Center Of Pressure Movement Research Articles

Effects of standing and walking on plantar pressure distribution in recreational runners before and after long-distance running

With marathon-running grew in popularity, the effect of long-distance running on plantar pressure has been more attractive. It has been proposed that long-distance running influences the deviation in the center of pressure (COP) during standing and the changes to plantar pressure during walking. The objective of this study was to observe the effects on the COP motion amplitude of static standing and the plantar pressure distribution of walking after long-distance running. The influence of a 10-km run on changes to plantar pressure was assessed during standing and walking. Plantar pressure was measured before and immediately after running. In the study, seven males and five females participated in barefoot tests of static standing and dynamic walking. In the static standing tests, COP was measured under the following four ordered conditions: (1) bipedal, eyes open, standing; (2) bipedal, eyes closed, standing; (3) unipedal, eyes open, standing and (4) unipedal, eyes closed, standing. Under each condition, the data was collected while a stable standing posture for 10 s. In the dynamic walking tests, the contact duration and plantar pressure were recorded. The standing tests results revealed no significant differences between males and females while slight differences before vs. after running. Running for a single time had no effect on COP deviation during standing. The walking tests results revealed an initial landing on the lateral heel. After landing on the lateral heel, the females quickly transferred to the medial heel. The movement of the pressure to the medial heel was slower in males than females. After running, the pressure of females was more inward, while that of males was more outward under the metatarsal zones in the propulsion phase.

The Relationship between Postural Control and Muscle Quality in Older Adults

This study aimed to determine relationships between muscle quality, the ratio of muscle strength to muscle mass, and postural control and compare postural control of older adults with higher and lower muscle quality. Twenty-five older adults had leg muscle quality and postural control with eyes open and closed measured. Linear and non-linear postural control variables were calculated from center of pressure movements. There was a significant canonical correlation between muscle quality and sway complexity, but no relationship between muscle quality and sway magnitude. Higher muscle quality older adults had greater medio-lateral sway complexity than lower muscle quality older adults. These findings suggest that higher muscle quality relates to greater sway complexity in older adults, suggesting maintenance of muscle quality should be considered important to attenuate postural control declines.

101. Quantitative Romberg using a force plate: An objective measure for cervical myelopathy

<h3>BACKGROUND CONTEXT</h3> Surgical decision-making for cervical spondylotic myelopathy (CSM) relies on evaluation of symptoms and physical examination. The Romberg test is a clinical exam used to identify balance issues with CSM. However, the Romberg test has a subjective interpretation and has a binary (positive or negative) result. While previous studies showed that force plate pressure readings provide quantitative measurements that objectively identify poor postural control in patients with CSM, the study compared an older CSM patient cohort with a significantly younger normal cohort, failing to account for regular aging changes. <h3>PURPOSE</h3> This study aims to compare force plate pressure readings during a standard Romberg test in patients with CSM to age-matched normal healthy volunteers. <h3>STUDY DESIGN/SETTING</h3> Longitudinal observational comparative cohort from a single multisurgeon spine center. <h3>PATIENT SAMPLE</h3> Patients who were clinically diagnosed with CSM (mean age 54.8 years, N=27) were compared to age-matched healthy volunteers (mean age 54.4 years, N=27) without a clinical history of cervical pathology. <h3>OUTCOME MEASURES</h3> Quantitative Romberg Force Plate Measurements. <h3>METHODS</h3> Patients with CSM requiring surgery and healthy normal volunteers were asked to perform the Romberg test while on a force plate measuring the center of pressure (COP): standing up straight with arms extended for 30 seconds with eyes open, followed by 30 seconds with eyes closed. The change for sway area, sway frequency and sway speed with eyes closed and eyes open were calculated and compared between patients with CSM and healthy volunteers. <h3>RESULTS</h3> Twenty-seven of 48 CSM patients were age-matched to 27 healthy volunteers. There was a larger change in Romberg measurements with eyes open vs eyes closed in CSM patients compared to normal volunteers for maximum lateral movement (12.1mm2 vs 4.1mm2, p<0.01), total lateral COP movement (97.2mm2 vs 32.6mm2 p<0.02), Total AP COP movement (165.8mm2 vs 78.1mm2, p<0.01), COP trace movement (211.5mm2 vs 87.8mm2, p<0.01), and total sway area (365.4mm2 vs 62.1mm2, p<0.01). Change in average speed with eyes open and eyes closed (7.0m/s vs 4.2m/s, p<0.09) and Anteroposterior movement (19.0 mm2 vs 10.8 mm2, p<0.07) were similar between the two groups. <h3>CONCLUSIONS</h3> Poor standing balance can be quantified in patients with CSM. Quantifying standing balance in patients with CSM shows significantly worse objective measures than age-matched healthy volunteers. The Romberg test on a force plate may help diagnose and evaluate patients with CSM, guide patient management, potentially grade the severity of spinal pathology, allow more timely surgical intervention, and improve surgical outcomes. Further studies are needed to determine its utility in monitoring disease progression and measure treatment effectiveness. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Influence of age on postural control during dual task: a centre of pressure motion and electromyographic analysis

BackgroundDual task influences postural control. A cognitive task seems to reduce muscle excitation during a postural balance, especially in older adults (OA).AimThe aim of this study is to evaluate the effect of three cognitive tasks on muscle excitation and static postural control in OA and young adults (YA) in an upright posture maintenance task.Methods31 YA and 30 OA were evaluated while performing a modified Romberg Test in five different conditions over a force plate: open eyes, closed eyes, spatial-memory brooks’ test, counting backwards aloud test and mental arithmetic task. The surface electromyographic signals of Tibialis anterior (TA), Lateral Gastrocnemius (GL), Peroneus Longus (PL), and Erector Spinae (ES) was acquired with an 8-channel surface electromyographic system. The following variables were computed for both the electromyographic analysis and the posturographic assessment: Root mean square (RMS), centre of pressure (CoP) excursion (Path) and velocity, sway area, RMS of the CoP Path and 50%, 95% of the power frequency. Mixed ANOVA was used to detect differences with group membership as factor between and type of task as within. The analysis was performed on the differences between each condition from OE.ResultsAn interaction effect was found for Log (logarithmic) Sway Area. A main effect for task emerged on all posturographic variables except Log 95% frequencies and for Log PL and ES RMS. A main effect for group was never detected.Discussion and conclusionThis study indicates a facilitating effect of mental secondary task on posturographic variables. Non-silent secondary task causes increase in ES and TA muscle activation and a worsening in static postural control performance.

Changes in Mediolateral Postural Control Mechanisms During Gait After Total Knee Arthroplasty

BackgroundPatients who have total knee arthroplasty (TKA) likely suffer from decreased postural stability because of postoperative changes in musculoskeletal structure and loss of proprioception. The purpose of this experimental biomechanical study was to determine if patients who have TKA improve their dynamic postural control during walking after TKA as compared with before TKA. The secondary purpose was to assess changes in postural control between post-TKA patients and healthy controls. MethodsTwenty-three patients who had primary knee osteoarthritis scheduled to undergo unilateral or bilateral TKA were prospectively enrolled. Each patient was tested at 3 months, 6 months, and 12 months after TKA. Ten healthy controls matched for age, sex, and body mass index were selected from a database of previous healthy volunteers without knee osteoarthritis. Ten Vicon cameras and four AMTI force platforms were used to collect the marker and center of pressure (COP) data while participants performed gait. ResultsInitial improvement in the double stance ratio was found by 6 months after TKA compared with before TKA. Patients showed improved postural control as evidenced by a faster mediolateral COP velocity and decreased double stance ratio at 12-month post-TKA compared with pre-TKA (P < .05). However, patients who underwent TKA exhibited limited ability to maintain consistent COP movement during walking with increased variability in COP parameters as compared with controls (P < .05). ConclusionPatients exhibited improvement in dynamic postural control after TKA with time, but had higher variability in COP parameters during gait than controls. It is possible that therapy aimed to improve proprioceptive balance after TKA may improve dynamic postural control.

Mechanisms of postural control in older adults based on surface electromyography data.

The present study aimed to clarify the mechanisms of postural control during standing in older adults and document the mechanisms of age-related motor control based on changes in muscle activities. A total of 26 healthy male adults (older adult group, ≥65-78years: n=16; younger adult group, 20-23years: n=10) participated in this study. Ground reaction force and kinematic data of the lower limbs (hip, knee, and ankle), and electromyographic data from 6 postural muscles on the right side were recorded and quantified for each motor phase during rapid voluntary center of pressure (COP) shift. Although hip strategy was more frequently observed in older adults than in young adults (56.3% vs. 20.0%), no muscle activity of hip agonists was observed in some (31.3%) older adults. Furthermore, older adults had a statistically significant delay in the inhibition of postural muscles during anticipatory postural adjustments (p<0.05). After the onset of COP motion, the co-contraction time between agonists and antagonists was significantly prolonged in the older adults than in the younger adults (p<0.05), and the reciprocal muscle pattern was unclear in the older adults. Prior to the termination of movement, agonist activity continued longer in the older adult group than in the younger adult group; that is, inhibition was insufficient in the older adult group. A series of postural strategies during the voluntary movement task were altered in older adults, and this was significantly related not only with the activation but also the inhibition of postural muscles.

Association between knee extensor and ankle plantarflexor muscle thickness and echo intensity with postural sway, mobility and physical function in older adults.

The purpose of this study was to assess the association between muscle thickness and echo intensity of the knee extensors and ankle plantarflexors with postural sway, mobility and physical function in older adults. Twenty-one older men and women (age; 69.9±4.3years) were assessed for postural sway (centre of pressure movement), mobility (i.e. Timed-Up and-Go-test [TUG]), physical function (i.e. 5 times sit-to-stand [STS]), and ultrasound derived measures of muscle thickness and echo intensity of the vastus lateralis (VL) and gastrocnemius medialis (GM). Significant inverse correlations were observed between VL and GM thickness with TUG (r=-0.432 to -0.492) and STS (r=-0.473 to -0.596). Significant positive correlations were observed between VL and GM echo intensity with TUG (r=0.459 to 0.518) and STS (r=0.481 to 0.635). Significant positive correlations were also detected between GM echo intensity and anteroposterior sway (r=0.451 to 0.534). Two key findings emerged from the present experiment. First, this study provides novel evidence that ankle plantarflexor echo intensity, but not thickness, was associated with anteroposterior postural sway among older adults. Second, we provide new evidence that muscle thickness and echo intensity of the knee extensors and uniquely, the ankle plantarflexors, presented with similar magnitude associations with TUG and STS performance in older adults.

Dynamic postural control correlates with activities of daily living and quality of life in patients with knee osteoarthritis

BackgroundKnee osteoarthritis (OA) negatively affects dynamic postural control, which is a basic function that individuals use to perform activities of daily living (ADL). The purpose of this study was to investigate the associations of center of pressure (COP) control during the transition from double-leg to single-leg standing with subjective assessments of ADL and quality of life (QOL) in patients with knee OA.MethodsThirty-six patients (29 females) with moderate-to-severe knee OA participated. Dynamic postural control was evaluated during the transition from double-leg to single-leg standing. Each patient stood on a force plate, lifted the less affected limb as fast as possible, and maintained single-leg standing with the more affected limb. The COP movements corresponding to anticipatory postural adjustment (APA) and transitional phases were assessed. The maximum displacement and peak velocity of the COP movements in the medial–lateral direction were calculated. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was used for the subjective assessment of ADL and QOL. Pearson’s product correlation analysis was performed to investigate the associations of COP movements in the APA and transitional phases with KOOS-ADL and KOOS-QOL.ResultsIn the APA phase, the maximum COP displacement was significantly correlated with KOOS-ADL (r = -0.353, P = 0.035) and KOOS-QOL (r = -0.379, P = 0.023). In the transitional phase, the maximum COP displacement and peak COP velocity were significantly correlated with KOOS-ADL (maximum displacement: r = 0.352, P = 0.035; peak velocity: r = 0.438, P = 0.008) and with KOOS-QOL (maximum displacement: r = 0.357, P = 0.032; peak velocity: r = 0.343, P = 0.040).ConclusionsThe present study showed that smaller COP movements in the APA phase and smaller and slower COP movements in the transitional phase correlated with poorer ADL and QOL conditions in patients with knee OA. These findings suggest that poor dynamic postural control is associated with poor ADL and QOL conditions in patients with moderate-to-severe medial knee OA. Conservative treatment for patients with knee OA may need to focus on dynamic postural control during the transition from double-leg to single-leg standing.

Cognitive processes and a centre-of-pressure error-based moving light-touch biofeedback

Lightly touching an earth-fixed external surface with the forefinger provides somatosensory information that reduces the center of pressure (CoP) oscillations. If this surface were to move slowly, the central nervous system (CNS) would misinterpret its movement as body self-motion, and involuntary compensatory sway responses would appear, resulting in a significant coupling between finger and CoP motions. We designed a forefinger moving light-touch biofeedback based on this finding, which controls the surface velocity to drive the CoP towards a target position.Here, we investigate this biofeedback resistance to cognitive processes. In addition to a baseline, the experimental protocol includes four main conditions. In the first, participants were utterly naive about the feedback. Then, they received additional reliable sensory information. The third condition ensured their full awareness of the external nature of the surface motion. Finally, the experimenter notified them that the external motion drives their balance and asked them to reject its influence.Our investigation shows that despite the robustness of the proposed biofeedback, light-touch remains penetrable by cognitive processes. For participants to dramatically reduce the existing coupling between the finger and CoP motions, they should be aware of the external motion, how it impacts sway, and actively reject its influence.The main implication of our findings is that light-touch exhibits the same cognitive flexibility as vision when artificially stimulated. This could be interpreted as a defense mechanism to re-weight these two sensory inputs in a moving environment.

Minimally important differences for subjective improvement in postural stability in patients with bilateral vestibulopathy

ObjectiveTo determine minimally important differences (MIDs) for subjective improvement in postural stability after a therapeutic intervention in patients with bilateral vestibulopathy (BVP). MethodsThirteen BVP patients received noisy galvanic vestibular stimulation (nGVS) for 30 min and their static posture with eyes closed was monitored after the stimuli. The velocity of the center of pressure (COP) movement, the area enclosed by the COP movement, and the root mean square (RMS) of the displacement of the COP were measured for 30 s. Subjective evaluation of postural stability after nGVS was graded as worsened, slightly worsened, unchanged, slightly improved and improved in comparison with postural stability measured without nGVS. Anchor-based methods were used to estimate MIDs for subjective improvement. Velocity, area and RMS for each anchor-response group were averaged (2 sessions, each with 5 measurement periods during 3 h after the stimuli). The mean changes between the slightly improved group and unchanged group were used as estimates for MID for improvement. ResultsA total of 129 anchors were analyzed. Subjective evaluations numbered 83 (64%) for unchanged and 33 (26%) for slightly improved. Anchor-based methods yielded estimates for MIDs of -0.43 cm/s in velocity improvement (p < 0.01), -0.77 cm2 for area improvement (p < 0.01) and -0.23 cm for RMS improvement (p < 0.001). ConclusionThe present study provides the estimation of MIDs for improving postural stability in BVP patients and may be useful for interpreting whether the results from clinical trials are meaningful in future studies.

Torque responses to in-place-perturbations in people with multiple sclerosis

BackgroundAutomatic postural responses are critical to prevent falls after a loss of balance. Although responses have been shown to be delayed in people with multiple sclerosis (PwMS), the degree to which other aspects of these movements are impacted by MS remains unknown. Research QuestionDo responses to in-place support-surface perturbations differ in PwMS compared to neurotypical adults? Are these responses related to a functional measure of postural response performance- center of mass (COM) displacement?. Method52 PwMS and 20 neurotypical, age-matched adults (NA) experienced backward support surface perturbations resulting in forward loss of balance and requiring an in-place response. Center of pressure (COP) and torque were calculated from force plates while center of mass (COM) approximations were collected via motion capture. Primary outcomes were maximal torque production at the foot and its timing, rate, and onset. ResultsPwMS and NA demonstrated no differences in maximal torque production (p = 0.79), timing of maximal torque (p = 0.29), rate of torque development (p = 0.76), or the onset of AP COP movement (p = 0.44). There was a significant negative association between the rate of torque development and forward COM displacement in both groups (Control: r=-0.64, p = 0.002; MS: r=-0.35, p = 0.01). Larger maximal torque production was also associated with smaller COM displacement in PwMS (r=-0.33, p = 0.02). ConclusionTorque profiles in response to backward support surface translations resulting in feet in-place responses were similar in people with mild MS and neurotypical adults. The rate of development and maximal torque were however correlated to functional postural response outcomes. These findings suggest that while not worse in PwMS during in-place perturbations, force-responses seem to be important predictors of the effectiveness of reactive postural control responses.

The effect of Estonian folk dance practice on static balance performance in young females

The aim of the present study was to establish the changes that occur in dancers’ static body balance indicators during rest, in case of interfering factors and in stress condition. The sample consisted of 14 advanced female folk dancers at the age of 16–20 years. The participants’ static body balance was measured at the beginning (in the autumn) and at the end (in the spring) of the eight-month dancing period. Static body balance indicators were registered on a dynamographic platform within 30 seconds, standing on bipedal on stable and unstable support surface in eyes-open (EO) and eyes-closed (EC) conditions. The Flamingo test balance control, the balance control after spinning around and jumping tests were conducted only in EO condition. The following parameters were registered: the movements of the centre of pressure (CoP) in the anterior-posterior (AP) and medio-lateral (ML) dimensions; the length, speed and area of the trajectory. According to the study, folk dancers’ CoP movements in the AP and ML dimensions, measured in different conditions (EO, EC), on stable and unstable support surface, did not change significantly after the eight-month dancing practice. The young folk dancers’ static body balance, assessed by CoP movement trajectory, speed and area, improved considerably over the eight-month training period. Flamingo test results indicate that practising folk dance develops the young female folk dancers’ right and left side static stability equally. In the context of Estonian folk dance practice, including preparation for performing at dance festival, the young female folk dancers’ balance performance improved both in vestibular instability (spins, standing on unstable support surface and in EO condition) and fatigue (jumping test) conditions.

The Effects of Stochastic Galvanic Vestibular Stimulation on Body Sway and Muscle Activity

Objective: This study aimed to investigate whether galvanic vestibular stimulation with stochastic noise (nGVS) modulates the body sway and muscle activity of the lower limbs, depending on visual and somatosensory information from the foot using rubber-foam.Methods: Seventeen healthy young adults participated in the study. Each subject maintained an upright standing position on a force plate with/without rubber-foam, with their eyes open/closed, to measure the position of their foot center of pressure. Thirty minutes after baseline measurements under four possible conditions (eyes open/closed with/without rubber-foam) performed without nGVS (intensity: 1 mA, duration: 40 s), the stimulation trials (sham-nGVS/real-nGVS) were conducted under the same conditions in random order, which were then repeated a week or more later. The total center of pressure (COP) path length movement (COP-TL) and COP movement velocity in the mediolateral (Vel-ML) and anteroposterior (Vel-AP) directions were recorded for 30 s during nGVS. Furthermore, electromyography activity of the right tibial anterior muscle and soleus muscle was recorded for the same time and analyzed.Results: Three-way analysis of variance and post-hoc multiple comparison revealed a significant increment in COP-related parameters by nGVS, and a significant increment in soleus muscle activity on rubber. There was no significant effect of eye condition on any parameter.Conclusions: During nGVS (1 mA), body sway and muscle activity in the lower limb may be increased depending not on the visual condition, but on the foot somatosensory condition.

TEMPORAL AND FRACTAL BEHAVIOR OF THE CENTER OF PRESSURE IN PARKINSONIAN AND HEALTHY ELDERLY COHORTS DURING QUIET STANDING

This study investigated the quantitative scaling properties of the center of pressure (COP) as well as the spatial-temporal properties of the COP to elucidate the postural control behavior of healthy elderly (HE) adults and adults with Parkinson’s disease (PD) during quiet standing. Eighteen adults with PD and eighteen HE adults participated in this study. The COP movements were recorded while participants stood on either a firm surface or on a foam pad with their eyes either opened or closed. The sway ranges in the anterior–posterior (AP) ([Formula: see text] and medio-lateral (ML) ([Formula: see text] directions, the total length of the trajectory ([Formula: see text], sway area ([Formula: see text], and scaling exponents ([Formula: see text] from detrended fluctuation analysis were computed from the measured COP data. All temporal variables of the COP in all conditions were found to be significantly larger in the PD group than in the HE group. Low scaling exponents obtained for the PD group showed this group possessed diminished postural control ability compared to the HE group. The PD group showed unpredictable open-loop control in both the AP and ML directions. This proprioceptive control became predictable and the time scale relations decreased as the postural challenges increased. The AP and ML closed-loop control of the PD group was more predictable than that of the HE group only when proprioception was distorted using intact visual input, and the visual and proprioceptive inputs were both intact.

Plantar pressures in three types of indigenous footwear, commercial minimal shoes, and conventional Western shoes, compared to barefoot walking

Humans evolved as barefoot walkers, and only started to use footwear recently in evolutionary history. It can be questioned what the effect is of footwear on gait. This effect has previously been studied for a range of conventional and athletic footwear, but this study focuses on indigenous footwear which does not have the features commonly associated with conventional footwear, such as a raised heel, a relatively narrow toe box, arch support, and a firm heel cup. We will assess whether such footwear can be considered functionally ‘minimal’ and simulate barefoot walking, by analysing spatial and temporal aspects of plantar pressure distribution. We first compare the 2 D spatial distribution of plantar pressure, using 2 D Statistical Parametric Mapping, between four populations walking barefoot and with indigenous or commercial minimal shoes. We compared Indians wearing sandal-like footwear (‘Kolhapuri’), Scandinavians wearing boot-type footwear (‘Nuvttohat’), Namibian San wearing sandal-like footwear (‘N!ang n|osi’) and Western Europeans wearing a commercial minimal shoe, and conventional Western footwear. Within each population, indigenous and commercial barefoot footwear data were compared to barefoot walking. No statistically significant differences were found within-population between all footwear conditions and barefoot walking. Second, we question whether there were 1 D temporal differences in centre of pressure movements between three footwear conditions (barefoot, commercial minimal, conventional Western) within one, Western, population. Using 1 D Statistical Parametric Mapping, differences between these three conditions are shown, with barefoot walking keeping a more proximal CoP position than both footwear conditions during most of push-off phase. Based on plantar pressure recordings, we conclude that all indigenous and commercial minimal shoes can functionally be considered ‘minimal footwear’, but with some differences to barefoot walking.

Evaluation of Postural Stability Differences in the Elderly Through Recurrent Analysis.

Measuring the center of pressure (CoP) for a subject positioned on a force plate is one of the most commonly used tools to investigate balance. Several studies have proven a significant degradation of the body's stability after the age of 60. The conclusions, however, are based on a limited number of indicators and without systematic nonlinear analysis methods being used to evaluate the progression of CoP parameter values. Neither the change in CoP movement in subjects over 60 years of age nor the considerations of their body mass index (BMI) has been systematically evaluated by nonlinear methods so far. This study is based on one of the frequent methods for nonlinear evaluation - the Recurrent Quantification analysis. This article discusses the applicability of this method with regards to the evaluation of changes in postural stability of subjects over 60 years of age. Postural stability changes were evaluated using CoP motion and tested by the nonlinear method. For this research purpose, a group of 103 elderly women were selected and divided into age-respective groups of 60-69 years and 70-79 years old. Each age group was further divided into a subgroup of normal and overweight subjects according to their BMI. The following recurrent analysis parameters were employed in the evaluation of CoP motion in medial-lateral and anterior-posterior directions: determinism (DET), laminarity (LAM) and trapping time (TT). The results of the Wilcoxon test revealed a statistically significant difference between the values in parameters for the different age groups of overweight subjects almost in all the cases. Conversely, statistically significant differences between age groups rarely occurred in a subgroup of subjects with a normal BMI.

Lower-limb coordination during gait: The effects of age and walking surface

Automatic postural responses are critical to prevent falls after a loss of balance. Although responses have been shown to be delayed in people with multiple sclerosis (PwMS), the degree to which other aspects of these movements are impacted by MS remains unknown.Do responses to in-place support-surface perturbations differ in PwMS compared to neurotypical adults? Are these responses related to a functional measure of postural response performance- center of mass (COM) displacement?.52 PwMS and 20 neurotypical, age-matched adults (NA) experienced backward support surface perturbations resulting in forward loss of balance and requiring an in-place response. Center of pressure (COP) and torque were calculated from force plates while center of mass (COM) approximations were collected via motion capture. Primary outcomes were maximal torque production at the foot and its timing, rate, and onset.PwMS and NA demonstrated no differences in maximal torque production (p = 0.79), timing of maximal torque (p = 0.29), rate of torque development (p = 0.76), or the onset of AP COP movement (p = 0.44). There was a significant negative association between the rate of torque development and forward COM displacement in both groups (Control: r=-0.64, p = 0.002; MS: r=-0.35, p = 0.01). Larger maximal torque production was also associated with smaller COM displacement in PwMS (r=-0.33, p = 0.02).Torque profiles in response to backward support surface translations resulting in feet in-place responses were similar in people with mild MS and neurotypical adults. The rate of development and maximal torque were however correlated to functional postural response outcomes. These findings suggest that while not worse in PwMS during in-place perturbations, force-responses seem to be important predictors of the effectiveness of reactive postural control responses.

Relationship between different methods to measure ankle range of motion in children with idiopathic toe walking

Automatic postural responses are critical to prevent falls after a loss of balance. Although responses have been shown to be delayed in people with multiple sclerosis (PwMS), the degree to which other aspects of these movements are impacted by MS remains unknown.Do responses to in-place support-surface perturbations differ in PwMS compared to neurotypical adults? Are these responses related to a functional measure of postural response performance- center of mass (COM) displacement?.52 PwMS and 20 neurotypical, age-matched adults (NA) experienced backward support surface perturbations resulting in forward loss of balance and requiring an in-place response. Center of pressure (COP) and torque were calculated from force plates while center of mass (COM) approximations were collected via motion capture. Primary outcomes were maximal torque production at the foot and its timing, rate, and onset.PwMS and NA demonstrated no differences in maximal torque production (p = 0.79), timing of maximal torque (p = 0.29), rate of torque development (p = 0.76), or the onset of AP COP movement (p = 0.44). There was a significant negative association between the rate of torque development and forward COM displacement in both groups (Control: r=-0.64, p = 0.002; MS: r=-0.35, p = 0.01). Larger maximal torque production was also associated with smaller COM displacement in PwMS (r=-0.33, p = 0.02).Torque profiles in response to backward support surface translations resulting in feet in-place responses were similar in people with mild MS and neurotypical adults. The rate of development and maximal torque were however correlated to functional postural response outcomes. These findings suggest that while not worse in PwMS during in-place perturbations, force-responses seem to be important predictors of the effectiveness of reactive postural control responses.

A Comparison of the Center of Pressure Trajectory Between Dynamic Response Prosthetic Feet Having Different Ankle Designs

ABSTRACT Introduction Commercially available dynamic response (DR) prosthetic feet have unique ankle designs, which provide different degrees of ankle motion. Differences in ankle motion between the prosthetic and anatomical foot creates an asymmetry in the locomotor system and affects its functions of shock absorption, progression, and stabilization. Ankle motion during gait can be assessed by quantifying the center of pressure (CoP) movement during the stance period of gait. Although previous studies have compared gait parameters between DR and non-DR feet, no studies have examined difference in CoP trajectories among common designs of DR feet. Methods LP-Variflex, Talux, and Variflex prosthetic feet were used as test feet to represent the common DR feet, that is, low-profile (LP), multi-axial (MX), and J-shaped (JS) ankle designs, respectively. Five subjects with unilateral transtibial amputation (TTA), six subjects with unilateral transfemoral amputation (TFA), and three healthy controls participated in the study. Subjects were prosthetic users for at least 18 months and were classified as K-level 3 or K-level 4 functional level. Each subject received standardized functional prosthetic gait training and accommodation with each test foot. For data collection, subjects walked on level ground using standardized shoes and CoP data were collected using in-sole sensors. The testing order of feet was randomized. The A-P and M-L location of CoP was determined at the following gait phases: initial contact (2% of gait cycle), early midstance (15% of gait cycle), terminal stance (35% of gait cycle), preswing (50% of gait cycle), and before toe-off (60% of gait cycle). The maximum A-P and M-L CoP excursion was also calculated. The A-P displacement of the CoP was normalized to the foot length, and the M-L displacement was normalized to the foot width. Analysis of variance was used to calculate differences in CoP between test feet, and a comparison-wise alpha of P &lt; 0.1 was considered as significant. Results In the TTA group, there was a significant difference between feet in A-P CoP location during early midstance (15% gait cycle). For the MX foot, the CoP was located at 21.3% ± 3.1% of the foot length, which was significantly greater than the LP and JS feet (15.6% ± 2% and 14.1% ± 3.4% foot length, respectively). During the period from terminal stance to toe-off (35%–60% gait cycle), the split keel design of JS and LP feet had greater M-L movement compared with that of the MX foot. In the TFA group, there were no differences in CoP trajectory between test feet. The maximum A-P excursion for all prosthetic feet was significantly greater than control subjects (80.4% ± 0.5% and 69.1% ± 2.7% foot length, respectively). The maximum M-L excursion for all prosthetic feet was significantly lesser than control subjects (14% ± 3.7% and 26.2% ± 3.7% foot width, respectively). Conclusions Differences in ankle design among different DR prosthetic feet can influence the asymmetry and functions of the locomotor system. In the TTA group, the MX foot resulted in a faster transition from initial contact to midstance, compared with the JS and LP feet. The split keel design of JS and LP feet closely mimicked the motion of the anatomical foot in late-stance period and provided controlled weight transfer from the prosthetic limb to the intact limb. In the TFA group, ankle design did not have a significant effect on CoP movement. All prosthetic feet had greater A-P CoP excursion and lower M-L excursion compared with the anatomical foot. Additional studies investigating the effects of DR foot/ankle designs on distinct functions of the locomotor system are needed to guide prosthetic foot prescription.

Functional Variability in Team-Handball Players during Balance Is Revealed by Non-Linear Measures and Is Related to Age and Expertise Level.

Postural control is considered a key variable in team sports, such as handball, which require abilities strongly related to balance. However, postural control and its relationship to the performance of handball skills according to the players’ skill level and age has not been evaluated to date. This study analyzes the relationship between balance ability and team-handball performance according to age and expertise, applying a non-linear approach to balance assessment. Postural control from 114 male team-handball players was analyzed through the center of pressure (COP) during a balance task. Sport performance was measured by the accuracy and speed in throwing. Expert players threw faster, but not more accurately than recreational players. Balance performance was better for 18+ players (older than 18 years old) than those U12 (under 12 years old), but no differences were found according to their skill level. Players who threw with less accuracy showed slower COP velocity during the balance task and their moves were less irregular. Players who threw faster displayed more irregular and less auto-correlated COP movements. In conclusion, experienced team-handball players exhibited better balance performance, and this seems to be related to the maturation of the motor system more than to sport performance level. Nevertheless, non-linear measures of COP excursion revealed an exploratory behavior during balance in expert players, exhibiting more motion adjustments to reduce motor output error. Traditional variables measuring balance performance did not show sensitivity to this motor control process. A non-linear approach to balance assessment revealed functional variability during balance as an intrinsic characteristic of individuals’ motor control according to age and skill level.