Ankle taping does not impair performance in jump or balance tests.

PubMed

Abián-Vicén, Javier; Alegre, Luis M; Fernández-Rodríguez, J Manuel; Lara, Amador J; Meana, Marta; Aguado, Xavier

2008-01-01

This study aimed to investigate the influence of prophylactic ankle taping on two balance tests (static and dynamic balance) and one jump test, in the push off and the landing phase. Fifteen active young subjects (age: 21.0 ± 4.4 years) without previous ankle injuries volunteered for the study. Each participant performed three tests in two different situations: with taping and without taping. The tests were a counter movement jump, static balance, and a dynamic posturography test. The tests and conditions were randomly performed. The path of the center of pressures was measured in the balance tests, and the vertical ground reaction forces were recorded during the push-off and landing phases of the counter movement jump. Ankle taping had no influence on balance performance or in the push off phase of the jump. However, the second peak vertical force value during the landing phase of the jump was 12% greater with ankle taping (0.66 BW, 95% CI -0.64 to 1.96). The use of prophylactic ankle taping had no influence on the balance or jump performance of healthy young subjects. In contrast, the taped ankle increased the second peak vertical force value, which could be related to a greater risk of injury produced by the accumulation of repeated impacts in sports where jumps are frequently performed. Key pointsAnkle taping has no influence on balance performance.Ankle taping does not impair performance during the push-off phase of the jump.Ankle taping could increase the risk of injury during landings by increasing peak forces.

Ankle Taping Does Not Impair Performance in Jump or Balance Tests

PubMed Central

Abián-Vicén, Javier; Alegre, Luis M.; Fernández-Rodríguez, J. Manuel; Lara, Amador J.; Meana, Marta; Aguado, Xavier

2008-01-01

This study aimed to investigate the influence of prophylactic ankle taping on two balance tests (static and dynamic balance) and one jump test, in the push off and the landing phase. Fifteen active young subjects (age: 21.0 ± 4.4 years) without previous ankle injuries volunteered for the study. Each participant performed three tests in two different situations: with taping and without taping. The tests were a counter movement jump, static balance, and a dynamic posturography test. The tests and conditions were randomly performed. The path of the center of pressures was measured in the balance tests, and the vertical ground reaction forces were recorded during the push-off and landing phases of the counter movement jump. Ankle taping had no influence on balance performance or in the push off phase of the jump. However, the second peak vertical force value during the landing phase of the jump was 12% greater with ankle taping (0.66 BW, 95% CI -0.64 to 1.96). The use of prophylactic ankle taping had no influence on the balance or jump performance of healthy young subjects. In contrast, the taped ankle increased the second peak vertical force value, which could be related to a greater risk of injury produced by the accumulation of repeated impacts in sports where jumps are frequently performed. Key pointsAnkle taping has no influence on balance performance.Ankle taping does not impair performance during the push-off phase of the jump.Ankle taping could increase the risk of injury during landings by increasing peak forces. PMID:24149902

Analysis of muscle activation in lower extremity for static balance.

PubMed

Chakravarty, Kingshuk; Chatterjee, Debatri; Das, Rajat Kumar; Tripathy, Soumya Ranjan; Sinha, Aniruddha

2017-07-01

Balance plays an important role for human bipedal locomotion. Degeneration of balance control is prominent in stroke patients, elderly adults and even for majority of obese people. Design of personalized balance training program, in order to strengthen muscles, requires the analysis of muscle activation during an activity. In this paper we have proposed an affordable and portable approach to analyze the relationship between the static balance strategy and activation of various lower extremity muscles. To do that we have considered Microsoft Kinect XBox 360 as a motion sensing device and Wii balance board for measuring external force information. For analyzing the muscle activation pattern related to static balance, participants are asked to do the single limb stance (SLS) exercise on the balance board and in front of the Kinect. Static optimization to minimize the overall muscle activation pattern is carried out using OpenSim, which is an open-source musculoskeletal simulation software. The study is done on ten normal and ten obese people, grouped according to body mass index (BMI). Results suggest that the lower extremity muscles like biceps femoris, psoas major, sartorius, iliacus play the major role for both maintaining the balance using one limb as well as maintaining the flexion of the other limb during SLS. Further investigations reveal that the higher muscle activations of the flexed leg for normal group demonstrate higher strength. Moreover, the lower muscle activation of the standing leg for normal group demonstrate more headroom for the biceps femoris-short-head and psoas major to withstand the load and hence have better static balance control.

Comparative Effects of Different Balance-Training–Progression Styles on Postural Control and Ankle Force Production: A Randomized Controlled Trial

PubMed Central

Cuğ, Mutlu; Duncan, Ashley; Wikstrom, Erik

2016-01-01

Context:  Despite the effectiveness of balance training, the exact parameters needed to maximize the benefits of such programs remain unknown. One such factor is how individuals should progress to higher levels of task difficulty within a balance-training program. Yet no investigators have directly compared different balance-training–progression styles. Objective:  To compare an error-based progression (ie, advance when proficient at a task) with a repetition-based progression (ie, advance after a set amount of repetitions) style during a balance-training program in healthy individuals. Design:  Randomized controlled trial. Setting:  Research laboratory. Patients or Other Participants:  A total of 28 (16 women, 12 men) physically healthy young adults (age = 21.57 ± 3.95 years, height = 171.60 ± 11.03 cm, weight = 72.96 ± 16.18 kg, body mass index = 24.53 ± 3.7). Intervention(s):  All participants completed 12 supervised balance-training sessions over 4 weeks. Each session consisted of a combination of dynamic unstable-surface tasks that incorporated a BOSU ball and lasted about 30 minutes. Main Outcome Measure(s):  Static balance from an instrumented force plate, dynamic balance as measured via the Star Excursion Balance Test, and ankle force production in all 4 cardinal planes of motion as measured with a handheld dynamometer before and after the intervention. Results:  Selected static postural-control outcomes, dynamic postural control, and ankle force production in all planes of motion improved (P < .05). However, no differences between the progression styles were observed (P > .05) for any of the outcome measures. Conclusions:  A 4-week balance-training program consisting of dynamic unstable-surface exercises on a BOSU ball improved dynamic postural control and ankle force production in healthy young adults. These results suggest that an error-based balance-training program is comparable with but not superior to a repetition-based balance-training program in improving postural control and ankle force production in healthy young adults. PMID:26878257

Effect of armor and carrying load on body balance and leg muscle function.

PubMed

Park, Huiju; Branson, Donna; Kim, Seonyoung; Warren, Aric; Jacobson, Bert; Petrova, Adriana; Peksoz, Semra; Kamenidis, Panagiotis

2014-01-01

This study investigated the impact of weight and weight distribution of body armor and load carriage on static body balance and leg muscle function. A series of human performance tests were conducted with seven male, healthy, right-handed military students in seven garment conditions with varying weight and weight distributions. Static body balance was assessed by analyzing the trajectory of center of plantar pressure and symmetry of weight bearing in the feet. Leg muscle functions were assessed by analyzing the peak electromyography amplitude of four selected leg muscles during walking. Results of this study showed that uneven weight distribution of garment and load beyond an additional 9 kg impaired static body balance as evidenced by increased sway of center of plantar pressure and asymmetry of weight bearing in the feet. Added weight on non-dominant side of the body created greater impediment to static balance. Increased garment weight also elevated peak EMG amplitude in the rectus femoris to maintain body balance and in the medial gastrocnemius to increase propulsive force. Negative impacts on balance and leg muscle function with increased carrying loads, particularly with an uneven weight distribution, should be stressed to soldiers, designers, and sports enthusiasts. Copyright © 2013 Elsevier B.V. All rights reserved.

Balance Improvement Effects of Biofeedback Systems with State-of-the-Art Wearable Sensors: A Systematic Review.

PubMed

Ma, Christina Zong-Hao; Wong, Duo Wai-Chi; Lam, Wing Kai; Wan, Anson Hong-Ping; Lee, Winson Chiu-Chun

2016-03-25

Falls and fall-induced injuries are major global public health problems. Balance and gait disorders have been the second leading cause of falls. Inertial motion sensors and force sensors have been widely used to monitor both static and dynamic balance performance. Based on the detected performance, instant visual, auditory, electrotactile and vibrotactile biofeedback could be provided to augment the somatosensory input and enhance balance control. This review aims to synthesize the research examining the effect of biofeedback systems, with wearable inertial motion sensors and force sensors, on balance performance. Randomized and non-randomized clinical trials were included in this review. All studies were evaluated based on the methodological quality. Sample characteristics, device design and study characteristics were summarized. Most previous studies suggested that biofeedback devices were effective in enhancing static and dynamic balance in healthy young and older adults, and patients with balance and gait disorders. Attention should be paid to the choice of appropriate types of sensors and biofeedback for different intended purposes. Maximizing the computing capacity of the micro-processer, while minimizing the size of the electronic components, appears to be the future direction of optimizing the devices. Wearable balance-improving devices have their potential of serving as balance aids in daily life, which can be used indoors and outdoors.

Balance Improvement Effects of Biofeedback Systems with State-of-the-Art Wearable Sensors: A Systematic Review

PubMed Central

Ma, Christina Zong-Hao; Wong, Duo Wai-Chi; Lam, Wing Kai; Wan, Anson Hong-Ping; Lee, Winson Chiu-Chun

2016-01-01

Falls and fall-induced injuries are major global public health problems. Balance and gait disorders have been the second leading cause of falls. Inertial motion sensors and force sensors have been widely used to monitor both static and dynamic balance performance. Based on the detected performance, instant visual, auditory, electrotactile and vibrotactile biofeedback could be provided to augment the somatosensory input and enhance balance control. This review aims to synthesize the research examining the effect of biofeedback systems, with wearable inertial motion sensors and force sensors, on balance performance. Randomized and non-randomized clinical trials were included in this review. All studies were evaluated based on the methodological quality. Sample characteristics, device design and study characteristics were summarized. Most previous studies suggested that biofeedback devices were effective in enhancing static and dynamic balance in healthy young and older adults, and patients with balance and gait disorders. Attention should be paid to the choice of appropriate types of sensors and biofeedback for different intended purposes. Maximizing the computing capacity of the micro-processer, while minimizing the size of the electronic components, appears to be the future direction of optimizing the devices. Wearable balance-improving devices have their potential of serving as balance aids in daily life, which can be used indoors and outdoors. PMID:27023558

Deformation of an Elastic Substrate Due to a Resting Sessile Droplet

NASA Astrophysics Data System (ADS)

Bardall, Aaron; Daniels, Karen; Shearer, Michael

2017-11-01

On a sufficiently soft substrate, a resting fluid droplet will cause significant deformation of the substrate. This deformation is driven by a combination of capillary forces at the contact line and the fluid pressure at the solid surface. These forces are balanced at the surface by the solid traction stress induced by the substrate deformation. Young's Law, which predicts the equilibrium contact angle of the droplet, also indicates an a priori radial force balance for rigid substrates, but not necessarily for soft substrates which deform under loading. It remains an open question whether the contact line transmits a non-zero force tangent to the substrate surface in addition to the conventional normal force. This talk will present a model for the static deformation of the substrate that includes a non-zero tangential contact line force as well as general interfacial energy conditions governing the angle of a two-dimensional droplet. We discuss extensions of this model to non-symmetric droplets and their effect on the static configuration of the droplet/substrate system. NSF #DMS-1517291.

Static balance according to hip joint angle of unsupported leg during one-leg standing.

PubMed

Cha, Ju-Hyung; Kim, Jang-Joon; Ye, Jae-Gwan; Lee, Seul-Ji; Hong, Jeong-Mi; Choi, Hyun-Kyu; Choi, Ho-Suk; Shin, Won-Seob

2017-05-01

[Purpose] This study aimed to determine static balance according to hip joint angle of the unsupported leg during one-leg standing. [Subjects and Methods] Subjects included 45 healthy adult males and females in their 20s. During one-leg standing on the non-dominant leg, the position of the unsupported leg was classified according to hip joint angles of point angle was class. Static balance was then measured using a force plate with eyes open and closed. The total length, sway velocity, maximum deviation, and velocity on the mediolateral and anteroposterior axes of center of pressure were measured. [Results] In balance assessment with eyes open, there were significant differences between groups according to hip joint angle, except for maximum deviation on the anteroposterior axis. In balance assessment with eyes closed, there were significant differences between total length measurements at 0° and 30°, 60° and between 30° and 90°. There were significant differences between sway velocity measurements at 0° and 30° and between 30° and 90°. [Conclusion] Thus, there were differences in static balance according to hip joint angle. It is necessary to clearly identify the hip joint angle during one-leg standing testing.

Balancing a force on the fingertip of a two-dimensional finger model without intrinsic muscles.

PubMed

Spoor, C W

1983-01-01

A slightly flexed human middle finger can balance an external force on the fingertip. Internal stabilization is also possible, which means that the externally unloaded finger can be kept stiff. We want to analyse whether in these situations the intrinsic hand muscles are needed. Distances from tendons to flexion axes are taken from the literature and are substituted in the moment equilibrium equations of a two-dimensional finger model. Diagrams illustrate the statically indeterminate problem of solving tendon forces. The possibilities for equilibrium without intrinsics appear to depend mainly on four tendon-to-joint distances. These distances determine to which of two groups a finger belongs: (1) one in which intrinsics are not necessary for internal stabilization nor for balancing a force on the fingertip in any direction in the sagittal plane; (2) one in which, without intrinsics, internal stabilization is impossible and only dorso-distally directed forces on the fingertip can be balanced.

Interpreting lateral dynamic weight shifts using a simple inverted pendulum model.

PubMed

Kennedy, Michael W; Bretl, Timothy; Schmiedeler, James P

2014-01-01

Seventy-five young, healthy adults completed a lateral weight-shifting activity in which each shifted his/her center of pressure (CoP) to visually displayed target locations with the aid of visual CoP feedback. Each subject's CoP data were modeled using a single-link inverted pendulum system with a spring-damper at the joint. This extends the simple inverted pendulum model of static balance in the sagittal plane to lateral weight-shifting balance. The model controlled pendulum angle using PD control and a ramp setpoint trajectory, and weight-shifting was characterized by both shift speed and a non-minimum phase (NMP) behavior metric. This NMP behavior metric examines the force magnitude at shift initiation and provides weight-shifting balance performance information that parallels the examination of peak ground reaction forces in gait analysis. Control parameters were optimized on a subject-by-subject basis to match balance metrics for modeled results to metric values calculated from experimental data. Overall, the model matches experimental data well (average percent error of 0.35% for shifting speed and 0.05% for NMP behavior). These results suggest that the single-link inverted pendulum model can be used effectively to capture lateral weight-shifting balance, as it has been shown to model static balance. Copyright © 2014 Elsevier B.V. All rights reserved.

Analysis of metal transfer in gas metal arc welding

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

Kim, Y.S.; Eager, T.W.

1993-06-01

Droplet sizes produced in GMAW are predicted using both the static force balance theory and the pinch instability theory as a function of welding current, and the results are compared with experimental measurements. The causes for the deviation of predicted droplet size from measured size are discussed with suggestions for modification of the theories in order to more accurately model metal transfer in GMAW. The mechanism of repelled metal transfer is also discussed. The transition of metal transfer mode has been considered as a critical phenomenon which changes dramatically over a narrow range of welding current. This transition has beenmore » investigated experimentally using high-speed videography which shows that the transition is much more gradual than is generally believed. The mechanism of the transition is discussed using a modified static force balance theory.« less

Rehabilitation of balance disturbances due to chemotherapy-induced peripheral neuropathy: a pilot study.

PubMed

Cammisuli, Sharon; Cavazzi, Enrico; Baldissarro, Eleonora; Leandri, Massimo

2016-08-01

Cancer patients with chemotherapy-induced peripheral neuropathy (CIPN) have sensory and motor deficits leading to inappropriate proprioceptive feedback, impaired postural control, and fall risk. Balance training with computerized force platforms has been successfully used in rehabilitation of balance disturbances, but programs specifically developed for CIPN patients are lacking. This pilot study evaluated a rehabilitation protocol exclusively based on visual computer-feedback balance training (VCFBT) to improve balance in patients with CIPN. Open-label, non-randomized pilot study, 4-week intervention with pre- vs. post-treatment evaluation. Outpatients of the Rehabilitation Institute of the Salvatore Maugeri Foundation, in Genoa, Italy. Seven out-patients with clinical-instrumental diagnosis of CIPN. At admission, patients were administered the Berg Balance Scale (BBS) and underwent static-dynamic posturography using a computerized force platform to objectively quantify their balance impairment. Their performance was compared to values of a normal age-matched population. Patients then underwent 4 weeks of VCFBT (three 60-minute sessions/week). At discharge, BBS and posturography were repeated and the results compared with those at admission. A significant pre- vs. post-treatment improvement was found in balance as measured by static-dynamic posturography (P=0.004) and BBS (P<0.002). Despite caution needed for the low sample size, this pilot study has shown preliminary evidence that intensive rehabilitation, based on VCFBT can produce a significant improvement in balance outcomes. To our knowledge, this is the first report in CIPN patients of a rehabilitation program based exclusively on VCFBT.

A balance and proprioception intervention programme to enhance combat performance in military personnel.

PubMed

Funk, Shany; Jacob, T; Ben-Dov, D; Yanovich, E; Tirosh, O; Steinberg, N

2018-02-01

Optimal functioning of the lower extremities under repeated movements on unstable surfaces is essential for military effectiveness. Intervention training to promote proprioceptive ability should be considered in order to limit the risk for musculoskeletal injuries. The aim of this study was to assess the effect of a proprioceptive intervention programme on static and dynamic postural balance among Israel Defense Forces combat soldiers. Twenty-seven male soldiers, aged 18-20 years, from a physical fitness instructor's course, were randomly divided into two groups matched by age and army unit. The intervention group (INT) underwent 4 weeks of proprioceptive exercises for 10 min daily; the control group underwent 4 weeks of upper body stretching exercises for 10 min daily. All participants were tested pre and postintervention for both static and dynamic postural balance. Significant interaction (condition*pre-post-test*group) was found for static postural balance, indicating that for the INT group, in condition 3 (on an unstable surface-BOSU), the post-test result was significantly better compared with the pretest result (p<0.05). Following intervention, the INT group showed significant correlations between static postural stability in condition 2 (eyes closed) and the dynamic postural stability (length of time walked on the beam following fatigue) ( r ranged from 0.647 to 0.822; p<0.05). The proprioceptive intervention programme for combat soldiers improved static postural balance on unstable surfaces, and improved the correlation between static postural balance in the eyes closed condition and dynamic postural balance following fatigue. Further longitudinal studies are needed to verify the relationship between proprioception programmes, additional weight bearing and the reduction of subsequent injuries in combat soldiers. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Comparison of Static Balance and the Role of Vision in Elite Athletes

PubMed Central

Hammami, Raouf; Behm, David G; Chtara, Mokhtar; Ben Othman, Aymen; Chaouachi, Anis

2014-01-01

When prescribing balance exercises to athletes in different sports, it may be important to recognize performance variations. Indeed, how athletes from different sports perform on balance tests is not well understood. The goal of the present study was to compare static balance and the role of vision among elite sprinters, jumpers and rugby players. The modified clinical test of sensory interaction on balance (mCTSIB) was used to assess the velocity of the center-of-pressure (CoP) on a force platform during a 30 s bipedal quiet standing posture in 4 conditions: firm surface with opened and closed eyes, foam surface with opened and closed eyes. Three-factor ANOVA indicated a significant main effect for groups (F=21.69, df=2, p<0.001, η2 = 0.34). Significant main effect of vision (F=43.20, df=1, p<0.001, η2 = 0.34) and surface (F=193.41, df=1, p<0.001, η2 = 0.70) as well as an interaction between vision (eyes open, eyes closed) and surface (firm and foam) (F=21.79, df=1, p=0.001) were reported in all groups. The subsequent Bonferroni-Dunn post hoc test indicated that rugby players displayed better static balance than sprinters and jumpers (p=0.001). The comparison of sprinters and jumpers did not reveal significant differences (p>0.05). The nature of the sport practiced and the absence of visual control are linked to modify static balance in elite athletes. Coaches and strength and conditioning professionals are recommended to use a variety of exercises to improve balance, including both exercises with opened and closed eyes on progressively challenging surfaces in order to make decisions about tasks and sensory availability during assessment and training. PMID:25114729

Identification of the period of stability in a balance test after stepping up using a simplified cumulative sum.

PubMed

Safieddine, Doha; Chkeir, Aly; Herlem, Cyrille; Bera, Delphine; Collart, Michèle; Novella, Jean-Luc; Dramé, Moustapha; Hewson, David J; Duchêne, Jacques

2017-11-01

Falls are a major cause of death in older people. One method used to predict falls is analysis of Centre of Pressure (CoP) displacement, which provides a measure of balance quality. The Balance Quality Tester (BQT) is a device based on a commercial bathroom scale that calculates instantaneous values of vertical ground reaction force (Fz) as well as the CoP in both anteroposterior (AP) and mediolateral (ML) directions. The entire testing process needs to take no longer than 12 s to ensure subject compliance, making it vital that calculations related to balance are only calculated for the period when the subject is static. In the present study, a method is presented to detect the stabilization period after a subject has stepped onto the BQT. Four different phases of the test are identified (stepping-on, stabilization, balancing, stepping-off), ensuring that subjects are static when parameters from the balancing phase are calculated. The method, based on a simplified cumulative sum (CUSUM) algorithm, could detect the change between unstable and stable stance. The time taken to stabilize significantly affected the static balance variables of surface area and trajectory velocity, and was also related to Timed-up-and-Go performance. Such a finding suggests that the time to stabilize could be a worthwhile parameter to explore as a potential indicator of balance problems and fall risk in older people. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

A theory of wheelchair wheelie performance.

PubMed

Kauzlarich, J J; Thacker, J G

1987-01-01

The results of this analytical study of wheelchair wheelie performance can be summarized into two wheelchair design equations, or rules of thumb, as developed in the paper. The equation containing the significant parameters involved in popping a wheelie for curb climbing is: fh = 0.8 mg theta c.g. [A] where fh is handrim force, m is the mass of the wheelchair + user less rear wheels, g is acceleration of gravity (9.807 m/s2), and theta c.g. is "c.g. angle," i.e., the angle between the vertical through the rear axle and a line connecting the rear axle and the system center-of-gravity. Equation [A] shows that reducing the mass and/or the c.g. angle will make it easier to pop a wheelie. The c.g. angle is reduced by moving the rear axle position forward on the wheelchair. Wheelie balance is the other aspect of performance considered; where the user balances the wheelchair on the rear wheels for going down curbs or just for fun. The ease with which a system can be controlled (balanced) is related to the static stability of the system. The static stability is defined as: omega 2 = mgl/J [B] where J is the mass moment of inertia at the center of gravity of the system about the direction perpendicular to the sideframe. For better wheelchair control during wheelchair balance the static stability should be reduced. Measurements of the value for the polar mass moment of inertia for a typical wheelchair + user of m = 90 kg was found to be J = 8.7 kg-m2. In order to decrease the value of the static stability, Equation [B], one can increase J or decrease m and/or l, where l is the distance from the rear axle to the c.g. of the system. It is also shown that balancing a rod in the palm of the hand (inverted pendulum) is a mathematical problem similar to the wheelie balance problem, and a rod of length 1.56 meters is similar to a wheelchair + user system mass of 90 kg. However, balancing a rod is done primarily by using visual perception, whereas wheelie balance involves human joint proprioceptors and visual plus vestibular (inner ear) perception. Thus, a simple test of determining the shortest length of rod one can balance in the palm of the hand (plus measuring handrim force capability and simple reaction time) may indicate if a wheelchair user will find it easy to do a wheelie balance.

A Theoretical Investigation of Longitudinal Stability of Airplane with Free Controls Including Effect of Friction in Control System

NASA Technical Reports Server (NTRS)

Greenberg, Harry; Sternfield, Leonard

1944-01-01

The relation between the elevator hinge-moment parameters and the control-forces for changes in forward speed and in maneuvers is shown for several values of static stability and elevator mass balance.

Steady hydromagnetic flows in open magnetic fields. II - Global flows with static zones

NASA Technical Reports Server (NTRS)

Tsinganos, K.; Low, B. C.

1989-01-01

A theoretical study of an axisymmetric steady stellar wind with a static zone is presented, with emphasis on the situation where the global magnetic field is symmetrical about the stellar equator and is partially open. In this scenario, the wind escapes in open magnetic fluxes originating from a region at the star pole and a region at an equatorial belt of closed magnetic field in static equilibrium. The two-dimensional balance of the pressure gradient and the inertial, gravitational, and Lorentz forces in different parts of the flow are studied, along with the static interplay between external sources of energy (heating and/or cooling) distributed in the flow and the pressure distribution.

Correlation of ankle eversion to inversion strength ratio and static balance in dominant and non-dominant limbs of basketball players.

PubMed

Dabadghav, Rachana

2016-04-01

To compare ankle eversion to inversion strength ratio (E/I R) and static balance control between the dominant and non-dominant limbs of basketball players and to correlate ankle E/I R and static balance control in the dominant and non-dominant limbs of basketball players. Twenty-one healthy basketball players in the age-group of 18-25 years participated in this study. Isokinetic ankle eversion and inversion muscle strength was assessed at 30°/s and 120°/s in both dominant and non-dominant limbs using the Biodex isokinetic dynamometer. Similarly balance was assessed on a force platform with eyes open and eyes closed in both dominant and non-dominant limbs. Repeated measure ANOVA for strength measurement, found that there was significant main effect of speed, P=0.001 (P<0.05). However, there was no significant main effect in the sides P=0.099 (P<0.05).There was significant main effect of sides with respect to balance. Balance was affected more in non-dominant limb P=0.000 as compared to dominant limb. However, there was not much of a significant difference with eyes open and eyes closed position. The E/I ratio was >1.0 at the angular velocity of 120°/s increasing the chances of ankle injuries in basketball players. There was no correlation between ankle strength and balance in both dominant and non-dominant limbs.

Static and dynamic force/moment measurements in the Eidetics water tunnel

NASA Technical Reports Server (NTRS)

Suarez, Carlos J.; Malcolm, Gerald N.

1994-01-01

Water tunnels have been utilized in one form or another to explore fluid mechanics and aerodynamics phenomena since the days of Leonardo da Vinci. Water tunnel testing is attractive because of the relatively low cost and quick turn-around time to perform flow visualization experiments and evaluate the results. The principal limitation of a water tunnel is that the low flow speed, which provides for detailed visualization, also results in very small hydrodynamic (aerodynamic) forces on the model, which, in the past, have proven to be difficult to measure accurately. However, the advent of semi-conductor strain gage technology and devices associated with data acquisition such as low-noise amplifiers, electronic filters, and digital recording have made accurate measurements of very low strain levels feasible. The principal objective of this research effort was to develop a multi-component strain gage balance to measure forces and moments on models tested in flow visualization water tunnels. A balance was designed that allows measuring normal and side forces, and pitching, yawing and rolling moments (no axial force). The balance mounts internally in the model and is used in a manner typical of wind tunnel balances. The key differences between a water tunnel balance and a wind tunnel balance are the requirement for very high sensitivity since the loads are very low (typical normal force is 0.2 lbs), the need for water proofing the gage elements, and the small size required to fit into typical water tunnel models.

The contribution of postural balance analysis in older adult fallers: A narrative review.

PubMed

Pizzigalli, L; Micheletti Cremasco, M; Mulasso, A; Rainoldi, A

2016-04-01

Falls are a serious health problem for older adults. Several studies have identified the decline of postural balance as one of the main risk factors for falls. Contrary to what may be believed, the capability of force platform measurements to predict falls remains uncertain. The focus of this narrative review is the identification of postural characteristics of older adults at risk of falling using both static and dynamic postural balance assessments. The literature analysis was conducted on Medline/PubMed. The search ended in May 2015. Centre of pressure (CoP) path length, CoP velocity and sway in medial lateral and anterior-posterior are the variables that distinguish older adult fallers from non-fallers. Recommendations to medical personnel on how to provide efficient balance training for older adults are offered, discussing the relevance and limitations of postural stability on static and dynamic board in falling risk prevention. Copyright © 2015 Elsevier Ltd. All rights reserved.

Assessment of postural balance in community-dwelling older adults - methodological aspects and effects of biofeedback-based Nintendo Wii training.

PubMed

Jørgensen, Martin Grønbech

2014-01-01

The overall purpose of this thesis was to examine selected methodological aspects and novel approaches for measuring postural balance older adults, and to examine the effects of biofeedback-based Nintendo Wii training on selected physiological, psychological and functional outcome variables in community-dwelling older adults. In Study I balance control was investigated using force plate analysis of Centre of Pressure (COP) excursion during static bilateral standing in 32 community-dwelling older adults at three different time-points (09:00, 12:30, and 16:00) throughout the day. An overall significant time-of-day effect was observed for all selected COP variables. The greatest change in all COP variables was observed (on average ~15%) between midday (12:30) and the afternoon (16:00), indicating that a systematic time-of-day influence on static postural balance exists in community-dwelling older adults. Consequently, longitudinal (i.e. pre-to-post training) comparisons of postural balance in in older adults with repeated assessments should be conducted at the same time-of-day. In Study II a novel approach for measuring postural balance (using the Nintendo Wii Stillness and Agility tests) was examined for reproducibility and concurrent validity in 30 community-dwelling older adults. While the Nintendo Wii Stillness test showed a high reproducibility, a systematic learning effect between successive sessions was observed for the Agility test. Moderate-to-excellent concurrent validity was seen for the Stillness test. In contrast, the Agility test revealed a poor concurrent validity. In conclusion, the Wii Stillness test seems to represent a low-cost objective reproducible test of postural balance in community-dwelling older adults and appears feasible in various clinical settings. A habituation (familiarization) period is necessary for the Wii Agility test to avoid a systematic learning effect between successive test sessions. Study III investigated the effect of ten weeks of biofeedback-based Nintendo Wii training on static postural balance, mechanical lower limb muscle function, and functional performance in 58 community-dwelling older adults. Additionally, the study investigated the participant motivation for this type of training (Exergaming). Marked improvements in maximal leg muscle strength, rapid force capacity and functional performance were observed following the period of biofeedback-based Nintendo Wii training. Unexpectedly, static bilateral postural balance remained unaltered following the period of intervention. The study participants perceived the Nintendo Wii training as enjoyable and highly motivating, which suggests that this type of exercise may be successfully implemented at senior citizens' centers and/or in the home of the elderly. The results presented in this thesis suggest that strict control of time-of-day is an important methodological aspect when evaluating postural balance in older adults, and an assessment protocol using the Nintendo Wii-Balance Board is reproducible and valid. Biofeedback-based Nintendo Wii exercise intervention appeared unsuccessful in improving static bilateral postural balance, most likely due to a test ceiling effect in the selected outcome measures, but the intervention elicited marked positive changes in various key risk factors associated to fall accidents. Notably, Wii based biofeedback exercise was perceived by the older adults as a highly motivating type of training.

Validity of a jump training apparatus using Wii Balance Board.

PubMed

Yamamoto, Keizo; Matsuzawa, Mamoru

2013-05-01

The dynamic quantification of jump ability is useful for sports performance evaluation. We developed a force measurement system using the Wii Balance Board (WBB). This study was conducted to validate the system in comparison with a laboratory-grade force plate (FP). For a static validation, weights of 10-180kg were put progressively on the WBB put on the FP. The vertical component of the ground reaction force (vGRF) was measured using both devices and compared. For the dynamic validation, 10 subjects without lower limb pathology participated in the study and performed vertical jumping twice on the WBB on the FP. The range of analysis was set from the landing after the first jump to taking off of the second jump. The peak values during the landing phase and jumping phase were obtained and the force-time integral (force impulse) was measured. The relations of the values measured using each device were compared using Pearson's correlation coefficient test and Bland-Altman plots (BAP). Significant correlation (P<.01, r=.99) was found between the values of both devices in the static and the dynamic test. Examination of the BAP revealed a proportion error in the landing phase and showed no relation in the jumping phase between the difference and the mean in the dynamic test. The WBB detects the vGRF in the jumping phase with high precision. Copyright © 2012 Elsevier B.V. All rights reserved.

Balance training using an interactive game to enhance the use of the affected side after stroke.

PubMed

Ciou, Shih-Hsiang; Hwang, Yuh-Shyan; Chen, Chih-Chen; Chen, Shih-Ching; Chou, Shih-Wei; Chen, Yu-Luen

2015-12-01

[Purpose] Stroke and other cerebrovascular diseases are major causes of adult mobility problems. Because stroke immobilizes the affected body part, balance training uses the healthy body part to complete the target movement. The muscle utilization rate on the stroke affected side is often reduced which further hinders affected side functional recovery in rehabilitation. [Subjects and Methods] This study tested a newly-developed interactive device with two force plates to measuring right and left side centers of pressure, to establish its efficacy in the improvement of the static standing ability of patients with hemiplegia. An interactive virtual reality game with different side reaction ratios was used to improve patient balance. The feasibility of the proposed approach was experimentally demonstrated. [Results] Although the non-affected-side is usually used to support the body weight in the standing position, under certain circumstances the patients could switch to using the affected side. A dramatic improvement in static standing balance control was achieved in the eyes open condition. [Conclusion] The proposed dual force plate technique used in this study separately measured the affected and non-affected-side centers of pressure. Based on this approach, different side ratio integration was achieved using an interactive game that helped stroke patients improve balance on the affected side. Only the patient who had suffered stroke relatively recently benefited significantly. The proposed technique is of little benefit for patients whose mobility has stagnated to a certain level.

On the Stability of a Can of Soda

ERIC Educational Resources Information Center

Benesh, G. A.; Olafsen, J. S.

2014-01-01

Stability is often an important consideration in both static and dynamic systems. While introductory students soon grasp the balance of forces required for constant velocity motion, it generally takes longer for them to reliably identify the various torques involved in producing rotational equilibrium. Accelerating systems have the additional…

Static calibration of the RSRA active-isolator rotor balance system

NASA Technical Reports Server (NTRS)

Acree, C. W., Jr.

1987-01-01

The Rotor Systems Research Aircraft (RSRA) active-isolator system is designed to reduce rotor vibrations transmitted to the airframe and to simultaneously measure all six forces and moments generated by the rotor. These loads are measured by using a combination of load cells, strain gages, and hydropneumatic active isolators with built-in pressure gages. The first static calibration of the complete active-isolator rotor balance system was performed in l983 to verify its load-measurement capabilities. Analysis of the data included the use of multiple linear regressions to determine calibration matrices for different data sets and a hysteresis-removal algorithm to estimate in-flight measurement errors. Results showed that the active-isolator system can fulfill most performance predictions. The results also suggested several possible improvements to the system.

Wind tunnel and ground static tests of a .094 scale powered model of a modified T-39 lift/cruise fan V/STOL research airplane

NASA Technical Reports Server (NTRS)

Hunt, D.; Clinglan, J.; Salemann, V.; Omar, E.

1977-01-01

Ground static and wind tunnel test of a scale model modified T-39 airplane are reported. The configuration in the nose and replacement of the existing nacelles with tilting lift/cruise fans. The model was powered with three 14 cm diameter tip driven turbopowered simulators. Forces and moments were measured by an internal strain guage balance. Engine simulator thrust and mass flow were measured by calibrated pressure and temperature instrumentation mounted downstream of the fans. The low speed handling qualities and general aerodynamic characteristics of the modified T-39 were defined. Test variables include thrust level and thrust balance, forward speed, model pitch and sideslip angle at forward speeds, model pitch, roll, and ground height during static tests, lift/cruise fan tilt angle, flap and aileron deflection angle, and horizonal stabilizer angle. The effects of removing the landing gear, the lift/cruise fans, and the tail surfaces were also investigated.

Effects of a salsa dance training on balance and strength performance in older adults.

PubMed

Granacher, Urs; Muehlbauer, Thomas; Bridenbaugh, Stephanie A; Wolf, Madeleine; Roth, Ralf; Gschwind, Yves; Wolf, Irene; Mata, Rui; Kressig, Reto W

2012-01-01

Deficits in static and particularly dynamic postural control and force production have frequently been associated with an increased risk of falling in older adults. The objectives of this study were to investigate the effects of salsa dancing on measures of static/dynamic postural control and leg extensor power in seniors. Twenty-eight healthy older adults were randomly assigned to an intervention group (INT, n = 14, age 71.6 ± 5.3 years) to conduct an 8-week progressive salsa dancing programme or a control group (CON, n = 14, age 68.9 ± 4.7 years). Static postural control was measured during one-legged stance on a balance platform and dynamic postural control was obtained while walking on an instrumented walkway. Leg extensor power was assessed during a countermovement jump on a force plate. Programme compliance was excellent with participants of the INT group completing 92.5% of the dancing sessions. A tendency towards an improvement in the selected measures of static postural control was observed in the INT group as compared to the CON group. Significant group × test interactions were found for stride velocity, length and time. Post hoc analyses revealed significant increases in stride velocity and length, and concomitant decreases in stride time. However, salsa dancing did not have significant effects on various measures of gait variability and leg extensor power. Salsa proved to be a safe and feasible exercise programme for older adults accompanied with a high adherence rate. Age-related deficits in measures of static and particularly dynamic postural control can be mitigated by salsa dancing in older adults. High physical activity and fitness/mobility levels of our participants could be responsible for the nonsignificant findings in gait variability and leg extensor power. Copyright © 2012 S. Karger AG, Basel.

Home-based balance training programme using Wii Fit with balance board for Parkinsons's disease: a pilot study.

PubMed

Esculier, Jean-Francois; Vaudrin, Joanie; Bériault, Patrick; Gagnon, Karine; Tremblay, Louis E

2012-02-01

To evaluate the effects of a home-based balance training programme using visual feedback (Nintendo Wii Fit game with balance board) on balance and functional abilities in subjects with Parkinson's disease, and to compare the effects with a group of paired healthy subjects. Ten subjects with moderate Parkinson's disease and 8 healthy elderly subjects. Subjects participated in a 6-week home-based balance training programme using Nintendo Wii Fit and balance board. Baseline measures were taken before training for the Sit-to-Stand test (STST), Timed-Up-and-Go (TUG), Tinetti Performance Oriented Mobility Assessment (POMA), 10-m walk test, Community Balance and Mobility assessment (CBM), Activities-specific Balance and Confidence scale (ABC), unipodal stance duration, and a force platform. All measurements were taken again after 3 and 6 weeks of training. The Parkinson's disease group significantly improved their results in TUG, STST, unipodal stance, 10-m walk test, CBM, POMA and force platform at the end of the 6-week training programme. The healthy subjects group significantly improved in TUG, STST, unipodal stance and CBM. This pilot study suggests that a home-based balance programme using Wii Fit with balance board could improve static and dynamic balance, mobility and functional abilities of people affected by Parkinson's disease.

At Odds: Reconciling Experimental and Theoretical Results in High School Physics

ERIC Educational Resources Information Center

Gates, Joshua

2009-01-01

For this experiment, students are divided into 2 groups and presented with a static equilibrium force-balance problem to solve. One group works entirely experimentally and the other group theoretically, using Newton's laws. The groups present their seemingly dissimilar results and must reconcile them through discussion. (Contains 3 figures.)

A calibration rig for multi-component internal strain gauge balance using the new design-of-experiment (DOE) approach

NASA Astrophysics Data System (ADS)

Nouri, N. M.; Mostafapour, K.; Kamran, M.

2018-02-01

In a closed water-tunnel circuit, the multi-component strain gauge force and moment sensor (also known as balance) are generally used to measure hydrodynamic forces and moments acting on scaled models. These balances are periodically calibrated by static loading. Their performance and accuracy depend significantly on the rig and the method of calibration. In this research, a new calibration rig was designed and constructed to calibrate multi-component internal strain gauge balances. The calibration rig has six degrees of freedom and six different component-loading structures that can be applied separately and synchronously. The system was designed based on the applicability of formal experimental design techniques, using gravity for balance loading and balance positioning and alignment relative to gravity. To evaluate the calibration rig, a six-component internal balance developed by Iran University of Science and Technology was calibrated using response surface methodology. According to the results, calibration rig met all design criteria. This rig provides the means by which various methods of formal experimental design techniques can be implemented. The simplicity of the rig saves time and money in the design of experiments and in balance calibration while simultaneously increasing the accuracy of these activities.

Cracks in Complex Bodies: Covariance of Tip Balances

NASA Astrophysics Data System (ADS)

Mariano, Paolo Maria

2008-04-01

In complex bodies, actions due to substructural changes alter (in some cases drastically) the force driving the tip of macroscopic cracks in quasi-static and dynamic growth, and must be represented directly. Here it is proven that tip balances of standard and substructural interactions are covariant. In fact, the former balance follows from the Lagrangian density’s requirement of invariance with respect to the action of the group of diffeomorphisms of the ambient space to itself, the latter balance accrues from an analogous invariance with respect to the action of a Lie group over the manifold of substructural shapes. The evolution equation of the crack tip can be obtained by exploiting invariance with respect to relabeling the material elements in the reference place. The analysis is developed by first focusing on general complex bodies that admit metastable states with substructural dissipation of viscous-like type inside each material element. Then we account for gradient dissipative effects that induce nonconservative stresses; the covariance of tip balances in simple bodies follows as a corollary. When body actions and boundary data of Dirichlet type are absent, the standard variational description of quasi-static crack growth is simply extended to the case of complex materials.

Muscle contributions to the acceleration of the whole body centre of mass during recovery from forward loss of balance by stepping in young and older adults.

PubMed

Graham, David F; Carty, Christopher P; Lloyd, David G; Barrett, Rod S

2017-01-01

The purpose of this study was to determine the muscular contributions to the acceleration of the whole body centre of mass (COM) of older compared to younger adults that were able to recover from forward loss of balance with a single step. Forward loss of balance was achieved by releasing participants (14 older adults and 6 younger adults) from a static whole-body forward lean angle of approximately 18 degrees. 10 older adults and 6 younger adults were able to recover with a single step and included in subsequent analysis. A scalable anatomical model consisting of 36 degrees-of-freedom was used to compute kinematics and joint moments from motion capture and force plate data. Forces for 92 muscle actuators were computed using Static Optimisation and Induced Acceleration Analysis was used to compute individual muscle contributions to the three-dimensional acceleration of the whole body COM. There were no significant differences between older and younger adults in step length, step time, 3D COM accelerations or muscle contributions to 3D COM accelerations. The stance and stepping leg Gastrocnemius and Soleus muscles were primarily responsible for the vertical acceleration experienced by the COM. The Gastrocnemius and Soleus from the stance side leg together with bilateral Hamstrings accelerated the COM forwards throughout balance recovery while the Vasti and Soleus of the stepping side leg provided the majority of braking accelerations following foot contact. The Hip Abductor muscles provided the greatest contribution to medial-lateral accelerations of the COM. Deficits in the neuromuscular control of the Gastrocnemius, Soleus, Vasti and Hip Abductors in particular could adversely influence balance recovery and may be important targets in interventions to improve balance recovery performance.

Muscle contributions to the acceleration of the whole body centre of mass during recovery from forward loss of balance by stepping in young and older adults

PubMed Central

Graham, David F.; Carty, Christopher P.; Lloyd, David G.

2017-01-01

The purpose of this study was to determine the muscular contributions to the acceleration of the whole body centre of mass (COM) of older compared to younger adults that were able to recover from forward loss of balance with a single step. Forward loss of balance was achieved by releasing participants (14 older adults and 6 younger adults) from a static whole-body forward lean angle of approximately 18 degrees. 10 older adults and 6 younger adults were able to recover with a single step and included in subsequent analysis. A scalable anatomical model consisting of 36 degrees-of-freedom was used to compute kinematics and joint moments from motion capture and force plate data. Forces for 92 muscle actuators were computed using Static Optimisation and Induced Acceleration Analysis was used to compute individual muscle contributions to the three-dimensional acceleration of the whole body COM. There were no significant differences between older and younger adults in step length, step time, 3D COM accelerations or muscle contributions to 3D COM accelerations. The stance and stepping leg Gastrocnemius and Soleus muscles were primarily responsible for the vertical acceleration experienced by the COM. The Gastrocnemius and Soleus from the stance side leg together with bilateral Hamstrings accelerated the COM forwards throughout balance recovery while the Vasti and Soleus of the stepping side leg provided the majority of braking accelerations following foot contact. The Hip Abductor muscles provided the greatest contribution to medial-lateral accelerations of the COM. Deficits in the neuromuscular control of the Gastrocnemius, Soleus, Vasti and Hip Abductors in particular could adversely influence balance recovery and may be important targets in interventions to improve balance recovery performance. PMID:29069097

Simultaneous drag and flow measurements of Olympic skeleton athletes

NASA Astrophysics Data System (ADS)

Moon, Yae Eun; Digiulio, David; Peters, Steve; Wei, Timothy

2009-11-01

The Olympic sport of skeleton involves an athlete riding a small sled face first down a bobsled track at speeds up to 130 km/hr. In these races, the difference between gold and missing the medal stand altogether can be hundredths of a second per run. As such, reducing aerodynamic drag through proper body positioning is of first order importance. To better study the flow behavior and to improve the performance of the athletes, we constructed a static force balance system on a mock section of a bobsled track. Athlete and the sled are placed on the force balance system which is positioned at the exit of an open loop wind tunnel. Simultaneous drag force and DPIV velocity field measurements were made along with video recordings of body position to aid the athletes in determining their optimal aerodynamic body position.

Strength and Power Training Effects on Lower Limb Force, Functional Capacity, and Static and Dynamic Balance in Older Female Adults.

PubMed

Lopes, Paula Born; Pereira, Gleber; Lodovico, Angélica; Bento, Paulo C B; Rodacki, André L F

2016-03-03

It has been proposed that muscle power is more effective to prevent falls than muscle force production capacity, as rapid reactions are required to allow the postural control. This study aimed to compare the effects of strength and power training on lower limb force, functional capacity, and static and dynamic balance in older female adults. Thirty-seven volunteered healthy women had been allocated into the strength-training group (n = 14; 69 ± 7.3 years, 155 ± 5.6 cm, 72 ± 9.7 kg), the power-training group (n = 12; 67 ± 7.4 years, 153 ± 5.5 cm, 67.2 ± 7 kg), and control group (n = 11; 65 ± 3.1 years, 154 ± 5.6 cm, 70.9 ± 3 kg). After 12 weeks of training, the strength-training and power-training groups increased significantly maximum dynamic strength (29% and 27%), isometric strength (26% and 37%), and step total time (13% and 14%, dynamic balance), respectively. However, only the power-training group increased the rate of torque development (55%) and the functional capacity in 30-second chair stand (22%) and in time up and go tests (-10%). Empirically, power training may reduce the risk of injuries due to lower loads compared to strength training, and consequently, the physical effort demand during the training session is lower. Therefore, power training should be recommended as attractive training stimuli to improve lower limb force, functional capacity, and postural control of older female adults.

Characterization of static balance abilities in elite soccer players by playing position and age.

PubMed

Pau, Massimiliano; Ibba, Gianfranco; Leban, Bruno; Scorcu, Marco

2014-01-01

In this study, we investigated the static balance of adult and adolescent elite soccer players to understand how expertise and playing position influence postural control. Seventy-one national level players were tested using a force platform to acquire Center-of-Pressure (COP) data in uni- and bipedal stance and calculate sway area (SA), COP path length, velocity and displacements. The results show significant differences in postural sway related to age and playing position only for single-limb stance. In particular, midfielders exhibited significantly lower values of SA with respect to defenders (-48%, p = 0.001) and the under-15 players exhibited SA 42-64% higher than all the others (p = 0.001). In the light of planning training or rehabilitation programs specific for each player's role and age, sway measurements may supply useful, objective and reliable information only for the unipedal test as the bipedal standing appears not challenging enough to let differences in balance abilities emerge.

An Impact Study of the Design of Exergaming Parameters on Body Intensity from Objective and Gameplay-Based Player Experience Perspectives, Based on Balance Training Exergame

PubMed Central

2013-01-01

Kinect-based exergames allow players to undertake physical exercise in an interactive manner with visual stimulation. Previous studies focused on investigating physical fitness based on calories or heart rate to ascertain the effectiveness of exergames. However, designing an exergame for specific training purposes, with intensity levels suited to the needs and skills of the players, requires the investigation of motion performance to study player experience. This study investigates how parameters of a Kinect-based exergame, combined with balance training exercises, influence the balance control ability and intensity level the player can tolerate, by analyzing both objective and gameplay-based player experience, and taking enjoyment and difficulty levels into account. The exergame tested required participants to maintain their balance standing on one leg within a posture frame (PF) while a force plate evaluated the player's balance control ability in both static and dynamic gaming modes. The number of collisions with the PF depended on the frame's travel time for static PFs, and the leg-raising rate and angle for dynamic PFs. In terms of center of pressure (COP) metrics, significant impacts were caused by the frame's travel time on MDIST-AP for static PFs, and the leg-raising rate on MDIST-ML and TOTEX for dynamic PFs. The best static PF balance control performance was observed with a larger frame offset by a travel time of 2 seconds, and the worst performance with a smaller frame and a travel time of 1 second. The best dynamic PF performance was with a leg-raising rate of 1 second at a 45-degree angle, while the worst performance was with a rate of 2 seconds at a 90-degree angle. The results demonstrated that different evaluation methods for player experience could result in different findings, making it harder to study the design of those exergames with training purposes based on player experience. PMID:23922716

Effect of somatosensory and neurofeedback training on balance in older healthy adults: a preliminary investigation.

PubMed

Azarpaikan, Atefeh; Taheri Torbati, Hamidreza

2017-10-23

The aim of this study was to assess the effectiveness of balance training with somatosensory and neurofeedback training on dynamic and static balance in healthy, elderly adults. The sample group consisted of 45 healthy adults randomly assigned to one of the three test groups: somatosensory, neurofeedback, and a control. Individualization of the balance program started with pre-tests for static and dynamic balances. Each group had 15- and 30-min training sessions. All groups were tested for static (postural stability) and dynamic balances (Berg Balance Scale) in acquisition and transfer tests (fall risk of stability and timed up and go). Improvements in static and dynamic balances were assessed by somatosensory and neurofeedback groups and then compared with the control group. Results indicated significant improvements in static and dynamic balances in both test groups in the acquisition test. Results revealed a significant improvement in the transfer test in the neurofeedback and somatosensory groups, in static and dynamic conditions, respectively. The findings suggest that these methods of balance training had a significant influence on balance. Both the methods are appropriate to prevent falling in adults. Neurofeedback training helped the participants to learn static balance, while somatosensory training was effective on dynamic balance learning. Further research is needed to assess the effects of longer and discontinuous stimulation with somatosensory and neurofeedback training on balance in elderly adults.

Objective Integrated Assessment of Functional Outcomes in Reduction Mammaplasty

PubMed Central

Passaro, Ilaria; Malovini, Alberto; Faga, Angela; Toffola, Elena Dalla

2013-01-01

Background: The aim of our study was an objective integrated assessment of the functional outcomes of reduction mammaplasty. Methods: The study involved 17 women undergoing reduction mammaplasty from March 2009 to June 2011. Each patient was assessed before surgery and 2 months postoperatively with the original association of 4 subjective and objective assessment methods: a physiatric clinical examination, the Roland Morris Disability Questionnaire, the Berg Balance Scale, and a static force platform analysis. Results: All of the tests proved multiple statistically significant associated outcomes demonstrating a significant improvement in the functional status following reduction mammaplasty. Surgical correction of breast hypertrophy could achieve both spinal pain relief and recovery of performance status in everyday life tasks, owing to a muscular postural functional rearrangement with a consistent antigravity muscle activity sparing. Pain reduction in turn could reduce the antalgic stiffness and improved the spinal range of motion. In our sample, the improvement of the spinal range of motion in flexion matched a similar improvement in extension. Recovery of a more favorable postural pattern with reduction of the anterior imbalance was demonstrated by the static force stabilometry. Therefore, postoperatively, all of our patients narrowed the gap between the actual body barycenter and the ideal one. The static force platform assessment also consistently confirmed the effectiveness of an accurate clinical examination of functional impairment from breast hypertrophy. Conclusions: The static force platform assessment might help the clinician to support the diagnosis of functional impairment from a breast hypertrophy with objectively based data. PMID:25289256

Development of a multicomponent force and moment balance for water tunnel applications, volume 2

NASA Technical Reports Server (NTRS)

Suarez, Carlos J.; Malcolm, Gerald N.; Kramer, Brian R.; Smith, Brooke C.; Ayers, Bert F.

1994-01-01

The principal objective of this research effort was to develop a multicomponent strain gauge balance to measure forces and moments on models tested in flow visualization water tunnels. Static experiments (which are discussed in Volume 1 of this report) were conducted, and the results showed good agreement with wind tunnel data on similar configurations. Dynamic experiments, which are the main topic of this Volume, were also performed using the balance. Delta wing models and two F/A-18 models were utilized in a variety of dynamic tests. This investigation showed that, as expected, the values of the inertial tares are very small due to the low rotating rates required in a low-speed water tunnel and can, therefore, be ignored. Oscillations in pitch, yaw and roll showed hysteresis loops that compared favorably to data from dynamic wind tunnel experiments. Pitch-up and hold maneuvers revealed the long persistence, or time-lags, of some of the force components in response to the motion. Rotary-balance experiments were also successfully performed. The good results obtained in these dynamic experiments bring a whole new dimension to water tunnel testing and emphasize the importance of having the capability to perform simultaneous flow visualization and force/moment measurements during dynamic situations.

Use of the Nintendo Wii Balance Board for Studying Standing Static Balance Control: Technical Considerations, Force-Plate Congruency, and the Effect of Battery Life.

PubMed

Weaver, Tyler B; Ma, Christine; Laing, Andrew C

2017-02-01

The Nintendo Wii Balance Board (WBB) has become popular as a low-cost alternative to research-grade force plates. The purposes of this study were to characterize a series of technical specifications for the WBB, to compare balance control metrics derived from time-varying center of pressure (COP) signals collected simultaneously from a WBB and a research-grade force plate, and to investigate the effects of battery life. Drift, linearity, hysteresis, mass accuracy, uniformity of response, and COP accuracy were assessed from a WBB. In addition, 6 participants completed an eyes-closed quiet standing task on the WBB (at 3 battery life levels) mounted on a force plate while sway was simultaneously measured by both systems. Characterization results were all associated with less than 1% error. R 2 values reflecting WBB sensor linearity were > .99. Known and measured COP differences were lowest at the center of the WBB and greatest at the corners. Between-device differences in quiet stance COP summary metrics were of limited clinical significance. Lastly, battery life did not affect WBB COP accuracy, but did influence 2 of 8 quiet stance WBB parameters. This study provides general support for the WBB as a low-cost alternative to research-grade force plates for quantifying COP movement during standing.

Evaluation of Relationship between Trunk Muscle Endurance and Static Balance in Male Students

PubMed Central

Barati, Amirhossein; SafarCherati, Afsaneh; Aghayari, Azar; Azizi, Faeze; Abbasi, Hamed

2013-01-01

Purpose Fatigue of trunk muscle contributes to spinal instability over strenuous and prolonged physical tasks and therefore may lead to injury, however from a performance perspective, relation between endurance efficient core muscles and optimal balance control has not been well-known. The purpose of this study was to examine the relationship of trunk muscle endurance and static balance. Methods Fifty male students inhabitant of Tehran university dormitory (age 23.9±2.4, height 173.0±4.5 weight 70.7±6.3) took part in the study. Trunk muscle endurance was assessed using Sørensen test of trunk extensor endurance, trunk flexor endurance test, side bridge endurance test and static balance was measured using single-limb stance test. A multiple linear regression analysis was applied to test if the trunk muscle endurance measures significantly predicted the static balance. Results There were positive correlations between static balance level and trunk flexor, extensor and lateral endurance measures (Pearson correlation test, r=0.80 and P<0.001; r=0.71 and P<0.001; r=0.84 and P<0.001, respectively). According to multiple regression analysis for variables predicting static balance, the linear combination of trunk muscle endurance measures was significantly related to the static balance (F (3,46) = 66.60, P<0.001). Endurance of trunk flexor, extensor and lateral muscles were significantly associated with the static balance level. The regression model which included these factors had the sample multiple correlation coefficient of 0.902, indicating that approximately 81% of the variance of the static balance is explained by the model. Conclusion There is a significant relationship between trunk muscle endurance and static balance. PMID:24800004

Instrumented Static and Dynamic Balance Assessment after Stroke Using Wii Balance Boards: Reliability and Association with Clinical Tests

PubMed Central

Bower, Kelly J.; McGinley, Jennifer L.; Miller, Kimberly J.; Clark, Ross A.

2014-01-01

Background and Objectives The Wii Balance Board (WBB) is a globally accessible device that shows promise as a clinically useful balance assessment tool. Although the WBB has been found to be comparable to a laboratory-grade force platform for obtaining centre of pressure data, it has not been comprehensively studied in clinical populations. The aim of this study was to investigate the measurement properties of tests utilising the WBB in people after stroke. Methods Thirty individuals who were more than three months post-stroke and able to stand unsupported were recruited from a single outpatient rehabilitation facility. Participants performed standardised assessments incorporating the WBB and customised software (static stance with eyes open and closed, static weight-bearing asymmetry, dynamic mediolateral weight shifting and dynamic sit-to-stand) in addition to commonly employed clinical tests (10 Metre Walk Test, Timed Up and Go, Step Test and Functional Reach) on two testing occasions one week apart. Test-retest reliability and construct validity of the WBB tests were investigated. Results All WBB-based outcomes were found to be highly reliable between testing occasions (ICC  = 0.82 to 0.98). Correlations were poor to moderate between WBB variables and clinical tests, with the strongest associations observed between task-related activities, such as WBB mediolateral weight shifting and the Step Test. Conclusions The WBB, used with customised software, is a reliable and potentially useful tool for the assessment of balance and weight-bearing asymmetry following stroke. Future research is recommended to further investigate validity and responsiveness. PMID:25541939

Instrumented static and dynamic balance assessment after stroke using Wii Balance Boards: reliability and association with clinical tests.

PubMed

Bower, Kelly J; McGinley, Jennifer L; Miller, Kimberly J; Clark, Ross A

2014-01-01

The Wii Balance Board (WBB) is a globally accessible device that shows promise as a clinically useful balance assessment tool. Although the WBB has been found to be comparable to a laboratory-grade force platform for obtaining centre of pressure data, it has not been comprehensively studied in clinical populations. The aim of this study was to investigate the measurement properties of tests utilising the WBB in people after stroke. Thirty individuals who were more than three months post-stroke and able to stand unsupported were recruited from a single outpatient rehabilitation facility. Participants performed standardised assessments incorporating the WBB and customised software (static stance with eyes open and closed, static weight-bearing asymmetry, dynamic mediolateral weight shifting and dynamic sit-to-stand) in addition to commonly employed clinical tests (10 Metre Walk Test, Timed Up and Go, Step Test and Functional Reach) on two testing occasions one week apart. Test-retest reliability and construct validity of the WBB tests were investigated. All WBB-based outcomes were found to be highly reliable between testing occasions (ICC  = 0.82 to 0.98). Correlations were poor to moderate between WBB variables and clinical tests, with the strongest associations observed between task-related activities, such as WBB mediolateral weight shifting and the Step Test. The WBB, used with customised software, is a reliable and potentially useful tool for the assessment of balance and weight-bearing asymmetry following stroke. Future research is recommended to further investigate validity and responsiveness.

Time series of ground reaction forces following a single leg drop jump landing in elite youth soccer players consist of four distinct phases.

PubMed

Fransz, Duncan P; Huurnink, Arnold; de Boode, Vosse A; Kingma, Idsart; van Dieën, Jaap H

2016-10-01

The single leg drop jump landing test may assess dynamic and static balance abilities in different phases of the landing. However objective definitions of different phases following landing and associated reliability are lacking. Therefore, we determined the existence of possible distinct phases of single leg drop jump landing on a force plate in 82 elite youth soccer players. Three outcome measures were calculated over moving windows of five sizes: center of pressure (COP) speed, COP sway and horizontal ground reaction force (GRF). Per outcome measure, a Factor Analysis was employed with all windows as input variables. It showed that four factors (patterns of variance) largely (>75%) explained the variance across subjects/trials along the 12s time series. Each factor was highly associated with a distinct phase of the time series signal: dynamic (0.4-2.7s), late dynamic (2.5-5.0s), static 1 (5.0-8.3s) and static 2 (8.1-11.7s). Intra-class correlations (ICC) between trials were lower for the dynamic phases (0.45-0.68) than for the static phases (0.60-0.86). The COP speed showed higher ICC's (0.63-0.86) than COP sway (0.45-0.61) and GRF (0.57-0.71) for all four phases. In conclusion, following a drop jump landing unique information is available in four distinct phases. The COP speed is most reliable, with higher reliability in the static phases compared to the dynamic phases. Future studies should assess the sensitivity of information from dynamic, late dynamic and static phases. Copyright © 2016 Elsevier B.V. All rights reserved.

Letting students discover the power, and the limits, of simple models: Coulomb's law

NASA Astrophysics Data System (ADS)

Bohacek, Peter; Vonk, Matthew; Dill, Joseph; Boehm, Emma

2017-09-01

The inverse-square law pops up all over. It's a simplified model of reality that describes light, sound, gravity, and static electricity. But when it's brought up in class, students are often just handed the equations. They rarely have an opportunity to discover Coulomb's law or Newton's law of gravitation for themselves. It's not hard to understand why. A quantitative demonstration of Coulomb's law can be difficult. The forces are smaller than many force sensors can measure and static electricity tends to be finicky. In addition, off-the-shelf units are expensive or difficult to use. As a result, many instructors skip this lab in favor of qualitative demonstrations or simulations. Adolf Cortel sought to remedy this by designing a straightforward experiment for measuring Coulomb's law using charged metalized-glass spheres (Christmas ornaments) and an electronic balance. Building on Cortel's design, we've made a series of video-based experiments that students can use to discover the relationships that underlie electric force.

Balance Performance Is Task Specific in Older Adults.

PubMed

Dunsky, Ayelet; Zeev, Aviva; Netz, Yael

2017-01-01

Balance ability among the elderly is a key component in the activities of daily living and is divided into two types: static and dynamic. For clinicians who wish to assess the risk of falling among their elderly patients, it is unclear if more than one type of balance test can be used to measure their balance impairment. In this study, we examined the association between static balance measures and two dynamic balance field tests. One hundred and twelve community-dwelling older adults (mean age 74.6) participated in the study. They underwent the Tetrax static postural assessment and then performed the Timed Up and Go (TUG) and the Functional Reach (FR) Test as dynamic balance tests. In general, low-moderate correlations were found between the two types of balance tests. For women, age and static balance parameters explained 28.1-40.4% of the variance of TUG scores and 14.6-24% of the variance of FR scores. For men, age and static balance parameters explained 9.5-31.2% of the variance of TUG scores and 23.9-41.7% of the variance of FR scores. Based on our findings, it is suggested that a combination of both static and dynamic tests be used for assessing postural balance ability.

Liquid management in low gravity using baffled rotating containers

NASA Technical Reports Server (NTRS)

Gans, R. F.

1985-01-01

Possible static configurations of liquids in rotating cylindrical containers with baffles evenly spaced in the axial direction are found. The force balance is among surface tension, centrifugal force and gravity. Two instabilities are found in this parameter space: type 1 is the inability of the liquid to form an interface attached to the baffles; type 2 is the inability for multi-baffled configurations to sustain interfaces between each pair of baffles. The type 1 analysis is confirmed through laboratory based equipment. Applications to orbiting containers are discussed.

Liquid management in low gravity using baffled rotating containers

NASA Technical Reports Server (NTRS)

Gans, R. F.

1984-01-01

Possible static configurations of liquids in rotating cylindrical containers with baffles evenly spaced in the axial direction are found. The force balance is among surface tension, centrifugal force and gravity. Two instabilities are found in this parameter space: type 1 is the inability of the liquid to form an interface attached to the baffles; type 2 is the inability for multi-baffled configurations to sustain interfaces between each pair of baffles. The type 1 analysis is confirmed through laboratory based equipment. Applications to orbiting containers are discussed.

Reliability and validity of the Wii Balance Board for assessment of standing balance: A systematic review.

PubMed

Clark, Ross A; Mentiplay, Benjamin F; Pua, Yong-Hao; Bower, Kelly J

2018-03-01

The use of force platform technologies to assess standing balance is common across a range of clinical areas. Numerous researchers have evaluated the low-cost Wii Balance Board (WBB) for its utility in assessing balance, with variable findings. This review aimed to systematically evaluate the reliability and concurrent validity of the WBB for assessment of static standing balance. Articles were retrieved from six databases (Medline, SCOPUS, EMBASE, CINAHL, Web of Science, Inspec) from 2007 to 2017. After independent screening by two reviewers, 25 articles were included. Two reviewers performed the data extraction and quality assessment. Test-retest reliability was investigated in 12 studies, with intraclass correlation coefficients or Pearson's correlation values showing a range from poor to excellent reliability (range: 0.27 to 0.99). Concurrent validity (i.e. comparison with another force platform) was examined in 21 studies, and was generally found to be excellent in studies examining the association between the same outcome measures collected on both devices. For studies reporting predominantly poor to moderate validity, potentially influential factors included the choice of 1) criterion reference (e.g. not a common force platform), 2) test duration (e.g. <30 s for double leg), 3) outcome measure (e.g. comparing a centre of pressure variable from the WBB with a summary score from the force platform), 4) data acquisition platform (studies using Apple iOS reported predominantly moderate validity), and 5) low sample size. In conclusion, evidence suggests that the WBB can be used as a reliable and valid tool for assessing standing balance. Protocol registration number: PROSPERO 2017: CRD42017058122. Copyright © 2018 Elsevier B.V. All rights reserved.

The effects of vestibular stimulation and fatigue on postural control in classical ballet dancers.

PubMed

Hopper, Diana M; Grisbrook, Tiffany L; Newnham, Prudence J; Edwards, Dylan J

2014-01-01

This study aimed to investigate the effects of ballet-specific vestibular stimulation and fatigue on static postural control in ballet dancers and to establish whether these effects differ across varying levels of ballet training. Dancers were divided into three groups: professional, pre-professional, and recreational. Static postural control of 23 dancers was measured on a force platform at baseline and then immediately, 30 seconds, and 60 seconds after vestibular stimulation (pirouettes) and induction of fatigue (repetitive jumps). The professional dancers' balance was unaffected by both the vestibular stimulation and the fatigue task. The pre-professional and recreational dancers' static sway increased following both perturbations. It is concluded that professional dancers are able to compensate for vestibular and fatiguing perturbations due to a higher level of skill-specific motor training.

Association of balance, strength, and power measures in young adults.

PubMed

Muehlbauer, Thomas; Gollhofer, Albert; Granacher, Urs

2013-03-01

The purpose of this study was to investigate the relationship between variables of static/dynamic balance, isometric strength, and power. Twenty-seven young healthy adults (mean age: 23 ± 4 years) performed measurements of static (unperturbed)/dynamic (perturbed) balance, isometric strength (i.e., maximal isometric torque [MIT]; rate of torque development [RTD] of the plantar flexor), and power (i.e., countermovement jump [CMJ] height and power). No significant associations were found between variables of static and dynamic balance (r = -0.090 to +0.329, p > 0.05) and between measures of static/dynamic balance and isometric strength (r = +0.041 to +0.387, p > 0.05) and static/dynamic balance and power (r = -0.076 to +0.218, p > 0.05). Significant positive correlations (r) were detected between variables of power and isometric strength ranging from +0.458 to +0.689 (p < 0.05). Furthermore, simple regression analyses revealed that a 10% increase in mean CMJ height (4.1 cm) was associated with 22.9 N·m and 128.4 N·m·s better MIT and RTD, respectively. The nonsignificant correlation between static and dynamic balance measures and between static/dynamic balance, isometric strength, and power variables implies that these capacities may be independent of each other and may have to be tested and trained complementarily.

Comparison of Static and Dynamic Balance in Female Collegiate Soccer, Basketball, and Gymnastics Athletes

PubMed Central

Bressel, Eadric; Yonker, Joshua C; Kras, John; Heath, Edward M

2007-01-01

Context: How athletes from different sports perform on balance tests is not well understood. When prescribing balance exercises to athletes in different sports, it may be important to recognize performance variations. Objective: To compare static and dynamic balance among collegiate athletes competing or training in soccer, basketball, and gymnastics. Design: A quasi-experimental, between-groups design. Independent variables included limb (dominant and nondominant) and sport played. Setting: A university athletic training facility. Patients or Other Participants: Thirty-four female volunteers who competed in National Collegiate Athletic Association Division I soccer (n = 11), basketball (n = 11), or gymnastics (n = 12). Intervention(s): To assess static balance, participants performed 3 stance variations (double leg, single leg, and tandem leg) on 2 surfaces (stiff and compliant). For assessment of dynamic balance, participants performed multidirectional maximal single-leg reaches from a unilateral base of support. Main Outcome Measure(s): Errors from the Balance Error Scoring System and normalized leg reach distances from the Star Excursion Balance Test were used to assess static and dynamic balance, respectively. Results: Balance Error Scoring System error scores for the gymnastics group were 55% lower than for the basketball group (P = .01), and Star Excursion Balance Test scores were 7% higher in the soccer group than the basketball group (P = .04). Conclusions: Gymnasts and soccer players did not differ in terms of static and dynamic balance. In contrast, basketball players displayed inferior static balance compared with gymnasts and inferior dynamic balance compared with soccer players. PMID:17597942

Analyses of balance and flexibility of obese patients undergoing bariatric surgery

PubMed Central

Benetti, Fernanda Antico; Bacha, Ivan Leo; Junior, Arthur Belarmino Garrido; Greve, Júlia Maria D'Andréa

2016-01-01

OBJECTIVE: To assess the postural control and flexibility of obese subjects before and both six and 12 months after bariatric surgery. To verify whether postural control is related to flexibility following weight reductions resulting from bariatric surgery. METHODS: The sample consisted of 16 subjects who had undergone bariatric surgery. All assessments were performed before and six and 12 months after bariatric surgery. Postural balance was assessed using an Accusuway® portable force platform, and flexibility was assessed using a standard chair sit and reach test (Wells' chair). RESULTS: With the force platform, no differences were observed in the displacement area or velocity from the center of pressure in the mediolateral and anteroposterior directions. The displacement speed from the center of pressure was decreased at the six month after the surgery; however, unchanged from baseline at 12 months post-surgery. Flexibility increased over time according to the three measurements tested. CONCLUSIONS: Static postural balance did not change. The velocity of postural adjustment responses were increased at six months after surgery. Therefore, weight loss promotes increased flexibility. Yet, improvements in flexibility are not related to improvements in balance. PMID:26934236

Axisymmetric and non-axisymmetric exhaust jet induced effects on a V/STOL vehicle design. Part 3: Experimental technique

NASA Technical Reports Server (NTRS)

Schnell, W. C.

1982-01-01

The jet induced effects of several exhaust nozzle configurations (axisymmetric, and vectoring/modulating varients) on the aeropropulsive performance of a twin engine V/STOL fighter design was determined. A 1/8 scale model was tested in an 11 ft transonic tunnel at static conditions and over a range of Mach Numbers from 0.4 to 1.4. The experimental aspects of the static and wind-on programs are discussed. Jet effects test techniques in general, fow through balance calibrations and tare force corrections, ASME nozzle thrust and mass flow calibrations, test problems and solutions are emphasized.

Static stall alleviation using a rail plasma actuator

NASA Astrophysics Data System (ADS)

Choi, Young-Joon; Gray, Miles; Sirohi, Jayant; Raja, Laxminarayan L.

2018-07-01

An experimental study was conducted to investigate the ability of a rail plasma actuator (RailPAc) to alleviate static stall on an airfoil. The RailPAc device consists of parallel rails flush mounted on the upper surface of a VR-12 airfoil, with a high-current (∼1.3 kA) arc bridging the gap between the rails. A Lorentz force (∼0.3 N lasting  ∼1 ms) generated on the arc propels it along the airfoil chord and transfers momentum to the surrounding flow. Experiments were conducted in a low speed wind tunnel at two different Reynolds numbers ( and ) and various static angles of attack (up to  ∼30°). Particle image velocimetry (PIV) was used to measure the flow over the passive and actuated airfoil, while the airfoil lift was measured using a force balance. The experiments showed that the RailPAc promotes flow reattachment and can suppress static stall over a wide range of angles of attack. Operation of a single RailPAc resulted in  ∼40 improvement in post-stall lift and  ∼4° increase in stall angle compared to a passive airfoil with an unpowered RailPAc. The results provide insight into the actuation mechanism and demonstrate, for the first time, the ability of the RailPAc to alleviate static stall on an airfoil.

Influence of visual control, conduction, and central integration on static and dynamic balance in healthy older adults.

PubMed

Perrin, P P; Jeandel, C; Perrin, C A; Béné, M C

1997-01-01

Aging is associated with decreased balance abilities, resulting in an increased risk of fall. In order to appreciate the visual, somatosensory, and central signals involved in balance control, sophisticated methods of posturography assessment have been developed, using static and dynamic tests, eventually associated with electromyographic measurements. We applied such methods to a population of healthy older adults in order to appreciate the respective importance of each of these sensorial inputs in aging individuals. Posture control parameters were recorded on a force-measuring platform in 41 healthy young (age 28.5 +/- 5.9 years) and 50 older (age 69.8 +/- 5.9 years) adults, using a static test and two dynamic tests performed by all individuals first with eyes open, then with eyes closed. The distance covered by the center of foot pressure, sway area, and anteroposterior oscillations were significantly higher, with eyes open or closed, in older people than in young subjects. Significant differences were noted in dynamic tests with longer latency responses in the group of old people. Dynamic recordings in a sinusoidal test had a more regular pattern when performed eyes open in both groups and evidenced significantly greater instability in old people. These data suggest that vision remains important in maintaining postural control while conduction and central integration become less efficient with age.

Effect of revised high-heeled shoes on foot pressure and static balance during standing.

PubMed

Bae, Young-Hyeon; Ko, Mansoo; Park, Young-Soul; Lee, Suk-Min

2015-04-01

[Purpose] The purpose of this study was to investigate the effects of revised high-heeled shoes on the foot pressure ratio and static balance during standing. [Subjects and Methods] A single-subject design was used, 15 healthy women wearing revised high-heeled shoes and general high-heeled shoes in a random order. The foot pressure ratio and static balance scores during standing were measured using a SpaceBalance 3D system. [Results] Forefoot and rearfoot pressures were significantly different between the 2 types of high-heeled shoes. Under the 3 conditions tested, the static balance score was higher for the revised high-heeled shoes than for the general high-heeled shoes, but this difference was not statistically significant. [Conclusion] Revised high-heeled shoes are preferable to general high-heeled shoes, as they result in normalization of normalized foot pressure and a positive effect on static balance.

Effect of revised high-heeled shoes on foot pressure and static balance during standing

PubMed Central

Bae, Young-Hyeon; Ko, Mansoo; Park, Young-Soul; Lee, Suk-Min

2015-01-01

[Purpose] The purpose of this study was to investigate the effects of revised high-heeled shoes on the foot pressure ratio and static balance during standing. [Subjects and Methods] A single-subject design was used, 15 healthy women wearing revised high-heeled shoes and general high-heeled shoes in a random order. The foot pressure ratio and static balance scores during standing were measured using a SpaceBalance 3D system. [Results] Forefoot and rearfoot pressures were significantly different between the 2 types of high-heeled shoes. Under the 3 conditions tested, the static balance score was higher for the revised high-heeled shoes than for the general high-heeled shoes, but this difference was not statistically significant. [Conclusion] Revised high-heeled shoes are preferable to general high-heeled shoes, as they result in normalization of normalized foot pressure and a positive effect on static balance. PMID:25995572

Development of Static Balance Measurement and Correction Compound Platform for Single Blade of Controllable Pitch Propeller

NASA Astrophysics Data System (ADS)

Chao, Zhang; Shijie, Su; Yilin, Yang; Guofu, Wang; Chao, Wang

2017-11-01

Aiming at the static balance of the controllable pitch propeller (CPP), a high efficiency static balance method based on the double-layer structure of the measuring table and gantry robot is adopted to realize the integration of torque measurement and corrected polish for controllable pitch propeller blade. The control system was developed by Microsoft Visual Studio 2015, and a composite platform prototype was developed. Through this prototype, conduct an experiment on the complete process of torque measurement and corrected polish based on a 300kg class controllable pitch propeller blade. The results show that the composite platform can correct the static balance of blade with a correct, efficient and labor-saving operation, and can replace the traditional method on static balance of the blade.

Increased fall risk is associated with elevated co-contraction about the ankle during static balance challenges in older adults.

PubMed

Nelson-Wong, Erika; Appell, Ryan; McKay, Mike; Nawaz, Hannah; Roth, Joanna; Sigler, Robert; Third, Jacqueline; Walker, Mark

2012-04-01

Falls are a leading contributor to disability in older adults. Increased muscle co-contraction in the lower extremities during static and dynamic balance challenges has been associated with aging, and also with a history of falling. Co-contraction during static balance challenges has not been previously linked with performance on clinical tests designed to ascertain fall risk. The purpose of this study was to investigate the relationship between co-contraction about the ankle during static balance challenges with fall risk on a commonly used dynamic balance assessment, the Four Square Step Test (FSST). Twenty-three volunteers (mean age 73 years) performed a series of five static balance challenges (Romberg eyes open/closed, Sharpened Romberg eyes open/closed, and Single Leg Standing) with continuous electromyography (EMG) of bilateral tibialis anterior and gastrocnemius muscles. Participants then completed the FSST and were categorized as 'at-risk' or 'not-at-risk' to fall based on a cutoff time of 12 s. Co-contraction was quantified with co-contraction index (CCI). CCI during narrow base conditions was positively correlated with time to complete FSST. High CCIs during all static balance challenges with the exception of Romberg stance with eyes closed were predictive of being at-risk to fall based on FSST time, odds ratio 19.3. The authors conclude that co-contraction about the ankle during static balance challenges can be predictive of performance on a dynamic balance test.

Effect of yoga training on one leg standing and functional reach tests in obese individuals with poor postural control

PubMed Central

Jorrakate, Chaiyong; Kongsuk, Jutaluk; Pongduang, Chiraprapa; Sadsee, Boontiwa; Chanthorn, Phatchari

2015-01-01

[Purpose] The aim of the present study was to investigate the effect of yoga training on static and dynamic standing balance in obese individuals with poor standing balance. [Subjects and Methods] Sixteen obese volunteers were randomly assigned into yoga and control groups. The yoga training program was performed for 45 minutes per day, 3 times per week, for 4 weeks. Static and dynamic balance were assessed in volunteers with one leg standing and functional reach tests. Outcome measures were tested before training and after a single week of training. Two-way repeated measure analysis of variance with Tukey’s honestly significant difference post hoc statistics was used to analyze the data. [Results] Obese individuals showed significantly increased static standing balance in the yoga training group, but there was no significant improvement of static or dynamic standing balance in the control group after 4 weeks. In the yoga group, significant increases in static standing balance was found after the 2nd, 3rd, and 4th weeks. Compared with the control group, static standing balance in the yoga group was significantly different after the 2nd week, and dynamic standing balance was significantly different after the 4th week. [Conclusion] Yoga training would be beneficial for improving standing balance in obese individuals with poor standing balance. PMID:25642038

Alterations in Body Fluid Balance During Fin Swimming in 29 °C Water in a Population of Special Forces Divers.

PubMed

Castagna, O; Desruelle, A V; Blatteau, J E; Schmid, B; Dumoulin, G; Regnard, J

2015-12-01

Highly trained "combat swimmers" encounter physiological difficulties when performing missions in warm water. The aim of this study was to assess the respective roles of immersion and physical activity in perturbing fluid balance of military divers on duty in warm water. 12 trained divers performed 2 dives each (2 h, 3 m depth) in fresh water at 29 °C. Divers either remained Static or swam continuously (Fin) during the dive. In the Fin condition, oxygen consumption and heart rate were 2-fold greater than during the Static dive. Core and skin temperatures were also higher (Fin: 38.5±0.4 °C and 36.2±0.3 °C and Static: 37.2±0.3 °C and 34.3±0.3 °C; respectively p=0.0002 and p=0.0003). During the Fin dive, the average mass loss was 989 g (39% urine loss, 41% sweating and 20% insensible water loss and blood sampling); Static divers lost 720 g (84% urine loss, 2% sweating and 14% insensible water loss and blood sampling) (p=0.003). In the Fin condition, a greater decrease in total body mass and greater sweating occurred, without effects on circulating renin and aldosterone concentrations; diuresis was reduced, and plasma volume decreased more than in the Static condition. © Georg Thieme Verlag KG Stuttgart · New York.

High-Reynolds Number Active Blowing Semi-Span Force Measurement System Development

NASA Technical Reports Server (NTRS)

Lynn, Keith C.; Rhew, Ray D.; Acheson, Michael J.; Jones, Gregory S.; Milholen, William E.; Goodliff, Scott L.

2012-01-01

Recent wind-tunnel tests at the NASA Langley Research Center National Transonic Facility utilized high-pressure bellows to route air to the model for evaluating aircraft circulation control. The introduction of these bellows within the Sidewall Model Support System significantly impacted the performance of the external sidewall mounted semi-span balance. As a result of this impact on the semi-span balance measurement performance, it became apparent that a new capability needed to be built into the National Transonic Facility s infrastructure to allow for performing pressure tare calibrations on the balance in order to properly characterize its performance under the influence of static bellows pressure tare loads and bellows thermal effects. The objective of this study was to design both mechanical calibration hardware and an experimental calibration design that can be employed at the facility in order to efficiently and precisely perform the necessary loadings in order to characterize the semi-span balance under the influence of multiple calibration factors (balance forces/moments and bellows pressure/temperature). Using statistical design of experiments, an experimental design was developed allowing for strategically characterizing the behavior of the semi-span balance for use in circulation control and propulsion-type flow control testing at the National Transonic Facility.

Analysis of static and dynamic balance in healthy elderly practitioners of Tai Chi Chuan versus ballroom dancing

PubMed Central

Rahal, Miguel Antônio; Alonso, Angélica Castilho; Andrusaitis, Felix Ricardo; Rodrigues, Thuam Silva; Speciali, Danielli Souza; Greve, Júlia Maria D′Andréa; Leme, Luiz Eugênio Garcez

2015-01-01

OBJECTIVE: To determine whether Tai Chi Chuan or ballroom dancing promotes better performance with respect to postural balance, gait, and postural transfer among elderly people. METHODS: We evaluated 76 elderly individuals who were divided into two groups: the Tai Chi Chuan Group and the Dance Group. The subjects were tested using the NeuroCom Balance Master® force platform system with the following protocols: static balance tests (the Modified Clinical Tests of Sensory Interaction on Balance and Unilateral Stance) and dynamic balance tests (the Walk Across Test and Sit-to-stand Transfer Test). RESULTS: In the Modified Clinical Test of Sensory Interaction on Balance, the Tai Chi Chuan Group presented a lower sway velocity on a firm surface with open and closed eyes, as well as on a foam surface with closed eyes. In the Modified Clinical Test of Sensory Interaction on Unilateral Stance, the Tai Chi Chuan Group presented a lower sway velocity with open eyes, whereas the Dance Group presented a lower sway velocity with closed eyes. In the Walk Across Test, the Tai Chi Chuan Group presented faster walking speeds than those of the Dance Group. In the Sit-to-stand Transfer Test, the Tai Chi Chuan Group presented shorter transfer times from the sitting to the standing position, with less sway in the final standing position. CONCLUSION: The elderly individuals who practiced Tai Chi Chuan had better bilateral balance with eyes open on both types of surfaces compared with the Dance Group. The Dance Group had better unilateral postural balance with eyes closed. The Tai Chi Chuan Group had faster walking speeds, shorter transfer times, and better postural balance in the final standing position during the Sit-to-stand Test. PMID:26017644

Analysis of static and dynamic balance in healthy elderly practitioners of Tai Chi Chuan versus ballroom dancing.

PubMed

Rahal, Miguel Antônio; Alonso, Angélica Castilho; Andrusaitis, Felix Ricardo; Rodrigues, Thuam Silva; Speciali, Danielli Souza; Greve, Júlia Maria D Andréa; Leme, Luiz Eugênio Garcez

2015-03-01

To determine whether Tai Chi Chuan or ballroom dancing promotes better performance with respect to postural balance, gait, and postural transfer among elderly people. We evaluated 76 elderly individuals who were divided into two groups: the Tai Chi Chuan Group and the Dance Group. The subjects were tested using the NeuroCom Balance Master¯ force platform system with the following protocols: static balance tests (the Modified Clinical Tests of Sensory Interaction on Balance and Unilateral Stance) and dynamic balance tests (the Walk Across Test and Sit-to-stand Transfer Test). In the Modified Clinical Test of Sensory Interaction on Balance, the Tai Chi Chuan Group presented a lower sway velocity on a firm surface with open and closed eyes, as well as on a foam surface with closed eyes. In the Modified Clinical Test of Sensory Interaction on Unilateral Stance, the Tai Chi Chuan Group presented a lower sway velocity with open eyes, whereas the Dance Group presented a lower sway velocity with closed eyes. In the Walk Across Test, the Tai Chi Chuan Group presented faster walking speeds than those of the Dance Group. In the Sit-to-stand Transfer Test, the Tai Chi Chuan Group presented shorter transfer times from the sitting to the standing position, with less sway in the final standing position. The elderly individuals who practiced Tai Chi Chuan had better bilateral balance with eyes open on both types of surfaces compared with the Dance Group. The Dance Group had better unilateral postural balance with eyes closed. The Tai Chi Chuan Group had faster walking speeds, shorter transfer times, and better postural balance in the final standing position during the Sit-to-stand Test.

Balance, Proprioception, and Gross Motor Development of Chinese Children Aged 3 to 6 Years.

PubMed

Jiang, Gui-Ping; Jiao, Xi-Bian; Wu, Sheng-Kou; Ji, Zhong-Qiu; Liu, Wei-Tong; Chen, Xi; Wang, Hui-Hui

2018-01-01

The authors' aim was to find the features of balance, proprioception, and gross motor development of Chinese children 3-6 years old and their correlations, provide theoretical support for promoting children's motor development, and enrich the world theoretical system of motor development. This study used a Tekscan foot pressure measurement instrument (Tekscan, Inc., Boston, MA), walking on a balance beam, Xsens 3-dimensional positional measuring system (Xsens Technologies, Enschede, the Netherlands), and Test of Gross Motor Development-2 to assess static balance, dynamic balance, knee proprioception, and levels of gross motor development (GMD) of 3- to 6-year-old children (n = 60) in Beijing. The results are as follows: children had significant age differences in static balance, dynamic balance, proprioception, and levels of GMD; children had significant gender differences in static balance, proprioception, and levels of GMD; children's static balance, dynamic balance, and proprioception had a very significant positive correlation with GMD (p < .01), but no significant correlation with body mass index.

MHD Forces in Quasi-Static Evolution, Catastrophe, and ``Failed'' Eruption of Solar Flux Ropes

NASA Astrophysics Data System (ADS)

Chen, James

2017-08-01

This paper presents the first unified theoretical model of flux rope dynamics---a single set of flux-rope equations in ideal MHD---to describe as one dynamical process the quasi-static evolution, catastrophic transition to eruption, cessation (``failure'') of eruption, and the post-eruption quasi-equilibria. The model is defined by the major radial {\\it and} minor radial equations of motion including pressure. The initial equilibrium is a flux rope in a background plasma with pressure $p_c(Z)$ and an overlying magnetic field $B_c(Z)$. The flux rope is initially force-free, but theevolution is not required to be force- free. A single quasi-static control parameter, the rate of increase in poloidal flux, is used for the entire process. As this parameter is slowly increased, the flux rope rises, following a sequence of quasi-static equilibria. As the apex of the flux rope rises past a critical height $Z_{crt}$, it expands on a dynamical (Alfvénic) timescale. The eruption rapidly ceases, as the stored magnetic energy of eruption is exhausted, and a new equilibrium is established at height $Z_1 > Z_{crt}$. The calculated velocity profile resembles the observed velocity profiles in ``failed'' eruptions including a damped oscillation. In the post-eruption equilibria, the outward hoop force is balanced by the tension of the toroidal self magnetic field and pressure gradient force. Thus, the flux rope does not evolve in a force-free manner. The flux rope may also expand without reaching a new equilibrium, provided a sufficient amount of poloidal flux is injected on the timescale of eruption. This scenario results in a full CME eruption. It is shown that the minor radial expansion critically couples the evolution of the toroidal self-field and pressure gradient force. No parameter regime is found in which the commonly used simplifications---near-equilibrium minor radial expansion, force-free expansion, and constant aspect ratio $R/a$ (e.g., the torus instability equation)---are valid.Work supported by the Naval Research Laboratory Base Research Program

Static Standing Balance in Adolescents with Down Syndrome

ERIC Educational Resources Information Center

Villarroya, M. Adoracion; Gonzalez-Aguero, Alejandro; Moros-Garcia, Teresa; de la Flor Marin, Mario; Moreno, Luis A.; Casajus, Jose A.

2012-01-01

Aim: To analyse static-standing-balance of adolescents with Down syndrome (DS). Methods: Thirty-two adolescents with DS aged 10-19 years (DSG); 33 adolescents, age/sex-matched, without DS (CG). Static-standing-balance under four conditions (C1: open-eyes/fixed-foot-support; C2: closed-eyes/fixed-foot-support; C3: open-eyes/compliant-foot-support;…

Modifications to the nozzle test chamber to extend nozzle static-test capability

NASA Technical Reports Server (NTRS)

Keyes, J. W.

1985-01-01

The nozzle test chamber was modified to provide a high-pressure-ratio nozzle static-test capability. Experiments were conducted to determine the range of the ratio of nozzle total pressure to chamber pressure and to make direct nozzle thrust measurements using a three-component strain-gage force balance. Pressure ratios from 3 to 285 were measured with several axisymmetric nozzles at a nozzle total pressure of 15 to 190 psia. Devices for measuring system mass flow were calibrated using standard axisymmetric convergent choked nozzles. System mass-flow rates up to 10 lbm/sec are measured. The measured thrust results of these nozzles are in good agreement with one-dimensional theoretical predictions for convergent nozzles.

Static Balance: A Comparative Study of Primary Age Boys and Girls.

ERIC Educational Resources Information Center

DiNucci, James M.

The ability to attain and maintain a body position or balance is considered important in learning and performing motor skills. Static balance is defined as balance in which the body maintains equilibrium for one position; dynamic balance is described as maintaining equilibrium while the body is in motion or changing from one balanced position to…

Effect of ankle proprioceptive exercise on static and dynamic balance in normal adults.

PubMed

Yong, Min-Sik; Lee, Yun-Seob

2017-02-01

[Purpose] The present study was conducted to investigate whether ankle proprioceptive exercise affects static and dynamic balance in normal adults. [Subjects and Methods] Twenty-eight normal adults were recruited to measure their static and dynamic balancing before and after the proprioceptive exercise. A subject stood with bare feet on the round supporting platform of the device for measuring balance, and the investigator entered the age and the height of the subjects and set his/her feet on the central point of the monitor screen. Training of ankle proprioceptive sense for the movements of plantar-flexion and dorsiflexion was performed. In the training of joint position sense in plantar-flexion and dorsiflexion, the plantar-flexion and the dorsiflexion were set as 15°, respectively. [Results] The static balancing did not show significant differences in average, while the dynamic balancing showed significant differences. [Conclusion] Ankle proprioceptive exercise can affect dynamic balance.

Measures of static postural control moderate the association of strength and power with functional dynamic balance.

PubMed

Forte, Roberta; Boreham, Colin A G; De Vito, Giuseppe; Ditroilo, Massimiliano; Pesce, Caterina

2014-12-01

Age-related reductions in strength and power are considered to negatively impact balance control, but the existence of a direct association is still an issue of debate. This is possibly due to the fact that balance assessment is complex, reflects different underlying physiologic mechanisms and involves quantitative measurements of postural sway or timing of performance during balance tasks. The present study evaluated the moderator effect of static postural control on the association of power and strength with dynamic balance tasks. Fifty-seven healthy 65-75 year old individuals performed tests of dynamic functional balance (walking speed under different conditions) and of strength, power and static postural control. Dynamic balance performance (walking speed) was associated with lower limb strength and power, as well as postural control under conditions requiring postural adjustments (narrow surface walking r(2) = 0.31, p < 0.001). An interaction effect between strength and static postural control was found with narrow surface walking and talking while walking (change of β 0.980, p < 0.001 in strength for 1 SD improvements in static postural control for narrow walking, and [Formula: see text] -0.730, p < 0.01 in talking while walking). These results indicate that good static postural control facilitates the utilisation of lower limb strength to better perform complex, dynamic functional balance tasks. Practical implications for assessment and training are discussed.

Efficacy of Nintendo Wii training on mechanical leg muscle function and postural balance in community-dwelling older adults: a randomized controlled trial.

PubMed

Jorgensen, Martin G; Laessoe, Uffe; Hendriksen, Carsten; Nielsen, Ole Bruno Faurholt; Aagaard, Per

2013-07-01

Older adults show increased risk of falling and major risk factors include impaired lower extremity muscle strength and postural balance. However, the potential positive effect of biofeedback-based Nintendo Wii training on muscle strength and postural balance in older adults is unknown. This randomized controlled trial examined postural balance and muscle strength in community-dwelling older adults (75±6 years) pre- and post-10 weeks of biofeedback-based Nintendo Wii training (WII, n = 28) or daily use of ethylene vinyl acetate copolymer insoles (controls [CON], n = 30). Primary end points were maximal muscle strength (maximal voluntary contraction) and center of pressure velocity moment during bilateral static stance. Intention-to-treat analysis with adjustment for age, sex, and baseline level showed that the WII group had higher maximal voluntary contraction strength (18%) than the control group at follow up (between-group difference = 269 N, 95% CI = 122; 416, and p = .001). In contrast, the center of pressure velocity moment did not differ (1%) between WII and CON at follow-up (between-group difference = 0.23 mm(2)/s, 95% CI = -4.1; 4.6, and p = .92). For secondary end points, pre-to-post changes favoring the WII group were evident in the rate of force development (p = .03), Timed Up and Go test (p = .01), short Falls Efficacy Scale-International (p = .03), and 30-second repeated Chair Stand Test (p = .01). Finally, participants rated the Wii training highly motivating at 5 and 10 weeks into the intervention. Biofeedback-based Wii training led to marked improvements in maximal leg muscle strength (maximal voluntary contraction; rate of force development) and overall functional performance in community-dwelling older adults. Unexpectedly, static bilateral postural balance remained unaltered with Wii training. The high level of participant motivation suggests that biofeedback-based Wii exercise may ensure a high degree of compliance to home- and/or community-based training in community-dwelling older adults.

The Effects of Two Different Stretching Programs on Balance Control and Motor Neuron Excitability

ERIC Educational Resources Information Center

Kaya, Fatih; Biçer, Bilal; Yüktasir, Bekir; Willems, Mark E. T.; Yildiz, Nebil

2018-01-01

We examined the effects of training (4d/wk for 6 wks) with static stretching (SS) or contract-relax proprioceptive neuromuscular facilitation (PNF) on static balance time and motor neuron excitability. Static balance time, H[subscript max]/M[subscript max] ratios and H-reflex recovery curves (HRRC) were measured in 28 healthy subjects (SS: n = 10,…

Rapid Assessment of Age-Related Differences in Standing Balance

PubMed Central

Kalisch, Tobias; Kattenstroth, Jan-Christoph; Noth, Sebastian; Tegenthoff, Martin; Dinse, Hubert R.

2011-01-01

As life expectancy continues to rise, in the future there will be an increasing number of older people prone to falling. Accordingly, there is an urgent need for comprehensive testing of older individuals to collect data and to identify possible risk factors for falling. Here we use a low-cost force platform to rapidly assess deficits in balance under various conditions. We tested 21 healthy older adults and 24 young adults during static stance, unidirectional and rotational displacement of their centre of pressure (COP). We found an age-related increase in postural sway during quiet standing and a reduction of maximal COP displacement in unidirectional and rotational displacement tests. Our data show that even low-cost computerized assessment tools allow for the comprehensive testing of balance performance in older subjects. PMID:21629742

The energy cost for balance control during upright standing.

PubMed

Houdijk, Han; Fickert, Richard; van Velzen, Judith; van Bennekom, Coen

2009-08-01

The aim of this study was to investigate whether balance control during a static upright standing task with and without balance perturbations elicits a significant and meaningful metabolic energy demand and to test whether this energy demand correlates with conventional posturography measures for balance control. Ten healthy subjects were assessed in four 4-min upright standing conditions on a force platform while energy consumption was measured using open circuit respirometry. In the reference condition subjects stood upright in parallel stance without balance perturbation (PS). In the other conditions balance was perturbed by placing the subjects in tandem stance (TS), in tandem stance blind folded (TSBF) and in tandem stance on a balance board (TSBB). Gross and net energy consumption was assessed and various conventional posturography measures were derived from the excursion of the center of pressure (CoP) of the ground reaction force. Energy consumption was substantially affected by all balance perturbations, compared to the reference condition. The highest increase in energy consumption was found for the TSBF condition (increase of 0.86 J kg(-1)s(-1) or 60% of PS). Significant correlations were found between energy consumption and posturography measures. The strongest correlation was found between gross energy consumption and the CoP path and normalized CoP path along the anterior-posterior axis (resp. r=0.57 and r=0.66, p<0.001). It was concluded that the effort for balance control can elicit a meaningful metabolic energy demand. Conventional posturography provided significant, though moderate, predictors of this metabolic effort for balance control.

Concussion History and Time Since Concussion Do not Influence Static and Dynamic Balance in Collegiate Athletes.

PubMed

Merritt, Eric D; Brown, Cathleen N; Queen, Robin M; Simpson, Kathy J; Schmidt, Julianne D

2017-11-01

Dynamic balance deficits exist following a concussion, sometimes years after injury. However, clinicians lack practical tools for assessing dynamic balance. To determine if there are significant differences in static and dynamic balance performance between individuals with and without a history of concussion. Cross sectional. Clinical research laboratory. 45 collegiate student-athletes with a history of concussion (23 males, 22 females; age = 20.0 ± 1.4 y; height = 175.8 ± 11.6 cm; mass = 76.4 ± 19.2 kg) and 45 matched controls with no history of concussion (23 males, 22 females; age = 20.0 ± 1.3 y; height = 178.8 ± 13.2 cm; mass = 75.7 ± 18.2 kg). Participants completed a static (Balance Error Scoring System) and dynamic (Y Balance Test-Lower Quarter) balance assessment. A composite score was calculated from the mean normalized Y Balance Test-Lower Quarter reach distances. Firm, foam, and overall errors were counted during the Balance Error Scoring System by a single reliable rater. One-way ANOVAs were used to compare balance performance between groups. Pearson's correlations were performed to determine the relationship between the time since the most recent concussion and balance performance. A Bonferonni adjusted a priori α < 0.025 was used for all analyses. Static and dynamic balance performance did not significantly differ between groups. No significant correlation was found between the time since the most recent concussion and balance performance. Collegiate athletes with a history of concussion do not present with static or dynamic balance deficits when measured using clinical assessments. More research is needed to determine whether the Y Balance Test-Lower Quarter is sensitive to acute balance deficits following concussion.

Performance tradeoffs in static and dynamic load balancing strategies

NASA Technical Reports Server (NTRS)

Iqbal, M. A.; Saltz, J. H.; Bokhart, S. H.

1986-01-01

The problem of uniformly distributing the load of a parallel program over a multiprocessor system was considered. A program was analyzed whose structure permits the computation of the optimal static solution. Then four strategies for load balancing were described and their performance compared. The strategies are: (1) the optimal static assignment algorithm which is guaranteed to yield the best static solution, (2) the static binary dissection method which is very fast but sub-optimal, (3) the greedy algorithm, a static fully polynomial time approximation scheme, which estimates the optimal solution to arbitrary accuracy, and (4) the predictive dynamic load balancing heuristic which uses information on the precedence relationships within the program and outperforms any of the static methods. It is also shown that the overhead incurred by the dynamic heuristic is reduced considerably if it is started off with a static assignment provided by either of the other three strategies.

A point of application study to determine the accuracy, precision and reliability of a low-cost balance plate for center of pressure measurement.

PubMed

Goble, Daniel J; Khan, Ehran; Baweja, Harsimran S; O'Connor, Shawn M

2018-04-11

Changes in postural sway measured via force plate center of pressure have been associated with many aspects of human motor ability. A previous study validated the accuracy and precision of a relatively new, low-cost and portable force plate called the Balance Tracking System (BTrackS). This work compared a laboratory-grade force plate versus BTrackS during human-like dynamic sway conditions generated by an inverted pendulum device. The present study sought to extend previous validation attempts for BTrackS using a more traditional point of application (POA) approach. Computer numerical control (CNC) guided application of ∼155 N of force was applied five times to each of 21 points on five different BTrackS Balance Plate (BBP) devices with a hex-nose plunger. Results showed excellent agreement (ICC > 0.999) between the POAs and measured COP by the BBP devices, as well as high accuracy (<1% average percent error) and precision (<0.1 cm average standard deviation of residuals). The ICC between BBP devices was exceptionally high (ICC > 0.999) providing evidence of almost perfect inter-device reliability. Taken together, these results provide an important, static corollary to the previously obtained dynamic COP results from inverted pendulum testing of the BBP. Copyright © 2018 Elsevier Ltd. All rights reserved.

Is standing balance altered in individuals with chronic low back pain? A systematic review.

PubMed

Berenshteyn, Yevgeniy; Gibson, Kelsey; Hackett, Gavin C; Trem, Andrew B; Wilhelm, Mark

2018-01-30

To examine the static standing balance of individuals with chronic low back pain when compared to a healthy control group. A search of available literature was done using PubMed, SPORTDiscus, CINAHL, and Scopus databases. Studies were included if they contained the following: (1) individuals with chronic low back pain 3 months or longer; (2) healthy control group; (3) quantified pain measurement; and (4) center of pressure measurement using a force plate. Two authors independently reviewed articles for inclusion, and assessed for quality using the Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross Sectional Studies. Cohen's d effect size was calculated to demonstrate the magnitude of differences between groups. Nine articles were included in this review. Quality scores ranged from 5/8 to 8/8. Although center of pressure measures were nonhomogeneous, subjects with chronic low back pain had poorer performance overall compared to healthy controls. Despite inconsistencies in statistical significance, effect sizes were frequently large, indicating a lack of sufficient power in the included studies. Data were insufficiently reported among certain studies, limiting the ability of direct study comparison. Results suggest that balance is impaired in individuals with chronic low back pain when compared to healthy individuals. Implications for rehabilitation Static balance is affected in individuals with chronic low back pain. Balance assessments should be completed for individuals with chronic low back pain. Results from balance assessments should be used to indicate areas of improvement and help guide the course of treatment, as well as reassess as treatment progresses.

Summary of comprehensive systematic review: Rehabilitation in multiple sclerosis

PubMed Central

Haselkorn, Jodie K.; Hughes, Christina; Rae-Grant, Alex; Henson, Lily Jung; Bever, Christopher T.; Lo, Albert C.; Brown, Theodore R.; Kraft, George H.; Getchius, Thomas; Gronseth, Gary; Armstrong, Melissa J.; Narayanaswami, Pushpa

2015-01-01

Objective: To systematically review the evidence regarding rehabilitation treatments in multiple sclerosis (MS). Methods: We systematically searched the literature (1970–2013) and classified articles using 2004 American Academy of Neurology criteria. Results: This systematic review highlights the paucity of well-designed studies, which are needed to evaluate the available MS rehabilitative therapies. Weekly home/outpatient physical therapy (8 weeks) probably is effective for improving balance, disability, and gait (MS type unspecified, participants able to walk ≥5 meters) but probably is ineffective for improving upper extremity dexterity (1 Class I). Inpatient exercises (3 weeks) followed by home exercises (15 weeks) possibly are effective for improving disability (relapsing-remitting MS [RRMS], primary progressive MS [PPMS], secondary progressive MS [SPMS], Expanded Disability Status Scale [EDSS] 3.0–6.5) (1 Class II). Six weeks' worth of comprehensive multidisciplinary outpatient rehabilitation possibly is effective for improving disability/function (PPMS, SPMS, EDSS 4.0–8.0) (1 Class II). Motor and sensory balance training or motor balance training (3 weeks) possibly is effective for improving static and dynamic balance, and motor balance training (3 weeks) possibly is effective for improving static balance (RRMS, SPMS, PPMS) (1 Class II). Breathing-enhanced upper extremity exercises (6 weeks) possibly are effective for improving timed gait and forced expiratory volume in 1 second (RRMS, SPMS, PPMS, mean EDSS 4.5); this change is of unclear clinical significance. This technique possibly is ineffective for improving disability (1 Class II). Inspiratory muscle training (10 weeks) possibly improves maximal inspiratory pressure (RRMS, SPMS, PPMS, EDSS 2–6.5) (1 Class II). PMID:26598432

Recommended Experimental Procedures for Evaluation of Abrupt Wing Stall Characteristics

NASA Technical Reports Server (NTRS)

Capone, F. J.; Hall, R. M.; Owens, D. B.; Lamar, J. E.; McMillin, S. N.

2003-01-01

This paper presents a review of the experimental program under the Abrupt Wing Stall (AWS) Program. Candidate figures of merit from conventional static tunnel tests are summarized and correlated with data obtained in unique free-to-roll tests. Where possible, free-to-roll results are also correlated with flight data. Based on extensive studies of static experimental figures of merit in the Abrupt Wing Stall Program for four different aircraft configurations, no one specific figure of merit consistently flagged a warning of potential lateral activity when actual activity was seen to occur in the free-to-roll experiments. However, these studies pointed out the importance of measuring and recording the root mean square signals of the force balance.

Diminution of contact angle hysteresis under the influence of an oscillating force.

PubMed

Manor, Ofer

2014-06-17

We suggest a simple quantitative model for the diminution of contact angle hysteresis under the influence of an oscillatory force invoked by thermal fluctuations, substrate vibrations, acoustic waves, or oscillating electric fields. Employing force balance rather than the usual description of contact angle hysteresis in terms of Gibbs energy, we highlight that a wetting system, such as a sessile drop or a bubble adhered to a solid substrate, appears at long times to be partially or fully independent of contact angle hysteresis and thus independent of static friction forces, as a result of contact line pinning. We verify this theory by studying several well-known experimental observations such as the approach of an arbitrary contact angle toward the Young contact angle and the apparent decrease (or increase) in an advancing (or a receding) contact angle under the influence of an external oscillating force.

Quasi-Static Evolution, Catastrophe, and "Failed" Eruption of Solar Flux Ropes

NASA Astrophysics Data System (ADS)

Chen, James

2017-04-01

This paper presents the first unified theoretical model of solar flux rope dynamics—a single set of flux-rope equations in ideal MHD—to describe as one integrated process the quasi-static evolution, catastrophic transition to eruption, cessation ("failure") of eruption, and the post-eruption quasi-equilibria. The model is defined by the major radial and minor radial equations of motion including pressure. The initial equilibrium is a flux rope in a background plasma with pressure pc(Z) and an overlying magnetic field Bc(Z). The flux rope may be initially force-free, but the evolution is not required to be force-free. As the poloidal flux is slowly increased, the flux rope rises through a sequence of quasi-static equilibria. As the apex of the flux rope expands past a critical height Zcrt, it erupts on a dynamical (Alfvénic) timescale. Mathematically, the onset of eruption is shown to be explosive, not exponential. The acceleration is rapidly quenched due to the geometrical effects of the stationary footpoints, and a new equilibrium is established at height Z1 > Zcrt. The calculated velocity profile resembles the observed velocity profiles in "failed" eruptions including a damped oscillation. In the post-eruption equilibria, the outward hoop force is balanced by the tension of the toroidal self magnetic field and pressure gradient force. Thus, the flux rope does not evolve in a force-free manner. The flux rope may also expand without reaching a new equilibrium, provided a sufficient amount of poloidal flux is injected on the timescale of eruption. This scenario results in a full CME eruption. It is shown that the minor radial expansion critically couples the evolution of the toroidal self-field and pressure gradient force. No parameter regime is found in which the commonly used simplifications—near-equilibrium minor radial expansion, force-free expansion, and constant aspect ratio R/a (e.g., the torus instability equation)—are valid. Work supported by the Naval Research Laboratory Base Research Program

Instance Analysis for the Error of Three-pivot Pressure Transducer Static Balancing Method for Hydraulic Turbine Runner

NASA Astrophysics Data System (ADS)

Weng, Hanli; Li, Youping

2017-04-01

The working principle, process device and test procedure of runner static balancing test method by weighting with three-pivot pressure transducers are introduced in this paper. Based on an actual instance of a V hydraulic turbine runner, the error and sensitivity of the three-pivot pressure transducer static balancing method are analysed. Suggestions about improving the accuracy and the application of the method are also proposed.

Fan and wing force data from wind tunnel investigation of a 0.38 meter (15 inch) diameter VTOL model lift fan installed in a two dimensional wing

NASA Technical Reports Server (NTRS)

Yuska, J. A.; Diedrich, J. H.

1972-01-01

Test data are presented for a 38-cm (15-in.) diameter, 1.28 pressure ratio model VTOL lift fan installed in a two-dimensional wing and tested in a 2.74-by 4.58-meter (9-by 15-ft)V/STOL wind tunnel. Tests were run with and without exit louvers over a wide range of crossflow velocities and wing angle of attack. Tests were also performed with annular-inlet vanes, inlet bell-mouth surface disconuities, and fences to induce fan windmilling. Data are presented on the axial force of the fan assembly and overall wing forces and moments as measured on force balances for various static and crossflow test conditions. Midspan wing surface pressure coefficient data are also given.

Comparative Study of Two Systems for the Assessment of Static Balance in Veterans with Mild Traumatic Brain Injury.

PubMed

Leland, Azadeh; Tavakol, Kamran; Scholten, Joel; Bakhshi, Simin; Kelarestaghi, Kaveh

2018-04-01

Traditionally, the diagnosis of postural instability relies on the clinical examination of static balance. In recent years, computerized technologies have provided a new approach for the accurate detection of positional changes during functional balance. The aim of this study was to investigate the similarities and differences between two electronic systems, NeuroCom and BioSensics , and their application in the clinical assessment of impaired balance in American veterans. We examined the sway around the center of mass during static balance conditions in 25 veterans with mild traumatic brain injury, using the two electronic systems. These patients met the inclusion criteria and were assessed for their impaired balance at the District of Columbia Veterans Affair Medical Center, Washington, DC, USA. There were six static balance tests conducted on either NeuroCom or BioSensics system in triplicate. Of the data for 36 sets of statistical data analyses, there were significant correlations among those for eight data sets (22.2%) between the two systems. The strongest positive correlation between the data from the two systems was found during the baseline test, when inputs from visual, vestibular and sensorymotor sources were uninterrupted. The data from the remaining experimental conditions did not correlate significantly with one another. Both NeuroCom and BioSensics provided comparable data in eight out of 36 experimental conditions in the assessment of static balance in patients with mild traumatic brain injury. The findings clarified the ambiguities in the application of NeuroCom versus BioSensics, provided new knowledge for the field of physical medicine and rehabilitation, and improved the clinical assessment of static balance in patients with mTBI.

Static structure of chameleon dark matter as an explanation of dwarf spheroidal galaxy cores

NASA Astrophysics Data System (ADS)

Chanda, Prolay Krishna; Das, Subinoy

2017-04-01

We propose a novel mechanism that explains the cored dark matter density profile in recently observed dark matter rich dwarf spheroidal galaxies. In our scenario, dark matter particle mass decreases gradually as a function of distance towards the center of a dwarf galaxy due to its interaction with a chameleon scalar. At closer distance towards the Galactic center the strength of attractive scalar fifth force becomes much stronger than gravity and is balanced by the Fermi pressure of the dark matter cloud; thus, an equilibrium static configuration of the dark matter halo is obtained. Like the case of soliton star or fermion Q-star, the stability of the dark matter halo is obtained as the scalar achieves a static profile and reaches an asymptotic value away from the Galactic center. For simple scalar-dark matter interaction and quadratic scalar self-interaction potential, we show that dark matter behaves exactly like cold dark matter (CDM) beyond a few kpc away from the Galactic center but at closer distance it becomes lighter and Fermi pressure cannot be ignored anymore. Using Thomas-Fermi approximation, we numerically solve the radial static profile of the scalar field, fermion mass and dark matter energy density as a function of distance. We find that for fifth force mediated by an ultralight scalar, it is possible to obtain a flattened dark matter density profile towards the Galactic center. In our scenario, the fifth force can be neglected at distance r ≥1 kpc from the Galactic center and dark matter can be simply treated as heavy nonrelativistic particles beyond this distance, thus reproducing the success of CDM at large scales.

Contact angle hysteresis in a microchannel: statics

NASA Astrophysics Data System (ADS)

Hatipogullari, Metin; Wylock, Christophe; Pradas, Marc; Kalliadasis, Serafim; Colinet, Pierre

2017-11-01

We study contact angle hysteresis by tracking static meniscus configurations upon varying the volume of a liquid inside a chemically heterogeneous microchannel. We first construct a graphical force balance similar to the classical theory of Joanny and de Gennes for this system, though here with a straight contact line (2D channel). Hysteresis is induced by wettability gradients above a finite threshold value. This is also visualized in a phase plot enabling to easily predict stick-slip events of the contact line and the occurrence of hysteresis. Above the threshold and for non-overlapping Gaussian defects, we find good agreement with the classical formulas for the hysteresis amplitude induced by a dilute system of defects. In particular it is found to be proportional to the square of the defect force and to the defect concentration. For a sinusoidal heterogeneity, decreasing the ratio between the heterogeneity wavelength and the microchannel gap size, brings the system from a sub threshold regime, to a stick-slip dominated regime, and finally to a regime with a quasi-constant advancing and receding angle. In the latter, the hysteresis amplitude is found to be proportional to the defect force.

Relationship between antigravity control and postural control in young children.

PubMed

Sellers, J S

1988-04-01

The purposes of this study were 1) to determine the relationship between antigravity control (supine flexion and prone extension) and postural control (static and dynamic balance), 2) to determine the quality of antigravity and postural control, and 3) to determine whether sex and ethnic group differences correlate with differences in antigravity control and postural control in young children. I tested 107 black, Hispanic, and Caucasian children in a Head Start program, with a mean age of 61 months. The study results showed significant relationships between antigravity control and postural control. Subjects' supine flexion performance was significantly related to the quantity and quality of their static and dynamic balance performance, whereas prone extension performance was related only to the quality of dynamic balance performance. Quality scale measurements (r = .90) indicated that the children in this study had not yet developed full antigravity or postural control. The study results revealed differences between sexes in the quality of static balance and prone extension performance and ethnic differences in static balance, dynamic balance, and prone extension performance.

Trajectory Adjustments Underlying Task-Specific Intermittent Force Behaviors and Muscular Rhythms

PubMed Central

Chen, Yi-Ching; Lin, Yen-Ting; Huang, Chien-Ting; Shih, Chia-Li; Yang, Zong-Ru; Hwang, Ing-Shiou

2013-01-01

Force intermittency is one of the major causes of motor variability. Focusing on the dynamics of force intermittency, this study was undertaken to investigate how force trajectory is fine-tuned for static and dynamic force-tracking of a comparable physical load. Twenty-two healthy adults performed two unilateral resistance protocols (static force-tracking at 75% maximal effort and dynamic force-tracking in the range of 50%–100% maximal effort) using the left hand. The electromyographic activity and force profile of the designated hand were monitored. Gripping force was off-line decomposed into a primary movement spectrally identical to the target motion and a force intermittency profile containing numerous force pulses. The results showed that dynamic force-tracking exhibited greater intermittency amplitude and force pulse but a smaller amplitude ratio of primary movement to force intermittency than static force-tracking. Multi-scale entropy analysis revealed that force intermittency during dynamic force-tracking was more complex on a low time scale but more regular on a high time scale than that of static force-tracking. Together with task-dependent force intermittency properties, dynamic force-tracking exhibited a smaller 8–12 Hz muscular oscillation but a more potentiated muscular oscillation at 35–50 Hz than static force-tracking. In conclusion, force intermittency reflects differing trajectory controls for static and dynamic force-tracking. The target goal of dynamic tracking is achieved through trajectory adjustments that are more intricate and more frequent than those of static tracking, pertaining to differing organizations and functioning of muscular oscillations in the alpha and gamma bands. PMID:24098640

Postural control and low back pain in elite athletes comparison of static balance in elite athletes with and without low back pain.

PubMed

Oyarzo, Claudio A; Villagrán, Claudio R; Silvestre, Rony E; Carpintero, Pedro; Berral, Francisco J

2014-01-01

Although current research findings suggest that postural control or static balance is impaired in subjects with low back pain, few studies have specifically addressed the effect of low back pain on static balance in elite athletes. Forty-four athletes belonging to Chilean national teams took part in this study; 20 had low back pain and the remaining 24 were healthy controls. Displacement of the centre of pressure was analyzed by computerized platform posturography, using a standardized protocol; subjects were required to stand upright on both feet, with eyes first open then closed. The results showed that, athletes with low back pain used significantly more energy (p< 0.0182) and had a greater displacement of the centre of pressure (p< 0.005) with open eyes to control posture than healthy athletes. It may be concluded that static balance is impaired in elite athletes with low back pain and that analysis of two-footed stance provides a sensitive assessment of static balance in athletes.

The Effect of Obstacle Training in Water on Static Balance of Chronic Stroke Patients

PubMed Central

Jung, JaeHyun; Lee, JiYeun; Chung, EunJung; Kim, Kyoung

2014-01-01

[Purpose] This study evaluated the effects of water and land-based obstacle training on static balance of chronic stroke patients. [Subjects] The subjects were randomly allocated to an aqua group (n=15) and a land group (n=15). [Methods] Both groups trained for 40 minutes, 3 times a week for 12 weeks. Static balance was assessed by measuring the mean velocities of mediolateral (ML) and anteroposterior (AP), and sway area with the eyes closed. [Results] Following the intervention, both groups showed significant changes in ML velocity, AP velocity, and sway area. The static balance of the aqua group was significantly better than the land group. [Conclusion] The results of this study suggest the feasibility and suitability of obstacle training in water for stroke patients. PMID:24707102

Analysis of the wind tunnel test of a tilt rotor power force model

NASA Technical Reports Server (NTRS)

Marr, R. L.; Ford, D. G.; Ferguson, S. W.

1974-01-01

Two series of wind tunnel tests were made to determine performance, stability and control, and rotor wake interaction on the airframe, using a one-tenth scale powered force model of a tilt rotor aircraft. Testing covered hover (IGE/OCE), helicopter, conversion, and airplane flight configurations. Forces and moments were recorded for the model from predetermined trim attitudes. Control positions were adjusted to trim flight (one-g lift, pitching moment and drag zero) within the uncorrected test data balance accuracy. Pitch and yaw sweeps were made about the trim attitudes with the control held at the trimmed settings to determine the static stability characteristics. Tail on, tail off, rotors on, and rotors off configurations were testes to determine the rotor wake effects on the empennage. Results are presented and discussed.

An Investigation of the Static Force Balance of a Model Railgun

DTIC Science & Technology

2007-06-01

this simple circuit diagram two 950 CCA batteries are passed through a variable resistor (R1) to limit the current applied to the model railgun (R2...of a known value and placed a voltmeter across the resistor . For additional protection in these early trials we inserted an equivalent 1kA fuse...our variable resistor . Current then passed through the resistor into the model gun, through a volt-meter with a known resistance, into a kilo-amp

The Effects of Comprehensive Warm-Up Programs on Proprioception, Static and Dynamic Balance on Male Soccer Players

PubMed Central

Daneshjoo, Abdolhamid; Mokhtar, Abdul Halim; Rahnama, Nader; Yusof, Ashril

2012-01-01

Purpose The study investigated the effects of FIFA 11+ and HarmoKnee, both being popular warm-up programs, on proprioception, and on the static and dynamic balance of professional male soccer players. Methods Under 21 year-old soccer players (n = 36) were divided randomly into 11+, HarmoKnee and control groups. The programs were performed for 2 months (24 sessions). Proprioception was measured bilaterally at 30°, 45° and 60° knee flexion using the Biodex Isokinetic Dynamometer. Static and dynamic balances were evaluated using the stork stand test and Star Excursion Balance Test (SEBT), respectively. Results The proprioception error of dominant leg significantly decreased from pre- to post-test by 2.8% and 1.7% in the 11+ group at 45° and 60° knee flexion, compared to 3% and 2.1% in the HarmoKnee group. The largest joint positioning error was in the non-dominant leg at 30° knee flexion (mean error value = 5.047), (p<0.05). The static balance with the eyes opened increased in the 11+ by 10.9% and in the HarmoKnee by 6.1% (p<0.05). The static balance with eyes closed significantly increased in the 11+ by 12.4% and in the HarmoKnee by 17.6%. The results indicated that static balance was significantly higher in eyes opened compared to eyes closed (p = 0.000). Significant improvements in SEBT in the 11+ (12.4%) and HarmoKnee (17.6%) groups were also found. Conclusion Both the 11+ and HarmoKnee programs were proven to be useful warm-up protocols in improving proprioception at 45° and 60° knee flexion as well as static and dynamic balance in professional male soccer players. Data from this research may be helpful in encouraging coaches or trainers to implement the two warm-up programs in their soccer teams. PMID:23251579

Neuroimaging of Human Balance Control: A Systematic Review

PubMed Central

Wittenberg, Ellen; Thompson, Jessica; Nam, Chang S.; Franz, Jason R.

2017-01-01

This review examined 83 articles using neuroimaging modalities to investigate the neural correlates underlying static and dynamic human balance control, with aims to support future mobile neuroimaging research in the balance control domain. Furthermore, this review analyzed the mobility of the neuroimaging hardware and research paradigms as well as the analytical methodology to identify and remove movement artifact in the acquired brain signal. We found that the majority of static balance control tasks utilized mechanical perturbations to invoke feet-in-place responses (27 out of 38 studies), while cognitive dual-task conditions were commonly used to challenge balance in dynamic balance control tasks (20 out of 32 studies). While frequency analysis and event related potential characteristics supported enhanced brain activation during static balance control, that in dynamic balance control studies was supported by spatial and frequency analysis. Twenty-three of the 50 studies utilizing EEG utilized independent component analysis to remove movement artifacts from the acquired brain signals. Lastly, only eight studies used truly mobile neuroimaging hardware systems. This review provides evidence to support an increase in brain activation in balance control tasks, regardless of mechanical, cognitive, or sensory challenges. Furthermore, the current body of literature demonstrates the use of advanced signal processing methodologies to analyze brain activity during movement. However, the static nature of neuroimaging hardware and conventional balance control paradigms prevent full mobility and limit our knowledge of neural mechanisms underlying balance control. PMID:28443007

Development of the NTF-117S Semi-Span Balance

NASA Technical Reports Server (NTRS)

Lynn, Keith C.

2010-01-01

A new high-capacity semi-span force and moment balance has recently been developed for use at the National Transonic Facility at the NASA Langley Research Center. This new semi-span balance provides the NTF a new measurement capability that will support testing of semi-span test models at transonic high-lift testing regimes. Future testing utilizing this new balance capability will include active circulation control and propulsion simulation testing of semi-span transonic wing models. The NTF has recently implemented a new highpressure air delivery station that will provide both high and low mass flow pressure lines that are routed out to the semi-span models via a set high/low pressure bellows that are indirectly linked to the metric end of the NTF-117S balance. A new check-load stand is currently being developed to provide the NTF with an in-house capability that will allow for performing check-loads on the NTF-117S balance in order to determine the pressure tare affects on the overall performance of the balance. An experimental design is being developed that will allow for experimentally assessing the static pressure tare affects on the balance performance.

Summary of comprehensive systematic review: Rehabilitation in multiple sclerosis: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology.

PubMed

Haselkorn, Jodie K; Hughes, Christina; Rae-Grant, Alex; Henson, Lily Jung; Bever, Christopher T; Lo, Albert C; Brown, Theodore R; Kraft, George H; Getchius, Thomas; Gronseth, Gary; Armstrong, Melissa J; Narayanaswami, Pushpa

2015-11-24

To systematically review the evidence regarding rehabilitation treatments in multiple sclerosis (MS). We systematically searched the literature (1970-2013) and classified articles using 2004 American Academy of Neurology criteria. This systematic review highlights the paucity of well-designed studies, which are needed to evaluate the available MS rehabilitative therapies. Weekly home/outpatient physical therapy (8 weeks) probably is effective for improving balance, disability, and gait (MS type unspecified, participants able to walk ≥5 meters) but probably is ineffective for improving upper extremity dexterity (1 Class I). Inpatient exercises (3 weeks) followed by home exercises (15 weeks) possibly are effective for improving disability (relapsing-remitting MS [RRMS], primary progressive MS [PPMS], secondary progressive MS [SPMS], Expanded Disability Status Scale [EDSS] 3.0-6.5) (1 Class II). Six weeks' worth of comprehensive multidisciplinary outpatient rehabilitation possibly is effective for improving disability/function (PPMS, SPMS, EDSS 4.0-8.0) (1 Class II). Motor and sensory balance training or motor balance training (3 weeks) possibly is effective for improving static and dynamic balance, and motor balance training (3 weeks) possibly is effective for improving static balance (RRMS, SPMS, PPMS) (1 Class II). Breathing-enhanced upper extremity exercises (6 weeks) possibly are effective for improving timed gait and forced expiratory volume in 1 second (RRMS, SPMS, PPMS, mean EDSS 4.5); this change is of unclear clinical significance. This technique possibly is ineffective for improving disability (1 Class II). Inspiratory muscle training (10 weeks) possibly improves maximal inspiratory pressure (RRMS, SPMS, PPMS, EDSS 2-6.5) (1 Class II). © 2015 American Academy of Neurology.

[The modern approaches to the restoration of postural balance in the patients suffering from the consequences of an acute cerebrovascular accident (CVA)].

PubMed

Volovets, S A; Sergeenko, E Y; Darinskaya, L Y; Polyaev, B A; Yashinina, Y A; Isaeva, M A; Zhitareva, I V; Lobov, A N; Panova, T I

2018-05-21

the most frequent and severe consequences of an acute cerebrovascular accident (CVA) are locomotor and coordination disorders which significantly increase the risk of falling in a static position and when walking. The methods used for the rehabilitation of the affected patients are designed in the first place to enable the patients to acquire the skills necessary for maintaining the static balance. The modern equipment allows to carry out coordination training in the static position and also during walking. The objective of the present study was to evaluate, based on the results of our original research, the feasibility and effectiveness of the application of the «Balance tutor» system developed for the restoration of static and dynamic balance in the framework of the combined rehabilitation treatment of the patients suffering from impaired postural balance as a consequence of acute cerebrovascular accident (CVA). A total of 56 patients presenting with impaired postural balance following CVA were available for the examination. All of them underwent functional testing to assess the static and dynamic balance, walking abilities, and the risk of falling down including the study with the use of computer-assisted stabilometry. The study has demonstrated that the inclusion of the «Balance tutor» system for the restoration of the static and dynamic balance in the combined rehabilitative treatment of the patients having postural balance disorders after the CVA reduces the risk of fall for a walking patient, improves his (her) static and dynamic balance, increases the patient's ability to move without exterior help. The patients comprising the main study group were found to experience a decrease of statokinesiogram space in the «eyes are open» position (p = 0.0576, the Mann-Whitney U test) as well as a reliable decrease of the statokinesiogram space in the «eyes are closed» position (p=0.0063, the Mann-Whitney U test). Similar changes occurred in speed of pressure center relocation. By the end of the rehabilitation course, the patients of the main group exhibited a reliable enhancement in the dynamic balance rates estimated with the use of the Berg Balance Scale (p=0.028, Tukey's criterion), an increase in stability based at the Tinneti scale, p=0.0291; Tukey's criterion), and a decrease of the risk of falling during walk assessed with the application of Dynamic Gait Index scale (p = 0.0001, Tukey's criterion). The results of the present study with the inclusion of the «Balance tutor» system in the program of combined rehabilitation of the patients suffering from the consequences of CVA in the form of the postural balance impairment give evidence of the feasibility and effectiveness of this approach. There is reason to believe that its application is likely to reduce the risk of falling down and to improve characteristics of static and dynamic balance. The inclusion of the «Balance tutor» system in the program of combined rehabilitation of the patients suffering from the consequences of CVA in the form of the postural balance impairment is both feasible and effective.

A Theoretical Investigation of Longitudinal Stability of Airplanes with Free Controls Including Effect of Friction in Control System

NASA Technical Reports Server (NTRS)

Greenberg, Harry; Sternfield, Leonard

1944-01-01

The relation between the elevator hinge moment parameters and the control forces for changes in forward speed and in maneuvers is shown for several values of static stability and elevator mass balance. The stability of the short period oscillations is shown as a series of boundaries giving the limits of the stable regions in terms of the elevator hinge moment parameters. The effects of static stability, elevator moment of inertia, elevator mass unbalance, and airplane density are also considered. Dynamic instability is likely to occur if there is mass unbalance of the elevator control system combined with a small restoring tendency (high aerodynamic balance). This instability can be prevented by a rearrangement of the unbalancing weights which, however, involves an increase of the amount of weight necessary. It can also be prevented by the addition of viscous friction to the elevator control system provided the airplane center of gravity is not behind a certain critical position. For high values of the density parameter, which correspond to high altitudes of flight, the addition of moderate amounts of viscous friction may be destabilizing even when the airplane is statically stable. In this case, increasing the viscous friction makes the oscillation stable again. The condition in which viscous friction causes dynamic instability of a statically stable airplane is limited to a definite range of hinge moment parameters. It is shown that, when viscous friction causes increasing oscillations, solid friction will produce steady oscillations having an amplitude proportional to the amount of friction.

Development of a commercially viable piezoelectric force sensor system for static force measurement

NASA Astrophysics Data System (ADS)

Liu, Jun; Luo, Xinwei; Liu, Jingcheng; Li, Min; Qin, Lan

2017-09-01

A compensation method for measuring static force with a commercial piezoelectric force sensor is proposed to disprove the theory that piezoelectric sensors and generators can only operate under dynamic force. After studying the model of the piezoelectric force sensor measurement system, the principle of static force measurement using a piezoelectric material or piezoelectric force sensor is analyzed. Then, the distribution law of the decay time constant of the measurement system and the variation law of the measurement system’s output are studied, and a compensation method based on the time interval threshold Δ t and attenuation threshold Δ {{u}th} is proposed. By calibrating the system and considering the influences of the environment and the hardware, a suitable Δ {{u}th} value is determined, and the system’s output attenuation is compensated based on the Δ {{u}th} value to realize the measurement. Finally, a static force measurement system with a piezoelectric force sensor is developed based on the compensation method. The experimental results confirm the successful development of a simple compensation method for static force measurement with a commercial piezoelectric force sensor. In addition, it is established that, contrary to the current perception, a piezoelectric force sensor system can be used to measure static force through further calibration.

Influence of visual inputs on quasi-static standing postural steadiness in individuals with spinal cord injury.

PubMed

Lemay, Jean-François; Gagnon, Dany; Duclos, Cyril; Grangeon, Murielle; Gauthier, Cindy; Nadeau, Sylvie

2013-06-01

Postural steadiness while standing is impaired in individuals with spinal cord injury (SCI) and could be potentially associated with increased reliance on visual inputs. The purpose of this study was to compare individuals with SCI and able-bodied participants on their use of visual inputs to maintain standing postural steadiness. Another aim was to quantify the association between visual contribution to achieve postural steadiness and a clinical balance scale. Individuals with SCI (n = 15) and able-bodied controls (n = 14) performed quasi-static stance, with eyes open or closed, on force plates for two 45 s trials. Measurements of the centre of pressure (COP) included the mean value of the root mean square (RMS), mean COP velocity (MV) and COP sway area (SA). Individuals with SCI were also evaluated with the Mini-Balance Evaluation Systems Test (Mini BESTest), a clinical outcome measure of postural steadiness. Individuals with SCI were significantly less stable than able-bodied controls in both conditions. The Romberg ratios (eyes open/eyes closed) for COP MV and SA were significantly higher for individuals with SCI, indicating a higher contribution of visual inputs for postural steadiness in that population. Romberg ratios for RMS and SA were significantly associated with the Mini-BESTest. This study highlights the contribution of visual inputs in individuals with SCI when maintaining quasi-static standing posture. Copyright © 2012 Elsevier B.V. All rights reserved.

Tactical STOL moment balance through innovative configuration technology

NASA Technical Reports Server (NTRS)

Eckard, G. J.; Sutton, R. C.; Poth, G. E.

1981-01-01

Innovative and conventional thrust vectoring moment balance mechanisms, as applied to advanced tactical fighters, are examined. The innovative mechanisms include thrust line translation, life line translation, and auxiliary power control; the conventional mechanisms under investigation are horizontal tails, canards, and variable sweep wings. These mechanisms are tested for their ability to provide negative static margins for landing approach or relocation of the vectored thrust line nearer the aircraft's center of gravity. The net pitching moment due to wing, flaps, and vectored thrust lift would then be small, making possible beneficial trim forces from small trimming devices. These innovative mechanisms are, however, possibly heavy and must be evaluated on their complexity, reliability, maintainability, and STOL capabilities. Several candidate fighter configurations are compared and evaluated.

Effects of virtual reality programs on balance in functional ankle instability

PubMed Central

Kim, Ki-Jong; Heo, Myoung

2015-01-01

[Purpose] The aim of present study was to identify the impact that recent virtual reality training programs used in a variety of fields have had on the ankle’s static and dynamic senses of balance among subjects with functional ankle instability. [Subjects and Methods] This study randomly divided research subjects into two groups, a strengthening exercise group (Group I) and a balance exercise group (Group II), with each group consisting of 10 people. A virtual reality program was performed three times a week for four weeks. Exercises from the Nintendo Wii Fit Plus program were applied to each group for twenty minutes along with ten minutes of warming up and wrap-up exercises. [Results] Group II showed a significant decrease of post-intervention static and dynamic balance overall in the anterior-posterior, and mediolateral directions, compared with the pre-intervention test results. In comparison of post-intervention static and dynamic balance between Group I and Group II, a significant decrease was observed overall. [Conclusion] Virtual reality programs improved the static balance and dynamic balance of subjects with functional ankle instability. Virtual reality programs can be used more safely and efficiently if they are implemented under appropriate monitoring by a physiotherapist. PMID:26644652

Effects of virtual reality programs on balance in functional ankle instability.

PubMed

Kim, Ki-Jong; Heo, Myoung

2015-10-01

[Purpose] The aim of present study was to identify the impact that recent virtual reality training programs used in a variety of fields have had on the ankle's static and dynamic senses of balance among subjects with functional ankle instability. [Subjects and Methods] This study randomly divided research subjects into two groups, a strengthening exercise group (Group I) and a balance exercise group (Group II), with each group consisting of 10 people. A virtual reality program was performed three times a week for four weeks. Exercises from the Nintendo Wii Fit Plus program were applied to each group for twenty minutes along with ten minutes of warming up and wrap-up exercises. [Results] Group II showed a significant decrease of post-intervention static and dynamic balance overall in the anterior-posterior, and mediolateral directions, compared with the pre-intervention test results. In comparison of post-intervention static and dynamic balance between Group I and Group II, a significant decrease was observed overall. [Conclusion] Virtual reality programs improved the static balance and dynamic balance of subjects with functional ankle instability. Virtual reality programs can be used more safely and efficiently if they are implemented under appropriate monitoring by a physiotherapist.

Effects on Hamstring Muscle Extensibility, Muscle Activity, and Balance of Different Stretching Techniques

PubMed Central

Lim, Kyoung-Il; Nam, Hyung-Chun; Jung, Kyoung-Sim

2014-01-01

[Purpose] The purpose of this study was to investigate the effects of two different stretching techniques on range of motion (ROM), muscle activation, and balance. [Subjects] For the present study, 48 adults with hamstring muscle tightness were recruited and randomly divided into three groups: a static stretching group (n=16), a PNF stretching group (n=16), a control group (n=16). [Methods] Both of the stretching techniques were applied to the hamstring once. Active knee extension angle, muscle activation during maximum voluntary isometric contraction (MVC), and static balance were measured before and after the application of each stretching technique. [Results] Both the static stretching and the PNF stretching groups showed significant increases in knee extension angle compared to the control group. However, there were no significant differences in muscle activation or balance between the groups. [Conclusion] Static stretching and PNF stretching techniques improved ROM without decrease in muscle activation, but neither of them exerted statistically significant effects on balance. PMID:24648633

Effects of a Nintendo Wii exercise program on spasticity and static standing balance in spastic cerebral palsy.

PubMed

Gatica-Rojas, Valeska; Cartes-Velásquez, Ricardo; Méndez-Rebolledo, Guillermo; Guzman-Muñoz, Eduardo; Lizama, L Eduardo Cofré

2017-08-01

This study sought to evaluate the effects of a Nintendo Wii Balance Board (NWBB) intervention on ankle spasticity and static standing balance in young people with spastic cerebral palsy (SCP). Ten children and adolescents (aged 72-204 months) with SCP participated in an exercise program with NWBB. The intervention lasted 6 weeks, 3 sessions per week, 25 minutes for each session. Ankle spasticity was assessed using the Modified Modified Ashworth Scale (MMAS), and static standing balance was quantified using posturographic measures (center-of-pressure [CoP] measures). Pre- and post-intervention measures were compared. Significant decreases of spasticity in the ankle plantar flexor muscles (p < 0.01). There was also a significant reduction in the CoP sway area (p = 0.04), CoP mediolateral velocity (p =0.03), and CoP anterior-posterior velocity (p = 0.03). A 6-session NWBB program reduces the spasticity at the ankle plantar flexors and improves the static standing balance in young people with SCP.

The PARAChute Project: Remote Monitoring of Posture and Gait for Fall Prevention

NASA Astrophysics Data System (ADS)

Hewson, David J.; Duchêne, Jacques; Charpillet, François; Saboune, Jamal; Michel-Pellegrino, Valérie; Amoud, Hassan; Doussot, Michel; Paysant, Jean; Boyer, Anne; Hogrel, Jean-Yves

2007-12-01

Falls in the elderly are a major public health problem due to both their frequency and their medical and social consequences. In France alone, more than two million people aged over 65 years old fall each year, leading to more than 9 000 deaths, in particular in those over 75 years old (more than 8 000 deaths). This paper describes the PARAChute project, which aims to develop a methodology that will enable the detection of an increased risk of falling in community-dwelling elderly. The methods used for a remote noninvasive assessment for static and dynamic balance assessments and gait analysis are described. The final result of the project has been the development of an algorithm for movement detection during gait and a balance signature extracted from a force plate. A multicentre longitudinal evaluation of balance has commenced in order to validate the methodologies and technologies developed in the project.

Assessment of magnetic field interactions and radiofrequency‐radiation‐induced heating of metallic spinal implants in 7 T field

PubMed Central

Tsukimura, Itsuko; Sasaki, Makoto; Endo, Hirooki; Yamabe, Daisuke; Oikawa, Ryosuke; Doita, Minoru

2017-01-01

ABSTRACT The safety of metallic spinal implants in magnetic resonance imaging (MRI) performed using ultrahigh fields has not been established. Hence, we examined whether the displacement forces caused by a static magnetic field and the heating induced by radiofrequency radiation are substantial for spinal implants in a 7 T field. We investigated spinal rods of various lengths and materials, a screw, and a cross‐linking bridge in accordance with the American Society for Testing and Materials guidelines. The displacement forces of the metallic implants in static 7 T and 3 T static magnetic fields were measured and compared. The temperature changes of the implants during 15‐min‐long fast spin‐echo and balanced gradient‐echo image acquisition sequences were measured in the 7 T field. The deflection angles of the metallic spinal materials in the 7 T field were 5.0–21.0° [median: 6.7°], significantly larger than those in the 3 T field (1.0–6.3° [2.2°]). Among the metallic rods, the cobalt–chrome rods had significantly larger deflection angles (17.8–21.0° [19.8°]) than the pure titanium and titanium alloy rods (5.0–7.7° [6.2°]). The temperature changes of the implants, including the cross‐linked rods, were 0.7–1.0°C [0.8°C] and 0.6–1.0°C [0.7°C] during the fast spin‐echo and balanced gradient‐echo sequences, respectively; these changes were slightly larger than those of the controls (0.4–1.1°C [0.5°C] and 0.3–0.9°C [0.6°C], respectively). All of the metallic spinal implants exhibited small displacement forces and minimal heating, indicating that MRI examinations using 7 T fields may be performed safely on patients with these implants. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:1831–1837, 2017. PMID:27769107

Assessment of magnetic field interactions and radiofrequency-radiation-induced heating of metallic spinal implants in 7 T field.

PubMed

Tsukimura, Itsuko; Murakami, Hideki; Sasaki, Makoto; Endo, Hirooki; Yamabe, Daisuke; Oikawa, Ryosuke; Doita, Minoru

2017-08-01

The safety of metallic spinal implants in magnetic resonance imaging (MRI) performed using ultrahigh fields has not been established. Hence, we examined whether the displacement forces caused by a static magnetic field and the heating induced by radiofrequency radiation are substantial for spinal implants in a 7 T field. We investigated spinal rods of various lengths and materials, a screw, and a cross-linking bridge in accordance with the American Society for Testing and Materials guidelines. The displacement forces of the metallic implants in static 7 T and 3 T static magnetic fields were measured and compared. The temperature changes of the implants during 15-min-long fast spin-echo and balanced gradient-echo image acquisition sequences were measured in the 7 T field. The deflection angles of the metallic spinal materials in the 7 T field were 5.0-21.0° [median: 6.7°], significantly larger than those in the 3 T field (1.0-6.3° [2.2°]). Among the metallic rods, the cobalt-chrome rods had significantly larger deflection angles (17.8-21.0° [19.8°]) than the pure titanium and titanium alloy rods (5.0-7.7° [6.2°]). The temperature changes of the implants, including the cross-linked rods, were 0.7-1.0°C [0.8°C] and 0.6-1.0°C [0.7°C] during the fast spin-echo and balanced gradient-echo sequences, respectively; these changes were slightly larger than those of the controls (0.4-1.1°C [0.5°C] and 0.3-0.9°C [0.6°C], respectively). All of the metallic spinal implants exhibited small displacement forces and minimal heating, indicating that MRI examinations using 7 T fields may be performed safely on patients with these implants. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:1831-1837, 2017. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society.

Kung-fu versus swimming training and the effects on balance abilities in young adolescents.

PubMed

Baccouch, Rym; Rebai, Haithem; Sahli, Sonia

2015-11-01

Our purpose is to investigate the static balance control of young adolescents practicing kung-fu and swimming in order to find out which of these physical activities is the most effective in developing specific balance abilities in young adolescents. Comparative experimental study. University laboratory research. Three groups of 11-13-year-old boys (12 practicing Kung-Fu, 12 practicing swimming and 12 controls). Center of pressure (CoP) excursions were registered in upright bipedal and unipedal stances on a stabilometric force platform in eyes open (EO) and eyes closed (EC) conditions. Kung-fu practitioners control their balance (P < .05) better than controls and swimmers in the unipedal posture when visual inputs are available. Kung-fu training improved (P < .05) the bipedal balance control in the EO condition. However, swimming training developed (P < .05) bipedal balance control in both EO and EC conditions. The swimmers showed a lower reliance on vision (P < .05) compared to kung-fu practitioners. Both of these physical activities could be recommended for young adolescents as recreational or rehabilitation programs as they develop specific balance abilities that could be important for improving and maintaining optimal health. Copyright © 2015 Elsevier Ltd. All rights reserved.

Dynamics of droplet motion under electrowetting actuation.

PubMed

Annapragada, S Ravi; Dash, Susmita; Garimella, Suresh V; Murthy, Jayathi Y

2011-07-05

The static shape of droplets under electrowetting actuation is well understood. The steady-state shape of the droplet is obtained on the basis of the balance of surface tension and electrowetting forces, and the change in the apparent contact angle is well characterized by the Young-Lippmann equation. However, the transient droplet shape behavior when a voltage is suddenly applied across a droplet has received less attention. Additional dynamic frictional forces are at play during this transient process. We present a model to predict this transient behavior of the droplet shape under electrowetting actuation. The droplet shape is modeled using the volume of fluid method. The electrowetting and dynamic frictional forces are included as an effective dynamic contact angle through a force balance at the contact line. The model is used to predict the transient behavior of water droplets on smooth hydrophobic surfaces under electrowetting actuation. The predictions of the transient behavior of droplet shape and contact radius are in excellent agreement with our experimental measurements. The internal fluid motion is explained, and the droplet motion is shown to initiate from the contact line. An approximate mathematical model is also developed to understand the physics of the droplet motion and to describe the overall droplet motion and the contact line velocities. © 2011 American Chemical Society

Vibration control in statically indeterminate adaptive truss structures

NASA Technical Reports Server (NTRS)

Baycan, C. M.; Utku, Senol; Wada, Ben K.

1993-01-01

In this work vibration control of statically indeterminate adaptive truss structures is investigated. Here, the actuators (i.e., length adjusting devices) that are used for vibration control, work against the axial forces caused by the inertial forces. In statically determinate adaptive trusses no axial force is induced by the actuation. The control problem in statically indeterminate trusses may be dominated by the actuation-induced axial element forces. The creation of actuation-induced axial forces puts the system to a higher energy state, thus aggravates the controls. It is shown that by the usage of sufficient number of slave actuators in addition to the actual control actuators, the actuation-induced axial element forces can be nullified, and the control problem of the statically indeterminate adaptive truss problem is reduced to that of a statically determinate one. It is also shown that the usage of slave actuators saves a great amount of control energy and provides robustness for the controls.

Rotary Balance Wind Tunnel Testing for the FASER Flight Research Aircraft

NASA Technical Reports Server (NTRS)

Denham, Casey; Owens, D. Bruce

2016-01-01

Flight dynamics research was conducted to collect and analyze rotary balance wind tunnel test data in order to improve the aerodynamic simulation and modeling of a low-cost small unmanned aircraft called FASER (Free-flying Aircraft for Sub-scale Experimental Research). The impetus for using FASER was to provide risk and cost reduction for flight testing of more expensive aircraft and assist in the improvement of wind tunnel and flight test techniques, and control laws. The FASER research aircraft has the benefit of allowing wind tunnel and flight tests to be conducted on the same model, improving correlation between wind tunnel, flight, and simulation data. Prior wind tunnel tests include a static force and moment test, including power effects, and a roll and yaw damping forced oscillation test. Rotary balance testing allows for the calculation of aircraft rotary derivatives and the prediction of steady-state spins. The rotary balance wind tunnel test was conducted in the NASA Langley Research Center (LaRC) 20-Foot Vertical Spin Tunnel (VST). Rotary balance testing includes runs for a set of given angular rotation rates at a range of angles of attack and sideslip angles in order to fully characterize the aircraft rotary dynamics. Tests were performed at angles of attack from 0 to 50 degrees, sideslip angles of -5 to 10 degrees, and non-dimensional spin rates from -0.5 to 0.5. The effects of pro-spin elevator and rudder deflection and pro- and anti-spin elevator, rudder, and aileron deflection were examined. The data are presented to illustrate the functional dependence of the forces and moments on angle of attack, sideslip angle, and angular rate for the rotary contributions to the forces and moments. Further investigation is necessary to fully characterize the control effectors. The data were also used with a steady state spin prediction tool that did not predict an equilibrium spin mode.

Development of a clinical static and dynamic standing balance measurement tool appropriate for use in adolescents.

PubMed

Emery, Carolyn A; Cassidy, J David; Klassen, Terry P; Rosychuk, Rhonda J; Rowe, Brian B

2005-06-01

There is a need in sports medicine for a static and dynamic standing balance measure to quantify balance ability in adolescents. The purposes of this study were to determine the test-retest reliability of timed static (eyes open) and dynamic (eyes open and eyes closed) unipedal balance measurements and to examine factors associated with balance. Adolescents (n=123) were randomly selected from 10 Calgary high schools. This study used a repeated-measures design. One rater measured unipedal standing balance, including timed eyes-closed static (ECS), eyes-open dynamic (EOD), and eyes-closed dynamic (ECD) balance at baseline and 1 week later. Dynamic balance was measured on a foam surface. Reliability was examined using both intraclass correlation coefficients (ICCs) and Bland and Altman statistical techniques. Multiple linear regressions were used to examine other potentially influencing factors. Based on ICCs, test-retest reliability was adequate for ECS, EOD, and ECD balance (ICC=.69, .59, and .46, respectively). The results of Bland and Altman methods, however, suggest that caution is required in interpreting reliability based on ICCs alone. Although both ECS balance and ECD balance appear to demonstrate adequate test-retest reliability by ICC, Bland and Altman methods of agreement demonstrate sufficient reliability for ECD balance only. Thirty percent of the subjects reached the 180-second maximum on EOD balance, suggesting that this test is not appropriate for use in this population. Balance ability (ECS and ECD) was better in adolescents with no past history of lower-extremity injury. Timed ECD balance is an appropriate and reliable clinical measurement for use in adolescents and is influenced by previous injury.

Variations in Static Force Control and Motor Unit Behavior with Error Amplification Feedback in the Elderly.

PubMed

Chen, Yi-Ching; Lin, Linda L; Lin, Yen-Ting; Hu, Chia-Ling; Hwang, Ing-Shiou

2017-01-01

Error amplification (EA) feedback is a promising approach to advance visuomotor skill. As error detection and visuomotor processing at short time scales decline with age, this study examined whether older adults could benefit from EA feedback that included higher-frequency information to guide a force-tracking task. Fourteen young and 14 older adults performed low-level static isometric force-tracking with visual guidance of typical visual feedback and EA feedback containing augmented high-frequency errors. Stabilogram diffusion analysis was used to characterize force fluctuation dynamics. Also, the discharge behaviors of motor units and pooled motor unit coherence were assessed following the decomposition of multi-channel surface electromyography (EMG). EA produced different behavioral and neurophysiological impacts on young and older adults. Older adults exhibited inferior task accuracy with EA feedback than with typical visual feedback, but not young adults. Although stabilogram diffusion analysis revealed that EA led to a significant decrease in critical time points for both groups, EA potentiated the critical point of force fluctuations [Formula: see text], short-term effective diffusion coefficients (Ds), and short-term exponent scaling only for the older adults. Moreover, in older adults, EA added to the size of discharge variability of motor units and discharge regularity of cumulative discharge rate, but suppressed the pooled motor unit coherence in the 13-35 Hz band. Virtual EA alters the strategic balance between open-loop and closed-loop controls for force-tracking. Contrary to expectations, the prevailing use of closed-loop control with EA that contained high-frequency error information enhanced the motor unit discharge variability and undermined the force steadiness in the older group, concerning declines in physiological complexity in the neurobehavioral system and the common drive to the motoneuronal pool against force destabilization.

Variations in Static Force Control and Motor Unit Behavior with Error Amplification Feedback in the Elderly

PubMed Central

Chen, Yi-Ching; Lin, Linda L.; Lin, Yen-Ting; Hu, Chia-Ling; Hwang, Ing-Shiou

2017-01-01

Error amplification (EA) feedback is a promising approach to advance visuomotor skill. As error detection and visuomotor processing at short time scales decline with age, this study examined whether older adults could benefit from EA feedback that included higher-frequency information to guide a force-tracking task. Fourteen young and 14 older adults performed low-level static isometric force-tracking with visual guidance of typical visual feedback and EA feedback containing augmented high-frequency errors. Stabilogram diffusion analysis was used to characterize force fluctuation dynamics. Also, the discharge behaviors of motor units and pooled motor unit coherence were assessed following the decomposition of multi-channel surface electromyography (EMG). EA produced different behavioral and neurophysiological impacts on young and older adults. Older adults exhibited inferior task accuracy with EA feedback than with typical visual feedback, but not young adults. Although stabilogram diffusion analysis revealed that EA led to a significant decrease in critical time points for both groups, EA potentiated the critical point of force fluctuations <ΔFc2>, short-term effective diffusion coefficients (Ds), and short-term exponent scaling only for the older adults. Moreover, in older adults, EA added to the size of discharge variability of motor units and discharge regularity of cumulative discharge rate, but suppressed the pooled motor unit coherence in the 13–35 Hz band. Virtual EA alters the strategic balance between open-loop and closed-loop controls for force-tracking. Contrary to expectations, the prevailing use of closed-loop control with EA that contained high-frequency error information enhanced the motor unit discharge variability and undermined the force steadiness in the older group, concerning declines in physiological complexity in the neurobehavioral system and the common drive to the motoneuronal pool against force destabilization. PMID:29167637

Short-term climatic fluctuations forced by thermal anomalies

NASA Technical Reports Server (NTRS)

Hanna, A. F.

1982-01-01

A two level, global, spectral model using pressure as a vertical coordinate was developed. The system of equations describing the model is nonlinear and quasi-geostrophic (linear balance). Static stability is variable in the model. A moisture budget is calculated in the lower layer only. Convective adjustment is used to avoid supercritical temperature lapse rates. The mechanical forcing of topography is introduced as a vertical velocity at the lower boundary. Solar forcing is specified assuming a daily mean zenith angle. The differential diabatic heating between land and sea is paramterized. On land and sea ice surfaces, a steady state thermal energy equation is solved to calculate the surface temperature. On the oceans, the sea surface temperature is specified as the climatological average for January. The model is used to simulate the January, February and March circulations.

Design analysis and performance assessment of hybrid magnetic bearings for a rotary centrifugal blood pump.

PubMed

Ren, Zhaohui; Jahanmir, Said; Heshmat, Hooshang; Hunsberger, Andrew Z; Walton, James F

2009-01-01

A hybrid magnetic bearing system was designed for a rotary centrifugal blood pump being developed to provide long-term circulatory support for heart failure patients. This design consists of two compact bearings to suspend the rotor in five degrees-of-freedom with single axis active control. Permanent magnets are used to provide passive radial support and electromagnets to maintain axial stability of the rotor. Characteristics of the passive radial and active thrust magnetic bearing system were evaluated by the electromagnetic finite element analysis. A proportional-integral-derivative controller with force balance algorithm was implemented for closed loop control of the magnetic thrust bearing. The control position is continuously adjusted based on the electrical energy in the bearing coils, and thus passive magnetic forces carry static thrust loads to minimize the bearing current. Performance of the magnetic bearing system with associated control algorithm was evaluated at different operating conditions. The bearing current was significantly reduced with the force balance control method and the power consumption was below 0.5 W under various thrust loads. The bearing parameters predicted by the analysis were validated by the experimental data.

The effects of Pilates exercise training on static and dynamic balance in chronic stroke patients: a randomized controlled trial

PubMed Central

Lim, Hee Sung; Kim, You Lim; Lee, Suk Min

2016-01-01

[Purpose] The purpose of this study was to analyze the effects of Pilates exercise on static and dynamic balance in chronic stroke patients. [Subjects and Methods] Nineteen individuals with unilateral chronic hemiparetic stroke (age, 64.7 ± 6.9 years; height, 161.7 ± 7.9 cm; weight, 67.0 ± 11.1 kg) were randomly allocated to either a Pilates exercise group (PG, n=10) or a control group (CG, n=9). The PG attended 24 exercise sessions conducted over an 8-week period (3 sessions/week). Center of pressure (COP) sway and COP velocity were measured one week before and after the exercise program and compared to assess training effects. [Results] Pilates exercise positively affected both static and dynamic balance in patients with chronic stroke. For static balance, COP sway and velocity in the medial-lateral (M-L) and anterior-posterior (A-P) directions were significantly decreased in the PG after training while no significant differences were found in the CG. For dynamic balance, measured during treadmill walking, the PG showed significantly reduced COP sway and velocity in the M-L and A-P directions for both the paretic and non-paretic leg. [Conclusions] The findings provide initial evidence that Pilates exercise can enhance static and dynamic balance in patients with chronic stroke. PMID:27390424

Effect of Ankle Range of Motion (ROM) and Lower-Extremity Muscle Strength on Static Balance Control Ability in Young Adults: A Regression Analysis

PubMed Central

Kim, Seong-Gil

2018-01-01

Background The purpose of this study was to investigate the effect of ankle ROM and lower-extremity muscle strength on static balance control ability in young adults. Material/Methods This study was conducted with 65 young adults, but 10 young adults dropped out during the measurement, so 55 young adults (male: 19, female: 36) completed the study. Postural sway (length and velocity) was measured with eyes open and closed, and ankle ROM (AROM and PROM of dorsiflexion and plantarflexion) and lower-extremity muscle strength (flexor and extensor of hip, knee, and ankle joint) were measured. Pearson correlation coefficient was used to examine the correlation between variables and static balance ability. Simple linear regression analysis and multiple linear regression analysis were used to examine the effect of variables on static balance ability. Results In correlation analysis, plantarflexion ROM (AROM and PROM) and lower-extremity muscle strength (except hip extensor) were significantly correlated with postural sway (p<0.05). In simple correlation analysis, all variables that passed the correlation analysis procedure had significant influence (p<0.05). In multiple linear regression analysis, plantar flexion PROM with eyes open significantly influenced sway length (B=0.681) and sway velocity (B=0.011). Conclusions Lower-extremity muscle strength and ankle plantarflexion ROM influenced static balance control ability, with ankle plantarflexion PROM showing the greatest influence. Therefore, both contractile structures and non-contractile structures should be of interest when considering static balance control ability improvement. PMID:29760375

Effect of Ankle Range of Motion (ROM) and Lower-Extremity Muscle Strength on Static Balance Control Ability in Young Adults: A Regression Analysis.

PubMed

Kim, Seong-Gil; Kim, Wan-Soo

2018-05-15

BACKGROUND The purpose of this study was to investigate the effect of ankle ROM and lower-extremity muscle strength on static balance control ability in young adults. MATERIAL AND METHODS This study was conducted with 65 young adults, but 10 young adults dropped out during the measurement, so 55 young adults (male: 19, female: 36) completed the study. Postural sway (length and velocity) was measured with eyes open and closed, and ankle ROM (AROM and PROM of dorsiflexion and plantarflexion) and lower-extremity muscle strength (flexor and extensor of hip, knee, and ankle joint) were measured. Pearson correlation coefficient was used to examine the correlation between variables and static balance ability. Simple linear regression analysis and multiple linear regression analysis were used to examine the effect of variables on static balance ability. RESULTS In correlation analysis, plantarflexion ROM (AROM and PROM) and lower-extremity muscle strength (except hip extensor) were significantly correlated with postural sway (p<0.05). In simple correlation analysis, all variables that passed the correlation analysis procedure had significant influence (p<0.05). In multiple linear regression analysis, plantar flexion PROM with eyes open significantly influenced sway length (B=0.681) and sway velocity (B=0.011). CONCLUSIONS Lower-extremity muscle strength and ankle plantarflexion ROM influenced static balance control ability, with ankle plantarflexion PROM showing the greatest influence. Therefore, both contractile structures and non-contractile structures should be of interest when considering static balance control ability improvement.

The effect of transcranial direct current stimulation (tDCS) on locomotion and balance in patients with chronic stroke: study protocol for a randomised controlled trial.

PubMed

Geiger, M; Supiot, A; Zory, R; Aegerter, P; Pradon, D; Roche, N

2017-10-23

Following stroke, patients are often left with hemiparesis that reduces balance and gait capacity. A recent, non-invasive technique, transcranial direct current stimulation, can be used to modify cortical excitability when used in an anodal configuration. It also increases the excitability of spinal neuronal circuits involved in movement in healthy subjects. Many studies in patients with stroke have shown that this technique can improve motor, sensory and cognitive function. For example, anodal tDCS has been shown to improve motor performance of the lower limbs in patients with stroke, such as voluntary quadriceps strength, toe-pinch force and reaction time. Nevertheless, studies of motor function have been limited to simple tasks. Surprisingly, the effects of tDCS on the locomotion and balance of patients with chronic stroke have never been evaluated. In this study, we hypothesise that anodal tDCS will improve balance and gait parameters in patients with chronic stroke-related hemiparesis through its effects at cortical and spinal level. This is a prospective, randomised, placebo-controlled, double-blinded, single-centre, cross-over study over 36 months. Forty patients with chronic stroke will be included. Each patient will participate in three visits: an inclusion visit, and two visits during which they will all undergo either one 30-min session of transcranial direct current stimulation or one 30-min session of placebo stimulation in a randomised order. Evaluations will be carried out before, during and twice after stimulation. The primary outcome is the variability of the displacement of the centre of mass during gait and a static-balance task. Secondary outcomes include clinical and functional measures before and after stimulation. A three-dimensional gait analysis, and evaluation of static balance on a force platform will be also conducted before, during and after stimulation. These results should constitute a useful database to determine the aspects of complex motor function that are the most improved by transcranial direct current stimulation in patients with hemiparesis. It is the first essential step towards validating this technique as a treatment, coupled with task-oriented training. ClinicalTrials.gov, ID: NCT02134158 . First received on 18 December 2013; last updated on 14 September 2016. Other study ID numbers: P120135 / AOM12126, 2013-A00952-43.

Mechanics

NASA Astrophysics Data System (ADS)

Cox, John

2014-05-01

Part 1. The Winning of the Principles: 1. Introduction; 2. The beginnings of statics. Archimedes. Problem of the lever and of the centre of gravity; 2. Experimental verification and applications of the principle of the lever; 3. The centre of gravity; 4. The balance; 5. Stevinus of Bruges. The principle of the inclined plane; 6. The parallelogram of forces; 7. The principle of virtual work; 8. Review of the principles of statics; 9. The beginnings of dynamics. Galileo. The problem of falling bodies; 10. Huyghens. The problem of uniform motion in a circle. 'Centrifugal force'; 11. Final statement of the principles of dynamics. Extension to the motions of the heavenly bodies. The law of universal gravitation. Newton; Part II. Mathematical Statement of the Principles: Introduction; 12. Kinematics; 13. Kinetics of a particle moving in a straight line. The laws of motion; 14. Experimental verification of the laws of motion. Atwood's machine; 15. Work and energy; 16. The parallelogram law; 17. The composition and resolution of forces. Resultant. Component. Equilibrium; 18. Forces in one plane; 19. Friction; Part III. Application to Various Problems: 20. Motion on an inclined plane. Brachistochrones; 21. Projectiles; 22. Simple harmonic motion; 23. The simple pendulum; 24. Central forces. The law of gravitation; 25. Impact and impulsive forces; Part IV. The Elements of Rigid Dynamics: 26. The compound pendulum. Huyghens' solution; 27. D'alembert's principle; 28. Moment of inertia; 29. Experimental determination of moments of inertia; 30. Determination of the value of gravity by Kater's pendulum; 31. The constant of gravitation, or weighing the Earth. The Cavendish experiment; Answers to the examples; Index.

Biomechanical implications of lateral pterygoid contribution to biting and jaw opening in humans.

PubMed

Osborn, J W

1995-12-01

The contributions of the lateral pterygoid muscle to a variety of different tasks were analysed by a linear programming mode based on the equations for static equilibrium in three dimensions and containing 12 muscles. The model was used to study lateral pterygoid activity at maximum bite force (MBF) for changes in (i) the direction and point of application of the bite force, (ii) the orientation of the masseter and medial pterygoid muscles and (iii) the slope of the articular eminence (glenoid slope). The effects on MBF of removing one or both lateral pterygoids were also examined. Lateral pterygoid provided a very important indirect contribution to some clenching forces. Under some conditions removing one lateral pterygoid muscle (simulating guarding an injured muscle) halved the MBF. Its activity at MBF was reduced as masseter was tilted more forward, the glenoid slope was made more horizontal and the bite force was made more vertical. The muscle helped to oppose (balance) the horizontal reaction forces at the bite point and joints, which potentially pushed the condyle backward. A balancing muscle is now defined as one (like lateral pterygoid) whose activity increases the output force by far more than its direct contribution to that force. In a larger model containing 16 muscles, every muscle was most active when its line of action was parallel to the output force. Finally, in a model which divided lateral pterygoid into superior and inferior heads, activity suddenly switched from the superior head to the inferior head when the angle of opening changed from 120 degrees (forward from the vertical) to 140 degrees.

Factors predicting dynamic balance and quality of life in home-dwelling elderly women.

PubMed

Karinkanta, S; Heinonen, A; Sievanen, H; Uusi-Rasi, K; Kannus, P

2005-01-01

Proper balance seems to be a critical factor in terms of fall prevention among the elderly. The purpose of this cross-sectional study was to examine factors that are associated with dynamic balance and health-related quality of life in home-dwelling elderly women. One hundred and fifty-three healthy postmenopausal women (mean age: 72 years, height: 159 cm, weight: 72 kg) were examined. General health and physical activity were assessed by a questionnaire. Quality of life was measured using a health-related quality of life questionnaire (Rand 36-Item Health Survey 1.0). Dynamic balance (agility) was tested by a figure-of-eight running test. Static balance (postural sway) was tested on an unstable platform. Maximal isometric strength of the leg extensors was measured with a leg press dynamometer. Dynamic muscle strength of lower limbs was tested by measuring ground reaction forces with a force platform during common daily activities (sit-to-stand and step-on-a-stair tests). Concerning physical activity, 33% of the subjects reported brisk exercise (walking, Nordic walking, cross-country skiing, swimming and aquatic exercises) at least twice a week, and 22% some kind of brisk activity once a week in addition to lighter physical exercise. The remaining 45% did not exercise regularly and were classified as sedentary. The correlations of step-on-a-stair and sit-to-stand ground reaction forces, and leg extensor strength to dynamic balance were from -0.32 to -0.43 (the better the strength, the better the balance). In the regression analysis with backward elimination, step-on-a-stair and sit-to-stand ground reaction forces, and leg extensor strength, age, brisk physical activity, number of diseases and dynamic postural stability explained 42% of the variance in the dynamic balance. Similarly, dynamic balance (figure-of-eight running time), number of diseases and walking more than 3 km per day explained 14% of the variance in the quality of life score. Of these, figure-of-eight running time was the strongest predictor of the quality of life score, explaining 9% of its variance. This study emphasizes the concept that in home-dwelling elderly women good muscle strength in lower limbs is crucial for proper body balance and that dynamic balance is an independent predictor of a standardized quality of life estimate. The results provide important and useful information when planning meaningful contents for studies related to fall prevention and quality of life and interventions in elderly women. Copyright (c) 2005 S. Karger AG, Basel.

A reliable unipedal stance test for the assessment of balance using a force platform.

PubMed

Ponce-González, J G; Sanchis-Moysi, J; González-Henriquez, J J; Arteaga-Ortiz, R; Calbet, J A L; Dorado, C

2014-02-01

The aim was to develop a unipedal stance test for the assessment of balance using a force platform. A single-leg balance test was conducted in 23 students (mean ± SD) age: 23 ± 3 years) in a standard position limiting the movement of the arms and non-supporting leg. Six attempts, with both the jumping (JL) and the contralateral leg (CL), were performed under 3 conditions: 1) eyes opened; 2) eyes closed; 3) eyes opened and executing a precision task. The same protocol was repeated two-week apart. The mean and the best result of the six attempts performed each day were taken as representative of balance. The speed of the centre of pressure (CP-Speed) showed excellent reliability for the "best result" analysis in all tests (ICCs 0.87-0.97), except in the test with the eyes closed performed on the CL (ICC<0.4). The CP-Speed had better reliability with the "best result" than with the "mean result" analysis (P<0.05), whilst no significant differences were observed between the JL and the CL (P=0.71 and P=0.96 for mean and best results analysis, respectively). A lower dispersion in the Bland and Altman graph was observed with the eyes opened than closed, and the dynamic test. The single-leg stance balance test proposed is a reliable method to assess balance, especially when performed in a static position, with the eyes opened and using the best result of six attempts as reference, independently of the stance leg.

The Indeterminate Case of Classical Static Friction When Coupled with Tension

ERIC Educational Resources Information Center

Hahn, Kenneth D.; Russell, Jacob M.

2018-01-01

It has been noted that the static friction force poses challenges for students and, at times, even their instructors. Unlike the gravitational force, which has a precise and unambiguous magnitude (F[subscript G] = mg), the magnitude and direction of the static friction force depend on other forces at play. Friction can be understood rather well in…

Downhill cycling symmetry breaking: how the rider foils experiment

NASA Astrophysics Data System (ADS)

Ben Abu, Yuval; Wolfson, Ira; Bran, Gil; Yizhaq, Hezi

2017-11-01

In high-school teaching of mechanics, we deal, among other things, with the nature of static and kinetic friction, forces that are proportional to the normal force. Under the influence of frictional forces, a body moves down a rough sloped decline at a fixed rate of acceleration that is independent of its mass. This situation does not apply to cases where the frictional force is dependent upon velocity, such as bodies which are moving through a streaming fluid (such as raindrops falling to the ground). In this case the body moves with a continuously decreasing acceleration, eventually reaching a terminal velocity when the frictional and gravitational forces balance out. This velocity constraint is determined by the dependence of the frictional force on velocity and geometric parameters that determine the strength of the frictional force. We show here that a similar situation takes place when bicycles descend an incline with a fixed slope. We also investigated the dependence of the velocity constraint with mass, using bicycles equipped with sophisticated sensors that metamorphose them into data-processing laboratories.

The relationship between balance confidence and control in individuals with Parkinson's disease

PubMed Central

Lee, Hyo Keun; Altman, Lori J.P.; McFarland, Nikolaus; Hass, Chris J.

2016-01-01

Introduction A broad range of subjective and objective assessments have been used to assess balance confidence and balance control in persons with Parkinson's disease (PD). However, little is known about the relationship between self-perceived balance confidence and actual balance control in PD. The purpose of this investigation was to determine the relationship between self-perceived balance confidence and objectively measured static/dynamic balance control abilities. Methods Forty-four individuals with PD participated in the study. Patients were stratified into 2 groups based on the modified Hoehn and Yahr (H&Y) disability score: early stage, H&Y≤2.0 and moderate stage, H&Y ≥2.5. All participants completed the activities-specific balance confidence (ABC) scale and performed standing balance and gait initiation tasks to assess static and dynamic balance control. The center of pressure (COP) sway (CE95%Sway) during static balance and the peak distance between the projections of the COP and the center of mass (COM) in the transverse plane (COPCOM) during gait initiation were calculated. Pearson correlation analyses were conducted relating the ABC score and CE95%Sway and COPCOM. Results For early stage PD, there was a moderate correlation between ABC score and CE95 %Sway (r=-0.56, R2=0.32, p=0.002), while no significant correlation was found between ABC score and COPCOM (r=-0.24, R2=0.06, p=0.227). For moderate stage PD, there was a moderate correlation between ABC score and COPCOM (r=0.49, R2=0.24, p=0.044), while no correlation was found between ABC score and CE95%Sway (r=-0.19, R2=0.04, p=0.478). Conclusion Individuals with different disease severities showed different relationships between balance confidence and actual static/dynamic balance control. PMID:26949065

Propulsion simulator for magnetically-suspended wind tunnel models

NASA Technical Reports Server (NTRS)

Joshi, Prakash B.; Goldey, C. L.; Sacco, G. P.; Lawing, Pierce L.

1991-01-01

The objective of phase two of a current investigation sponsored by NASA Langley Research Center is to demonstrate the measurement of aerodynamic forces/moments, including the effects of exhaust gases, in magnetic suspension and balance system (MSBS) wind tunnels. Two propulsion simulator models are being developed: a small-scale and a large-scale unit, both employing compressed, liquified carbon dioxide as propellant. The small-scale unit was designed, fabricated, and statically-tested at Physical Sciences Inc. (PSI). The large-scale simulator is currently in the preliminary design stage. The small-scale simulator design/development is presented, and the data from its static firing on a thrust stand are discussed. The analysis of this data provides important information for the design of the large-scale unit. A description of the preliminary design of the device is also presented.

Recent NASA Research on Aerodynamic Modeling of Post-Stall and Spin Dynamics of Large Transport Airplanes

NASA Technical Reports Server (NTRS)

Murch, Austin M.; Foster, John V.

2007-01-01

A simulation study was conducted to investigate aerodynamic modeling methods for prediction of post-stall flight dynamics of large transport airplanes. The research approach involved integrating dynamic wind tunnel data from rotary balance and forced oscillation testing with static wind tunnel data to predict aerodynamic forces and moments during highly dynamic departure and spin motions. Several state-of-the-art aerodynamic modeling methods were evaluated and predicted flight dynamics using these various approaches were compared. Results showed the different modeling methods had varying effects on the predicted flight dynamics and the differences were most significant during uncoordinated maneuvers. Preliminary wind tunnel validation data indicated the potential of the various methods for predicting steady spin motions.

A preliminary study of static and dynamic balance in sedentary obese young adults: the relationship between BMI, posture and postural balance.

PubMed

do Nascimento, J A; Silva, C C; Dos Santos, H H; de Almeida Ferreira, J J; de Andrade, P R

2017-12-01

The aim of this study was to evaluate the postural control of obese young adults with normal body mass index during different static (bipedic and unipedic support) and dynamic postural conditions (gait velocity and limits of stability) in order to compare the static and dynamic balance of these individuals. A cross-sectional quantitative study was carried out to evaluate static and dynamic balance in 25 sedentary individuals. The sample was divided into two groups, 10 in the normal-weight group (24.70 ± 3.89 years and 21.5 ± 1.66 kg m -2 ) and 15 in the obese group (26.80 ± 5.16 years and 35.66 ± 4.29 kg m -2 ). Postural evaluation was performed through visual inspection, and balance analyses were performed using the Timed Up & Go test (TUGT) and Balance System (Biodex). Descriptive analyses, Fisher's exact test and Mann Whitney U-tests were performed using the Statistical Package for Social Sciences (SPSS - 20.0, Armonk, NY) software. Most of the obese volunteers presented postural alterations, such as head protrusion (47.6%), hyperkyphosis (46.7%) and hyperlordosis (26.7%). Medial-lateral dynamic displacement, risk of falls and mean time to perform the limits of stability test and TUGT were higher for obese subjects (P < 0.05), while there were no significant differences between the groups (P > 0.05) for static balance tests for either bipedal or unipedal tasks. The disadvantage presented by the young obese subjects occurs in dynamic activities, representing worse balance and an increase in time needed to accomplish these activities. © 2017 World Obesity Federation.

Morphofunctional changes in distribution of pressure center in multiple sclerosis.

PubMed

Neamţu, Marius Cristian; Neamţu, Oana Maria; Enescu Bieru, Denisa; Marin, Mihnea Ion; Rusu, Mihai Robert; Tudorache, Ştefania; Brăila, Anca Daniela; Poiană, Cătălina; Rusu, Ligia

2018-01-01

Gait evaluation and assessment of motor performance are of utmost importance in the clinical management of multiple sclerosis (MS). A new approach to the analysis of static and dynamic balance of MS patients is the use of complex biomechanical analysis that includes an analysis of the distribution of the center of pressure (DCP) and loading, measured by using the pressure and force platforms. The study was conducted on a total of 18 patients with MS, with the mean age of 41.2 years old, divided into two groups, according to the presence of clinically detectable gait disturbances. The biomechanical analysis that included the assessment of the loading and DPC was performed using the platform of force distribution. DPC represented the center of all the forces applied and its value could appreciate the mediolateral stability, hence the pronation or, respectively, the supination. Group 1, consisting of 12 patients with MS with clinically detectable gait disorders, including six men and six women, and group 2, of six MS patients without clinically detectable gait disorders, including two men and four women. For group 1, the center of pressure had a left-right asymmetric distribution, and also an anterior-posterior one. There was a predominant distribution at the medial heel, at metatarsals 1-3 and at the hallux. For group 2, the analysis of the plantograms recorded in our study indicated a tendency of the distribution of the pressure center in the metatarsals 2, 3 and less in the heel. The analysis of the loading and distribution of the pressure center was important not only to appreciate the static equilibrium disorders but also to appreciate how these disorders affected the gait initiation, since the patients suffered from anterior-posterior and mediolateral disorders, which produced spatial and temporal distortion preventing gait initiation. In the study of pressure and force, we noticed a predominant distribution on the lateral region of the heel, explained by an attempt of the body to compensate the disorders of balance and orientation of the reaction force of the ground to normalize the gait.

Static response of coated microbubbles compressed between rigid plates: Simulations and asymptotic analysis including elastic and adhesive forces

NASA Astrophysics Data System (ADS)

Lytra, A.; Pelekasis, N.

2018-03-01

The static response of coated microbubbles is investigated with a novel approach employed for modeling contact between a microbubble and the cantilever of an atomic force microscope. Elastic tensions and moments are described via appropriate constitutive laws. The encapsulated gas is assumed to undergo isothermal variations. Due to the hydrophilic nature of the cantilever, an ultrathin aqueous film is formed, which transfers the force onto the shell. An interaction potential describes the local pressure applied on the shell. The problem is solved in axisymmetric form with the finite element method. The response is governed by the dimensionless bending, k^ b=kb/(χ R02 ), pressure, P^ A=(PAR0 )/χ , and interaction potential, W ^ =w0/χ . Hard polymeric shells have negligible resistance to gas compression, while for the softer lipid shells gas compressibility is comparable with shell elasticity. As the external force increases, numerical simulations reveal that the force versus deformation (f vs d) curve of polymeric shells exhibits a transition from the linear O(d) (Reissner) regime, marked by flattened shapes around the contact region, to a non-linear O(d1/2) (Pogorelov) regime dominated by shapes exhibiting crater formation due to buckling. When lipid shells are tested, buckling is bypassed as the external force increases and flattened shapes prevail in an initially linear f vs d curve. Transition to a curved upwards regime is observed as the force increases, where gas compression and area dilatation form the dominant balance providing a nonlinear regime with an O(d3) dependence. Asymptotic analysis recovers the above patterns and facilitates estimation of the shell mechanical properties.

Can a pilates exercise program be effective on balance, flexibility and muscle endurance? A randomized controlled trial.

PubMed

Kibar, Sibel; Yardimci, Fatma Ö; Evcik, Deniz; Ay, Saime; Alhan, Aslıhan; Manço, Miray; Ergin, Emine S

2016-10-01

This randomized controlled study aims to determine the effect of pilates mat exercises on dynamic and static balance, hamstring flexibility, abdominal muscle activity and endurance in healthy adults. Female healthy volunteer university students randomly assigned into two groups. Group 1 followed a pilates program for an hour two times a week. Group 2 continued daily activities as control group. Dynamic and static balance were evaluated by Sport Kinesthetic Ability Trainer (KAT) 4000 device. Hamstring flexibility and abdominal endurance were determined by sit-and-reach test, curl-up test respectively. Pressure biofeedback unit (PBU) was used to measure transversus abdominis and lumbar muscle activity. The physical activity of the participants was followed by International Physical Activity Questionnaire-Short Form. Twenty-three subjects in pilates group and 24 control subjects completed the study. In pilates group, statistical significant improvements were observed in curl-up, sit-and-reach test, PBU scores at sixth week (P<0.001), and KAT static and dynamic balance scores (P<0.001), waist circumference (P=0.007) at eighth week. In the comparison between two groups, there were significant improvements in pilates group for sit-and-reach test (P=0.01) and PBU scores (P<0.001) at sixth week, additionally curl-up and static KAT scores progressed in eighth week (P<0.001). No correlation was found between flexibility, endurance, trunk muscle activity and balance parameters. An eight-week pilates training program has been found to have beneficial effect on static balance, flexibility, abdominal muscle endurance, abdominal and lumbar muscle activity. These parameters have no effect on balance.

Static balance function in children with a history of preterm birth

PubMed Central

Eshaghi, Zahra; Jafari, Zahra; Jalaie, Shohreh

2015-01-01

Background: The incomplete maturation of brain in preterm children results in long-term neurodevelopmental impairment. This study aimed to investigate the static balance function in children with a history of preterm birth. Methods: Participants were 31 preterm children including 21 moderately preterm (MPT), 10 very preterm (VPT), and 20 term children aged 5.5 and 6.5 years. The cervical vestibular-evoked myogenic potential (cVEMP) test and four static balance subscales of BOT-2 were performed. Results: The VPT children showed a significant increase in P1 and N1 wave latencies in cVEMP test compared to those in the term children (p= 0.041). Mean scores in the four static balance subscales of BOT-2 were significantly lower in the preterm children compared to those in the term children (p= 0.025). The P1 wave latency (p= 0.003) and mean score of standing on a balance beam with open eyes (p= 0.039) were significantly lower in the VPT children compared to those in the MPT children. A significant correlation was observed between the mean score in exercise 4 (standing on one leg on a balance beam with closed eyes) of static balance subscales of BOT-2 and P1 (r= -0.267, p= 0.036) and N1 (r= -0.304, p= 0.016) wave latencies of cVEMP. Conclusion: The longer latency of cVEMP waves along with a poor performance of children with a history of preterm birth suggests a possible defect in central vestibular pathway. PMID:26913273

A cross-sectional study comparing lateral and diagonal maximum weight shift in people with stroke and healthy controls and the correlation with balance, gait and fear of falling

PubMed Central

Meyer, Sarah; Beyens, Hilde; Dejaeger, Eddy; Verheyden, Geert

2017-01-01

Impaired balance is common post stroke and can be assessed by means of force-platforms measuring center of pressure (COP) displacements during static standing, or more dynamically during lateral maximum weight shift (MWS). However, activities of daily life also include diagonal MWS and since force platforms are nowadays commercially available, investigating lateral and diagonal MWS in a clinical setting might be feasible and clinically relevant. We investigated lateral and diagonal MWS while standing in patients with stroke (PwS) and healthy controls (HC), evaluated MWS towards the affected and the non-affected side for PwS and correlated MWS with measures of balance, gait and fear of falling. In a cross-sectional observational study including 36 ambulatory sub-acute inpatients and 32 age-matched HC, a force platform (BioRescue, RM Ingénierie, France) was used to measure lateral and diagonal MWS in standing. Clinical outcome measures collected were Berg Balance Scale and Community Balance and Mobility Scale (CBMS) for balance, 10-meter walk test (10MWT) for gait speed and Falls Efficacy Scale–international version for fear of falling. MWS for PwS towards the affected side was significantly smaller compared to HC (lateral: p = 0.029; diagonal-forward: p = 0.000). MWS for PwS was also significantly reduced towards the affected side in the diagonal-forward direction (p = 0.019) compared to the non-affected side of PwS. Strong correlations were found for MWS for PwS in the diagonal-forward direction towards the affected side, and clinical measures of balance (CBMS: r = 0.66) and gait speed (10MWT: r = 0.66). Our study showed that ambulatory sub-acute PwS, in comparison to HC, have decreased ability to shift their body weight diagonally forward in standing towards their affected side. This reduced ability is strongly related to clinical measures of balance and gait speed. Our results suggest that MWS in a diagonal-forward direction should receive attention in rehabilitation of ambulatory sub-acute PwS in an inpatient setting. PMID:28809939

A cross-sectional study comparing lateral and diagonal maximum weight shift in people with stroke and healthy controls and the correlation with balance, gait and fear of falling.

PubMed

van Dijk, Margaretha M; Meyer, Sarah; Sandstad, Solveig; Wiskerke, Evelyne; Thuwis, Rhea; Vandekerckhove, Chesny; Myny, Charlotte; Ghosh, Nitesh; Beyens, Hilde; Dejaeger, Eddy; Verheyden, Geert

2017-01-01

Impaired balance is common post stroke and can be assessed by means of force-platforms measuring center of pressure (COP) displacements during static standing, or more dynamically during lateral maximum weight shift (MWS). However, activities of daily life also include diagonal MWS and since force platforms are nowadays commercially available, investigating lateral and diagonal MWS in a clinical setting might be feasible and clinically relevant. We investigated lateral and diagonal MWS while standing in patients with stroke (PwS) and healthy controls (HC), evaluated MWS towards the affected and the non-affected side for PwS and correlated MWS with measures of balance, gait and fear of falling. In a cross-sectional observational study including 36 ambulatory sub-acute inpatients and 32 age-matched HC, a force platform (BioRescue, RM Ingénierie, France) was used to measure lateral and diagonal MWS in standing. Clinical outcome measures collected were Berg Balance Scale and Community Balance and Mobility Scale (CBMS) for balance, 10-meter walk test (10MWT) for gait speed and Falls Efficacy Scale-international version for fear of falling. MWS for PwS towards the affected side was significantly smaller compared to HC (lateral: p = 0.029; diagonal-forward: p = 0.000). MWS for PwS was also significantly reduced towards the affected side in the diagonal-forward direction (p = 0.019) compared to the non-affected side of PwS. Strong correlations were found for MWS for PwS in the diagonal-forward direction towards the affected side, and clinical measures of balance (CBMS: r = 0.66) and gait speed (10MWT: r = 0.66). Our study showed that ambulatory sub-acute PwS, in comparison to HC, have decreased ability to shift their body weight diagonally forward in standing towards their affected side. This reduced ability is strongly related to clinical measures of balance and gait speed. Our results suggest that MWS in a diagonal-forward direction should receive attention in rehabilitation of ambulatory sub-acute PwS in an inpatient setting.

The effects of neck and trunk stabilization exercises on cerebral palsy children’s static and dynamic trunk balance: case series

PubMed Central

Shin, Ji-won; Song, Gui-bin; Ko, Jooyeon

2017-01-01

[Purpose] The purpose of this case series was to examination the effects of trunk and neck stabilization exercise on the static, dynamic trunk balance abilities of children with cerebral palsy. [Subjects and Methods] The study included 11 school aged children diagnosed with paraplegia due to a premature birth. Each child engaged in exercise treatments twice per week for eight weeks; each treatment lasted for 45 minutes. After conducting a preliminary assessment, exercise treatments were designed based on each child’s level of functioning. Another assessment was conducted after the eight weeks of treatment. [Results] The Trunk Control Measurement Scale evaluation showed that the exercise treatments had a significant effect on static sitting balance, selective movement control, dynamic reaching, and total Trunk Control Measurement Scale scores. [Conclusion] The results indicate that neck and trunk stabilization exercises that require children’s active participation are helpful for improving static and dynamic balance ability among children diagnosed with cerebral palsy. PMID:28533628

The Seismic Design of Waterfront Retaining Structures

DTIC Science & Technology

1993-01-01

of elastic backfill behind a rigid wall .... .......... .. 134 5.2 Pressure distributions on smooth rigid wall for l-g static horizontal body force...135 5.3 Resultant force and resultant moment on smooth rigid wall for l-g static horizontal body force...distributions on smooth rigid wall for 1-g static horizontal body force clearly showed the limitations of Woods simplified procedure when this condi- tion is not

Prenatal alcohol exposure and childhood balance ability: findings from a UK birth cohort study

PubMed Central

Humphriss, Rachel; Hall, Amanda; May, Margaret; Zuccolo, Luisa; Macleod, John

2013-01-01

Objective To investigate the association of prenatal alcohol exposure with balance in10-year-old children. Design Population-based prospective longitudinal study. Setting Former Avon region of UK (Southwest England). Participants 6915 children from the Avon Longitudinal Study of Parents and Children who had a balance assessment at age 10 and had data on maternal alcohol consumption. Outcome measures 3 composite balance scores: dynamic balance (beam-walking), static balance eyes open, static balance eyes closed (heel-to-toe balance on a beam and standing on one leg, eyes open or closed). Results Most mothers (95.5%) consumed no-to-moderate amounts (3–7 glasses/week) of alcohol during pregnancy. Higher total-alcohol consumption was associated with maternal-social advantage, whereas binge drinking (≥4 units/day) and abstinence were associated with maternal social disadvantage. No evidence was found of an adverse effect of maternal-alcohol consumption on childhood balance. Higher maternal-alcohol use during pregnancy was generally associated with better offspring outcomes, with some specific effects appearing strong (static balance eyes open and moderate total alcohol exposure at 18 weeks, adjusted OR 1.23 (95% CI 1.01 to 1.49); static balance eyes closed and moderate total alcohol exposure at 18 weeks, adjusted OR 1.25 (95% CI 1.06 to 1.48). Similar results were found for both paternal and postnatal maternal alcohol exposure. A Mendelian-randomization approach was used to estimate the association between maternal genotype and offspring balance using the non-synonymous variant rs1229984*A (ADH1B) to proxy for lower maternal alcohol consumption; no strong associations were found between this genotype/proxy and offspring balance. Conclusions No evidence was found to indicate that moderate maternal alcohol consumption in this population sample had an adverse effect on offspring balance at age 10. An apparent beneficial effect of higher total maternal alcohol consumption on offspring balance appeared likely to reflect residual confounding. PMID:23794556

The Relationship Between Maximum Unilateral Squat Strength and Balance in Young Adult Men and Women

PubMed Central

McCurdy, Kevin; Langford, George

2006-01-01

The purpose of this study was to determine the relationship between unilateral squat strength and measures of static balance to compare balance performance between the dominant and non-dominant leg. Seventeen apparently healthy men (mean mass 90.5 ± 20.9 kg and age 21.7 ± 1.8 yrs) and 25 women (mean mass 62.2 ± 14.5 kg and age 21.9 ± 1.3 yrs) completed the study. Weight bearing unilateral strength was measured with a 1RM modified unilateral squat on the dominant and non-dominant leg. The students completed the stork stand and wobble board tests to determine static balance on the dominant and non-dominant leg. Maximum time maintained in the stork stand position, on the ball of the foot with the uninvolved foot against the involved knee with hands on the hips, was recorded. Balance was measured with a 15 second wobble board test. No significant correlations were found between the measurements of unilateral balance and strength (r values ranged between -0.05 to 0.2) for the men and women. Time off balance was not significantly different between the subjects’ dominant (men 1.1 ± 0.4 s; women 0.3 ± 0.1 s) and non-dominant (men 0.9 ± 0.3 s; women 0.3 ± 0.1 s) leg for the wobble board. Similar results were found for the time balanced during the stork stand test on the dominant (men 26.4 ± 6.3 s; women 24.1 ± 5.6 s) and non-dominant (men 26.0 ± 5.7 s; women 21.3 ± 4.1 s) leg. The data indicate that static balance and strength is unrelated in young adult men and women and gains made in one variable after training may not be associated with a change in performance of the other variable. These results also suggest that differences in static balance performance between legs can not be determined by leg dominance. Similar research is needed to compare contralateral leg balance in populations who participate in work or sport activities requiring repetitive asymmetrical use. A better understanding of contralateral balance performance will help practitioners make evaluative decisions during the rehabilitation process. Key Points 1RM unilateral squat strength is unrelated to measures of unilateral static balance in young adult men and women Static balance is similar between the dominant and non-dominant leg in young adult men and women Side-to-side differences in balance warrant assessment and training to correct imbalances prior to participation in activities that present a high risk for injury. PMID:24260001

Validity and Reliability of a Portable Balance Tracking System, BTrackS, in Older Adults.

PubMed

Levy, Susan S; Thralls, Katie J; Kviatkovsky, Shiloah A

Falls are the leading cause of disability, injury, hospital admission, and injury-related death among older adults. Balance limitations have consistently been identified as predictors of falls and increased fall risk. Field measures of balance are limited by issues of subjectivity, ceiling effects, and low sensitivity to change. The gold standard for measuring balance is the force plate; however, its field use is untenable due to high cost and lack of portability. Thus, a critical need is observed for valid objective field measures of balance to accurately assess balance and identify limitations over time. The purpose of this study was to examine the concurrent validity and 3-day test-retest reliability of Balance Tracking System (BTrackS) in community-dwelling older adults. Minimal detectable change values were also calculated to reflect changes in balance beyond measurement error. Postural sway data were collected from community-dwelling older adults (N = 49, mean [SD] age = 71.3 [7.3] years) with a force plate and BTrackS in multitrial eyes open (EO) and eyes closed (EC) static balance conditions. Force sensors transmitted BTrackS data via a USB to a computer running custom software. Three approaches to concurrent validity were taken including calculation of Pearson product moment correlation coefficients, repeated-measures ANOVAs, and Bland-Altman plots. Three-day test-retest reliability of BTrackS was examined in a second sample of 47 community-dwelling older adults (mean [SD] age = 75.8 [7.7] years) using intraclass correlation coefficients and MDC values at 95% CI (MDC95) were calculated. BTrackS demonstrated good validity using Pearson product moment correlations (r > 0.90). Repeated-measures ANOVA and Bland-Altman plots indicated some BTrackS bias with center of pressure (COP) values higher than FP COP values in the EO (mean [SD] bias = 4.0 [6.8]) and EC (mean [SD] bias = 9.6 [12.3]) conditions. Test-retest reliability using intraclass correlation coefficients (ICC2.1 was excellent (0.83) and calculated MDC95 for EO (9.6 cm) and EC (19.4 cm) and suggested that postural sway changes of these amounts are meaningful. BTrackS showed some bias with values exceeding force plate values in both EO and EC conditions. Excellent test-retest reliability and resulting MDC95 values indicated that BTrackS has the potential to identify meaningful changes in balance that may warrant intervention. BTrackS is an objective measure of balance that can be used to monitor balance in community-dwelling older adults over time. It can reliably identify changes that may require further attention (eg, fall-prevention strategies, declines in physical function) and shows promise for assessing intervention efficacy in this growing segment of the population.

The effect of saccular function on static balance ability of profound hearing-impaired children.

PubMed

Jafari, Zahra; Asad Malayeri, Saeed

2011-07-01

Researches have shown that in clinical practice, balance disorders in children with congenital or early acquired severe to profound hearing loss are probable. The purposes of present study were to specify the percentage of vestibular evoked myogenic potential (VEMP) and an acoustically evoked, short latency negative response (ASNR) recordings and the relation between their presence and static balance ability and postural control of children with profound sensorineural hearing loss (SNHL). Thirty children with profound SNHL, with an average age of 6.93 years, underwent the VEMP and auditory brainstem response (ABR) tests. Both VEMP and ABR were recorded at the threshold level through air-conduction stimulation via an insert receiver. The static balance performance of the hearing-impaired children was tested with six exercises and compared with that of 30 age- and sex-matched normal-hearing children as controls. VEMP was recorded in 53.3% of ears and ASNR in 40.0%. VEMP was revealed in all ears with ASNR, and a significant correlation was shown between their presence (p=0.005) and also between the ASNR wave latency and P1 (p=0.0001) and N1 (p=0.004) wave amplitude of VEMP. There was a significant correlation between the presence of VEMP and ASNR with the performance of the children in two static balance skills, namely standing on one leg with eyes open on a line and the same practice on the balance beam (p≤0.008). There was a close relation between the presence of VEMP and ASNR. Additionally, when ASNR was present, the recording of VEMP could be expected. Successful performance in the static balance exercises with reduced vestibular and somatosensory inputs increased the possibility of the recording of ASNR and VEMP. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Static elastica formulations of a pine conveying fluid

NASA Astrophysics Data System (ADS)

Thompson, J. M. T.; Lunn, T. S.

1981-07-01

An elastic pipe in an equilibrium configuration of arbitrary large deflection discharging fluid from its end experiences static centrifugal and frictional drag forces along its complete length. These are, however, entirely equivalent to an end follower force of magnitude ρ AV2. This equivalence is examined in detail by using the intrinsic field equations which are suitable for closed form solutions in terms of elliptic integrals. Once the pipe moves it also experiences gyroscopic Coriolis forces along its length, but these are not considered in this static examination. It is shown in detail how a discharging pipe with end forces and moments is statically equivalent to a beam or strut with the same end forces and moments plus the reversed momentum vector ρ AV2. It is seen that a cantilevered pipe with a free end can have no statical equilibrium states at all, at either large or small deflections, while pipes with constrained ends have large static deflections identical to those of the equivalent struts.

Assessment of Visual Reliance in Balance Control: An Inexpensive Extension of the Static Posturography.

PubMed

Púčik, Jozef; Šaling, Marián; Lukáč, Tomáš; Ondráček, Oldřich; Kucharík, Martin

2014-01-01

Ability of humans to maintain balance in an upright stance and during movement activities is one of the most natural skills affecting everyday life. This ability progressively deteriorates with increasing age, and balance impairment, often aggravated by age-related diseases, can result in falls that adversely impact the quality of life. Falls represent serious problems of health concern associated with aging. Many investigators, involved in different science disciplines such as medicine, engineering, psychology, and sport, have been attracted by a research of the human upright stance. In a clinical practice, stabilometry based on the force plate is the most widely available procedure used to evaluate the balance. In this paper, we have proposed a low-cost extension of the conventional stabilometry by the multimedia technology that allows identifying potentially disturbing effects of visual sensory information. Due to the proposed extension, a stabilometric assessment in terms of line integral of center of pressure (COP) during moving scene stimuli shows higher discrimination power between young healthy and elderly subjects with supposed stronger visual reliance.

Assessment of Visual Reliance in Balance Control: An Inexpensive Extension of the Static Posturography

PubMed Central

Púčik, Jozef; Šaling, Marián; Lukáč, Tomáš; Ondráček, Oldřich; Kucharík, Martin

2014-01-01

Ability of humans to maintain balance in an upright stance and during movement activities is one of the most natural skills affecting everyday life. This ability progressively deteriorates with increasing age, and balance impairment, often aggravated by age-related diseases, can result in falls that adversely impact the quality of life. Falls represent serious problems of health concern associated with aging. Many investigators, involved in different science disciplines such as medicine, engineering, psychology, and sport, have been attracted by a research of the human upright stance. In a clinical practice, stabilometry based on the force plate is the most widely available procedure used to evaluate the balance. In this paper, we have proposed a low-cost extension of the conventional stabilometry by the multimedia technology that allows identifying potentially disturbing effects of visual sensory information. Due to the proposed extension, a stabilometric assessment in terms of line integral of center of pressure (COP) during moving scene stimuli shows higher discrimination power between young healthy and elderly subjects with supposed stronger visual reliance. PMID:27006930

Poor anaerobic power/capability and static balance predicted prospective musculoskeletal injuries among Soldiers of the 101st Airborne (Air Assault) Division.

PubMed

Nagai, Takashi; Lovalekar, Mita; Wohleber, Meleesa F; Perlsweig, Katherine A; Wirt, Michael D; Beals, Kim

2017-11-01

Musculoskeletal injuries have negatively impacted tactical readiness. The identification of prospective and modifiable risk factors of preventable musculoskeletal injuries can guide specific injury prevention strategies for Soldiers and health care providers. To analyze physiological and neuromuscular characteristics as predictors of preventable musculoskeletal injuries. Prospective-cohort study. A total of 491 Soldiers were enrolled and participated in the baseline laboratory testing, including body composition, aerobic capacity, anaerobic power/capacity, muscular strength, flexibility, static balance, and landing biomechanics. After reviewing their medical charts, 275 male Soldiers who met the criteria were divided into two groups: with injuries (INJ) and no injuries (NOI). Simple and multiple logistic regression analyses were used to calculate the odds ratio (OR) and significant predictors of musculoskeletal injuries (p<0.05). The final multiple logistic regression model included the static balance with eyes-closed and peak anaerobic power as predictors of future injuries (p<0.001). The current results highlighted the importance of anaerobic power/capacity and static balance. High intensity training and balance exercise should be incorporated in their physical training as countermeasures. Copyright © 2017 Sports Medicine Australia. All rights reserved.

Space shuttle: Static aerodynamic characteristics and control effectiveness of two delta wing orbiter configurations (M equals 0.6 to 4.96)

NASA Technical Reports Server (NTRS)

Ellis, R. R.; Buchholz, R. E.; Moore, J. A.

1972-01-01

Two 0.00325-scale models of a space shuttle orbiter were tested in trisonic wind tunnel to obtain force, static stability, and control effectiveness data by six component internal strain gauge balance. Two separate configurations were tested; however, the fuselage and basic wing were of one-piece construction. The configurations were varied by replacing the straight wing tip extensions with upswept wing tips. Directional stability was provided for one configuration by a centerline vertical tail. Due to the one-piece body/wing construction, no body-alone data were obtained. The effect of tip fins and vertical tail size were, however, investigated. Both configurations were tested over a Mach range of 0.6 to 4.96 with data taken at angles of attack from minus 4 deg to 60 deg and at angles of sideslip from minus 4 deg to 10 deg.

An experimental study of the effect of tail configuration on the spinning characteristics of general aviation aircraft. M.S. Thesis; [static wind tunnel force measurements

NASA Technical Reports Server (NTRS)

Ballin, M. G.

1982-01-01

The feasibility of using static wind tunnel tests to obtain information about spin damping characteristics of an isolated general aviation aircraft tail was investigated. A representative tail section was oriented to the tunnel free streamline at angles simulating an equilibrium spin. A full range of normally encountered spin conditions was employed. Results of parametric studies performed to determine the effect of spin damping on several tail design parameters show satisfactory agreement with NASA rotary balance tests. Wing and body interference effects are present in the NASA studies at steep spin attitudes, but agreement improves with increasing pitch angle and spin rate, suggesting that rotational flow effects are minimal. Vertical position of the horizontal stabilizer is found to be a primary parameter affecting yaw damping, and horizontal tail chordwise position induces a substantial effect on pitching moment.

The effects of shoulder stabilization exercises and pectoralis minor stretching on balance and maximal shoulder muscle strength of healthy young adults with round shoulder posture.

PubMed

Kim, Mi-Kyoung; Lee, Jung Chul; Yoo, Kyung-Tae

2018-03-01

[Purpose] The purpose of this study was to analyze the effects of pectoralis minor stretching and shoulder strengthening with an elastic band on balance and maximal shoulder muscle strength in young adults with rounded shoulder posture. [Subjects and Methods] Nineteen subjects with rounded shoulder posture were randomly divided into 2 groups: a shoulder stabilization exercise group and a stretching exercise group. The groups performed each exercise for 40 minutes, 3 times a week, for 4 weeks. Static balance (eyes open and closed), dynamic balance (the limits of stability in 4 directions) and shoulder muscle strength in 5 directions were measure before and after the exercises. [Results] The stretching exercise demonstrated a significant difference between the pre- and post-exercise in the static balance with eyes closed and extension and horizontal abduction strength while the stabilization exercise demonstrated significant difference in the left and right directions between the pre- and post-exercise of the dynamic balance and flexion strength. The stabilization exercise demonstrated significant differences shown in the flexion between the pre- and post-test. [Conclusion] The shoulder stabilization and stretching exercises improved the static balance, dynamic balance, and muscle strength.

Postural Stability Assessment of University Marching Musicians Using Force Platform Measures.

PubMed

Magnotti, Trevor D; McElhiney, Danielle; Russell, Jeffrey A

2016-09-01

Lower extremity injury is prevalent in marching musicians, and poor postural stability is a possible risk factor for this. The external load of an instrument may predispose these performers to injury by decreasing postural stability. The purpose of this study was to determine the relationship between instrument load and static and dynamic postural stability in this population. Fourteen university marching musicians were recruited and completed a balance assessment protocol on a force platform with and without their instrument. Mean center of pressure (CoP) displacement was then calculated for each exercise in the anterior/posterior and medial/lateral planes. Mean anterior/posterior CoP displacement significantly increased in the instrument condition for the static surface, eyes closed, 2 feet condition (p≤0.005; d=0.89). No significant differences were found in the medial/lateral plane between non-instrument and instrument conditions. Significant differences were not found between test stance conditions independent of group. Comparisons between the non-instrument-loaded and instrument-loaded conditions revealed possible significance of instrument load on postural stability in the anterior/posterior plane. Mean differences indicated that an unstable surface created a greater destabilizing effect on postural stability than instrument load.

Split torque transmission load sharing

NASA Technical Reports Server (NTRS)

Krantz, T. L.; Rashidi, M.; Kish, J. G.

1992-01-01

Split torque transmissions are attractive alternatives to conventional planetary designs for helicopter transmissions. The split torque designs can offer lighter weight and fewer parts but have not been used extensively for lack of experience, especially with obtaining proper load sharing. Two split torque designs that use different load sharing methods have been studied. Precise indexing and alignment of the geartrain to produce acceptable load sharing has been demonstrated. An elastomeric torque splitter that has large torsional compliance and damping produces even better load sharing while reducing dynamic transmission error and noise. However, the elastomeric torque splitter as now configured is not capable over the full range of operating conditions of a fielded system. A thrust balancing load sharing device was evaluated. Friction forces that oppose the motion of the balance mechanism are significant. A static analysis suggests increasing the helix angle of the input pinion of the thrust balancing design. Also, dynamic analysis of this design predicts good load sharing and significant torsional response to accumulative pitch errors of the gears.

Black holes in an expanding universe.

PubMed

Gibbons, Gary W; Maeda, Kei-ichi

2010-04-02

An exact solution representing black holes in an expanding universe is found. The black holes are maximally charged and the universe is expanding with arbitrary equation of state (P = w rho with -1 < or = for all w < or = 1). It is an exact solution of the Einstein-scalar-Maxwell system, in which we have two Maxwell-type U(1) fields coupled to the scalar field. The potential of the scalar field is an exponential. We find a regular horizon, which depends on one parameter [the ratio of the energy density of U(1) fields to that of the scalar field]. The horizon is static because of the balance on the horizon between gravitational attractive force and U(1) repulsive force acting on the scalar field. We also calculate the black hole temperature.

The relationship between balance confidence and control in individuals with Parkinson's disease.

PubMed

Lee, Hyo Keun; Altmann, Lori J P; McFarland, Nikolaus; Hass, Chris J

2016-05-01

A broad range of subjective and objective assessments have been used to assess balance confidence and balance control in persons with Parkinson's disease (PD). However, little is known about the relationship between self-perceived balance confidence and actual balance control in PD. The purpose of this investigation was to determine the relationship between self-perceived balance confidence and objectively measured static/dynamic balance control abilities. Forty-four individuals with PD participated in the study. Patients were stratified into 2 groups based on the modified Hoehn and Yahr (H&Y) disability score: early stage, H&Y ≤ 2.0 and moderate stage, H&Y ≥ 2.5. All participants completed the activities-specific balance confidence (ABC) scale and performed standing balance and gait initiation tasks to assess static and dynamic balance control. The center of pressure (COP) sway (CE95%Sway) during static balance and the peak distance between the projections of the COP and the center of mass (COM) in the transverse plane (COPCOM) during gait initiation were calculated. Pearson correlation analyses were conducted relating the ABC score and CE95%Sway and COPCOM. For early stage PD, there was a moderate correlation between ABC score and CE95%Sway (r = -0.56, R(2) = 0.32, p = 0.002), while no significant correlation was found between ABC score and COPCOM (r = -0.24, R(2) = 0.06, p = 0.227). For moderate stage PD, there was a moderate correlation between ABC score and COPCOM (r = 0.49, R(2) = 0.24, p = 0.044), while no correlation was found between ABC score and CE95%Sway (r = -0.19, R(2) = 0.04, p = 0.478). Individuals with different disease severities showed different relationships between balance confidence and actual static/dynamic balance control. Copyright © 2016 Elsevier Ltd. All rights reserved.

New Approach in Fibromyalgia Exercise Program: A Preliminary Study Regarding the Effectiveness of Balance Training.

PubMed

Kibar, Sibel; Yıldız, Hatice Ecem; Ay, Saime; Evcik, Deniz; Ergin, Emine Süreyya

2015-09-01

To determine the effectiveness of balance exercises on the functional level and quality of life (QOL) of patients with fibromyalgia syndrome (FMS) and to investigate the circumstances associated with balance disorders in FMS. Randomized controlled trial. Physical medicine and rehabilitation clinic. Patients (N=57) (age range, 18-65y) with FMS were randomly assigned into 2 groups. Group 1 was given flexibility and balance exercises for 6 weeks, whereas group 2 received only a flexibility program as the control group. Functional balance was measured by the Berg Balance Scale (BBS), and dynamic and static balance were evaluated by a kinesthetic ability trainer (KAT) device. Fall risk was assessed with the Hendrich II fall risk model. The Nottingham Health Profile, Fibromyalgia Impact Questionnaire (FIQ), and Beck Depression Inventory (BDI) were used to determine QOL and functional and depression levels, respectively. Assessments were performed at baseline and after the 6-week program. In group 1, statistically significant improvements were observed in all parameters (P<.05), but no improvement was seen in group 2 (P>.05). When comparing the 2 groups, there were significant differences in group 1 concerning the KAT static balance test (P=.017) and FIQ measurements (P=.005). In the correlation analysis, the BDI was correlated with the BBS (r=-.434) and Hendrich II results (r=.357), whereas body mass index (BMI) was correlated with the KAT static balance measurements (r=.433), BBS (r=-.285), and fall frequency (r=.328). A 6-week balance training program had a beneficial effect on the static balance and functional levels of patients with FMS. We also observed that depression deterioration was related to balance deficit and fall risk. Higher BMI was associated with balance deficit and fall frequency. Copyright © 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Vertical Force-deflection Characteristics of a Pair of 56-inch-diameter Aircraft Tires from Static and Drop Tests with and Without Prerotation

NASA Technical Reports Server (NTRS)

Smiley, Robert F; Horne, Walter B

1957-01-01

The vertical force-deflection characteristics were experimentally determined for a pair of 56-inch-diameter tires under static and drop-test conditions with and without prerotation. For increasing force, the tires were found to be least stiff for static tests, almost the same as for the static case for prerotation drop tests as long as the tires remain rotating, and appreciably stiffer for drop tests without prerotation.

Validation of the Balance Board for Clinical Evaluation of Balance During Serious Gaming Rehabilitation Exercises.

PubMed

Bonnechère, Bruno; Jansen, Bart; Omelina, Lubos; Sholukha, Victor; Van Sint Jan, Serge

2016-09-01

Balance and posture can be affected in various conditions or become decreased with aging. A diminution of balance control induces an increase of fall's risk. The Nintendo Wii Balance Board™ (WBB) is used in rehabilitation to perform balance exercises (using commercial video games). The WBB has also been validated to assess balance and posture in static conditions. However, there is currently no study investigating the use of WBB to assess balance during the realization of balance exercises using this device. The aim of this study was to validate the use of WBB, coupled with specially developed serious games, to assess dynamic balance during rehabilitation exercises. Thirty five subjects participated in this study. Subjects were asked to play two specially developed serious games. Center of pressure (CP) displacements were simultaneously recorded with a WBB and a gold standard force plate (FP). Nine parameters were derived from CP displacement. Bland and Altman plots, paired-sample t tests, intraclass correlation coefficient's, and Pearson's coefficient correlations were computed. Excellent correlation between both devices was found for each parameter for the two games (R = 0.95 and 0.96). Unlike previous work on the WBB, these excellent results were obtained without using any calibration procedure. Despite this, results were highly correlated between the WBB and the FP. The WBB could be used in clinics to assess balance during rehabilitation exercises and, thus, allows a more regular patient follow-up.

Visual display and alarm system for wind tunnel static and dynamic loads

NASA Technical Reports Server (NTRS)

Hanly, Richard D.; Fogarty, James T.

1987-01-01

A wind tunnel balance monitor and alarm system developed at NASA Ames Research Center will produce several beneficial results. The costs of wind tunnel delays because of inadvertent balance damage and the costs of balance repair or replacement can be greatly reduced or eliminated with better real-time information on the balance static and dynamic loading. The wind tunnel itself will have enhanced utility with the elimination of overly cautious limits on test conditions. The microprocessor-based system features automatic scaling and 16 multicolored LED bargraphs to indicate both static and dynamic components of the signals from eight individual channels. Five individually programmable alarm levels are available with relay closures for internal or external visual and audible warning devices and other functions such as automatic activation of external recording devices, model positioning mechanisms, or tunnel shutdown.

Visual display and alarm system for wind tunnel static and dynamic loads

NASA Technical Reports Server (NTRS)

Hanly, Richard D.; Fogarty, James T.

1987-01-01

A wind tunnel balance monitor and alarm system developed at NASA Ames Research Center will produce several beneficial results. The costs of wind tunnel delays because of inadvertent balance damage and the costs of balance repair or replacement can be greatly reduced or eliminated with better real-time information on the balance static and dynamic loading. The wind tunnel itself will have enhanced utility with the elimination of overly cautious limits on test conditions. The microprocessor-based system features automatic scaling and 16 multicolored LED bargraphs to indicate both static and dynamic components of the signals from eight individual channels. Five individually programmable alarm levels are available with relay closures for internal or external visual and audible warning devices and other functions such as automatic activation of external recording devices, model positioning mechanism, or tunnel shutdown.

[Postural control disorders in initial phases of whiplash].

PubMed

Pleguezuelos Cobo, Eulogio; García-Alsina, Joan; García Almazán, Concepción; Ortiz Fandiño, Javier; Pérez Mesquida, M Engracia; Guirao Cano, Lluis; Samitier Pastor, Beatriz; Perucho Pont, Cristina; Coll Serra, Estel; Matarrubias, Carlos; Reveron, Genoveva

2009-05-02

Dizziness of variable intensity is a frequent complaint in patients who suffered whiplash and largely documented balance disturbances. The objective of the study was to identify balance disorders in early stage of whiplash after road traffic accidents. Ninety nine women were included in the study. Fifty four women had suffered whiplash within two weeks and 45 were included in a healthy control group. Static posturography on a force platform was carried out in all study participants, by means of the Romberg test in four sequential phases, using the postural sway area (SA) as a dependent variable. Visual Analogic Scale (VAS) and Northwick Park Neck Pain Questionnaire (NPH) were used to evaluate pain and function. Postural sway area increased significantly in each of the consecutive phases in both groups. The differences of the means of the postural sway area were statistically significant in all Romberg phases (p=.009 to P=.000). No correlation was found between SA and VAS or NPH scores. There was a positive correlation between the postural sway area standing on a thick foam cushion placed over the plate with closed eyes and the number of days of transitory incapacity (r=0.414; P=.009). Patients with recent whiplash show a postural control disturbance revealed trough a sequential static posturography analysis. This suggests that the balance disorder is not only a consequence of late whiplash syndrome evolution. Therefore, we should promote early instauration of a specific therapeutic approach if and when the patient refers dizziness and related symptoms.

Flexture plate motion-transfer mechanism, beam-splitter assembly, and interferometer incorporating the same

DOEpatents

Carangelo, R.M.; Dettori, M.D.; Grigely, L.J.; Murray, T.C.; Solomon, P.R.; Dine, C.P. Van; Wright, D.D.

1996-01-23

A multiplicity of one-piece flexure plates are assembled in pairs to provide a support system on which a retroreflector may be mounted for reciprocal motion. Combined with balance bodies, the flexure plates provide a support system having portions that are dynamically and statically balanced with one another, irrespective of orientation, so as to thereby immunize the unit against extraneous forces. The motion transfer assembly is especially adapted for use to support a moving retroreflector in a two-arm interferometer that may further include a beamsplitter assembly constructed from a one-piece, integrally formed body, the body having convergent, optically flat planar surfaces of specular reflectance, and means for adjustably mounting a beamsplitter therein. The spectrometer is of modular construction, and employs an integrated clocking sub-assembly as well as a light-weight voice-coil motor. 15 figs.

Flexture plate motion-transfer mechanism, beam-splitter assembly, and interferometer incorporating the same

DOEpatents

Carangelo, Robert M.; Dettori, Mark D.; Grigely, Lawrence J.; Murray, Terence C.; Solomon, Peter R.; Van Dine, C. Peter; Wright, David D.

1996-01-01

A multiplicity of one-piece flexure plates are assembled in pairs to provide a support system on which a retroreflector may be mounted for reciprocal motion. Combined with balance bodies, the flexure plates provide a support system having portions that are dynamically and statically balanced with one another, irrespective of orientation, so as to thereby immunize the unit against extraneous forces. The motion transfer assembly is especially adapted for use to support a moving retroreflector in a two-arm interferometer that may further include a beamsplitter assembly constructed from a one-piece, integrally formed body, the body having convergent, optically flat planar surfaces of specular reflectance, and means for adjustably mounting a beamsplitter therein. The spectrometer is of modular construction, and employs an integrated clocking sub-assembly as well as a light-weight voice-coil motor.

Biomechanics of Step Initiation After Balance Recovery With Implications for Humanoid Robot Locomotion.

PubMed

Miller Buffinton, Christine; Buffinton, Elise M; Bieryla, Kathleen A; Pratt, Jerry E

2016-03-01

Balance-recovery stepping is often necessary for both a human and humanoid robot to avoid a fall by taking a single step or multiple steps after an external perturbation. The determination of where to step to come to a complete stop has been studied, but little is known about the strategy for initiation of forward motion from the static position following such a step. The goal of this study was to examine the human strategy for stepping by moving the back foot forward from a static, double-support position, comparing parameters from normal step length (SL) to those from increasing SLs to the point of step failure, to provide inspiration for a humanoid control strategy. Healthy young adults instrumented with joint reflective markers executed a prescribed-length step from rest while marker positions and ground reaction forces (GRFs) were measured. The participants were scaled to the Gait2354 model in opensim software to calculate body kinematic and joint kinetic parameters, with further post-processing in matlab. With increasing SL, participants reduced both static and push-off back-foot GRF. Body center of mass (CoM) lowered and moved forward, with additional lowering at the longer steps, and followed a path centered within the initial base of support (BoS). Step execution was successful if participants gained enough forward momentum at toe-off to move the instantaneous capture point (ICP) to within the BoS defined by the final position of both feet on the front force plate. All lower extremity joint torques increased with SL except ankle joint. Front knee work increased dramatically with SL, accompanied by decrease in back-ankle work. As SL increased, the human strategy changed, with participants shifting their CoM forward and downward before toe-off, thus gaining forward momentum, while using less propulsive work from the back ankle and engaging the front knee to straighten the body. The results have significance for human motion, suggesting the upper limit of the SL that can be completed with back-ankle push-off before additional knee flexion and torque is needed. For biped control, the results support stability based on capture-point dynamics and suggest strategy for center-of-mass trajectory and distribution of ground force reactions that can be compared with robot controllers for initiation of gait after recovery steps.

Laboratory evidence that line-tied tension forces can suppress loss-of-equilibrium flux rope eruptions in the solar corona

NASA Astrophysics Data System (ADS)

Myers, C. E.; Yamada, M.; Belova, E.; Ji, H.; Yoo, J.; Fox, W.; Jara-Almonte, J.; Gao, L.

2014-10-01

Loss-of-equilibrium mechanisms such as the ideal torus instability [Kliem & Török, Phys. Rev. Lett. 96, 255002 (2006)] are predicted to drive arched flux ropes in the solar corona to erupt. In recent line-tied flux rope experiments conducted in the Magnetic Reconnection Experiment (MRX), however, we find that quasi-statically driven flux ropes remain confined well beyond the predicted torus instability threshold. In order to understand this behavior, in situ measurements from a 300 channel 2D magnetic probe array are used to comprehensively analyze the force balance between the external (vacuum) and internal (plasma-generated) magnetic fields. We find that the line-tied tension force--a force that is not included in the basic torus instability theory--plays a major role in preventing eruptions. The dependence of this tension force on various vacuum field and flux rope parameters will be discussed. This research is supported by DoE Contract Number DE-AC02-09CH11466 and by the NSF/DoE Center for Magnetic Self-Organization (CMSO).

The relationship between infratentorial lesions, balance deficit and accidental falls in multiple sclerosis.

PubMed

Prosperini, Luca; Kouleridou, Anna; Petsas, Nikolaos; Leonardi, Laura; Tona, Francesca; Pantano, Patrizia; Pozzilli, Carlo

2011-05-15

The role of static posturography and magnetic resonance imaging (MRI) in identifying patients at high risk of falls was investigated. Relationships between static posturography measures and MRI metrics were also investigated. A total of 31 ambulatory MS patients (EDSS ranging from 2.0 to 5.0) with a predominant balance disorder were recruited. Each patient underwent a static posturography with a monoaxial platform and a conventional 1.5 T brain MRI scan. Measurements of T1-hypointense and T2-hyperintense lesion volumes (LVs), focusing on lesions selectively located at infratentorial levels, were performed by two operators unaware of clinical data. The self-reported number of falls in the previous 6 months was considered as the main outcome measure. Fourteen (45%) patients reported 1 or more falls over the past 6 months. When compared to non-faller patients, they had a higher EDSS score, poorer static standing balance, and greater brainstem and middle cerebellar peduncle (MCP) T2-LVs. A strength correlation between brainstem T2-LV and impaired static standing balance in an open eye condition was also found. In the multivariate analysis, the variables more strictly associated with recurrent falls were greater T2-LV at the MCP (beta: 6.2; p=0.01) and brainstem (beta: 5.8; p=0.001) levels, and a wider displacement of the body center of pressure in the closed eye condition (beta: 0.02; p=0.03). Our data suggests that the damage of specific infratentorial areas negatively affect the static standing balance and may predispose MS patients to accidental falls. These findings might contribute in selecting patients requiring a proper rehabilitation intervention program. Copyright © 2011 Elsevier B.V. All rights reserved.

The Effects of Shoulder Slings on Balance in Patients With Hemiplegic Stroke.

PubMed

Sohn, Min Kyun; Jee, Sung Ju; Hwang, Pyoungsik; Jeon, Yumi; Lee, Hyunkeun

2015-12-01

To investigate the effects of a shoulder sling on balance in patients with hemiplegia. Twenty-seven hemiplegic stroke patients (right 13, left 14) were enrolled in this study. The subjects' movement in their centers of gravity (COGs) during their static and dynamic balance tests was measured with their eyes open in each sling condition-without a sling, with Bobath's axillary support (Bobath sling), and with a simple arm sling. The percent times in quadrant, overall, anterior/posterior, and medial/lateral stability indexes were measured using a posturography platform (Biodex Balance System SD). Functional balance was evaluated using the Berg Balance Scale and the Trunk Impairment Scale. All balance tests were performed with each sling in random order. The COGs of right hemiplegic stroke patients and all hemiplegic stroke patients shifted to, respectively, the right and posterior quadrants during the static balance test without a sling (p<0.05). This weight asymmetry pattern did not improve with either the Bobath or the simple arm sling. There was no significant improvement in any stability index during either the static or the dynamic balance tests in any sling condition. The right and posterior deviations of the hemiplegic stroke patients' COGs were maintained during the application of the shoulder slings, and there were no significant effects of the shoulder slings on the patients' balance in the standing still position.

The Effects of Shoulder Slings on Balance in Patients With Hemiplegic Stroke

PubMed Central

Sohn, Min Kyun; Jee, Sung Ju; Hwang, Pyoungsik; Jeon, Yumi

2015-01-01

Objective To investigate the effects of a shoulder sling on balance in patients with hemiplegia. Methods Twenty-seven hemiplegic stroke patients (right 13, left 14) were enrolled in this study. The subjects' movement in their centers of gravity (COGs) during their static and dynamic balance tests was measured with their eyes open in each sling condition-without a sling, with Bobath's axillary support (Bobath sling), and with a simple arm sling. The percent times in quadrant, overall, anterior/posterior, and medial/lateral stability indexes were measured using a posturography platform (Biodex Balance System SD). Functional balance was evaluated using the Berg Balance Scale and the Trunk Impairment Scale. All balance tests were performed with each sling in random order. Results The COGs of right hemiplegic stroke patients and all hemiplegic stroke patients shifted to, respectively, the right and posterior quadrants during the static balance test without a sling (p<0.05). This weight asymmetry pattern did not improve with either the Bobath or the simple arm sling. There was no significant improvement in any stability index during either the static or the dynamic balance tests in any sling condition. Conclusion The right and posterior deviations of the hemiplegic stroke patients' COGs were maintained during the application of the shoulder slings, and there were no significant effects of the shoulder slings on the patients' balance in the standing still position. PMID:26798614

Static and dynamic balance of children and adolescents with sensorineural hearing loss.

PubMed

Melo, Renato de Souza; Marinho, Sônia Elvira Dos Santos; Freire, Maryelly Evelly Araújo; Souza, Robson Arruda; Damasceno, Hélio Anderson Melo; Raposo, Maria Cristina Falcão

2017-01-01

To assess the static and dynamic balance performance of students with normal hearing and with sensorineural hearing loss. A cross-sectional study assessing 96 students, 48 with normal hearing and 48 with sensorineural hearing loss of both sexes, aged 7 and 18 years. To evaluate static balance, Romberg, Romberg-Barré and Fournier tests were used; and for the dynamic balance, we applied the Unterberger test. Hearing loss students showed more changes in static and dynamic balance as compared to normal hearing, in all tests used (p<0.001). The same difference was found when subjects were grouped by sex. For females, Romberg, Romberg-Barré, Fournier and Unterberger test p values were, respectively, p=0.004, p<0.001, p<0.001 and p=0.023; for males, the p values were p=0.009, p<0.001, p<0.001 and p=0.002, respectively. The same difference was observed when students were classified by age. For 7 to 10 years old students, the p values for Romberg, Romberg-Barré and Fournier tests were, respectively, p=0.007, p<0.001 and p=0.001; for those aged 11 and 14 years, the p values for Romberg, Romberg-Barré, Fournier and Unterberger tests were p=0.002, p<0.001, p<0.001 and p=0.015, respectively; and for those aged 15 and 18 years, the p values for Romberg-Barré, Fournier and Unterberger tests were, respectively, p=0.037, p<0.001 and p=0.037. Hearing-loss students showed more changes in static and dynamic balance comparing to normal hearing of same sex and age groups.

Acute effects of static stretching on passive stiffness and postural balance in healthy, elderly men.

PubMed

Palmer, Ty B; Agu-Udemba, Chinonye C; Palmer, Bailey M

2018-02-01

This study aimed to examine the acute effects of straight-leg raise (SLR) static stretching on passive stiffness and postural balance in healthy, elderly men. An additional aim of this study was to examine the relationships between stiffness and balance at baseline (prior to stretching) and the relationships between the stretch-induced changes in these variables. Eleven elderly men (age = 69 ± 6 years; height = 177 ± 7 cm; mass = 83 ± 13 kg) underwent postural balance and passive stiffness assessments before and after: 1) a stretching treatment consisting of four, 15-s SLR static stretches performed by the primary investigator and 2) a control treatment consisting of no static stretching. Passive stiffness was calculated from the slopes of the initial (phase 1) and final (phase 2) portions of the angle-torque curve. Unilateral postural balance was assessed on the right leg using a commercially designed balance testing device, which provides a measurement of static stability based on the overall stability index (OSI). The slope coefficients and OSI values decreased from pre- to post-treatment for the stretching intervention (P = 0.015 and 0.018, respectively); however, there were no changes for the control (P = 0.654 and 0.920). For the stretching intervention, a significant positive relationship was observed between OSI and the slope coefficient of phase 1 at baseline (r = 0.619; P = 0.042). A significant positive relationship was also observed between the stretched-induced changes in OSI and the slope coefficient of phase 1 (r = 0.731; P = 0.011). No relationship was observed between OSI and the slope coefficient of phase 2 at baseline (r = 0.262; P = 0.437) nor was there a relationship between the changes in these variables (r = 0.419; P = 0.200). A short, practical bout of SLR static stretching may be an effective intervention for reducing passive stiffness and improving postural balance in healthy, elderly men.

A lower-limb training program to improve balance in healthy elderly women using the T-bow device.

PubMed

Chulvi-Medrano, Iván; Colado, Juan C; Pablos, Carlos; Naclerio, Fernando; García-Massó, Xavier

2009-06-01

Ageing impairs balance, which increases the risk of falls. Fall-related injuries are a serious health problem associated with dependency and disability in the elderly and results in high costs to public health systems. This study aims to determine the effects of a training program to develop balance using a new device called the T-Bow. A total of 28 women > 65 years were randomly assigned to an experimental group (EG) (n = 18; 69.50 [0.99] years), or a control group (CG) (n = 10; 70.70 [2.18] years). A program for lower limbs was applied for 8 weeks using 5 exercises on the T-Bow: squat, lateral and frontal swings, lunges, and plantarflexions. The intensity of the exercises was controlled by time of exposure, support base, and ratings of perceived exertion. Clinical tests were used to evaluate variables of balance. Static balance was measured by a 1-leg balance test (unipedal stance test), dynamic balance was measured by the 8-foot-up-and-go test, and overall balance was measured using the Tinetti test. Results for the EG showed an increase of 35.2% in static balance (P < 0.005), 12.7% in dynamic balance (P < 0.005), and 5.9% in overall balance (P > 0.05). Results for the CG showed a decline of 5.79% in static balance (P > 0.05) but no change in the other balance variables. Thus the data suggest that implementing a training program using the T-Bow could improve balance in healthy older women.

Novel models and algorithms of load balancing for variable-structured collaborative simulation under HLA/RTI

NASA Astrophysics Data System (ADS)

Yue, Yingchao; Fan, Wenhui; Xiao, Tianyuan; Ma, Cheng

2013-07-01

High level architecture(HLA) is the open standard in the collaborative simulation field. Scholars have been paying close attention to theoretical research on and engineering applications of collaborative simulation based on HLA/RTI, which extends HLA in various aspects like functionality and efficiency. However, related study on the load balancing problem of HLA collaborative simulation is insufficient. Without load balancing, collaborative simulation under HLA/RTI may encounter performance reduction or even fatal errors. In this paper, load balancing is further divided into static problems and dynamic problems. A multi-objective model is established and the randomness of model parameters is taken into consideration for static load balancing, which makes the model more credible. The Monte Carlo based optimization algorithm(MCOA) is excogitated to gain static load balance. For dynamic load balancing, a new type of dynamic load balancing problem is put forward with regards to the variable-structured collaborative simulation under HLA/RTI. In order to minimize the influence against the running collaborative simulation, the ordinal optimization based algorithm(OOA) is devised to shorten the optimization time. Furthermore, the two algorithms are adopted in simulation experiments of different scenarios, which demonstrate their effectiveness and efficiency. An engineering experiment about collaborative simulation under HLA/RTI of high speed electricity multiple units(EMU) is also conducted to indentify credibility of the proposed models and supportive utility of MCOA and OOA to practical engineering systems. The proposed research ensures compatibility of traditional HLA, enhances the ability for assigning simulation loads onto computing units both statically and dynamically, improves the performance of collaborative simulation system and makes full use of the hardware resources.

Superhydrophobic gecko feet with high adhesive forces towards water and their bio-inspired materials.

PubMed

Liu, Kesong; Du, Jiexing; Wu, Juntao; Jiang, Lei

2012-02-07

Functional integration is an inherent characteristic for multiscale structures of biological materials. In this contribution, we first investigate the liquid-solid adhesive forces between water droplets and superhydrophobic gecko feet using a high-sensitivity micro-electromechanical balance system. It was found, in addition to the well-known solid-solid adhesion, the gecko foot, with a multiscale structure, possesses both superhydrophobic functionality and a high adhesive force towards water. The origin of the high adhesive forces of gecko feet to water could be attributed to the high density nanopillars that contact the water. Inspired by this, polyimide films with gecko-like multiscale structures were constructed by using anodic aluminum oxide templates, exhibiting superhydrophobicity and a strong adhesive force towards water. The static water contact angle is larger than 150° and the adhesive force to water is about 66 μN. The resultant gecko-inspired polyimide film can be used as a "mechanical hand" to snatch micro-liter liquids. We expect this work will provide the inspiration to reveal the mechanism of the high-adhesive superhydrophobic of geckos and extend the practical applications of polyimide materials. This journal is © The Royal Society of Chemistry 2012

Effect of a single session of transcranial direct-current stimulation combined with virtual reality training on the balance of children with cerebral palsy: a randomized, controlled, double-blind trial

PubMed Central

Lazzari, Roberta Delasta; Politti, Fabiano; Santos, Cibele Alimedia; Dumont, Arislander Jonathan Lopes; Rezende, Fernanda Lobo; Grecco, Luanda André Collange; Braun Ferreira, Luiz Alfredo; Oliveira, Claudia Santos

2015-01-01

[Purpose] The aim of the present study was to investigate the effects of a single session of transcranial direct current stimulation combined with virtual reality training on the balance of children with cerebral palsy. [Subjetcs and Methods] Children with cerebral palsy between four and 12 years of age were randomly allocated to two groups: an experimental group which performed a single session of mobility training with virtual reality combined with active transcranial direct current stimulation; and a control group which performed a single session of mobility training with virtual reality combined with placebo transcranial direct current stimulation. The children were evaluated before and after the training protocols. Static balance (sway area, displacement, velocity and frequency of oscillations of the center of pressure on the anteroposterior and mediolateral axes) was evaluated using a force plate under four conditions (30-second measurements for each condition): feet on the force plate with the eyes open, and with the eyes closed; feet on a foam mat with the eyes open, and with the eyes closed. [Results] An increase in sway velocity was the only significant difference found. [Conclusion] A single session of anodal transcranial direct current stimulation combined with mobility training elicited to lead to an increase in the body sway velocity of children with cerebral palsy. PMID:25931726

Balance training and center-of-pressure location in participants with chronic ankle instability.

PubMed

Mettler, Abby; Chinn, Lisa; Saliba, Susan A; McKeon, Patrick O; Hertel, Jay

2015-04-01

Chronic ankle instability (CAI) occurs in some people after a lateral ankle sprain and often results in residual feelings of instability and episodes of the ankle's giving way. Compared with healthy people, patients with CAI demonstrated poor postural control and used a more anteriorly and laterally positioned center of pressure (COP) during a single-limb static-balance task on a force plate. Balance training is an effective means of altering traditional COP measures; however, whether the overall location of the COP distribution under the foot also changes is unknown. To determine if the spatial locations of COP data points in participants with CAI change after a 4-week balance-training program. Randomized controlled trial. Laboratory. Thirty-one persons with self-reported CAI. Participants were randomly assigned to a 4-week balance-training program or no balance training. We collected a total of 500 COP data points while participants balanced using a single limb on a force plate during a 10-second trial. The location of each COP data point relative to the geometric center of the foot was determined, and the frequency count in 4 sections (anteromedial, anterolateral, posteromedial, posterolateral) was analyzed for differences between groups. Overall, COP position in the balance-training group shifted from being more anterior to less anterior in both eyes-open trials (before trial = 319.1 ± 165.4, after trial = 160.5 ± 149.5; P = .006) and eyes-closed trials (before trial = 387.9 ± 123.8, after trial = 189.4 ± 102.9; P < .001). The COP for the group that did not perform balance training remained the same in the eyes-open trials (before trial = 214.1 ± 193.3, after trial = 230.0 ± 176.3; P = .54) and eyes-closed trials (before trial = 326.9 ± 134.3, after trial = 338.2 ± 126.1; P = .69). In participants with CAI, the balance-training program shifted the COP location from anterolateral to posterolateral. The program may have repaired some of the damaged sensorimotor system pathways, resulting in a more optimally functioning and less constrained system.

Effect of a Hippotherapy Intervention Program on Static Balance and Strength in Adolescents with Intellectual Disabilities

ERIC Educational Resources Information Center

Giagazoglou, Paraskevi; Arabatzi, Fotini; Dipla, Konstantina; Liga, Maria; Kellis, Eleftherios

2012-01-01

The aim of this study was to assess the effects of a hippotherapy program on static balance and strength in adolescents with intellectual disability (ID). Nineteen adolescents with moderate ID were assigned either an experimental group (n = 10) or a control group (n = 9). The experimental group attended a 10-week hippotherapy program. To assess…

[Static posturography versus clinical tests in elderly people with vestibular pathology].

PubMed

Ortuño-Cortés, Miguel A; Martín-Sanz, Eduardo; Barona-de Guzmán, Rafael

2008-01-01

Balance can be quantified by clinical tests and through instrumental studies. The objective of this paper is to determine the correlation between static posturography and 4 clinical tests of balance in elderly people with vestibular disorders and to identify its capability to discriminate the groups studied. 60 patients with vestibular disorders and 60 healthy subjects performed 4 clinical tests (one leg standing with opened eyes, Timed Up and Go, Tinetti and Berg tests) and a static posturography analysis (NedSVE/IBV system) under 4 conditions: Romberg Test, Eyes Open (REO), Romberg Test, Eyes Closed (REC), Romberg Test on Foam with Eyes Open (RFEO), and Romberg Test on Foam with Eyes Closed (RFEC). RFEO correlated best with the clinical tests and RFEC was the worst. RFEO distinguished between healthy individuals and decompensated patients. RFEO gave the best information about postural balance in the elderly. RFEC was not useful. Static posturography can be useful to distinguish vestibular compensation status.

Injury incidence and balance in rugby players.

PubMed

M, Jaco Ras; Puckree, Threethambal

2014-01-01

Objective : This study determined and correlated injury incidence and balance in rugby players. A prospective survey with balance testing was conducted on first year rugby academy players (N= 114). Injury incidence, static and dynamic balance were tested pre and post-season using a Biosway portable balance system. The data was analysed using paired and independent samples t-tests at p<0.05, Odds ratios, and Spearman's correlation coefficients. 75.50% participated, 71.40% were 18 years old, and 71.40% were White. Injury was sustained by 83% of players with the knee (25%) most commonly injured. Injury incidence was 1.52 per player with an injury rate of 5.95 injuries per 1000 match playing hours. The Stability Index increased significantly (p=0.03) by 15% in the medial/lateral direction post-season compared to pre-season. Significant differences in post-test anterior posterior and overall static and front and front right dynamic stability between injured and uninjured players were noted. Risk factors for injury included the scrum-half (14.80%) playing position, injuries in the 2nd half of the match (57%), and during contact (67%). Conclusion : Injury incidence was related to static and dynamic balance in forward right direction only.

Injury incidence and balance in rugby players

PubMed Central

M, Jaco Ras; Puckree, Threethambal

2014-01-01

Objective : This study determined and correlated injury incidence and balance in rugby players. Methods: A prospective survey with balance testing was conducted on first year rugby academy players (N= 114). Injury incidence, static and dynamic balance were tested pre and post-season using a Biosway portable balance system. The data was analysed using paired and independent samples t-tests at p<0.05, Odds ratios, and Spearman’s correlation coefficients. Results: 75.50% participated, 71.40% were 18 years old, and 71.40% were White. Injury was sustained by 83% of players with the knee (25%) most commonly injured. Injury incidence was 1.52 per player with an injury rate of 5.95 injuries per 1000 match playing hours. The Stability Index increased significantly (p=0.03) by 15% in the medial/lateral direction post-season compared to pre-season. Significant differences in post-test anterior posterior and overall static and front and front right dynamic stability between injured and uninjured players were noted. Risk factors for injury included the scrum-half (14.80%) playing position, injuries in the 2nd half of the match (57%), and during contact (67%). Conclusion : Injury incidence was related to static and dynamic balance in forward right direction only. PMID:25674136

Actuator placement in prestressed adaptive trusses for vibration control

NASA Technical Reports Server (NTRS)

Jalihal, P.; Utku, Senol; Wada, Ben K.

1993-01-01

This paper describes the optimal location selection of actuators for vibration control in prestressed adaptive trusses. Since prestressed adaptive trusses are statically indeterminate, the actuators to be used for vibration control purposes must work against (1) existing static axial prestressing forces, (2) static axial forces caused by the actuation, and (3) dynamic axial forces caused by the motion of the mass. In statically determinate adaptive trusses (1) and (2) are non - existing. The actuator placement problem in statically indeterminate trusses is therefore governed by the actuation energy and the actuator strength requirements. Assuming output feedback type control of selected vibration modes in autonomous systems, a procedure is given for the placement of vibration controlling actuators in prestressed adaptive trusses.

Length oscillation mimicking periodic individual deep inspirations during tidal breathing attenuates force recovery and adaptation in airway smooth muscle.

PubMed

Raqeeb, Abdul; Solomon, Dennis; Paré, Peter D; Seow, Chun Y

2010-11-01

Airway smooth muscle (ASM) is able to generate maximal force under static conditions, and this isometric force can be maintained over a large length range due to length adaptation. The increased force at short muscle length could lead to excessive narrowing of the airways. Prolonged exposure of ASM to submaximal stimuli also increases the muscle's ability to generate force in a process called force adaptation. To date, the effects of length and force adaptation have only been demonstrated under static conditions. In the mechanically dynamic environment of the lung, ASM is constantly subjected to periodic stretches by the parenchyma due to tidal breathing and deep inspiration. It is not known whether force recovery due to muscle adaptation to a static environment could occur in a dynamic environment. In this study the effect of length oscillation mimicking tidal breathing and deep inspiration was examined. Force recovery after a length change was attenuated in the presence of length oscillation, except at very short lengths. Force adaptation was abolished by length oscillation. We conclude that in a healthy lung (with intact airway-parenchymal tethering) where airways are not allowed to narrow excessively, large stretches (associated with deep inspiration) may prevent the ability of the muscle to generate maximal force that would occur under static conditions irrespective of changes in mean length; mechanical perturbation on ASM due to tidal breathing and deep inspiration, therefore, is the first line of defense against excessive bronchoconstriction that may result from static length and force adaptation.

Forces associated with pneumatic power screwdriver operation: statics and dynamics.

PubMed

Lin, Jia-Hua; Radwin, Robert G; Fronczak, Frank J; Richard, Terry G

2003-10-10

The statics and dynamics of pneumatic power screwdriver operation were investigated in the context of predicting forces acting against the human operator. A static force model is described in the paper, based on tool geometry, mass, orientation in space, feed force, torque build up, and stall torque. Three common power hand tool shapes are considered, including pistol grip, right angle, and in-line. The static model estimates handle force needed to support a power nutrunner when it acts against the tightened fastener with a constant torque. A system of equations for static force and moment equilibrium conditions are established, and the resultant handle force (resolved in orthogonal directions) is calculated in matrix form. A dynamic model is formulated to describe pneumatic motor torque build-up characteristics dependent on threaded fastener joint hardness. Six pneumatic tools were tested to validate the deterministic model. The average torque prediction error was 6.6% (SD = 5.4%) and the average handle force prediction error was 6.7% (SD = 6.4%) for a medium-soft threaded fastener joint. The average torque prediction error was 5.2% (SD = 5.3%) and the average handle force prediction error was 3.6% (SD = 3.2%) for a hard threaded fastener joint. Use of these equations for estimating handle forces based on passive mechanical elements representing the human operator is also described. These models together should be useful for considering tool handle force in the selection and design of power screwdrivers, particularly for minimizing handle forces in the prevention of injuries and work related musculoskeletal disorders.

Effects of Water-Based Training on Static and Dynamic Balance of Older Women.

PubMed

Bento, Paulo Cesar Barauce; Lopes, Maria de Fátima A; Cebolla, Elaine Cristine; Wolf, Renata; Rodacki, André L F

2015-08-01

The aim of this study was to evaluate the effects of a water-based exercise program on static and dynamic balance. Thirty-six older women were randomly assigned to a water-based training (3 days/week for 12 weeks) or control group. Water level was kept at the level of the xiphoid process and temperature at ∼28-30°C. Each session included aerobic activities and lower limb strength exercises. The medial-lateral, the anterior-posterior amplitude, and displacement of the center of pressure (CP-D) were measured in a quiet standing position (60 sec eyes opened and closed). The dynamic balance and 8-Foot Up-and-Go tests were also applied. Group comparisons were made using two-way analysis of variance (ANOVA) with repeated measures. No differences were found in the center of pressure variables; however, the WBT group showed better performance in the 8 Foot Up-and-Go Test after training (5.61±0.76 vs. 5.18±0.42; p<0.01). The water-based training was effective in improving dynamic balance, but not static balance.

Status of MSBS Study at NAL in 1995

NASA Technical Reports Server (NTRS)

Sawada, Hideo; Suenaga, Hisasi; Kunimasu, Tetuya; Kohno, Takashi

1996-01-01

Magnetic field intensity and currents passing through the coils of the National Aerospace Laboratory (NAL) 1O cm Magnetic Suspension and Balance System (MSBS) were measured while a cylindrical model was oscillated along x,y,z and also about y and z axes, respectively. The model was made of alnico 5 and was 8 mm in diameter and 60 mm long. Two kinds of tests were carried out. Amplitude of the oscillation was varied at a frequency of 10 Hz. Frequency was varied from 1 to 50 Hz in the other test. Results of the tests show that the relation between coil currents and magnetic force acting on the model is affected by frequency. They also show that the relation between measured magnetic field intensity and the force in vertical direction is independent of the frequency below 30 Hz. Using the measured magnetic field intensity, the vertical force can be evaluated at the MSBS instantaneously when a model moves at frequencies below 30 Hz. A static drag force calibration test was carried out at the 60 cm MSBS. Obtained relationships between measured drag coil currents and loads shows large hysteresis.

Local Viscoelastic Properties of Live Cells Investigated Using Dynamic and Quasi-Static Atomic Force Microscopy Methods

PubMed Central

Cartagena, Alexander; Raman, Arvind

2014-01-01

The measurement of viscoelasticity of cells in physiological environments with high spatio-temporal resolution is a key goal in cell mechanobiology. Traditionally only the elastic properties have been measured from quasi-static force-distance curves using the atomic force microscope (AFM). Recently, dynamic AFM-based methods have been proposed to map the local in vitro viscoelastic properties of living cells with nanoscale resolution. However, the differences in viscoelastic properties estimated from such dynamic and traditional quasi-static techniques are poorly understood. In this work we quantitatively reconstruct the local force and dissipation gradients (viscoelasticity) on live fibroblast cells in buffer solutions using Lorentz force excited cantilevers and present a careful comparison between mechanical properties (local stiffness and damping) extracted using dynamic and quasi-static force spectroscopy methods. The results highlight the dependence of measured viscoelastic properties on both the frequency at which the chosen technique operates as well as the interactions with subcellular components beyond certain indentation depth, both of which are responsible for differences between the viscoelasticity property maps acquired using the dynamic AFM method against the quasi-static measurements. PMID:24606928

The Influence of Friction Between Football Helmet and Jersey Materials on Force: A Consideration for Sport Safety.

PubMed

Rossi, Anthony M; Claiborne, Tina L; Thompson, Gregory B; Todaro, Stacey

2016-09-01

The pocketing effect of helmet padding helps to dissipate forces experienced by the head, but if the player's helmet remains stationary in an opponent's shoulder pads, the compressive force on the cervical spine may increase. To (1) measure the coefficient of static friction between different football helmet finishes and football jersey fabrics and (2) calculate the potential amount of force on a player's helmet due to the amount of friction present. Cross-sectional study. Laboratory. Helmets with different finishes and different football jersey fabrics. The coefficient of friction was determined for 2 helmet samples (glossy and matte), 3 football jerseys (collegiate, high school, and youth), and 3 types of jersey numbers (silkscreened, sublimated, and stitched on) using the TAPPI T 815 standard method. These measurements determined which helmet-to-helmet, helmet-to-jersey number, and helmet-to-jersey material combination resulted in the least amount of static friction. The glossy helmet versus glossy helmet combination produced a greater amount of static friction than the other 2 helmet combinations (P = .013). The glossy helmet versus collegiate jersey combination produced a greater amount of static friction than the other helmet-to-jersey material combinations (P < .01). The glossy helmet versus silkscreened numbers combination produced a greater amount of static friction than the other helmet-to-jersey number combinations (P < .01). The force of static friction experienced during collisions can be clinically relevant. Conditions with higher coefficients of static friction result in greater forces. In this study, the highest coefficient of friction (glossy helmet versus silkscreened number) could increase the forces on the player's helmet by 3553.88 N when compared with other helmet-to-jersey combinations. Our results indicate that the makeup of helmet and uniform materials may affect sport safety.

Subsonic balance and pressure investigation of a 60-deg delta wing with leading-edge devices (data report)

NASA Technical Reports Server (NTRS)

Rao, D. M.; Tingas, S. A.

1981-01-01

The drag reduction potential of leading edge devices on a 60 degree delta wing at high lift was examined. Geometric variations of fences, chordwise slots, pylon type vortex generators, leading edge vortex flaps, and sharp leading edge extensions were tested individually and in specific combinations to improve high-alpha drag performance with a minimum of low-alpha drag penalty. The force, moment, and surface static pressure data for angles of attack up to 23 degrees, at Mach and Reynolds numbers of 0.16 and 3.85 x 10 to the 6th power per meter are documented.

Quasi-static and dynamic magnetic tension forces in arched, line-tied magnetic flux ropes

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

Myers, C. E.; Yamada, M.; Ji, H.

Solar eruptions are often driven by magnetohydrodynamic instabilities such as the torus and kink instabilities that act on line-tied magnetic flux ropes. We designed our recent laboratory experiments to study these eruptive instabilities which have demonstrated the key role of both dynamic (Myers et al 2015 Nature 528 526) and quasi-static (Myers et al 2016 Phys. Plasmas 23 112102) magnetic tension forces in contributing to the equilibrium and stability of line-tied magnetic flux ropes. In our paper, we synthesize these laboratory results and explore the relationship between the dynamic and quasi-static tension forces. And while the quasi-static tension force ismore » found to contribute to the flux rope equilibrium in a number of regimes, the dynamic tension force is substantial mostly in the so-called failed torus regime where magnetic self-organization events prevent the flux rope from erupting.« less

Quasi-static and dynamic magnetic tension forces in arched, line-tied magnetic flux ropes

DOE PAGES

Myers, C. E.; Yamada, M.; Ji, H.; ...

2016-11-22

Solar eruptions are often driven by magnetohydrodynamic instabilities such as the torus and kink instabilities that act on line-tied magnetic flux ropes. We designed our recent laboratory experiments to study these eruptive instabilities which have demonstrated the key role of both dynamic (Myers et al 2015 Nature 528 526) and quasi-static (Myers et al 2016 Phys. Plasmas 23 112102) magnetic tension forces in contributing to the equilibrium and stability of line-tied magnetic flux ropes. In our paper, we synthesize these laboratory results and explore the relationship between the dynamic and quasi-static tension forces. And while the quasi-static tension force ismore » found to contribute to the flux rope equilibrium in a number of regimes, the dynamic tension force is substantial mostly in the so-called failed torus regime where magnetic self-organization events prevent the flux rope from erupting.« less

A Planar Quasi-Static Constraint Mode Tire Model

DTIC Science & Technology

2015-07-10

strikes a balance between simple tire models that lack the fidelity to make accurate chassis load predictions and computationally intensive models that...strikes a balance between heuristic tire models (such as a linear point-follower) that lack the fidelity to make accurate chassis load predictions...UNCLASSIFIED: Distribution Statement A. Cleared for public release A PLANAR QUASI-STATIC CONSTRAINT MODE TIRE MODEL Rui Maa John B. Ferris

Immediate effects of cryotherapy on static and dynamic balance.

PubMed

Douglas, Matthew; Bivens, Serena; Pesterfield, Jennifer; Clemson, Nathan; Castle, Whitney; Sole, Gisela; Wassinger, Craig A

2013-02-01

Cryotherapy is commonly used in physical therapy with many known benefits; however several investigations have reported decreased functional performance following therapeutic application thereof. The purpose of this study was to determine the effect of cryotherapy applied to the ankle on static and dynamic standing balance. It was hypothesized that balance would be decreased after cryotherapy application. Twenty individuals (aged 18 to 40 years) participated in this research project. Each participant was tested under two conditions: an experimental condition where subjects received ice water immersion of the foot and ankle for 15 minutes immediately before balance testing and a control condition completed at room temperature. A Biodex® Balance System was used to quantify balance using anterior/posterior (AP), medial/lateral (ML), and overall balance indices. Paired t-tests were used to compare the balance indices for the two conditions with alpha set at 0.05 a priori. Effect size was also calculated to account for the multiple comparisons made. The static balance indices did not display statistically significant differences between the post-cryotherapy and the control conditions with low effect sizes. Dynamic ML indices significantly increased following the cryotherapy application compared to the control exhibiting a moderate effect size indicating decreased balance following cryotherapy application. No differences were noted between experimental and control conditions for the dynamic AP or overall balance indices while a small effect size was noted for both. The results suggest that cryotherapy to the ankle has a negative effect on the ML component of dynamic balance following ice water immersion. Immediate return to play following cryotherapy application is cautioned given the decreased dynamic ML balance and potential for increased injury risk. 3b Case-control study.

Hallux valgus surgery may produce early improvements in balance control: results of a cross-sectional pilot study.

PubMed

Sadra, Saba; Fleischer, Adam; Klein, Erin; Grewal, Gurtej S; Knight, Jessica; Weil, Lowell Scott; Weil, Lowell; Najafi, Bijan

2013-01-01

Hallux valgus (HV) is associated with poorer performance during gait and balance tasks and is an independent risk factor for falls in older adults. We sought to assess whether corrective HV surgery improves gait and balance. Using a cross-sectional study design, gait and static balance data were obtained from 40 adults: 19 patients with HV only (preoperative group), 10 patients who recently underwent successful HV surgery (postoperative group), and 11 control participants. Assessments were made in the clinic using body-worn sensors. Patients in the preoperative group generally demonstrated poorer static balance control compared with the other two groups. Despite similar age and body mass index, postoperative patients exhibited 29% and 63% less center of mass sway than preoperative patients during double-and single-support balance assessments, respectively (analysis of variance P =.17 and P =.14, respectively [both eyes open condition]). Overall, gait performance was similar among the groups, except for speed during gait initiation, where lower speeds were encountered in the postoperative group compared with the preoperative group (Scheffe P = .049). This study provides supportive evidence regarding the benefits of corrective lower-extremity surgery on certain aspects of balance control. Patients seem to demonstrate early improvements in static balance after corrective HV surgery, whereas gait improvements may require a longer recovery time. Further research using a longitudinal study design and a larger sample size capable of assessing the long-term effects of HV surgical correction on balance and gait is probably warranted.

Statistical mechanics framework for static granular matter.

PubMed

Henkes, Silke; Chakraborty, Bulbul

2009-06-01

The physical properties of granular materials have been extensively studied in recent years. So far, however, there exists no theoretical framework which can explain the observations in a unified manner beyond the phenomenological jamming diagram. This work focuses on the case of static granular matter, where we have constructed a statistical ensemble which mirrors equilibrium statistical mechanics. This ensemble, which is based on the conservation properties of the stress tensor, is distinct from the original Edwards ensemble and applies to packings of deformable grains. We combine it with a field theoretical analysis of the packings, where the field is the Airy stress function derived from the force and torque balance conditions. In this framework, Point J characterized by a diverging stiffness of the pressure fluctuations. Separately, we present a phenomenological mean-field theory of the jamming transition, which incorporates the mean contact number as a variable. We link both approaches in the context of the marginal rigidity picture proposed by Wyart and others.

Effects of training and detraining on the static and dynamic balance in elderly fallers and non-fallers: a pilot study.

PubMed

Toulotte, Claire; Thevenon, Andre; Fabre, Claudine

2006-01-30

The aim of this study was to evaluate the effects of training based on static and dynamic balance in single and dual task conditions in order to analyse the effects of detraining on static and dynamic balance in healthy elderly fallers and non-fallers. A group of 16 subjects were trained: eight fallers aged 71.1 +/- 5.0 years and eight non-fallers aged 68.4 +/- 4.5 years. The subjects were evaluated 3 months before the training period, 2 days before the training period, 2 days after the end of the training period and 3 months after the training period. All subjects performed a unipedal test with eyes open and eyes closed. Gait parameters were analysed under single-task and dual motor-task conditions. This study demonstrated a loss of physical capacities over 3 months for stride time, single support time for fallers in both conditions. Physical training significantly improves static and dynamic balance under single and dual task conditions. Lastly, after 3 months of detraining, a loss of the physical training effects were measured for fallers and non-fallers on the different walking parameters in the two conditions and on the unipedal tests. The absence of stimulation before the trained period shows a negative effect of ageing on walking and falls whereas training permits an improvement in static balance and the pattern of walking under single and dual task conditions, which could be due to an increase in muscular strength and a better division of attention. On the other hand, 3 months of detraining inhibited the effects of training, which showed the speed of the decline caused by 'natural' ageing.

Role of Viscous Dissipative Processes on the Wetting of Textured Surfaces

PubMed Central

Grewal, H. S.; Nam Kim, Hong; Cho, Il-Joo; Yoon, Eui-Sung

2015-01-01

We investigate the role of viscous forces on the wetting of hydrophobic, semi-hydrophobic, and hydrophilic textured surfaces as second-order effects. We show that during the initial contact, the transition from inertia- to viscous-dominant regime occurs regardless of their surface topography and chemistry. Furthermore, we demonstrate the effect of viscosity on the apparent contact angle under quasi-static conditions by modulating the ratio of a water/glycerol mixture and show the effect of viscosity, especially on the semi-hydrophobic and hydrophobic textured substrates. The reason why the viscous force does not affect the apparent contact angle of the hydrophilic surface is explained based on the relationship between the disjoining pressure and surface chemistry. We further propose a wetting model that can predict the apparent contact angle of a liquid drop on a textured substrate by incorporating a viscous force component in the force balance equation. This model can predict apparent contact angles on semi-hydrophobic and hydrophobic textured surfaces exhibiting Wenzel state more accurately than the Wenzel model, indicating the importance of viscous forces in determining the apparent contact angle. The modified model can be applied for estimating the wetting properties of arbitrary engineered surfaces. PMID:26390958

The balance effect of acupuncture therapy among stroke patients.

PubMed

Huang, Shih-Wei; Wang, Wei-Te; Yang, Tsung-Hsien; Liou, Tsan-Hon; Chen, Guan-Yu; Lin, Li-Fong

2014-08-01

To analyze how acupuncture therapy affects balance in patients experiencing their first stroke and to identify the stroke group with greatest improvement in balance after acupuncture intervention. Retrospective case-control study. Ward of a medical university hospital. A total of 629 stroke patients were enrolled initially; 345 patients met the study criteria and 132 were analyzed (66 each in the study and control groups). The study group received physiotherapy combined with acupuncture and the control group received only physiotherapy. The Postural Assessment Scale for Stroke patients (PASS) was used to evaluate balance. This balance scale system can be subdivided into static balance (PASS-MP, maintain posture) and dynamic balance (PASS-CP, change posture). This study revealed no statistically significant improvement of balance in the study group (t test). When patients with high Brunnstrom stage (Br stage) and low Br stage were analyzed separately, once again no statistical difference was detected between the study and control groups of those with high Br stage. However, among low-Br stage patients, the study group showed significant improvement in static balance (mean PASS-MP score±standard deviation: 4.7±3.7) compared with the control group (PASS-MP score: 2.8±2.7) (p<0.05). In first-ever stroke patients with a low Br stage, acupuncture therapy can improve static balance during rehabilitation. However, the effect on balance was limited among high-Br stage patients. This study provides information valuable to patients with hemiplegic stroke because it suggests that acupuncture can be used to improve balance. A prospective double-blind, randomized, controlled study design is recommended for future studies in patients with hemiplegic stroke.

Use of a Mobile Application to Help Students Develop Skills Needed in Solving Force Equilibrium Problems

ERIC Educational Resources Information Center

Yang, Eunice

2016-01-01

This paper discusses the use of a free mobile engineering application (app) called Autodesk® ForceEffect™ to provide students assistance with spatial visualization of forces and more practice in solving/visualizing statics problems compared to the traditional pencil-and-paper method. ForceEffect analyzes static rigid-body systems using free-body…

Regulation of the basement membrane by epithelia generated forces

NASA Astrophysics Data System (ADS)

Tanner, Kandice

2012-12-01

Tumor metastasis involves a progressive loss of tissue architecture and dissolution of structural boundaries between the epithelium and connective tissue. The basement membrane (BM), a specialized network of extracellular matrix proteins forms a barrier that physically restricts pre-invasive lesions such that they remain as local insults. The BM is not a static structure, but one that is constantly regenerated and remodeled in the adult organism. Matrix organization also regulates cell function. Thus alterations in the balance of synthesis, remodeling and proteolytic degradation of the extracellular matrix proteins may contribute to a loss of structural integrity. However, the de novo assembly and maintenance of the complex structural properties of in vivo basement membranes remain elusive. Here, this paper highlights the current understanding on the structural properties and the establishment of the BM, and discusses the potential role of self-generated forces in adult tissue remodeling and the maintenance of the BM as a malignancy suppressor.

Mental imagery. Effects on static balance and attentional demands of the elderly.

PubMed

Hamel, M F; Lajoie, Yves

2005-06-01

Several studies have demonstrated the effectiveness of mental imagery in improving motor performance. However, no research has studied the effectiveness of such a technique on static balance in the elderly. This study evaluated the efficiency of a mental imagery technique, aimed at improving static balance by reducing postural oscillations and attentional demands in the elderly. Twenty subjects aged 65 to 90 years old, divided into two groups (8 in Control group and 12 in Experimental group) participated in the study. The experimental participants underwent daily mental imagery training for a period of six weeks. Antero-posterior and lateral oscillations, reaction times during the use of the double-task paradigm were measured, and the Berg Balance Scale, Activities-specific Balance Confidence Scale, and VMIQ questionnaire were answered during both pre-test and post-test. Attentional demands and postural oscillations (antero-posterior) decreased significantly in the group with mental imagery training compared with those of the Control group. Subjects in the mental imagery group became significantly better in their aptitudes to generate clear vivid mental images, as indicated by the VMIQ questionnaire, whereas no significant difference was observed for the Activities-specific Balance Confidence Scale or Berg Scale. The results support psychoneuromuscular and motor coding theories associated with mental imagery.

Effect of Virtual Reality on Postural and Balance Control in Patients with Stroke: A Systematic Literature Review.

PubMed

Chen, Ling; Lo, Wai Leung Ambrose; Mao, Yu Rong; Ding, Ming Hui; Lin, Qiang; Li, Hai; Zhao, Jiang Li; Xu, Zhi Qin; Bian, Rui Hao; Huang, Dong Feng

2016-01-01

Objective . To critically evaluate the studies that were conducted over the past 10 years and to assess the impact of virtual reality on static and dynamic balance control in the stroke population. Method . A systematic review of randomized controlled trials published between January 2006 and December 2015 was conducted. Databases searched were PubMed, Scopus, and Web of Science. Studies must have involved adult patients with stroke during acute, subacute, or chronic phase. All included studies must have assessed the impact of virtual reality programme on either static or dynamic balance ability and compared it with a control group. The Physiotherapy Evidence Database (PEDro) scale was used to assess the methodological quality of the included studies. Results . Nine studies were included in this systematic review. The PEDro scores ranged from 4 to 9 points. All studies, except one, showed significant improvement in static or dynamic balance outcomes group. Conclusions . This review provided moderate evidence to support the fact that virtual reality training is an effective adjunct to standard rehabilitation programme to improve balance for patients with chronic stroke. The effect of VR training in balance recovery is less clear in patients with acute or subacute stroke. Further research is required to investigate the optimum training intensity and frequency to achieve the desired outcome.

Smooth-pursuit eye movements without head movement disrupt the static body balance.

PubMed

Kim, Sang-Yeob; Moon, Byeong-Yeon; Cho, Hyun Gug

2016-04-01

[Purpose] To investigate the changes of body balance in static posture in smooth-pursuit eye movements (SPEMs) without head movement. [Subjects and Methods] Forty subjects (24 males, 16 females) aged 23.24 ± 2.58 years participated. SPEMs were activated in three directions (horizontal, vertical, and diagonal movements); the target speed was set at three conditions (10°/s, 20°/s, and 30°/s); and the binocular visual field was limited to 50°. To compare the body balance changes, the general stability (ST) and the fall risk index (FI) were measured with TETRAX. The subjects wore a head-neck collar and stood on a balance plate for 32 s during each measurement in three directions. SPEMs were induced to each subject with nine target speeds and directions. All measured values were compared with those in stationary fixation. [Results] The ST and FI increased significantly in all SPEMs directions, with an increased target speed than that in stationary fixation. In the same condition of the target speed, the FI had the highest value relative to diagonal SPEMs. [Conclusion] SPEMs without head movement disrupt the stability of body balance in a static posture, and diagonal SPEMs may have a more negative effect in maintaining body balance than horizontal or vertical SPEMs.

The effect of spinal curvature on the photogrammetric assessment on static balance in elderly women.

PubMed

Drzał-Grabiec, Justyna; Rachwał, Maciej; Podgórska-Bednarz, Justyna; Rykała, Justyna; Snela, Sławomir; Truszczyńska, Aleksandra; Trzaskoma, Zbigniew

2014-05-29

Involutional changes to the body in elderly patients affect the shape of the spine and the activity of postural muscles. The purpose of this study was to assess the influence of age-related changes in spinal curvature on postural balance in elderly women. The study population consisted of 90 women, with a mean age of 70 ± 8.01 years. Static balance assessments were conducted on a tensometric platform, and posturographic assessments of body posture were performed using a photogrammetric method based on the Projection Moiré method. The results obtained were analysed using the Spearman's rank correlation coefficient test. We found a statistically significant correlation between body posture and the quality of the balance system response based on the corrective function of the visual system. The shape of the spinal curvature influenced postural stability, as measured by static posturography. Improvement in the quality of the balance system response depended on corrective information from the visual system and proprioceptive information from the paraspinal muscles. The sensitivity of the balance system to the change of centre of pressure location was influenced by the direction of the change in rotation of the shoulder girdle and spine. Development of spinal curvature in the sagittal plane and maintenance of symmetry in the coronal and transverse planes are essential for correct balance control, which in turn is essential for the development of a properly proportioned locomotor system.

Effects of Combining Running and Practical Duration Stretching on Proprioceptive Skills of National Sprinters.

PubMed

Romero-Franco, Natalia; Párraga-Montilla, Juan Antonio; Molina-Flores, Enrique M; Jiménez-Reyes, Pedro

2018-06-01

Romero-Franco, N, Párraga-Montilla, JA, Molina-Flores, EM, and Jiménez-Reyes, P. Effects of combining running and practical duration stretching on proprioceptive skills of national sprinters. J Strength Cond Res XX(X): 000-000, 2018-Practical duration stretching after aerobic activities is a recommended component of the first part of warm-up because of its effects on performance. However, its effects on proprioceptive skills are unknown. This study aimed to analyze the effects of running and practical duration static stretching (SS) and dynamic stretching (DS) on postural balance and the joint position sense (JPS) of national sprinters. Thirty-two national sprinters were randomly classified into a SS group (n = 11), DS group (n = 11), or control group (n = 10). Static stretching performed 5 minutes of running and short-duration (20 seconds) static stretches; DS performed 5 minutes of running and short-duration dynamic (20 seconds) stretches; and the control group performed 5 minutes of running. Before and after the intervention, unipedal static postural balance and knee JPS were evaluated. Static stretching exhibited a more centralized center of pressure in the medial-lateral plane for unipedal static postural balance in right-leg support after stretching (p = 0.005, d = 1.24), whereas DS showed values further from the center after stretching for the same unipedal support compared with baseline (p = 0.042, d = 0.49), and the control group remained stable (p > 0.05). Joint position sense did not show significant differences in any group (p > 0.05). In conclusion, combining running and practical duration SS may be beneficial for right-leg postural stabilization, whereas DS may be partly and slightly deleterious. Both SS and DS combined with running and running alone have neutral effects on knee JPS. Sports professionals should consider running and practical duration SS as part of the warm-up of sprinters to partly improve unipedal static postural balance.

Force fluctuations while pressing and moving against high- and low-friction touch screen surfaces.

PubMed

Joshi, Mukta N; Keenan, Kevin G

2016-07-01

The purpose of this study was to identify the influence of a high- and low-friction surface on the ability to maintain a steady downward force during an index finger pressing and moving task. Fifteen right-handed subjects (24-48 years) performed a static force pressing task and a hybrid pressing and moving task on the surface of an iPad mini while holding a steady 2-N force on high- and low-friction surfaces. Variability of force was quantified as the standard deviation (SD) of normal force (F z) and shear force (F xy) across friction conditions and tasks. The SD of F z was 227 % greater during the hybrid task as compared to the static task (p < .001) and was 19 % greater for the high- versus low-friction condition (p = .033). There were positive correlations between SD of F z and F xy during the hybrid force/motion tasks on the high- and low-friction conditions (r (2) = 0.5 and 0.86, respectively), suggesting significant associations between normal and shear forces for this hybrid task. The correlation between the SD of F z for static and hybrid tasks was r (2) = 0.44, indicating that the common practice of examining the control of static tasks may not sufficiently explain performance during hybrid tasks, at least for the young subjects tested in the current study. As activities of daily living frequently require hybrid force/motion tasks (e.g., writing, doing the dishes, and cleaning counters), the results of this study emphasize the need to study motor performance during hybrid tasks in addition to static force tasks.

The effect of arm sling on balance in patients with hemiplegia.

PubMed

Acar, Merve; Karatas, Gulcin Kaymak

2010-10-01

The aim of this study was to investigate the effect of an arm sling on balance in patients with, hemiplegia following a stroke. Twenty-six patients with hemiplegia (11 men, 15 women) who had, shoulder subluxation were enrolled in the study. Balance was evaluated by the Berg Balance Scale, the, Functional Reach test, and a static balance index which was measured by the Kinesthetic Ability, Trainer 3000. Balance tests were performed twice, with arm sling and without arm sling use. Results of, this study show that the Berg Balance Scores and static balance index ameliorated with arm sling use (p=0.005 and p=0.004, respectively). Likewise, the Functional Reach test was better when performed with an arm sling (p=0.039). In conclusion, arm slings have a beneficial effect on balance in patients, with hemiplegia. An arm sling may be applied for its possible beneficial effect on balance especially in, the early phases of stroke rehabilitation while the upper extremity is still flaccid and arm swing is, reduced. Copyright © 2010 Elsevier B.V. All rights reserved.

Impairments in static standing balance are highly prevalent among older adults receiving home-based physical therapy.

PubMed

Bohannon, Richard W

2012-01-01

Measures of balance are an important component of the physical therapist examination. This study investigated the usefulness of timed static stance durations for identifying balance impairments among patients receiving home-based physical therapy. This study involved the retrospective retrieval of data from the records of 48 patients at least 60 years of age. Their balance was measured under 3 foot configurations; that is, feet apart, feet together, and on each foot. Every patient demonstrated impaired standing balance. Most, but not all could balance 30 seconds with the feet apart or together. Only 19 could maintain balance on each of both feet. Of those who could so balance, none was able to achieve the average time of normal individuals of comparable age. Although not able to identify all aspects of balance, timed durations of stance under different configurations demonstrate a high prevalence of balance impairments among patients receiving home-based physical therapy. As the tests are objective, fast, and require little space, they can be advocated in such a setting.

Balance and mobility dysfunction and falls risk in older people with mild to moderate Alzheimer disease.

PubMed

Suttanon, Plaiwan; Hill, Keith D; Said, Catherine M; Logiudice, Dina; Lautenschlager, Nicola T; Dodd, Karen J

2012-01-01

This study aimed to identify the magnitude and type of balance and mobility impairments in people with Alzheimer disease by comparing their performance with that of older people without cognitive impairment. Twenty-five community-dwelling people with mild to moderate Alzheimer disease and a comparison group of 25 cognitively intact age- and sex-matched people completed a comprehensive balance and mobility assessment. This included computerized posturography measures of static and dynamic balance under various conditions, clinical balance, and mobility measures, and measures of falls and falls risk. The level of falls risk was higher in people with Alzheimer disease. Standing balance in people with Alzheimer disease was significantly impaired across a range of static and dynamic balance conditions. Activity level, gait, and mobility measures were also impaired, particularly turning and dual tasks. The findings of the study highlight the value of including balance screening as a routine component of early dementia assessment. This would allow for the early detection of balance dysfunction and the introduction of balance retraining before impairments progress to more advanced levels.

Specific sine-Gordon soliton dynamics in the presence of external driving forces

NASA Astrophysics Data System (ADS)

Reinisch, Gilbert; Fernandez, Jean Claude

1981-07-01

We consider the acceleration of a single sine-Gordon (SG) soliton kink wave by an external time-dependent force χ(t), first without any dissipation, and then in the presence of a weak damping effect. We use the method of Fogel, Trullinger, Bishop, and Krumhansl [FTBK,

Balance outcomes following a tap dance program for a child with congenital myotonic muscular dystrophy.

PubMed

Biricocchi, Charlanne; Drake, JaimeLynn; Svien, Lana

2014-01-01

This case report describes the effects of a 6-week progressive tap dance program on static and dynamic balance for a child with type 1 congenital myotonic muscular dystrophy (congenital MMD1). A 6-year-old girl with congenital MMD1 participated in a 1-hour progressive tap dance program. Classes were held once a week for 6 consecutive weeks and included 3 children with adaptive needs and 1 peer with typical development. The Bruininks-Oseretsky Test of Motor Proficiency, second edition (BOT-2) balance subsection and the Pediatric Balance Scale were completed at the beginning of the first class and the sixth class. The participant's BOT-2 score improved from 3 to 14. Her Pediatric Balance Scale score did not change. Participation in a progressive tap dance class by a child with congenital MMD1 may facilitate improvements in static and dynamic balance.

Specific balance training included in an endurance-resistance exercise program improves postural balance in elderly patients undergoing haemodialysis.

PubMed

Frih, Bechir; Mkacher, Wajdi; Jaafar, Hamdi; Frih, Ameur; Ben Salah, Zohra; El May, Mezry; Hammami, Mohamed

2018-04-01

The purpose of this study was to evaluate the effects of 6 months of specific balance training included in endurance-resistance program on postural balance in haemodialysis (HD) patients. Forty-nine male patients undergoing HD were randomly assigned to an intervention group (balance training included in an endurance-resistance training, n = 26) or a control group (resistance-endurance training only, n = 23). Postural control was assessed using six clinical tests; Timed Up and Go test, Tinetti Mobility Test, Berg Balance Scale, Unipodal Stance test, Mini-Balance Evaluation Systems Test and Activities Balance Confidence scale. All balance measures increased significantly after the period of rehabilitation training in the intervention group. Only the Timed Up and Go, Berg Balance Scale, Mini-Balance Evaluation Systems Test and Activities Balance Confidence scores were improved in the control group. The ranges of change in these tests were greater in the balance training group. In HD patients, specific balance training included in a usual endurance-resistance training program improves static and dynamic balance better than endurance-resistance training only. Implications for rehabilitation Rehabilitation using exercise in haemodialysis patients improved global mobility and functional abilities. Specific balance training included in usual endurance resistance training program could lead to improved static and dynamic balance.

Stick-slip chaos in a mechanical oscillator with dry friction

NASA Astrophysics Data System (ADS)

Kousaka, Takuji; Asahara, Hiroyuki; Inaba, Naohiko

2018-03-01

This study analyzes a forced mechanical dynamical system with dry friction that can generate chaotic stick-slip vibrations. We find that the dynamics proposed by Yoshitake et al. [Trans. Jpn. Soc. Mech. Eng. C 61, 768 (1995)] can be expressed as a nonautonomous constraint differential equation owing to the static friction force. The object is constrained to the surface of a moving belt by a static friction force from when it sticks to the surface until the force on the object exceeds the maximal static friction force. We derive a 1D Poincaré return map from the constrained mechanical system, and prove numerically that this 1D map has an absolutely continuous invariant measure and a positive Lyapunov exponent, providing strong evidence for chaos.

Observing the Forces Involved in Static Friction under Static Situations

ERIC Educational Resources Information Center

Kaplan, Daniel

2013-01-01

Static friction is an important concept in introductory physics. Later in the year students apply their understanding of static friction under more complex conditions of static equilibrium. Traditional lab demonstrations in this case involve exceeding of the maximum level of static friction, resulting in the "onset of motion." (Contains…

Differential Effect of Taekwondo Training on Knee Muscle Strength and Reactive and Static Balance Control in Children with Developmental Coordination Disorder: A Randomized Controlled Trial

ERIC Educational Resources Information Center

Fong, Shirley S. M.; Chung, Joanne W. Y.; Chow, Lina P. Y.; Ma, Ada W. W.; Tsang, William W. N.

2013-01-01

This randomized controlled trial aimed to investigate the effect of short-term intensive TKD training on the isokinetic knee muscle strength and reactive and static balance control of children with developmental coordination disorder (DCD). Among the 44 children with DCD (mean age: 7.6 plus or minus 1.3 years) recruited, 21 were randomly assigned…

The Indeterminate Case of Classical Static Friction When Coupled with Tension

NASA Astrophysics Data System (ADS)

Hahn, Kenneth D.; Russell, Jacob M.

2018-02-01

It has been noted that the static friction force poses challenges for students and, at times, even their instructors. Unlike the gravitational force, which has a precise and unambiguous magnitude (FG = mg), the magnitude and direction of the static friction force depend on other forces at play. Friction can be understood rather well in terms of complicated atomic-scale interactions between surfaces. Ringlein and Robbins survey aspects of the atomic origins of friction, and Folkerts explores factors that affect the value of static friction. However, what students typically encounter in an introductory course ignores the atomic origins of friction (beyond perhaps a brief overview of the atomic model). The rules of dry friction (i.e., non-lubricated surfaces in contact) taught in introductory physics were originally published in 1699 by Guillaume Amontons. Amontons's first law states that the force of friction is directly proportional to the applied load, i.e., f = μFN, where FN is the normal force and μ is the coefficient of friction. His second law states that the force of friction is independent of the macroscopic area of contact. These laws were verified by Coulomb in 1781.

Statically vs dynamically balanced gait: Analysis of a robotic exoskeleton compared with a human.

PubMed

Barbareschi, Giulia; Richards, Rosie; Thornton, Matt; Carlson, Tom; Holloway, Catherine

2015-01-01

In recent years exoskeletons able to replicate human gait have begun to attract growing popularity for both assistive and rehabilitative purposes. Although wearable robots often need the use of external support in order to maintain stability, the REX exoskeleton by REX Bionics is able to self-balance through the whole cycle. However this statically balanced gait presents important differences with the dynamically balanced gait of human subjects. This paper will examine kinematic and kinetic differences between the gait analysis performed on a subject wearing the REX exoskeleton and human gait analysis data as presented in literature. We will also provide an insight on the impact that these differences can have for both rehabilitative and assistive applications.

The Influence of Friction Between Football Helmet and Jersey Materials on Force: A Consideration for Sport Safety

PubMed Central

Rossi, Anthony M.; Claiborne, Tina L.; Thompson, Gregory B.; Todaro, Stacey

2016-01-01

Context: The pocketing effect of helmet padding helps to dissipate forces experienced by the head, but if the player's helmet remains stationary in an opponent's shoulder pads, the compressive force on the cervical spine may increase. Objective: To (1) measure the coefficient of static friction between different football helmet finishes and football jersey fabrics and (2) calculate the potential amount of force on a player's helmet due to the amount of friction present. Design: Cross-sectional study. Setting: Laboratory. Patients or Other Participants: Helmets with different finishes and different football jersey fabrics. Main Outcome Measure(s): The coefficient of friction was determined for 2 helmet samples (glossy and matte), 3 football jerseys (collegiate, high school, and youth), and 3 types of jersey numbers (silkscreened, sublimated, and stitched on) using the TAPPI T 815 standard method. These measurements determined which helmet-to-helmet, helmet-to-jersey number, and helmet-to-jersey material combination resulted in the least amount of static friction. Results: The glossy helmet versus glossy helmet combination produced a greater amount of static friction than the other 2 helmet combinations (P = .013). The glossy helmet versus collegiate jersey combination produced a greater amount of static friction than the other helmet-to-jersey material combinations (P < .01). The glossy helmet versus silkscreened numbers combination produced a greater amount of static friction than the other helmet-to-jersey number combinations (P < .01). Conclusions: The force of static friction experienced during collisions can be clinically relevant. Conditions with higher coefficients of static friction result in greater forces. In this study, the highest coefficient of friction (glossy helmet versus silkscreened number) could increase the forces on the player's helmet by 3553.88 N when compared with other helmet-to-jersey combinations. Our results indicate that the makeup of helmet and uniform materials may affect sport safety. PMID:27824251

Effects of ballates, step aerobics, and walking on balance in women aged 50-75 years.

PubMed

Clary, Sarah; Barnes, Cathleen; Bemben, Debra; Knehans, Allen; Bemben, Michael

2006-01-01

This study examined the effectiveness of Ballates training (strengthening of the central core musculature by the inception of balance techniques) compared to more traditional exercise programs, such as step aerobics and walking, on balance in women aged 50- 75 years. Participants were randomly assigned to one of three supervised training groups (1 hour/day, 3 days/week, 13 weeks), Ballates (n = 12), step aerobics (n = 17), or walking (n =15). Balance was measured by four different methods (modified Clinical Test for the Sensory Interaction on Balance - mCTSIB; Unilateral Stance with Eyes Open - US-EO or Eyes Closed - US-EC; Tandem Walk - TW; Step Quick Turn - SQT) using the NeuroCom Balance Master. A 2-way (Group and Trial) repeated measures ANOVA and post-hoc Bonferroni Pair-wise Comparisons were used to evaluate changes in the dependent variables used to describe stability and balance (sway velocity, turn sway, speed, and turn time). Measures of static postural stability and dynamic balance were similar for the three groups prior to training. Following the different exercise interventions, sway velocity on firm and foam surfaces (mCTSIB) with eyes closed (p < 0.05) increased for the Ballates group while the other two exercise groups either maintained or decreased their sway velocity following the training, therefore suggesting that these two groups either maintained or improved their balance. There were significant improvements in speed during the TW test (p < 0.01), and turn time (p < 0.01) and sway (p < 0.05) during the SQT test for each of the three groups. In general, all three training programs improved dynamic balance, however, step aerobics and walking programs resulted in be better improvements in postural stability or static balance when compared to the Ballates program. Key PointsExercise training can improve balanceNeed to consider both static and dynamic aspects of balance individuallyImproved balance can reduce the risk of fall.

Variable camber wing based on pneumatic artificial muscles

NASA Astrophysics Data System (ADS)

Yin, Weilong; Liu, Libo; Chen, Yijin; Leng, Jinsong

2009-07-01

As a novel bionic actuator, pneumatic artificial muscle has high power to weight ratio. In this paper, a variable camber wing with the pneumatic artificial muscle is developed. Firstly, the experimental setup to measure the static output force of pneumatic artificial muscle is designed. The relationship between the static output force and the air pressure is investigated. Experimental result shows the static output force of pneumatic artificial muscle decreases nonlinearly with increasing contraction ratio. Secondly, the finite element model of the variable camber wing is developed. Numerical results show that the tip displacement of the trailing-edge increases linearly with increasing external load and limited with the maximum static output force of pneumatic artificial muscles. Finally, the variable camber wing model is manufactured to validate the variable camber concept. Experimental result shows that the wing camber increases with increasing air pressure and that it compare very well with the FEM result.

24. "GAFFTC 29 SEP 60, F106B STATIC TEST 1." Test ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

24. "G-AFFTC 29 SEP 60, F-106B STATIC TEST 1." Test of the Convair sled escape system at static test site east of Station "50". File no. 11,988-60. - Edwards Air Force Base, South Base Sled Track, Edwards Air Force Base, North of Avenue B, between 100th & 140th Streets East, Lancaster, Los Angeles County, CA

A Comparative Study of the Effects of Pilates and Latin Dance on Static and Dynamic Balance in Older Adults.

PubMed

Sofianidis, George; Dimitriou, Anna-Maria; Hatzitaki, Vassilia

2017-07-01

The present study was designed to compare the effectiveness of exercise programs with Pilates and Latin dance on older adults' static and dynamic balance. Thirty-two older adults were divided into three groups: Pilates group, Dance group, and Control group. Static and dynamic balance was assessed with following tasks: (a) tandem stance, (b) one-leg stance, and (c) periodic sway with and without metronome guidance. Analysis revealed a significant reduction of the trunk sway amplitude during the tandem stance with eyes closed, reduction in the center of pressure (CoP) displacement during one-leg stance, and increase in the amplitude of trunk oscillation during the sway task for both intervention groups, and reduction in the standard deviation of the CoP displacement during the metronome paced task only for the dance group. The differences in specific balance indices between the two programs suggest some specific adaptations that may provide useful knowledge for the selection of exercises that are better tailored to the needs of the old adult.

The effect of combined mechanism ankle support on postural control of patients with chronic ankle instability.

PubMed

Hadadi, Mohammad; Ebrahimi, Ismaeil; Mousavi, Mohammad Ebrahim; Aminian, Gholamreza; Esteki, Ali; Rahgozar, Mehdi

2017-02-01

Chronic ankle instability is associated with neuromechanical changes and poor postural stability. Despite variety of mechanisms of foot and ankle orthoses, almost none apply comprehensive mechanisms to improve postural control in all subgroups of chronic ankle instability patients. The purpose of this study was to investigate the effect of an ankle support implementing combined mechanisms to improve postural control in chronic ankle instability patients. Cross-sectional study. An ankle support with combined mechanism was designed based on most effective action mechanisms of foot and ankle orthoses. The effect of this orthosis on postural control was evaluated in 20 participants with chronic ankle instability and 20 matched healthy participants. The single-limb stance balance test was measured in both groups with and without the new orthosis using a force platform. The results showed that application of combined mechanism ankle support significantly improved all postural sway parameters in chronic ankle instability patients. There were no differences in means of investigated parameters with and without the orthosis in the healthy group. No statistically significant differences were found in postural sway between chronic ankle instability patients and healthy participants after applying the combined mechanism ankle support. The combined mechanism ankle support is effective in improving static postural control of chronic ankle instability patients to close to the postural sway of healthy individual. the orthosis had no adverse effects on balance performance of healthy individuals. Clinical relevance Application of the combined mechanism ankle support for patients with chronic ankle instability is effective in improving static balance. This may be helpful in reduction of recurrence of ankle sprain although further research about dynamic conditions is needed.

Results of an investigation of hypersonic viscous interaction effects of the space shuttle orbiter using a 0.010 scale model (51-0) in the AEDC-VKF tunnel F (OA160)

NASA Technical Reports Server (NTRS)

Elder, D. J.

1975-01-01

An experimental aerodynamic investigation was conducted in the AEDC-VKF Hypervelocity Wind Tunnel (Tunnel F) at a nomial Mach number of 19 to determine hypersonic viscous interaction effects on the space shuttle orbiter. The tests were conducted at an angle of attack of 30 degrees over a free-stream Reynolds number (based on fuselage length) variation from 0.1 to 0.4 million. Viscous interaction parameter was varied from 0.02 to 0.06. Six component static stability force and moment data were measured by an internally compensated internal strain gage balance. Resulting data are presented.

Functional Brace in ACL Surgery: Force Quantification in an In Vivo Study

PubMed Central

LaPrade, Robert F.; Venderley, Melanie B.; Dahl, Kimi D.; Dornan, Grant J.; Turnbull, Travis Lee

2017-01-01

Background: A need exists for a functional anterior cruciate ligament (ACL) brace that dynamically supports the knee joint to match the angle-dependent forces of a native ACL, especially in the early postoperative period. Purpose/Hypothesis: The purpose of this study was to quantify the posteriorly directed external forces applied to the anterior proximal tibia by both a static and a dynamic force ACL brace. The proximal strap forces applied by the static force brace were hypothesized to remain relatively constant regardless of knee flexion angle compared with those of the dynamic force brace. Study Design: Controlled laboratory study. Methods: Seven healthy adult males (mean age, 27.4 ± 3.4 years; mean height, 1.8 ± 0.1 m; mean body mass, 84.1 ± 11.3 kg) were fitted with both a static and a dynamic force ACL brace. Participants completed 3 functional activities: unloaded extension, sit-to-stand, and stair ascent. Kinematic data were collected using traditional motion-capture techniques while posteriorly directed forces applied to the anterior aspect of both the proximal and distal tibia were simultaneously collected using a customized pressure-mapping technique. Results: The mean posteriorly directed forces applied to the proximal tibia at 30° of flexion by the dynamic force brace during unloaded extension (80.2 N), sit-to-stand (57.5 N), and stair ascent (56.3 N) activities were significantly larger, regardless of force setting, than those applied by the static force brace (10.1 N, 9.5 N, and 11.9 N, respectively; P < .001). Conclusion: The dynamic force ACL brace, compared with the static force brace, applied significantly larger posteriorly directed forces to the anterior proximal tibia in extension, where the ACL is known to experience larger in vivo forces. Further studies are required to determine whether the physiological behavior of the brace will reduce anterior knee laxity and improve long-term patient outcomes. Clinical Relevance: ACL braces that dynamically restrain the proximal tibia in a manner similar to physiological ACL function may improve pre- and postoperative treatment. PMID:28748195

Aerodynamic characteristics of the National Launch System (NLS) 1 1/2 stage launch vehicle

NASA Technical Reports Server (NTRS)

Springer, A. M.; Pokora, D. C.

1994-01-01

The National Aeronautics and Space Administration (NASA) is studying ways of assuring more reliable and cost effective means to space. One launch system studied was the NLS which included the l l/2 stage vehicle. This document encompasses the aerodynamic characteristics of the 1 l/2 stage vehicle. To support the detailed configuration definition two wind tunnel tests were conducted in the NASA Marshall Space Flight Center's 14x14-Inch Trisonic Wind Tunnel during 1992. The tests were a static stability and a pressure test, each utilizing 0.004 scale models. The static stability test resulted in the forces and moments acting on the vehicle. The aerodynamics for the reference configuration with and without feedlines and an evaluation of three proposed engine shroud configurations were also determined. The pressure test resulted in pressure distributions over the reference vehicle with and without feedlines including the reference engine shrouds. These pressure distributions were integrated and balanced to the static stability coefficients resulting in distributed aerodynamic loads on the vehicle. The wind tunnel tests covered a Mach range of 0.60 to 4.96. These ascent flight aerodynamic characteristics provide the basis for trajectory and performance analysis, loads determination, and guidance and control evaluation.

Static Postural Control in Youth With Osteogenesis Imperfecta Type I.

PubMed

Pouliot-Laforte, Annie; Lemay, Martin; Rauch, Frank; Veilleux, Louis-Nicolas

2017-10-01

To assess static postural control in eyes-open and eyes-closed conditions in individuals with osteogenesis imperfecta (OI) type I as compared with typically developing (TD) individuals and to explore the relation between postural control and lower limb muscle function. Cross-sectional study. Outpatient department of a pediatric orthopedic hospital. A convenience sample (N=38) of individuals with OI type I (n=22; mean age, 13.1y; range, 6-21y) and TD individuals (n=16; mean age, 13.1y; range, 6-20y) was selected. Participants were eligible if they were between 6 and 21 years and if they did not have any fracture or surgery in the lower limb in the 12 months before testing. Not applicable. Postural control was assessed through static balance tests and muscle function through mechanographic tests on a force platform. Selected postural parameters were path length, velocity, 90% confidence ellipse area, and the ellipse's length of the mediolateral and anteroposterior axes. Mechanographic parameters were peak force and peak power as measured using the multiple two-legged hopping and the single two-legged jump test, respectively. Individuals with OI type I had poorer postural control than did TD individuals as indicated by longer and faster displacements and a larger ellipse area. Muscle function was unrelated to postural control in the OI group. Removing visual information resulted in a larger increase in postural control parameters in the OI group than in the TD group. A proprioceptive deficit could explain poorer postural control in individuals with OI type I. Copyright © 2017 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

[Reliability of static posturography in elderly persons].

PubMed

Bauer, C M; Gröger, I; Rupprecht, R; Tibesku, C O; Gassmann, K G

2010-08-01

Static posturography is used to quantify body sway. It is used to assess the balance of elderly persons who are prone to falls. There is still no general opinion concerning the reliability of force platform measurements. The aim of this study was to test the reliability of force platform parameters when measuring elderly persons. The reliability of 11 force platform parameters was tested measuring 30 elderly persons. The following parameters were calculated: mean speed of center of pressure displacement in mm/s, length of sway in mm, sway area in mm(2), amplitudes of center of pressure movement, the axis of oscillation in degrees and the person's angles of inclination in degrees. Three measurements were taken on the same day, with a resting period of 2 min. Four different test conditions were used: normal standing and narrow stand with eyes open and eyes closed, respectively. Reliability was determined by using intraclass correlation coefficients. Six parameters had excellent reliability with a correlation coefficient of >0.9: mean speed of center of pressure movement during narrow stand, area of sway during narrow stand, length of sway during normal and narrow stand, and the angle of inclination in the sagittal plane during normal stand and narrow stand. The condition "narrow stand eyes closed" proved to be the most reliable test position. Six parameters proved to have excellent reliability and are recommended to be used in further investigations. Narrow stand with eyes closed should be used as the test position. The tested protocol proved to be reliable. Whether these parameters can be used to predict falls in elderly persons remains to be investigated.

Investigation into the Effects of Eight Weeks of Step Aerobic Dance Practice on Static Balance, Flexibility and Selected Basketball Skills in Young Basketball Players

ERIC Educational Resources Information Center

Bavli, Özhan

2016-01-01

The aim of this study was to investigate the effects of eight weeks of step aerobic exercises on static balance, flexibility and selected basketball skills in young basketball players. A total of 20 basketball players (average age 16.1 ± 0.7 years and average sporting age 4.1 ± 0.7 years) voluntarily joined the study. Participants were randomly…

The effect of single-task and dual-task balance exercise programs on balance performance in adults with osteoporosis: a randomized controlled preliminary trial.

PubMed

Konak, H E; Kibar, S; Ergin, E S

2016-11-01

Osteoporosis is a serious disease characterized by muscle weakness in the lower extremities, shortened length of trunk, and increased dorsal kyphosis leading to poor balance performance. Although balance impairment increases in adults with osteoporosis, falls and fall-related injuries have been shown to occur mainly during the dual-task performance. Several studies have shown that dual-task performance was improved with specific repetitive dual-task exercises. The aims of this study were to compare the effect of single- and dual-task balance exercise programs on static balance, dynamic balance, and activity-specific balance confidence in adults with osteoporosis and to assess the effectiveness of dual-task balance training on gait speed under dual-task conditions. Older adults (N = 42) (age range, 45-88 years) with osteoporosis were randomly assigned into two groups. Single-task balance training group was given single-task balance exercises for 4 weeks, whereas dual-task balance training group received dual-task balance exercises. Participants received 45-min individualized training session, three times a week. Static balance was evaluated by one-leg stance (OLS) and a kinesthetic ability trainer (KAT) device. Dynamic balance was measured by the Berg Balance Scale (BBS), Time Up and Go (TUG) test, and gait speed. Self-confidence was assessed with the Activities-specific Balance Confidence (ABC-6) scale. Assessments were performed at baseline and after the 4-week program. At the end of the treatment periods, KAT score, BBS score, time in OLS and TUG, gait speeds under single- and dual-task conditions, and ABC-6 scale scores improved significantly in all patients (p < 0.05). However, BBS and gait speeds under single- and dual-task conditions showed significantly greater improvement in the dual-task balance training group than in the single-task balance training group (p < 0.05). ABC-6 scale scores improved more in the single-task balance training group than in the dual-task balance training group (p < 0.05). A 4-week single- and dual-task balance exercise programs are effective in improving static balance, dynamic balance, and balance confidence during daily activities in older adults with osteoporosis. However, single- and dual-task gait speeds showed greater improvement following the application of a specific type of dual-task exercise programs. 24102014-2.

Effect of Virtual Reality on Postural and Balance Control in Patients with Stroke: A Systematic Literature Review

PubMed Central

Chen, Ling; Ding, Ming Hui; Lin, Qiang; Li, Hai; Zhao, Jiang Li; Xu, Zhi Qin; Bian, Rui Hao

2016-01-01

Objective. To critically evaluate the studies that were conducted over the past 10 years and to assess the impact of virtual reality on static and dynamic balance control in the stroke population. Method. A systematic review of randomized controlled trials published between January 2006 and December 2015 was conducted. Databases searched were PubMed, Scopus, and Web of Science. Studies must have involved adult patients with stroke during acute, subacute, or chronic phase. All included studies must have assessed the impact of virtual reality programme on either static or dynamic balance ability and compared it with a control group. The Physiotherapy Evidence Database (PEDro) scale was used to assess the methodological quality of the included studies. Results. Nine studies were included in this systematic review. The PEDro scores ranged from 4 to 9 points. All studies, except one, showed significant improvement in static or dynamic balance outcomes group. Conclusions. This review provided moderate evidence to support the fact that virtual reality training is an effective adjunct to standard rehabilitation programme to improve balance for patients with chronic stroke. The effect of VR training in balance recovery is less clear in patients with acute or subacute stroke. Further research is required to investigate the optimum training intensity and frequency to achieve the desired outcome. PMID:28053988

Effects of Game-Based Constraint-Induced Movement Therapy on Balance in Patients with Stroke: A Single-Blind Randomized Controlled Trial.

PubMed

Choi, Ho-Suk; Shin, Won-Seob; Bang, Dae-Hyouk; Choi, Sung-Jin

2017-03-01

The aims of this work were to determine whether game-based constraint-induced movement therapy (CIMT) is effective at improving balance ability in patients with stroke, and to provide clinical knowledge of game-based training that allows application of CIMT to the lower extremities. Thirty-six patients with chronic stroke were randomly assigned to game-based CIMT (n = 12), general game-based training (n = 12), and conventional (n = 12) groups. All interventions were conducted 3 times a week for 4 weeks. The static balance control and weight-bearing symmetry were assessed, and the Functional Reach Test (FRT), modified Functional Reach Test (mFRT), and Timed Up and Go (TUG) test were performed to evaluate balance ability. All 3 groups showed significant improvement in anterior-posterior axis (AP-axis) distance, sway area, weight-bearing symmetry, FRT, mFRT, and TUG test after the intervention (P < 0.05). Post hoc analysis revealed significant differences in AP-axis, and sway area, weight-bearing symmetry of the game-based CIMT group compared with the other group (P < 0.05). Although the general game-based training and the game-based CIMT both improved on static and dynamic balance ability, game-based CIMT had a larger effect on static balance control, weight-bearing symmetry, and side-to-side weight shift.

Exergaming as a Viable Therapeutic Tool to Improve Static and Dynamic Balance among Older Adults and People with Idiopathic Parkinson's Disease: A Systematic Review and Meta-Analysis.

PubMed

Harris, Dale M; Rantalainen, Timo; Muthalib, Makii; Johnson, Liam; Teo, Wei-Peng

2015-01-01

The use of virtual reality games (known as "exergaming") as a neurorehabilitation tool is gaining interest. Therefore, we aim to collate evidence for the effects of exergaming on the balance and postural control of older adults and people with idiopathic Parkinson's disease (IPD). Six electronic databases were searched, from inception to April 2015, to identify relevant studies. Standardized mean differences (SMDs) and 95% confidence intervals (CI) were used to calculate effect sizes between experimental and control groups. I (2) statistics were used to determine levels of heterogeneity. 325 older adults and 56 people with IPD who were assessed across 11 -studies. The results showed that exergaming improved static balance (SMD 1.069, 95% CI 0.563-1.576), postural control (SMD 0.826, 95% CI 0.481-1.170), and dynamic balance (SMD -0.808, 95% CI -1.192 to -0.424) in healthy older adults. Two IPD studies showed an improvement in static balance (SMD 0.124, 95% CI -0.581 to 0.828) and postural control (SMD 2.576, 95% CI 1.534-3.599). Our findings suggest that exergaming might be an appropriate therapeutic tool for improving balance and postural control in older adults, but more -large-scale trials are needed to determine if the same is true for people with IPD.

Posturography and risk of recurrent falls in healthy non-institutionalized persons aged over 65.

PubMed

Buatois, Séverine; Gueguen, René; Gauchard, Gérome C; Benetos, Athanase; Perrin, Philippe P

2006-01-01

A poor postural stability in older people is associated with an increased risk of falling. The posturographic tool has widely been used to assess balance control; however, its value in predicting falls remains unclear. The purpose of this prospective study was to determine the predictive value of posturography in the estimation of the risk of recurrent falls, including a comparison with standard clinical balance tests, in healthy non-institutionalized persons aged over 65. Two hundred and six healthy non-institutionalized volunteers aged over 65 were tested. Postural control was evaluated by posturographic tests, performed on static, dynamic and dynamized platforms (static test, slow dynamic test and Sensory Organization Test [SOT]) and clinical balance tests (Timed 'Up & Go' test, One-Leg Balance, Sit-to-Stand-test). Subsequent falls were monitored prospectively with self-questionnaire sent every 4 months for a period of 16 months after the balance testing. Subjects were classified prospectively in three groups of Non-Fallers (0 fall), Single-Fallers (1 fall) and Multi-Fallers (more than 2 falls). Loss of balance during the last trial of the SOT sensory conflicting condition, when visual and somatosensory inputs were distorted, was the best factor to predict the risk of recurrent falls (OR = 3.6, 95% CI = 1.3-10.11). Multi-Fallers showed no postural adaptation during the repetitive trials of this sensory condition, contrary to Non-Fallers and Single-Fallers. The Multi-Fallers showed significantly more sway when visual inputs were occluded. The clinical balance tests, the static test and the slow dynamic test revealed no significant differences between the groups. In a sample of non-institutionalized older persons aged over 65, posturographic evaluation by the SOT, especially with repetition of the same task in sensory conflicting condition, compared to the clinical tests and the static and dynamic posturographic test, appears to be a more sensitive tool to identify those at high-risk of recurrent falls. Copyright (c) 2006 S. Karger AG, Basel.

Flight Reynolds Number Testing of the Orion Launch Abort Vehicle in the NASA Langley National Transonic Facility

NASA Technical Reports Server (NTRS)

Chan, David T.; Brauckmann, Gregory J.

2011-01-01

A 6%-scale unpowered model of the Orion Launch Abort Vehicle (LAV) ALAS-11-rev3c configuration was tested in the NASA Langley National Transonic Facility to obtain static aerodynamic data at flight Reynolds numbers. Subsonic and transonic data were obtained for Mach numbers between 0.3 and 0.95 for angles of attack from -4 to +22 degrees and angles of sideslip from -10 to +10 degrees. Data were also obtained at various intermediate Reynolds numbers between 2.5 million and 45 million depending on Mach number in order to examine the effects of Reynolds number on the vehicle. Force and moment data were obtained using a 6-component strain gauge balance that operated both at warm temperatures (+120 . F) and cryogenic temperatures (-250 . F). Surface pressure data were obtained with electronically scanned pressure units housed in heated enclosures designed to survive cryogenic temperatures. Data obtained during the 3-week test entry were used to support development of the LAV aerodynamic database and to support computational fluid dynamics code validation. Furthermore, one of the outcomes of the test was the reduction of database uncertainty on axial force coefficient for the static unpowered LAV. This was accomplished as a result of good data repeatability throughout the test and because of decreased uncertainty on scaling wind tunnel data to flight.

Static Force-Deflection Properties of Automobile Steering Components

DOT National Transportation Integrated Search

1987-06-01

This report provides the static force-deflection test results for 28 steering columns and 24 steering wheels used in domestic and import passener cars from model year 1975 to 1985. The steering columns and wheels tested include approzimately 90 perce...

Laboratory Evidence That Line-Tied Toroidal Magnetic Fields Can Suppress Loss-of-Equilibrium Flux Rope Eruptions in the Solar Corona

NASA Astrophysics Data System (ADS)

Myers, C. E.; Yamada, M.; Belova, E.; Ji, H.; Yoo, J.; Fox, W. R., II; Jara-Almonte, J.

2014-12-01

Loss-of-equilibrium mechanisms such as the ideal torus instability [Kliem & Török, Phys. Rev. Lett. 96, 255002 (2006)] are predicted to drive arched flux ropes in the solar corona to erupt. In recent line-tied flux rope experiments conducted in the Magnetic Reconnection Experiment (MRX), however, we find that quasi-statically driven flux ropes remain confined well beyond the predicted torus instability threshold. In order to understand this behavior, in situ measurements from a 300 channel 2D magnetic probe array are used to comprehensively analyze the force balance between the external (potential) and internal (plasma-generated) magnetic fields. We find that forces due to the line-tied toroidal magnetic field, which are not included in the basic torus instability theory, can play a major role in preventing eruptions. The dependence of these toroidal magnetic forces on various potential field and flux rope parameters will be discussed. This research is supported by DoE Contract Number DE-AC02-09CH11466 and by the NSF/DoE Center for Magnetic Self-Organization (CMSO).

Bistable front dynamics in a contractile medium: travelling wave and cortical advection define stable zones of RhoA signaling at epithelial adherens junctions

NASA Astrophysics Data System (ADS)

Neufeld, Zoltan

Recent studies have demonstrated that mechanical forces can lead to novel mechanisms of pattern formation such as clustering and oscillations in contractile systems. We investigate how contractile forces in mechanically active media can affect bistable front propagation. We found that contraction regulates the front speed or can fully suppress its propagation in space to create a static localized zone. We demonstrate how the interplay between biochemical signaling through positive feedback, combined with diffusion on the cell membrane and mechanical forces generated in the actomyosin cortex, can determine the spatial distribution of RhoA signaling at cell-cell junctions. The dynamical mechanism relies on the balance between a propagating bistable signal that is opposed by an advective flow generated by an actomyosin stress gradient. Experimental observations on the behaviour of the system when contractility is inhibited are in qualitative agreement with the predictions of the model. In collaboration with: Zoltan Neufeld, Guillermo A. Gomez, and Alpha S. Yap, University of Queensland, Brisbane, Australia

Balance and postural skills in normal-weight and overweight prepubertal boys.

PubMed

Deforche, Benedicte I; Hills, Andrew P; Worringham, Charles J; Davies, Peter S W; Murphy, Alexia J; Bouckaert, Jacques J; De Bourdeaudhuij, Ilse M

2009-01-01

This study investigated differences in balance and postural skills in normal-weight versus overweight prepubertal boys. Fifty-seven 8-10-year-old boys were categorized overweight (N = 25) or normal-weight (N = 32) according to the International Obesity Task Force cut-off points for overweight in children. The Balance Master, a computerized pressure plate system, was used to objectively measure six balance skills: sit-to-stand, walk, step up/over, tandem walk (walking on a line), unilateral stance and limits of stability. In addition, three standardized field tests were employed: standing on one leg on a balance beam, walking heel-to-toe along the beam and the multiple sit-to-stand test. Overweight boys showed poorer performances on several items assessed on the Balance Master. Overweight boys had slower weight transfer (p < 0.05), lower rising index (p < 0.05) and greater sway velocity (p < 0.001) in the sit-to-stand test, greater step width while walking (p < 0.05) and lower speed when walking on a line (p < 0.01) compared with normal-weight counterparts. Performance on the step up/over test, the unilateral stance and the limits of stability were comparable between both groups. On the balance beam, overweight boys could not hold their balance on one leg as long (p < 0.001) and had fewer correct steps in the heel-to-toe test (p < 0.001) than normal-weight boys. Finally, overweight boys were slower in standing up and sitting down five times in the multiple sit-to-stand task (p < 0.01). This study demonstrates that when categorised by body mass index (BMI) level, overweight prepubertal boys displayed lower capacity on several static and dynamic balance and postural skills.

The Effect of Underwater Gait Training on Balance Ability of Stroke Patients

PubMed Central

Park, Seok Woo; Lee, Kyoung Jin; Shin, Doo Chul; Shin, Seung Ho; Lee, Myung Mo; Song, Chang Ho

2014-01-01

[Purpose] The purpose of this study was to investigate the effects of underwater treadmill gait training on the balance ability of stroke patients. [Subjects] Twenty-two patients with stroke were randomly assigned to an underwater treadmill group (n =11) or a control group (n =11). [Methods] Both groups received general rehabilitation for 30 min per session, 5 times per week, over a 4-week period. The underwater treadmill group received additional underwater gait training for 30 min per session, 5 times per week, over the same 4-week period. Static and dynamic balances were evaluated before and after the intervention. [Results] The means of static and dynamic balance ability increased significantly in both groups, but there was no significant difference between the two groups. [Conclusion] Compared to the general rehabilitation program, underwater treadmill gait training was not more effective at improving the balance ability of stroke patients than land-based training. PMID:25013292

Motor control goes beyond physics: differential effects of gravity and inertia on finger forces during manipulation of hand-held objects.

PubMed

Zatsiorsky, Vladimir M; Gao, Fan; Latash, Mark L

2005-04-01

According to basic physics, the local effects induced by gravity and acceleration are identical and cannot be separated by any physical experiment. In contrast-as this study shows-people adjust the grip forces associated with gravitational and inertial forces differently. In the experiment, subjects oscillated a vertically-oriented handle loaded with five different weights (from 3.8 N to 13.8 N) at three different frequencies in the vertical plane: 1 Hz, 1.5 Hz and 2.0 Hz. Three contributions to the grip force-static, dynamic, and stato-dynamic fractions-were quantified. The static fraction reflects grip force related to holding a load statically. The stato-dynamic fraction reflects a steady change in the grip force when the same load is moved cyclically. The dynamic fraction is due to acceleration-related adjustments of the grip force during oscillation cycles. The slope of the relation between the grip force and the load force was steeper for the static fraction than for the dynamic fraction. The stato-dynamic fraction increased with the frequency and load. The slope of the dynamic grip force-load force relation decreased with frequency, and as a rule, increased with the load. Hence, when adjusting grip force to task requirements, the central controller takes into account not only the expected magnitude of the load force but also such factors as whether the force is gravitational or inertial and the contributions of the object mass and acceleration to the inertial force. As an auxiliary finding, a complex finger coordination pattern aimed at preserving the rotational equilibrium of the object during shaking movements was reported.

Static and dynamic postural control in low-vision and normal-vision adults.

PubMed

Tomomitsu, Mônica S V; Alonso, Angelica Castilho; Morimoto, Eurica; Bobbio, Tatiana G; Greve, Julia M D

2013-04-01

This study aimed to evaluate the influence of reduced visual information on postural control by comparing low-vision and normal-vision adults in static and dynamic conditions. Twenty-five low-vision subjects and twenty-five normal sighted adults were evaluated for static and dynamic balance using four protocols: 1) the Modified Clinical Test of Sensory Interaction on Balance on firm and foam surfaces with eyes opened and closed; 2) Unilateral Stance with eyes opened and closed; 3) Tandem Walk; and 4) Step Up/Over. The results showed that the low-vision group presented greater body sway compared with the normal vision during balance on a foam surface (p≤0.001), the Unilateral Stance test for both limbs (p≤0.001), and the Tandem Walk test. The low-vision group showed greater step width (p≤0.001) and slower gait speed (p≤0.004). In the Step Up/Over task, low-vision participants were more cautious in stepping up (right p≤0.005 and left p≤0.009) and in executing the movement (p≤0.001). These findings suggest that visual feedback is crucial for determining balance, especially for dynamic tasks and on foam surfaces. Low-vision individuals had worse postural stability than normal-vision adults in terms of dynamic tests and balance on foam surfaces.

The Balance Control of Children with and without Hearing Impairment in Singapore--A Case Study

ERIC Educational Resources Information Center

Jernice, Tan Sing Yee; Nonis, Karen P.; Yi, Chow Jia

2011-01-01

The purpose of this study is to compare the balance control of participants with and without HI and also to investigate the effect of a Balance Programme (BP) on their balance control (HI; n = 2, M age = 7 years old). The BP consisted of six practice sessions of 45 minutes each. The Balance Tasks used to assess balance control were static Balance…

Effects of orthopedic insoles on static balance of older adults wearing thick socks.

PubMed

Ma, Christina Zong-Hao; Wong, Duo Wai-Chi; Wan, Anson Hong-Ping; Lee, Winson Chiu-Chun

2018-06-01

The wearing of socks and insoles may affect the ability of the foot to detect tactile input influencing postural balance. The aim of this study was to investigate whether (1) thick socks adversely affected the elderly postural balance and (2) orthopedic insoles could improve the elderly postural balance while wearing thick socks. Repeated-measures study design. In total, 14 healthy older adults were recruited. A monofilament test was conducted to evaluate foot plantar sensation with and without thick socks. Subjects then performed the Romberg tests under three conditions: (1) barefoot, (2) with socks only, and (3) with both socks and insoles. Postural balance was assessed by measuring the center of pressure movement during standing in each experimental condition. Thick socks significantly decreased the monofilament score ( p < 0.001), suggesting reduction in ability to detect external forces. All center of pressure parameters increased significantly while wearing thick socks ( p < 0.017), implying reduction of postural stability. They then decreased significantly with the additional use of insoles ( p < 0.017). Previous studies have documented the changes in plantar pressure distribution with the use of orthopedic insoles. This study further suggests that such changes in contact mechanics could produce some balance-improving effects, which appears not to have been reported earlier. Clinical relevance Wearing thick socks reduces plantar pressure sensitivity and increases postural sway which may increase risk of falls. Orthopedic insoles and footwear with similar design could potentially be a cost-effective method in maintaining postural balance when wearing thick socks.

Wagon instability in long trains

NASA Astrophysics Data System (ADS)

Cole, Colin; McClanachan, Mitchell; Spiryagin, Maksym; Sun, Yan Quan

2012-01-01

Lateral force components and impacts from couplers can adversely affect wagon stability. These issues are significant in longer and heavier trains increasing the risk of wagon rollover, wheel climb, wagon body pitch, bogie pitch and wagon lift-off. Modelling of coupler angles has been added to normal longitudinal train simulation to allow comprehensive study of lateral components of coupler forces. Lateral coupler forces are then combined with centripetal inertia calculations to determine quasi-static lateral forces, quasi-static vertical forces and quasi-static bogie lateral to vertical ratio, allowing the study of stringlining, buckling and wagon rollover risks. The approach taken allows for different rolling stock lengths, overhang and coupling lengths, and allows the study of angles occurring in transitions. Wagon body and bogie pitch are also studied with enhancements added to previous modelling to allow the study of wagon lift-off.

Effects of Plantar Flexor Muscle Static Stretching Alone and Combined With Massage on Postural Balance.

PubMed

Hemmati, Ladan; Rojhani-Shirazi, Zahra; Ebrahimi, Samaneh

2016-10-01

To evaluate and compare the effects of stretching and combined therapy (stretching and massage) on postural balance in people aged 50 to 65 years. Twenty-three subjects participated in this nonrandomized clinical trial study. Each participant randomly received plantar flexor muscle stretching (3 cycles of 45 seconds with a 30-second recovery period between cycles) alone and in combination with deep stroking massage (an interval of at least 30 minutes separated the two interventions). The data were recorded with a force platform immediately after each condition with eyes open and closed. The center of pressure displacement and velocity along the mediolateral and anteroposterior axes were calculated under each condition. The data were analyzed with multiple-pair t-tests. The center of pressure displacement and velocity along the mediolateral axis increased after both stretching and the combined intervention. There were significant differences in both values between participants in the stretching and combined interventions (p<0.05). Plantar flexor muscle stretching (for 45 seconds) combined with deep stroking massage may have more detrimental effects on postural balance than stretching alone because each intervention can intensify the effects of the other.

Biomechanics of the incudo-malleolar-joint - Experimental investigations for quasi-static loads.

PubMed

Ihrle, S; Gerig, R; Dobrev, I; Röösli, C; Sim, J H; Huber, A M; Eiber, A

2016-10-01

Under large quasi-static loads, the incudo-malleolar joint (IMJ), connecting the malleus and the incus, is highly mobile. It can be classified as a mechanical filter decoupling large quasi-static motions while transferring small dynamic excitations. This is presumed to be due to the complex geometry of the joint inducing a spatial decoupling between the malleus and incus under large quasi-static loads. Spatial Laser Doppler Vibrometer (LDV) displacement measurements on isolated malleus-incus-complexes (MICs) were performed. With the malleus firmly attached to a probe holder, the incus was excited by applying quasi-static forces at different points. For each force application point the resulting displacement was measured subsequently at different points on the incus. The location of the force application point and the LDV measurement points were calculated in a post-processing step combining the position of the LDV points with geometric data of the MIC. The rigid body motion of the incus was then calculated from the multiple displacement measurements for each force application point. The contact regions of the articular surfaces for different load configurations were calculated by applying the reconstructed motion to the geometry model of the MIC and calculate the minimal distance of the articular surfaces. The reconstructed motion has a complex spatial characteristic and varies for different force application points. The motion changed with increasing load caused by the kinematic guidance of the articular surfaces of the joint. The IMJ permits a relative large rotation around the anterior-posterior axis through the joint when a force is applied at the lenticularis in lateral direction before impeding the motion. This is part of the decoupling of the malleus motion from the incus motion in case of large quasi-static loads. Copyright © 2015 Elsevier B.V. All rights reserved.

Influences of posterior-located center of gravity on lumbar extension strength, balance, and lumbar lordosis in chronic low back pain.

PubMed

Kim, Dae-Hun; Park, Jin-Kyu; Jeong, Myeong-Kyun

2014-01-01

In patients with chronic low back pain, the center of gravity (COG) is abnormally located posterior to the center in most cases. The purpose of this study was to examine the effects of posterior-located COG on the functions (lumbar extension strength, and static and dynamic balance) and structure (lumbar lordosis angle and lumbosacral angle) of the lumbar spine. In this study, the COG of chronic low back pain patients who complained of only low back pain were examined using dynamic body balance equipment. A total of 164 subjects participated in the study (74 males and 90 females), and they were divided into two groups of 82 patients each. One group (n=82) consisted of patients whose COG was located at the center (C-COG); the other group (n=82) consisted of patients whose COG was located posterior to the center (P-COG). The following measures assessed the lumber functions and structures of the two groups: lumbar extension strength, moving speed of static and dynamic COGs, movement distance of the static and dynamic COGs, lumbar lordosis angle, and lumbosacral angle. The measured values were analyzed using independent t-tests. The group of patients with P-COG showed more decreases in lumbar extension strength, lumbar lordosis angle, and lumbosacral angle compared to the group of patients with C-COG. Also this group showed increases in moving speed and movement distance of the static COG. However, there were no differences in moving speed and movement distance of the dynamic COG between the two groups. These findings suggest that chronic LBP patients with P-COG have some disadvantages to establish lumbar extension strength and static and dynamic balance, which require specific efforts to maintain a neutral position and to control posture.

Inducer Hydrodynamic Forces in a Cavitating Environment

NASA Technical Reports Server (NTRS)

Skelley, Stephen E.

2004-01-01

Marshall Space Flight Center has developed and demonstrated a measurement device for sensing and resolving the hydrodynamic loads on fluid machinery. The device - a derivative of the six-component wind tunnel balance - senses the forces and moments on the rotating device through a weakened shaft section instrumented with a series of strain gauges. This rotating balance was designed to directly measure the steady and unsteady hydrodynamic loads on an inducer, thereby defining the amplitude and frequency content associated with operating in various cavitation modes. The rotating balance was calibrated statically using a dead-weight load system in order to generate the 6 x 12 calibration matrix later used to convert measured voltages to engineering units. Structural modeling suggested that the rotating assembly first bending mode would be significantly reduced with the balance s inclusion. This reduction in structural stiffness was later confirmed experimentally with a hammer-impact test. This effect, coupled with the relatively large damping associated with the rotating balance waterproofing material, limited the device s bandwidth to approximately 50 Hertz Other pre-test validations included sensing the test article rotating assembly built-in imbalance for two configurations and directly measuring the assembly mass and buoyancy while submerged under water. Both tests matched predictions and confirmed the device s sensitivity while stationary and rotating. The rotating balance was then demonstrated in a water test of a full-scale Space Shuttle Main Engine high-pressure liquid oxygen pump inducer. Experimental data was collected a scaled operating conditions at three flow coefficients across a range of cavitation numbers for the single inducer geometry and radial clearance. Two distinct cavitation modes were observed symmetric tip vortex cavitation and alternate-blade cavitation. Although previous experimental tests on the same inducer demonstrated two additional cavitation modes at lower inlet pressures, these conditions proved unreachable with the rotating balance installed due to the intense dynamic environment. The sensed radial load was less influenced by flow coefficient than by cavitation number or cavitation mode although the flow coefficient range was relatively narrow. Transition from symmetric tip vortex to alternate-blade cavitation corresponded to changes in both radial load magnitude and radial load orientation relative to the inducer. Sensed moments indicated that the effective load center moved downstream during this change in cavitation mode. An occurrence of "higher+rdex cavitation" was also detected in both the stationary pressures and the rotating balance data although the frequency of the phenomena was well above the reliable bandwidth of the rotating balance. In summary the experimental tests proved both the concept and device s capability despite the limitations and confirmed that hydrodynamically-induced forces and moments develop in response to the unbalanced pressure field, which is, in turn, a product of the cavitation environment.

A COMPARISON OF STATIC AND DYNAMIC OPTIMIZATION MUSCLE FORCE PREDICTIONS DURING WHEELCHAIR PROPULSION

PubMed Central

Morrow, Melissa M.; Rankin, Jeffery W.; Neptune, Richard R.; Kaufman, Kenton R.

2014-01-01

The primary purpose of this study was to compare static and dynamic optimization muscle force and work predictions during the push phase of wheelchair propulsion. A secondary purpose was to compare the differences in predicted shoulder and elbow kinetics and kinematics and handrim forces. The forward dynamics simulation minimized differences between simulated and experimental data (obtained from 10 manual wheelchair users) and muscle co-contraction. For direct comparison between models, the shoulder and elbow muscle moment arms and net joint moments from the dynamic optimization were used as inputs into the static optimization routine. RMS errors between model predictions were calculated to quantify model agreement. There was a wide range of individual muscle force agreement that spanned from poor (26.4 % Fmax error in the middle deltoid) to good (6.4 % Fmax error in the anterior deltoid) in the prime movers of the shoulder. The predicted muscle forces from the static optimization were sufficient to create the appropriate motion and joint moments at the shoulder for the push phase of wheelchair propulsion, but showed deviations in the elbow moment, pronation-supination motion and hand rim forces. These results suggest the static approach does not produce results similar enough to be a replacement for forward dynamics simulations, and care should be taken in choosing the appropriate method for a specific task and set of constraints. Dynamic optimization modeling approaches may be required for motions that are greatly influenced by muscle activation dynamics or that require significant co-contraction. PMID:25282075

Orientation of Magnetized MnBi in a Strong Static Magnetic Field

NASA Astrophysics Data System (ADS)

Zheng, Tianxiang; Zhong, Yunbo; Dong, Licheng; Zhou, Bangfei; Ren, Zhongming; Debray, Francois; Beaugnon, Eric

2018-06-01

Solidification of Bi-4.5 wt pct Mn alloy was investigated in the presence and absence of a strong static magnetic field (SSMF). A cooling rate ( R) of 60 K/min caused MnBi to orient with the SSMF, owing to the force moment and attractive force. The attractive force and magnetic gradient force induced formation of multilayered MnBi when R was 5 K/min. The magnetic gradient force was damped when R was 60 K/min. Low cooling rates favored the aggregation process.

The Association of Flexibility, Balance, and Lumbar Strength with Balance Ability: Risk of Falls in Older Adults

PubMed Central

Emilio, Emilio J. Martínez-López; Hita-Contreras, Fidel; Jiménez-Lara, Pilar M.; Latorre-Román, Pedro; Martínez-Amat, Antonio

2014-01-01

The purpose of the present study was to determine the effects of a proprioceptive training program on older adults, as well as to analyze the association between flexibility, balance and lumbar strength (physical fitness test) with balance ability and fall risk (functional balance tests). This study was a controlled, longitudinal trial with a 12-week follow-up period. Subjects from a population of older adults were allocated to the intervention group (n = 28) or to the usual care (control) group (n = 26). Subjects performed proprioceptive training twice weekly (6 specific exercises with Swiss ball and BOSU). Each session included 50 minutes (10 minutes of warm-up with slow walk, 10 minutes of mobility and stretching exercises, 30 minutes of proprioceptive exercises). The outcome variables were physical fitness (lower-body flexibility, hip-joint mobility, dynamic balance, static balance, and lumbar strength) and functional balance (Berg scale and Tinetti test). The experimental group obtained significantly higher values than the control group in lower-body flexibility, dynamic balance, and lumbar strength (p = 0.019, p < 0.001, and p = 0.034 respectively). Hip-joint mobility, dynamic balance, and lumbar strength were positively associated with balance ability (p < 0.001, p < 0.001, and p = 0.014, respectively) and the prevention of falls (p = 0.001, p < 0.001, and p = 0.017 respectively). These findings suggest that a 12-week proprioception program intervention (twice a week) significantly improves flexibility, balance, and lumbar strength in older adults. Hip-joint mobility, dynamic balance and lumbar strength are positively associated to balance ability and the risk of falls in older adults. This proprioceptive training does not show a significant improvement in hip-joint mobility or static balance. Key points A 12-week proprioceptive intervention program (two times per week) significantly improves flexibility, balance, and lumbar strength in older adults. The risk of falls and balance ability are significantly improved after a training program with Bosu and Swiss ball in older adults. An improvement in joint mobility, dynamic balance and lumbar strength is positively associated with balance ability and improved fall risk in older adults. A 12-week proprioceptive intervention program (two times per week) does not show a significant improvement in hip-joint mobility and static balance. PMID:24790489

Repelling, binding, and oscillating of two-particle discrete-time quantum walks

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

Wang, Qinghao; Li, Zhi-Jian, E-mail: zjli@sxu.edu.cn

In this paper, we investigate the effects of particle–particle interaction and static force on the propagation of probability distribution in two-particle discrete-time quantum walk, where the interaction and static force are expressed as a collision phase and a linear position-dependent phase, respectively. It is found that the interaction can lead to boson repelling and fermion binding. The static force also induces Bloch oscillation and results in a continuous transition from boson bunching to fermion anti-bunching. The interplays of particle–particle interaction, quantum interference, and Bloch oscillation provide a versatile framework to study and simulate many-particle physics via quantum walks.

A Study of the Use of Contact Loading to Simulate Low Velocity Impact

NASA Technical Reports Server (NTRS)

Highsmith, Alton L.

1997-01-01

Although numerous studies on the impact response of laminated composites have been conducted, there is as yet no agreement within the composites community on what parameter or parameters are adequate for quantifying the severity of an impact event. One of the more interesting approaches that has been proposed uses the maximum contact force during impact to "quantify" the severity of the impact event, provided that the impact velocity is sufficiently low. A significant advantage of this approach, should it prove to be reliable, is that quasi-static contact loading could be used to simulate low velocity impact. In principle, a single specimen, loaded quasi-statically to successively increasing contact loads could be used to map the entire spectrum of damage as a function of maximum contact force. The present study had as its objective assessing whether or not the maximum contact force during impact is a suitable parameter for characterizing an impact. The response of [+/-60/0(sub 4)/+/-60/0(sub 2)](sub s) laminates fabricated from Fiberite T300/934 graphite epoxy and subjected to quasi-static contact loading and to low velocity impact was studied. Three quasi-static contact load levels - 525 lb., 600 lb., and 675 lb. - were selected. Three impact energy levels - 1.14 ft.-lb., 2.0 ft.-lb., and 2.60 ft.-lb. - were chosen in an effort to produce impact events in which the maximum contact forces during the impact events were 525 lb., 600 lb., and 625 lb., respectively. Damage development was documented using dye-penetrant enhanced x-ray radiography. A digital image processing technique was used to obtain quantitative information about the damage zone. Although it was intended that the impact load levels produce maximum contact forces equal to those used in the quasi-static contact experiments, larger contact forces were developed during impact loading. In spite of this, the damage zones developed in impacted specimens were smaller than the damage zones developed in specimens subjected to the corresponding quasi-static contact loading. The impacted specimens may have a greater tendency to develop fiber fracture, but, at present, a quantitative assessment of fiber fracture is not available. In addressing whether or not contact force is an adequate metric for describing the severity of an impact event, the results of this study suggest that it is not. In cases where the quasi-static load level and the maximum contact force during impact were comparable, the quasi-statically loaded specimens consistently developed larger damage zones. It should be noted, however, that using quasi-static damage data to forecast the behavior of impacted material may give conservative estimates of the residual strength of impacted composites.

The effect of a senior jazz dance class on static balance in healthy women over 50 years of age: a pilot study.

PubMed

Wallmann, Harvey W; Gillis, Carrie B; Alpert, Patricia T; Miller, Sally K

2009-01-01

The purpose of this pilot study is to assess the impact of a senior jazz dance class on static balance for healthy women over 50 years of age using the NeuroCom Smart Balance Master System (Balance Master). A total of 12 healthy women aged 54-88 years completed a 15-week jazz dance class which they attended 1 time per week for 90 min per class. Balance data were collected using the Sensory Organization Test (SOT) at baseline (pre), at 7 weeks (mid), and after 15 weeks (post). An equilibrium score measuring postural sway was calculated for each of six different conditions. The composite equilibrium score (all six conditions integrated to 1 score) was used as an overall measure of balance. Repeated measures analyses of variance (ANOVAs) were used to compare the means of each participant's SOT composite equilibrium score in addition to the equilibrium score for each individual condition (1-6) across the 3 time points (pre, mid, post). There was a statistically significant difference among the means, p < .0005. Pairwise (Bonferroni) post hoc analyses revealed the following statistically significant findings for SOT composite equilibrium scores for the pre (67.33 + 10.43), mid (75.25 + 6.97), and post (79.00 + 4.97) measurements: premid (p = .008); prepost (p < .0005); midpost (p = .033). In addition, correlational statistics were used to determine any relationship between SOT scores and age. Results indicated that administration of a 15-week jazz dance class 1 time per week was beneficial in improving static balance as measured by the Balance Master SOT.

Reliability and concurrent validity of the Microsoft Xbox One Kinect for assessment of standing balance and postural control.

PubMed

Clark, Ross A; Pua, Yong-Hao; Oliveira, Cristino C; Bower, Kelly J; Thilarajah, Shamala; McGaw, Rebekah; Hasanki, Ksaniel; Mentiplay, Benjamin F

2015-07-01

The Microsoft Kinect V2 for Windows, also known as the Xbox One Kinect, includes new and potentially far improved depth and image sensors which may increase its accuracy for assessing postural control and balance. The aim of this study was to assess the concurrent validity and reliability of kinematic data recorded using a marker-based three dimensional motion analysis (3DMA) system and the Kinect V2 during a variety of static and dynamic balance assessments. Thirty healthy adults performed two sessions, separated by one week, consisting of static standing balance tests under different visual (eyes open vs. closed) and supportive (single limb vs. double limb) conditions, and dynamic balance tests consisting of forward and lateral reach and an assessment of limits of stability. Marker coordinate and joint angle data were concurrently recorded using the Kinect V2 skeletal tracking algorithm and the 3DMA system. Task-specific outcome measures from each system on Day 1 and 2 were compared. Concurrent validity of trunk angle data during the dynamic tasks and anterior-posterior range and path length in the static balance tasks was excellent (Pearson's r>0.75). In contrast, concurrent validity for medial-lateral range and path length was poor to modest for all trials except single leg eyes closed balance. Within device test-retest reliability was variable; however, the results were generally comparable between devices. In conclusion, the Kinect V2 has the potential to be used as a reliable and valid tool for the assessment of some aspects of balance performance. Copyright © 2015 Elsevier B.V. All rights reserved.

The Hydromagnetic Interior of a Solar Quiescent Prominence. I. Coupling between Force Balance and Steady Energy Transport

NASA Astrophysics Data System (ADS)

Low, B. C.; Berger, T.; Casini, R.; Liu, W.

2012-08-01

This series of papers investigates the dynamic interiors of quiescent prominences revealed by recent Hinode and SDO/AIA high-resolution observations. This first paper is a study of the static equilibrium of the Kippenhahn-Schlüter diffuse plasma slab, suspended vertically in a bowed magnetic field, under the frozen-in condition and subject to a theoretical thermal balance among an optically thin radiation, heating, and field-aligned thermal conduction. The everywhere-analytical solutions to this nonlinear problem are an extremely restricted subset of the physically admissible states of the system. For most values of the total mass frozen into a given bowed field, force balance and steady energy transport cannot both be met without a finite fraction of the total mass having collapsed into a cold sheet of zero thickness, within which the frozen-in condition must break down. An exact, resistive hydromagnetic extension of the Kippenhahn-Schlüter slab is also presented, resolving the mass-sheet singularity into a finite-thickness layer of steadily falling dense fluid. Our hydromagnetic result suggests that the narrow, vertical prominence Hα threads may be falling across magnetic fields, with optically thick cores much denser and ionized to much lower degrees than conventionally considered. This implication is discussed in relation to (1) the recent SDO/AIA observations of quiescent prominences that are massive and yet draining mass everywhere in their interiors, (2) the canonical range of 5-60 G determined from spectral polarimetric observations of prominence magnetic fields over the years, and (3) the need for a more realistic multi-fluid treatment.

The role of large-scale eddies in the climate equilibrium. Part 2: Variable static stability

NASA Technical Reports Server (NTRS)

Zhou, Shuntai; Stone, Peter H.

1993-01-01

Lorenz's two-level model on a sphere is used to investigate how the results of Part 1 are modified when the interaction of the vertical eddy heat flux and static stability is included. In general, the climate state does not depend very much on whether or not this interaction is included, because the poleward eddy heat transport dominates the eddy forcing of mean temperature and wind fields. However, the climatic sensitivity is significantly affected. Compared to two-level model results with fixed static stability, the poleward eddy heat flux is less sensitive to the meridional temperature gradient and the gradient is more sensitive to the forcing. For example, the logarithmic derivative of the eddy flux with respect to the gradient has a slope that is reduced from approximately 15 on a beta-plane with fixed static stability and approximately 6 on a sphere with fixed static stability, to approximately 3 to 4 in the present model. This last result is more in line with analyses from observations. The present model also has a stronger baroclinic adjustment than that in Part 1, more like that in two-level beta-plane models with fixed static stability, that is, the midlatitude isentropic slope is very insensitive to the forcing, the diabatic heating, and the friction, unless the forcing is very weak.

The force synergy of human digits in static and dynamic cylindrical grasps.

PubMed

Kuo, Li-Chieh; Chen, Shih-Wei; Lin, Chien-Ju; Lin, Wei-Jr; Lin, Sheng-Che; Su, Fong-Chin

2013-01-01

This study explores the force synergy of human digits in both static and dynamic cylindrical grasping conditions. The patterns of digit force distribution, error compensation, and the relationships among digit forces are examined to quantify the synergetic patterns and coordination of multi-finger movements. This study recruited 24 healthy participants to perform cylindrical grasps using a glass simulator under normal grasping and one-finger restricted conditions. Parameters such as the grasping force, patterns of digit force distribution, and the force coefficient of variation are determined. Correlation coefficients and principal component analysis (PCA) are used to estimate the synergy strength under the dynamic grasping condition. Specific distribution patterns of digit forces are identified for various conditions. The compensation of adjacent fingers for the force in the normal direction of an absent finger agrees with the principle of error compensation. For digit forces in anti-gravity directions, the distribution patterns vary significantly by participant. The forces exerted by the thumb are closely related to those exerted by other fingers under all conditions. The index-middle and middle-ring finger pairs demonstrate a significant relationship. The PCA results show that the normal forces of digits are highly coordinated. This study reveals that normal force synergy exists under both static and dynamic cylindrical grasping conditions.

The Force Synergy of Human Digits in Static and Dynamic Cylindrical Grasps

PubMed Central

Kuo, Li-Chieh; Chen, Shih-Wei; Lin, Chien-Ju; Lin, Wei-Jr; Lin, Sheng-Che; Su, Fong-Chin

2013-01-01

This study explores the force synergy of human digits in both static and dynamic cylindrical grasping conditions. The patterns of digit force distribution, error compensation, and the relationships among digit forces are examined to quantify the synergetic patterns and coordination of multi-finger movements. This study recruited 24 healthy participants to perform cylindrical grasps using a glass simulator under normal grasping and one-finger restricted conditions. Parameters such as the grasping force, patterns of digit force distribution, and the force coefficient of variation are determined. Correlation coefficients and principal component analysis (PCA) are used to estimate the synergy strength under the dynamic grasping condition. Specific distribution patterns of digit forces are identified for various conditions. The compensation of adjacent fingers for the force in the normal direction of an absent finger agrees with the principle of error compensation. For digit forces in anti-gravity directions, the distribution patterns vary significantly by participant. The forces exerted by the thumb are closely related to those exerted by other fingers under all conditions. The index-middle and middle-ring finger pairs demonstrate a significant relationship. The PCA results show that the normal forces of digits are highly coordinated. This study reveals that normal force synergy exists under both static and dynamic cylindrical grasping conditions. PMID:23544151

Effect of expertise in shooting and Taekwondo on bipedal and unipedal postural control isolated or concurrent with a reaction-time task.

PubMed

Negahban, Hossein; Aryan, Najmolhoda; Mazaheri, Masood; Norasteh, Ali Asghar; Sanjari, Mohammad Ali

2013-06-01

It was hypothesized that training in 'static balance' or 'dynamic balance' sports has differential effects on postural control and its attention demands during quiet standing. In order to test this hypothesis, two groups of female athletes practicing shooting, as a 'static balance' sport, and Taekwondo, as a 'dynamic balance' sport, and a control group of non-physically active females voluntarily participated in this study. Postural control was assessed during bipedal and unipedal stance with and without performing a Go/No-go reaction time task. Visual and/or support surface conditions were manipulated in bipedal and unipedal stances in order to modify postural difficulty. Mixed model analysis of variance was used to determine the effects of dual tasking on postural and cognitive performance. Similar pattern of results were found in bipedal and unipedal stances, with Taekwondo practitioners displaying larger sway, shooters displaying lower sway and non-athletes displaying sway characteristics intermediate to Taekwondo and shooting athletes. Larger effect was found in bipedal stance. Single to dual-task comparison of postural control showed no significant effect of mental task on sway velocity in shooters, indicating less cognitive effort invested in balance control during bipedal stance. We suggest that expertise in shooting has a more pronounced effect on decreased sway in static balance conditions. Furthermore, shooters invest less attention in postures that are more specific to their training, i.e. bipedal stance. Copyright © 2012 Elsevier B.V. All rights reserved.

Exergaming as a Viable Therapeutic Tool to Improve Static and Dynamic Balance among Older Adults and People with Idiopathic Parkinson’s Disease: A Systematic Review and Meta-Analysis

PubMed Central

Harris, Dale M.; Rantalainen, Timo; Muthalib, Makii; Johnson, Liam; Teo, Wei-Peng

2015-01-01

The use of virtual reality games (known as “exergaming”) as a neurorehabilitation tool is gaining interest. Therefore, we aim to collate evidence for the effects of exergaming on the balance and postural control of older adults and people with idiopathic Parkinson’s disease (IPD). Six electronic databases were searched, from inception to April 2015, to identify relevant studies. Standardized mean differences (SMDs) and 95% confidence intervals (CI) were used to calculate effect sizes between experimental and control groups. I2 statistics were used to determine levels of heterogeneity. 325 older adults and 56 people with IPD who were assessed across 11 ­studies. The results showed that exergaming improved static balance (SMD 1.069, 95% CI 0.563–1.576), postural control (SMD 0.826, 95% CI 0.481–1.170), and dynamic balance (SMD −0.808, 95% CI −1.192 to −0.424) in healthy older adults. Two IPD studies showed an improvement in static balance (SMD 0.124, 95% CI −0.581 to 0.828) and postural control (SMD 2.576, 95% CI 1.534–3.599). Our findings suggest that exergaming might be an appropriate therapeutic tool for improving balance and postural control in older adults, but more ­large-scale trials are needed to determine if the same is true for people with IPD. PMID:26441634

Method of Calibrating a Force Balance

NASA Technical Reports Server (NTRS)

Parker, Peter A. (Inventor); Rhew, Ray D. (Inventor); Johnson, Thomas H. (Inventor); Landman, Drew (Inventor)

2015-01-01

A calibration system and method utilizes acceleration of a mass to generate a force on the mass. An expected value of the force is calculated based on the magnitude and acceleration of the mass. A fixture is utilized to mount the mass to a force balance, and the force balance is calibrated to provide a reading consistent with the expected force determined for a given acceleration. The acceleration can be varied to provide different expected forces, and the force balance can be calibrated for different applied forces. The acceleration may result from linear acceleration of the mass or rotational movement of the mass.

Dance Therapy with Physical Therapy for Children with Down Syndrome.

ERIC Educational Resources Information Center

Dupont, Blanche Burt; Schulmann, Diana

This study sought to investigate effects of a dance program on bilateral toe-standing balance and single-point static balance skills of a group of children with Down Syndrome. Thirteen experimental and 10 control group students between the ages of 3 and 13 years were assessed on toe-standing balance and single-point standing balance on the right…

The Relationship with Balance, Foot Posture, and Foot Size in School of Physical Education and Sports Students

ERIC Educational Resources Information Center

Irez, Gonul Babayigit

2014-01-01

The aim of this study is to investigate the relationship of foot posture and foot size with balance. A hundred and thirteen healthy volunteers were recruited from undergraduate students (Male = 74, Female = 37, age range 18-22). The Foot Posture Index (FPI-6), anthropometric measurements, dynamic balance and static balance measurements were done…

The effect of viewing a virtual environment through a head-mounted display on balance.

PubMed

Robert, Maxime T; Ballaz, Laurent; Lemay, Martin

2016-07-01

In the next few years, several head-mounted displays (HMD) will be publicly released making virtual reality more accessible. HMD are expected to be widely popular at home for gaming but also in clinical settings, notably for training and rehabilitation. HMD can be used in both seated and standing positions; however, presently, the impact of HMD on balance remains largely unknown. It is therefore crucial to examine the impact of viewing a virtual environment through a HMD on standing balance. To compare static and dynamic balance in a virtual environment perceived through a HMD and the physical environment. The visual representation of the virtual environment was based on filmed image of the physical environment and was therefore highly similar. This is an observational study in healthy adults. No significant difference was observed between the two environments for static balance. However, dynamic balance was more perturbed in the virtual environment when compared to that of the physical environment. HMD should be used with caution because of its detrimental impact on dynamic balance. Sensorimotor conflict possibly explains the impact of HMD on balance. Copyright © 2016 Elsevier B.V. All rights reserved.

Balance and Risk of Fall in Individuals with Bilateral Mild and Moderate Knee Osteoarthritis

PubMed Central

Khalaj, Nafiseh; Abu Osman, Noor Azuan; Mokhtar, Abdul Halim; Mehdikhani, Mahboobeh; Wan Abas, Wan Abu Bakar

2014-01-01

Balance is essential for mobility and performing activities of daily living. People with knee osteoarthritis display impairment in knee joint proprioception. Thus, the aim of this study was to evaluate balance and risk of fall in individuals with bilateral mild and moderate knee osteoarthritis. Sixty subjects aged between 50 and 70 years volunteered in this study. They were categorized into three groups which were healthy (n = 20), mild (n = 20) and moderate (n = 20) bilateral knee osteoarthritis groups. Dynamic and static balance and risk of fall were assessed using Biodex Stability System. In addition, Timed Up and Go test was used as a clinical test for balance. Results of this study illustrated that there were significant differences in balance (dynamic and static) and risk of fall between three groups. In addition, the main (most significant) difference was found to be between healthy group and moderate group. Furthermore, on clinical scoring of balance, the “Timed Up and Go” test, all three groups showed significant difference. In conclusion, bilateral knee osteoarthritis impaired the balance and increased the risk of fall, particularly in people with moderate knee osteoarthritis. PMID:24642715

Balance and risk of fall in individuals with bilateral mild and moderate knee osteoarthritis.

PubMed

Khalaj, Nafiseh; Abu Osman, Noor Azuan; Mokhtar, Abdul Halim; Mehdikhani, Mahboobeh; Wan Abas, Wan Abu Bakar

2014-01-01

Balance is essential for mobility and performing activities of daily living. People with knee osteoarthritis display impairment in knee joint proprioception. Thus, the aim of this study was to evaluate balance and risk of fall in individuals with bilateral mild and moderate knee osteoarthritis. Sixty subjects aged between 50 and 70 years volunteered in this study. They were categorized into three groups which were healthy (n = 20), mild (n = 20) and moderate (n = 20) bilateral knee osteoarthritis groups. Dynamic and static balance and risk of fall were assessed using Biodex Stability System. In addition, Timed Up and Go test was used as a clinical test for balance. Results of this study illustrated that there were significant differences in balance (dynamic and static) and risk of fall between three groups. In addition, the main (most significant) difference was found to be between healthy group and moderate group. Furthermore, on clinical scoring of balance, the "Timed Up and Go" test, all three groups showed significant difference. In conclusion, bilateral knee osteoarthritis impaired the balance and increased the risk of fall, particularly in people with moderate knee osteoarthritis.

The effects of eyeball exercise on balance ability and falls efficacy of the elderly who have experienced a fall: A single-blind, randomized controlled trial.

PubMed

Park, Jin-Hyuck

The purpose of this study was to investigate the effects of eyeball exercise on balance and fall efficacy of the elderly who have experienced a fall. Subjects were randomly assigned to the eyeball exercise group (n=30) or functional exercise group (n=31). All subjects received 30 sessions for 10 weeks. To identify the effects on balance, static and dynamic balance were measured using the center of pressure (CoP) measurement equipment and Timed Up and Go Test (TUGT) respectively. Fall efficacy was evaluated using the modified efficacy scale (MFES). The outcome measurements were performed before and after the 10 weeks training period. After 10 weeks, static balance, dynamic balance, and fall efficacy were significantly improved in both groups. Also, there were significant differences in the outcome measures between both groups (p<0.05). These results indicate that eyeball exercise is beneficial to improve the fall efficacy as well as the balance of the elderly compared with functional exercise. Eyeball exercise would be useful to improve balance and fall efficacy of the elderly who have experienced a fall. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Peripheral Neuropathy, Sensory Processing, and Balance in Survivors of Acute Lymphoblastic Leukemia.

PubMed

Varedi, Mitra; Lu, Lu; Howell, Carrie R; Partin, Robyn E; Hudson, Melissa M; Pui, Ching-Hon; Krull, Kevin R; Robison, Leslie L; Ness, Kirsten K; McKenna, Raymond F

2018-05-29

Purpose To compare peripheral nervous system function and balance between adult survivors of childhood acute lymphoblastic leukemia (ALL) and matched controls and to determine associations between peripheral neuropathy (PN) and limitations in static balance, mobility, walking endurance, and quality of life (QoL) among survivors. Patients and Methods Three hundred sixty-five adult survivors of childhood ALL and 365 controls with no cancer history completed assessments of PN (modified Total Neuropathy Score [mTNS]), static balance (Sensory Organization Test [SOT]), mobility (Timed Up and Go), walking endurance (6-minute walk test), QoL (Medical Outcomes Study 36-Item Short Form Survey), and visual-motor processing speed (Wechsler Adult Intelligence Scale). Results PN, but not impairments, in performance on SOT was more common in survivors than controls (41.4% v 9.5%, respectively; P < .001). In multivariable models, higher mTNS scores were associated with longer time to complete the Timed Up and Go (β = 0.15; 95% CI, 0.06 to 0.23; P < .001), shorter distance walked in 6 minutes (β = -4.39; 95% CI, -8.63 to -0.14; P = .04), and reduced QoL (β = -1.33; 95% CI, -1.79 to -0.87; P < .001 for physical functioning; β = -1.16; 95% CI, -1.64 to -0.67; P < .001 for role physical; and β = -0.88; 95% CI, -1.34 to -0.42; P < .001 for general health). Processing speed (β = 1.69; 95% CI, 0.98 to 2.40; P < .001), but not mTNS score, was associated with anterior-posterior sway on the SOT. Conclusion PN in long-term ALL survivors is associated with movement, including mobility and walking endurance, but not with static standing balance. The association between processing speed and sway suggests that static balance impairment in ALL survivors may be influenced by problems with CNS function, including the processing of sensory information.

Use of a Mobile Application to Help Students Develop Skills Needed in Solving Force Equilibrium Problems

NASA Astrophysics Data System (ADS)

Yang, Eunice

2016-02-01

This paper discusses the use of a free mobile engineering application (app) called Autodesk® ForceEffect™ to provide students assistance with spatial visualization of forces and more practice in solving/visualizing statics problems compared to the traditional pencil-and-paper method. ForceEffect analyzes static rigid-body systems using free-body diagrams (FBDs) and provides solutions in real time. It is a cost-free software that is available for download on the Internet. The software is supported on the iOS™, Android™, and Google Chrome™ platforms. It is easy to use and the learning curve is approximately two hours using the tutorial provided within the app. The use of ForceEffect has the ability to provide students different problem modalities (textbook, real-world, and design) to help them acquire and improve on skills that are needed to solve force equilibrium problems. Although this paper focuses on the engineering mechanics statics course, the technology discussed is also relevant to the introductory physics course.

Experimental investigations of an 0.0405 scale space shuttle configuration 3 orbiter to determine subsonic stability characteristics (OA21A/OA21B), volume 2

NASA Technical Reports Server (NTRS)

Cameron, B. W.; Ritschel, A. J.

1974-01-01

Aerodynamic investigations were conducted in a low speed wind tunnel from June 18 through June 25, 1973 on a 0.0405 scale -139B model Space Shuttle Vehicle orbiter. The purpose of the test was to investigate the longitudinal and lateral-directional subsonic aerodynamic characteristics of the proposed PRR Space Shuttle Orbiter. Emphasis was placed on component buildup effects, elevon, rudder, body flaps, rudder flare effectiveness, and canard and speed brake development. Angles of attack from -4 to 24 and angles of sideslip of -10 to 10 were tested. Static pressures were recorded on the base. The aerodynamic force balance results are presented in plotted and tabular form.

Results of investigations on a 0.0405 scale model ATP version of the NR-SSV orbiter in the North American Aeronautical Laboratory low speed wind tunnel

NASA Technical Reports Server (NTRS)

Mennell, R.; Vaughn, J. E.; Singellton, R.

1973-01-01

Experimental aerodynamic investigations were conducted on a scale model space shuttle vehicle (SSV) orbiter. The purpose of the test was to investigate the longitudinal and lateral-directional aerodynamic characteristics. Emphasis was placed on model component, wing-glove, and wing-body fairing effects, as well as elevon, aileron, and rudder control effectiveness. Angles of attack from - 5 deg to + 30 deg and angles of sideslip from - 5 deg to + 10 deg were tested. Static pressures were recorded on base, fuselage, and wing surfaces. Tufts and talc-kerosene flow visualization techniques were also utilized. The aerodynamic force balance results are presented in plotted and tabular form.

Multiphase-field model of small strain elasto-plasticity according to the mechanical jump conditions

NASA Astrophysics Data System (ADS)

Herrmann, Christoph; Schoof, Ephraim; Schneider, Daniel; Schwab, Felix; Reiter, Andreas; Selzer, Michael; Nestler, Britta

2018-04-01

We introduce a small strain elasto-plastic multiphase-field model according to the mechanical jump conditions. A rate-independent J_2 -plasticity model with linear isotropic hardening and without kinematic hardening is applied exemplary. Generally, any physically nonlinear mechanical model is compatible with the subsequently presented procedure. In contrast to models with interpolated material parameters, the proposed model is able to apply different nonlinear mechanical constitutive equations for each phase separately. The Hadamard compatibility condition and the static force balance are employed as homogenization approaches to calculate the phase-inherent stresses and strains. Several verification cases are discussed. The applicability of the proposed model is demonstrated by simulations of the martensitic transformation and quantitative parameters.

Siphon flows in isolated magnetic flux tubes. III - The equilibrium path of the flux-tube arch

NASA Technical Reports Server (NTRS)

Thomas, John H.; Montesinos, Benjamin

1990-01-01

It is shown how to calculate the equilibrium path of a thin magnetic flux tube in a stratified, nonmagnetic atmosphere when the flux tube contains a steady siphon flow. The equilbrium path of a static thin flux tube in an infinite stratified atmosphere generally takes the form of a symmetric arch of finite width, with the flux tube becoming vertical at either end of the arch. A siphon flow within the flux tube increases the curvature of the arched equilibrium path in order that the net magnetic tension force can balance the inertial force of the flow, which tries to straighten the flux tube. Thus, a siphon flow reduces the width of the arched equilibrium path, with faster flows producing narrower arches. The effect of the siphon flow on the equilibrium path is generally greater for flux tubes of weaker magnetic field strength. Examples of the equilibrium are shown for both isothemal and adiabatic siphon flows in thin flux tubes in an isothermal external atmosphere.

Effects of functional level on balance in children with Duchenne Muscular Dystrophy.

PubMed

Alkan, Halil; Mutlu, Akmer; Fırat, Tüzün; Bulut, Numan; Karaduman, Aynur Ayşe; Yılmaz, Öznur Tunca

2017-07-01

This study was planned to compare the static and dynamic balance in children with Duchenne Muscular Dystrophy (DMD) at different functional levels with each other and with healthy peers. Sixty nine children between the ages of 6 and 11 were included in this study where 52 of them were diagnosed with DMD in Level I (18 patients), Level II (17 patients), and Level III (17 patients) according to Brooke Functional Classification Scale and 17 of them healthy peers were included. In order to assess static and dynamic balance pediatric functional reach test (PFRT) and timed up and go test (TUGT) were used. When compared in terms of the TUGT, differences were found between all groups, i.e. Level 1 and 2, Level 2 and 3, Level 1 and 3, Healthy peers and Level 1, Healthy peers and Level 2, and Healthy peers and Level 3 (p < 0.0083). When compared in terms of the PFRT in the standing positions, there was difference between level 3 and healthy peers (p < 0.0083), but not between the other groups. We found poor functional level in DMD to affect the dynamic and static balance parameters in this study. The dynamic balance of a child with DMD at Level 3 is decreased to a third of a healthy peer. Copyright © 2017 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.

Vibrotactile perception thresholds at the sole of the foot: effects of contact force and probe indentation.

PubMed

Gu, Cheng; Griffin, Michael J

2012-05-01

When using vibrotactile thresholds to investigate neuropathy in the fingers, the indentation of a vibrating probe, and the force applied to a static surround around a vibrating probe, affect thresholds. This study was designed to investigate the effects on vibrotactile perception thresholds at the sole of the foot of probe indentation (i.e. height of a vibrating probe relative to a static surround) and the force applied to the static surround. Thresholds at 20 Hz (expected to be mediated by the NP I channel) and at 160 Hz (expected to be mediated by the Pacinian channel) were obtained at the hallux (i.e. greater toe) and the ball of the foot on 14 healthy subjects. In one condition, the height of the vibrating probe was varied to 0, 1, 2, 3, and 4 mm above a static surround with 4-N force applied to the surround. In a second condition, the force applied to the surround was varied to 1, 2, 3, 4, 5, and 6 N while using a probe height of 1mm. Thresholds at 20 Hz decreased with increasing probe height from 0 to 1 mm but showed no significant variation between 2, 3, and 4mm at either the hallux or the ball of the foot. Thresholds at 160 Hz decreased with increasing probe height from 0 to 4 mm at both the hallux and the ball of the foot. Thresholds at 20 Hz obtained with 1-N surround force were higher than thresholds obtained with 2 N, but there was no significant difference with surround forces from 2 to 6 N at either the hallux or the ball of the foot. Thresholds at 160 Hz were unaffected by variations in surround force at the ball of the foot but tended to decrease with increasing force at the hallux. It is concluded that a vibrating probe flush with a static surround, and a surround force in the range 2-4 N, are appropriate when measuring vibrotactile thresholds at the hallux and the ball of the foot with a 6-mm diameter contactor and a 2-mm gap to the static surround. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

Effect of cantilever geometry on the optical lever sensitivities and thermal noise method of the atomic force microscope.

PubMed

Sader, John E; Lu, Jianing; Mulvaney, Paul

2014-11-01

Calibration of the optical lever sensitivities of atomic force microscope (AFM) cantilevers is especially important for determining the force in AFM measurements. These sensitivities depend critically on the cantilever mode used and are known to differ for static and dynamic measurements. Here, we calculate the ratio of the dynamic and static sensitivities for several common AFM cantilevers, whose shapes vary considerably, and experimentally verify these results. The dynamic-to-static optical lever sensitivity ratio is found to range from 1.09 to 1.41 for the cantilevers studied - in stark contrast to the constant value of 1.09 used widely in current calibration studies. This analysis shows that accuracy of the thermal noise method for the static spring constant is strongly dependent on cantilever geometry - neglect of these dynamic-to-static factors can induce errors exceeding 100%. We also discuss a simple experimental approach to non-invasively and simultaneously determine the dynamic and static spring constants and optical lever sensitivities of cantilevers of arbitrary shape, which is applicable to all AFM platforms that have the thermal noise method for spring constant calibration.

THE EFFECTS OF DIFFERENT TRUNK INCLINATIONS ON BILATERAL TRUNK MUSCULAR ACTIVITIES, CENTRE OF PRESSURE AND FORCE EXERTIONS IN STATIC PUSHING POSTURES.

PubMed

Sanjaya, Kadek Heri; Lee, Soomin; Sriwarno, Andar Bagus; Shimomura, Yoshihito; Katsuura, Tetsuo

2014-06-01

In order to reconcile contradictory results from previous studies on manual pushing, a study was conducted to examine the effect of trunk inclination on muscular activities, centre of pressure (COP) and force exertion during static pushing. Ten subjects pushed at 0 degrees, 15 degrees, 30 degrees, and 45 degrees body inclinations in parallel and staggered feet stances. Wall and ground force plates measured pushing force, wall COP, vertical ground reaction force (GRF) and ground COP. Electromyogram data were recorded at 10 trunk muscle sites. Pushing force was found to increase with body inclination. GRF peaked at 15 degrees and reached its lowest level at the 45 degrees inclination. The lowest wall force plate standard deviation of COP displacement was found at the 30 degrees inclination. The lowest low back muscular activity was found at the 15 degrees and 30 degrees inclinations. Based on force exertion, muscular load, and stability, the 30 degrees body inclination was found to be the best posture for static pushing. This study also showed asymmetry in muscular activity and force exertion which has been received less attention in manual pushing studies. These findings will require further study.

Subsonic and supersonic static aerodynamic characteristics of a family of bulbous base cones measured with a magnetic suspension and balance system

NASA Technical Reports Server (NTRS)

Vlajinac, M.; Stephens, T.; Gilliam, G.; Pertsas, N.

1972-01-01

Results of subsonic and supersonic wind-tunnel tests with a magnetic balance and suspension system on a family of bulbous based cone configurations are presented. At subsonic speeds the base flow and separation characteristics of these configurations is shown to have a pronounced effect on the static data. Results obtained with the presence of a dummy sting are compared with support interference free data. Support interference is shown to have a substantial effect on the measured aerodynamic coefficient.

Simulation of the effects of different pilot helmets on neck loading during air combat.

PubMed

Mathys, R; Ferguson, S J

2012-09-21

New generation pilot helmets with mounted devices enhance the capabilities of pilots substantially. However, the additional equipment increases the helmet weight and shifts its center of mass forward. Two helmets with different mass properties were modeled to simulate their effects on the pilot's neck. A musculoskeletal computer model was used, with the methods of inverse dynamics and static optimization, to compute the muscle activations and joint reaction forces for a given range of quasi-static postures at various accelerations experienced during air combat. Head postures which induce much higher loads on the cervical spine than encountered in a neutral position could be identified. The increased weight and the forward shift of the center of mass of a new generation helmet lead to higher muscle activations and higher joint reaction loads over a wide range of head and neck movements. The muscle activations required to balance the head and neck in extreme postures increased the compressive force at the T1-C7 level substantially, while in a neutral posture the muscle activations remained low. The lateral neck muscles can reach activations of 100% and cause compressive joint forces up to 1100N during extensive rotations and extensions at high 'vertical' accelerations (Gz). The calculated values have to be interpreted with care as the model has not been validated. Nevertheless, this systematic analysis could separate the effects of head posture, acceleration and helmet mass on neck loading. More reliable data about mass properties and muscle morphometry with a more detailed motion analysis would help to refine the existing model. Copyright © 2012 Elsevier Ltd. All rights reserved.

Sensorimotor Control of the Shoulder in Professional Volleyball Players with Isolated Infraspinatus Muscle Atrophy.

PubMed

Contemori, Samuele; Biscarini, Andrea; Botti, Fabio Massimo; Busti, Daniele; Panichi, Roberto; Pettorossi, Vito Enrico

2017-06-12

Isolated infraspinatus muscle atrophy (IIMA) only affects the hitting shoulder of overhead-activity athletes, and is caused by suprascapular nerve neuropathy. No study has assessed the static and dynamic stability of the shoulder in overhead professional athletes with IIMA to reveal possible shoulder sensorimotor alterations. To assess the shoulder static stability, dynamic stability, and strength in professional volleyball players with IIMA and in healthy control players. Cross-sectional study. Research laboratory. Twenty-four male professional volleyball players (12 players with diagnosed IIMA and 12 healthy players) recruited from local volleyball teams. Static stability was evaluated with two independent force platforms and dynamic stability was assessed with the "Upper Quarter Y Balance Test". The static stability assessment was conducted in different support (single hand and both hand) and vision (open and closed eyes) conditions. Data from each test were analyzed with ANOVA and paired t-test models, to highlight statistical differences within and between groups. In addition to reduced abduction and external rotation strength, athletes with IIMA consistently demonstrated significant less static (P < 0.001) and dynamic stability (P < 0,001), compared with the contralateral shoulder and with healthy athletes. Closed eyes condition significantly enhanced the static stability deficit of the shoulder with IIMA (P = 0.039 and P = 0.034 for both hand and single hand support, respectively), but had no effect in healthy contralateral and healthy players' shoulders. This study highlights an impairment of the sensorimotor control system of the shoulder with IIMA, which likely results from both proprioceptive and strength deficits. This condition could yield subtle alteration in the functional use of the shoulder and predispose it to acute or overuse injuries. The results of this study may help athletic trainers and physical/physiotherapists to prevent shoulder injuries and create specific proprioceptive and neuromuscular training programs.

Inducer Hydrodynamic Load Measurement Devices

NASA Technical Reports Server (NTRS)

Skelley, Stephen E.; Zoladz, Thomas F.

2002-01-01

Marshall Space Flight Center (MSFC) has demonstrated two measurement devices for sensing and resolving the hydrodynamic loads on fluid machinery. The first - a derivative of the six component wind tunnel balance - senses the forces and moments on the rotating device through a weakened shaft section instrumented with a series of strain gauges. This "rotating balance" was designed to directly measure the steady and unsteady hydrodynamic loads on an inducer, thereby defining both the amplitude and frequency content associated with operating in various cavitation modes. The second device - a high frequency response pressure transducer surface mounted on a rotating component - was merely an extension of existing technology for application in water. MSFC has recently completed experimental evaluations of both the rotating balance and surface-mount transducers in a water test loop. The measurement bandwidth of the rotating balance was severely limited by the relative flexibility of the device itself, resulting in an unexpectedly low structural bending mode and invalidating the higher frequency response data. Despite these limitations, measurements confirmed that the integrated loads on the four-bladed inducer respond to both cavitation intensity and cavitation phenomena. Likewise, the surface-mount pressure transducers were subjected to a range of temperatures and flow conditions in a non-rotating environment to record bias shifts and transfer functions between the transducers and a reference device. The pressure transducer static performance was within manufacturer's specifications and dynamic response accurately followed that of the reference.

Inducer Hydrodynamic Load Measurement Devices

NASA Technical Reports Server (NTRS)

Skelley, Stephen E.; Zoladz, Thomas F.; Turner, Jim (Technical Monitor)

2002-01-01

Marshall Space Flight Center (MSFC) has demonstrated two measurement devices for sensing and resolving the hydrodynamic loads on fluid machinery. The first - a derivative of the six-component wind tunnel balance - senses the forces and moments on the rotating device through a weakened shaft section instrumented with a series of strain gauges. This rotating balance was designed to directly measure the steady and unsteady hydrodynamic loads on an inducer, thereby defining both the amplitude and frequency content associated with operating in various cavitation modes. The second device - a high frequency response pressure transducer surface mounted on a rotating component - was merely an extension of existing technology for application in water. MSFC has recently completed experimental evaluations of both the rotating balance and surface-mount transducers in a water test loop. The measurement bandwidth of the rotating balance was severely limited by the relative flexibility of the device itself, resulting in an unexpectedly low structural bending mode and invalidating the higher-frequency response data. Despite these limitations, measurements confirmed that the integrated loads on the four-bladed inducer respond to both cavitation intensity and cavitation phenomena. Likewise, the surface-mount pressure transducers were subjected to a range of temperatures and flow conditions in a non-rotating environment to record bias shifts and transfer functions between the transducers and a reference device. The pressure transducer static performance was within manufacturer's specifications and dynamic response accurately followed that of the reference.

Cardiovascular control during concomitant dynamic leg exercise and static arm exercise in humans

PubMed Central

Strange, S

1999-01-01

Skeletal muscle blood flow is thought to be determined by a balance between sympathetic vasoconstriction and metabolic vasodilatation. The purpose of this study was to assess the importance of high levels of sympathetic vasoconstrictor activity in control of blood flow to human skeletal muscle during dynamic exercise.Muscle sympathetic nerve activity to the exercising leg was increased by static or static ischaemic arm exercise added to on-going dynamic leg exercise. Ten subjects performed light (20 W) or moderate (40 W) dynamic knee extension for 6 min with one leg alone or concomitant with bilateral static handgrip at 20% of maximal voluntary contraction force with or without forearm muscle ischaemia or post-exercise forearm muscle ischaemia.Muscle sympathetic nerve activity was measured by microneurography (peroneal nerve) and leg muscle blood flow by a constant infusion thermodilution technique (femoral vein).Activation of an exercise pressor reflex from the arms, causing a 2- to 4-fold increase in muscle sympathetic nerve activity and a 15–32% increase in mean arterial blood pressure, did not affect blood flow to the dynamically exercising leg muscles at any level of leg exercise. Leg vascular conductance was reduced in line with the higher perfusion pressure.The results demonstrate that the vasoconstrictor effects of high levels of muscle sympathetic nerve activity does not affect blood flow to human skeletal muscle exercising at moderate intensities. One question remaining is whether the observed decrease in muscle vascular conductance is the result of sympathetic vasoconstriction or metabolic autoregulation of muscle blood flow. PMID:9831733

Musculoskeletal Modeling of the Lumbar Spine to Explore Functional Interactions between Back Muscle Loads and Intervertebral Disk Multiphysics

PubMed Central

Toumanidou, Themis; Noailly, Jérôme

2015-01-01

During daily activities, complex biomechanical interactions influence the biophysical regulation of intervertebral disks (IVDs), and transfers of mechanical loads are largely controlled by the stabilizing action of spine muscles. Muscle and other internal forces cannot be easily measured directly in the lumbar spine. Hence, biomechanical models are important tools for the evaluation of the loads in those tissues involved in low-back disorders. Muscle force estimations in most musculoskeletal models mainly rely, however, on inverse calculations and static optimizations that limit the predictive power of the numerical calculations. In order to contribute to the development of predictive systems, we coupled a predictive muscle model with the passive resistance of the spine tissues, in a L3–S1 musculoskeletal finite element model with osmo-poromechanical IVD descriptions. The model included 46 fascicles of the major back muscles that act on the lower spine. The muscle model interacted with activity-related loads imposed to the osteoligamentous structure, as standing position and night rest were simulated through distributed upper body mass and free IVD swelling, respectively. Calculations led to intradiscal pressure values within ranges of values measured in vivo. Disk swelling led to muscle activation and muscle force distributions that seemed particularly appropriate to counterbalance the anterior body mass effect in standing. Our simulations pointed out a likely existence of a functional balance between stretch-induced muscle activation and IVD multiphysics toward improved mechanical stability of the lumbar spine understanding. This balance suggests that proper night rest contributes to mechanically strengthen the spine during day activity. PMID:26301218

Implementation of the vortex force formalism in the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system for inner shelf and surf zone applications

USGS Publications Warehouse

Kumar, Nirnimesh; Voulgaris, George; Warner, John C.; Olabarrieta, Maitane

2012-01-01

Model results from the planar beach case show good agreement with depth-averaged analytical solutions and with theoretical flow structures. Simulation results for the DUCK' 94 experiment agree closely with measured profiles of cross-shore and longshore velocity data from and . Diagnostic simulations showed that the nonlinear processes of wave roller generation and wave-induced mixing are important for the accurate simulation of surf zone flows. It is further recommended that a more realistic approach for determining the contribution of wave rollers and breaking induced turbulent mixing can be formulated using non-dimensional parameters which are functions of local wave parameters and the beach slope. Dominant terms in the cross-shore momentum balance are found to be the quasi-static pressure gradient and breaking acceleration. In the alongshore direction, bottom stress, breaking acceleration, horizontal advection and horizontal vortex forces dominate the momentum balance. The simulation results for the bar/rip channel morphology case clearly show the ability of the modeling system to reproduce horizontal and vertical circulation patterns similar to those found in laboratory studies and to numerical simulations using the radiation stress representation. The vortex force term is found to be more important at locations where strong flow vorticity interacts with the wave-induced Stokes flow field. Outside the surf zone, the three-dimensional model simulations of wave-induced flows for non-breaking waves closely agree with flow observations from MVCO, with the vertical structure of the simulated flow varying as a function of the vertical viscosity as demonstrated by Lentz et al. (2008).

Should Ballet Dancers Vary Postures and Underfoot Surfaces When Practicing Postural Balance?

PubMed

Steinberg, Nili; Waddington, Gordon; Adams, Roger; Karin, Janet; Tirosh, Oren

2018-01-01

Postural balance (PB) is an important component skill for professional dancers. However, the effects of different types of postures and different underfoot surfaces on PB have not adequately been addressed. The main aim of this study was to investigate the effect of different conditions of footwear, surfaces, and standing positions on static and dynamic PB ability of young ballet dancers. A total of 36 male and female young professional ballet dancers (aged 14-19 years) completed static and dynamic balance testing, measured by head and lumbar accelerometers, while standing on one leg in the turnout position, under six different conditions: (1) "relaxed" posture; (2) "ballet" posture; (3) barefoot; (4) ballet shoes with textured insoles; (5) barefoot on a textured mat; and (6) barefoot on a spiky mat. A condition effect was found for static and dynamic PB. Static PB was reduced when dancers stood in the ballet posture compared with standing in the relaxed posture and when standing on a textured mat and on a spiky mat (p < .05), and static PB in the relaxed posture was significantly better than PB in all the other five conditions tested. Dynamic PB was significantly better while standing in ballet shoes with textured insoles and when standing on a spiky mat compared with all other conditions (p < .05). The practical implications derived from this study are that both male and female dancers should try to be relaxed in their postural muscles when practicing a ballet aligned position, including dance practice on different types of floors and on different types of textured/spiky materials may result in skill transfer to practice on normal floor surfaces, and both static and dynamic PB exercises should be assessed and generalized into practical dance routines.

An Experimental Investigation on the Static Equilibria and Dynamics of Liquid Bridges. Degree Awarded by the University of Alabama, 1997

NASA Technical Reports Server (NTRS)

Resnick, Andrew Howard

1997-01-01

A liquid bridge is a volume of liquid held between two or more solid supports. In the case of small disk supports with a sharp edge, the contact line between the bridge and the support disk will be anchored along the edge of the disk. For these cases the solid presents a geometrical singularity and the contact angle is indeterminate within a given range. This dissertation presents research conducted on liquid bridges with anchored contact lines. The three major topics covered are: determining the role of support geometry on static equilibria, liquid bridge dynamical behavior, and forces exerted by a liquid bridge on a support structure. The work was primarily experimental and conducted in a "Plateau tank" that allowed for the simulation of equivalent low-gravity conditions. The main thrust of the experimental work involved the use of a high resolution optical measurement system for imaging the dynamic zone shape, measurement of the static and dynamic contact angles and non-invasive analysis of excited surface modes. The liquid bridge was manipulated by computer controlled linear actuators which allowed precise control over the physical characteristics of the bridge. Experiments have been carried out to locate a bifurcation point along the maximum volume axisymmetric stability margin. Below the critical slenderness the bifurcation from an axisymmetric to a stable nonaxisymmetric configuration is supercritical. However, above this critical slenderness, the bifurcation is subcritical. A series of experiments analyzed the effect on axisymmetric bridge stability by using support disks of different radii, The shape behavior as transition points were approached, as well as the limiting case of a vanishing support radius was investigated. Experiments were performed to determine the resonant frequencies of axisymmetric bridges subject to lateral vibrations. Anomolous results led to a series of experiments to characterize nonlinearities present in the dynamic bridge shape. Finally, an attempt was made to experimentally measure the force exerted by the bridge on the lower support disk. This was done through use of a force balance apparatus. Particular attention was paid to the behavior of the bridge as the minimum volume stability limit was approached.

Effects of ankle strengthening exercise program on an unstable supporting surface on proprioception and balance in adults with functional ankle instability.

PubMed

Ha, Sun-Young; Han, Jun-Ho; Sung, Yun-Hee

2018-04-01

The present study was conducted to investigate the effect of ankle strengthening exercise applied on unstable supporting surfaces on the proprioceptive sense and balance in adults with functional ankle instability. As for the study method, 30 adults with functional ankle instability were randomly assigned to an ankle strengthening exercise group and a stretching group on unstable supporting surfaces, and the interventions were implemented for 40 min. Before and after the interventions, a digital dual inclinometer was used to measure the proprioceptive sense of the ankle, the Balancia program was used to measure static balance ability, and the functional reach test was used to measure dynamic balance ability. In the results, both proprioceptive sense and static dynamic balance ability were significantly different between before and after the intervention in the experimental group ( P <0.05). When such results are put together, it can be seen that ankle strengthening exercise applied on unstable supporting surfaces may be presented as an effective treatment method for enhancing the proprioceptive sense and balance ability in adults with functional ankle instability.

The Effects of Local Vibration on Balance, Power, and Self-Reported Pain After Exercise.

PubMed

Custer, Lisa; Peer, Kimberly S; Miller, Lauren

2017-05-01

Muscle fatigue and acute muscle soreness occur after exercise. Application of a local vibration intervention may reduce the consequences of fatigue and soreness. To examine the effects of a local vibration intervention after a bout of exercise on balance, power, and self-reported pain. Single-blind crossover study. Laboratory. 19 healthy, moderately active subjects. After a 30-min bout of full-body exercise, subjects received either an active or a sham vibration intervention. The active vibration intervention was performed bilaterally over the muscle bellies of the triceps surae, quadriceps, hamstrings, and gluteals. At least 1 wk later, subjects repeated the bout, receiving the other vibration intervention. Static balance, dynamic balance, power, and self-reported pain were measured at baseline, after the vibration intervention, and 24 h postexercise. After the bout of exercise, subjects had reduced static and dynamic balance and increased self-reported pain regardless of vibration intervention. There were no differences between outcome measures between the active and sham vibration conditions. The local vibration intervention did not affect balance, power, or self-reported pain.

Determination of the static friction coefficient from circular motion

NASA Astrophysics Data System (ADS)

Molina-Bolívar, J. A.; Cabrerizo-Vílchez, M. A.

2014-07-01

This paper describes a physics laboratory exercise for determining the coefficient of static friction between two surfaces. The circular motion of a coin placed on the surface of a rotating turntable has been studied. For this purpose, the motion is recorded with a high-speed digital video camera recording at 240 frames s-1, and the videos are analyzed using Tracker video-analysis software, allowing the students to dynamically model the motion of the coin. The students have to obtain the static friction coefficient by comparing the centripetal and maximum static friction forces. The experiment only requires simple and inexpensive materials. The dynamics of circular motion and static friction forces are difficult for many students to understand. The proposed laboratory exercise addresses these topics, which are relevant to the physics curriculum.

Acute Effects of the Different Intensity of Static Stretching on Flexibility and Isometric Muscle Force.

PubMed

Kataura, Satoshi; Suzuki, Shigeyuki; Matsuo, Shingo; Hatano, Genki; Iwata, Masahiro; Yokoi, Kazuaki; Tsuchida, Wakako; Banno, Yasuhiro; Asai, Yuji

2017-12-01

Kataura, S, Suzuki, S, Matsuo, S, Hatano, G, Iwata, M, Yokoi, K, Tsuchida, W, Banno, Y, and Asai, Y. Acute effects of the different intensity of static stretching on flexibility and isometric muscle force. J Strength Cond Res 31(12): 3403-3410, 2017-In various fields, static stretching is commonly performed to improve flexibility, whereas the acute effects of different stretch intensities are unclear. Therefore, we investigated the acute effects of different stretch intensities on flexibility and muscle force. Eighteen healthy participants (9 men and 9 women) performed 180-second static stretches of the right hamstrings at 80, 100, and 120% of maximum tolerable intensity without stretching pain, in random order. The following outcomes were assessed as markers of lower limb function and flexibility: static passive torque (SPT), range of motion (ROM), passive joint (muscle-tendon) stiffness, passive torque (PT) at onset of pain, and isometric muscle force. Static passive torque was significantly decreased after all stretching intensities (p ≤ 0.05). Compared with before stretching at 100 and 120% intensities, ROM and PT were significantly increased after stretching (p ≤ 0.05), and passive stiffness (p = 0.05) and isometric muscle force (p ≤ 0.05) were significantly decreased. In addition, ROM was significantly greater after stretching at 100 and 120% than at 80%, and passive stiffness was significantly lower after 120% than after 80% (p ≤ 0.05). However, all measurements except SPT were unchanged after 80% intensity. There was a weak positive correlation between the intensities of stretching and the relative change for SPT (p ≤ 0.05), a moderate positive correlation with ROM (p ≤ 0.05), and a moderate positive correlation with passive stiffness (p ≤ 0.05). These results indicate that static stretching at greater intensity is more effective for increasing ROM and decreasing passive muscle-tendon stiffness.

Aeroservoelastic Wind-Tunnel Tests of a Free-Flying, Joined-Wing SensorCraft Model for Gust Load Alleviation

NASA Technical Reports Server (NTRS)

Scott, Robert C.; Castelluccio, Mark A.; Coulson, David A.; Heeg, Jennifer

2011-01-01

A team comprised of the Air Force Research Laboratory (AFRL), Boeing, and the NASA Langley Research Center conducted three aeroservoelastic wind-tunnel tests in the Transonic Dynamics Tunnel to demonstrate active control technologies relevant to large, exible vehicles. In the first of these three tests, a full-span, aeroelastically scaled, wind-tunnel model of a joined-wing SensorCraft vehicle was mounted to a force balance to acquire a basic aerodynamic data set. In the second and third tests, the same wind-tunnel model was mated to a new, two-degree-of-freedom, beam mount. This mount allowed the full-span model to translate vertically and pitch. Trimmed flight at -10% static margin and gust load alleviation were successfully demonstrated. The rigid body degrees of freedom required that the model be own in the wind tunnel using an active control system. This risky mode of testing necessitated that a model arrestment system be integrated into the new mount. The safe and successful completion of these free-flying tests required the development and integration of custom hardware and software. This paper describes the many systems, software, and procedures that were developed as part of this effort. The balance and free ying wind-tunnel tests will be summarized. The design of the trim and gust load alleviation control laws along with the associated results will also be discussed.

A microNewton thrust stand for average thrust measurement of pulsed microthruster.

PubMed

Zhou, Wei-Jing; Hong, Yan-Ji; Chang, Hao

2013-12-01

A torsional thrust stand has been developed for the study of the average thrust for microNewton pulsed thrusters. The main body of the thrust stand mainly consists of a torsional balance, a pair of flexural pivots, a capacitive displacement sensor, a calibration assembly, and an eddy current damper. The behavior of the stand was thoroughly studied. The principle of thrust measurement was analyzed. The average thrust is determined as a function of the average equilibrium angle displacement of the balance and the spring stiffness. The thrust stand has a load capacity up to 10 kg, and it can theoretically measure the force up to 609.6 μN with a resolution of 24.4 nN. The static calibrations were performed based on the calibration assembly composed of the multiturn coil and the permanent magnet. The calibration results demonstrated good repeatability (less than 0.68% FSO) and good linearity (less than 0.88% FSO). The assembly of the multiturn coil and the permanent magnet was also used as an exciter to simulate the microthruster to further research the performance of the thrust stand. Three sets of force pulses at 17, 33.5, and 55 Hz with the same amplitude and pulse width were tested. The repeatability error at each frequency was 7.04%, 1.78%, and 5.08%, respectively.

Pattern of age-associated decline of static and dynamic balance in community-dwelling older women.

PubMed

Takeshima, Nobuo; Islam, Mohammod M; Rogers, Michael E; Koizumi, Daisuke; Tomiyama, Naoki; Narita, Makoto; Rogers, Nicole L

2014-07-01

Falling is the leading cause of injury-related deaths in older adults, and a loss of balance is often the precursor to a fall. However, little is known about the rate at which balance declines with age. The objective of the present study was to determine whether there is an age-associated decline in static (SB) and/or dynamic (DB) balance in community-dwelling older women. SB and DB were determined in 971 older women. Intraclass correlation coefficients (ICC) were used to determine test-retest reliability. Sway velocity was used to measure SB standing on a platform and foam with eyes open and closed. DB was characterized by limits of stability (LOS) that measured end-point excursion (EXE) and maximum excursion (MXE) of the body's center of pressure. ICC for EXE and MXE for the LOS test were excellent (EPE = 0.96, MXE = 0.96). ICC for SB tests, except for the eyes open firm surface condition (ICC = 0.10), showed a high level of reproducibility (ICC = 0.88 and 0.90). Relationships existed between age and SB (r = 0.31, P < 0.001), and between age and DB (r = -0.46--0.48, P < 0.001). The rate of decline for both DB and SB was approximately 1% per year. Age was significantly associated with all balance measures. DB got significantly lower with advancing age until 80 years, and then plateaued. SB did not decline with age until 80 years, and then decreased significantly thereafter. Although large individual variation was found with balance ability, an age-related decline was found with both dynamic and static balance for Japanese older women. © 2013 Japan Geriatrics Society.

An eight-legged tactile sensor to estimate coefficient of static friction.

PubMed

Wei Chen; Rodpongpun, Sura; Luo, William; Isaacson, Nathan; Kark, Lauren; Khamis, Heba; Redmond, Stephen J

2015-08-01

It is well known that a tangential force larger than the maximum static friction force is required to initiate the sliding motion between two objects, which is governed by a material constant called the coefficient of static friction. Therefore, knowing the coefficient of static friction is of great importance for robot grippers which wish to maintain a stable and precise grip on an object during various manipulation tasks. Importantly, it is most useful if grippers can estimate the coefficient of static friction without having to explicitly explore the object first, such as lifting the object and reducing the grip force until it slips. A novel eight-legged sensor, based on simplified theoretical principles of friction is presented here to estimate the coefficient of static friction between a planar surface and the prototype sensor. Each of the sensor's eight legs are straight and rigid, and oriented at a specified angle with respect to the vertical, allowing it to estimate one of five ranges (5 = 8/2 + 1) that the coefficient of static friction can occupy. The coefficient of friction can be estimated by determining whether the legs have slipped or not when pressed against a surface. The coefficients of static friction between the sensor and five different materials were estimated and compared to a measurement from traditional methods. A least-squares linear fit of the sensor estimated coefficient showed good correlation with the reference coefficient with a gradient close to one and an r(2) value greater than 0.9.

Research of the BWS system for lower extremity rehabilitation robot.

PubMed

Zhang, Xiao; Li, Weida; Li, Juan; Cai, Xiaowei

2017-07-01

Body weight support (BWS) system is increasingly used in conjunction with treadmills to assist the patients with neurological impairments. Owing to lower limbs of the patients unable to bear the whole weight during the rehabilitation training, some weight can be removed to help the patients recover the basic walking ability gradually. Therefore, considering the man-machine relationship and the effects of the rehabilitation, a wire-driven BWS system is designed. The main unit of the system is an active closed-loop controlled drive to generate the exact desired force. The force acted on the body is through the adjustment of the length of the rope which is connected to the harness worn by the patient. The structure designed in the research is easy to operate to realize the goal of the rehabilitation. To verify the effectiveness and practicability of the BWS system, some experiments have been curried out. From the results, not only the constant unloading force can be realized, but also the response time is limited in a small range which can bring a positive effect on correcting gait, improving balance and reducing muscle spasms. Also, compared to the traditional body weight support system, such as static system or passive elastic system, it has the advantages of the fast response, small errors and constant unloading force.

Competing influence of greenhouse warming and aerosols on thermodynamic and dynamic controls of the Asian monoon

NASA Astrophysics Data System (ADS)

Lau, W. K. M.; Kim, K. M.

2016-12-01

In this study, we investigate the relative roles of greenhouse gas (GHG) warming and aerosol forcing on the Asian monsoon. A baseline for global warming response is established from analysis of the multi-model mean (MMM) of 33 CMIP5 models based on a 140-year integration of 1% per year CO2 experiment. The relative roles of GHG warming and aerosol forcing on Asian monsoon precipitation changes are then assessed based on the 20th century historical runs, under a) all-forcing including GHG and aerosols, and b) GHG only. Results show that under CO2 warming, the Asian monsoon atmosphere can get wetter, no change, or drier regionally, depending on changes in moisture availability, atmospheric moist static stability, and topography. Rainfall is generally increased over the Asian monsoon tropical land and adjacent oceanic regions. However, in subtropical and extratropical land region over East Asia, monsoon rainfall increase is minimal, unchanged, or even suppressed. This is due to increased subsidence, and reduction of mid-tropopsheric relative humidity from an enhanced Hadley circulation, which weakens the monsoon meridional overturning circulation. These create the apparent paradox of a monsoon with increased rainfall, but weakened monsoon circulation under GHG warming. The monsoon response to GHG-only forcing in the historical run is similar to the baseline. On the other hand, as inferred from the difference of the all-forcing and the GHG-only runs, aerosols through solar dimming (SDM) and semi-direct effects suppress monsoon precipitation, causing a further weakening of the Asian monsoon. A scale analysis of precipitation shows that under a hypothetical GHG-only forcing in the past century, the "effective precipitation efficiency" (EPE) would have to be strongly reduced in order to achieve water balance between dynamics and thermodynamics. Under all-forcing (including aerosol), the reduction in EPE is much smaller. Here, the weaker monsoon circulation needed for water balance can be achieved via the aerosol semi-direct effect in increased atmospheric stability, and aerosol solar dimming effect in lessening the GHG induced land-sea thermal contrast between Eurasia and the surrounding oceans.

The effect of shoe type on static and dynamic balance during treadmill walking in young healthy women.

PubMed

Kim, Mi-Kyoung; Kong, Byung-Sun; Yoo, Kyung-Tae

2017-09-01

[Purpose] The purpose of this study was to analyze the effect of various shoes on the static and dynamic balance of young women in their 20s. [Subjects and Methods] The subjects of the study were 15 healthy young women and repeated measured design. The subjects walked on the treadmill at a speed of 4 km/h for 30 minutes wearing three types of shoes: sneaker, rain boots, and combat boots. Balance was measured by a Romberg test and a limits of stability test. One-way ANOVA was used for statistical analysis. [Results] As the results of the Romberg test, the main effect of time was shown in the EO-COG area, EO-COG length, and EO-COG velocity. As the results of the limits of stability test, the main effects of time in LT, RT, FW, and total. There were significant differences in the LT in the sneaker group, the rain boots group, and the LT and RT in the combat boots group between the pre- and post-test. [Conclusion] The characteristics of shoes such as the materials, hardness, and thickness of the soles, the coefficient of friction of the outsoles, and the collar height affected the static and dynamic balance.

The effect of shoe type on static and dynamic balance during treadmill walking in young healthy women

PubMed Central

Kim, Mi-Kyoung; Kong, Byung-Sun; Yoo, Kyung-Tae

2017-01-01

[Purpose] The purpose of this study was to analyze the effect of various shoes on the static and dynamic balance of young women in their 20s. [Subjects and Methods] The subjects of the study were 15 healthy young women and repeated measured design. The subjects walked on the treadmill at a speed of 4 km/h for 30 minutes wearing three types of shoes: sneaker, rain boots, and combat boots. Balance was measured by a Romberg test and a limits of stability test. One-way ANOVA was used for statistical analysis. [Results] As the results of the Romberg test, the main effect of time was shown in the EO-COG area, EO-COG length, and EO-COG velocity. As the results of the limits of stability test, the main effects of time in LT, RT, FW, and total. There were significant differences in the LT in the sneaker group, the rain boots group, and the LT and RT in the combat boots group between the pre- and post-test. [Conclusion] The characteristics of shoes such as the materials, hardness, and thickness of the soles, the coefficient of friction of the outsoles, and the collar height affected the static and dynamic balance. PMID:28932007

Effects of brisk walking on static and dynamic balance, locomotion, body composition, and aerobic capacity in ageing healthy active men.

PubMed

Paillard, T; Lafont, C; Costes-Salon, M C; Rivière, D; Dupui, P

2004-10-01

This work analyses the short-term physiological and neurophysiological effects of a brisk walking programme in ageing, healthy, active men. Twenty-one men 63 to 72 years of age were recruited and separated into 2 groups. One group performed a walking programme (WP) (n = 11) and another served as control (C) group (n = 10). The walking programme lasted for twelve weeks and included five sessions per week. Several parameters were assessed before and after the programme for the WP group. The same tests were performed (separated by twelve weeks) in group C. During each assessment, the subjects were put through static and dynamic balance tests, spatio-temporal gait analysis, body composition measurements and determination of aerobic capacity and bone mineral density. The statistic analysis showed a significant improvement in dynamic balance performance, especially in lateral sway when the subjects kept their eyes open, an increase of VO(2) max and loss of fat mass in the WP group. However, no alterations appeared in spatiotemporal gait characteristics, static balance performance, lean mass or bone mineral density (total body and hip). According to these results, this walking programme may have positive effects on preventing ageing subjects from falling.

Results from the balance rehabilitation unit in benign paroxysmal positional vertigo.

PubMed

Kasse, Cristiane Akemi; Santana, Graziela Gaspar; Scharlach, Renata Coelho; Gazzola, Juliana Maria; Branco, Fátima Cristina Barreiro; Doná, Flávia

2010-01-01

Posturography is a useful new tool to study the influence of vestibular diseases on balance. to compare the results from the Balance Rehabilitation Unit (BRU) static posturography in elderly patients with Benign Paroxysmal Positional Vertigo (BPPV), before and after Epley's maneuver. a prospective study of 20 elderly patients with a diagnosis of BPPV. The patients underwent static posturography and the limit of stability (LE) and ellipse area were measured. We also applied the Dizziness Handicap Inventory (DHI) questionnaire to study treatment effectiveness. 80% were females, with a mean age of 68.15 years. After the maneuver, the LE increased significantly (p=0.001). The elliptical area of somatosensory, visual and vestibular conflicts (2,7,8,9 situations) in BRU and the DHI scores decreased significantly (p<0.05) after treatment. the study suggests that elderly patients with BPPV may present static postural control impairment and that the maneuver is effective for the remission of symptoms, to increase in the stability and improvement in postural control in situations of visual, somatosensory and vestibular conflicts.

THE RELATIONSHIP BETWEEN VARIOUS MODES OF SINGLE LEG POSTURAL CONTROL ASSESSMENT

PubMed Central

Schmitz, Randy

2012-01-01

Purpose/Background: While various techniques have been developed to assess the postural control system, little is known about the relationship between single leg static and functional balance. The purpose of the current study was to determine the relationship between the performance measures of several single leg postural stability tests. Methods: Forty six recreationally active college students (17 males, 29 females, 21±3 yrs, 173±10 cm) performed six single leg tests in a counterbalanced order: 1) Firm Surface-Eyes Open, 2) Firm Surface-Eyes Closed, 3) Multiaxial Surface-Eyes Open, 4) Multiaxial Surface-Eyes Closed, 5) Star Excursion Balance Test (posterior medial reach), 6) Single leg Hop-Stabilization Test. Bivariate correlations were conducted between the six outcome variables. Results: Mild to moderate correlations existed between the static tests. No significant correlations existed involving either of the functional tests. Conclusions: The results indicate that while performance of static balance tasks are mildly to moderately related, they appear to be unrelated to functional reaching or hopping movements, supporting the utilization of a battery of tests to determine overall postural control performance. Level of Evidence: 3b PMID:22666640

Adhesion of Lunar Dust

NASA Astrophysics Data System (ADS)

Walton, Otis R.

2007-04-01

This paper reviews the physical characteristics of lunar dust and the effects of various fundamental forces acting on dust particles on surfaces in a lunar environment. There are transport forces and adhesion forces after contact. Mechanical forces (i.e., from rover wheels, astronaut boots and rocket engine blast) and static electric effects (from UV photo-ionization and/or tribo-electric charging) are likely to be the major contributors to the transport of dust particles. If fine regolith particles are deposited on a surface, then surface energy-related (e.g., van der Walls) adhesion forces and static-electric-image forces are likely to be the strongest contributors to adhesion. Some measurement techniques are offered to quantify the strength of adhesion forces. And finally some dust removal techniques are discussed.

Adhesion of Lunar Dust

NASA Technical Reports Server (NTRS)

Walton, Otis R.

2007-01-01

This paper reviews the physical characteristics of lunar dust and the effects of various fundamental forces acting on dust particles on surfaces in a lunar environment. There are transport forces and adhesion forces after contact. Mechanical forces (i.e., from rover wheels, astronaut boots and rocket engine blast) and static electric effects (from UV photo-ionization and/or tribo-electric charging) are likely to be the major contributors to the transport of dust particles. If fine regolith particles are deposited on a surface, then surface energy-related (e.g., van der Walls) adhesion forces and static-electric-image forces are likely to be the strongest contributors to adhesion. Some measurement techniques are offered to quantify the strength of adhesion forces. And finally some dust removal techniques are discussed.

Dynamic balance and stepping versus tai chi training to improve balance and stepping in at-risk older adults.

PubMed

Nnodim, Joseph O; Strasburg, Debra; Nabozny, Martina; Nyquist, Linda; Galecki, Andrzej; Chen, Shu; Alexander, Neil B

2006-12-01

To compare the effect of two 10-week balance training programs, Combined Balance and Step Training (CBST) versus tai chi (TC), on balance and stepping measures. Prospective intervention trial. Local senior centers and congregate housing facilities. Aged 65 and older with at least mild impairment in the ability to perform unipedal stance and tandem walk. Participants were allocated to TC (n = 107, mean age 78) or CBST, an intervention focused on improving dynamic balance and stepping (n = 106, mean age 78). At baseline and 10 weeks, participants were tested in their static balance (Unipedal Stance and Tandem Stance (TS)), stepping (Maximum Step Length, Rapid Step Test), and Timed Up and Go (TUG). Performance improved more with CBST than TC, ranging from 5% to 10% for the stepping tests (Maximum Step Length and Rapid Step Test) and 9% for TUG. The improvement in TUG represented an improvement of more than 1 second. Greater improvements were also seen in static balance ability (in TS) with CBST than TC. Of the two training programs, in which variants of each program have been proven to reduce falls, CBST results in modest improvements in balance, stepping, and functional mobility versus TC over a 10-week period. Future research should include a prospective comparison of fall rates in response to these two balance training programs.

Soft tissue balance changes depending on joint distraction force in total knee arthroplasty.

PubMed

Nagai, Kanto; Muratsu, Hirotsugu; Matsumoto, Tomoyuki; Miya, Hidetoshi; Kuroda, Ryosuke; Kurosaka, Masahiro

2014-03-01

The influence of joint distraction force on intraoperative soft tissue balance was evaluated using Offset Repo-Tensor® for 78 knees that underwent primary posterior-stabilized total knee arthroplasty. The joint center gap and varus ligament balance were measured between osteotomized surfaces using 20, 40 and 60 lbs of joint distraction force. These values were significantly increased at extension and flexion as the distraction force increased. Furthermore, lateral compartment stiffness was significantly lower than medial compartment stiffness. Thus, larger joint distraction forces led to larger varus ligament balance and joint center gap, because of the difference in soft tissue stiffness between lateral and medial compartments. These findings indicate the importance of the strength of joint distraction force in the assessment of soft tissue balance, especially when using gap-balancing technique. © 2014.

Development and validity of an instrumented handbike: initial results of propulsion kinetics.

PubMed

van Drongelen, Stefan; van den Berg, Jos; Arnet, Ursina; Veeger, Dirkjan H E J; van der Woude, Lucas H V

2011-11-01

To develop an instrumented handbike system to measure the forces applied to the handgrip during handbiking. A 6 degrees of freedom force sensor was built into the handgrip of an attach-unit handbike, together with two optical encoders to measure the orientation of the handgrip and crank in space. Linearity, precision, and percent error were determined for static and dynamic tests. High linearity was demonstrated for both the static and the dynamic condition (r=1.01). Precision was high under the static condition (standard deviation of 0.2N), however the precision decreased with higher loads during the dynamic condition. Percent error values were between 0.3 and 5.1%. This is the first instrumented handbike system that can register 3-dimensional forces. It can be concluded that the instrumented handbike system allows for an accurate force analysis based on forces registered at the handle bars. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

Fundamental considerations in ski binding analysis.

PubMed

Mote, C D; Hull, M L

1976-01-01

1. The static adjustment of a ski binding by hand or by available machines is only an adjustment and is neither a static nor a dynamic evaluation of the binding design. Bindings of different design with identical static adjustments will perform differently in environments in which the forces are static or dynamic. 2. The concept of binding release force is a useful measure of binding adjustment, but it is inappropriate as a criterion for binding evaluation. First, it does not direct attention toward the injury causing mechanism, strain, or displacement in the leg. Second, it is only part of the evaluation in dynamic problems. 3. The binding release decision in present bindings is displacement controlled. The relative displacement of the boot and ski is the system variable. For any specified relative displacement the binding force can be any of an infinite number of possibilities determined by the loading path. 4. The response of the leg-ski system to external impulses applied to the ski is independent of the boot-ski relative motion as long as the boot recenters quickly in the binding. Response is dependent upon the external impulse plus system inertia, damping and stiffness. 5. When tested under half sinusoidal forces applied to a test ski, all bindings will demonstrate static and impulse loading regions. In the static region the force drives the binding to a relative release displacement. In the impulse region the initial velocity of the ski drives the binding to a release displacement. 6. The transition between the static and impulse loading regions is determined by the binding's capacity to store and dissipate energy along the principal loading path. Increased energy capacity necessitates larger external impulses to produce release. 7. In all bindings examined to date, the transmitted leg displacement or strain at release under static loading exceeds leg strain under dynamic or impact loading. Because static loading is responsible for many injuries, a skier should be able to release his bindings in every mode by simply pulling or twisting his foot outward. If that cannot be done without injury, the skier has identified for himself one type of fall that will result in injury. 8. And lastly, a little advice from Ben Franklin--"Carelessness does more harm than a want of knowledge."

Hamstring Stiffness Returns More Rapidly After Static Stretching Than Range of Motion, Stretch Tolerance, and Isometric Peak Torque.

PubMed

Hatano, Genki; Suzuki, Shigeyuki; Matsuo, Shingo; Kataura, Satoshi; Yokoi, Kazuaki; Fukaya, Taizan; Fujiwara, Mitsuhiro; Asai, Yuji; Iwata, Masahiro

2017-12-18

Hamstring injuries are common, and lack of hamstring flexibility may predispose to injury. Static stretching increases range of motion (ROM) but also results in reduced muscle strength after stretching. The effects of stretching on the hamstring muscles and the duration of these effects remain unclear. To determine the effects of static stretching on the hamstrings and the duration of these effects. Randomized crossover study. University laboratory. Twenty-four healthy volunteers. We measured the torque-angle relationship (ROM, passive torque (PT) at the onset of pain, and passive stiffness) and isometric muscle force using an isokinetic dynamometer. After a 60-minute rest, the ROM of the dynamometer was set at maximum tolerable intensity; this position was maintained for 300 seconds while static passive torque (SPT) was measured continuously. We remeasured the torque-angle relationship and isometric muscle force after rest periods of 10, 20, and 30 minutes. Change in SPT during stretching; changes in ROM, PT at the onset of pain, passive stiffness, and isometric muscle force before stretching compared with 10, 20, and 30 minutes after stretching. SPT decreased significantly during stretching. Passive stiffness decreased significantly 10 and 20 minutes after stretching, but there was no significant pre- vs. post-stretching difference after 30 minutes. PT at the onset of pain and ROM increased significantly after stretching at all rest intervals, while isometric muscle force decreased significantly after all rest intervals. The effect of static stretching on passive stiffness of the hamstrings was not maintained as long as the changes in ROM, stretch tolerance, and isometric muscle force. Therefore, frequent stretching is necessary to improve the viscoelasticity of the muscle-tendon unit. Muscle force was decreased for 30 minutes after stretching; this should be considered prior to activities requiring maximal muscle strength.

Revisiting the Least Force Required to Keep a Block from Sliding

ERIC Educational Resources Information Center

De, Subhranil

2013-01-01

This article pertains to a problem on static friction that concerns a block of mass "M" resting on a rough inclined plane. The coefficient of static friction is microsecond and the inclination angle theta is greater than tan[superscript -1] microsecond. This means that some force "F" must be applied (see Fig. 1) to keep the…

Effect of Aerobic Loading on Static Balance in Young Athletes

ERIC Educational Resources Information Center

Akyüz, Öznur

2017-01-01

The fact that balances can also be a factor in performance distinction between athletes in athletic skills, and is considered to provide positive acceleration for physical development in which motor skills are exhibited. Human's skill to ensure balance can be defined as a determinant factor in development of other motor skills. From this point of…

Fluid flows and forces in development: functions, features and biophysical principles

PubMed Central

Freund, Jonathan B.; Goetz, Jacky G.; Hill, Kent L.; Vermot, Julien

2012-01-01

Throughout morphogenesis, cells experience intracellular tensile and contractile forces on microscopic scales. Cells also experience extracellular forces, such as static forces mediated by the extracellular matrix and forces resulting from microscopic fluid flow. Although the biological ramifications of static forces have received much attention, little is known about the roles of fluid flows and forces during embryogenesis. Here, we focus on the microfluidic forces generated by cilia-driven fluid flow and heart-driven hemodynamics, as well as on the signaling pathways involved in flow sensing. We discuss recent studies that describe the functions and the biomechanical features of these fluid flows. These insights suggest that biological flow determines many aspects of cell behavior and identity through a specific set of physical stimuli and signaling pathways. PMID:22395739

Effects of aquatic physiotherapy on the improvement of balance and corporal symmetry in stroke survivors.

PubMed

Montagna, Jéssica Cristine; Santos, Bárbara C; Battistuzzo, Camila R; Loureiro, Ana Paula C

2014-01-01

One of the main problems associate with hemiparesis after stroke is the decrease in balance during static and dynamic postures which can highly affect daily life activities. To assess the effects of aquatic physiotherapy on the balance and quality of life (SS-QoL) of people with pos stroke. Chronic stroke participants received at total 18 individual sessions of aquatic physiotherapy using the principle of Halliwick (2x of 40 minutes per week). The outcomes measured were: Berg Balance scale, Timed up & go test (TUG), Stroke Specific Quality of Life Scale (SS-QoL) and baropodometric analysis. These assessment were performed before and one week after intervention. Fifteen participants were included in this study. The mean age was 58.5 and 54% was male. After intervention, participants had a significant improvement on their static balance measured by Berg Balance scale and TUG. Dynamic balance had a significant trend of improvement in mediolateral domain with eyes closed and during sit-to-stand. The mobility domain of the SS-QoL questionnaire was significant higher after intervention. Our results suggest that aquatic physiotherapy using the method of Halliwick can be a useful tool during stroke rehabilitation to improve balance. However, this improvement may not have significant impact of their quality of life.

[Studies of time-course changes in human body balance after ingestion of long-acting hypnotics].

PubMed

Nakamura, Masahiro; Ishii, Masanori; Niwa, Yoji; Yamazaki, Momoko; Ito, Hiroshi

2004-02-01

Falling accidents are a serious nocosomial problem, with balance disorders after the ingestion of hypnotics said to be a cause. Based on the results of animal studies, it was postulated that this problem involves the muscle relaxation that is a pharmacological effect of benzodiazepines (BZP). No reports have, to our knowledge, been made of time-course changes in human body balance after ingestion of hypnotics. Accordingly, we used quazepam (Doral), a long-acting hypnotic considered to show comparatively weak muscle relaxation, to study static balance after drug ingestion in human volunteers. Briefly, informed consent was obtained from 8 healthy adults, then a gait analytic system (Gangas) was used to test static balance after drug ingestion (Mann and Romberg tests). We also measured circulating drug concentration over time. Our results showed that balance disorders occurred after quazepam ingestion with an unstable posture particularly striking. Given the function of quazepam receptors, it is difficult to surmise that balance disorders after drug ingestion were due to the drug's muscle relaxation. We surmised that inhibition from the central nervous system in connection with nerves awakening was involved. We found a strong correlation between the manifestation of balance disorders after drug ingestion and circulating drug concentration.

Ponderomotive Forces in Cosmos

NASA Astrophysics Data System (ADS)

Lundin, R.; Guglielmi, A.

2006-12-01

This review is devoted to ponderomotive forces and their importance for the acceleration of charged particles by electromagnetic waves in space plasmas. Ponderomotive forces constitute time-averaged nonlinear forces acting on a media in the presence of oscillating electromagnetic fields. Ponderomotive forces represent a useful analytical tool to describe plasma acceleration. Oscillating electromagnetic fields are also related with dissipative processes, such as heating of particles. Dissipative processes are, however, left outside these discussions. The focus will be entirely on the (conservative) ponderomotive forces acting in space plasmas. The review consists of seven sections. In Section 1, we explain the rational for using the auxiliary ponderomotive forces instead of the fundamental Lorentz force for the study of particle motions in oscillating fields. In Section 2, we present the Abraham, Miller, Lundin-Hultqvist and Barlow ponderomotive forces, and the Bolotovsky-Serov ponderomotive drift. The hydrodynamic, quasi-hydrodynamic, and ‘`test-particle’' approaches are used for the study of ponderomotive wave-particle interaction. The problems of self-consistency and regularization are discussed in Section 3. The model of static balance of forces (Section 4) exemplifies the interplay between thermal, gravitational and ponderomotive forces, but it also introduces a set of useful definitions, dimensionless parameters, etc. We analyze the Alfvén and ion cyclotron waves in static limit with emphasis on the specific distinction between traveling and standing waves. Particular attention has been given to the impact of traveling Alfvén waves on the steady state anabatic wind that blows over the polar regions (Section~5). We demonstrate the existence of a wave-induced cold anabatic wind. We also show that, at a critical point, the ponderomotive acceleration of the wind is a factor of 3 greater than the thermal acceleration. Section 6 demonstrates various manifestations of ponderomotive forces in the Earth's magnetosphere, for instance the ionospheric plasma acceleration and outflow. The polar wind and the auroral density cavities are considered in relation to results from the Freja and Viking satellites. The high-altitude energization and escape of ions is discussed. The ponderomotive anharmonicity of standing Alfvén waves is analyzed from ground based ULF wave measurements. The complexity of the many challenging problems related with plasma processes near the magnetospheric boundaries is discussed in the light of recent Cluster observations. At the end of Section 6, we consider the application of ponderomotive forces to the diversity of phenomena on the Sun, in the interstellar environment, on newborn stars, pulsars and active galaxies. We emphasize the role of forcing of magnetized plasmas in general and ponderomotive forcing in particular, presenting some simple conceivable scenarios for massive outflow and jets from astrophysical objects.

Effectiveness of a Wii balance board-based system (eBaViR) for balance rehabilitation: a pilot randomized clinical trial in patients with acquired brain injury

PubMed Central

2011-01-01

Background Acquired brain injury (ABI) is the main cause of death and disability among young adults. In most cases, survivors can experience balance instability, resulting in functional impairments that are associated with diminished health-related quality of life. Traditional rehabilitation therapy may be tedious. This can reduce motivation and adherence to the treatment and thus provide a limited benefit to patients with balance disorders. We present eBaViR (easy Balance Virtual Rehabilitation), a system based on the Nintendo® Wii Balance Board® (WBB), which has been designed by clinical therapists to improve standing balance in patients with ABI through motivational and adaptative exercises. We hypothesize that eBaViR, is feasible, safe and potentially effective in enhancing standing balance. Methods In this contribution, we present a randomized and controlled single blinded study to assess the influence of a WBB-based virtual rehabilitation system on balance rehabilitation with ABI hemiparetic patients. This study describes the eBaViR system and evaluates its effectiveness considering 20 one-hour-sessions of virtual reality rehabilitation (n = 9) versus standard rehabilitation (n = 8). Effectiveness was evaluated by means of traditional static and dynamic balance scales. Results The final sample consisted of 11 men and 6 women. Mean ± SD age was 47.3 ± 17.8 and mean ± SD chronicity was 570.9 ± 313.2 days. Patients using eBaViR had a significant improvement in static balance (p = 0.011 in Berg Balance Scale and p = 0.011 in Anterior Reaches Test) compared to patients who underwent traditional therapy. Regarding dynamic balance, the results showed significant improvement over time in all these measures, but no significant group effect or group-by-time interaction was detected for any of them, which suggests that both groups improved in the same way. There were no serious adverse events during treatment in either group. Conclusions The results suggest that eBaViR represents a safe and effective alternative to traditional treatment to improve static balance in the ABI population. These results have encouraged us to reinforce the virtual treatment with new exercises, so an evolution of the system is currently being developed. PMID:21600066

Effectiveness of a Wii balance board-based system (eBaViR) for balance rehabilitation: a pilot randomized clinical trial in patients with acquired brain injury.

PubMed

Gil-Gómez, José-Antonio; Lloréns, Roberto; Alcañiz, Mariano; Colomer, Carolina

2011-05-23

Acquired brain injury (ABI) is the main cause of death and disability among young adults. In most cases, survivors can experience balance instability, resulting in functional impairments that are associated with diminished health-related quality of life. Traditional rehabilitation therapy may be tedious. This can reduce motivation and adherence to the treatment and thus provide a limited benefit to patients with balance disorders. We present eBaViR (easy Balance Virtual Rehabilitation), a system based on the Nintendo® Wii Balance Board® (WBB), which has been designed by clinical therapists to improve standing balance in patients with ABI through motivational and adaptative exercises. We hypothesize that eBaViR, is feasible, safe and potentially effective in enhancing standing balance. In this contribution, we present a randomized and controlled single blinded study to assess the influence of a WBB-based virtual rehabilitation system on balance rehabilitation with ABI hemiparetic patients. This study describes the eBaViR system and evaluates its effectiveness considering 20 one-hour-sessions of virtual reality rehabilitation (n = 9) versus standard rehabilitation (n = 8). Effectiveness was evaluated by means of traditional static and dynamic balance scales. The final sample consisted of 11 men and 6 women. Mean ± SD age was 47.3 ± 17.8 and mean ± SD chronicity was 570.9 ± 313.2 days. Patients using eBaViR had a significant improvement in static balance (p = 0.011 in Berg Balance Scale and p = 0.011 in Anterior Reaches Test) compared to patients who underwent traditional therapy. Regarding dynamic balance, the results showed significant improvement over time in all these measures, but no significant group effect or group-by-time interaction was detected for any of them, which suggests that both groups improved in the same way. There were no serious adverse events during treatment in either group. The results suggest that eBaViR represents a safe and effective alternative to traditional treatment to improve static balance in the ABI population. These results have encouraged us to reinforce the virtual treatment with new exercises, so an evolution of the system is currently being developed.

The Dynamics of Hadley Circulation Variability and Change

NASA Astrophysics Data System (ADS)

Davis, Nicholas Alexander

The Hadley circulation exerts a dominant control on the surface climate of earth's tropical belt. Its converging surface winds fuel the tropical rains, while subsidence in the subtropics dries and stabilizes the atmosphere, creating deserts on land and stratocumulus decks over the oceans. Because of the strong meridional gradients in temperature and precipitation in the subtropics, any shift in the Hadley circulation edge could project as major changes in surface climate. While climate model simulations predict an expansion of the Hadley cells in response to greenhouse gas forcings, the mechanisms remain elusive. An analysis of the climatology, variability, and response of the Hadley circulation to radiative forcings in climate models and reanalyses illuminates the broader landscape in which Hadley cell expansion is realized. The expansion is a fundamental response of the atmosphere to increasing greenhouse gas concentrations as it scales with other key climate system changes, including polar amplification, increasing static stability, stratospheric cooling, and increasing global-mean surface temperatures. Multiple measures of the Hadley circulation edge latitudes co-vary with the latitudes of the eddy-driven jets on all timescales, and both exhibit a robust poleward shift in response to forcings. Further, across models there is a robust coupling between the eddy-driving on the Hadley cells and their width. On the other hand, the subtropical jet and tropopause break latitudes, two common observational proxies for the tropical belt edges, lack a strong statistical relationship with the Hadley cell edges and have no coherent response to forcings. This undermines theories for the Hadley cell width predicated on angular momentum conservation and calls for a new framework for understanding Hadley cell expansion. A numerical framework is developed within an idealized general circulation model to isolate the mean flow and eddy responses of the global atmosphere to radiative forcings. It is found that it is primarily the eddy response to greenhouse-gas-like forcings that causes Hadley cell expansion. However, the mean flow changes in the Hadley circulation itself crucially mediate this eddy response such that the full response comes about due to eddy-mean flow interactions. A theoretical scaling for the Hadley cell width based on moist static energy is developed to provide an improved framework to understand climate change responses of the general circulation. The scaling predicts that expansion is driven by increases in the surface latent heat flux and the width of the rising branch of the circulation and opposed by increases in tropospheric radiative cooling. A reduction in subtropical moist static energy flux divergence by the eddies is key, as it tilts the energetic balance in favor of expansion.

Destabilization of Human Balance Control by Static and Dynamic Head Tilts

NASA Technical Reports Server (NTRS)

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

2004-01-01

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

The energy balance of the solar transition region

NASA Technical Reports Server (NTRS)

Jordan, C.

1980-01-01

It is shown how the observed distribution of the emission measure with temperature can be used to limit the range of energy deposition functions suitable for heating the solar transition region and inner corona. The minimum energy loss solution is considered in view of the work by Hearn (1975) in order to establish further scaling laws between the transition region pressure, the maximum coronal temperature and the parameter giving the absolute value of the emission measure. Also discussed is the absence of a static energy balance at the base of the transition region in terms of measurable atmospheric parameters, and the condition for a static energy balance is given. In addition, the possible role of the emission from He II in stabilizing the atmosphere by providing enhanced radiation loss is considered.

Landing pressure loads of the 140A/B space shuttle orbiter (model 43-0) determined in the Rockwell International low speed wind tunnel (OA69), volume 1. [wind tunnel tests

NASA Technical Reports Server (NTRS)

Soard, T. L.

1975-01-01

Wind tunnel tests of a 0.0405 scale model of the -1404A/B configuration of the Space Shuttle Vehicle Orbiter are presented. Pressure loads data were obtained from the orbiter in the landing configuration in the presence of the ground for structural strength analysis. This was accomplished by locating as many as 30 static pressure bugs at various locations on external model surfaces as each configuration was tested. A complete pressure loads survey was generated for each configuration by combining data from all bug locations, and these loads are described for the fuselage, wing, vertical tail, and landing gear doors. Aerodynamic force data was measured by a six component internal strain gage balance. This data was recorded to correct model angles of attack and sideslip for sting and balance deflections and to determine the aerodynamic effects of landing gear extension. All testing was conducted at a Mach number of 0.165 and a Reynolds number of 1.2 million per foot. Photographs of test configurations are shown.

Tail function during arboreal quadrupedalism in squirrel monkeys (Saimiri boliviensis) and tamarins (Saguinus oedipus).

PubMed

Young, Jesse W; Russo, Gabrielle A; Fellmann, Connie D; Thatikunta, Meena A; Chadwell, Brad A

2015-10-01

The need to maintain stability on narrow branches is often presented as a major selective force shaping primate morphology, with adaptations to facilitate grasping receiving particular attention. The functional importance of a long and mobile tail for maintaining arboreal stability has been comparatively understudied. Tails can facilitate arboreal balance by acting as either static counterbalances or dynamic inertial appendages able to modulate whole-body angular momentum. We investigate associations between tail use and inferred grasping ability in two closely related cebid platyrrhines-cotton-top tamarins (Saguinus oedipus) and black-capped squirrel monkeys (Saimiri boliviensis). Using high-speed videography of captive monkeys moving on 3.2 cm diameter poles, we specifically test the hypothesis that squirrel monkeys (characterized by grasping extremities with long digits) will be less dependent on the tail for balance than tamarins (characterized by claw-like nails, short digits, and a reduced hallux). Tamarins have relatively longer tails than squirrel monkeys, move their tails through greater angular amplitudes, at higher angular velocities, and with greater angular accelerations, suggesting dynamic use of tail to regulate whole-body angular momentum. By contrast, squirrel monkeys generally hold their tails in a comparatively stationary posture and at more depressed angles, suggesting a static counterbalancing mechanism. This study, the first empirical test of functional tradeoffs between grasping ability and tail use in arboreal primates, suggests a critical role for the tail in maintaining stability during arboreal quadrupedalism. Our findings have the potential to inform our functional understanding of tail loss during primate evolution. © 2015 Wiley Periodicals, Inc.

Devices and tasks involved in the objective assessment of standing dynamic balancing - A systematic literature review.

PubMed

Petró, Bálint; Papachatzopoulou, Alexandra; Kiss, Rita M

2017-01-01

Static balancing assessment is often complemented with dynamic balancing tasks. Numerous dynamic balancing assessment methods have been developed in recent decades with their corresponding balancing devices and tasks. The aim of this systematic literature review is to identify and categorize existing objective methods of standing dynamic balancing ability assessment with an emphasis on the balancing devices and tasks being used. Three major scientific literature databases (Science Direct, Web of Science, PLoS ONE) and additional sources were used. Studies had to use a dynamic balancing device and a task described in detail. Evaluation had to be based on objectively measureable parameters. Functional tests without instrumentation evaluated exclusively by a clinician were excluded. A total of 63 articles were included. The data extracted during full-text assessment were: author and date; the balancing device with the balancing task and the measured parameters; the health conditions, size, age and sex of participant groups; and follow-up measurements. A variety of dynamic balancing assessment devices were identified and categorized as 1) Solid ground, 2) Balance board, 3) Rotating platform, 4) Horizontal translational platform, 5) Treadmill, 6) Computerized Dynamic Posturography, and 7) Other devices. The group discrimination ability of the methods was explored and the conclusions of the studies were briefly summarized. Due to the wide scope of this search, it provides an overview of balancing devices and do not represent the state-of-the-art of any single method. The identified dynamic balancing assessment methods are offered as a catalogue of candidate methods to complement static assessments used in studies involving postural control.

Effectiveness of balance training programme in reducing the frequency of falling in established osteoporotic women: a randomized controlled trial.

PubMed

Mikó, Ibolya; Szerb, Imre; Szerb, Anna; Poor, Gyula

2017-02-01

To investigate the effect of a 12-month sensomotor balance exercise programme on postural control and the frequency of falling in women with established osteoporosis. Randomized controlled trial where the intervention group was assigned the 12-month Balance Training Programme and the control group did not undertake any intervention beyond regular osteoporosis treatment. A total of 100 osteoporotic women - at least with one osteoporotic fracture - aged 65 years old and above. Balance was assessed in static and dynamic posture both with performance-based measures of balance, such as the Berg Balance Scale and the Timed Up and Go Test, and with a stabilometric computerized platform. Patients in the intervention group completed the 12-month sensomotor Balance Training Programme in an outpatient setting, guided by physical therapists, three times a week, for 30 minutes. The Berg Balance Scale and the Timed Up and Go Test showed a statistically significant improvement of balance in the intervention group ( p = 0.001 and p = 0.005, respectively). Balance tests using the stabilometer also showed a statistically significant improvement in static and dynamic postural balance for osteoporotic women after the completion of the Balance Training Programme. As a consequence, the one-year exercise programme significantly decreased the number of falls in the exercise group compared with the control group. The Balance Training Programme significantly improved the balance parameters and reduced the number of falls in postmenopausal women who have already had at least one fracture in the past.

Strain Gauge Balance Uncertainty Analysis at NASA Langley: A Technical Review

NASA Technical Reports Server (NTRS)

Tripp, John S.

1999-01-01

This paper describes a method to determine the uncertainties of measured forces and moments from multi-component force balances used in wind tunnel tests. A multivariate regression technique is first employed to estimate the uncertainties of the six balance sensitivities and 156 interaction coefficients derived from established balance calibration procedures. These uncertainties are then employed to calculate the uncertainties of force-moment values computed from observed balance output readings obtained during tests. Confidence and prediction intervals are obtained for each computed force and moment as functions of the actual measurands. Techniques are discussed for separate estimation of balance bias and precision uncertainties.

Three-Component Force Measurements on a Scramjet in a Reflected-Shock Tunnel

NASA Technical Reports Server (NTRS)

Tsai, C.-Y.; Bakos, R. J.; Mee, D. J.

1998-01-01

A three-component stress-wave force-balance for a large scramjet has been designed, calibrated and tested in the HYPULSE reflected shock tunnel at GASL Inc., New York. The scramjet model is over 3-foot long and weighs in excess of 90 Ibm. The stress-wave force-balance is comprised of three stress bars which are attached to the model. Calibration results indicate that the force balance responds well within about 1 ms and that the sensitivity of the balance to the distribution of load is not large. Results with and without fuel injection were obtained in the tunnel operated for Mach 7 and Mach 10 flight simulation. These tests showed the force-balance can resolve axial force increments due to combustion of about 40 lb in the presence of model lift forces of 500-700 lb.

Field assessment of balance in 10 to 14 year old children, reproducibility and validity of the Nintendo Wii board.

PubMed

Larsen, Lisbeth Runge; Jørgensen, Martin Grønbech; Junge, Tina; Juul-Kristensen, Birgit; Wedderkopp, Niels

2014-06-10

Because body proportions in childhood are different to those in adulthood, children have a relatively higher centre of mass location. This biomechanical difference and the fact that children's movements have not yet fully matured result in different sway performances in children and adults. When assessing static balance, it is essential to use objective, sensitive tools, and these types of measurement have previously been performed in laboratory settings. However, the emergence of technologies like the Nintendo Wii Board (NWB) might allow balance assessment in field settings. As the NWB has only been validated and tested for reproducibility in adults, the purpose of this study was to examine reproducibility and validity of the NWB in a field setting, in a population of children. Fifty-four 10-14 year-olds from the CHAMPS-Study DK performed four different balance tests: bilateral stance with eyes open (1), unilateral stance on dominant (2) and non-dominant leg (3) with eyes open, and bilateral stance with eyes closed (4). Three rounds of the four tests were completed with the NWB and with a force platform (AMTI). To assess reproducibility, an intra-day test-retest design was applied with a two-hour break between sessions. Bland-Altman plots supplemented by Minimum Detectable Change (MDC) and concordance correlation coefficient (CCC) demonstrated satisfactory reproducibility for the NWB and the AMTI (MDC: 26.3-28.2%, CCC: 0.76-0.86) using Centre Of Pressure path Length as measurement parameter. Bland-Altman plots demonstrated satisfactory concurrent validity between the NWB and the AMTI, supplemented by satisfactory CCC in all tests (CCC: 0.74-0.87). The ranges of the limits of agreement in the validity study were comparable to the limits of agreement of the reproducibility study. Both NWB and AMTI have satisfactory reproducibility for testing static balance in a population of children. Concurrent validity of NWB compared with AMTI was satisfactory. Furthermore, the results from the concurrent validity study were comparable to the reproducibility results of the NWB and the AMTI. Thus, NWB has the potential to replace the AMTI in field settings in studies including children. Future studies are needed to examine intra-subject variability and to test the predictive validity of NWB.

Field assessment of balance in 10 to 14 year old children, reproducibility and validity of the Nintendo Wii board

PubMed Central

2014-01-01

Background Because body proportions in childhood are different to those in adulthood, children have a relatively higher centre of mass location. This biomechanical difference and the fact that children’s movements have not yet fully matured result in different sway performances in children and adults. When assessing static balance, it is essential to use objective, sensitive tools, and these types of measurement have previously been performed in laboratory settings. However, the emergence of technologies like the Nintendo Wii Board (NWB) might allow balance assessment in field settings. As the NWB has only been validated and tested for reproducibility in adults, the purpose of this study was to examine reproducibility and validity of the NWB in a field setting, in a population of children. Methods Fifty-four 10–14 year-olds from the CHAMPS-Study DK performed four different balance tests: bilateral stance with eyes open (1), unilateral stance on dominant (2) and non-dominant leg (3) with eyes open, and bilateral stance with eyes closed (4). Three rounds of the four tests were completed with the NWB and with a force platform (AMTI). To assess reproducibility, an intra-day test-retest design was applied with a two-hour break between sessions. Results Bland-Altman plots supplemented by Minimum Detectable Change (MDC) and concordance correlation coefficient (CCC) demonstrated satisfactory reproducibility for the NWB and the AMTI (MDC: 26.3-28.2%, CCC: 0.76-0.86) using Centre Of Pressure path Length as measurement parameter. Bland-Altman plots demonstrated satisfactory concurrent validity between the NWB and the AMTI, supplemented by satisfactory CCC in all tests (CCC: 0.74-0.87). The ranges of the limits of agreement in the validity study were comparable to the limits of agreement of the reproducibility study. Conclusion Both NWB and AMTI have satisfactory reproducibility for testing static balance in a population of children. Concurrent validity of NWB compared with AMTI was satisfactory. Furthermore, the results from the concurrent validity study were comparable to the reproducibility results of the NWB and the AMTI. Thus, NWB has the potential to replace the AMTI in field settings in studies including children. Future studies are needed to examine intra-subject variability and to test the predictive validity of NWB. PMID:24913461

Results of investigations on a 0.0405 scale model PRR version of the NR-SSV orbiter in the North American Aeronautical Laboratory low speed wind tunnel

NASA Technical Reports Server (NTRS)

Kingsland, R. B.; Vaughn, J. E.; Singellton, R.

1973-01-01

Experimental aerodynamic investigations were conducted in a low speed wind tunnel on a scale model space shuttle vehicle (SSV) orbiter. The purpose of the test was to investigate the longitudinal and lateral-directional aerodynamic characteristics of the space shuttle orbiter. Emphasis was placed on model component, wing-glove, and wing-body fairing effects, as well as elevon, aileron, and rudder control effectiveness. Angles of attack from - 5 deg to + 30 deg and angles of sideslip of - 5 deg, 0 deg, and + 5 deg were tested. Static pressures were recorded on base, fuselage, and wing surfaces. Tufts and talc-kerosene flow visualization techniques were also utilized. The aerodynamic force balance results are presented in plotted and tabular form.

Experimental investigations of an 0.0405 scale Space Shuttle Configuration 3 orbiter to determine subsonic stability characteristics. Volume 1: OA21A

NASA Technical Reports Server (NTRS)

Cameron, B. W.; Ritschel, A. J.

1973-01-01

Experimental aerodynamic investigations were conducted in a low speed wind tunnel from May 21 through June 4 and from June 18 through June 25, 1973 on a 0.0405 scale -139B model Space Shuttle Vehicle (SSV) orbiter. The purpose of the test was to investigate the longitudinal and lateral-directional subsonic aerodynamic characteristics of the proposed PRR Space Shuttle orbiter. Emphasis was placed on component buildup effects, elevon, rudder, body flaps, rudder flare effectiveness, and canard and speed brake development. Angles of attack from -4 deg. to 24 deg. and angles of sideslip of -10 deg. to 10 deg. were tested. Static pressures were recorded on the base. The aerodynamic force balance results are presented in plotted and tabular form.

Reduction of the uncertainty of the PTB vacuum pressure scale by a new large area non-rotating piston gauge

NASA Astrophysics Data System (ADS)

Bock, Th; Ahrendt, H.; Jousten, K.

2009-10-01

This paper describes the metrological characterization of a new large area piston gauge (FRS5, Furness Rosenberg Standard) installed at the vacuum metrology laboratory of the Physikalisch-Technische Bundesanstalt (PTB). The operational procedure and the uncertainty budget for pressures between 30 Pa and 11 kPa are given. Comparisons between the FRS5 and a mercury manometer, a rotary piston gauge and a force-balanced piston gauge are described. We show that the reproducibility of the calibration values of capacitance diaphragm gauges is enhanced by a factor of 6 compared with a static expansion primary standard (SE2). Improvements of the SE2 performance by reducing the number of expansions and smaller uncertainties of expansion ratios are discussed.

Balance evaluation in haemophilic preadolescent patients using Nintendo Wii Balance Board®.

PubMed

Pérez-Alenda, S; Carrasco, J J; Aguilar-Rodríguez, M; Martínez-Gómez, L; Querol-Giner, M; Cuesta-Barriuso, R; Torres-Ortuño, A; Querol, F

2017-01-01

Alterations in the musculoskeletal system, especially in the lower limbs, limit physical activity and affect balance and walking. Postural impairments in haemophilic preteens could increase the risk of bleeding events and deteriorate the physical condition, promoting the progression of haemophilic arthropathy. This study aims to evaluate static postural balance in haemophilic children, assessed by means of the Wii Balance Board ® (WBB). Nineteen children with haemophilia and 19 without haemophilia aged 9-10 years, have participated in this study. Postural balance was assessed by performing four tests, each one lasting 15 s: bipodal eyes open (BEO), bipodal eyes closed (BEC), monopodal dominant leg (MD) and monopodal non-dominant leg (MND). Two balance indices, standard deviation of amplitude (SDA) and standard deviation of velocity (SDV) were calculated in the anterior-posterior (AP) and medial-lateral (ML) directions. Index values were higher in haemophilic group and the differences were statistically significant (P < 0.05) in only six (SDAAP in BEO, BEC and MD conditions, SDAML in BEO, SDVAP in BEO and SDVML in MND condition) of 16 parameters analysed. Tests performed indicate a poorer static postural balance in the haemophilic cohort compared to the control group. Accordingly, physiotherapy programmes, physical activity and sports should be designed to improve the postural balance with the aim of preventing joint deterioration and improving quality of life. © 2016 John Wiley & Sons Ltd.

A Tactile Sensor Using Piezoresistive Beams for Detection of the Coefficient of Static Friction

PubMed Central

Okatani, Taiyu; Takahashi, Hidetoshi; Noda, Kentaro; Takahata, Tomoyuki; Matsumoto, Kiyoshi; Shimoyama, Isao

2016-01-01

This paper reports on a tactile sensor using piezoresistive beams for detection of the coefficient of static friction merely by pressing the sensor against an object. The sensor chip is composed of three pairs of piezoresistive beams arranged in parallel and embedded in an elastomer; this sensor is able to measure the vertical and lateral strains of the elastomer. The coefficient of static friction is estimated from the ratio of the fractional resistance changes corresponding to the sensing elements of vertical and lateral strains when the sensor is in contact with an object surface. We applied a normal force on the sensor surface through objects with coefficients of static friction ranging from 0.2 to 1.1. The fractional resistance changes corresponding to vertical and lateral strains were proportional to the applied force. Furthermore, the relationship between these responses changed according to the coefficients of static friction. The experimental result indicated the proposed sensor could determine the coefficient of static friction before a global slip occurs. PMID:27213374

Friction between various self-ligating brackets and archwire couples during sliding mechanics.

PubMed

Stefanos, Sennay; Secchi, Antonino G; Coby, Guy; Tanna, Nipul; Mante, Francis K

2010-10-01

The aim of this study was to evaluate the frictional resistance between active and passive self-ligating brackets and 0.019 × 0.025-in stainless steel archwire during sliding mechanics by using an orthodontic sliding simulation device. Maxillary right first premolar active self-ligating brackets In-Ovation R, In-Ovation C (both, GAC International, Bohemia, NY), and SPEED (Strite Industries, Cambridge, Ontario, Canada), and passive self-ligating brackets SmartClip (3M Unitek, Monrovia, Calif), Synergy R (Rocky Mountain Orthodontics, Denver, Colo), and Damon 3mx (Ormco, Orange, Calif) with 0.022-in slots were used. Frictional force was measured by using an orthodontic sliding simulation device attached to a universal testing machine. Each bracket-archwire combination was tested 30 times at 0° angulation relative to the sliding direction. Statistical comparisons were performed with 1-way analysis of variance (ANOVA) followed by Dunn multiple comparisons. The level of statistical significance was set at P <0.05. The Damon 3mx brackets had significantly the lowest mean static frictional force (8.6 g). The highest mean static frictional force was shown by the SPEED brackets (83.1 g). The other brackets were ranked as follows, from highest to lowest, In-Ovation R, In-Ovation C, SmartClip, and Synergy R. The mean static frictional forces were all statistically different. The ranking of the kinetic frictional forces of bracket-archwire combinations was the same as that for static frictional forces. All bracket-archwire combinations showed significantly different kinetic frictional forces except SmartClip and In-Ovation C, which were not significantly different from each other. Passive self-ligating brackets have lower static and kinetic frictional resistance than do active self-ligating brackets with 0.019 × 0.025-in stainless steel wire. Copyright © 2010 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Choose Wisely: Static or Kinetic Friction--The Power of Dimensionless Plots

ERIC Educational Resources Information Center

Ludwigsen, Daniel; Svinarich, Kathryn

2009-01-01

Consider a problem of sliding blocks, one stacked atop the other, resting on a frictionless table. If the bottom block is pulled horizontally, nature makes a choice: if the applied force is small, static friction between the blocks accelerates the blocks together, but with a large force the blocks slide apart. In that case, kinetic friction still…

Kinematic and Kinetic Analysis of Repeated and Static Elevé in Adolescent Female Dance Students.

PubMed

Abraham, Amit; Dunsky, Ayelet; Hackney, Madeleine E; Dickstein, Ruth

2018-03-15

Elevé is a fundamental dance movement practiced routinely by dance students and serving as an integral component of screening in dance. It consists of ankle plantar flexion (PF) movement and is considered to be a frequent cause of foot and ankle injuries among dancers, with adolescent female dance students being at greatest risk for such injuries. Therefore, gaining additional knowledge regarding elevé functional range of motion (ROM) and inter-leg weightbearing distribution (WBD) properties among adolescent dance students is warranted for pedagogic, screening, injury prevention, and rehabilitation purposes. The aims of this study were three-fold: 1. to report and compare dance-specific, functional kinematic (ankle PF maximum angle and ankle PF ROM), kinetic (inter-leg WBD), and self-reported level of difficulty (balance, muscular force, and concentration) properties of repeated and static elevé among adolescent female dance students; 2. to look for correlations between elevé properties and participants' demographics (age, height, weight, dance experience, and leg dominance); and 3. to describe the relationships between the two kinematic properties in both elevé tasks. Twenty-three adolescent female dance students (mean age 13.57 ± 0.50 years) were measured while performing two elevé tasks: 10 repetitions ("repeated elevé task") and 10 consecutive seconds hold ("static elevé task"). Data regarding ankle motion and WBD were collected and analyzed using three-dimensional motion capture and two force plates. The data gained from this study expand our current understanding of elevé dance movement and may contribute to clinical relevancy and applicability of screening procedures being conducted in pre-professional dance settings. This may help to identify adolescent dance students with the potential to undertake a career in professional dance as well as to investigate the parameters associated with risk of ankle injuries in this population.

Virtual-reality balance training with a video-game system improves dynamic balance in chronic stroke patients.

PubMed

Cho, Ki Hun; Lee, Kyoung Jin; Song, Chang Ho

2012-09-01

Stroke is one of the most serious healthcare problems and a major cause of impairment of cognition and physical functions. Virtual rehabilitation approaches to postural control have been used for enhancing functional recovery that may lead to a decrease in the risk of falling. In the present study, we investigated the effects of virtual reality balance training (VRBT) with a balance board game system on balance of chronic stroke patients. Participants were randomly assigned to 2 groups: VRBT group (11 subjects including 3 women, 65.26 years old) and control group (11 subjects including 5 women, 63.13 years old). Both groups participated in a standard rehabilitation program (physical and occupational therapy) for 60 min a day, 5 times a week for 6 weeks. In addition, the VRBT group participated in VRBT for 30 min a day, 3 times a week for 6 weeks. Static balance (postural sway velocity with eyes open or closed) was evaluated with the posturography. Dynamic balance was evaluated with the Berg Balance Scale (BBS) and Timed Up and Go test (TUG) that measures balance and mobility in dynamic balance. There was greater improvement on BBS (4.00 vs. 2.81 scores) and TUG (-1.33 vs. -0.52 sec) in the VRBT group compared with the control group (P < 0.05), but not on static balance in both groups. In conclusion, we demonstrate a significant improvement in dynamic balance in chronic stroke patients with VRBT. VRBT is feasible and suitable for chronic stroke patients with balance deficit in clinical settings.

BMI Group-Related Differences in Physical Fitness and Physical Activity in Preschool-Age Children: A Cross-Sectional Analysis

ERIC Educational Resources Information Center

Niederer, Iris; Kriemler, Susi; Zahner, Lukas; Burgi, Flavia; Ebenegger, Vincent; Marques- Vidal, Pedro; Puder, Jardena J.

2012-01-01

In the Ballabeina study, we investigated age- and BMI-group-related differences in aerobic fitness (20 m shuttle run), agility (obstacle course), dynamic (balance beam) and static balance (balance platform), and physical activity (PA, accelerometers) in 613 children (M age = 5.1 years, SD = 0.6). Normal weight (NW) children performed better than…

Vestibulo-ocular response and balance control in children and young adults with mild-to-moderate intellectual and developmental disability: a pilot study.

PubMed

Zur, Oz; Ronen, Ayelet; Melzer, Itshak; Carmeli, Eli

2013-06-01

The vestibulo-ocular response (VOR) may not be fully developed in children with an intellectual and developmental disability (IDD). This study aimed to identify the presence of VOR deficit in children and young adults with unspecified mild-to-moderate intellectual and developmental disability and its effect on balance control. Twenty-one children and young adults with IDD ranging in age from 8 to 22 years (mean 17.5 ± 3.9 years) were included in the study. The VOR was evaluated with the Head Impulse Test and the Static and Dynamic Visual Acuity Test (S&D-VAT). Postural stability was measured in an upright standing position by the Clinical Test for Sensory Interaction in Balance (CTSIB), single leg stance (SLS) during eyes open and eyes closed, and Romberg stance under eyes open and eyes closed conditions using a force platform. Reduced vestibulo-ocular responses were found in 13 of 21 (62%) participants who were able to complete testing. In the fifth condition of the CTSIB (standing on foam with eyes closed), those without VOR deficit were able to maintain balance longer than those with VOR deficit (29 s [median 30] vs. 12s [median 7.3], respectively; p=0.03). The study demonstrates potential effects of VOR deficit in children and young adults with IDD and some significant differences in balance control between those with and without a VOR deficit. VOR function in children and young adults with IDD should be routinely tested to enable early detection of deficits. Copyright © 2013 Elsevier Ltd. All rights reserved.

The influence of commercial-grade carpet on postural sway and balance strategy among older adults.

PubMed

Dickinson, Joan I; Shroyer, JoAnn L; Elias, Jeffrey W

2002-08-01

The purpose of this research study was to examine the effect of a selected commercial-grade carpet on the static balance of healthy, older adults who had not fallen more than twice in the last 6 months. We tested a total of 45 participants. Each participant stood on a computerized balance machine and was subjected to a carpeted versus a noncarpeted condition while exposed to various sensory limitations. We measured both postural sway and balance strategy. The selected commercial-grade carpet did not affect postural sway. The participants were able to adapt to the sensory limitations regardless of whether they were standing on the carpet. Although balance strategy scores were significantly lower during the carpeted conditions, the clinical significance was questionable as the difference between the means was small for practical purposes. Healthy, older adults did not have difficulty maintaining static balance on the carpeted surface; however, the results could be different if participants who had a history of falling had been included. The results from this study are important and provide a basis of comparison for those individuals who have experienced more than two falls in the last 6 months or who have a history of falling.

Medical education on a collision course: sooner rather than later?

PubMed

David, Alan K

2013-03-01

The escalating cost of medical education does not have transparency. This results in high percentages of medical students with progressively rising levels of indebtedness that are only exceeded by the increases in tuition. Indebtedness is a factor in specialty choice along with the "business" of medicine that reimburses procedural-based physicians much more than cognitive primary care-based services. In response to perceived increased physician demand by 2025, medical schools have increased enrollments, and new schools are online or in development. Despite the inevitable increase in medical graduates, the number of residency positions is static and may even contract. While these phenomena are being studied individually, almost no one is examining the bigger picture: increasing numbers of highly indebted students vying for static numbers of residency positions, especially in the more highly remunerative specialties. The workforce is out of balance now, and the desired workforce outcomes are not universally agreed upon, let alone how to achieve them. This collision of forces is imminent. Family medicine can become "counter culture" once again and advocate for change with education/cost data, political expertise, and outcome measures. Returning to our roots by advocating ultimately for the patient is fundamental to our discipline.

Body-freedom flutter of a 1/2-scale forward-swept-wing model, an experimental and analytical study

NASA Technical Reports Server (NTRS)

Chipman, R.; Rauch, F.; Rimer, M.; Muniz, B.

1984-01-01

The aeroelastic phenomenon known as body-freedom flutter (BFF), a dynamic instability involving aircraft-pitch and wing-bending motions which, though rarely experienced on conventional vehicles, is characteristic of forward swept wing (FSW) aircraft was investigated. Testing was conducted in the Langley transonic dynamics tunnel on a flying, cable-mounted, 1/2-scale model of a FSW configuration with and without relaxed static stability (RSS). The BFF instability boundaries were found to occur at significantly lower airspeeds than those associated with aeroelastic wing divergence on the same model. For those cases with RSS, a canard-based stability augmentation system (SAS) was incorporated in the model. This SAS was designed using aerodynamic data measured during a preliminary tunnel test in which the model was attached to a force balance. Data from the subsequent flutter test indicated that BFF speed was not dependent on open-loop static margin but, rather, on the equivalent closed-loop dynamics provided by the SAS. Servo-aeroelastic stability analyses of the flying model were performed using a computer code known as SEAL and predicted the onset of BFF reasonably well.

The internal representation of head orientation differs for conscious perception and balance control

PubMed Central

Dalton, Brian H.; Rasman, Brandon G.; Inglis, J. Timothy

2017-01-01

Key points We tested perceived head‐on‐feet orientation and the direction of vestibular‐evoked balance responses in passively and actively held head‐turned postures.The direction of vestibular‐evoked balance responses was not aligned with perceived head‐on‐feet orientation while maintaining prolonged passively held head‐turned postures. Furthermore, static visual cues of head‐on‐feet orientation did not update the estimate of head posture for the balance controller.A prolonged actively held head‐turned posture did not elicit a rotation in the direction of the vestibular‐evoked balance response despite a significant rotation in perceived angular head posture.It is proposed that conscious perception of head posture and the transformation of vestibular signals for standing balance relying on this head posture are not dependent on the same internal representation. Rather, the balance system may operate under its own sensorimotor principles, which are partly independent from perception. Abstract Vestibular signals used for balance control must be integrated with other sensorimotor cues to allow transformation of descending signals according to an internal representation of body configuration. We explored two alternative models of sensorimotor integration that propose (1) a single internal representation of head‐on‐feet orientation is responsible for perceived postural orientation and standing balance or (2) conscious perception and balance control are driven by separate internal representations. During three experiments, participants stood quietly while passively or actively maintaining a prolonged head‐turned posture (>10 min). Throughout the trials, participants intermittently reported their perceived head angular position, and subsequently electrical vestibular stimuli were delivered to elicit whole‐body balance responses. Visual recalibration of head‐on‐feet posture was used to determine whether static visual cues are used to update the internal representation of body configuration for perceived orientation and standing balance. All three experiments involved situations in which the vestibular‐evoked balance response was not orthogonal to perceived head‐on‐feet orientation, regardless of the visual information provided. For prolonged head‐turned postures, balance responses consistent with actual head‐on‐feet posture occurred only during the active condition. Our results indicate that conscious perception of head‐on‐feet posture and vestibular control of balance do not rely on the same internal representation, but instead treat sensorimotor cues in parallel and may arrive at different conclusions regarding head‐on‐feet posture. The balance system appears to bypass static visual cues of postural orientation and mainly use other sensorimotor signals of head‐on‐feet position to transform vestibular signals of head motion, a mechanism appropriate for most daily activities. PMID:28035656

Traditional Chinese Mind and Body Exercises for Promoting Balance Ability of Old Adults: A Systematic Review and Meta-Analysis

PubMed Central

Zhang, Yanjie; Wang, Yong Tai; Liu, Xiao Lei

2016-01-01

The purpose of this study was to provide a quantitative evaluation of the effectiveness of traditional Chinese mind and body exercises in promoting balance ability for old adults. The eligible studies were extensively searched from electronic databases (Medline, CINAHL, SportDicus, and Web of Science) until 10 May 2016. Reference lists of relevant publications were screened for future hits. The trials used randomized controlled approaches to compare the effects of traditional Chinese mind and body exercise (TCMBE) on balance ability of old adults that were included. The synthesized results of Berg Balance Scale (BBS), Timed Up and Go Test (TUG), and static balance with 95% confidence intervals were counted under a random-effects model. Ten studies were selected based on the inclusion criteria, and a total of 1,798 participants were involved in this review. The results of the meta-analysis showed that TCMBE had no significant improvement on BBS and TUG, but the BBS and TUG could be obviously improved by prolonging the intervention time. In addition, the results showed that TCMBE could significantly improve the static balance compared to control group. In conclusion, old adults who practiced TCMBE with the time not less than 150 minutes per week for more than 15 weeks could promote the balance ability. PMID:27990168

Traditional Chinese Mind and Body Exercises for Promoting Balance Ability of Old Adults: A Systematic Review and Meta-Analysis.

PubMed

Chen, Shihui; Zhang, Yanjie; Wang, Yong Tai; Liu, Xiao Lei

2016-01-01

The purpose of this study was to provide a quantitative evaluation of the effectiveness of traditional Chinese mind and body exercises in promoting balance ability for old adults. The eligible studies were extensively searched from electronic databases (Medline, CINAHL, SportDicus, and Web of Science) until 10 May 2016. Reference lists of relevant publications were screened for future hits. The trials used randomized controlled approaches to compare the effects of traditional Chinese mind and body exercise (TCMBE) on balance ability of old adults that were included. The synthesized results of Berg Balance Scale (BBS), Timed Up and Go Test (TUG), and static balance with 95% confidence intervals were counted under a random-effects model. Ten studies were selected based on the inclusion criteria, and a total of 1,798 participants were involved in this review. The results of the meta-analysis showed that TCMBE had no significant improvement on BBS and TUG, but the BBS and TUG could be obviously improved by prolonging the intervention time. In addition, the results showed that TCMBE could significantly improve the static balance compared to control group. In conclusion, old adults who practiced TCMBE with the time not less than 150 minutes per week for more than 15 weeks could promote the balance ability.

Friction phenomena and phase transition in the underdamped two-dimensional Frenkel-Kontorova model

NASA Astrophysics Data System (ADS)

Yang, Yang; Duan, Wen-Shan; Chen, Jian-Min; Yang, Lei; Tekić, Jasmina; Shao, Zhi-Gang; Wang, Cang-Long

2010-11-01

Locked-to-sliding phase transition has been studied in the driven two-dimensional Frenkel-Kontorova model with the square symmetric substrate potential. It is found that as the driving force increases, the system transfers from the locked state to the sliding state where the motion of particles is in the direction different from that of driving force. With the further increase in driving force, at some critical value, the particles start to move in the direction of driving force. These two critical forces, the static friction or depinning force, and the kinetic friction force for which particles move in the direction of driving force have been analyzed for different system parameters. Different scenarios of phase transitions have been examined and dynamical phases are classified. In the case of zero misfit angle, the analytical expressions for static and kinetic friction force have been obtained.

Corticomuscular synchronization with small and large dynamic force output

PubMed Central

Andrykiewicz, Agnieszka; Patino, Luis; Naranjo, Jose Raul; Witte, Matthias; Hepp-Reymond, Marie-Claude; Kristeva, Rumyana

2007-01-01

Background Over the last few years much research has been devoted to investigating the synchronization between cortical motor and muscular activity as measured by EEG/MEG-EMG coherence. The main focus so far has been on corticomuscular coherence (CMC) during static force condition, for which coherence in beta-range has been described. In contrast, we showed in a recent study [1] that dynamic force condition is accompanied by gamma-range CMC. The modulation of the CMC by various dynamic force amplitudes, however, remained uninvestigated. The present study addresses this question. We examined eight healthy human subjects. EEG and surface EMG were recorded simultaneously. The visuomotor task consisted in isometric compensation for 3 forces (static, small and large dynamic) generated by a manipulandum. The CMC, the cortical EEG spectral power (SP), the EMG SP and the errors in motor performance (as the difference between target and exerted force) were analyzed. Results For the static force condition we found the well-documented, significant beta-range CMC (15–30 Hz) over the contralateral sensorimotor cortex. Gamma-band CMC (30–45 Hz) occurred in both small and large dynamic force conditions without any significant difference between both conditions. Although in some subjects beta-range CMC was observed during both dynamic force conditions no significant difference between conditions could be detected. With respect to the motor performance, the lowest errors were obtained in the static force condition and the highest ones in the dynamic condition with large amplitude. However, when we normalized the magnitude of the errors to the amplitude of the applied force (relative errors) no significant difference between both dynamic conditions was observed. Conclusion These findings confirm that during dynamic force output the corticomuscular network oscillates at gamma frequencies. Moreover, we show that amplitude modulation of dynamic force has no effect on the gamma CMC in the low force range investigated. We suggest that gamma CMC is rather associated with the internal state of the sensorimotor system as supported by the unchanged relative error between both dynamic conditions. PMID:18042289

Reliability and Construct Validity of Limits of Stability Test in Adolescents Using a Portable Forceplate System.

PubMed

Alsalaheen, Bara; Haines, Jamie; Yorke, Amy; Broglio, Steven P

2015-12-01

To examine the reliability, convergent, and discriminant validity of the limits of stability (LOS) test to assess dynamic postural stability in adolescents using a portable forceplate system. Cross-sectional reliability observational study. School setting. Adolescents (N=36) completed all measures during the first session. To examine the reliability of the LOS test, a subset of 15 participants repeated the LOS test after 1 week. Not applicable. Outcome measurements included the LOS test, Balance Error Scoring System, Instrumented Balance Error Scoring System, and Modified Clinical Test for Sensory Interaction on Balance. A significant relation was observed among LOS composite scores (r=.36-.87, P<.05). However, no relation was observed between LOS and static balance outcome measurements. The reliability of the LOS composite scores ranged from moderate to good (intraclass correlation coefficient model 2,1=.73-.96). The results suggest that the LOS composite scores provide unique information about dynamic postural stability, and the LOS test completed at 100% of the theoretical limit appeared to be a reliable test of dynamic postural stability in adolescents. Clinicians should use dynamic balance measurement as part of their balance assessment and should not use static balance testing (eg, Balance Error Scoring System) to make inferences about dynamic balance, especially when balance assessment is used to determine rehabilitation outcomes, or when making return to play decisions after injury. Copyright © 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Static balance and function in children with cerebral palsy submitted to neuromuscular block and neuromuscular electrical stimulation: Study protocol for prospective, randomized, controlled trial

PubMed Central

2012-01-01

Background The use of botulinum toxin A (BT-A) for the treatment of lower limb spasticity is common in children with cerebral palsy (CP). Following the administration of BT-A, physical therapy plays a fundamental role in potentiating the functionality of the child. The balance deficit found in children with CP is mainly caused by muscle imbalance (spastic agonist and weak antagonist). Neuromuscular electrical stimulation (NMES) is a promising therapeutic modality for muscle strengthening in this population. The aim of the present study is to describe a protocol for a study aimed at analyzing the effects of NMES on dorsiflexors combined with physical therapy on static and functional balance in children with CP submitted to BT- A. Methods/Design Protocol for a prospective, randomized, controlled trial with a blinded evaluator. Eligible participants will be children with cerebral palsy (Levels I, II and III of the Gross Motor Function Classification System) between five and 12 years of age, with independent gait with or without a gait-assistance device. All participants will receive BT-A in the lower limbs (triceps surae). The children will then be randomly allocated for either treatment with motor physical therapy combined with NMES on the tibialis anterior or motor physical therapy alone. The participants will be evaluated on three occasions: 1) one week prior to the administration of BT-A; 2) one week after the administration of BT-A; and 3) four months after the administration of BT-A (end of intervention). Spasticity will be assessed by the Modified Ashworth Scale and Modified Tardieu Scale. Static balance will be assessed using the Medicapteurs Fusyo pressure platform and functional balance will be assessed using the Berg Balance Scale. Discussion The aim of this protocol study is to describe the methodology of a randomized, controlled, clinical trial comparing the effect of motor physical therapy combined with NMES on the tibialis anterior muscle or motor physical therapy alone on static and functional balance in children with CP submitted to BT-A in the lower limbs. This study describes the background, hypotheses, methodology of the procedures and measurement of the results. Trial registration RBR5qzs8h PMID:22591446

Static current-sheet models of quiescent prominences

NASA Technical Reports Server (NTRS)

Wu, F.; Low, B. C.

1986-01-01

A particular class of theoretical models idealize the prominence to be a discrete flat electric-current sheet suspended vertically in a potential magnetic field. The weight of the prominence is supported by the Lorentz force in the current sheet. These models can be extended to have curved electric-current sheets and to vary three-dimensionally. The equation for force balance is 1 over 4 pi (del times B) times Bdel p- p9 z=zero. Using Cartesian coordinates we take, for simplicity, a uniform gravity with constant acceleration g in the direction -z. If we are interested not in the detailed internal structure of the prominence, but in the global magnetic configuration around the prominence, we may take prominence plasma to be cold. Consideration is given to how such equilibrium states can be constructed. To simplify the mathematical problem, suppose there is no electric current in the atmosphere except for the discrete currents in the cold prominence sheet. Let us take the plane z =0 to be the base of the atmosphere and restrict our attention to the domain z greater than 0. The task we have is to solve for a magnetic field which is everywhere potential except on some free surface S, subject to suit able to boundary conditions. The surface S is determined by requiring that it possesses a discrete electric current density such that the Lorentz force on it is everywhere vertically upward to balance the weight of the material m(S). Since the magnetic field is potential in the external atmosphere, the latter is decoupled from the magnetic field and its plane parallel hydrostatic pressure and density can be prescribed.

Static current-sheet models of quiescent prominences

NASA Astrophysics Data System (ADS)

Wu, F.; Low, B. C.

1986-12-01

A particular class of theoretical models idealize the prominence to be a discrete flat electric-current sheet suspended vertically in a potential magnetic field. The weight of the prominence is supported by the Lorentz force in the current sheet. These models can be extended to have curved electric-current sheets and to vary three-dimensionally. The equation for force balance is 1 over 4 pi (del times B) times Bdel p- p9 z=zero. Using Cartesian coordinates we take, for simplicity, a uniform gravity with constant acceleration g in the direction -z. If we are interested not in the detailed internal structure of the prominence, but in the global magnetic configuration around the prominence, we may take prominence plasma to be cold. Consideration is given to how such equilibrium states can be constructed. To simplify the mathematical problem, suppose there is no electric current in the atmosphere except for the discrete currents in the cold prominence sheet. Let us take the plane z =0 to be the base of the atmosphere and restrict our attention to the domain z greater than 0. The task we have is to solve for a magnetic field which is everywhere potential except on some free surface S, subject to suit able to boundary conditions. The surface S is determined by requiring that it possesses a discrete electric current density such that the Lorentz force on it is everywhere vertically upward to balance the weight of the material m(S). Since the magnetic field is potential in the external atmosphere, the latter is decoupled from the magnetic field and its plane parallel hydrostatic pressure and density can be prescribed.

Effects of Diaphragmatic Breathing Patterns on Balance: A Preliminary Clinical Trial.

PubMed

Stephens, Rylee J; Haas, Mitchell; Moore, William L; Emmil, Jordan R; Sipress, Jayson A; Williams, Alex

The purpose of this study was to determine the feasibility of performing a larger study to determine if training in diaphragmatic breathing influences static and dynamic balance. A group of 13 healthy persons (8 men, 5 women), who were staff, faculty, or students at the University of Western States participated in an 8-week breathing and balance study using an uncontrolled clinical trial design. Participants were given a series of breathing exercises to perform weekly in the clinic and at home. Balance and breathing were assessed at the weekly clinic sessions. Breathing was evaluated with Liebenson's breathing assessment, static balance with the Modified Balance Error Scoring System, and dynamic balance with OptoGait's March in Place protocol. Improvement was noted in mean diaphragmatic breathing scores (1.3 to 2.6, P < .001), number of single-leg stance balance errors (7.1 to 3.8, P = .001), and tandem stance balance errors (3.2 to 0.9, P = .039). A decreasing error rate in single-leg stance was associated with improvement in breathing score within participants over the 8 weeks of the study (-1.4 errors/unit breathing score change, P < .001). Tandem stance performance did not reach statistical significance (-0.5 error/unit change, P = .118). Dynamic balance was insensitive to balance change, being error free for all participants throughout the study. This proof-of-concept study indicated that promotion of a costal-diaphragmatic breathing pattern may be associated with improvement in balance and suggests that a study of this phenomenon using an experimental design is feasible. Copyright © 2017. Published by Elsevier Inc.

An involuntary stereotypical grasp tendency pervades voluntary dynamic multifinger manipulation

PubMed Central

Rácz, Kornelius; Brown, Daniel

2012-01-01

We used a novel apparatus with three hinged finger pads to characterize collaborative multifinger interactions during dynamic manipulation requiring individuated control of fingertip motions and forces. Subjects placed the thumb, index, and middle fingertips on each hinged finger pad and held it—unsupported—with constant total grasp force while voluntarily oscillating the thumb's pad. This task combines the need to 1) hold the object against gravity while 2) dynamically reconfiguring the grasp. Fingertip force variability in this combined motion and force task exhibited strong synchrony among normal (i.e., grasp) forces. Mechanical analysis and simulation show that such synchronous variability is unnecessary and cannot be explained solely by signal-dependent noise. Surprisingly, such variability also pervaded control tasks requiring different individuated fingertip motions and forces, but not tasks without finger individuation such as static grasp. These results critically extend notions of finger force variability by exposing and quantifying a pervasive challenge to dynamic multifinger manipulation: the need for the neural controller to carefully and continuously overlay individuated finger actions over mechanically unnecessary synchronous interactions. This is compatible with—and may explain—the phenomenology of strong coupling of hand muscles when this delicate balance is not yet developed, as in early childhood, or when disrupted, as in brain injury. We conclude that the control of healthy multifinger dynamic manipulation has barely enough neuromechanical degrees of freedom to meet the multiple demands of ecological tasks and critically depends on the continuous inhibition of synchronous grasp tendencies, which we speculate may be of vestigial evolutionary origin. PMID:22956798

25. "GAFFTC 19 OCT 60, BLAST EFFECTS ON AIRFOILS, STATIC ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

25. "G-AFFTC 19 OCT 60, BLAST EFFECTS ON AIRFOILS, STATIC RUN 5." View of track rail mounting and the water brake trough at 20,000-foot track. Looking northeast. File no. 12,358-60. - Edwards Air Force Base, South Base Sled Track, Edwards Air Force Base, North of Avenue B, between 100th & 140th Streets East, Lancaster, Los Angeles County, CA

Initial Flight Tests of the NASA F-15B Propulsion Flight Test Fixture

NASA Technical Reports Server (NTRS)

Palumbo, Nathan; Moes, Timothy R.; Vachon, M. Jake

2002-01-01

Flights of the F-15B/Propulsion Flight Test Fixture (PFTF) with a Cone Drag Experiment (CDE) attached have been accomplished at NASA Dryden Flight Research Center. Mounted underneath the fuselage of an F-15B airplane, the PFTF provides volume for experiment systems and attachment points for propulsion experiments. A unique feature of the PFTF is the incorporation of a six-degree-of-freedom force balance. The force balance mounts between the PFTF and experiment and measures three forces and moments. The CDE has been attached to the force balance for envelope expansion flights. This experiment spatially and inertially simulates a large propulsion test article. This report briefly describes the F-15B airplane, the PFTF, and the force balance. A detailed description of the CDE is provided. Force-balance ground testing and stiffness modifications are described. Flight profiles and selected flight data from the envelope expansion flights are provided and discussed, including force-balance data, the internal PFTF thermal and vibration environment, a handling qualities assessment, and performance capabilities of the F-15B airplane with the PFTF installed.

Effects of aquatic physiotherapy on the improvement of balance and corporal symmetry in stroke survivors

PubMed Central

Montagna, Jéssica Cristine; Santos, Bárbara C; Battistuzzo, Camila R; Loureiro, Ana Paula C

2014-01-01

Introduction: One of the main problems associate with hemiparesis after stroke is the decrease in balance during static and dynamic postures which can highly affect daily life activities. Objective: To assess the effects of aquatic physiotherapy on the balance and quality of life (SS-QoL) of people with pos stroke. Methods: Chronic stroke participants received at total 18 individual sessions of aquatic physiotherapy using the principle of Halliwick (2x of 40 minutes per week). The outcomes measured were: Berg Balance scale, Timed up & go test (TUG), Stroke Specific Quality of Life Scale (SS-QoL) and baropodometric analysis. These assessment were performed before and one week after intervention. Results: Fifteen participants were included in this study. The mean age was 58.5 and 54% was male. After intervention, participants had a significant improvement on their static balance measured by Berg Balance scale and TUG. Dynamic balance had a significant trend of improvement in mediolateral domain with eyes closed and during sit-to-stand. The mobility domain of the SS-QoL questionnaire was significant higher after intervention. Conclusions: Our results suggest that aquatic physiotherapy using the method of Halliwick can be a useful tool during stroke rehabilitation to improve balance. However, this improvement may not have significant impact of their quality of life. PMID:24955206

Recent Investments by NASA's National Force Measurement Technology Capability

NASA Technical Reports Server (NTRS)

Commo, Sean A.; Ponder, Jonathan D.

2016-01-01

The National Force Measurement Technology Capability (NFMTC) is a nationwide partnership established in 2008 and sponsored by NASA's Aeronautics Evaluation and Test Capabilities (AETC) project to maintain and further develop force measurement capabilities. The NFMTC focuses on force measurement in wind tunnels and provides operational support in addition to conducting balance research. Based on force measurement capability challenges, strategic investments into research tasks are designed to meet the experimental requirements of current and future aerospace research programs and projects. This paper highlights recent and force measurement investments into several areas including recapitalizing the strain-gage balance inventory, developing balance best practices, improving calibration and facility capabilities, and researching potential technologies to advance balance capabilities.

Numerical simulation of the geodynamo reaches Earth's core dynamical regime

NASA Astrophysics Data System (ADS)

Aubert, J.; Gastine, T.; Fournier, A.

2016-12-01

Numerical simulations of the geodynamo have been successful at reproducing a number of static (field morphology) and kinematic (secular variation patterns, core surface flows and westward drift) features of Earth's magnetic field, making them a tool of choice for the analysis and retrieval of geophysical information on Earth's core. However, classical numerical models have been run in a parameter regime far from that of the real system, prompting the question of whether we do get "the right answers for the wrong reasons", i.e. whether the agreement between models and nature simply occurs by chance and without physical relevance in the dynamics. In this presentation, we show that classical models succeed in describing the geodynamo because their large-scale spatial structure is essentially invariant as one progresses along a well-chosen path in parameter space to Earth's core conditions. This path is constrained by the need to enforce the relevant force balance (MAC or Magneto-Archimedes-Coriolis) and preserve the ratio of the convective overturn and magnetic diffusion times. Numerical simulations performed along this path are shown to be spatially invariant at scales larger than that where the magnetic energy is ohmically dissipated. This property enables the definition of large-eddy simulations that show good agreement with direct numerical simulations in the range where both are feasible, and that can be computed at unprecedented values of the control parameters, such as an Ekman number E=10-8. Combining direct and large-eddy simulations, large-scale invariance is observed over half the logarithmic distance in parameter space between classical models and Earth. The conditions reached at this mid-point of the path are furthermore shown to be representative of the rapidly-rotating, asymptotic dynamical regime in which Earth's core resides, with a MAC force balance undisturbed by viscosity or inertia, the enforcement of a Taylor state and strong-field dynamo action. We conclude that numerical modelling has advanced to a stage where it is possible to use models correctly representing the statics, kinematics and now the dynamics of the geodynamo. This opens the way to a better analysis of the geomagnetic field in the time and space domains.

Subpercent-Scale Control of 3D Low Modes of Targets Imploded in Direct-Drive Configuration on OMEGA

NASA Astrophysics Data System (ADS)

Michel, D. T.; Igumenshchev, I. V.; Davis, A. K.; Edgell, D. H.; Froula, D. H.; Jacobs-Perkins, D. W.; Goncharov, V. N.; Regan, S. P.; Shvydky, A.; Campbell, E. M.

2018-03-01

Multiple self-emission x-ray images are used to measure tomographically target modes 1, 2, and 3 up to the end of the target acceleration in direct-drive implosions on OMEGA. Results show that the modes consist of two components: the first varies linearly with the laser beam-energy balance and the second is static and results from physical effects including beam mistiming, mispointing, and uncertainty in beam energies. This is used to reduce the target low modes of low-adiabat implosions from 2.2% to 0.8% by adjusting the beam-energy balance to compensate these static modes.

Longitudinal relationships among posturography and gait measures in multiple sclerosis.

PubMed

Fritz, Nora E; Newsome, Scott D; Eloyan, Ani; Marasigan, Rhul Evans R; Calabresi, Peter A; Zackowski, Kathleen M

2015-05-19

Gait and balance dysfunction frequently occurs early in the multiple sclerosis (MS) disease course. Hence, we sought to determine the longitudinal relationships among quantitative measures of gait and balance in individuals with MS. Fifty-seven ambulatory individuals with MS (28 relapsing-remitting, 29 progressive) were evaluated using posturography, quantitative sensorimotor and gait measures, and overall MS disability with the Expanded Disability Status Scale at each session. Our cohort's age was 45.8 ± 10.4 years (mean ± SD), follow-up time 32.8 ± 15.4 months, median Expanded Disability Status Scale score 3.5, and 56% were women. Poorer performance on balance measures was related to slower walking velocity. Two posturography measures, the anterior-posterior sway and sway during static eyes open, feet apart conditions, were significant contributors to walk velocity over time (approximate R(2) = 0.95), such that poorer performance on the posturography measures was related to slower walking velocity. Similarly, the anterior-posterior sway and sway during static eyes closed, feet together conditions were also significant contributors to the Timed 25-Foot Walk performance over time (approximate R(2) = 0.83). This longitudinal cohort study establishes a strong relationship between clinical gait measures and posturography. The data show that increases in static posturography and reductions in dynamic posturography are associated with a decline in walk velocity and Timed 25-Foot Walk performance over time. Furthermore, longitudinal balance measures predict future walking performance. Quantitative walking and balance measures are important additions to clinical testing to explore longitudinal change and understand fall risk in this progressive disease population. © 2015 American Academy of Neurology.

Relative net vertical impulse determines jumping performance.

PubMed

Kirby, Tyler J; McBride, Jeffrey M; Haines, Tracie L; Dayne, Andrea M

2011-08-01

The purpose of this investigation was to determine the relationship between relative net vertical impulse and jump height in a countermovement jump and static jump performed to varying squat depths. Ten college-aged males with 2 years of jumping experience participated in this investigation (age: 23.3 ± 1.5 years; height: 176.7 ± 4.5 cm; body mass: 84.4 ± 10.1 kg). Subjects performed a series of static jumps and countermovement jumps in a randomized fashion to a depth of 0.15, 0.30, 0.45, 0.60, and 0.75 m and a self-selected depth (static jump depth = 0.38 ± 0.08 m, countermovement jump depth = 0.49 ± 0.06 m). During the concentric phase of each jump, peak force, peak velocity, peak power, jump height, and net vertical impulse were recorded and analyzed. Net vertical impulse was divided by body mass to produce relative net vertical impulse. Increasing squat depth corresponded to a decrease in peak force and an increase in jump height and relative net vertical impulse for both static jump and countermovement jump. Across all depths, relative net vertical impulse was statistically significantly correlated to jump height in the static jump (r = .9337, p < .0001, power = 1.000) and countermovement jump (r = .925, p < .0001, power = 1.000). Across all depths, peak force was negatively correlated to jump height in the static jump (r = -0.3947, p = .0018, power = 0.8831) and countermovement jump (r = -0.4080, p = .0012, power = 0.9050). These results indicate that relative net vertical impulse can be used to assess vertical jump performance, regardless of initial squat depth, and that peak force may not be the best measure to assess vertical jump performance.

Children with ADHD Show No Deficits in Plantar Foot Sensitivity and Static Balance Compared to Healthy Controls

ERIC Educational Resources Information Center

Schlee, Gunther; Neubert, Tom; Worenz, Andreas; Milani, Thomas L.

2012-01-01

The goal of this study was to investigate plantar foot sensitivity and balance control of ADHD (n = 21) impaired children compared to age-matched healthy controls (n = 25). Thresholds were measured at 200 Hz at three anatomical locations of the plantar foot area of both feet (hallux, first metatarsal head (METI) and heel). Body balance was…

A Retrospective Analysis of Post-Stroke Berg Balance Scale Scores: How Should Normal and At-Risk Scores Be Interpreted?

PubMed Central

Inness, Elizabeth; McIlroy, William E.; Mansfield, Avril

2017-01-01

Purpose: The Berg Balance Scale (BBS) is a performance-based measure of standing balance commonly used by clinicians working with individuals post-stroke. Performance on the BBS can be influenced by compensatory strategies, but measures derived from two force plates can isolate compensatory strategies and thus better indicate balance impairment. This study examined BBS scores that reflect “normal” and disordered balance with respect to dual force-plate measures of standing balance in individuals post-stroke. Methods: BBS and force-plate measures were extracted from 75 patient charts. Individuals were classified by BBS score with respect to (1) age-matched normative values and (2) values that suggested increased risk of falls. Multiple analysis of variance was used to examine the effect of group assignment on force-plate measures of standing balance. Results: Individuals with BBS scores within and below normative values did not differ in force-plate measures. Individuals with BBS scores below the falls risk cutoff loaded their affected leg less than individuals with BBS scores above the cutoff. There were no other differences in force-plate measures between these two groups. Conclusions: BBS scores indicating either normal or disordered balance function are not necessarily associated with normal or disordered quiet standing-balance control measured by two force plates. This finding suggests that the BBS may reflect a capacity for compensation rather than any underlying impairments. PMID:28539694

Self-forces on static bodies in arbitrary dimensions

NASA Astrophysics Data System (ADS)

Taylor, Peter

2016-03-01

I will present exact expressions for the scalar and electromagnetic self-forces and self-torques acting on arbitrary static extended bodies in arbitrary static spacetimes with any number of dimensions. Non-perturbatively, these results are identical in all dimensions. Meaningful point particle limits are quite different, however. I will discuss how such limits are defined and evaluated, resulting in simple ``regularization algorithms'' which can be used in concrete calculations. In them, self-interaction is shown to be progressively less important in higher numbers of dimensions, generically competing in magnitude with increasingly high-order extended-body effects. Conversely, self-interaction effects can be relatively large in 1 + 1 and 2 + 1 dimensions. It will further be shown that there is considerable freedom to use different ``effective fields'' in the laws of motion. Different choices give rise to different inertias, gravitational forces, and electromagnetic or scalar self-forces. However, the particular combinations of these quantities which are observable remain invariant under all possible field redefinitions.

A multiphase ion-transport analysis of the electrostatic disjoining pressure: implications for binary droplet coalescence

NASA Astrophysics Data System (ADS)

Mason, Lachlan; Gebauer, Felix; Bart, Hans-Jörg; Stevens, Geoffrey; Harvie, Dalton

2016-11-01

Understanding the physics of emulsion coalescence is critical for the robust simulation of industrial solvent extraction processes, in which loaded organic and raffinate phases are separated via the coalescence of dispersed droplets. At the droplet scale, predictive collision-outcome models require an accurate description of the repulsive surface forces arising from electrical-double-layer interactions. The conventional disjoining-pressure treatment of double-layer forces, however, relies on assumptions which do not hold generally for deformable droplet collisions: namely, low interfacial curvature and negligible advection of ion species. This study investigates the validity bounds of the disjoining pressure approximation for low-inertia droplet interactions. A multiphase ion-transport model, based on a coupling of droplet-scale Nernst-Planck and Navier-Stokes equations, predicts ion-concentration fields that are consistent with the equilibrium Boltzmann distribution; indicating that the disjoining-pressure approach is valid for both static and dynamic interactions in low-Reynolds-number settings. The present findings support the development of coalescence kernels for application in macro-scale population balance modelling.

The effect of activity history and current activity on static and dynamic postural balance in older adults.

PubMed

Bulbulian, R; Hargan, M L

2000-01-01

The purpose of this study was to investigate the effects of former athleticism and current activity status on static and dynamic postural balance in older adults. Fifty-six subjects participated in four study groups including former athletes, currently active (AA; n = 15; 69.1+/-4.4 years.; 77.8+/-9.8 kg), former athletes, currently inactive (AI; n = 12; 66.7 years.; 87.2+/-15.1 kg), controls currently active (CA; n = 14; 68.6 +/- 4.5 years.; 73.9+/-15 kg), and controls currently inactive (CI; n = 15; 72.8+/-4.8 years; 81.1+/-14.8). All subjects were tested for height, weight, flexibility, thigh circumference, and static (sharpened Romberg/unipedal stance), and dynamic (step length and width) balance tests. The sharpened Romberg (eyes open) test showed that AA (60.0+/-0 s) and CA (59.4+/- 0.5 s) balanced significantly longer than AI (41.5+/-7.2 s), and CI (41.8+/-6.1 s) (p<0.05). The unipedal (eyes open) test balance scores for AA, CA, AI, and CI were respectively 40.0+/-4.5, 55.1+/- 3.4, 33.0+/-7.1, and 27.5+/-6.1 s, with CA significantly better than CI (p<0.05). In dynamic balance AA and CA (746.1+/-28.0 and 724.6+/-24.3 mm) showed significantly longer step lengths (p<0.05) than CI (643.7+/-26.5 mm). The eyes closed test results for relative group comparisons were similar. Overall, two-way analysis of variance showed a significant activity main effect for all dependent variables measured (p<0.05). The results indicated that current activity status plays a key role on balance performance in older adults. Furthermore, former athletic activity history provides no protection for the age related onset of postural imbalance.

Relationship between foot sensation and standing balance in patients with multiple sclerosis.

PubMed

Citaker, Seyit; Gunduz, Arzu Guclu; Guclu, Meral Bosnak; Nazliel, Bijen; Irkec, Ceyla; Kaya, Defne

2011-06-01

The aims of the present study were to investigate the relationship between the foot sensations and standing balance in patients with Multiple Sclerosis (MS) and find out the sensation, which best predicts balance. Twenty-seven patients with MS (Expanded Disability Status Scale 1-3.5) and 10 healthy volunteers were included. Threshold of light touch-pressure, duration of vibration, and distance of two-point discrimination of the foot sole were assessed. Duration of static one-leg standing balance was measured. Light touch-pressure, vibration, two-point discrimination sensations of the foot sole, and duration of one-leg standing balance were decreased in patients with MS compared with controls (p<0.05). Sensation of the foot sole was related with duration of one-leg standing balance in patients with MS. In the multiple regression analysis conducted in the 27 MS patients, 47.6% of the variance in the duration of one-leg standing balance was explained by two-point discrimination sensation of the heel (R(2)=0.359, p=0.001) and vibration sensation of the first metatarsal head (R(2)=0.118, p=0.029). As the cutaneous receptors sensitivity decreases in the foot sole the standing balance impairs in patients with MS. Two-point discrimination sensation of the heel and vibration sensation of the first metatarsal head region are the best predictors of the static standing balance in patients with MS. Other factors which could be possible to predict balance and effects of sensorial training of foot on balance should be investigated. Copyright © 2011 Elsevier B.V. All rights reserved.

Knee Joint Loading during Gait in Healthy Controls and Individuals with Knee Osteoarthritis

PubMed Central

Kumar, Deepak; Manal, Kurt T.; Rudolph, Katherine S.

2013-01-01

Objective People with knee osteoarthritis (OA) are thought to walk with high loads at the knee which are yet to be quantfied using modeling techniques that account for subject specific EMG patterns, kinematics and kinetics. The objective was to estimate medial and lateral loading for people with knee OA and controls using an approach that is sensitive to subject specific muscle activation patterns. Methods 16 OA and 12 control (C) subjects walked while kinematic, kinetic and EMG data were collected. Muscle forces were calculated using an EMG-Driven model and loading was calculated by balancing the external moments with internal muscle and contact forces Results OA subjects walked slower and had greater laxity, static and dynamic varus alignment, less flexion and greater knee adduction moment (KAM). Loading (normalized to body weight) was no different between the groups but OA subjects had greater absolute medial load than controls and maintained a greater %total load on the medial compartment. These patterns were associated with body mass, sagittal and frontal plane moments, static alignment and close to signficance for dynamic alignment. Lateral compartment unloading during mid-late stance was observed in 50% of OA subjects. Conclusions Loading for control subjects was similar to data from instrumented prostheses. Knee OA subjects had high medial contact loads in early stance and half of the OA cohort demonstared lateral compartment lift-off. Results suggest that interventions aimed at reducing body weight and dynamic malalignment might be effective in reducing medial compartment loading and establishing normal medio-lateral load sharing patterns. PMID:23182814

Improving approximate-optimized effective potentials by imposing exact conditions: Theory and applications to electronic statics and dynamics

NASA Astrophysics Data System (ADS)

Kurzweil, Yair; Head-Gordon, Martin

2009-07-01

We develop a method that can constrain any local exchange-correlation potential to preserve basic exact conditions. Using the method of Lagrange multipliers, we calculate for each set of given Kohn-Sham orbitals a constraint-preserving potential which is closest to the given exchange-correlation potential. The method is applicable to both the time-dependent (TD) and independent cases. The exact conditions that are enforced for the time-independent case are Galilean covariance, zero net force and torque, and Levy-Perdew virial theorem. For the time-dependent case we enforce translational covariance, zero net force, Levy-Perdew virial theorem, and energy balance. We test our method on the exchange (only) Krieger-Li-Iafrate (xKLI) approximate-optimized effective potential for both cases. For the time-independent case, we calculated the ground state properties of some hydrogen chains and small sodium clusters for some constrained xKLI potentials and Hartree-Fock (HF) exchange. The results (total energy, Kohn-Sham eigenvalues, polarizability, and hyperpolarizability) indicate that enforcing the exact conditions is not important for these cases. On the other hand, in the time-dependent case, constraining both energy balance and zero net force yields improved results relative to TDHF calculations. We explored the electron dynamics in small sodium clusters driven by cw laser pulses. For each laser pulse we compared calculations from TD constrained xKLI, TD partially constrained xKLI, and TDHF. We found that electron dynamics such as electron ionization and moment of inertia dynamics for the constrained xKLI are most similar to the TDHF results. Also, energy conservation is better by at least one order of magnitude with respect to the unconstrained xKLI. We also discuss the problems that arise in satisfying constraints in the TD case with a non-cw driving force.

Improving approximate-optimized effective potentials by imposing exact conditions: Theory and applications to electronic statics and dynamics

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

Kurzweil, Yair; Head-Gordon, Martin

2009-07-15

We develop a method that can constrain any local exchange-correlation potential to preserve basic exact conditions. Using the method of Lagrange multipliers, we calculate for each set of given Kohn-Sham orbitals a constraint-preserving potential which is closest to the given exchange-correlation potential. The method is applicable to both the time-dependent (TD) and independent cases. The exact conditions that are enforced for the time-independent case are Galilean covariance, zero net force and torque, and Levy-Perdew virial theorem. For the time-dependent case we enforce translational covariance, zero net force, Levy-Perdew virial theorem, and energy balance. We test our method on the exchangemore » (only) Krieger-Li-Iafrate (xKLI) approximate-optimized effective potential for both cases. For the time-independent case, we calculated the ground state properties of some hydrogen chains and small sodium clusters for some constrained xKLI potentials and Hartree-Fock (HF) exchange. The results (total energy, Kohn-Sham eigenvalues, polarizability, and hyperpolarizability) indicate that enforcing the exact conditions is not important for these cases. On the other hand, in the time-dependent case, constraining both energy balance and zero net force yields improved results relative to TDHF calculations. We explored the electron dynamics in small sodium clusters driven by cw laser pulses. For each laser pulse we compared calculations from TD constrained xKLI, TD partially constrained xKLI, and TDHF. We found that electron dynamics such as electron ionization and moment of inertia dynamics for the constrained xKLI are most similar to the TDHF results. Also, energy conservation is better by at least one order of magnitude with respect to the unconstrained xKLI. We also discuss the problems that arise in satisfying constraints in the TD case with a non-cw driving force.« less

Whole-body vibration training improves balance, muscle strength and glycosylated hemoglobin in elderly patients with diabetic neuropathy.

PubMed

Lee, Kyoungjin; Lee, Seungwon; Song, Changho

2013-12-01

Elderly patients with diabetes and peripheral neuropathy are more likely to experience falls. However, the information available on how such falls can be prevented is scarce. We investigated the effects of whole-body vibration (WBV) combined with a balance exercise program on balance, muscle strength, and glycosylated hemoglobin (HbA1c) in elderly patients with diabetic peripheral neuropathy. Fifty-five elderly patients with diabetic neuropathy were randomly assigned to WBV with balance exercise group, balance exercise (BE) group, and control group. The WBV and BE groups performed the balance exercise program for 60 min per day, 2 times per week, for 6 weeks. Further, the WBV group performed WBV training (up to 3 × 3 min, 3 times per week, for 6 weeks). The control group did not participate in any training. The main outcome measures were assessed at baseline and after 6 weeks of training; namely, we assessed the postural sway and one leg stance (OLS) for static balance; Berg balance scale (BBS), timed up-and-go (TUG) test, and functional reach test (FRT) for dynamic balance; five-times-sit-to-stand (FTSTS) test for muscle strength; and HbA1c for predicting the progression of diabetes. Significant improvements were noted in the static balance, dynamic balance, muscle strength, and HbA1c in the WBV group, compared to the BE and control groups (P < 0.05). Thus, in combination with the balance exercise program, the short-term WBV therapy is beneficial in improving balance, muscle strength and HbA1c, in elderly patients with diabetic neuropathy who are at high risk for suffering falls.

Balance Training Does Not Alter Reliance on Visual Information during Static Stance in Those with Chronic Ankle Instability: A Systematic Review with Meta-Analysis.

PubMed

Song, Kyeongtak; Rhodes, Evan; Wikstrom, Erik A

2018-04-01

Visual, vestibular, and somatosensory systems contribute to postural control. Chronic ankle instability (CAI) patients have been observed to have a reduced ability to dynamically shift their reliance among sources of sensory information and rely more heavily on visual information during a single-limb stance relative to uninjured controls. Balance training is proven to improve postural control but there is a lack of evidence regarding the ability of balance training programs to alter the reliance on visual information in CAI patients. Our objective was to determine if balance training alters the reliance on visual information during static stance in CAI patients. The PubMed, CINAHL, and SPORTDiscus databases were searched from their earliest available date to October 2017 using a combination of keywords. Study inclusion criteria consisted of (1) using participants with CAI; (2) use of a balance training intervention; and (3) calculation of an objective measure of static postural control during single-limb stance with eyes open and eyes closed. Sample sizes, means, and standard deviations of single-leg balance measures for eyes-open and eyes-closed testing conditions before and after balance training were extracted from the included studies. Eyes-open to eyes-closed effect sizes [Hedges' g and 95% confidence intervals (CI)] before and after balance training were calculated, and between-study variability for heterogeneity and potential risks of publication bias were examined. Six studies were identified. The overall eyes-open to eyes-closed effect size difference between pre- and post-intervention assessments was not significant (Hedges' g effect size = 0.151, 95% CI = - 0.151 to 0.453, p = 0.26). This result indicates that the utilization of visual information in individuals with CAI during the single-leg balance is not altered after balance training. Low heterogeneity (Q(5) = 2.96, p = 0.71, I 2  = 0%) of the included studies and no publication bias were found. On the basis of our systematic review with meta-analysis, it appears that traditional balance training protocols do not alter the reliance on visual information used by CAI patients during a single-leg stance.

A Developmental Study of Static Postural Control and Superimposed Arm Movements in Normal and Slowly Developing Children.

ERIC Educational Resources Information Center

Fisher, Janet M.

Selected electromyographic parameters underlying static postural control in 4, 6, and 8 year old normally and slowly developing children during performance of selected arm movements were studied. Developmental delays in balance control were assessed by the Cashin Test of Motor Development (1974) and/or the Williams Gross Motor Coordination Test…

Cryogenic Balance Technology at the National Transonic Facility

NASA Technical Reports Server (NTRS)

Parker, P. A.

2001-01-01

This paper provides an overview of force measurement at the National Transonic Facility (NTF). The NTF has unique force measurement requirements that dictate an integration of all aspects of balance design, production, and calibration. An overview of current force measurement capabilities is provided along with new balance development efforts. Research activities in the areas of thermal compensation and balance calibration are presented. Also, areas of future research are detailed.

Showing Area Matters: A Work of Friction

ERIC Educational Resources Information Center

Van Domelen, David

2010-01-01

Typically, we teach the simplified friction equation of the form F[subscript s] = [mu][subscript s]N for static friction, where F[subscript s] is the maximum static friction, [mu][subscript s] is the coefficient of static friction, and "N" is the normal force pressing the surfaces together. However, this is a bit too simplified, and…

Minimum constitutive relation error based static identification of beams using force method

NASA Astrophysics Data System (ADS)

Guo, Jia; Takewaki, Izuru

2017-05-01

A new static identification approach based on the minimum constitutive relation error (CRE) principle for beam structures is introduced. The exact stiffness and the exact bending moment are shown to make the CRE minimal for given displacements to beam damages. A two-step substitution algorithm—a force-method step for the bending moment and a constitutive-relation step for the stiffness—is developed and its convergence is rigorously derived. Identifiability is further discussed and the stiffness in the undeformed region is found to be unidentifiable. An extra set of static measurements is complemented to remedy the drawback. Convergence and robustness are finally verified through numerical examples.

Self-forces on static bodies in arbitrary dimensions

NASA Astrophysics Data System (ADS)

Harte, Abraham I.; Flanagan, Éanna É.; Taylor, Peter

2016-06-01

We derive exact expressions for the scalar and electromagnetic self-forces and self-torques acting on arbitrary static extended bodies in arbitrary static spacetimes with any number of dimensions. Nonperturbatively, our results are identical in all dimensions. Meaningful point particle limits are quite different in different dimensions, however. These limits are defined and evaluated, resulting in simple "regularization algorithms" which can be used in concrete calculations. In these limits, self-interaction is shown to be progressively less important in higher numbers of dimensions; it generically competes in magnitude with increasingly high-order extended-body effects. Conversely, we show that self-interaction effects can be relatively large in 1 +1 and 2 +1 dimensions. Our motivations for this work are twofold: First, no previous derivation of the self-force has been provided in arbitrary dimensions, and heuristic arguments presented by different authors have resulted in conflicting conclusions. Second, the static self-force problem in arbitrary dimensions provides a valuable test bed with which to continue the development of general, nonperturbative methods in the theory of motion. Several new insights are obtained in this direction, including a significantly improved understanding of the renormalization process. We also show that there is considerable freedom to use different "effective fields" in the laws of motion—a freedom which can be exploited to optimally simplify specific problems. Different choices give rise to different inertias, gravitational forces, and electromagnetic or scalar self-forces, but there is a sense in which none of these quantities are individually accessible to experiment. Certain combinations are observable, however, and these remain invariant under all possible field redefinitions.

Weber's gravitational force as static weak field approximation

NASA Astrophysics Data System (ADS)

Tiandho, Yuant

2016-02-01

Weber's gravitational force (WGF) is one of gravitational model that can accommodate a non-static system because it depends not only on the distance but also on the velocity and the acceleration. Unlike Newton's law of gravitation, WGF can predict the anomalous of Mercury and gravitational bending of light near massive object very well. Then, some researchers use WGF as an alternative model of gravitation and propose a new mechanics theory namely the relational mechanics theory. However, currently we have known that the theory of general relativity which proposed by Einstein can explain gravity with very accurate. Through the static weak field approximation for the non-relativistic object, we also have known that the theory of general relativity will reduce to Newton's law of gravity. In this work, we expand the static weak field approximation that compatible with relativistic object and we obtain a force equation which correspond to WGF. Therefore, WGF is more precise than Newton's gravitational law. The static-weak gravitational field that we used is a solution of the Einstein's equation in the vacuum that satisfy the linear field approximation. The expression of WGF with ξ = 1 and satisfy the requirement of energy conservation are obtained after resolving the geodesic equation. By this result, we can conclude that WGF can be derived from the general relativity.

The Influence of Joint Distraction Force on the Soft-Tissue Balance Using Modified Gap-Balancing Technique in Posterior-Stabilized Total Knee Arthroplasty.

PubMed

Nagai, Kanto; Muratsu, Hirotsugu; Takeoka, Yoshiki; Tsubosaka, Masanori; Kuroda, Ryosuke; Matsumoto, Tomoyuki

2017-10-01

During modified gap-balancing technique, there is no consensus on the best method for obtaining appropriate soft-tissue balance and determining the femoral component rotation. Sixty-five varus osteoarthritic patients underwent primary posterior-stabilized total knee arthroplasty using modified gap-balancing technique. The influence of joint distraction force on the soft-tissue balance measurement during the modified gap-balancing technique was evaluated with Offset Repo-Tensor between the osteotomized surfaces at extension, and between femoral posterior condyles and tibial osteotomized surface at flexion of the knee before the resection of femoral posterior condyles. The joint center gap (millimeters) and varus ligament balance (°) were measured under 20, 40, and 60 pounds of joint distraction forces, and the differences in these values at extension and flexion (the value at flexion minus the value at extension) were also calculated. The differences in joint center gap (-6.7, -6.8, and -6.9 mm for 20, 40, and 60 pounds, respectively) and varus ligament balance (3.5°, 3.8°, and 3.8°) at extension and flexion were not significantly different among different joint distraction forces, although the joint center gap and varus ligament balance significantly increased stepwise at extension and flexion as the joint distraction force increased. The difference in joint center gap and varus ligament balance at extension and flexion were consistent even among the different joint distraction forces. This novel index would be useful for the determination of femoral component rotation during the modified gap-balancing technique. Copyright © 2017 Elsevier Inc. All rights reserved.

Balance ability of 7 and 10 year old children in the population: results from a large UK birth cohort study.

PubMed

Humphriss, Rachel; Hall, Amanda; May, Margaret; Macleod, John

2011-01-01

The literature contains many reports of balance function in children, but these are often on atypical samples taken from hospital-based clinics and may not be generalisable to the population as a whole. The purpose of the present study is to describe balance test results from a large UK-based birth cohort study. Data from the Avon Longitudinal Study of Parents and Children (ALSPAC) were analysed. A total of 5402 children completed the heel-to-toe walking test at age 7 years. At age 10 years, 6915 children underwent clinical tests of balance including beam-walking, standing heel-to-toe on a beam and standing on one leg. A proportion of the children returned to the clinic for retesting within 3 months allowing test-retest agreement to be measured. Frequency distributions for each of the balance tests are given. Correlations between measures of dynamic balance at ages 7 and 10 years were weak. The static balance of 10 year old children was found to be poorer with eyes closed than with eyes open, and poorer in boys than in girls for all measures. Balance on one leg was poorer than heel-to-toe balance on a beam. A significant learning effect was found when first and second attempts of the tests were compared. Measures of static and dynamic balance appeared independent. Consistent with previous reports in the literature, test-retest reliability was found to be low. This study provides information about the balance ability of children aged 7 and 10 years and provides clinicians with reference data for balance tests commonly used in the paediatric clinic. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Workspace Safe Operation of a Force- or Impedance-Controlled Robot

NASA Technical Reports Server (NTRS)

Abdallah, Muhammad E. (Inventor); Hargrave, Brian (Inventor); Strawser, Philip A. (Inventor); Yamokoski, John D. (Inventor)

2013-01-01

A method of controlling a robotic manipulator of a force- or impedance-controlled robot within an unstructured workspace includes imposing a saturation limit on a static force applied by the manipulator to its surrounding environment, and may include determining a contact force between the manipulator and an object in the unstructured workspace, and executing a dynamic reflex when the contact force exceeds a threshold to thereby alleviate an inertial impulse not addressed by the saturation limited static force. The method may include calculating a required reflex torque to be imparted by a joint actuator to a robotic joint. A robotic system includes a robotic manipulator having an unstructured workspace and a controller that is electrically connected to the manipulator, and which controls the manipulator using force- or impedance-based commands. The controller, which is also disclosed herein, automatically imposes the saturation limit and may execute the dynamic reflex noted above.

Internet-based home training is capable to improve balance in multiple sclerosis: a randomized controlled trial.

PubMed

Frevel, D; Mäurer, M

2015-02-01

Balance disorders are common in multiple sclerosis. Aim of the study is to investigate the effectiveness of an Internet-based home training program (e-Training) to improve balance in patients with multiple sclerosis. A randomized, controlled study. Academic teaching hospital in cooperation with the therapeutic riding center Gut Üttingshof, Bad Mergentheim. Eighteen multiple sclerosis patients (mean EDSS 3,5) took part in the trial. Outcome of patients using e-Training (N.=9) was compared to the outcome of patients receiving hippotherapy (N.=9), which can be considered as an advanced concept for the improvement of balance and postural control in multiple sclerosis. After simple random allocation patients received hippotherapy or Internet-based home training (balance, postural control and strength training) twice a week for 12 weeks. Assessments were done before and after the intervention and included static and dynamic balance (primary outcome). Isometric muscle strength of the knee and trunk extension/flexion (dynamometer), walking capacity, fatigue and quality of life served as secondary outcome parameters. Both intervention groups showed comparable and highly significant improvement in static and dynamic balance capacity, no difference was seen between the both intervention groups. However looking at fatigue and quality of life only the group receiving hippotherapy improved significantly. Since e-Training shows even comparable effects to hippotherapy to improve balance, we believe that the established Internet-based home training program, specialized on balance and postural control training, is feasible for a balance and strength training in persons with multiple sclerosis. We demonstrated that Internet-based home training is possible in patients with multiple sclerosis.

Fear of falling and postural reactivity in patients with glaucoma.

PubMed

Daga, Fábio B; Diniz-Filho, Alberto; Boer, Erwin R; Gracitelli, Carolina P B; Abe, Ricardo Y; Medeiros, Felipe A

2017-01-01

To investigate the relationship between postural metrics obtained by dynamic visual stimulation in a virtual reality environment and the presence of fear of falling in glaucoma patients. This cross-sectional study included 35 glaucoma patients and 26 controls that underwent evaluation of postural balance by a force platform during presentation of static and dynamic visual stimuli with head-mounted goggles (Oculus Rift). In dynamic condition, a peripheral translational stimulus was used to induce vection and assess postural reactivity. Standard deviations of torque moments (SDTM) were calculated as indicative of postural stability. Fear of falling was assessed by a standardized questionnaire. The relationship between a summary score of fear of falling and postural metrics was investigated using linear regression models, adjusting for potentially confounding factors. Subjects with glaucoma reported greater fear of falling compared to controls (-0.21 vs. 0.27; P = 0.039). In glaucoma patients, postural metrics during dynamic visual stimulus were more associated with fear of falling (R2 = 18.8%; P = 0.001) than static (R2 = 3.0%; P = 0.005) and dark field (R2 = 5.7%; P = 0.007) conditions. In the univariable model, fear of falling was not significantly associated with binocular standard perimetry mean sensitivity (P = 0.855). In the multivariable model, each 1 Nm larger SDTM in anteroposterior direction during dynamic stimulus was associated with a worsening of 0.42 units in the fear of falling questionnaire score (P = 0.001). In glaucoma patients, postural reactivity to a dynamic visual stimulus using a virtual reality environment was more strongly associated with fear of falling than visual field testing and traditional balance assessment.

Factors Associated with the Risk of Falls of Nursing Home Residents Aged 80 or Older.

PubMed

Álvarez Barbosa, Francisco; Del Pozo-Cruz, Borja; Del Pozo-Cruz, Jesús; Alfonso-Rosa, Rosa M; Sañudo Corrales, Borja; Rogers, Michael E

2016-01-01

Falls are the leading cause of mortality and morbidity in older and represents one of the major and most costly public health problems worldwide. Evaluate the influences of lower limb muscle performance, static balance, functional independence and quality of life on fall risk as assessed with the timed up and go (TUG) test. Cross-sectional study. Fifty-two residents aged 80 or older were assessed and distributed in one of the two study groups (no risk of falls; risk of falls) according to the time to complete the TUG test. A Kistler force platform and linear transducer was used to determinate lower limb muscle performance. Postural Stability (static balance) was measured by recording the center of pressure. The EuroQol-5 dimension was used to assess Health-related quality of life and the Barthel index was used to examine functional status. Student's t-test was performed to evaluate the differences between groups. Correlations between variables were analyzed using Spearman or Pearson coefficient. ROC (receiver operating charasteristic) analysis was used to determine the cut-off points related to a decrease in the risk of a fall. Participants of no-fall risk group showed better lower limb performance, quality of life, and functional status. Cut-off points were determined for each outcome. Risk of falls in nursing home residents over the age of 80 is associated with lower limb muscle performance, functional status, and quality of Life. Cut-off points can be used by clinicians when working toward fall prevention and could help in determining the optimal lower limb muscle performance level for preventing falls. © 2015 Association of Rehabilitation Nurses.

Fear of falling and postural reactivity in patients with glaucoma

PubMed Central

Daga, Fábio B.; Diniz-Filho, Alberto; Boer, Erwin R.; Gracitelli, Carolina P. B.; Abe, Ricardo Y.; Medeiros, Felipe A.

2017-01-01

Purpose To investigate the relationship between postural metrics obtained by dynamic visual stimulation in a virtual reality environment and the presence of fear of falling in glaucoma patients. Methods This cross-sectional study included 35 glaucoma patients and 26 controls that underwent evaluation of postural balance by a force platform during presentation of static and dynamic visual stimuli with head-mounted goggles (Oculus Rift). In dynamic condition, a peripheral translational stimulus was used to induce vection and assess postural reactivity. Standard deviations of torque moments (SDTM) were calculated as indicative of postural stability. Fear of falling was assessed by a standardized questionnaire. The relationship between a summary score of fear of falling and postural metrics was investigated using linear regression models, adjusting for potentially confounding factors. Results Subjects with glaucoma reported greater fear of falling compared to controls (-0.21 vs. 0.27; P = 0.039). In glaucoma patients, postural metrics during dynamic visual stimulus were more associated with fear of falling (R2 = 18.8%; P = 0.001) than static (R2 = 3.0%; P = 0.005) and dark field (R2 = 5.7%; P = 0.007) conditions. In the univariable model, fear of falling was not significantly associated with binocular standard perimetry mean sensitivity (P = 0.855). In the multivariable model, each 1 Nm larger SDTM in anteroposterior direction during dynamic stimulus was associated with a worsening of 0.42 units in the fear of falling questionnaire score (P = 0.001). Conclusion In glaucoma patients, postural reactivity to a dynamic visual stimulus using a virtual reality environment was more strongly associated with fear of falling than visual field testing and traditional balance assessment. PMID:29211742

Flexural Fillet Geometry Optimization for Design of Force Transducers Used in Aeronautics Testing

NASA Technical Reports Server (NTRS)

Lynn, Keith C.; Dixon, Genevieve

2014-01-01

Force transducer designs used in the ground testing aeronautics community have seen minimal change over the last few decades. With increased focus on data quality and long- term performance capabilities over the life of these instruments, it is critical to investigate new methods that improve these designs. One area of focus in the past few years at NASA has been on the design of the exural elements of traditional force balance transducers. Many of the heritage balances that have been heavily used over the last few decades have started to develop fatigue cracks. The recent focus on the exural design of traditional single-piece force balances revolves around the design of these elements such that stress concentrations are minimized, with the overall goal of increasing the fatigue life of the balance. Recent research in the area of using conic shaped llets in the highly stressed regions of traditional force balances will be discussed, with preliminary numerical and experimental data results. A case study will be presented which discusses integration of this knowledge into a new high-capacity semi-span force balance

Flexural Fillet Geometry Optimization for Design of Force Transducers Used in Aeronautics Testing

NASA Technical Reports Server (NTRS)

Lynn, Keith C.; Dixon, Genevieve

2015-01-01

Force transducer designs used in the ground testing aeronautics community have seen minimal change over the last few decades. With increased focus on data quality and long-term performance capabilities over the life of these instruments, it is critical to investigate new methods that improve these designs. One area of focus in the past few years at NASA has been on the design of the flexural elements of traditional force balance transducers. Many of the heritage balances that have been heavily used over the last few decades have started to develop fatigue cracks. The recent focus on the flexural design of traditional single-piece force balances revolves around the design of these elements such that stress concentrations are minimized, with the overall goal of increasing the fatigue life of the balance. Recent research in the area of using conic shaped fillets in the highly stressed regions of traditional force balances will be discussed, with preliminary numerical and experimental data results. A case study will be presented which discusses integration of this knowledge into a new high-capacity semi-span force balance.

Dynamic Forces Between Two Deformable Oil Droplets in Water

NASA Astrophysics Data System (ADS)

Dagastine, Raymond R.; Manica, Rogério; Carnie, Steven L.; Chan, D. Y. C.; Stevens, Geoffrey W.; Grieser, Franz

2006-07-01

The understanding of static interactions in colloidal suspensions is well established, whereas dynamic interactions more relevant to biological and other suspended soft-matter systems are less well understood. We present the direct force measurement and quantitative theoretical description for dynamic forces for liquid droplets in another immiscible fluid. Analysis of this system demonstrates the strong link between interfacial deformation, static surface forces, and hydrodynamic drainage, which govern dynamic droplet-droplet interactions over the length scale of nanometers and over the time scales of Brownian collisions. The results and analysis have direct bearing on the control and manipulation of suspended droplets in soft-matter systems ranging from the emulsions in shampoo to cellular interactions.

Contact forces between a particle and a wet wall at both quasi-static and dynamic state

NASA Astrophysics Data System (ADS)

Zhang, Huang; Chen, Sheng; Li, Shuiqing

2017-06-01

The contact regime of particle-wall is investigated by the atomic force microscope (AFM) and theoretical models. First, AFM is used to measure the cohesive force between a micron-sized grain and a glass plate at quasi-static state under various humidity. It is found out that the cohesive force starts to grow slowly and suddenly increase rapidly beyond a critical Relative Humidity (RH). Second, mathematical models of contacting forces are presented to depict the dynamic process that a particle impacts on a wet wall. Then the energy loss of a falling grain is calculated in comparison with the models and the experimental data from the previous references. The simulation results show that the force models presented here are adaptive for both low and high viscosity fluid films with different thickness.

Cognitive predictors of balance in Parkinson's disease.

PubMed

Fernandes, Ângela; Mendes, Andreia; Rocha, Nuno; Tavares, João Manuel R S

2016-06-01

Postural instability is one of the most incapacitating symptoms of Parkinson's disease (PD) and appears to be related to cognitive deficits. This study aims to determine the cognitive factors that can predict deficits in static and dynamic balance in individuals with PD. A sociodemographic questionnaire characterized 52 individuals with PD for this work. The Trail Making Test, Rule Shift Cards Test, and Digit Span Test assessed the executive functions. The static balance was assessed using a plantar pressure platform, and dynamic balance was based on the Timed Up and Go Test. The results were statistically analysed using SPSS Statistics software through linear regression analysis. The results show that a statistically significant model based on cognitive outcomes was able to explain the variance of motor variables. Also, the explanatory value of the model tended to increase with the addition of individual and clinical variables, although the resulting model was not statistically significant The model explained 25-29% of the variability of the Timed Up and Go Test, while for the anteroposterior displacement it was 23-34%, and for the mediolateral displacement it was 24-39%. From the findings, we conclude that the cognitive performance, especially the executive functions, is a predictor of balance deficit in individuals with PD.

Effect of core muscle thickness and static or dynamic balance on prone bridge exercise with sling by shoulder joint angle in healthy adults.

PubMed

Park, Mi Hwa; Yu, Jae Ho; Hong, Ji Heon; Kim, Jin Seop; Jung, Sang Woo; Lee, Dong Yeop

2016-03-01

[Purpose] To date, core muscle activity detected using ultrasonography during prone bridge exercises has not been reported. Here we investigated the effects of core muscle thickness and balance on sling exercise efficacy by shoulder joint angle in healthy individuals. [Subjects and Methods] Forty-three healthy university students were enrolled in this study. Ultrasonography thickness of external oblique, internal oblique, and transversus abdominis during sling workouts was investigated. Muscle thickness was measured on ultrasonography imaging before and after the experiment. Dynamic balance was tested using a functional reaching test. Static balance was tested using a Tetrax Interactive Balance System. [Results] Different muscle thicknesses were observed during the prone bridge exercise with the shoulder flexed at 60°, 90° or 120°. Shoulder flexion at 60° and 90° in the prone bridge exercise with a sling generated the greatest thickness of most transversus abdominis muscles. Shoulder flexion at 120° in the prone bridge exercise with a sling generated the greatest thickness of most external oblique muscles. [Conclusion] The results suggest that the prone bridge exercise with shoulder joint angle is an effective method of increasing global and local muscle strength.

Ice skating promotes postural control in children.

PubMed

Keller, M; Röttger, K; Taube, W

2014-12-01

High fall rates causing injury and enormous financial costs are reported for children. However, only few studies investigated the effects of balance training in children and these studies did not find enhanced balance performance in postural (transfer) tests. Consequently, it was previously speculated that classical balance training might not be stimulating enough for children to adequately perform these exercises. Therefore, the aim of this study is to evaluate the influence of ice skating as an alternative form of balance training. Volunteers of an intervention (n = 17; INT: 13.1 ± 0.4 years) and a control group (n = 13; CON: 13.2 ± 0.3 years) were tested before and after training in static and dynamic postural transfer tests. INT participated in eight sessions of ice skating during education lessons, whereas CON participated in normal physical education. Enhanced balance performance was observed in INT but not in CON when tested on an unstable free-swinging platform (P < 0.05) or when performing a functional reach test (P < 0.001). This is the first study showing significantly enhanced balance performance after ice skating in children. More importantly, participating children improved static and dynamic balance control in postural tasks that were not part of the training. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Changes in Balancing Ability of Athletes With Chronic Ankle Instability After Foot Orthotics Application and Rehabilitation Exercises

PubMed Central

Lee, Hong-Jae; Lim, Kil-Byung; Jung, Tae-Ho; Kim, Dug-Young

2013-01-01

Objective To compare the effect of foot orthotics and rehabilitation exercises by assessing balancing ability and joint proprioception in athletes who have chronic ankle instability. Methods Forty-one athletes who visited hospitals due to chronic ankle instability were randomly assigned to two groups. One group had ankle rehabilitation exercises while the other group had the same rehabilitation exercises as well as foot orthotics. Joint position sense of the ankle joint was examined by using an isokinetic exercise machine. Balancing abilities categorized into static, dynamic and functional balance abilities were evaluated by using computerized posturography. We tested the subjects before and after the four-week rehabilitation program. Results After the four-week treatment, for joint reposition sense evaluation, external 75% angle evaluation was done, revealing that the group with the application of foot orthotics improved by -1.07±1.64 on average, showing no significant difference between the two groups (p>0.05). Static, dynamic and functional balancing abilities using balance masters were evaluated, revealing that the two groups improved in some items, but showing no significant difference between them (p>0.05). Conclusion This study found that athletes with chronic ankle instability who had foot orthotics applied for four weeks improved their proprioceptive and balancing abilities, but did not show additional treatment effects compared with rehabilitation exercise treatment. PMID:24020033

Changes in balancing ability of athletes with chronic ankle instability after foot orthotics application and rehabilitation exercises.

PubMed

Lee, Hong-Jae; Lim, Kil-Byung; Jung, Tae-Ho; Kim, Dug-Young; Park, Kyung-Rok

2013-08-01

To compare the effect of foot orthotics and rehabilitation exercises by assessing balancing ability and joint proprioception in athletes who have chronic ankle instability. Forty-one athletes who visited hospitals due to chronic ankle instability were randomly assigned to two groups. One group had ankle rehabilitation exercises while the other group had the same rehabilitation exercises as well as foot orthotics. Joint position sense of the ankle joint was examined by using an isokinetic exercise machine. Balancing abilities categorized into static, dynamic and functional balance abilities were evaluated by using computerized posturography. We tested the subjects before and after the four-week rehabilitation program. After the four-week treatment, for joint reposition sense evaluation, external 75% angle evaluation was done, revealing that the group with the application of foot orthotics improved by -1.07±1.64 on average, showing no significant difference between the two groups (p>0.05). Static, dynamic and functional balancing abilities using balance masters were evaluated, revealing that the two groups improved in some items, but showing no significant difference between them (p>0.05). This study found that athletes with chronic ankle instability who had foot orthotics applied for four weeks improved their proprioceptive and balancing abilities, but did not show additional treatment effects compared with rehabilitation exercise treatment.

NASA Ultra-Sensitive Miniature Accelerometer

NASA Technical Reports Server (NTRS)

Zavracky, Paul M.; Hartley, Frank T.

1994-01-01

Using micro-machined silicon technology, an ultra-sensitive miniature acce.,rometer can be constructed which meets the requirements for microgravity experiments in the space environment.Such an accelerometer will have a full scale sensitivity of 1C2 g a resolution of lC8 g, low cross axis sensitivity, and low temperature sensitivity. Mass of the device is approximately five grams and its footprint is 2 cm x 2 cm. Innovative features of the accelerometer, which are patented, are: electrostatic caging to withstand handling shock up to 150 g, in-situ calibration, in situ performance characterization, and both static and dynamic compensation. The transducer operates on a force balance principle wherein the displacement of the proof mass is monitored by measuring tunneling electron current flow between a conductive tip, and a fixed platen. The four major parts of the accelerometer are tip die, incorporating the tunneling tip and four field plates for controlling pitch and roll of the proof mass; two proof mass dies, attached to the surrounding frame by sets of four leg" springs; and a force plate die. The four parts are fuse-bonded into a complete assembly. External electrical connections are made at bond pads on the front surface of the force plate die. Materials and processes used in the construction of the transducer are compatible with volume production.

PIV-based estimation of unsteady loads on a flat plate at high angle of attack using momentum equation approaches

NASA Astrophysics Data System (ADS)

Guissart, Amandine; Bernal, Luis; Dimitriadis, Gregorios; Terrapon, Vincent

2015-11-01

The direct measurement of loads with force balance can become challenging when the forces are small or when the body is moving. An alternative is the use of Particle Image Velocimetry (PIV) velocity fields to indirectly obtain the aerodynamic coefficients. This can be done by the use of control volume approaches which lead to the integration of velocities, and other fields deriving from them, on a contour surrounding the studied body and its supporting surface. This work exposes and discusses results obtained with two different methods: the direct use of the integral formulation of the Navier-Stokes equations and the so-called Noca's method. The latter is a reformulation of the integral Navier-Stokes equations in order to get rid of the pressure. Results obtained using the two methods are compared and the influence of different parameters is discussed. The methods are applied to PIV data obtained from water channel testing for the flow around a 16:1 plate. Two cases are considered: a static plate at high angle of attack and a large amplitude imposed pitching motion. Two-dimensional PIV velocity fields are used to compute the aerodynamic forces. Direct measurements of dynamic loads are also carried out in order to assess the quality of the indirectly calculated coefficients.

Calibration Variable Selection and Natural Zero Determination for Semispan and Canard Balances

NASA Technical Reports Server (NTRS)

Ulbrich, Norbert M.

2013-01-01

Independent calibration variables for the characterization of semispan and canard wind tunnel balances are discussed. It is shown that the variable selection for a semispan balance is determined by the location of the resultant normal and axial forces that act on the balance. These two forces are the first and second calibration variable. The pitching moment becomes the third calibration variable after the normal and axial forces are shifted to the pitch axis of the balance. Two geometric distances, i.e., the rolling and yawing moment arms, are the fourth and fifth calibration variable. They are traditionally substituted by corresponding moments to simplify the use of calibration data during a wind tunnel test. A canard balance is related to a semispan balance. It also only measures loads on one half of a lifting surface. However, the axial force and yawing moment are of no interest to users of a canard balance. Therefore, its calibration variable set is reduced to the normal force, pitching moment, and rolling moment. The combined load diagrams of the rolling and yawing moment for a semispan balance are discussed. They may be used to illustrate connections between the wind tunnel model geometry, the test section size, and the calibration load schedule. Then, methods are reviewed that may be used to obtain the natural zeros of a semispan or canard balance. In addition, characteristics of three semispan balance calibration rigs are discussed. Finally, basic requirements for a full characterization of a semispan balance are reviewed.

The internal representation of head orientation differs for conscious perception and balance control.

PubMed

Dalton, Brian H; Rasman, Brandon G; Inglis, J Timothy; Blouin, Jean-Sébastien

2017-04-15

We tested perceived head-on-feet orientation and the direction of vestibular-evoked balance responses in passively and actively held head-turned postures. The direction of vestibular-evoked balance responses was not aligned with perceived head-on-feet orientation while maintaining prolonged passively held head-turned postures. Furthermore, static visual cues of head-on-feet orientation did not update the estimate of head posture for the balance controller. A prolonged actively held head-turned posture did not elicit a rotation in the direction of the vestibular-evoked balance response despite a significant rotation in perceived angular head posture. It is proposed that conscious perception of head posture and the transformation of vestibular signals for standing balance relying on this head posture are not dependent on the same internal representation. Rather, the balance system may operate under its own sensorimotor principles, which are partly independent from perception. Vestibular signals used for balance control must be integrated with other sensorimotor cues to allow transformation of descending signals according to an internal representation of body configuration. We explored two alternative models of sensorimotor integration that propose (1) a single internal representation of head-on-feet orientation is responsible for perceived postural orientation and standing balance or (2) conscious perception and balance control are driven by separate internal representations. During three experiments, participants stood quietly while passively or actively maintaining a prolonged head-turned posture (>10 min). Throughout the trials, participants intermittently reported their perceived head angular position, and subsequently electrical vestibular stimuli were delivered to elicit whole-body balance responses. Visual recalibration of head-on-feet posture was used to determine whether static visual cues are used to update the internal representation of body configuration for perceived orientation and standing balance. All three experiments involved situations in which the vestibular-evoked balance response was not orthogonal to perceived head-on-feet orientation, regardless of the visual information provided. For prolonged head-turned postures, balance responses consistent with actual head-on-feet posture occurred only during the active condition. Our results indicate that conscious perception of head-on-feet posture and vestibular control of balance do not rely on the same internal representation, but instead treat sensorimotor cues in parallel and may arrive at different conclusions regarding head-on-feet posture. The balance system appears to bypass static visual cues of postural orientation and mainly use other sensorimotor signals of head-on-feet position to transform vestibular signals of head motion, a mechanism appropriate for most daily activities. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Recording forces exerted on the bowel wall during colonoscopy: in vitro evaluation.

PubMed

Dogramadzi, S; Virk, G S; Bell, G D; Rowland, R S; Hancock, J

2005-12-01

A novel system for distributed force measurement between the bowel wall and the shaft of a colonoscope is presented. The system, based on the piezoresistive method, involves the integration of soft miniature transducers to a colonoscope to enable a wide range of forces to be sensed. The attached sensing sheath does not restrict the propulsion of the colonoscope nor notably alter its flexibility. The addition of the sensor sheath increases the colonoscope diameter by 15-20% depending on the type of the colonoscope (adult or paediatric). The transducer's accuracy is +/-20 grammes if it is not subjected to extensive static forces. Under large static force conditions the errors may increase to +/-50 grammes. The tactile force measuring sensors have provided preliminary results from experiments on a model of the large bowel. The force measurements confirm the predictions on the location and magnitude of the forces and that most of the forces are exerted whilst the instrument is looping. Copyright 2005 John Wiley & Sons, Ltd.

Interchangeability of the Wii Balance Board for Bipedal Balance Assessment.

PubMed

Bonnechère, Bruno; Jansen, Bart; Omelina, Lubos; Rooze, Marcel; Van Sint Jan, Serge

2015-08-27

Since 2010, an increasing interest in more portable and flexible hardware for balance and posture assessment led to previously published studies determining whether or not the Wii Balance Board could be used to assess balance and posture, both scientifically and clinically. However, no previous studies aimed at comparing results from different Wii Balance Boards for clinical balance evaluation exist. The objective of this crossover study is to assess the interchangeability of the Wii Balance Board. A total of 6 subjects participated in the study and their balance was assessed using 4 different Wii Balance Boards. Trials were recorded simultaneously with Wii Balance Boards and with a laboratory force plate. Nine relevant clinical parameters were derived from center of pressure displacement data obtained from Wii Balance Board and force plate systems. Intraclass correlation coefficients (ICC), F tests, and Friedman tests were computed to assess the agreement between trials and to compare the Wii Balance Board and force plate results. Excellent correlations were found between the Wii Balance Board and force plate (mean ρ =.83). With the exception of 2 parameters, strong to excellent agreements were found for the 7 remaining parameters (ICC=.96). No significant differences were found between trials recorded with different Wii Balance Boards. Our results indicate that for most of the parameters analyzed, balance and posture assessed with one Wii Balance Board were statistically similar to results obtained from another. Furthermore, the good correlation between the Wii Balance Board and force plate results shows that Wii Balance Boards can be reliably used for scientific assessment using most of the parameters analyzed in this study. These results also suggest that the Wii Balance Board could be used in multicenter studies and therefore, would allow for the creation of larger populations for clinical studies. Ethical Committee of the Erasme Hospital (CCB B406201215142). ©Bruno Bonnechère, Bart Jansen, Lubos Omelina, Marcel Rooze, Serge Van Sint Jan. Originally published in JMIR Rehabilitation and Assistive Technology (http://rehab.jmir.org), 27.08.2015.

Interchangeability of the Wii Balance Board for Bipedal Balance Assessment

PubMed Central

Jansen, Bart; Omelina, Lubos; Rooze, Marcel; Van Sint Jan, Serge

2015-01-01

Background Since 2010, an increasing interest in more portable and flexible hardware for balance and posture assessment led to previously published studies determining whether or not the Wii Balance Board could be used to assess balance and posture, both scientifically and clinically. However, no previous studies aimed at comparing results from different Wii Balance Boards for clinical balance evaluation exist. Objective The objective of this crossover study is to assess the interchangeability of the Wii Balance Board. Methods A total of 6 subjects participated in the study and their balance was assessed using 4 different Wii Balance Boards. Trials were recorded simultaneously with Wii Balance Boards and with a laboratory force plate. Nine relevant clinical parameters were derived from center of pressure displacement data obtained from Wii Balance Board and force plate systems. Intraclass correlation coefficients (ICC), F tests, and Friedman tests were computed to assess the agreement between trials and to compare the Wii Balance Board and force plate results. Results Excellent correlations were found between the Wii Balance Board and force plate (mean ρ =.83). With the exception of 2 parameters, strong to excellent agreements were found for the 7 remaining parameters (ICC=.96). No significant differences were found between trials recorded with different Wii Balance Boards. Conclusions Our results indicate that for most of the parameters analyzed, balance and posture assessed with one Wii Balance Board were statistically similar to results obtained from another. Furthermore, the good correlation between the Wii Balance Board and force plate results shows that Wii Balance Boards can be reliably used for scientific assessment using most of the parameters analyzed in this study. These results also suggest that the Wii Balance Board could be used in multicenter studies and therefore, would allow for the creation of larger populations for clinical studies. Trial Registration Ethical Committee of the Erasme Hospital (CCB B406201215142). PMID:28582237

Measuring center of pressure signals to quantify human balance using multivariate multiscale entropy by designing a force platform.

PubMed

Huang, Cheng-Wei; Sue, Pei-Der; Abbod, Maysam F; Jiang, Bernard C; Shieh, Jiann-Shing

2013-08-08

To assess the improvement of human body balance, a low cost and portable measuring device of center of pressure (COP), known as center of pressure and complexity monitoring system (CPCMS), has been developed for data logging and analysis. In order to prove that the system can estimate the different magnitude of different sways in comparison with the commercial Advanced Mechanical Technology Incorporation (AMTI) system, four sway tests have been developed (i.e., eyes open, eyes closed, eyes open with water pad, and eyes closed with water pad) to produce different sway displacements. Firstly, static and dynamic tests were conducted to investigate the feasibility of the system. Then, correlation tests of the CPCMS and AMTI systems have been compared with four sway tests. The results are within the acceptable range. Furthermore, multivariate empirical mode decomposition (MEMD) and enhanced multivariate multiscale entropy (MMSE) analysis methods have been used to analyze COP data reported by the CPCMS and compare it with the AMTI system. The improvements of the CPCMS are 35% to 70% (open eyes test) and 60% to 70% (eyes closed test) with and without water pad. The AMTI system has shown an improvement of 40% to 80% (open eyes test) and 65% to 75% (closed eyes test). The results indicate that the CPCMS system can achieve similar results to the commercial product so it can determine the balance.

TauG-guidance of dynamic balance control during gait initiation in patients with chronic fatigue syndrome and fibromyalgia.

PubMed

Rasouli, Omid; Stensdotter, Ann-Katrin; Van der Meer, Audrey L H

2016-08-01

Impaired postural control has been reported in static conditions in chronic fatigue syndrome and fibromyalgia, but postural control in dynamic tasks have not yet been investigated. Thus, we investigated measurements from a force plate to evaluate dynamic balance control during gait initiation in patients with chronic fatigue syndrome and fibromyalgia compared to matched healthy controls. Thirty female participants (10 per group) performed five trials of gait initiation. Center of pressure (CoP) trajectory of the initial weight shift onto the supporting foot in the mediolateral direction (CoPX) was analyzed using General Tau Theory. We investigated the hypothesis that tau of the CoPX motion-gap (τCoPx) is coupled onto an intrinsic tauG-guide (τG) by keeping the relation τCoPx=KτG, where K is a scaling factor that determines the relevant kinematics of a movement. Mean K values were 0.57, 0.55, and 0.50 in fibromyalgia, chronic fatigue syndrome, and healthy controls, respectively. Both patient groups showed K values significantly higher than 0.50 (P<0.05), indicating that patients showed poorer dynamic balance control, CoPX colliding with the boundaries of the base of support (K>0.5). The findings revealed a lower level of dynamic postural control in both fibromyalgia and chronic fatigue syndrome compared to controls. Copyright © 2016 Elsevier Ltd. All rights reserved.

Measuring Center of Pressure Signals to Quantify Human Balance Using Multivariate Multiscale Entropy by Designing a Force Platform

PubMed Central

Huang, Cheng-Wei; Sue, Pei-Der; Abbod, Maysam F.; Jiang, Bernard C.; Shieh, Jiann-Shing

2013-01-01

To assess the improvement of human body balance, a low cost and portable measuring device of center of pressure (COP), known as center of pressure and complexity monitoring system (CPCMS), has been developed for data logging and analysis. In order to prove that the system can estimate the different magnitude of different sways in comparison with the commercial Advanced Mechanical Technology Incorporation (AMTI) system, four sway tests have been developed (i.e., eyes open, eyes closed, eyes open with water pad, and eyes closed with water pad) to produce different sway displacements. Firstly, static and dynamic tests were conducted to investigate the feasibility of the system. Then, correlation tests of the CPCMS and AMTI systems have been compared with four sway tests. The results are within the acceptable range. Furthermore, multivariate empirical mode decomposition (MEMD) and enhanced multivariate multiscale entropy (MMSE) analysis methods have been used to analyze COP data reported by the CPCMS and compare it with the AMTI system. The improvements of the CPCMS are 35% to 70% (open eyes test) and 60% to 70% (eyes closed test) with and without water pad. The AMTI system has shown an improvement of 40% to 80% (open eyes test) and 65% to 75% (closed eyes test). The results indicate that the CPCMS system can achieve similar results to the commercial product so it can determine the balance. PMID:23966184

Statically determined slip-line field solution for the axial forming force estimation in the radial-axial ring rolling process

NASA Astrophysics Data System (ADS)

Quagliato, Luca; Berti, Guido A.

2017-10-01

In this paper, a statically determined slip-line solution algorithm is proposed for the calculation of the axial forming force in the radial-axial ring rolling process of flat rings. The developed solution is implemented in an Excel spreadsheet for the construction of the slip-line field and the calculation of the pressure factor to be used in the force model. The comparison between analytical solution and authors' FE simulation allows stating that the developed model supersedes the previous literature ones and proves the reliability of the proposed approach.

Stability improvement of a four cable-driven parallel manipulator using a center of mass balance system

NASA Astrophysics Data System (ADS)

Salafian, Iman; Stewart, Blake; Newman, Matthew; Zygielbaum, Arthur I.; Terry, Benjamin

2017-04-01

A four cable-driven parallel manipulator (CDPM), consisting of sophisticated spectrometers and imagers, is under development for use in acquiring phenotypic and environmental data over an acre-sized crop field. To obtain accurate and high quality data from the instruments, the end effector must be stable during sensing. One of the factors that reduces stability is the center of mass offset of the end effector, which can cause a pendulum effect or undesired tilt angle. The purpose of this work is to develop a system and method for balancing the center of mass of a 12th-scale CDPM to minimize vibration that can cause error in the acquired data. A simple method for balancing the end effector is needed to enable end users of the CDPM to arbitrarily add and remove sensors and imagers from the end effector as their experiments may require. A Center of Mass Balancing System (CMBS) is developed in this study which consists of an adjustable system of weights and a gimbal for tilt mitigation. An electronic circuit board including an orientation sensor, wireless data communication, and load cells was designed to validate the CMBS. To measure improvements gained by the CMBS, several static and dynamic experiments are carried out. In the experiments, the dynamic vibrations due to the translational motion and static orientation were measured with and without CMBS use. The results show that the CMBS system improves the stability of the end-effector by decreasing vibration and static tilt angle.

One session of high-intensity interval training (HIIT) every 5 days, improves muscle power but not static balance in lifelong sedentary ageing men

PubMed Central

Sculthorpe, Nicholas F.; Herbert, Peter; Grace, Fergal

2017-01-01

Abstract Background: Declining muscle power during advancing age predicts falls and loss of independence. High-intensity interval training (HIIT) may improve muscle power, but remains largely unstudied in ageing participants. Methods: This randomized controlled trial (RCT) investigated the efficacy of a low-frequency HIIT (LfHIIT) intervention on peak muscle power (peak power output [PPO]), body composition, and balance in lifelong sedentary but otherwise healthy males. Methods: Thirty-three lifelong sedentary ageing men were randomly assigned to either intervention (INT; n = 22, age 62.3 ± 4.1 years) or control (n = 11, age 61.6 ± 5.0 years) who were both assessed at 3 distinct measurement points (phase A), after 6 weeks of conditioning exercise (phase B), and after 6 weeks of HIIT once every 5 days in INT (phase C), where control remained inactive throughout the study. Results: Static balance remained unaffected, and both absolute and relative PPO were not different between groups at phases A or B, but increased significantly in INT after LfHIIT (P < 0.01). Lean body mass displayed a significant interaction (P < 0.01) due to an increase in INT between phases B and C (P < 0.05). Conclusions: 6 weeks of LfHIIT exercise feasible and effective method to induce clinically relevant improvements in absolute and relative PPO, but does not improve static balance in sedentary ageing men. PMID:28178145

One session of high-intensity interval training (HIIT) every 5 days, improves muscle power but not static balance in lifelong sedentary ageing men: A randomized controlled trial.

PubMed

Sculthorpe, Nicholas F; Herbert, Peter; Grace, Fergal

2017-02-01

Declining muscle power during advancing age predicts falls and loss of independence. High-intensity interval training (HIIT) may improve muscle power, but remains largely unstudied in ageing participants. This randomized controlled trial (RCT) investigated the efficacy of a low-frequency HIIT (LfHIIT) intervention on peak muscle power (peak power output [PPO]), body composition, and balance in lifelong sedentary but otherwise healthy males. Thirty-three lifelong sedentary ageing men were randomly assigned to either intervention (INT; n = 22, age 62.3 ± 4.1 years) or control (n = 11, age 61.6 ± 5.0 years) who were both assessed at 3 distinct measurement points (phase A), after 6 weeks of conditioning exercise (phase B), and after 6 weeks of HIIT once every 5 days in INT (phase C), where control remained inactive throughout the study. Static balance remained unaffected, and both absolute and relative PPO were not different between groups at phases A or B, but increased significantly in INT after LfHIIT (P < 0.01). Lean body mass displayed a significant interaction (P < 0.01) due to an increase in INT between phases B and C (P < 0.05). 6 weeks of LfHIIT exercise feasible and effective method to induce clinically relevant improvements in absolute and relative PPO, but does not improve static balance in sedentary ageing men.

Slipping and Tipping: Measuring Static Friction with a Straightedge

ERIC Educational Resources Information Center

Dietz, Eric; Aguilar, Isaac

2012-01-01

Following a discussion of forces, torques, and the conditions for static equilibrium, I tell my introductory mechanics class that I will show them how to measure the coefficient of static friction, us, between the surfaces of a block and the front bench using "nothing but a straightedge". After a few seconds of hushed anticipation, I nudge the…

Dynamic cues for whisker-based object localization: An analytical solution to vibration during active whisker touch

PubMed Central

Vaxenburg, Roman; Wyche, Isis; Svoboda, Karel; Efros, Alexander L.

2018-01-01

Vibrations are important cues for tactile perception across species. Whisker-based sensation in mice is a powerful model system for investigating mechanisms of tactile perception. However, the role vibration plays in whisker-based sensation remains unsettled, in part due to difficulties in modeling the vibration of whiskers. Here, we develop an analytical approach to calculate the vibrations of whiskers striking objects. We use this approach to quantify vibration forces during active whisker touch at a range of locations along the whisker. The frequency and amplitude of vibrations evoked by contact are strongly dependent on the position of contact along the whisker. The magnitude of vibrational shear force and bending moment is comparable to quasi-static forces. The fundamental vibration frequencies are in a detectable range for mechanoreceptor properties and below the maximum spike rates of primary sensory afferents. These results suggest two dynamic cues exist that rodents can use for object localization: vibration frequency and comparison of vibrational to quasi-static force magnitude. These complement the use of quasi-static force angle as a distance cue, particularly for touches close to the follicle, where whiskers are stiff and force angles hardly change during touch. Our approach also provides a general solution to calculation of whisker vibrations in other sensing tasks. PMID:29584719

Whole body vibration training--improving balance control and muscle endurance.

PubMed

Ritzmann, Ramona; Kramer, Andreas; Bernhardt, Sascha; Gollhofer, Albert

2014-01-01

Exercise combined with whole body vibration (WBV) is becoming increasingly popular, although additional effects of WBV in comparison to conventional exercises are still discussed controversially in literature. Heterogeneous findings are attributed to large differences in the training designs between WBV and "control" groups in regard to training volume, load and type. In order to separate the additional effects of WBV from the overall adaptations due to the intervention, in this study, a four-week WBV training setup was compared to a matched intervention program with identical training parameters in both training settings except for the exposure to WBV. In a repeated-measures matched-subject design, 38 participants were assigned to either the WBV group (VIB) or the equivalent training group (CON). Training duration, number of sets, rest periods and task-specific instructions were matched between the groups. Balance, jump height and local static muscle endurance were assessed before and after the training period. The statistical analysis revealed significant interaction effects of group×time for balance and local static muscle endurance (p<0.05). Hence, WBV caused an additional effect on balance control (pre vs. post VIB +13%, p<0.05 and CON +6%, p = 0.33) and local static muscle endurance (pre vs. post VIB +36%, p<0.05 and CON +11%, p = 0.49). The effect on jump height remained insignificant (pre vs. post VIB +3%, p = 0.25 and CON ±0%, p = 0.82). This study provides evidence for the additional effects of WBV above conventional exercise alone. As far as balance and muscle endurance of the lower leg are concerned, a training program that includes WBV can provide supplementary benefits in young and well-trained adults compared to an equivalent program that does not include WBV.

Whole Body Vibration Training - Improving Balance Control and Muscle Endurance

PubMed Central

Ritzmann, Ramona; Kramer, Andreas; Bernhardt, Sascha; Gollhofer, Albert

2014-01-01

Exercise combined with whole body vibration (WBV) is becoming increasingly popular, although additional effects of WBV in comparison to conventional exercises are still discussed controversially in literature. Heterogeneous findings are attributed to large differences in the training designs between WBV and “control” groups in regard to training volume, load and type. In order to separate the additional effects of WBV from the overall adaptations due to the intervention, in this study, a four-week WBV training setup was compared to a matched intervention program with identical training parameters in both training settings except for the exposure to WBV. In a repeated-measures matched-subject design, 38 participants were assigned to either the WBV group (VIB) or the equivalent training group (CON). Training duration, number of sets, rest periods and task-specific instructions were matched between the groups. Balance, jump height and local static muscle endurance were assessed before and after the training period. The statistical analysis revealed significant interaction effects of group×time for balance and local static muscle endurance (p<0.05). Hence, WBV caused an additional effect on balance control (pre vs. post VIB +13%, p<0.05 and CON +6%, p = 0.33) and local static muscle endurance (pre vs. post VIB +36%, p<0.05 and CON +11%, p = 0.49). The effect on jump height remained insignificant (pre vs. post VIB +3%, p = 0.25 and CON ±0%, p = 0.82). This study provides evidence for the additional effects of WBV above conventional exercise alone. As far as balance and muscle endurance of the lower leg are concerned, a training program that includes WBV can provide supplementary benefits in young and well-trained adults compared to an equivalent program that does not include WBV. PMID:24587114

A Baseline Load Schedule for the Manual Calibration of a Force Balance

NASA Technical Reports Server (NTRS)

Ulbrich, N.; Gisler, R.

2013-01-01

A baseline load schedule for the manual calibration of a force balance is defined that takes current capabilities at the NASA Ames Balance Calibration Laboratory into account. The chosen load schedule consists of 18 load series with a total of 194 data points. It was designed to satisfy six requirements: (i) positive and negative loadings should be applied for each load component; (ii) at least three loadings should be applied between 0 % and 100 % load capacity; (iii) normal and side force loadings should be applied at the forward gage location, aft gage location, and the balance moment center; (iv) the balance should be used in "up" and "down" orientation to get positive and negative axial force loadings; (v) the constant normal and side force approaches should be used to get the rolling moment loadings; (vi) rolling moment loadings should be obtained for 0, 90, 180, and 270 degrees balance orientation. In addition, three different approaches are discussed in the paper that may be used to independently estimate the natural zeros, i.e., the gage outputs of the absolute load datum of the balance. These three approaches provide gage output differences that can be used to estimate the weight of both the metric and non-metric part of the balance. Data from the calibration of a six-component force balance will be used in the final manuscript of the paper to illustrate characteristics of the proposed baseline load schedule.

A Baseline Load Schedule for the Manual Calibration of a Force Balance

NASA Technical Reports Server (NTRS)

Ulbrich, N.; Gisler, R.

2013-01-01

A baseline load schedule for the manual calibration of a force balance was developed that takes current capabilities at the NASA Ames Balance Calibration Laboratory into account. The load schedule consists of 18 load series with a total of 194 data points. It was designed to satisfy six requirements: (i) positive and negative loadings should be applied for each load component; (ii) at least three loadings should be applied between 0 % and 100 % load capacity; (iii) normal and side force loadings should be applied at the forward gage location, the aft gage location, and the balance moment center; (iv) the balance should be used in UP and DOWN orientation to get axial force loadings; (v) the constant normal and side force approaches should be used to get the rolling moment loadings; (vi) rolling moment loadings should be obtained for 0, 90, 180, and 270 degrees balance orientation. Three different approaches are also reviewed that may be used to independently estimate the natural zeros of the balance. These three approaches provide gage output differences that may be used to estimate the weight of both the metric and non-metric part of the balance. Manual calibration data of NASA s MK29A balance and machine calibration data of NASA s MC60D balance are used to illustrate and evaluate different aspects of the proposed baseline load schedule design.

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

PubMed

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

2014-01-01

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

Detailed Drawings for the Force Balance Test Apparatus

EPA Pesticide Factsheets

The American Society of Mechanical Engineers (ASME)/Canadian Standards Association (CSA) Joint Harmonization Task Force on water-efficient showerheads used the force balance test apparatus shown in these drawings.

Probing static disorder in Arrhenius kinetics by single-molecule force spectroscopy.

PubMed

Kuo, Tzu-Ling; Garcia-Manyes, Sergi; Li, Jingyuan; Barel, Itay; Lu, Hui; Berne, Bruce J; Urbakh, Michael; Klafter, Joseph; Fernández, Julio M

2010-06-22

The widely used Arrhenius equation describes the kinetics of simple two-state reactions, with the implicit assumption of a single transition state with a well-defined activation energy barrier DeltaE, as the rate-limiting step. However, it has become increasingly clear that the saddle point of the free-energy surface in most reactions is populated by ensembles of conformations, leading to nonexponential kinetics. Here we present a theory that generalizes the Arrhenius equation to include static disorder of conformational degrees of freedom as a function of an external perturbation to fully account for a diverse set of transition states. The effect of a perturbation on static disorder is best examined at the single-molecule level. Here we use force-clamp spectroscopy to study the nonexponential kinetics of single ubiquitin proteins unfolding under force. We find that the measured variance in DeltaE shows both force-dependent and independent components, where the force-dependent component scales with F(2), in excellent agreement with our theory. Our study illustrates a novel adaptation of the classical Arrhenius equation that accounts for the microscopic origins of nonexponential kinetics, which are essential in understanding the rapidly growing body of single-molecule data.

Force instrumentation for cryogenic wind tunnels using one-piece strain-gage balances

NASA Technical Reports Server (NTRS)

Ferris, A. T.

1980-01-01

The use of cryogenic temperatures in wind tunnels to achieve high Reynolds numbers has imposed a harsh operating environment on the force balance. Laboratory tests were conducted to study the effect cryogenic temperatures have on balance materials, gages, wiring, solder, adhesives, and moisture proofing. Wind tunnel tests were conducted using a one piece three component balance to verify laboratory results. These initial studies indicate that satisfactory force data can be obtained under steady state conditions.

Assessment of a flow-through balance for hypersonic wind tunnel models with scramjet exhaust flow simulation

NASA Technical Reports Server (NTRS)

Huebner, Lawrence D.; Kniskern, Marc W.; Monta, William J.

1993-01-01

The purpose of this investigation were twofold: first, to determine whether accurate force and moment data could be obtained during hypersonic wind tunnel tests of a model with a scramjet exhaust flow simulation that uses a representative nonwatercooled, flow-through balance; second, to analyze temperature time histories on various parts of the balance to address thermal effects on force and moment data. The tests were conducted in the NASA Langley Research Center 20-Inch Mach 6 Wind Tunnel at free-stream Reynolds numbers ranging from 0.5 to 7.4 x 10(exp 6)/ft and nominal angles of attack of -3.5 deg, 0 deg, and 5 deg. The simulant exhaust gases were cold air, hot air, and a mixture of 50 percent Argon and 50 percent Freon by volume, which reached stagnation temperatures within the balance of 111, 214, and 283 F, respectively. All force and moment values were unaffected by the balance thermal response from exhaust gas simulation and external aerodynamic heating except for axial-force measurements, which were significantly affected by balance heating. This investigation showed that for this model at the conditions tested, a nonwatercooled, flow-through balance is not suitable for axial-force measurements during scramjet exhaust flow simulation tests at hypersonic speeds. In general, heated exhaust gas may produce unacceptable force and moment uncertainties when used with thermally sensitive balances.

The effects of dance training program on the postural stability of middle aged women.

PubMed

Kostić, Radmila; Uzunović, Slavoljub; Purenović-Ivanović, Tijana; Miletić, Đurđica; Katsora, Georgija; Pantelić, Saša; Milanović, Zoran

2015-11-01

The aim of the study was to determine the effects of Greek folk dancing on postural stability in middle age women. Sixty-three women aged from 47-53 participated in this study. All participants were randomly divided into the experimental group - 33 participants (mean ± SD; body height=160.13 ± 12.07 cm, body mass=63.81 ± 10.56 kg), and the control group - 30 participants (mean ± SD; body height=160.63 ± 6.22 cm, body mass=64.79 ± 8.19 kg). The following tests were used to evaluate the motor balance and posture stability of participants; the double-leg stance along the length of a balance beam (eyes open), the double-leg stance along the width of a balance beam (eyes open), the single-leg stance (eyes open) and the double-leg stance on one's toes (eyes closed). The Functional Reach Test for balance and the Star Excursion Balance Test were used to evaluate dynamic balance. The multivariate analysis of covariance of static and dynamic balance between participants of the experimental and control group at the final measuring, with neutralized differences at the initial measuring (Wilks' λ=0.45), revealed a significant difference (p<0.05). The intergroup difference at the final measuring was also found to be significant (p<0.05) for the following variables; the double-leg stance on one's toes, the Functional Reach Test, balance of the right anterolateral, balance of the right posterolateral and balance of the left posteromedial. An organized dance activity programme does lead to the improvement of static and dynamic balance in middle aged women. Copyright© by the National Institute of Public Health, Prague 2015.

The combination of plyometric and balance training improves sprint and shuttle run performances more often than plyometric-only training with children.

PubMed

Chaouachi, Anis; Othman, Aymen Ben; Hammami, Raouf; Drinkwater, Eric J; Behm, David G

2014-02-01

Because balance is not fully developed in children and studies have shown functional improvements with balance only training studies, a combination of plyometric and balance activities might enhance static balance, dynamic balance, and power. The objective of this study was to compare the effectiveness of plyometric only (PLYO) with balance and plyometric (COMBINED) training on balance and power measures in children. Before and after an 8-week training period, testing assessed lower-body strength (1 repetition maximum leg press), power (horizontal and vertical jumps, triple hop for distance, reactive strength, and leg stiffness), running speed (10-m and 30-m sprint), static and dynamic balance (Standing Stork Test and Star Excursion Balance Test), and agility (shuttle run). Subjects were randomly divided into 2 training groups (PLYO [n = 14] and COMBINED [n = 14]) and a control group (n = 12). Results based on magnitude-based inferences and precision of estimation indicated that the COMBINED training group was considered likely to be superior to the PLYO group in leg stiffness (d = 0.69, 91% likely), 10-m sprint (d = 0.57, 84% likely), and shuttle run (d = 0.52, 80% likely). The difference between the groups was unclear in 8 of the 11 dependent variables. COMBINED training enhanced activities such as 10-m sprints and shuttle runs to a greater degree. COMBINED training could be an important consideration for reducing the high velocity impacts of PLYO training. This reduction in stretch-shortening cycle stress on neuromuscular system with the replacement of balance and landing exercises might help to alleviate the overtraining effects of excessive repetitive high load activities.

Integrated dynamic and static tactile sensor: focus on static force sensing

NASA Astrophysics Data System (ADS)

Wettels, Nicholas; Pletner, Baruch

2012-04-01

Object grasping by robotic hands in unstructured environments demands a sensor that is durable, compliant, and responsive to static and dynamic force conditions. In order for a tactile sensor to be useful for grasp control in these, it should have the following properties: tri-axial force sensing (two shear plus normal component), dynamic event sensing across slip frequencies, compliant surface for grip, wide dynamic range (depending on application), insensitivity to environmental conditions, ability to withstand abuse and good sensing behavior (e.g. low hysteresis, high repeatability). These features can be combined in a novel multimodal tactile sensor. This sensor combines commercial-off-the-shelf MEMS technology with two proprietary force sensors: a high bandwidth device based on PZT technology and low bandwidth device based on elastomers and optics. In this study, we focus on the latter transduction mechanism and the proposed architecture of the completed device. In this study, an embedded LED was utilized to produce a constant light source throughout a layer of silicon rubber which covered a plastic mandrel containing a set of sensitive phototransistors. Features about the contacted object such as center of pressure and force vectors can be extracted from the information in the changing patterns of light. The voltage versus force relationship obtained with this molded humanlike finger had a wide dynamic range that coincided with forces relevant for most human grip tasks.

Comparison of quasi-static and dynamic squats: a three-dimensional kinematic, kinetic and electromyographic study of the lower limbs.

PubMed

Clément, Julien; Hagemeister, Nicola; Aissaoui, Rachid; de Guise, Jacques A

2014-01-01

Numerous studies have described 3D kinematics, 3D kinetics and electromyography (EMG) of the lower limbs during quasi-static or dynamic squatting activities. One study compared these two squatting conditions but only at low speed on healthy subjects, and provided no information on kinetics and EMG of the lower limbs. The purpose of the present study was to contrast simultaneous recordings of 3D kinematics, 3D kinetics and EMG of the lower limbs during quasi-stat ic and fast-dynamic squats in healthy and pathological subjects. Ten subjects were recruited: five healthy and five osteoarthritis subjects. A motion-capture system, force plate, and surface electrodes respectively recorded 3D kinematics, 3D kinetics and EMG of the lower limbs. Each subject performed a quasi-static squat and several fast-dynamic squats from 0° to 70° of knee flexion. The two squatting conditions were compared for positions where quasi-static and fast-dynamic knee flexion-extension angles were similar. Mean differences between quasi-static and fast-dynamic squats were 1.5° for rotations, 1.9 mm for translations, 2.1% of subjects' body weight for ground reaction forces, 6.6 Nm for torques, 11.2 mm for center of pressure, and 6.3% of maximum fast-dynamic electromyographic activities for EMG. Some significant differences (p<0.05) were found in internal rotation, anterior translation, vertical force and EMG. All differences between quasi-static and fast-dynamic squats were small. 69.5% of compared data were equivalent. In conclusion, this study showed that quasi-static and fast-dynamic squatting activities are comparable in terms of 3D kinematics, 3D kinetics and EMG, although some reservations still remain. Copyright © 2014 Elsevier B.V. All rights reserved.

TIGER: Development of Thermal Gradient Compensation Algorithms and Techniques

NASA Technical Reports Server (NTRS)

Hereford, James; Parker, Peter A.; Rhew, Ray D.

2004-01-01

In a wind tunnel facility, the direct measurement of forces and moments induced on the model are performed by a force measurement balance. The measurement balance is a precision-machined device that has strain gages at strategic locations to measure the strain (i.e., deformations) due to applied forces and moments. The strain gages convert the strain (and hence the applied force) to an electrical voltage that is measured by external instruments. To address the problem of thermal gradients on the force measurement balance NASA-LaRC has initiated a research program called TIGER - Thermally-Induced Gradients Effects Research. The ultimate goals of the TIGER program are to: (a) understand the physics of the thermally-induced strain and its subsequent impact on load measurements and (b) develop a robust thermal gradient compensation technique. This paper will discuss the impact of thermal gradients on force measurement balances, specific aspects of the TIGER program (the design of a special-purpose balance, data acquisition and data analysis challenges), and give an overall summary.

Single-Vector Calibration of Wind-Tunnel Force Balances

NASA Technical Reports Server (NTRS)

Parker, P. A.; DeLoach, R.

2003-01-01

An improved method of calibrating a wind-tunnel force balance involves the use of a unique load application system integrated with formal experimental design methodology. The Single-Vector Force Balance Calibration System (SVS) overcomes the productivity and accuracy limitations of prior calibration methods. A force balance is a complex structural spring element instrumented with strain gauges for measuring three orthogonal components of aerodynamic force (normal, axial, and side force) and three orthogonal components of aerodynamic torque (rolling, pitching, and yawing moments). Force balances remain as the state-of-the-art instrument that provide these measurements on a scale model of an aircraft during wind tunnel testing. Ideally, each electrical channel of the balance would respond only to its respective component of load, and it would have no response to other components of load. This is not entirely possible even though balance designs are optimized to minimize these undesirable interaction effects. Ultimately, a calibration experiment is performed to obtain the necessary data to generate a mathematical model and determine the force measurement accuracy. In order to set the independent variables of applied load for the calibration 24 NASA Tech Briefs, October 2003 experiment, a high-precision mechanical system is required. Manual deadweight systems have been in use at Langley Research Center (LaRC) since the 1940s. These simple methodologies produce high confidence results, but the process is mechanically complex and labor-intensive, requiring three to four weeks to complete. Over the past decade, automated balance calibration systems have been developed. In general, these systems were designed to automate the tedious manual calibration process resulting in an even more complex system which deteriorates load application quality. The current calibration approach relies on a one-factor-at-a-time (OFAT) methodology, where each independent variable is incremented individually throughout its full-scale range, while all other variables are held at a constant magnitude. This OFAT approach has been widely accepted because of its inherent simplicity and intuitive appeal to the balance engineer. LaRC has been conducting research in a "modern design of experiments" (MDOE) approach to force balance calibration. Formal experimental design techniques provide an integrated view to the entire calibration process covering all three major aspects of an experiment; the design of the experiment, the execution of the experiment, and the statistical analyses of the data. In order to overcome the weaknesses in the available mechanical systems and to apply formal experimental techniques, a new mechanical system was required. The SVS enables the complete calibration of a six-component force balance with a series of single force vectors.

In-Situ Load System for Calibrating and Validating Aerodynamic Properties of Scaled Aircraft in Ground-Based Aerospace Testing Applications

NASA Technical Reports Server (NTRS)

Lynn, Keith C. (Inventor); Acheson, Michael J. (Inventor); Commo, Sean A. (Inventor); Landman, Drew (Inventor)

2016-01-01

An In-Situ Load System for calibrating and validating aerodynamic properties of scaled aircraft in ground-based aerospace testing applications includes an assembly having upper and lower components that are pivotably interconnected. A test weight can be connected to the lower component to apply a known force to a force balance. The orientation of the force balance can be varied, and the measured forces from the force balance can be compared to applied loads at various orientations to thereby develop calibration factors.

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

PubMed

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

2017-07-01

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

On the origin of why static or breakloose friction is larger than kinetic friction, and how to reduce it: the role of aging, elasticity and sequential interfacial slip.

PubMed

Lorenz, B; Persson, B N J

2012-06-06

We discuss the origin of static friction and show how it can be reduced towards kinetic friction by the appropriate design of the sliding system. The basic idea is to use elastically soft solids and apply the external forces in such a way that different parts of the contacting interface start to slip at different times during the (tangential) loading process. In addition, the local slip must be large enough in order to result in a strong drop in the static friction force. We illustrate the theoretical predictions with the results of a simple model experiment.

Enhanced balance associated with coordination training with stochastic resonance stimulation in subjects with functional ankle instability: an experimental trial.

PubMed

Ross, Scott E; Arnold, Brent L; Blackburn, J Troy; Brown, Cathleen N; Guskiewicz, Kevin M

2007-12-17

Ankle sprains are common injuries that often lead to functional ankle instability (FAI), which is a pathology defined by sensations of instability at the ankle and recurrent ankle sprain injury. Poor postural stability has been associated with FAI, and sports medicine clinicians rehabilitate balance deficits to prevent ankle sprains. Subsensory electrical noise known as stochastic resonance (SR) stimulation has been used in conjunction with coordination training to improve dynamic postural instabilities associated with FAI. However, unlike static postural deficits, dynamic impairments have not been indicative of ankle sprain injury. Therefore, the purpose of this study was to examine the effects of coordination training with or without SR stimulation on static postural stability. Improving postural instabilities associated with FAI has implications for increasing ankle joint stability and decreasing recurrent ankle sprains. This study was conducted in a research laboratory. Thirty subjects with FAI were randomly assigned to either a: 1) conventional coordination training group (CCT); 2) SR stimulation coordination training group (SCT); or 3) control group. Training groups performed coordination exercises for six weeks. The SCT group received SR stimulation during training, while the CCT group only performed coordination training. Single leg postural stability was measured after the completion of balance training. Static postural stability was quantified on a force plate using anterior/posterior (A/P) and medial/lateral (M/L) center-of-pressure velocity (COPvel), M/L COP standard deviation (COPsd), M/L COP maximum excursion (COPmax), and COP area (COParea). Treatment effects comparing posttest to pretest COP measures were highest for the SCT group. At posttest, the SCT group had reduced A/P COPvel (2.3 +/- 0.4 cm/s vs. 2.7 +/- 0.6 cm/s), M/L COPvel (2.6 +/- 0.5 cm/s vs. 2.9 +/- 0.5 cm/s), M/L COPsd (0.63 +/- 0.12 cm vs. 0.73 +/- 0.11 cm), M/L COPmax (1.76 +/- 0.25 cm vs. 1.98 +/- 0.25 cm), and COParea (0.13 +/- 0.03 cm2 vs. 0.16 +/- 0.04 cm2) than the pooled means of the CCT and control groups (P < 0.05). Reduced values in COP measures indicated postural stability improvements. Thus, six weeks of coordination training with SR stimulation enhanced postural stability. Future research should examine the use of SR stimulation for decreasing recurrent ankle sprain injury in physically active individuals with FAI.

Enhanced balance associated with coordination training with stochastic resonance stimulation in subjects with functional ankle instability: an experimental trial

PubMed Central

Ross, Scott E; Arnold, Brent L; Blackburn, J Troy; Brown, Cathleen N; Guskiewicz, Kevin M

2007-01-01

Background Ankle sprains are common injuries that often lead to functional ankle instability (FAI), which is a pathology defined by sensations of instability at the ankle and recurrent ankle sprain injury. Poor postural stability has been associated with FAI, and sports medicine clinicians rehabilitate balance deficits to prevent ankle sprains. Subsensory electrical noise known as stochastic resonance (SR) stimulation has been used in conjunction with coordination training to improve dynamic postural instabilities associated with FAI. However, unlike static postural deficits, dynamic impairments have not been indicative of ankle sprain injury. Therefore, the purpose of this study was to examine the effects of coordination training with or without SR stimulation on static postural stability. Improving postural instabilities associated with FAI has implications for increasing ankle joint stability and decreasing recurrent ankle sprains. Methods This study was conducted in a research laboratory. Thirty subjects with FAI were randomly assigned to either a: 1) conventional coordination training group (CCT); 2) SR stimulation coordination training group (SCT); or 3) control group. Training groups performed coordination exercises for six weeks. The SCT group received SR stimulation during training, while the CCT group only performed coordination training. Single leg postural stability was measured after the completion of balance training. Static postural stability was quantified on a force plate using anterior/posterior (A/P) and medial/lateral (M/L) center-of-pressure velocity (COPvel), M/L COP standard deviation (COPsd), M/L COP maximum excursion (COPmax), and COP area (COParea). Results Treatment effects comparing posttest to pretest COP measures were highest for the SCT group. At posttest, the SCT group had reduced A/P COPvel (2.3 ± 0.4 cm/s vs. 2.7 ± 0.6 cm/s), M/L COPvel (2.6 ± 0.5 cm/s vs. 2.9 ± 0.5 cm/s), M/L COPsd (0.63 ± 0.12 cm vs. 0.73 ± 0.11 cm), M/L COPmax (1.76 ± 0.25 cm vs. 1.98 ± 0.25 cm), and COParea (0.13 ± 0.03 cm2 vs. 0.16 ± 0.04 cm2) than the pooled means of the CCT and control groups (P < 0.05). Conclusion Reduced values in COP measures indicated postural stability improvements. Thus, six weeks of coordination training with SR stimulation enhanced postural stability. Future research should examine the use of SR stimulation for decreasing recurrent ankle sprain injury in physically active individuals with FAI. PMID:18086314

Lift, drag and thrust measurement in a hypersonic impulse facility

NASA Technical Reports Server (NTRS)

Tuttle, S. L.; Mee, D. J.; Simmons, J. M.

1995-01-01

This paper reports the extension of the stress wave force balance to the measurement of forces on models which are non-axisymmetric or which have non-axisymmetric load distributions. Recent results are presented which demonstrate the performance of the stress wave force balance for drag measurement, for three-component force measurement and preliminary results for thrust measurement on a two-dimensional scramjet nozzle. In all cases, the balances respond within a few hundred microseconds.

Levitation force of melt-textured YBCO superconductors under non-quasi-static situation

NASA Astrophysics Data System (ADS)

Zhao, Z. M.; Xu, J. M.; Yuan, X. Y.; Zhang, C. P.

2018-06-01

The superconducting levitation force of a simple superconductor-magnet system under non-quasi-static situation is investigated experimentally. Two yttrium barium copper oxide (YBCO) samples with different performances are chosen from two small batches of samples prepared by the top-seeded melt-textured growth process. The residual carbon content of the precursor powders of the two batches is different due to different heat treatment processes. During the experimental process for measuring the levitation force, the value of the relative speed between the YBCO sample and the permanent magnet is higher than that in conventional studies. The variation characteristics of the superconducting levitation force are analyzed and a crossing phenomenon in the force-displacement hysteresis curves is observed. The results indicate that the superconducting levitation force is different due to the different residual carbon contents. As residual carbon contents reduce, the crossing phenomenon is more obvious accordingly.

Creation

NASA Astrophysics Data System (ADS)

Terry, Bruce

2003-04-01

An infinity of pure, non-moving space did not need to be created. What would or could replace it? The Self-Creating Universe* explains exactly the importance of why this infinity of space was static and how static space converted itself to first movement thus creating the two equal but opposite forces necessary for cosmic evolution to begin. This process provided the atmosphere for a self-causing third force to develope. The third force, in conjunction with the original two forces, became the background that triggered the creation of the physical forces. The derivatives of this action/re-action allowed all of the known cosmos to complete itself. All processes of movement constituting the cosmos, whether it be compression (creating density) or expansion (drawing a vacuum), must involve two or more of the three original forces. The full abstract of The Self-Creating Universe* theory, can be found at http://www.scuinc.com. *copyright by Bruce Terry All Rights Reserved

Clinical balance tests, proprioceptive system and adolescent idiopathic scoliosis.

PubMed

Le Berre, Morgane; Guyot, Marc-Alexandre; Agnani, Olivier; Bourdeauducq, Isabelle; Versyp, Marie-Christine; Donze, Cécile; Thévenon, André; Catanzariti, Jean-Francois

2017-06-01

Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of the spinal column of unknown etiology. Multiple factors could be involved, including neurosensory pathways and, potentially, an elective disorder of dynamic proprioception. The purpose of this study was to determine whether routine balance tests could be used to demonstrate an elective alteration of dynamic proprioception in AIS. This was a multicentre case-control study based on prospectively collected clinical data, in three hospitals pediatric, with spine consultation, from January 2013 through April 2015. From an original population of 547 adolescents, inclusion and non-inclusion criteria indentified 114 adolescents with right thoracic AIS (mean age 14.5 ± 1.9 years, Cobb angle 35.7 ± 15.3°) and 81 matched adolescents without scoliosis (mean age 14.1 ± 1.9 years). Participants performed three routine clinical balance tests to assess the static and dynamic proprioception: the Fukuda-Utenberger stepping test (angle of rotation in degrees and distance of displacement in cm) to assess dynamic balance; the sharpened Romberg test and the unipedal stance test (eyes closed) to assess static balance. There was no significant difference between AIS subjects and controls for the static tests, but there was a significant difference for the dynamic test for both measures: distance of displacement (p < 0.01) and angle of rotation (p < 0.0001). This result confirms our initial these: the dynamic proprioception is altered electively in AIS. These findings confirm recent AIS studies. Our results might be related to immature central integration of dynamic proprioceptive input leading to a poorly adapted motor response, particularly for postural control of the, in AIS. These balance tests can be performed in routine practice. Their validity as a biomarker for screening and monitoring purposes should be assessed.

On the expected relationships among apparent stress, static stress drop, effective shear fracture energy, and efficiency

USGS Publications Warehouse

Beeler, N.M.; Wong, T.-F.; Hickman, S.H.

2003-01-01

We consider expected relationships between apparent stress ??a and static stress drop ????s using a standard energy balance and find ??a = ????s (0.5 - ??), where ?? is stress overshoot. A simple implementation of this balance is to assume overshoot is constant; then apparent stress should vary linearly with stress drop, consistent with spectral theories (Brune, 1970) and dynamic crack models (Madariaga, 1976). Normalizing this expression by the static stress drop defines an efficiency ??sw = ??sa/????s as follows from Savage and Wood (1971). We use this measure of efficiency to analyze data from one of a number of observational studies that find apparent stress to increase with seismic moment, namely earthquakes recorded in the Cajon Pass borehole by Abercrombie (1995). Increases in apparent stress with event size could reflect an increase in seismic efficiency; however, ??sw for the Cajon earthquakes shows no such increase and is approximately constant over the entire moment range. Thus, apparent stress and stress drop co-vary, as expected from the energy balance at constant overshoot. The median value of ??sw for the Cajon earthquakes is four times lower than ??sw for laboratory events. Thus, these Cajon-recorded earthquakes have relatively low and approximately constant efficiency. As the energy balance requires ??sw = 0.5 - ??, overshoot can be estimated directly from the Savage-Wood efficiency; overshoot is positive for Cajon Pass earthquakes. Variations in apparent stress with seismic moment for these earthquakes result primarily from systematic variations in static stress drop with seismic moment and do not require a relative decrease in sliding resistance with increasing event size (dynamic weakening). Based on the comparison of field and lab determinations of the Savage-Wood efficiency, we suggest the criterion ??sw > 0.3 as a test for dynamic weakening in excess of that seen in the lab.

Age-related changes in physical fall risk factors: results from a 3 year follow-up of community dwelling older adults in Tasmania, Australia.

PubMed

Bird, Marie-Louise; Pittaway, Jane K; Cuisick, Isobel; Rattray, Megan; Ahuja, Kiran D K

2013-11-11

As the population ages, fall rates are expected to increase, leading to a rise in accidental injury and injury-related deaths, and placing an escalating burden on health care systems. Sixty-nine independent community-dwelling adults (60-85 years, 18 males) had their leg strength, physical activity levels and their annual fall rate assessed at two timepoints over three years, (summer 2010 and summer 2013) monitoring balance. Force platform measures of medio-lateral sway range increased significantly under conditions of eyes open (mean difference MD 2.5 cm; 95% CI 2.2 to 2.8 cm) and eyes closed (MD 3.2 cm; 95% CI 2.8 to 3.6 cm), respectively (all p < 0.001) indicating worsening static balance control. Dynamic balance showed similar changes (p < 0.036). Leg strength was not significantly different between visits (p > 0.26). Physical activity reduced significantly (MD -909 Cal/week; 95% CI -347 to -1,470 Cal/week; p = 0.002) during the course of the study. Participants maintained aerobic activities, however resistance and balance exercise levels decreased non-significantly. The likelihood of falling was higher at the end of the study compared to the first timepoint (odds ratio 1.93, 95% CI 0.94 to 3.94; p = 0.07). Results of this study indicate that despite maintenance of leg strength there was an increase in medio-lateral sway over a relatively short time frame, with higher than expected increases in fall rates.

Systematic study of error sources in supersonic skin-friction balance measurements

NASA Technical Reports Server (NTRS)

Allen, J. M.

1976-01-01

An experimental study was performed to investigate potential error sources in data obtained with a self-nulling, moment-measuring, skin-friction balance. The balance was installed in the sidewall of a supersonic wind tunnel, and independent measurements of the three forces contributing to the balance output (skin friction, lip force, and off-center normal force) were made for a range of gap size and element protrusion. The relatively good agreement between the balance data and the sum of these three independently measured forces validated the three-term model used. No advantage to a small gap size was found; in fact, the larger gaps were preferable. Perfect element alignment with the surrounding test surface resulted in very small balance errors. However, if small protrusion errors are unavoidable, no advantage was found in having the element slightly below the surrounding test surface rather than above it.

SACCON Forced Oscillation Tests at DNW-NWB and NASA Langley 14x22-Foot Tunnel

NASA Technical Reports Server (NTRS)

Vicroy Dan D.; Loeser, Thomas D.; Schuette, Andreas

2010-01-01

A series of three wind tunnel static and forced oscillation tests were conducted on a generic unmanned combat air vehicle (UCAV) geometry. These tests are part of an international research effort to assess the state-of-the-art of computational fluid dynamics (CFD) methods to predict the static and dynamic stability and control characteristics. The experimental dataset includes not only force and moment time histories but surface pressure and off body particle image velocimetry measurements as well. The extent of the data precludes a full examination within the scope of this paper. This paper provides some examples of the dynamic force and moment data available as well as some of the observed trends.

Constitutive models for static and dynamic response of geotechnical materials

NASA Astrophysics Data System (ADS)

Nemat-Nasser, S.

1983-11-01

The objective of this research program has been to develop realistic macroscopic constitutive relations which describe static and dynamic properties of geotechnical materials (soils and rocks). To this end a coordinated theoretical and experimental activity has been followed. The theoretical work includes a balanced combination of statistical microscopic (at the grain size level) modeling and a nonclassical elasto-plastic macroscopic formulation. The latter includes the effects of internal friction, plastic compressibility, and pressure sensitivity, as well as anisotropy which is commonly observed in geotechnical materials. The following specific goals have been sought: (1) to develop three-dimensional constitutive relations under ordinary or high pressures (such as those induced by blasting or tectonic forces which may cause a large amount of densification by relative motion and possible crushing of grains); and (2) to examine and characterize the behavior of saturated granular materials under dynamic loading. The latter item includes characterization of possible liquefaction and subsidence which may be induced in granular materials under confining pressure by ground vibration or passage of waves. The theoretical work has been carefully coordinated with key experiments in order to: (1) understand the basic physics of the process, both at macroscopic and microscopic levels; (2) to verify the corresponding theoretical predictions; and (3) to establish relevant material parameters.

Comparison of forcing functions in magnetohydrodynamics

NASA Astrophysics Data System (ADS)

McKay, Mairi E.; Linkmann, Moritz; Clark, Daniel; Chalupa, Adam A.; Berera, Arjun

2017-11-01

Results are presented of direct numerical simulations of incompressible, homogeneous magnetohydrodynamic turbulence without a mean magnetic field, subject to different mechanical forcing functions commonly used in the literature. Specifically, the forces are negative damping (which uses the large-scale velocity field as a forcing function), a nonhelical random force, and a nonhelical static sinusoidal force (analogous to helical ABC forcing). The time evolution of the three ideal invariants (energy, magnetic helicity, and cross helicity), the time-averaged energy spectra, the energy ratios, and the dissipation ratios are examined. All three forcing functions produce qualitatively similar steady states with regard to the time evolution of the energy and magnetic helicity. However, differences in the cross-helicity evolution are observed, particularly in the case of the static sinusoidal method of energy injection. Indeed, an ensemble of sinusoidally forced simulations with identical parameters shows significant variations in the cross helicity over long time periods, casting some doubt on the validity of the principle of ergodicity in systems in which the injection of helicity cannot be controlled. Cross helicity can unexpectedly enter the system through the forcing function and must be carefully monitored.

Evaluation of the reliability and validity for X16 balance testing scale for the elderly.

PubMed

Ju, Jingjuan; Jiang, Yu; Zhou, Peng; Li, Lin; Ye, Xiaolei; Wu, Hongmei; Shen, Bin; Zhang, Jialei; He, Xiaoding; Niu, Chunjin; Xia, Qinghua

2018-05-10

Balance performance is considered as an indicator of functional status in the elderly, a large scale population screening and evaluation in the community context followed by proper interventions would be of great significance at public health level. However, there has been no suitable balance testing scale available for large scale studies in the unique community context of urban China. A balance scale named X16 balance testing scale was developed, which was composed of 3 domains and 16 items. A total of 1985 functionally independent and active community-dwelling elderly adults' balance abilities were tested using the X16 scale. The internal consistency, split-half reliability, content validity, construct validity, discriminant validity of X16 balance testing scale were evaluated. Factor analysis was performed to identify alternative factor structure. The Eigenvalues of factors 1, 2, and 3 were 8.53, 1.79, and 1.21, respectively, and their cumulative contribution to the total variance reached 72.0%. These 3 factors mainly represented domains static balance, postural stability, and dynamic balance. The Cronbach alpha coefficient for the scale was 0.933. The Spearman correlation coefficients between items and its corresponding domains were ranged from 0.538 to 0.964. The correlation coefficients between each item and its corresponding domain were higher than the coefficients between this item and other domains. With the increase of age, the scores of balance performance, domains static balance, postural stability, and dynamic balance in the elderly declined gradually (P < 0.001). With the increase of age, the proportion of the elderly with intact balance performance decreased gradually (P < 0.001). The reliability and validity of the X16 balance testing scale is both adequate and acceptable. Due to its simple and quick use features, it is practical to be used repeatedly and routinely especially in community setting and on large scale screening.

An open-source model and solution method to predict co-contraction in the finger.

PubMed

MacIntosh, Alexander R; Keir, Peter J

2017-10-01

A novel open-source biomechanical model of the index finger with an electromyography (EMG)-constrained static optimization solution method are developed with the goal of improving co-contraction estimates and providing means to assess tendon tension distribution through the finger. The Intrinsic model has four degrees of freedom and seven muscles (with a 14 component extensor mechanism). A novel plugin developed for the OpenSim modelling software applied the EMG-constrained static optimization solution method. Ten participants performed static pressing in three finger postures and five dynamic free motion tasks. Index finger 3D kinematics, force (5, 15, 30 N), and EMG (4 extrinsic muscles and first dorsal interosseous) were used in the analysis. The Intrinsic model predicted co-contraction increased by 29% during static pressing over the existing model. Further, tendon tension distribution patterns and forces, known to be essential to produce finger action, were determined by the model across all postures. The Intrinsic model and custom solution method improved co-contraction estimates to facilitate force propagation through the finger. These tools improve our interpretation of loads in the finger to develop better rehabilitation and workplace injury risk reduction strategies.

Parachute Aerodynamics From Video Data

NASA Technical Reports Server (NTRS)

Schoenenberger, Mark; Queen, Eric M.; Cruz, Juan R.

2005-01-01

A new data analysis technique for the identification of static and dynamic aerodynamic stability coefficients from wind tunnel test video data is presented. This new technique was applied to video data obtained during a parachute wind tunnel test program conducted in support of the Mars Exploration Rover Mission. Total angle-of-attack data obtained from video images were used to determine the static pitching moment curve of the parachute. During the original wind tunnel test program the static pitching moment curve had been determined by forcing the parachute to a specific total angle-of -attack and measuring the forces generated. It is shown with the new technique that this parachute, when free to rotate, trims at an angle-of-attack two degrees lower than was measured during the forced-angle tests. An attempt was also made to extract pitch damping information from the video data. Results suggest that the parachute is dynamically unstable at the static trim point and tends to become dynamically stable away from the trim point. These trends are in agreement with limit-cycle-like behavior observed in the video. However, the chaotic motion of the parachute produced results with large uncertainty bands.

A computational framework for simultaneous estimation of muscle and joint contact forces and body motion using optimization and surrogate modeling.

PubMed

Eskinazi, Ilan; Fregly, Benjamin J

2018-04-01

Concurrent estimation of muscle activations, joint contact forces, and joint kinematics by means of gradient-based optimization of musculoskeletal models is hindered by computationally expensive and non-smooth joint contact and muscle wrapping algorithms. We present a framework that simultaneously speeds up computation and removes sources of non-smoothness from muscle force optimizations using a combination of parallelization and surrogate modeling, with special emphasis on a novel method for modeling joint contact as a surrogate model of a static analysis. The approach allows one to efficiently introduce elastic joint contact models within static and dynamic optimizations of human motion. We demonstrate the approach by performing two optimizations, one static and one dynamic, using a pelvis-leg musculoskeletal model undergoing a gait cycle. We observed convergence on the order of seconds for a static optimization time frame and on the order of minutes for an entire dynamic optimization. The presented framework may facilitate model-based efforts to predict how planned surgical or rehabilitation interventions will affect post-treatment joint and muscle function. Copyright © 2018 IPEM. Published by Elsevier Ltd. All rights reserved.

STATIC BALANCE MEASUREMENTS IN STABLE AND UNSTABLE CONDITIONS DO NOT DISCRIMINATE GROUPS OF YOUNG ADULTS ASSESSED BY THE FUNCTIONAL MOVEMENT SCREEN™ (FMS™).

PubMed

Trindade, Matheus A; de Toledo, Aline Martins; Cardoso, Jefferson Rosa; Souza, Igor Eduardo; Dos Santos Mendes, Felipe Augusto; Santana, Luisiane A; Carregaro, Rodrigo Luiz

2017-11-01

The Functional Movement Screen™ (FMS™) has been the focus of recent research related to movement profiling and injury prediction. However, there is a paucity of studies examining the associations between physical performance tasks such as balance and the FMS™ screening system. The purpose of this study was to compare measures of static balance in stable and unstable conditions between different groups divided by FMS™ scores. A secondary purpose was to discern if balance indices discriminate the groups divided by FMS™ scores. Cross-sectional study. Fifty-seven physically active subjects (25 men and 32 women; mean age of 22.9 ± 3.1 yrs) participated. The outcome was unilateral stance balance indices, composed by: Anteroposterior Index; Medial-lateral Index, and Overall Balance Index in stable and unstable conditions, as provided by the Biodex balance platform. Subjects were dichotomized into two groups, according to a FMS™ cut-off score of 14: FMS1 (score > 14) and FMS2 (score ≤ 14). The independent Students t-test was used to verify differences in balance indices between FMS1 and FMS2 groups. A discriminant analysis was applied in order to identify which of the balance indices would adequately discriminate the FMS™ groups. Comparisons between FMS1 and FMS2 groups in the stable and unstable conditions demonstrated a higher unstable Anteroposterior index for FMS2 (p=0.017). No significant differences were found for other comparisons (p>0.05). The indices did not discriminate the FMS™ groups ( p  > 0.05). The balance indices adopted in this study were not useful as a parameter for identification and discrimination of healthy subjects assessed by the FMS™. 2c.

Impact force identification for composite helicopter blades using minimal sensing

NASA Astrophysics Data System (ADS)

Budde, Carson N.

In this research a method for online impact identification using minimal sensors is developed for rotor hubs with composite blades. Modal impact data and the corresponding responses are recorded at several locations to develop a frequency response function model for each composite blade on the rotor hub. The frequency response model for each blade is used to develop an impact identification algorithm which can be used to identify the location and magnitude of impacts. Impacts are applied in two experimental setups, including a four-blade spin test rig and a cantilevered full-sized composite blade. The impacts are estimated to have been applied at the correct location 92.3% of the time for static fiberglass blades, 97.4% of the time for static carbon fiber blades and 99.2% of the time for a full sized-static blade. The estimated location is assessed further and determined to have been estimated in the correct chord position 96.1% of the time for static fiberglass, 100% of the time for carbon fiber blades and 99.2% of the time for the full-sized blades. Projectile impacts are also applied statically and during rotation to the carbon fiber blades on the spin test rig at 57 and 83 RPM. The applied impacts can be located to the correct position 63.9%, 41.7% and 33.3% for the 0, 57 and 83 RPM speeds, respectively, while the correct chord location is estimated 100% of the time. The impact identification algorithm also estimates the force of an impact with an average percent difference of 4.64, 2.61 and 1.00 for static fiberglass, full sized, and carbon fiber blades, respectively. Using a load cell and work equations, the force of impact for a projectile fired from a dynamic firing setup is estimated at about 400 N. The average force measured for applied projectile impacts to the carbon fiber blades, rotating at 0, 57 and 83 RPM, is 368.8, 373.7 and 432.4 N, respectively.

Wii-habilitation as balance therapy for children with acquired brain injury.

PubMed

Tatla, Sandy K; Radomski, Anna; Cheung, Jessica; Maron, Melissa; Jarus, Tal

2014-02-01

To evaluate the effectiveness of the Nintendo Wii compared to traditional balance therapy in improving balance, motivation, and functional ability in children undergoing acute rehabilitation after brain injury. A non-concurrent, randomized multiple baseline single-subject research design was used with three participants. Data were analyzed by visual inspection of trend lines. Daily Wii balance training was equally motivating to traditional balance therapy for two participants and more motivating for one participant. While improvements in dynamic balance were observed, the results for static balance remain inconclusive. All participants demonstrated improvements in functional ability. Wii balance therapy is a safe, feasible, and motivating intervention for children undergoing acute rehabilitation after an acquired brain injury. Further research to examine the effectiveness of Wii balance therapy in this population is warranted.

Thermal Noise Reduction of Mechanical Oscillators by Actively Controlled External Dissipative Forces

NASA Technical Reports Server (NTRS)

Liang, Shoudan; Medich, David; Czajkowsky, Daniel M.; Sheng, Sitong; Yuan, Jian-Yang; Shao, Zhifeng

1999-01-01

We show that the thermal fluctuations of very soft mechanical oscillators, such as the cantilever in an atomic force microscope (AFM), can be reduced without changing the stiffness of the spring or having to lower the environment temperature. We derive a theoretical relationship between the thermal fluctuations of an oscillator and an actively external-dissipative force. This relationship is verified by experiments with an AFM cantilever where the external active force is coupled through a magnetic field. With simple instrumentation, we have reduced the thermal noise amplitude of the cantilever by a factor of 3.4, achieving an apparent temperature of 25 K with the environment at 295K. This active noise reduction approach can significantly improve the accuracy of static position or static force measurements in a number of practical applications.

Prediction of static friction coefficient in rough contacts based on the junction growth theory

NASA Astrophysics Data System (ADS)

Spinu, S.; Cerlinca, D.

2017-08-01

The classic approach to the slip-stick contact is based on the framework advanced by Mindlin, in which localized slip occurs on the contact area when the local shear traction exceeds the product between the local pressure and the static friction coefficient. This assumption may be too conservative in the case of high tractions arising at the asperities tips in the contact of rough surfaces, because the shear traction may be allowed to exceed the shear strength of the softer material. Consequently, the classic frictional contact model is modified in this paper so that gross sliding occurs when the junctions formed between all contacting asperities are independently sheared. In this framework, when the contact tractions, normal and shear, exceed the hardness of the softer material on the entire contact area, the material of the asperities yields and the junction growth process ends in all contact regions, leading to gross sliding inception. This friction mechanism is implemented in a previously proposed numerical model for the Cattaneo-Mindlin slip-stick contact problem, which is modified to accommodate the junction growth theory. The frictionless normal contact problem is solved first, then the tangential force is gradually increased, until gross sliding inception. The contact problems in the normal and in the tangential direction are successively solved, until one is stabilized in relation to the other. The maximum tangential force leading to a non-vanishing stick area is the static friction force that can be sustained by the rough contact. The static friction coefficient is eventually derived as the ratio between the latter friction force and the normal force.

Equipment and Protocols for Quasi-Static and Dynamic Tests of Very-High-Strength Concrete (VHSC) and High-Strength High-Ductility Concrete (HSHDC)

DTIC Science & Technology

2016-08-01

quasi -static mechanical properties, deformation behavior, and damage mechanisms in HSHDC and compare the behavior with VHSC. 2. Develop experimental ...using the experimental setup described in Chapter 6. The quasi -static strain rate was approximately 10-4/s. All panels tested have nominal dimensions...ER D C TR -1 6- 13 Force Protection Basing; TeCD 1a Equipment and Protocols for Quasi -Static and Dynamic Tests of Very-High-Strength

The effect of static force on round window stimulation with the direct acoustic cochlea stimulator.

PubMed

Maier, Hannes; Salcher, Rolf; Schwab, Burkard; Lenarz, Thomas

2013-07-01

The Direct Acoustic Cochlea Stimulator Partial Implant (DACS PI, Phonak Acoustic Implants SA, Switzerland) is intended to stimulate the cochlea by a conventional stapedotomy piston that is crimped onto the DACS PI artificial incus. An alternative approach to the round window (RW) is successfully done with other devices, having the advantage of being also independent of the existence of middle ear structure (e.g. ossicles). Here the possibility of stimulating the RW with the DACS actuator is investigated including the impact of static force on sound transmission to the cochlea. The maximum equivalent sound pressure output with RW stimulation was determined experimentally in fresh human temporal bones. Experiments were performed in analogy to the ASTM standard (F2504.24930-1) method for the output determination of implantable middle ear hearing devices (IMEHDs) in human cadaveric temporal bones (TBs). ASTM compliant temporal bones were stimulated with a prosthesis having a spherical tip (∅0.5 mm) attached to the actuator. The stimulation was performed perpendicular to the round window membrane (RWM) at varying position relative to the RW and the resulting static force on the RW membrane was determined. At each position the displacement output of the DACS PI actuator and the stapes footplate (SFP) vibration in response to actuator stimulation was measured with a Laser Doppler Velocimeter (LDV). By comparison of the achieved output at the stapes footplate in response to sound and transducer stimulation the equivalent sound pressure level at the tympanic membrane at 1Vrms input voltage was calculated assuming that the SFP displacement in both conditions is a measure of perceived loudness, as it is done in the ASTM standard. Ten TB preparations within the acceptance range of the ASTM standard were used for analysis. The actuator driven stapes footplate displacement amplitude as well as the resulting equivalent sound pressure level was highly dependent on the static force applied to the RW. The sound transfer efficiency from the RW to the stapes footplate increased monotonically with increasing static load. At a moderate static force load (approx. 3.9 mN) the obtained average sound equivalent sound pressure level was 102-120 eq. dB SPL @ nominally 1Vrms input for frequencies ≤4 kHz. At higher frequencies (6-10 kHz) the achieved output dropped to ∼90 dB SPL. This output was obtained at loading conditions compatible with the actuator safe operating range, although it was possible to increase the output further by increasing the static force load. Our results demonstrate for a first time that static force applied to the RW is crucial for sound transmission efficiency. Further we could show that RW stimulation with the DACS PI actuator is possible having a maximum output that is sufficient to treat moderate and pronounced sensorineural hearing losses (SNHL). This article is part of a Special Issue entitled "MEMRO 2012". Copyright © 2013 Elsevier B.V. All rights reserved.

Manipulation of nanoparticles of different shapes inside a scanning electron microscope

PubMed Central

Polyakov, Boris; Dorogin, Leonid M; Butikova, Jelena; Antsov, Mikk; Oras, Sven; Lõhmus, Rünno; Kink, Ilmar

2014-01-01

Summary In this work polyhedron-like gold and sphere-like silver nanoparticles (NPs) were manipulated on an oxidized Si substrate to study the dependence of the static friction and the contact area on the particle geometry. Measurements were performed inside a scanning electron microscope (SEM) that was equipped with a high-precision XYZ-nanomanipulator. To register the occurring forces a quartz tuning fork (QTF) with a glued sharp probe was used. Contact areas and static friction forces were calculated by using different models and compared with the experimentally measured force. The effect of NP morphology on the nanoscale friction is discussed. PMID:24605279

Static and dynamic stability of the guidance force in a side-suspended HTS maglev system

NASA Astrophysics Data System (ADS)

Zhou, Dajin; Cui, Chenyu; Zhao, Lifeng; Zhang, Yong; Wang, Xiqing; Zhao, Yong

2017-02-01

The static and dynamic stability of the guidance force in a side-suspended HTS-PMG (permanent magnetic guideway) system were studied theoretically and experimentally. It is found that there are two types of guidance force that exist in the HTS-PMG system, which are sensitive to the levitation gap and the arrangement of YBCO bulks around the central axis of the PMG. An optimized YBCO array was used to stabilize the system, which enabled a side-suspended HTS-PMG maglev vehicle to run stably at 102 km h-1 on a circular test track with 6.5 m in diameter.

Low-Speed Dynamic Wind Tunnel Test Analysis of a Generic 53 Degree Swept UCAV Configuration With Controls

NASA Technical Reports Server (NTRS)

Vicroy, Dan D.; Huber, Kerstin C.; Rohlf, Detlef; Loser, Thomas

2014-01-01

Several static and dynamic forced-motion wind tunnel tests have been conducted on a generic unmanned combat air vehicle (UCAV) configuration with a 53deg swept leading edge. These tests are part of an international research effort to assess and advance the state-of-art of computational fluid dynamics (CFD) methods to predict the static and dynamic stability and control characteristics for this type of configuration. This paper describes the dynamic forced motion data collected from two different models of this UCAV configuration as well as analysis of the control surface deflections on the dynamic forces and moments.

Effects of physical training on age-related balance and postural control.

PubMed

Lelard, T; Ahmaidi, S

2015-11-01

In this paper, we review the effects of physical activity on balance performance in the elderly. The increase in the incidence of falls with age reflects the disorders of balance-related to aging. We are particularly interested in age-related changes in the balance control system as reflected in different static and dynamic balance tests. We report the results of studies demonstrating the beneficial effects of physical activity on postural balance. By comparing groups of practitioners of different physical activities, it appears that these effects on postural control depend on the type of activity and the time of practice. Thus, we have focused in the present review on "proprioceptive" and "strength" activities. Training programs offering a combination of several activities have demonstrated beneficial effects on the incidence of falls, and we present and compare the effects of these two types of training activities. It emerges that there are differential effects of programs of activities: while all activities improve participants' confidence in their ability, the "proprioceptive" activities rather improve performance in static tasks, while "strength" activities tend to improve performance in dynamic tasks. These effects depend on the targeted population and will have a greater impact on the frailest subjects. The use of new technologies in the form of "exergames" may also be proposed in home-based exercises. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Effects of a randomized controlled recurrent fall prevention program on risk factors for falls in frail elderly living at home in rural communities.

PubMed

Jeon, Mi Yang; Jeong, HyeonCheol; Petrofsky, Jerrold; Lee, Haneul; Yim, JongEun

2014-11-14

Falling can lead to severe health issues in the elderly and importantly contributes to morbidity, death, immobility, hospitalization, and early entry to long-term care facilities. The aim of this study was to devise a recurrent fall prevention program for elderly women in rural areas. This study adopted an assessor-blinded, randomized, controlled trial methodology. Subjects were enrolled in a 12-week recurrent fall prevention program, which comprised strength training, balance training, and patient education. Muscle strength and endurance of the ankles and the lower extremities, static balance, dynamic balance, depression, compliance with preventive behavior related to falls, fear of falling, and fall self-efficacy at baseline and immediately after the program were assessed. Sixty-two subjects (mean age 69.2±4.3 years old) completed the program--31 subjects in the experimental group and 31 subjects in the control group. When the results of the program in the 2 groups were compared, significant differences were found in ankle heel rise test, lower extremity heel rise test, dynamic balance, depression, compliance with fall preventative behavior, fear of falling, and fall self-efficacy (p<0.05), but no significant difference was found in static balance. This study shows that the fall prevention program described effectively improves muscle strength and endurance, balance, and psychological aspects in elderly women with a fall history.

GMI Instrument Spin Balance Method, Optimization, Calibration, and Test

NASA Technical Reports Server (NTRS)

Ayari, Laoucet; Kubitschek, Michael; Ashton, Gunnar; Johnston, Steve; Debevec, Dave; Newell, David; Pellicciotti, Joseph

2014-01-01

The Global Microwave Imager (GMI) instrument must spin at a constant rate of 32 rpm continuously for the 3 year mission life. Therefore, GMI must be very precisely balanced about the spin axis and CG to maintain stable scan pointing and to minimize disturbances imparted to the spacecraft and attitude control on-orbit. The GMI instrument is part of the core Global Precipitation Measurement (GPM) spacecraft and is used to make calibrated radiometric measurements at multiple microwave frequencies and polarizations. The GPM mission is an international effort managed by the National Aeronautics and Space Administration (NASA) to improve climate, weather, and hydro-meteorological predictions through more accurate and frequent precipitation measurements. Ball Aerospace and Technologies Corporation (BATC) was selected by NASA Goddard Space Flight Center to design, build, and test the GMI instrument. The GMI design has to meet a challenging set of spin balance requirements and had to be brought into simultaneous static and dynamic spin balance after the entire instrument was already assembled and before environmental tests began. The focus of this contribution is on the analytical and test activities undertaken to meet the challenging spin balance requirements of the GMI instrument. The novel process of measuring the residual static and dynamic imbalances with a very high level of accuracy and precision is presented together with the prediction of the optimal balance masses and their locations.

GMI Instrument Spin Balance Method, Optimization, Calibration and Test

NASA Technical Reports Server (NTRS)

Ayari, Laoucet; Kubitschek, Michael; Ashton, Gunnar; Johnston, Steve; Debevec, Dave; Newell, David; Pellicciotti, Joseph

2014-01-01

The Global Microwave Imager (GMI) instrument must spin at a constant rate of 32 rpm continuously for the 3-year mission life. Therefore, GMI must be very precisely balanced about the spin axis and center of gravity (CG) to maintain stable scan pointing and to minimize disturbances imparted to the spacecraft and attitude control on-orbit. The GMI instrument is part of the core Global Precipitation Measurement (GPM) spacecraft and is used to make calibrated radiometric measurements at multiple microwave frequencies and polarizations. The GPM mission is an international effort managed by the National Aeronautics and Space Administration (NASA) to improve climate, weather, and hydro-meteorological predictions through more accurate and frequent precipitation measurements. Ball Aerospace and Technologies Corporation (BATC) was selected by NASA Goddard Space Flight Center to design, build, and test the GMI instrument. The GMI design has to meet a challenging set of spin balance requirements and had to be brought into simultaneous static and dynamic spin balance after the entire instrument was already assembled and before environmental tests began. The focus of this contribution is on the analytical and test activities undertaken to meet the challenging spin balance requirements of the GMI instrument. The novel process of measuring the residual static and dynamic imbalances with a very high level of accuracy and precision is presented together with the prediction of the optimal balance masses and their locations.

Evaluation of frictional resistance and surface characteristics after immersion of orthodontic brackets and wire in different chemical solutions: A comparative in vitrostudy.

PubMed

Nanjundan, Kavitha; Vimala, G

2016-01-01

To evaluate the changes of static and kinetic frictional forces between the brackets and wires following exposure to a soft drink, acidic food ingredient, and acidulated fluoride prophylactic agents. Two types of Roth prescription mandibular incisor brackets were used: 3M Unitek Victory stainless steel (SS) brackets (n = 40) and Transcend 6000 polycrystalline alumina (PCA) brackets (n = 40) as well as eighty 0.019 × 0.025" dimension ortho technology SS wires of 50 mm length each. Subsequently, brackets tied with SS wires divided into eight subgroups (n = 10) and were immersed in vinegar (pH = 3.5 ± 0.5), Pepsi ® (pH = 2.46), Colgate Phos-Flur mouth rinse (pH = 5.1), and artificial saliva (control group pH = 7) for 24 h. Changes in surface morphology under scanning electron microscope ×1000, surface roughness (Ra) with surface profilometer (single bracket and single wire from each subgroup), and frictional resistance using universal testing machine were evaluated. Highest mean (standard deviation) static frictional force of 2.65 (0.25) N was recorded in Pepsi ® followed by 2.57 (0.25) N, 2.40 (0.22) N, and 2.36 (0.17) N for Vinegar, Colgate Phos-Flur mouth rinse, and artificial saliva groups, respectively. In a similar order, lesser mean kinetic frictional forces obtained. PCA brackets revealed more surface deterioration and higher frictional force values than SS brackets. A significant positive correlation was observed between frictional forces and bracket slot roughness (r = 0.861 and 0.802, respectively, for static and kinetic frictional forces, p < 0.001 for both) and wire roughness (r = 0.243 and 0.242, respectively, for static and kinetic frictional forces, p < 0.05 for both). Findings may have long-term implications when acidic food substances are used during fixed orthodontic treatment. Further, in vivo studies are required to analyze the clinical effect of acidic mediums in the oral environment during orthodontic treatment.

A new paradigm for predicting zonal-mean climate and climate change

NASA Astrophysics Data System (ADS)

Armour, K.; Roe, G.; Donohoe, A.; Siler, N.; Markle, B. R.; Liu, X.; Feldl, N.; Battisti, D. S.; Frierson, D. M.

2016-12-01

How will the pole-to-equator temperature gradient, or large-scale patterns of precipitation, change under global warming? Answering such questions typically involves numerical simulations with comprehensive general circulation models (GCMs) that represent the complexities of climate forcing, radiative feedbacks, and atmosphere and ocean dynamics. Yet, our understanding of these predictions hinges on our ability to explain them through the lens of simple models and physical theories. Here we present evidence that zonal-mean climate, and its changes, can be understood in terms of a moist energy balance model that represents atmospheric heat transport as a simple diffusion of latent and sensible heat (as a down-gradient transport of moist static energy, with a diffusivity coefficient that is nearly constant with latitude). We show that the theoretical underpinnings of this model derive from the principle of maximum entropy production; that its predictions are empirically supported by atmospheric reanalyses; and that it successfully predicts the behavior of a hierarchy of climate models - from a gray radiation aquaplanet moist GCM, to comprehensive GCMs participating in CMIP5. As an example of the power of this paradigm, we show that, given only patterns of local radiative feedbacks and climate forcing, the moist energy balance model accurately predicts the evolution of zonal-mean temperature and atmospheric heat transport as simulated by the CMIP5 ensemble. These results suggest that, despite all of its dynamical complexity, the atmosphere essentially responds to energy imbalances by simply diffusing latent and sensible heat down-gradient; this principle appears to explain zonal-mean climate and its changes under global warming.

All about Motion & Balance. Physical Science for Children[TM]. Schlessinger Science Library. [Videotape].

ERIC Educational Resources Information Center

2000

Walking on a balance beam or riding a bike both require motion and balance. This program will reveal how unbalanced forces create motion, while balanced forces keep things still. Students also learn how concepts like velocity, acceleration, and momentum fit into this puzzle. A unique hands-on activity combined with vivid imagery and graphics…

Effects of Wearable Sensor-Based Balance and Gait Training on Balance, Gait, and Functional Performance in Healthy and Patient Populations: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

PubMed

Gordt, Katharina; Gerhardy, Thomas; Najafi, Bijan; Schwenk, Michael

2018-01-01

Wearable sensors (WS) can accurately measure body motion and provide interactive feedback for supporting motor learning. This review aims to summarize current evidence for the effectiveness of WS training for improving balance, gait and functional performance. A systematic literature search was performed in PubMed, Cochrane, Web of Science, and CINAHL. Randomized controlled trials (RCTs) using a WS exercise program were included. Study quality was examined by the PEDro scale. Meta-analyses were conducted to estimate the effects of WS balance training on the most frequently reported outcome parameters. Eight RCTs were included (Parkinson n = 2, stroke n = 1, Parkinson/stroke n = 1, peripheral neuropathy n = 2, frail older adults n = 1, healthy older adults n = 1). The sample size ranged from n = 20 to 40. Three types of training paradigms were used: (1) static steady-state balance training, (2) dynamic steady-state balance training, which includes gait training, and (3) proactive balance training. RCTs either used one type of training paradigm (type 2: n = 1, type 3: n = 3) or combined different types of training paradigms within their intervention (type 1 and 2: n = 2; all types: n = 2). The meta-analyses revealed significant overall effects of WS training on static steady-state balance outcomes including mediolateral (eyes open: Hedges' g = 0.82, CI: 0.43-1.21; eyes closed: g = 0.57, CI: 0.14-0.99) and anterior-posterior sway (eyes open: g = 0.55, CI: 0.01-1.10; eyes closed: g = 0.44, CI: 0.02-0.86). No effects on habitual gait speed were found in the meta-analysis (g = -0.19, CI: -0.68 to 0.29). Two RCTs reported significant improvements for selected gait variables including single support time, and fast gait speed. One study identified effects on proactive balance (Alternate Step Test), but no effects were found for the Timed Up and Go test and the Berg Balance Scale. Two studies reported positive results on feasibility and usability. Only one study was performed in an unsupervised setting. This review provides evidence for a positive effect of WS training on static steady-state balance in studies with usual care controls and studies with conventional balance training controls. Specific gait parameters and proactive balance measures may also be improved by WS training, yet limited evidence is available. Heterogeneous training paradigms, small sample sizes, and short intervention durations limit the validity of our findings. Larger studies are required for estimating the true potential of WS technology. © 2017 S. Karger AG, Basel.

Gait and functionality of individuals with visual impairment who participate in sports.

PubMed

da Silva, Edson Soares; Fischer, Gabriela; da Rosa, Rodrigo Gomes; Schons, Pedro; Teixeira, Luísa Beatriz Trevisan; Hoogkamer, Wouter; Peyré-Tartaruga, Leonardo Alexandre

2018-05-01

Individuals with visual impairment (VI) have often been observed to walk slower than individuals with unimpaired vision. These observations might be confounded by typical low levels of physical activity and greater sedentary behavior in individuals with VI than the overall population. Here, we compared gait and balance measures between individuals with VI who participate in disability sports, and activity level matched sighted individuals. We assessed static balance, anthropometry, self-selected walking speed, locomotion rehabilitation index, and lower limb muscular endurance; and applied physical activity level and fear of falling questionnaires. Individuals with VI who participate in disability sports, self-selected a similar walking speed (1.29 ± 0.26 m/s) as active sighted individuals (1.39 ± 0.21 m/s). Locomotor rehabilitation index and muscular endurance of lower limbs were also similar between groups. Individuals with VI presented lower static balance (42.0 ± 17.0s) than the sighted control group (45.0 ± 0s) when the controls were tested with their eyes open. However, no difference was found when the controls were tested with their eyes closed (30.3 ± 17.0s). Furthermore, individuals with VI showed a greater fear of falling. In conclusion, individuals with VI who participate in disability sports, as goalball and football, walk with similar self-selected walking speeds as active sighted individuals, but have slightly worse static balance and fear of falling. Copyright © 2018 Elsevier B.V. All rights reserved.

Associations of leisure-time physical activity with balance and lower extremity strength: a validation of the neuromuscular part of the Physical Activity Pie.

PubMed

Lindström, Paula J; Suni, Jaana H; Nygård, Clas-Håkan

2009-07-01

The importance of neuromuscular-type exercise (NME) has been recognized in recent recommendations for public health. However, the knowledge on associations and dose response of different types of leisure-time physical activity (LTPA) with musculoskeletal fitness and health is incomplete. This study evaluated the validity of the NME recommendation for public health introduced by the Physical Activity Pie. Engagement in LTPA and health-related fitness were assessed in 2 consecutive studies with the same adult population age 30 to 69 years (n = 575). Cross-sectional associations between different LTPA types and motor and musculoskeletal fitness were examined by logistic-regression models. Engagement in NME was associated with good static and dynamic balance and lower extremity strength. The highest odds ratios (OR) were found between brisk NME and static balance (most vs least fit OR = 2.39, moderate vs least fit OR = 1.94) and brisk NME and leg strength (more vs least fit OR = 2.10). Some associations were also found between brisk aerobic exercise and good balance. This cross-sectional study suggests that the recommendation for NME in the Physical Activity Pie is valid in terms of balance and leg strength, the 2 major fitness factors related to mobility functioning, especially among aging adults.

An investigation in MSFC 14-inch TWT to determine the static stability characteristics of 0.004-scale model (74-OTS) space shuttle vehicle 5 configuration (IA33), volume 1

NASA Technical Reports Server (NTRS)

Allen, E. C.

1975-01-01

Wind tunnel tests were conducted to: (1) determine the static stability characteristics of the Shuttle Vehicle 5 configuration; (2) determine the effect on the Vehicle 5 aerodynamic characteristics of External Tank (ET) and Solid Rocket Booster (SRB) nose shape, SRB nozzle shroud flare angle, orbiter to tank fairing, and sting location; (3) provide flow visualization using thin film oil paint; and (4) determine rudder, body flap, and inboard and outboard elevon hinge moments. The mated vehicle model was mounted in three different ways: (1) the orbiter mounted on the balance with the SRB's attached to the tank and the tank in turn attached to the orbiter; (2) the tank mounted on the balance (with the sting protruding through the tank base) with the SRB's and orbiter attached to the tank, and (3) with the tank mounted on the balance and the balance in turn supported by a forked sting entering the nozzle of each SRB, extending forward into the SRB's then crossing over to the tank to provide a balance socket. Data were obtained for Mach numbers from 0.6 through 4.96 at angles-of-attack and -sideslip from -10 to 10 degrees.

Influence of Pilates Mat and Apparatus Exercises on Pain and Balance of Businesswomen with Chronic Low Back Pain

PubMed Central

Lee, Chae-Woo; Hyun, Ju; Kim, Seong Gil

2014-01-01

[Purpose] The purpose of this study was to examine the influence of mat Pilates and apparatus Pilates on pain and static balance of businesswomen with chronic back pain. [Subjects and Methods] Participants were randomly allocated to Pilates mat exercises (PME) or Pilates apparatus exercise (PAE), and performed the appropriate Pilates exercises 3 days per week for 8 weeks. In order to measure the improvement in the participants’ static balance ability as a result of the exercise, the sway length and sway velocity of the subjects were measured before and after the experiment while the subjects stood on a Balance Performance Monitor (BPM) facing the front wall for 30 seconds with their eyes open. The visual analogue scale (VAS) was used to measure the degree of pain. [Results] The VAS score, sway length, and sway velocity of both groups decreased significantly after the experiment, but the PME group showed a greater decrease than the PAE group. [Conclusion] PME showed greater improvement in pain level and balance compared with PAE in this research. Since the subjects of this study were patients with low back pain, PME is assumed to have been more suitable and effective because it uses body weight to strengthen core muscles rather than heavier apparatuses as in PAE. PMID:24764614

Influence of pilates mat and apparatus exercises on pain and balance of businesswomen with chronic low back pain.

PubMed

Lee, Chae-Woo; Hyun, Ju; Kim, Seong Gil

2014-04-01

[Purpose] The purpose of this study was to examine the influence of mat Pilates and apparatus Pilates on pain and static balance of businesswomen with chronic back pain. [Subjects and Methods] Participants were randomly allocated to Pilates mat exercises (PME) or Pilates apparatus exercise (PAE), and performed the appropriate Pilates exercises 3 days per week for 8 weeks. In order to measure the improvement in the participants' static balance ability as a result of the exercise, the sway length and sway velocity of the subjects were measured before and after the experiment while the subjects stood on a Balance Performance Monitor (BPM) facing the front wall for 30 seconds with their eyes open. The visual analogue scale (VAS) was used to measure the degree of pain. [Results] The VAS score, sway length, and sway velocity of both groups decreased significantly after the experiment, but the PME group showed a greater decrease than the PAE group. [Conclusion] PME showed greater improvement in pain level and balance compared with PAE in this research. Since the subjects of this study were patients with low back pain, PME is assumed to have been more suitable and effective because it uses body weight to strengthen core muscles rather than heavier apparatuses as in PAE.

Effects of Vestibular Rehabilitation on Balance Control in Older People with Chronic Dizziness: A Randomized Clinical Trial.

PubMed

Ricci, Natalia Aquaroni; Aratani, Mayra Cristina; Caovilla, Heloísa Helena; Ganança, Fernando Freitas

2016-04-01

The aim of this study was to compare the effects of vestibular rehabilitation protocols on balance control in elderly with dizziness. This is a randomized clinical trial with 3-mo follow-up period. The sample was composed of 82 older individuals with chronic dizziness from vestibular disorders. The control group was treated according to the Conventional Cawthorne & Cooksey protocol (n = 40), and the experimental group was submitted to a Multimodal Cawthorne & Cooksey protocol (n = 42). Measures included Dynamic Gait Index, fall history, hand grip strength, Time Up-and-Go Test, sit-to-stand test, multidirectional reach, and static balance tests. With the exception of history of falls, Forward Functional Reach, Unipedal Right and Left Leg Eyes Closed, and Sensorial Romberg Eyes Open, all outcomes improved after treatments. Such results persisted at follow-up period, with the exception of the Tandem Eyes Open and the Timed Up-and-Go manual. The between-group differences for Sensorial Romberg Eyes Closed (4.27 secs) and Unipedal Left Leg Eyes Open (4.08 secs) were significant after treatment, favoring the Multimodal protocol. Both protocols resulted in improvement on elderly's balance control, which was maintained during a short-term period. The multimodal protocol presented better performance on specific static balance tests.

Control of Precision Grip Force in Lifting and Holding of Low-Mass Objects

PubMed Central

Kimura, Daisuke; Kadota, Koji; Ito, Taro

2015-01-01

Few studies have investigated the control of grip force when manipulating an object with an extremely small mass using a precision grip, although some related information has been provided by studies conducted in an unusual microgravity environment. Grip-load force coordination was examined while healthy adults (N = 17) held a moveable instrumented apparatus with its mass changed between 6 g and 200 g in 14 steps, with its grip surface set as either sandpaper or rayon. Additional measurements of grip-force-dependent finger-surface contact area and finger skin indentation, as well as a test of weight discrimination, were also performed. For each surface condition, the static grip force was modulated in parallel with load force while holding the object of a mass above 30 g. For objects with mass smaller than 30 g, on the other hand, the parallel relationship was changed, resulting in a progressive increase in grip-to-load force (GF/LF) ratio. The rayon had a higher GF/LF force ratio across all mass levels. The proportion of safety margin in the static grip force and normalized moment-to-moment variability of the static grip force were also elevated towards the lower end of the object mass for both surfaces. These findings indicate that the strategy of grip force control for holding objects with an extremely small mass differs from that with a mass above 30 g. The data for the contact area, skin indentation, and weight discrimination suggest that a decreased level of cutaneous feedback signals from the finger pads could have played some role in a cost function in efficient grip force control with low-mass objects. The elevated grip force variability associated with signal-dependent and internal noises, and anticipated inertial force on the held object due to acceleration of the arm and hand, could also have contributed to the cost function. PMID:26376484

Plate-shaped non-contact ultrasonic transporter using flexural vibration.

PubMed

Ishii, Takahiko; Mizuno, Yosuke; Koyama, Daisuke; Nakamura, Kentaro; Harada, Kana; Uchida, Yukiyoshi

2014-02-01

We developed a plate-shaped non-contact transporter based on ultrasonic vibration, exploiting a phenomenon that a plate can be statically levitated at the place where its gravity and the acoustic radiation force are balanced. In the experiment, four piezoelectric zirconate titanate elements were attached to aluminum plates, on which lattice flexural vibration was excited at 22.3 kHz. The vibrating plates were connected to a loading plate via flexible posts that can minimize the influence of the flexure induced by heavy loads. The distribution of the vibration displacement on the plate was predicted through finite-element analysis to find the appropriate positions of the posts. The maximum levitation height of this transporter was 256 μm with no load. When two vibrating plates were connected to a loading plate, the maximum transportable load was 4.0 kgf. Copyright © 2013. Published by Elsevier B.V.

Effect of varying internal geometry on the static performance of rectangular thrust-reverser ports

NASA Technical Reports Server (NTRS)

Re, Richard J.; Mason, Mary L.

1987-01-01

An investigation has been conducted to evaluate the effects of several geometric parameters on the internal performance of rectangular thrust-reverser ports for nonaxisymmetric nozzles. Internal geometry was varied with a test apparatus which simulated a forward-flight nozzle with a single, fully deployed reverser port. The test apparatus was designed to simulate thrust reversal (conceptually) either in the convergent section of the nozzle or in the constant-area duct just upstream of the nozzle. The main geometric parameters investigated were port angle, port corner radius, port location, and internal flow blocker angle. For all reverser port geometries, the port opening had an aspect ratio (throat width to throat height) of 6.1 and had a constant passage area from the geometric port throat to the exit. Reverser-port internal performance and thrust-vector angles computed from force-balance measurements are presented.

Effects of Static Stretching and Playing Soccer on Knee Laxity.

PubMed

Baumgart, Christian; Gokeler, Alli; Donath, Lars; Hoppe, Matthias W; Freiwald, Jürgen

2015-11-01

This study investigated exercise-induced effects of static stretching and playing soccer on anterior tibial translation (ATT) of the knee joint. Randomized controlled trial. University biomechanics laboratory. Thirty-one athletes were randomly assigned into a stretching (26.9 ± 6.2 years, 1.77 ± 0.09 m, 67.9 ± 10.7 kg) and a control group (27.9 ± 7.4 years, 1.75 ± 0.08 m, 72.0 ± 14.9 kg). Thirty-one amateur soccer players in an additional soccer group (25.1 ± 5.6 years, 1.74 ± 0.10 m, 71.8 ± 14.8 kg). All participants had no history of knee injury requiring surgery and any previous knee ligament or cartilage injury. The stretching group performed 4 different static stretching exercises with a duration of 2 × 20 seconds interspersed with breaks of 10 seconds. The soccer group completed a 90-minute soccer-specific training program. The control group did not perform any physical activity for approximately 30 minutes. Anterior tibial translation was measured with the KT-1000 knee arthrometer at forces of 67 N, 89 N, and maximal manual force (Max) before and after the intervention. There was a significant increase in ATT after static stretching and playing soccer at all applied forces. Maximal manual testing revealed a mean increase of ATT after static stretching of 2.1 ± 1.6 mm (P < 0.0005) and after playing soccer of 1.0 ± 1.5 mm (P = 0.001). The ATT increase after static stretching at 67 and 89 N is significantly higher than in controls. At maximum manual testing, significant differences were evident between all groups. Static stretching and playing soccer increase ATT and may consequently influence mechanical factors of the anterior cruciate ligament. The ATT increase after static stretching was greater than after playing soccer. The observed increase in ATT after static stretching and playing soccer may be associated with changes in kinesthetic perception and sensorimotor control, activation of muscles, joint stability, overall performance, and higher injury risk.

The force balance of sea ice in a numerical model of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Steele, Michael; Zhang, Jinlun; Rothrock, Drew; Stern, Harry

1997-09-01

The balance of forces in the sea ice model of Hibler [1979] is examined. The model predicts that internal stress gradients are an important force in much of the Arctic Ocean except in summer, when they are significant only off the northern coasts of Greenland and the Canadian Archipelago. A partition of the internal stress gradient between the pressure gradient and the viscous terms reveals that both are significant, although they operate on very different timescales. The acceleration term is generally negligible, while the sum of Coriolis plus sea surface tilt is small. Thus the seasonal average force balance in fall, winter, and spring is mostly between three terms of roughly equal magnitudes: air drag, water drag, and internal stress gradients. This is also true for the monthly average force balance. However, we find that there is a transition around the weekly timescale and that on a daily basis the force balance at a particular location and time is often between only two terms: either between air drag and water drag or between air drag and internal stress gradients. The model is in agreement with the observations of Thorndike and Colony [1982] in that the correlation between geostrophic wind forcing and the model's ice velocity field is high. This result is discussed in the context of the force balance; we show that the presence of significant internal stress gradients does not preclude high wind-ice correlation. A breakdown of the internal stress gradient into component parts reveals that the shear viscous force is far from negligible, which casts strong doubt on the theoretical validity of the cavitating fluid approximation (in which this component is neglected). Finally, the role of ice pressure is examined by varying the parameter P*. We find a strong sensitivity in terms of the force balance, as well as ice thickness and velocity.

Stability of the Einstein static universe in open cosmological models

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

Canonico, Rosangela; Parisi, Luca; INFN, Sezione di Napoli, GC di Salerno, Via Ponte Don Melillo, I-84081 Baronissi

2010-09-15

The stability properties of the Einstein static solution of general relativity are altered when corrective terms arising from modification of the underlying gravitational theory appear in the cosmological equations. In this paper the existence and stability of static solutions are considered in the framework of two recently proposed quantum gravity models. The previously known analysis of the Einstein static solutions in the semiclassical regime of loop quantum cosmology with modifications to the gravitational sector is extended to open cosmological models where a static neutrally stable solution is found. A similar analysis is also performed in the framework of Horava-Lifshitz gravitymore » under detailed balance and projectability conditions. In the case of open cosmological models the two solutions found can be either unstable or neutrally stable according to the admitted values of the parameters.« less

Maximal Voluntary Static Force Production Characteristics of Skeletal Muscle in Children 8-11 Years of Age.

ERIC Educational Resources Information Center

Going, Scott B.; And Others

1987-01-01

A study of maximal voluntary isometric muscle contraction force-time curves among 32 normal, healthy 8- to 11-year-olds performing tasks involving separate muscle groups found that force and maximal rate of force increase were quite reproducible, but time to selected force levels reflected considerable variations. (Author/CB)