. The peroneal FES had a positive effect only on the ankle. The results suggest that dual-channel FES for the dorsiflexors and hamstrings muscles may affect lower limb control beyond that which can be attributed to peroneal stimulation alone. PMID:23231828

  18. Plantar-flexion of the ankle joint complex in terminal stance is initiated by subtalar plantar-flexion: A bi-planar fluoroscopy study.

    PubMed

    Koo, Seungbum; Lee, Kyoung Min; Cha, Young Joo

    2015-10-01

    Gross motion of the ankle joint complex (AJC) is a summation of the ankle and subtalar joints. Although AJC kinematics have been widely used to evaluate the function of the AJC, the coordinated movements of the ankle and subtalar joints are not well understood. The purpose of this study was to accurately quantify the individual kinematics of the ankle and subtalar joints in the intact foot during ground walking by using a bi-planar fluoroscopic system. Bi-planar fluoroscopic images of the foot and ankle during walking and standing were acquired from 10 healthy subjects. The three-dimensional movements of the tibia, talus, and calcaneus were calculated with a three-dimensional/two-dimensional registration method. The skeletal kinematics were quantified from 9% to 86% of the full stance phase because of the limited camera speed of the X-ray system. At the beginning of terminal stance, plantar-flexion of the AJC was initiated in the subtalar joint on average at 75% ranging from 62% to 76% of the stance phase, and plantar-flexion of the ankle joint did not start until 86% of the stance phase. The earlier change to plantar-flexion in the AJC than the ankle joint due to the early plantar-flexion in the subtalar joint was observed in 8 of the 10 subjects. This phenomenon could be explained by the absence of direct muscle insertion on the talus. Preceding subtalar plantar-flexion could contribute to efficient and stable ankle plantar-flexion by locking the midtarsal joint, but this explanation needs further investigation. PMID:26238571

  19. (Positive) Power to the Child: The Role of Children's Willing Stance toward Parents in Developmental Cascades from Toddler Age to Early Preadolescence

    PubMed Central

    Kochanska, Grazyna; Kim, Sanghag; Boldt, Lea J.

    2015-01-01

    In contrast to once dominant views of children as passive in the parent-led process of socialization, they are now seen as active agents who can considerably influence that process. But those newer perspectives typically focus on the child's antagonistic influence, due either to a difficult temperament or aversive, resistant, negative behaviors that elicit adversarial responses from the parent and lead to future coercive cascades in the relationship. Children's capacity to act as receptive, willing, even enthusiastic, active socialization agents is largely overlooked. Informed by attachment theory and other relational perspectives, we depict children as able to adopt an active willing stance and to exert robust positive influence in the mutually cooperative socialization enterprise. A longitudinal study of 100 community families (mothers, fathers, and children) demonstrates that willing stance (a) is a latent construct, observable in diverse parent-child contexts parallel at 38, 52, and 67 months, and longitudinally stable, (b) originates within an early secure parent-child relationship at 25 months, and (c) promotes a positive future cascade toward adaptive outcomes at age 10. The outcomes include the parent's observed and child-reported positive, responsive behavior, as well as child-reported internal obligation to obey the parent and parent-reported low level of child behavior problems. The construct of willing stance has implications for basic research in typical socialization and in developmental psychopathology, and for prevention and intervention. PMID:26439058

  20. Clarification of functional differences between the hallux and lesser toes during the single leg stance: immediate effects of conditioning contraction of the toe plantar flexion muscles.

    PubMed

    Saeki, Junya; Tojima, Michio; Torii, Suguru

    2015-09-01

    [Purpose] The purpose of this study was to determine the functional differences of the plantar flexion muscles of the hallux and lesser toes during the single leg stance by comparing postural sway in different conditioning contraction interventions. [Subjects] Thirty-four healthy, young males and females participated in this study. [Methods] The front-back and right-left direction components of maximal displacement and postural sway velocity during the single leg stance were measured in various conditioning contraction interventions for the plantar flexion muscles of the hallux or lessor toes. [Results] The main findings of this study were as follows: 1) the front-back direction component of maximal displacement was reduced by conditioning contraction of the plantar flexion muscles of the hallux, and 2) the front-back direction component of the postural sway velocity was reduced by conditioning contraction of the plantar flexion muscles of the lesser toes during the single leg stance. [Conclusion] The plantar flexion muscles of the lesser toes control the postural sway velocity. Furthermore, the plantar flexion muscles of the hallux appear to control the amplitude of postural sway. PMID:26504272

  1. (Positive) power to the child: The role of children's willing stance toward parents in developmental cascades from toddler age to early preadolescence.

    PubMed

    Kochanska, Grazyna; Kim, Sanghag; Boldt, Lea J

    2015-11-01

    In a change from the once-dominant view of children as passive in the parent-led process of socialization, children are now seen as active agents who can considerably influence that process. However, these newer perspectives typically focus on the child's antagonistic influence, due either to a difficult temperament or aversive, resistant, negative behaviors that elicit adversarial responses from the parent and lead to future coercive cascades in the relationship. Children's capacity to act as receptive, willing, even enthusiastic, active socialization agents is largely overlooked. Informed by attachment theory and other relational perspectives, we depict children as able to adopt an active willing stance and to exert robust positive influence in the mutually cooperative socialization enterprise. A longitudinal study of 100 community families (mothers, fathers, and children) demonstrates that willing stance (a) is a latent construct, observable in diverse parent-child contexts, parallel at 38, 52, and 67 months and longitudinally stable; (b) originates within an early secure parent-child relationship at 25 months; and (c) promotes a positive future cascade toward adaptive outcomes at age 10. The outcomes include the parent's observed and child-reported positive, responsive behavior, as well as child-reported internal obligation to obey the parent and parent-reported low level of child behavior problems. The construct of willing stance has implications for basic research in typical socialization and in developmental psychopathology as well as for prevention and intervention. PMID:26439058

  2. 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

  3. Estimation of Quasi-Stiffness and Propulsive Work of the Human Ankle in the Stance Phase of Walking

    PubMed Central

    Shamaei, Kamran; Sawicki, Gregory S.; Dollar, Aaron M.

    2013-01-01

    Characterizing the quasi-stiffness and work of lower extremity joints is critical for evaluating human locomotion and designing assistive devices such as prostheses and orthoses intended to emulate the biological behavior of human legs. This work aims to establish statistical models that allow us to predict the ankle quasi-stiffness and net mechanical work for adults walking on level ground. During the stance phase of walking, the ankle joint propels the body through three distinctive phases of nearly constant stiffness known as the quasi-stiffness of each phase. Using a generic equation for the ankle moment obtained through an inverse dynamics analysis, we identify key independent parameters needed to predict ankle quasi-stiffness and propulsive work and also the functional form of each correlation. These parameters include gait speed, ankle excursion, and subject height and weight. Based on the identified form of the correlation and key variables, we applied linear regression on experimental walking data for 216 gait trials across 26 subjects (speeds from 0.75–2.63 m/s) to obtain statistical models of varying complexity. The most general forms of the statistical models include all the key parameters and have an R2 of 75% to 81% in the prediction of the ankle quasi-stiffnesses and propulsive work. The most specific models include only subject height and weight and could predict the ankle quasi-stiffnesses and work for optimal walking speed with average error of 13% to 30%. We discuss how these models provide a useful framework and foundation for designing subject- and gait-specific prosthetic and exoskeletal devices designed to emulate biological ankle function during level ground walking. PMID:23555839

  4. US definitions, current use, and FDA stance on use of platelet-rich plasma in sports medicine.

    PubMed

    Beitzel, Knut; Allen, Donald; Apostolakos, John; Russell, Ryan P; McCarthy, Mary Beth; Gallo, Gregory J; Cote, Mark P; Mazzocca, Augustus D

    2015-02-01

    With increased utilization of platelet-rich plasma (PRP), it is important for clinicians to understand the United States, the Food and Drug Administration (FDA) regulatory role and stance on PRP. Blood products such as PRP fall under the prevue of FDA's Center for Biologics Evaluation and Research (CBER). CBER is responsible for regulating human cells, tissues, and cellular and tissue-based products. The regulatory process for these products is described in the FDA's 21 CFR 1271 of the Code of Regulations. Under these regulations, certain products including blood products such as PRP are exempt and therefore do not follow the FDA's traditional regulatory pathway that includes animal studies and clinical trials. The 510(k) application is the pathway used to bring PRP preparation systems to the market. The 510(k) application allows devices that are "substantially equivalent" to a currently marketed device to come to the market. There are numerous PRP preparation systems on the market today with FDA clearance; however, nearly all of these systems have 510(k) clearance for producing platelet-rich preparations intended to be used to mix with bone graft materials to enhance bone graft handling properties in orthopedic practices. The use of PRP outside this setting, for example, an office injection, would be considered "off label." Clinicians are free to use a product off-label as long as certain responsibilities are met. Per CBER, when the intent is the practice of medicine, clinicians "have the responsibility to be well informed about the product, to base its use on firm scientific rationale and on sound medical evidence, and to maintain records of the product's use and effects." Finally, despite PRP being exempted, the language in 21 CFR 1271 has caused some recent concern over activated PRP; however to date, the FDA has not attempted to regulate activated PRP. Clinicians using activated PRP should be mindful of these concerns and continued to stay informed. PMID

  5. Naturalness as an ethical stance: idea(l)s and practices of care in western herbal medicine in the UK.

    PubMed

    Nissen, Nina

    2015-01-01

    An association of non-biomedical healthcare with appeals to nature and naturalness, and an invocation of a rhetoric of gentleness, goodness, purity and moral power has been noted previously, and some scholars argue that nature has taken on a meaning broadly opposed to the rational scientific order of modernity. Drawing on an ethnographic study of women's practice and use of western herbal medicine (WHM) in the UK, the intertwining of the perceived naturalness of WHM with distinct care practices points to a further avenue for exploration. To examine patients' and herbalists' discourses of the naturalness of WHM and associated idea(l)s and practices of care, understandings of nature and a feminist ethics of care are utilized as analytical frameworks. The analysis presented suggests that, through WHM, patients and herbalists become embedded in a complex spatio-temporal wholeness and web of care that intertwines past, present and future, self and others, and local and global concerns. In the emerging 'ordinary ethics of care', naturalness constitutes a sign of goodness and of a shared humanity within the organic world, while care, underpinned by idea(l)s of natural and holistic care practices, links human and non-human others. Thus, the naturalness of WHM, as perceived by some patients and herbalists, engages and blends with a continually unfolding field of relationships in the lifeworld(s), where care practices, caring relations and collective wellbeing may constitute an ethical stance that raises deeper questions about the significance of relationality, the values of care/caring and the mutual involvement of nature and human being(s). PMID:26001272

  6. The effect of time-of-day on static and dynamic balance in recreational athletes.

    PubMed

    Heinbaugh, Erika M; Smith, Derek T; Zhu, Qin; Wilson, Margaret A; Dai, Boyi

    2015-09-01

    The purpose of this study was to investigate the effect of time-of-day (morning vs. afternoon) on static and dynamic balance in recreational athletes. A total of 34 recreational athletes completed the single-leg stance test with or without eyes open, lower quarter Y-balance test, upper quarter Y-balance test, and single-leg landing balance test in a random order in the morning (7:00-10:00 am) and afternoon (3:00-6:00 pm) for two consecutive days. Compared with the morning, participants demonstrated decreased centre of pressure (COP) sway areas (p = 0.002; Cohen's d (d) = 0.28) and sway speeds (p = 0.002; d = 0.17) during the eyes-open single-leg stance test, increased stance time (p = 0.031; d = 0.16) and decreased COP sway areas (p = 0.029; d = 0.22) during the eyes-closed single-leg stance test, and increased reaching distances (p = 0.024; d = 0.10) during the upper quarter Y-balance test in the afternoon. The between-day effect (day 1 vs. day 2) was observed for several parameters. Time-of-day had a minimal effect on dynamic balance and a noticeable effect on static balance. Time-of-day may be considered as a factor in designing balance training programmes and intervention studies for recreational athletes. PMID:26517605

  7. Comparison of a laboratory grade force platform with a Nintendo Wii Balance Board on measurement of postural control in single-leg stance balance tasks.

    PubMed

    Huurnink, Arnold; Fransz, Duncan P; Kingma, Idsart; van Dieën, Jaap H

    2013-04-26

    Training and testing of balance have potential applications in sports and medicine. Laboratory grade force plates (FP) are considered the gold standard for the measurement of balance performance. Measurements in these systems are based on the parameterization of center of pressure (CoP) trajectories. Previous research validated the inexpensive, widely available and portable Nintendo Wii Balance Board (WBB). The novelty of the present study is that FP and WBB are compared on CoP data that was collected simultaneously, by placing the WBB on the FP. Fourteen healthy participants performed ten sequences of single-leg stance tasks with eyes open (EO), eyes closed (EC) and after a sideways hop (HOP). Within trial comparison of the two systems showed small root-mean-square differences for the CoP trajectories in the x and y direction during the three tasks (mean±SD; EO: 0.33±0.10 and 0.31±0.16 mm; EC: 0.58±0.17 and 0.63±0.19 mm; HOP: 0.74±0.34 and 0.74±0.27 mm, respectively). Additionally, during all 420 trials, comparison of FP and WBB revealed very high Pearson's correlation coefficients (r) of the CoP trajectories (x: 0.999±0.002; y: 0.998±0.003). A general overestimation was found on the WBB compared to the FP for 'CoP path velocity' (EO: 5.3±1.9%; EC: 4.0±1.4%; HOP: 4.6±1.6%) and 'mean absolute CoP sway' (EO: 3.5±0.7%; EC: 3.7±0.5%; HOP: 3.6±1.0%). This overestimation was highly consistent over the 140 trials per task (r>0.996). The present findings demonstrate that WBB is sufficiently accurate in quantifying CoP trajectory, and overall amplitude and velocity during single-leg stance balance tasks. PMID:23528845

  8. Philip Morris's website and television commercials use new language to mislead the public into believing it has changed its stance on smoking and disease

    PubMed Central

    Friedman, Lissy C

    2007-01-01

    Objectives This paper analyses Philip Morris's evolving website and the legal strategies employed in its creation and dissemination. Methods Internal tobacco documents were searched and examined and their substance verified and triangulated using media accounts, legal and public health research papers, and visits to Philip Morris's website. Various drafts of website language, as well as informal discussion of the website's creation, were located in internal Philip Morris documents. I compared website statements pertaining to Philip Morris's stance on cigarette smoking and disease with statements made in tobacco trials. Results Philip Morris created and disseminated its website's message that it agreed that smoking causes disease and is addictive in an effort to sway public opinion, while maintaining in a litigation setting its former position that it cannot be proved that smoking causes disease or is addictive. Conclusions Philip Morris has not changed its position on smoking and health or addiction in the one arena where it has the most to lose—in the courtroom, under oath. PMID:18048599

  9. Calibration of the Leg Muscle Responses Elicited by Predictable Perturbations of Stance and the Effect of Vision.

    PubMed

    Sozzi, Stefania; Nardone, Antonio; Schieppati, Marco

    2016-01-01

    Motor adaptation due to task practice implies a gradual shift from deliberate control of behavior to automatic processing, which is less resource- and effort-demanding. This is true both for deliberate aiming movements and for more stereotyped movements such as locomotion and equilibrium maintenance. Balance control under persisting critical conditions would require large conscious and motor effort in the absence of gradual modification of the behavior. We defined time-course of kinematic and muscle features of the process of adaptation to repeated, predictable perturbations of balance eliciting both reflex and anticipatory responses. Fifty-nine sinusoidal (10 cm, 0.6 Hz) platform displacement cycles were administered to 10 subjects eyes-closed (EC) and eyes-open (EO). Head and Center of Mass (CoM) position, ankle angle and Tibialis Anterior (TA) and Soleus (Sol) EMG were assessed. EMG bursts were classified as reflex or anticipatory based on the relationship between burst amplitude and ankle angular velocity. Muscle activity decreased over time, to a much larger extent for TA than Sol. The attenuation was larger for the reflex than the anticipatory responses. Regardless of muscle activity attenuation, latency of muscle bursts and peak-to-peak CoM displacement did not change across perturbation cycles. Vision more than doubled speed and the amount of EMG adaptation particularly for TA activity, rapidly enhanced body segment coordination, and crucially reduced head displacement. The findings give new insight on the mode of amplitude- and time-modulation of motor output during adaptation in a balancing task, advocate a protocol for assessing flexibility of balance strategies, and provide a reference for addressing balance problems in patients with movement disorders. PMID:27625599

  10. Calibration of the Leg Muscle Responses Elicited by Predictable Perturbations of Stance and the Effect of Vision

    PubMed Central

    Sozzi, Stefania; Nardone, Antonio; Schieppati, Marco

    2016-01-01

    Motor adaptation due to task practice implies a gradual shift from deliberate control of behavior to automatic processing, which is less resource- and effort-demanding. This is true both for deliberate aiming movements and for more stereotyped movements such as locomotion and equilibrium maintenance. Balance control under persisting critical conditions would require large conscious and motor effort in the absence of gradual modification of the behavior. We defined time-course of kinematic and muscle features of the process of adaptation to repeated, predictable perturbations of balance eliciting both reflex and anticipatory responses. Fifty-nine sinusoidal (10 cm, 0.6 Hz) platform displacement cycles were administered to 10 subjects eyes-closed (EC) and eyes-open (EO). Head and Center of Mass (CoM) position, ankle angle and Tibialis Anterior (TA) and Soleus (Sol) EMG were assessed. EMG bursts were classified as reflex or anticipatory based on the relationship between burst amplitude and ankle angular velocity. Muscle activity decreased over time, to a much larger extent for TA than Sol. The attenuation was larger for the reflex than the anticipatory responses. Regardless of muscle activity attenuation, latency of muscle bursts and peak-to-peak CoM displacement did not change across perturbation cycles. Vision more than doubled speed and the amount of EMG adaptation particularly for TA activity, rapidly enhanced body segment coordination, and crucially reduced head displacement. The findings give new insight on the mode of amplitude- and time-modulation of motor output during adaptation in a balancing task, advocate a protocol for assessing flexibility of balance strategies, and provide a reference for addressing balance problems in patients with movement disorders. PMID:27625599

  11. Higher Knee Flexion Moment During the Second Half of the Stance Phase of Gait Is Associated With the Progression of Osteoarthritis of the Patellofemoral Joint on Magnetic Resonance Imaging

    PubMed Central

    Teng, Hsiang-Ling; Macleod, Toran D.; Link, Thomas M.; Majumdar, Sharmila; Souza, Richard B.

    2016-01-01

    STUDY DESIGN Controlled laboratory study, longitudinal design. OBJECTIVE To examine whether baseline knee flexion moment or impulse during walking is associated with the progression of osteoarthritis (OA) with magnetic resonance imaging of the patellofemoral joint (PFJ) at 1 year. BACKGROUND Patellofemoral joint OA is highly prevalent and a major source of pain and dysfunction. The biomechanical factors associated with the progression of PFJ OA remain unclear. METHODS Three-dimensional gait analyses were performed at baseline. Magnetic resonance imaging of the knee (high-resolution, 3-D, fast spin-echo sequence) was used to identify PFJ cartilage and bone marrow edema–like lesions at baseline and a 1-year follow-up. The severity of PFJ OA progression was defined using the modified Whole-Organ Magnetic Resonance Imaging Score when new or increased cartilage or bone marrow edema–like lesions were observed at 1 year. Peak external knee flexion moment and flexion moment impulse during the first and second halves of the stance phase of gait were compared between progressors and nonprogressors, and used to predict progression after adjusting for age, sex, body mass index, and presence of baseline PFJ OA. RESULTS Sixty-one participants with no knee OA or isolated PFJ OA were included. Patellofemoral joint OA progressors (n = 10) demonstrated significantly higher peak knee flexion moment (P = .01) and flexion moment impulse (P = .04) during the second half of stance at baseline compared to nonprogressors. Logistic regression showed that higher peak knee flexion moment during the second half of the stance phase was significantly associated with progression at 1 year (adjusted odds ratio = 3.3, P = .01). CONCLUSION Peak knee flexion moment and flexion moment impulse during the second half of stance are related to the progression of PFJ OA and may need to be considered when treating individuals who are at risk of or who have PFJ OA. PMID:26161626

  12. Comparison of the classically conditioned withdrawal reflex in cerebellar patients and healthy control subjects during stance: 2. Biomechanical characteristics.

    PubMed

    Kutz, D F; Kaulich, Th; Föhre, W; Gerwig, M; Timmann, D; Kolb, F P

    2014-03-01

    This study addresses cerebellar involvement in classically conditioned nociceptive lower limb withdrawal reflexes in standing humans. A preceding study compared electromyographic activities in leg muscles of eight patients with cerebellar disease (CBL) and eight age-matched controls (CTRL). The present study extends and completes that investigation by recording biomechanical signals from a strain-gauge-equipped platform during paired auditory conditioning stimuli (CS) and unconditioned stimuli (US) trials and during US-alone trials. The withdrawal reflex performance-lifting the stimulated limb (decreasing the vertical force from that leg, i.e. 'unloading') and transferring body weight to the supporting limb (increasing the vertical force from that leg, i.e. 'loading')-was quantified by the corresponding forces exerted onto the platform. The force changes were not simultaneous but occurred as a sequence of multiple force peaks at different times depending on the specific limb task (loading or unloading). Motor learning, expressed by the occurrence of conditioned responses (CR), is characterized by this sequence beginning already within the CSUS window. Loading and unloading were delayed and prolonged in CBL, resulting in incomplete rebalancing during the analysis period. Trajectory loops of the center of vertical pressure-derived from vertical forces-were also incomplete in CBL within the recording period. However, exposing CBL to a CS resulted in motor improvement reflected by shortening the time of rebalancing and by optimizing the trajectory loop. In summary, associative responses in CBL are not absent although they are less frequent and of smaller amplitude than in CTRL. PMID:24445111

  13. Comparison of the classically conditioned withdrawal reflex in cerebellar patients and healthy control subjects during stance: I. electrophysiological characteristics.

    PubMed

    Timmann, D; Kaulich, T; Föhre, W; Kutz, D F; Gerwig, M; Kolb, F P

    2013-02-01

    The aim of this study was to demonstrate the involvement of the human cerebellum in the classically conditioned lower limb withdrawal reflex in standing subjects. Electromyographic activity was recorded from the main muscle groups of both legs of eight patients with cerebellar disease (CBL) and eight control subjects (CTRL). The unconditioned stimulus (US) consisted of electrical stimulation of the tibial nerve at the medial malleolus. The conditioning stimulus (CS) was an auditory signal given via headphones. Experiments started with 70 paired conditioning stimulus-unconditioned stimulus(CSUS) trials followed by 50 US-alone trials. The general reaction consisted of lifting and flexing the stimulated (stepping) leg with accompanying activation of the contralateral (supporting) leg. In CTRL, the ipsilateral (side of stimulation) flexor and contralateral extensor muscles were activated characteristically. In CBL, the magnitudes of ipsilateral flexor and contralateral extensor muscle activation were reduced comparably. In CTRL, the conditioning process increased the incidence of conditioned responses (CR), following a typical learning curve, while CBL showed a clearly lower CR incidence with a marginal increase, albeit, at a shorter latency. Conditioning processes also modified temporal parameters by shortening unconditioned response (UR) onset latencies and UR times to peak and, more importantly in CBL, also the sequence of activation of muscles, which became similar to that of CTRL. The expression of this reflex in standing subjects showed characteristic differences in the groups tested with the underlying associative processes not being restricted exclusively to the CR but also modifying parameters of the innate UR. PMID:22836373

  14. Automatic determination of the transition between successive control mechanisms in upright stance assessed by modelling of the centre of pressure.

    PubMed

    Rougier, P

    1999-02-01

    A recently introduced concept models the trajectory of the centre of pressure as a fractional Brownian motion and reveals that two successive scaling regimes, acting hypothetically as open and closed loop mechanisms, are implicated in posture control. Objectivity is obviously required in the determination of the transition point, i.e. the point at which an open-loop control mechanism would switch to a closed-loop one, in order to provide reproducibility and automatism in the processing of data. In the method proposed herein, the transition point corresponds to the maximal distance separating a diffusion curve in a double logarithmic plot (mean square distances MSD calculated on each axis versus increasing time intervals Deltat) from a straight line characterising a pure stochastic behaviour. In closed eye conditions, the switch appears medio-laterally in a 0. 26-0.52 s range for Deltat, the corresponding MSD being in the range of 1.86-10.50 mm(2). In the forward-backward direction, the transition is in a 0.28-0.42 s range and the corresponding MSD is between 3.60 and 15.17 mm(2). Finally, these co-ordinates induce scaling exponents over 0.50 for the shortest Deltat, thus suggesting open-loop control, whereas those of longest Deltat, ranged between 0 and 0.20, give evidence of close-loop control. This data is compared to previous data based upon empirical methods. PMID:10455557

  15. Influence of visual feedback on successive control mechanisms in upright quiet stance in humans assessed by fractional Brownian motion modelling.

    PubMed

    Rougier, P

    1999-05-14

    An up-to-date way to model the centre of pressure (CP) trajectories may consist in using fractional Brownian motion (fBm). By doing so, one may note that standing still is in fact controlled by two separate and successive mechanisms. The point raised in this study concerns the nature of these control mechanisms and their level of interaction. Following this idea, visual feedback (VFB), which is known to affect postural control by significantly decreasing sway magnitudes, was used. Twelve healthy adults, instructed to stand as still as possible, were tested under this VFB protocol (via a PC screen). In order to model the CP trajectories as fBm, variograms (mean square distances, MSD, expressed as a function of increasing time intervals deltat) were bi-logarithmically plotted. The main visual effect of VFB on these variograms concerns longest latency scaling regimes which reveal less stochastic and consequently more accurate control (P < 0.05 and P < 0.01 for X and Y components, respectively). An increase in the MSD of the transition point, which corresponds to the switch between the two control mechanisms, is also noted (P < 0.05). Overall, evidence is provided from this data that long latency scaling regimes do operate through a feedback process. Interestingly, this improved determinism in feedback control in turn induces a similar effect on the control operating over the shortest deltat. Thus, by privileging a control strategy based on feedback mechanisms, VFB in turn would make the subjects quicker in their initial displacement in order to reach a position capable of initiating a feedback mechanism. PMID:10465697

  16. Dynamic 3D scanning as a markerless method to calculate multi-segment foot kinematics during stance phase: methodology and first application.

    PubMed

    Van den Herrewegen, Inge; Cuppens, Kris; Broeckx, Mario; Barisch-Fritz, Bettina; Vander Sloten, Jos; Leardini, Alberto; Peeraer, Louis

    2014-08-22

    Multi-segmental foot kinematics have been analyzed by means of optical marker-sets or by means of inertial sensors, but never by markerless dynamic 3D scanning (D3DScanning). The use of D3DScans implies a radically different approach for the construction of the multi-segment foot model: the foot anatomy is identified via the surface shape instead of distinct landmark points. We propose a 4-segment foot model consisting of the shank (Sha), calcaneus (Cal), metatarsus (Met) and hallux (Hal). These segments are manually selected on a static scan. To track the segments in the dynamic scan, the segments of the static scan are matched on each frame of the dynamic scan using the iterative closest point (ICP) fitting algorithm. Joint rotations are calculated between Sha-Cal, Cal-Met, and Met-Hal. Due to the lower quality scans at heel strike and toe off, the first and last 10% of the stance phase is excluded. The application of the method to 5 healthy subjects, 6 trials each, shows a good repeatability (intra-subject standard deviations between 1° and 2.5°) for Sha-Cal and Cal-Met joints, and inferior results for the Met-Hal joint (>3°). The repeatability seems to be subject-dependent. For the validation, a qualitative comparison with joint kinematics from a corresponding established marker-based multi-segment foot model is made. This shows very consistent patterns of rotation. The ease of subject preparation and also the effective and easy to interpret visual output, make the present technique very attractive for functional analysis of the foot, enhancing usability in clinical practice. PMID:24998032

  17. The difficulty of the postural control task affects multi-muscle control during quiet standing.

    PubMed

    García-Massó, X; Pellicer-Chenoll, M; Gonzalez, L M; Toca-Herrera, J L

    2016-07-01

    The aim of this study was to compare the electromyographic (EMG) coherence between the lower limb and the core muscles when carrying out two postural tasks at different difficulty levels. EMG was recorded in 20 healthy male subjects while performing two independent quiet standing tasks. The first one involved a bipedal stance with the eyes open, while the second consisted of a dominant unipedal stance also with the eyes open. The obtained EMG signals were analysed by computing estimations of EMG-EMG coherence between muscle pairs, both singly (single-pair estimations) and combined (pooled estimations). Pooled and single coherence of anterior, posterior, core, antagonist and mixed pairs of muscles were significant in the 0-5 Hz frequency band. The results indicate that core and antagonist muscle groups, such as the anterior and posterior muscles, share low-frequency neural inputs (0-5 Hz) which could be responsible of the M-modes assembly. The core muscles could therefore provide the necessary synergy to maintain spine stability during the balancing exercise. Finally, differences in EMG-EMG coherence suggest that the muscle synergies formed during unipedal stance tasks are different from those established during bipedal stance. PMID:26942928

  18. Fall risk-relevant functional mobility outcomes in dementia following dyadic tai chi exercise.

    PubMed

    Yao, Lan; Giordani, Bruno J; Algase, Donna L; You, Mei; Alexander, Neil B

    2013-03-01

    Whether persons with dementia benefit from fall prevention exercise is unclear. Applying the Positive Emotion-Motivated Tai Chi protocol, preliminary findings concerning adherence and effects of a dyadic Tai Chi exercise program on persons with Alzheimer's disease (AD) are reported. Using pre/posttest design, 22 community-dwelling AD-caregiver dyads participated in the program. Fall-risk-relevant functional mobility was measured using Unipedal Stance Time (UST) and Timed Up and Go (TUG) tests. Results showed that 19/22 (86.4%) AD patients completed the 16-week program and final assessment; 16/19 dyads (84.2%) completed the prescribed home program as reported by caregivers. UST adjusted mean improved from 4.0 to 5.1 (Week 4, p < .05) and 5.6 (Week 16, p < .05); TUG improved from 13.2 to 11.6 (Week 4, p < .05) and 11.6 (Week 16, p > .05) post intervention. Retaining dementia patients in an exercise intervention remains challenging. The dyadic Tai Chi approach appears to succeed in keeping AD-caregiver dyads exercising and safe. PMID:22517441

  19. Time-Limited Psychotherapy With Adolescents

    PubMed Central

    Shefler, Gaby

    2000-01-01

    Short-term dynamic therapies, characterized by abbreviated lengths (10–40 sessions) and, in many cases, preset termination dates, have become more widespread in the past three decades. Short-term therapies are based on rapid psychodynamic diagnosis, a therapeutic focus, a rapidly formed therapeutic alliance, awareness of termination and separation processes, and the directive stance of the therapist. The emotional storm of adolescence, stemming from both developmental and psychopathological sources, leaves many adolescents in need of psychotherapy. Many adolescents in need of therapy resist long-term attachment and involvement in an ambiguous relationship, which they experience as a threat to their emerging sense of independence and separateness. Short-term dynamic therapy can be the treatment of choice for many adolescents because it minimizes these threats and is more responsive to their developmental needs. The article presents treatment and follow-up of a 17-year-old youth, using James Mann's time-limited psychotherapy method. PMID:10793128

  20. A model of time-effective group psychotherapy for patients with personality disorders: the clinical model.

    PubMed

    Budman, S H; Cooley, S; Demby, A; Koppenaal, G; Koslof, J; Powers, T

    1996-07-01

    This article describes a model of time-limited psychotherapy for patients with personality disorders that emphasizes the group as a social microcosm. The patient population described is relatively high functioning, although the majority of the group members meet DSM-III-R (American Psychiatric Association, 1987) criteria for an Axis II diagnosis. The clinical model's key theoretical concepts, for example, interpersonal focus; active therapist stance; emphasis on group interaction and processes; use of time limits; primary care/intermittent treatment philosophy; and emphasis on patients' strengths, goals, and resources are described. The relationships between the phases of group therapy and the key theoretical concepts are delineated. PMID:8753151

  1. Stance and swing phase detection during level and slope walking in the cat: effects of slope, injury, subject and kinematic detection method.

    PubMed

    Pantall, Annette; Gregor, Robert J; Prilutsky, Boris I

    2012-05-11

    In quadrupeds, there have been limited comparisons of gait timing events detection (e.g., paw contact, PC and paw-off, PO) determined from kinematics and forceplates. The goal of this study was to investigate the effect of different slopes (0, -27, +27°), recovery times after ankle extensor nerve injury and repair (2, 6, 12 weeks), subjects and detection methods on accuracy of kinematically derived PC and PO timings during feline walking. Right hindlimb kinematics and ground reaction forces (GRF) of 4 cats walking along a sloped walkway with embedded forceplates were recorded. A total of 963 walking cycles were analyzed. Gait timings were determined from five kinematic methods based on displacements, velocities or accelerations of hindlimb markers. GRF based 'gold standard' timings for PC and PO were used to determine the systematic and random error of kinematic timing. Systematic errors between the kinematic methods differed significantly (p<0.05). Methods based on vertical paw peak acceleration and velocity gave the smallest systematic errors for PC and PO, respectively. The smallest random errors (standard deviations) for PC and PO were demonstrated by method based on paw horizontal displacement relative to greater trochanter: 13.4ms and 6.6ms, respectively. Effects of slope and subject on systematic errors of kinematic methods were significant, whereas effects of recovery time after nerve injury were not. It was concluded that timing of gait events can be determined consistently using kinematics, although adjustments must be made to account for the systematic error which varies according to subject and slope condition. PMID:22483230

  2. Hip and knee joints are more stabilized than driven during the stance phase of gait: an analysis of the 3D angle between joint moment and joint angular velocity.

    PubMed

    Dumas, R; Cheze, L

    2008-08-01

    Joint power is commonly used in orthopaedics, ergonomics or sports analysis but its clinical interpretation remains controversial. Some basic principles on muscle actions and energy transfer have been proposed in 2D. The decomposition of power on 3 axes, although questionable, allows the same analysis in 3D. However, these basic principles have been widely criticized, mainly because bi-articular muscles must be considered. This requires a more complex computation in order to determine how the individual muscle force contributes to drive the joint. Conversely, with simple 3D inverse dynamics, the analysis of both joint moment and angular velocity directions is essential to clarify when the joint moment can contribute or not to drive the joint. The present study evaluates the 3D angle between the joint moment and the joint angular velocity and investigates when the hip, knee and ankle joints are predominantly driven (angle close to 0 degrees and 180 degrees ) or stabilized (angle close to 90 degrees ) during gait. The 3D angle curves show that the three joints are never fully but only partially driven and that the hip and knee joints are mainly stabilized during the stance phase. The notion of stabilization should be further investigated, especially for subjects with motion disorders or prostheses. PMID:18206375

  3. Muscle-Activation Onset Times With Shoes and Foot Orthoses in Participants With Chronic Ankle Instability

    PubMed Central

    Dingenen, Bart; Peeraer, Louis; Deschamps, Kevin; Fieuws, Steffen; Janssens, Luc; Staes, Filip

    2015-01-01

    Context Participants with chronic ankle instability (CAI) use an altered neuromuscular strategy to shift weight from double-legged to single-legged stance. Shoes and foot orthoses may influence these muscle-activation patterns. Objective To evaluate the influence of shoes and foot orthoses on onset times of lower extremity muscle activity in participants with CAI during the transition from double-legged to single-legged stance. Design Cross-sectional study. Setting Musculoskeletal laboratory. Patients or Other Participants A total of 15 people (9 men, 6 women; age = 21.8 ± 3.0 years, height = 177.7 ± 9.6 cm, mass = 72.0 ± 14.6 kg) who had CAI and wore foot orthoses were recruited. Intervention(s) A transition task from double-legged to single-legged stance was performed with eyes open and with eyes closed. Both limbs were tested in 4 experimental conditions: (1) barefoot (BF), (2) shoes only, (3) shoes with standard foot orthoses, and (4) shoes with custom foot orthoses (SCFO). Main Outcome Measure(s) The onset of activity of 9 lower extremity muscles was recorded using surface electromyography and a single force plate. Results Based on a full-factorial (condition, region, limb, vision) linear model for repeated measures, we found a condition effect (F3,91.8 = 9.39, P < .001). Differences among experimental conditions did not depend on limb or vision condition. Based on a 2-way (condition, muscle) linear model within each region (ankle, knee, hip), earlier muscle-activation onset times were observed in the SCFO than in the BF condition for the peroneus longus (P < .001), tibialis anterior (P = .003), vastus medialis obliquus (P = .04), and vastus lateralis (P = .005). Furthermore, the peroneus longus was activated earlier in the shoes-only (P = .02) and shoes-with-standard-foot-orthoses (P = .03) conditions than in the BF condition. No differences were observed for the hip muscles. Conclusions Earlier onset of muscle activity was most apparent in the SCFO

  4. Processing time of addition or withdrawal of single or combined balance-stabilizing haptic and visual information.

    PubMed

    Honeine, Jean-Louis; Crisafulli, Oscar; Sozzi, Stefania; Schieppati, Marco

    2015-12-01

    We investigated the integration time of haptic and visual input and their interaction during stance stabilization. Eleven subjects performed four tandem-stance conditions (60 trials each). Vision, touch, and both vision and touch were added and withdrawn. Furthermore, vision was replaced with touch and vice versa. Body sway, tibialis anterior, and peroneus longus activity were measured. Following addition or withdrawal of vision or touch, an integration time period elapsed before the earliest changes in sway were observed. Thereafter, sway varied exponentially to a new steady-state while reweighting occurred. Latencies of sway changes on sensory addition ranged from 0.6 to 1.5 s across subjects, consistently longer for touch than vision, and were regularly preceded by changes in muscle activity. Addition of vision and touch simultaneously shortened the latencies with respect to vision or touch separately, suggesting cooperation between sensory modalities. Latencies following withdrawal of vision or touch or both simultaneously were shorter than following addition. When vision was replaced with touch or vice versa, adding one modality did not interfere with the effect of withdrawal of the other, suggesting that integration of withdrawal and addition were performed in parallel. The time course of the reweighting process to reach the new steady-state was also shorter on withdrawal than addition. The effects of different sensory inputs on posture stabilization illustrate the operation of a time-consuming, possibly supraspinal process that integrates and fuses modalities for accurate balance control. This study also shows the facilitatory interaction of visual and haptic inputs in integration and reweighting of stance-stabilizing inputs. PMID:26334013

  5. Quantitative analysis of stance in ataxic myxoedema.

    PubMed Central

    Harayama, H; Ohno, T; Miyatake, T

    1983-01-01

    Postural abnormalities in a 66-year-old woman with ataxic myxoedema were recorded by stabilography during treatment. After replacement therapy, 3 Hz power in the sagittal plane was greater than before treatment; this peak shifted to a higher frequency and finally its ratio became normal. This is the first report of recovery of a 3 Hz body oscillation in ataxic myxoedema. PMID:6875595

  6. Quantitative analysis of stance in ataxic myxoedema.

    PubMed

    Harayama, H; Ohno, T; Miyatake, T

    1983-06-01

    Postural abnormalities in a 66-year-old woman with ataxic myxoedema were recorded by stabilography during treatment. After replacement therapy, 3 Hz power in the sagittal plane was greater than before treatment; this peak shifted to a higher frequency and finally its ratio became normal. This is the first report of recovery of a 3 Hz body oscillation in ataxic myxoedema. PMID:6875595

  7. Resistance to Taking a Critical Stance.

    ERIC Educational Resources Information Center

    Willett, Jerri; Jeannot, Mary

    1993-01-01

    Resistance to the notion of empowerment among students in a graduate English-as-a-Second-Language (ESL) teacher preparation program is analyzed using a postmodern and feminist framework. Focus is on the role of facilitator, a role instituted to help students reflect on their own collaborative and critical processes. (Contains 39 references.)…

  8. Taking a Democratic Stance toward Knowledge

    ERIC Educational Resources Information Center

    Traugh, Cecelia

    2009-01-01

    One of the major priorities that should guide teacher education programs in preparing teachers for their work in a democratic society is to develop a commitment to knowledge that embraces complexity and to place this knowledge into competition with the mainstream vision, which results from a deep reliance on standardized testing and controls much…

  9. Error Correction: A Cognitive-Affective Stance

    ERIC Educational Resources Information Center

    Saeed, Aziz Thabit

    2007-01-01

    This paper investigates the application of some of the most frequently used writing error correction techniques to see the extent to which this application takes learners' cognitive and affective characteristics into account. After showing how unlearned application of these styles could be discouraging and/or damaging to students, the paper…

  10. Phytol in a pharma-medico-stance.

    PubMed

    Islam, Md Torequl; de Alencar, Marcus Vinícius Oliveira Barros; da Conceição Machado, Katia; da Conceição Machado, Keylla; de Carvalho Melo-Cavalcante, Ana Amélia; de Sousa, Damiao Pergentino; de Freitas, Rivelilson Mendes

    2015-10-01

    This study aims to review phytol (PYT), through published articles, periodicals, magazines and patents, which were retrieved from the PM, SD, WS, SP; DII, WIPO, CIPO, USPTO and INPI databases. Among the 149 articles and 62 patents, 27.52% articles and 87.09% patients were found on the searched topic, PYT and its sources and synthesis and metabolism; then followed by 15.44% and 14.77% articles on PYT in cytotoxicity/cancer/mutagenicity/teratogenicity and PYT in neurological diseases, respectively. In the pharma-medico viewpoint, PYT and its derivatives have been evident to have antimicrobial, cytotoxic, antitumorous, antimutagenic, anti-teratogenic, antibiotic-chemotherapeutic, antidiabetic, lipid lowering, antispasmodic, anticonvulsant, antinociceptive, antioxidant, anti-inflammatory, anxiolytic, antidepressant, immunoadjuvancy, hair growth facilitator, hair fall defense and antidandruff activities. Otherwise, the important biometebolite of PYT is phytanic acid (PA). Evidence shows PA to have cytotoxic, anticancer, antidiabetic, lipid lowering and aniteratogenic activities. In addition, it may be considered as an important biomarker for some diseases such as Refsum's Disease (RD), Sjögren Larsson syndrome (SLS), rhizomelic chondrodysplasia punctata (RZCP), chronic polyneuropathy (CP), Zellweger's disease hyperpipecolic academia (ZDHA) and related diseases. Thus, phytol may be considered as a new drug candidate. PMID:26296761

  11. Stance and the Subjunctive in Isleno Spanish

    ERIC Educational Resources Information Center

    Coles, Felice A.

    2012-01-01

    Isleno Spanish speakers maintain few contexts firmly in the subjunctive (for example, adverbial clauses with the conjunctions "para que" and "antes que" and nominal clauses with "querer"), with most other semantic or syntactic categories optionally licensing the subjunctive. This study will outline the obligatory and optional uses of present and…

  12. A Study of relationship between frailty and physical performance in elderly women.

    PubMed

    Jeoung, Bog Ja; Lee, Yang Chool

    2015-08-01

    Frailty is a disorder of multiple inter-related physiological systems. It is unclear whether the level of physical performance factors can serve as markers of frailty and a sign. The purpose of this study was to examine the relationship between frailty and physical performance in elderly women. One hundred fourteen elderly women participated in this study, their aged was from 65 to 80. We were measured 6-min walk test, grip-strength, 30-sec arm curl test, 30-sec chair stand test, 8 foot Up- and Go, Back scratch, chair sit and reach, unipedal stance, BMI, and the frailty with questionnaire. The collected data were analyzed by descriptive statistics, frequencies, correlation analysis, ANOVA, and simple liner regression using the IBM 21. SPSS program. In results, statistic tests showed that there were significant differences between frailty and 6-min walk test, 30-sec arm curl test, 30-sec chair stand test, grip-strength, Back scratch, and BMI. However, we did not find significant differences between frailty and 8 foot Up- and Go, unipedal stance. When the subjects were divided into five groups according to physical performance level, subjects with high 6-min walk, 30-sec arm curl test, chair sit and reach test, and high grip strength had low score frailty. Physical performance factors were strongly associated with decreased frailty, suggesting that physical performance improvements play an important role in preventing or reducing the frailty. PMID:26331137

  13. Time scale dependence of the center of pressure entropy: What characteristics of the neuromuscular postural control system influence stabilographic entropic half-life?

    PubMed

    Federolf, Peter; Zandiyeh, Payam; von Tscharner, Vinzenz

    2015-12-01

    The center of pressure (COP) movement in studies of postural control reveals a highly regular structure (low entropy) over short time periods and a highly irregular structure over large time scales (high entropy). Entropic half-life (EnHL) is a novel measure that quantifies the time over which short-term temporal correlations in a time series deteriorate to an uncorrelated, random structure. The current study suggested and tested three hypotheses about how characteristics of the neuromuscular postural control system may affect stabilometric EnHL: (H1) control system activity hypothesis: EnHL decreases with increased frequency of control system interventions adjusting COP motion; (H2) abundance of states hypothesis: EnHL decreases with increased number of mechanically equivalent states available to the postural system; and (H3) neurologic process hierarchy hypothesis: EnHL increases if postural control functions shift from the spinal level to the motor cortex. Thirty healthy participants performed quiet stance tests for 90 s in 18 different conditions: stance (bipedal, one-legged, and tandem); footwear (bare foot, regular sports shoe, and rocker sole shoes); and simultaneous cognitive task (two-back working memory task, no challenge). A four-way repeated-measures ANOVA revealed significant changes in EnHL for the different stance positions and for different movement directions (medio-lateral, anterior-posterior). These changes support H1 and H2. Significant differences were also found between rocker sole shoes and normal or barefoot standing, which supports H3. This study contributes to the understanding of how and why EnHL is a useful measure to monitor neuromuscular control of balance. PMID:26303025

  14. Development of the RT-GAIT, a Real-Time feedback device to improve Gait of individuals with stroke.

    PubMed

    Hegde, Nagaraj; Fulk, George D; Sazonov, Edward S

    2015-08-01

    Regaining the ability to walk is a major rehabilitation goal after a stroke. Recent research suggests that, in people with stroke, task-oriented and intensive rehabilitation strategies can drive cortical reorganization and increase activity levels. This paper describes development and pilot testing of a novel wearable device for Real-Time Gait and Activity Improving Telerehabilitation (RT-GAIT), designed for use with such rehabilitation strategies. The RT-GAIT provides auditory or tactile feedback to the individual wearing the platform. The feedback is based on the amount of time spent in stance phase on each foot, as measured by the pressure sensors embedded into the insoles. The system was initially bench-validated using sensor signals collected in a previous study. Next, a clinical case study was conducted with one post-stroke individual. The results of the case study suggest that the RT-GAIT device can potentially improve the gait parameters. Mean difference in stance times between the healthy limb and paretic limb was improved by 48% and the standard deviation for the same was improved by 87.5%, between baseline measurements and the measurements taken after the treatment with the RT-GAIT. PMID:26737592

  15. Martial Arts: Time Needed for Training

    PubMed Central

    Burke, David T.; Protopapas, Marina; Bonato, Paolo; Burke, John T.; Landrum, Rpbert F.

    2011-01-01

    Purpose To measure the time needed to teach a series of martial arts techniques to proficiency. Methods Fifteen volunteer subjects without any prior martial arts or self-defense experience were recruited. A panel of martial arts experts selected 21 different techniques including defensive stances, arm blocks, elbow strikes, palm strikes, thumbs to eyes, instep kicks and a carotid neck restraint. The critical elements of each technique were identified by the panel and incorporated into a teaching protocol, and then into a scoring system. Two black belt martial arts instructors directed a total of forty-five 45-minute training sessions. Videotaped proficiency testing was performed weekly. The videotapes were reviewed by the investigators to determine the proficiency levels of each subject for each technique. Results The techniques were rated by the average number of training sessions needed for an individual to develop proficiency in that technique. The mean number of sessions necessary to train individuals to proficiency ranged from 27 to 38.3. Using this system, the most difficult techniques seemed to be elbow strikes to the rear, striking with thumbs to the eyes and arm blocking. Conclusions In this study 29 hours of training was necessary to train novice students to be proficient in 21 offensive and defensive martial arts techniques. To our knowledge, this is the first study that attempts to measure the learning curves involved when teaching martial arts techniques. PMID:22375215

  16. Preschool children's learning proclivities: When the ritual stance trumps the instrumental stance.

    PubMed

    Wilks, Matti; Kapitány, Rohan; Nielsen, Mark

    2016-09-01

    Previous research has demonstrated an efficiency bias in social learning whereby young children preferentially imitate the functional actions of a successful individual over an unsuccessful group member. Our aim in the current research was to examine whether this bias remains when actions are presented as conventional rather than instrumental. Preschool children watched videos of an individual and a group member. The individual always demonstrated a successful instrumental action and the group member an unsuccessful action that was either causally transparent or opaque. Highlighting the selective nature of social learning, children copied the group at higher rates when the demonstrated actions were causally opaque than when they were causally transparent. This research draws attention to the influence of conventional/ritual-like actions on young children's learning choices and emphasizes the role of this orientation in the development of human-specific cumulative culture. PMID:26918867

  17. Time outs

    MedlinePlus

    ... this page: //medlineplus.gov/ency/patientinstructions/000756.htm Time outs To use the sharing features on this ... children, 2 to 12 years old. Why Does Time out Work? When you put children in time ...

  18. Flushing Time

    EPA Science Inventory

    The flushing time of an estuary is generally defined as the turnover time of fresh water in the estuary, that is, the time required to replace the fresh water contained in the estuary with freshwater inflow. Thus, the flushing time of an estuary is the ratio of the volume of fres...

  19. Reinventing Time

    ERIC Educational Resources Information Center

    Technology Teacher, 2004

    2004-01-01

    What do planet Earth, a swinging pendulum, a quartz crystal, and a Cesium atom have in common? They have all been used by humans to measure time. They represent humanity's progress through time in measuring time itself. But what is it, really, that humans set out to measure? Before time could be measured, somebody had to decide what to actually…

  20. Chua's Time

    NASA Astrophysics Data System (ADS)

    Buscarino, Arturo; Fortuna, Luigi; Frasca, Mattia

    2013-01-01

    We discuss the relationship between the idea of time of the philosopher Bergson and the concept of time recurrence in chaotic systems. By taking into account the Chua's circuit, we saw that the "Chua's time", i.e., the average recurrence time of trajectories in the Chua's circuit, is able to qualitatively represent the features of the Bergon's time. Numerical and experimental results are presented.

  1. Bleeding time

    MedlinePlus

    Bleeding time is a medical test that measures how fast small blood vessels in the skin stop bleeding. ... until the bleeding stops. The provider records the time it takes for the cuts to stop bleeding.

  2. Entropic Time

    SciTech Connect

    Caticha, Ariel

    2011-03-14

    The formulation of quantum mechanics within the framework of entropic dynamics includes several new elements. In this paper we concentrate on one of them: the implications for the theory of time. Entropic time is introduced as a book-keeping device to keep track of the accumulation of changes. One new feature is that, unlike other concepts of time appearing in the so-called fundamental laws of physics, entropic time incorporates a natural distinction between past and future.

  3. Time Honoured

    ERIC Educational Resources Information Center

    Campbell, Mora; Timmerman, Peter

    2007-01-01

    The vast majority of literature and practices in environmental education focuses on places and spaces. Little attention has been paid to time and temporalities as elements of environments, and the ways in which how we experience time affects our experience of place. This paper is an examination of the ways in which reflection on time can be…

  4. Time Out for Measuring Time.

    ERIC Educational Resources Information Center

    Markle, Sandra

    1983-01-01

    The ability to measure time means being able to arrange events in logical sequences, predict which kinds of events take longer than others, and understand different divisions of time. Teaching methods and class activities that will help children develop skills and concepts concerning time usage are presented. (PP)

  5. TIMING APPARATUS

    DOEpatents

    Bennett, A.E.; Geisow, J.C.H.

    1956-04-17

    The timing device comprises an escapement wheel and pallet, a spring drive to rotate the escapement wheel to a zero position, means to wind the pretensioned spring proportional to the desired signal time, and a cam mechanism to control an electrical signal switch by energizing the switch when the spring has been wound to the desired position, and deenergizing it when it reaches the zero position. This device produces an accurately timed signal variably witain the control of the operator.

  6. Turnover Time

    EPA Science Inventory

    Ecosystems contain energy and materials such as carbon, nitrogen, phosphorus, and water, and are open to their flow-through. Turnover time refers to the amount of time required for replacement by flow-through of the energy or substance of interest contained in the system, and is ...

  7. Time Management

    ERIC Educational Resources Information Center

    Stoilov, Todor, Ed.

    2012-01-01

    The time management is worthy goal of many human activities. It concerns variety problems related to goals definition, assessment of available resources, control of management policies, scheduling of decisions. This book is an attempt to illustrate the decision making process in time management for different success stories, which can be used as…

  8. Managing Time.

    ERIC Educational Resources Information Center

    Murphy, Linda; Della Corte, Suzanne

    1991-01-01

    This newsletter issue discusses time management techniques for parents of special needs children. Techniques include changing one's attitudes about perfection, prioritizing tasks, having a back-up plan, learning to say "no," asking for help, keeping things simple, hiring others, using waiting time wisely, and doing two things at once. Household…

  9. Turnaround time.

    PubMed

    Baumgardner, H W; Boyer, B P; Cavenaugh, B; Keller, C

    1992-01-01

    Advances in instrumentation have enabled laboratories to deliver results much more quickly. But as equipment has advanced so have expectations on turnaround time (TAT), driving up costs in the process. Laboratories must balance the needs of their clients against the need to cover their costs. In this issue, we asked our respondents: How do you address the issue of turnaround time? PMID:10118449

  10. Reaction time in gait initiation depends on the time available for affective processing.

    PubMed

    Gélat, Thierry; Chapus, Carole Ferrel

    2015-11-16

    Previous studies have reported that reaction time in gait initiation was affected by emotion eliciting pictures. This study examined the effect of a change in the delay between image onset and the imperative "go" on reaction time. From a standing posture, 19 young adults had to walk (several steps) toward pleasant or unpleasant images in two conditions. In the short condition, the word "go" appeared 500ms after image onset and participants were instructed to initiate gait as soon as possible after the word go appeared. In the long condition, the same procedure was used but the word "go" appeared 3000ms after image onset. Results demonstrated that motor responses were faster for pleasant pictures than unpleasant ones in the short condition. In contrast, no significant difference was found between both categories of pictures in the long condition. Moreover, we found that self ratings of valence of unpleasant pictures were less unpleasant in the long condition than in the short one whereas there was no difference for pleasant pictures between both conditions. This result reflected a change in the affective significance of unpleasant pictures in the long condition. We also found in the long condition, that the body was inclined forward and to the stance limb during the standing posture and importantly with a similar extent for pleasant and unpleasant pictures. This change clearly reflected a facilitation of the gait initiation process. Overall, results suggested that this gait facilitation when confronted to unpleasant pictures resulted from emotional regulation processes enabling to reappraise these pictures and to override the initial avoidance tendency that they caused. PMID:26455865

  11. Finding time.

    PubMed

    Killeen, Peter R

    2014-01-01

    We understand time through our models of it. These are typically models of our physical chronometers, which we then project into our subjects. A few of these models of the nature of time and its effects on the behavior of organisms are reviewed. New models, such as thermodynamics and spectral decomposition, are recommended for the potential insights that they afford. In all cases, associations are essential features of timing. To make them, time must be discretized by stimuli such as hours, minutes, conditioned stimuli, trials, and contexts in general. Any one association is seldom completely dominant, but rather shares control through proximity in a multidimensional space, important dimensions of which may include physical space and time as rendered by Fourier transforms. PMID:23973706

  12. Time outs

    MedlinePlus

    ... Time-out technique for discipline. Children's Health Network web site. http://www.childrenshealthnetwork.org/CRS/CRS/pa_ ... a break from negative behavior. Massachusetts Medical Society web site. http://www.massmed.org/patient-care/health- ...

  13. Taking Time

    ERIC Educational Resources Information Center

    Perry, Tonya

    2004-01-01

    The opportunity for students to successfully complete the material increases when teachers take time and care about what they are reading. Students can read the contents of a text successfully if they keep their thoughts moving and ideas developing.

  14. Pluto Time

    NASA Video Gallery

    If you stood on Pluto at noon and looked around, the landscape would be illuminated about as brightly as on Earth soon after sunset. The team for NASA's New Horizons mission dubbed this "Pluto Time...

  15. Thrombin Time

    MedlinePlus

    ... monitor unfractionated heparin therapy and to detect heparin contamination in a blood sample. While it is still ... thrombin time may sometimes be ordered when heparin contamination of a sample is suspected or when a ...

  16. Time Out for Time Management.

    ERIC Educational Resources Information Center

    Herr, Judy; And Others

    1995-01-01

    Offers early childhood program administrators time management strategies to increase available time, efficiency, and effectiveness. To manage paper, directors should clear the desk top, use in-out baskets, create a filing system, and handle mail effectively. Tips for managing meetings include preparing an agenda, scheduling meetings for…

  17. Timing During Interruptions in Timing

    ERIC Educational Resources Information Center

    Fortin, Claudette; Bedard, Marie-Claude; Champagne, Julie

    2005-01-01

    Duration and location of breaks in time interval production were manipulated in various conditions of stimulus presentation (Experiments 1-4). Produced intervals shortened and then stabilized as break duration lengthened, suggesting that participants used the break as a preparatory period to restart timing as quickly as possible at the end of the…

  18. About time

    NASA Technical Reports Server (NTRS)

    Denning, Peter J.

    1990-01-01

    Time has historically been a measure of progress of recurrent physical processes. Coordination of future actions, prediction of future events, and assigning order to events are three practical reasons for implementing clocks and signalling mechanisms. In large networks of computers, these needs lead to the problem of synchronizing the clocks throughout the network. Recent methods allow this to be done in large networks with precision around 1 millisecond despite mean message exchange times near 5 milliseconds. These methods are discussed.

  19. Number Time

    ERIC Educational Resources Information Center

    Herrera, Terese A.

    2004-01-01

    This article features Number Time, a site developed by the British Broadcasting Corporation (BBC) for young mathematics learners, located at www.bbc.co.uk/schools/numbertime. The site uses interactive animation to help children in pre-K through grade 2 understand and practice number basics. Users will find online games, videos that tell number…

  20. Geologic Time.

    ERIC Educational Resources Information Center

    Albritton, Claude C., Jr.

    1984-01-01

    Discusses the historical development of the concept of geologic time. Develops the topic by using the major discoveries of geologists, beginning with Steno and following through to the discovery and use of radiometric dating. An extensive reference list is provided. (JM)

  1. Timely arguments.

    PubMed

    Callahan, S

    1991-04-01

    The consideration of time is central to philosophical resolution of issues of protection of human life. The central question is, how much future living is possible at a given point in time. Fetal life merits protection because of the potential for rational self-governance and moral self-consciousness. In contrast, a dying person consciousness or functioning. In the author's view, allowing a comatose person to die reflects the same respect for human life as protecting embryos from abortion. There is no moral justification for using technology to prolong a life when future consciousness is impossible. Viewed from the perspective of future potential, the opposition of many who are part of the antiabortion movement to the removal of feeding tubes from a comatose US woman, Nancy Cruzan, is senseless. PMID:10109972

  2. Nurses' daily life: gender relations from the time spent in hospital1

    PubMed Central

    Pereira, Audrey Vidal

    2015-01-01

    Objective: to analyze the everyday life of nurses through the sexual work division as well as through interdependence relations and the time in hospital. Method: quanti-qualitative study, based on the Time Use Survey and in Norbert Elias's Configuration Theory of Interdependencies. Daily shifts distribution record, directed by 42 participants - with self-confrontation - by interviews which drew dialogues on subjective aspects of the everyday experiences related to use of time, based on a job at a university hospital. The theoretical intake that founded data analysis was based on concepts of conflicts of interest, power struggles, sexual work division and polychronic-monochronic concepts - whether the work environment demands multitasking nurses or not. Results: time records allowed to observe differences between the groups studied, useful to identify conflicts, tensions, power struggles and gender inequalities in interviewees' everyday affairs that do not only affect physical and mental health, but also their way of life. Conclusion: the analytical path pointed out the need for public policies that promote equity in gender relations, keeping at sight the exercise of plural discourses and tolerant stances capable to respect differences between individual and collective time. PMID:26487146

  3. Doing Time

    PubMed Central

    Yang, Suzanne; Kadouri, Alane; Révah-Lévy, Anne; Mulvey, Edward P.; Falissard, Bruno

    2009-01-01

    Once convicted, the perpetrator of serious crime embarks upon a new journey: the challenge of adjusting to long-term imprisonment. Prisoners’ views of incarceration and the meaning of this experience may affect their later adjustment to life in the community. On the basis of brief narrative responses collected during an epidemiological survey of the psychological health of prisoners in France, this study examined the impact of incarceration on psychological state in a group of 59 inmates serving long sentences. Qualitative content analysis and computer-assisted linguistic analysis (using ALCESTE software) were performed on the textual data of open responses to three standard questions. Using a combination of these two approaches, seven categories of the subjective experience of prisoners in the sample were identified: the Outside World, Others, Punishment, Time, Affects and Impulses, Self-Concept, and Speech. Further qualitative analyses were then performed to compare the responses of Severely Mentally Ill (SMI) subjects and subjects with no psychiatric disorder. These analyses revealed contrasting attitudes towards incarceration. SMI subjects spoke in more hostile and persecutory terms about their experience in prison, attributing suffering to external circumstances, while subjects with no psychiatric disorder evoked similar themes, but with an introspective attitude. The themes evoked by mentally ill individuals in our sample suggest that their reactions to the prison environment arise in part from aspects of their psychiatric symptoms, and this may have relevance to future mental health policy and practices in criminal corrections. PMID:19619895

  4. Contribution of the motor cortex to the structure and the timing of hindlimb locomotion in the cat: a microstimulation study.

    PubMed

    Bretzner, Frédéric; Drew, Trevor

    2005-07-01

    We used microstimulation to examine the contribution of the motor cortex to the structure and timing of the hindlimb step cycle during locomotion in the intact cat. Stimulation was applied to the hindlimb representation of the motor cortex in 34 sites in three cats using either standard glass-insulated microelectrodes (16 sites in 1 cat) or chronically implanted microwire electrodes (18 sites in 2 cats). Stimulation at just suprathreshold intensities with the cat at rest produced multi-joint movements at a majority of sites (21/34, 62%) but evoked responses restricted to a single joint, normally the ankle, at the other 13/34 (38%) sites. Stimulation during locomotion generally evoked larger responses than the same stimulation at rest and frequently activated additional muscles. Stimulation at all 34 sites evoked phase-dependent responses in which stimulation in swing produced transient increases in activity in flexor muscles while stimulation during stance produced transient decreases in activity in extensors. Stimulation with long (200 ms) trains of stimuli in swing produced an increased level of activity and duration of flexor muscles without producing changes in cycle duration. In contrast, stimulation during stance decreased the duration of the extensor muscle activity and initiated a new and premature period of swing, resetting the step cycle. Stimulation of the pyramidal tract in two of these three cats as well as in two additional ones produced similar effects. The results show that the motor cortex is capable of influencing hindlimb activity during locomotion in a similar manner to that seen for the forelimb. PMID:15788518

  5. Conveying a Stance of Religious Pluralism in Children's Literature

    ERIC Educational Resources Information Center

    Sanders, Jennifer; Foyil, Kris; Graff, Jennifer M.

    2010-01-01

    Religious discrimination is a global concern, as social dissonance and devastating violence result from religious intolerance. In order to develop socially competent, global citizens and create a peaceful society, religious diversity must be explored in public school classrooms; yet it remains a controversial and seldom addressed topic. Children's…

  6. Place-Based Education: A Transformative Activist Stance

    ERIC Educational Resources Information Center

    Coughlin, Christine A.; Kirch, Susan A.

    2010-01-01

    The ethnography presented by van Eijck and Roth focuses on the activities of people involved in a government funded internship program in conservation and restoration, which was offered by a "multidisciplinary research center" through a local First Nation adult education center. The internship was designed, in partnership with a local non-profit…

  7. Illuminating a Dialectical Transformative Activist Stance in Education

    ERIC Educational Resources Information Center

    Ritchie, Stephen M.

    2008-01-01

    In this essay I comment on Stetsenko's (2008) essay that draws together the work of Vygotsky, Piaget and Dewey, as she attempts to counter the "new" reductionist synthesis in public educational policy. While this theoretical work is helpful, it could be enhanced further by illuminating everyday practices of learners. I pose some questions that…

  8. Urban Teacher Education in Partnership: An Inquiry Stance Sustains Collaboration

    ERIC Educational Resources Information Center

    Stairs, Andrea J.

    2010-01-01

    The relationship between Brighton High School (BHS) and Boston College (BC) spans several decades. Professors from multiple departments at the university--not only teacher educators but professors of psychology, measurement, and arts and sciences--have walked, as regular parts of the school community, the halls of the gothic-style high school…

  9. Reasons Given by UK Churchgoers for Their Stance on Evolution

    ERIC Educational Resources Information Center

    Village, Andrew; Baker, Sylvia

    2013-01-01

    A sample of 661 churchgoers from a range of Christian denominations in the United Kingdom was asked about Darwinian evolution (defined as the common origin of all species, including humans). Respondents were categorised as those who accepted the idea, those who rejected it, and those who were unsure or neutral. People in each category were given a…

  10. Pleasure, Learning, Video Games, and Life: The Projective Stance

    ERIC Educational Resources Information Center

    Gee, James Paul

    2005-01-01

    This article addresses three questions. First, what is the deep pleasure that humans take from video games? Second, what is the relationship between video games and real life? Third, what do the answers to these questions have to do with learning? Good commercial video games are deep technologies for recruiting learning as a form of profound…