Center Of Pressure Variability Research Articles

The Influence of high kinesiophobia on dynamic postural stability among females with patellofemoral pain syndrome during a single-leg squat test

Objective. The purpose of this study was to examine the effect of Kinesiophobia level on postural stability during Single Leg Squat Test (SLST) in females with patellofemoral pain syndrome (PFPS). Methods. Forty women with PFPS were divided into a High Kinesiophobia level group (HK), a Low Kinesiophobia level group (LK), and a pain-free control group of twenty participants. Postural stability was measured during the performance of the Single Leg Squat Test (SLST) on a force platform. The centre of pressure (COP) excursion and velocity were recorded. Results. The HK group had a significantly higher mean medial–lateral and anterior-posterior COP displacement compared to the LK and control groups. However, the results showed no significant differences in COP variables (velocity and displacement) between LK and healthy subjects. Muscle strength of participants with PFPS presented a significant deficit compared to healthy control group. Conclusions. High Kinesiophobia negatively affects postural stability during the SLST. Kinesiophobia should be considered during the assessment and management of PFPS.

The effects of pressure on anticipatory postural adjustments during a jump shot in basketball

BackgroundAnticipatory postural adjustments (APAs) play an important role in feedforward control of dynamic movements, such as jump shot performance in basketball. It is known that jump shot performance declines under pressure from a defender (shot blocker). Research questionDoes pressure from a shot blocker affect the APAs of a jump shot in basketball? Is jump shot performance in basketball associated with APAs? MethodsFourteen healthy male university basketball players performed jump shots under pressure and non-pressure (free) conditions by a shot blocker. Using a force plate, the APAs were defined as occurring until the point of thrust (TH) phase, and ground reaction force (GRF) and center of pressure (COP) at that moment were assessed. To assess jump shot performance, the maximum GRF during the TH phase (THmax), jumping height, and success score of the shot (accuracy score: AS) were measured by using the vertical component of the force plate. Two-way ANOVA examined the effects of the phase and condition on APA duration. The effects of pressure from a shot blocker on each variable (subjective pressure intensity, AS, GRF, and COP) were analyzed using a pairwise t-test or Wilcoxon signed-rank tests. Relationships between changes in jump shot performance and GRF or COP variables were assessed via Spearman’s correlation analysis. Differences between the pressure and free conditions were denoted by p/f (pressure/free). ResultsThe APA duration was shorter under the pressure condition compared to the free condition. The THmax and jump height values were greater under the pressure condition relative to the free condition. Across conditions, changes in COP sway velocity of the APA phase were significantly and negatively correlated with AS. SignificanceThe results of this study suggest that pressure from a shot blocker shortens APA duration and decreases jump shot performance.

Comparison of Biomechanical, Clinical Indicators, and Quality of Life in People Undergoing Hip Replacement Surgery with Anterior and Posterior Approaches

Background: There are ongoing debates among surgeons regarding the most effective surgical method for hip replacement, with varying preferences for the anterior and posterior approaches. Both methods have demonstrated excellent long-term outcomes, with clinical differences primarily observed in the early postoperative period. Objectives: This study aimed to compare the anterior and posterior methods of hip replacement after six months of surgery in terms of biomechanical and clinical indicators, as well as quality of life. Methods: In this cross-sectional observational study, 42 patients who underwent hip replacement surgery using either the anterior (n = 22) or posterior method (n = 20) at least six months (and a maximum of 12 months) post-surgery, along with 20 healthy individuals, were evaluated. Biomechanical indices of the center of pressure (COP) were measured using a force plate during two-leg standing with eyes open and closed. Functional balance, independence, self-perception of performance, satisfaction, and quality of life were assessed using the timed up and go test (TUG), Barthel Index, Canadian Occupational Performance Measure (COPM), and the SF-36, respectively. Results: No significant differences were found between the anterior and posterior groups in terms of COP, clinical variables, and quality of life (P > 0.05). However, when compared to the control group, the anterior replacement group exhibited significantly higher COP displacement in the medial-lateral direction (P = 0.03) and COP velocity in the anterior-posterior direction (P = 0.02) during two-leg standing with eyes open. No significant differences in COP variables were observed in the posterior replacement group compared to the control group (P > 0.05). Conclusions: The findings indicate no significant differences between the anterior and posterior approaches to hip replacement in terms of biomechanical and clinical indicators, as well as quality of life after six months. Therefore, the choice of surgical method can be based on the patient's condition and the surgeon’s expertise in the respective approach.

Comparative Analysis of Dual-Task and Single- Task Balance Exercises in Improving Static Balance in Individuals with Anterior Cruciate Ligament Reconstruction

Introduction: Various balance exercises have been employed to enhance functional stability and balance in individuals who have undergone anterior cruciate ligament (ACL) reconstruction; however, no study has explored the use of dual-task balance exercises for these patients. This study compares the effects of dual motor task balance exercises and single-task exercises on the static balance indices of individuals with ACL reconstruction. Materials and Methods: In a single-blind randomized controlled trial, 27 subjects who had undergone ACL reconstruction were randomly divided into two groups: Dual-task and single- task balance exercises. Both groups performed their exercises three days a week for one month. Static balance indicators were assessed at the beginning and end of the treatment. Results: The results demonstrated that after the treatment, there was a statistically significant decrease in various center of pressure variables, including mean displacement in the anterior- posterior and medial-lateral directions, total path length, mean velocity of displacement, root mean square of displacement, and velocity. Furthermore, the knee injury and osteoarthritis outcome score significantly increased in both groups (P<0.05). However, when comparing the two groups, no significant difference was observed after the treatment (P>0.05). Conclusion: Dual-task and single-task motor exercises improve static stability and knee function levels in patients who have undergone ACL reconstruction. Meanwhile, the effectiveness of these exercise types does not significantly differ from each other.

Benefits of postural sway to succeed in goal-directed visual tasks

When individuals stand, they sway and so have to maintain their balance. It is generally expected that task performance is worse when standing and swaying than when sitting and therefore not swaying. In contrast, we hypothesized that greater sway is associated with better task performance in the absence of external perturbations of posture. Twenty-four healthy, young adults performed two goal-directed, modified Stroop tasks (incongruent and reversed incongruent) in four body position conditions (standing against a vertical surface, and standing freely with a wide, standard or narrow stance). Centre of pressure (COP) sway, head sway, eye movements, visual attention, and task performance were recorded. Partial correlation analyses showed significant positive associations between task performance and some COP and head sway variables, after controlling for the level of visual attention. Analyses of variance with three factors (body position, task difficulty, target distance) also showed significant interaction effects between body position (and therefore postural sway) and the number of accurate target findings. The presence of these interactions showed that narrow stance was both the best body position for performing the incongruent task and the worst body position for performing the reversed incongruent task. Overall, COP sway and head sway can increase task performance. Hence, healthy, young adults in quiet stance appear to use sway to explore their environment more effectively. However, it should be borne in mind that our hypothesis was formulated solely with regard to healthy, young adults standing in quiet stance.

The influence of balance support base manipulation on the kinematics of lower limbs during single-legged squats in people with patellofemoral pain

BackgroundGiven that people with patellofemoral pain (PFP) exhibit deficits in postural control, certain postural reactions may be associated with movement alterations in this population. Therefore, the objective of the present study was to investigate whether manipulation of the support base for balance maintenance could lead to different patterns of lower limb kinematics in people with PFP during single-legged squats. MethodsFourteen participants with PFP and 14 asymptomatic controls were first assessed performing single-legged squats freely, and then while holding a stick to provide stabilization during the task. Center of pressure (CoP) behavior and movements of the hip, knee, ankle in the sagittal, frontal, and transverse planes were evaluated. ResultsFor the participants with PFP, the use of support led to a reduction in the magnitude of CoP oscillation compared to free squatting, with effect sizes ranging from small to large, but no significant differences were found for the kinematic variables. No significant differences were observed for CoP or kinematic variables in the comparisons between squat conditions in asymptomatic controls. ConclusionIn summary, performing single-legged squats in a more stabilized condition did not influence lower limb movements in people with PFP.

Balance in obese and normal weight pregnant women: A longitudinal study

IntroductionPregnancy's physiological changes and weight gain can decrease balance control, increasing the risk of falls and impacting quality of life. The effect of obesity on balance control in pregnant women needs further investigation. ObjectiveInvestigate the effect of obesity during pregnancy on center of pressure (COP) control under sensory disturbances at different gestational age. MethodsThe COP (95% ellipse area, mean velocity and total length) of 23 pregnant women classified as normal weight (CG: n = 12) and obese (OG: n = 11) was evaluated at three gestational-age week times (T1 = 16th, T2 = 24th, T3 = 32nd week) on a force platform on standing position (SP) and under three disturbances: 1) visual disturbance (eyes closed), 2) proprioceptive disturbance (over an unstable surface) and, 3) vestibular disturbance (head movement). A mixed ANOVA (3 repeated measures vs. 2 groups) and LSD post-hoc was applied to examine main effects and interactions. Effect sizes were assessed using generalized eta squared (η2). ResultsAs main effect, in SP, COP area increased from T2 to T3 for both groups (P = 0.021, η2 = 0.193). One interaction was observed, under visual disturbance, the area increased from T2 to T3 only in the CG group (P = 0.020, η2 = 0.195). ConclusionThe progression of pregnancy negatively impacts postural stability throughout its course. Visual disturbance only affected the balance of the CG. Hence, obesity combined with pregnancy does not appear to alter COP variables.

Wobble Board Performance: A Practical and Useful Quantification in Balance Assessment

Balance is integral in ankle injury prevention and therapy, especially in high-risk sports like volleyball. For balance assessment, the recommended wobble board (WB) performance (i.e., time at equilibrium) has never been compared with the gold standard. The objective was to investigate the relationships of force-plate-derived center of pressure (CoP) with WB performance and the accuracy of WB-derived CoP estimates. Twelve high-level volleyball players completed six unipedal standing trials on a computerized WB. WB tilt angles and CoP were obtained simultaneously via tri-axis accelerometers on the WB (200 Hz) and a force plate (1000 Hz), respectively. WB performance, polynomial-transformed CoP estimates, and CoP fractal sway, sway area, and mean sway velocity were assessed via Pearson and concordance correlation, root mean square errors, and dependent t-tests. WB performance was related with CoP sway and sway area (|rlinear| = 0.714–0.842, |rnonlinear| = 0.833–0.910, p < 0.01). The strongest concordance (0.878–0.893, p < 0.001) and smallest errors (6.5–10.7%) were reported for anterior–posterior sway and sway area. Moderate to excellent relationships between the WB performance and force plate CoP variables supported the usefulness of WB performance and estimates (especially sway area) in balance assessment. Furthermore, this study presents recommendations for future analyses and modeling approaches to reflect the complexity of postural control.

Effects of infant care posture and weight on static postural balance.

Studies investigating postural balance during various infant care postures have not been reported yet. The aim of this study was to measure static postural balance when holding an infant dummy in-arms and carrying an infant dummy on back according to different infant dummy weights. Sixteen healthy young subjects participated in a balance test. Infant dummies with weights of 4.6 kg (1-month) and 9.8 kg (12-month) were used in this study. All subjects were asked to naturally stand on a force platform in two infant care postures (holding an infant in-arms and carrying an infant on one's back). Center of pressure (COP) was measured from the force platform. Quantitative variables were derived from the COP. Two-way repeated measure analysis of variance (ANOVA) was performed to determine main effects of infant care postures, infant weight, and their interactions on COP variables. Back carrying a 12-month infant dummy had the greatest amplitude in all COP variables. Back carrying posture showed significantly greater mean distance and peak power, faster mean velocity, and wider COP area compared to holding posture (P< 0.05). There were significant weight effects of most COP variables mainly in AP direction (P< 0.01). Our results could contribute to the prevention of musculoskeletal diseases or prevention of fall due to various infant care activities by developing an assisting device to improve postural balance.

Postural Control and Muscle Activity during Dual-Task in Young Adults.

In everyday life, we recurrently perform two tasks simultaneously, which is called dual-tasking. A common dual task is smartphone use while standing or walking. According to previous studies, this task can compromise postural stability. However, few studies have analyzed lower limb muscle activity during dual-tasking using smartphones. This study aimed to assess the postural sway and muscle activity during dual-tasking in young adults. Thirty-six healthy young adults (23.08 ± 3.92 years) participated in this study. They performed a single task (ST: keeping a quiet standing posture) and a dual task (DT: keeping the ST while simultaneously performing a cognitive task on their smartphone). Postural sway was assessed through the center of pressure (CoP) analysis using a force platform: total CoP displacement, CoP displacement in the anterior-posterior and medial-lateral directions, mean total velocity of the CoP, mean velocity of the CoP in the anterior-posterior and medial-lateral directions, and 95% confidence ellipse sway area. A surface electromyography system recorded the muscle activity of the lumbar spinal erector and five muscles of the lower limb (bilaterally). The results showed an increase in postural sway from the ST to the DT in all CoP variables (p < 0.05), and muscle activity in most muscles analyzed decreased from the ST to the DT (p < 0.05). In conclusion, our results reflect a decentralization of attention from motor performance once postural sway increased and muscle activity decreased in dual-task conditions.

362 Enhanced Measures to Quantify Gait and Balance Impairment in Degenerative Cervical Myelopathy: A Prospective Cohort Study

INTRODUCTION: Gait and balance impairment are among the cardinal symptoms of Degenerative Cervical Myelopathy, however, utilizing objective measurements of these functions is highly challenging. METHODS: A prospective cross-sectional cohort study with manual and quantitative gait/balance testing using a Protokinetics Zeno Walkway electronic pressure mat (self/fast-paced, tandem gait/stance, Romberg, one foot standing). RESULTS: 95 DCM and 78 healthy subjects were included. For quantitave gait assesment, Velocity (p = 4.56x 10-8, 3.39x10-7), Gait Variability Index (p = 1.788x10-8, p = 0.00169), and stability ratio, single stance time/ double stance time, (p = 4.167x10^-7, p = 1.438x10^-5) were significantly different between groups for both self and fast-paced gait assessments, respectively. Balance was assessed by the variability of the center of pressure (COP). The standard deviation variability of COP in both the X (p = 0.00171) and Y directions (p = 0.000104) and cadence (p = 0.00175) were significant for tandem gait, walking heel-to-toe. Standing on either the Left or Right foot also showed a difference in the variability of COP in both directions X (p = 4.21x10^-7 Left Foot, p = 8.27x10^-7 Right Foot) and Y (p = 6.64x10^-4 Left Foot, p = 1.32x10^-4 Right Foot). On, manual assesment, DCM patients scored significantly worse in all parameters such as self-paced (p = 5.54x10^-2), fast-paced (p = 6.28x10^-2), tandem gait (p = 3.60x10^-8), Romberg eyes open (p = 1.58x10^-2), Romberg eyes closed (p = 1.90x10^-2), L foot stance (p = 6.78x10^-6), R foot stance (2.1x10^-6), and tandem stance (p = 8.83x10^-5). CONCLUSIONS: Quantitative parameters from an electronic pressure mat can be used to assess gait and balance impairment with high sensitivity and strong correlation with subjective measures. Manual scoring of tandem gait, standing on one foot, and tandem stance also provided robust differences and can be easily adopted into routine assessment of DCM patients.

The Effects of Various Cognitive Tasks Including Working Memory, Visuospatial, and Executive Function on Postural Control in Patients With Anterior Cruciate Ligament Injury.

Anterior cruciate ligament (ACL) rupture can impair balance performance, particularly during cognitive motor dual-tasks. This study aimed to determine the effects of various modalities of cognitive load (working memory, and visuospatial and executive function) on postural control parameters in individuals with ACL injury. Twenty-seven ACL-injured and 27 healthy participants were evaluated doing different cognitive tasks (silent backward counting, Benton's judgment of line orientation, and Stroop color-word test) while standing on a rigid surface or a foam. Each task was repeated three times and then averaged. Center of pressure variables used to measure postural performance included sway area and sway velocity in anterior-posterior and medial-lateral directions. Cognitive performance was also assessed by calculating errors and the score of cognitive tasks. A mixed model analysis of variance for center of pressure parameters indicated that patients had more sways than the healthy group. The interaction of group by postural difficulty by cognitive tasks was statistically significant for cognitive errors (p < .01), and patients with ACL injury indicated more cognitive errors compared to healthy controls while standing on the foam. The main effect of cognitive task was statistically significant for all postural parameters, representing reduced postural sways in both groups with all cognitive tasks. However, ACL-injured patients showed more cognitive errors in difficult postural conditions, suggesting that individuals with ACL injury may prioritize postural control over cognitive task accuracy and adopt the posture-first strategy to maintain balance under dual-task conditions.

Assessment of Postural Control in Children with Movement Disorders by Means of a New Technological Tool: A Pilot Study.

Considering the variability and heterogeneity of motor impairment in children with Movement Disorders (MDs), the assessment of postural control becomes essential. For its assessment, only a few tools objectively quantify and recognize the difference among children with MDs. In this study, we use the Virtual Reality Rehabilitation System (VRRS) for assessing the postural control in children with MD. Furthermore, 16 children (mean age 10.68 ± 3.62 years, range 4.29-18.22 years) were tested with VRRS by using a stabilometric balance platform. Postural parameters, related to the movements of the Centre of Pressure (COP), were collected and analyzed. Three different MD groups were identified according to the prevalent MD: dystonia, chorea and chorea-dystonia. Statistical analyses tested the differences among MD groups in the VRRS-derived COP variables. The mean distance, root mean square, excursion, velocity and frequency values of the dystonia group showed significant differences (p < 0.05) between the chorea group and the chorea-dystonia group. Technology provides quantitative data to support clinical assessment: in this case, the VRRS detected differences among the MD patterns, identifying specific group features. This tool could be useful also for monitoring the longitudinal trajectories and detecting post-treatment changes.

Increasing Visual Biofeedback Scale Changes Postural Control Complexity.

Visual biofeedback (vFB) during quiet stance has been shown to improve postural control. While this improvement has been quantified by a reduction in the center of pressure (COP) sway, the effect on COP complexity remains unexplored. As such, 20 young adults (12 females; aged 23.63 ± 3.17 years) were asked to remain in a static upright posture under different visual biofeedback magnitude (no feedback [NoFB], magnified by 1 [vFB1], magnified by 5 [vBF5] and magnified by 10 [vBF10]). In addition to confirming, through traditional COP variables (i.e. standard deviation, mean velocity, sway area), that vFB scaling improved postural control, results also suggested changes in COP complexity. Specifically, sample entropy and wavelet analysis showed that increasing the vFB scale from 1:1 to 1:5 and 1:10 led to a more irregular COP and a shift toward higher frequency. Together, and particularly from a complexity standpoint, these findings provided additional understandings of how vFB and vFB scaling improved postural control.

Effects of arousal and valence on center of pressure and ankle muscle activity during quiet standing.

Emotion affects postural control during quiet standing. Emotional states can be defined as two-dimensional models comprising valence (pleasant/unpleasant) and arousal (aroused/calm). Most previous studies have investigated the effects of valence on postural control without considering arousal. In addition, studies have focused on the center of pressure (COP) trajectory to examine emotional effects on the quiet standing control; however, the relationship between neuromuscular mechanisms and the emotionally affected quiet standing control is largely unknown. This study aimed to investigate the effects of arousal and valence on the COP trajectory and ankle muscle activity during quiet standing. Twenty-two participants were instructed to stand on a force platform and look at affective pictures for 72 seconds. The tasks were repeated six times, according to the picture conditions composed of arousal (High and Low) and valence (Pleasant, Neutral, and Unpleasant). During the task, the COP, electromyogram (EMG) of the tibialis anterior and soleus muscles, and electrocardiogram (ECG) were recorded. The heart rate calculated from the ECG was significantly affected by valence; the value was lower in Unpleasant than that in Neutral and Pleasant. The 95% confidence ellipse area and standard deviation of COP in the anterior-posterior direction were lower, and the mean power frequency of COP in the anterior-posterior direction was higher in Unpleasant than in Pleasant. Although the mean velocity of the COP in the medio-lateral direction was significantly lower in Unpleasant than in Pleasant, the effect was observed only when arousal was low. Although the EMG variables were not significantly affected by emotional conditions, some EMG variables were significantly correlated with the COP variables that were affected by emotional conditions. Therefore, ankle muscle activity may be partially associated with postural changes triggered by emotional intervention. In conclusion, both valence and arousal affect the COP variables, and ankle muscle activity may be partially associated with these COP changes.

Investigating the Effect of Addition of Cervical Proprioceptive Training to Conventional Physiotherapy on Visual, Vestibular and Proprioceptive Dependency of Postural Control in Patients with Chronic Non-Specific Neck Pain: A Randomized Controlled Clinical Trial.

While cervical proprioception deficit has been suggested as a contributing factor to clinical consequences of chronic non-specific neck pain (CNSNP), the effect of addressing such impairments on postural control strategies has remained unexplored. The aim of this study was to compare the response of the postural control system to alteration of sensory afferents in CNSNP with asymptomatic individuals. Furthermore, we examined whether proprioceptive training would yield superior outcomes to routine physiotherapy for improvement of postural control, pain and disability. Center of pressure (CoP) variables of sixty CNSNP patients equally distributed in any of the proprioception-specific or conventional physiotherapy groups and 30 asymptomatic participants were evaluated under four standing conditions:1) normal, 2) foam, 3) cervical extension/eyes open and 4) cervical extension/eyes closed standing. CoP anteroposterior range and anteroposterior and mediolateral velocity in patients were significantly higher than the control group under condition 2 (P<0.05). Patients also demonstrated lower anteroposterior lyapunov exponent under conditions 2 and 4 (P<0.05). Both interventions significantly decreased anteroposterior range and anteroposterior velocity(P<0.05). Anteroposterior lyapunov exponent also increased under condition 2 (P<0.05).. After the interventions, CoP anteroposterior range and anteroposterior velocity were significantly lower in the proprioceptive exercise group than the conventional physiotherapy group (P<0.05). Anteroposterior lyapunov exponent was also significantly higher in the proprioceptive exercise group (P<0.05).This while there was no significant difference between these patients and control group participants in any of the CoP variables after intervention. Our results rejected the hypothesis that impaired neck proprioception in the presence of CNSNP is compensated by overweighting other sources of sensory afferent information. The findings also revealed that while proprioceptive exercises successfully returned postural strategies of CNSNP patients to those in asymptomatic participants, they do not add to clinical recovery of these patients.

Comparison of the Effects of Cognitive Dual-Task and Single-Task Balance Exercises on Static Balance among People with Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial.

The anterior cruciate ligament (ACL) reconstruction surgery improves mechanical stability; however, functional stability remains impaired. Balance exercises can help improve functional stability. The effect of cognitive dual-task balance exercises has not been studied in people with ACL reconstruction surgery; therefore, this study aimed to compare the effect of cognitive dual-task and single-task balance exercises on the static balance indices in these individuals. This study was a randomized clinical trial. After a period of conventional physiotherapy and applying inclusion criteria, 28 patients with ACL reconstruction surgery were randomly divided into two groups of cognitive dual-task and single-task balance exercises. Each group received the relevant exercises for four weeks, three times a week, with each session lasting 20 min. Center of pressure variables, including mean displacement in anterior-posterior and medial-lateral directions, total path length, mean velocity of displacement, root mean square of displacement and velocity, and the elliptical area, were measured using the FDM pressure platform before and after the interventions as the primary outcomes. Knee Injury and Osteoarthritis Outcome Score (KOOS) scale was completed by the participants before and after the interventions. The measured static balance variables and KOOS subscales had significant differences before and after intervention in both groups (P<0.05); however, no statistically significant difference was observed in these variables between the two groups. There was no significant correlation between KOOS subscales and measured static balance variables. Both cognitive dual-task and single-task balance exercises improved the indicators related to static balance and the level of functional disability of the knee. However, cognitive dual-task balance exercises had no superiority over single-task balance exercises in ACL-reconstructed individuals.

Plantar intrinsic foot muscle activity and its relationship with postural sway during tiptoe standing in ballet dancers and non-dancers

BackgroundMinimizing postural sway during tiptoe standing is essential for ballet dancers. Investigation of the activity of the plantar intrinsic foot muscles (PIFMs) may provide insight into postural sway in dancers. Herein, we compared PIFM activity during tiptoe standing between dancers and non-dancers and examined its relationship with postural sway. MethodsWe enrolled 14 female ballet dancers and 13 female non-dancers. Electromyography (EMG) amplitudes of 64 channels of PIFMs and center of pressure (COP) data were recorded during bipedal tiptoe standing tasks performed with ankle plantarflexion angles of 20°, 40°, and 60° (dancers only). The EMG amplitudes were normalized to those during the maximum voluntary contraction, and the muscle activity level and its coefficient of variation over time (EMG-CVtime) during the task were assessed. Standard deviations in the anteroposterior and mediolateral directions, velocity, and area were calculated from the COP data. ResultsMost COP and EMG variables were significantly lower in dancers than in non-dancers in both the 20° and 40° tasks (p < 0.05). Significant correlations were found between most combinations of the COP and EMG variables in both the 20° and 40° tasks in the whole cohort (r = 0.468–0.807, p ≤ 0.014). In the 60° task in dancers, COP velocity was strongly correlated with EMG-CVtime (r = 0.700, p = 0.005). ConclusionThese results provide novel evidence that the PIFMs do not require high activity, but rather that its low, steady activity is the key, to achieve less postural sway during bipedal tiptoe standing in dancers.

EMG Analysis During Static Balance in Chronic Ankle Instability, Coper and Controls.

Patients with chronic ankle instability (CAI) consistently display postural control alterations, which may result from sensorimotor dysfunction. This study aimed to compare muscle activity in the lower extremity and postural control among individuals with CAI, copers and uninjured controls during a static balance test. A total of 57 physically active participants were categorized into three groups (CAI, copers and controls) and performed a single-leg balance test with two visual conditions: eyes open and eyes closed. Muscle activity in six lower extremity muscles and center of pressure (CoP) variables were recorded and analyzed. Patients with CAI exhibited greater muscle activity in the medial gastrocnemius and gluteus maximus compared to controls or copers, regardless of the visual condition. Copers displayed increased gluteus medius activity compared to controls. Additionally, all groups demonstrated increased muscle activity and CoP variables when visual feedback was disrupted. These findings suggest that patients with CAI may have less effective recruitment of motor units during static balance. On the other hand, greater muscle activity in the gluteus medius in copers may represent a coping mechanism to avoid further ankle injuries. Further research on muscle activity during dynamic postural control is warranted to explore sensorimotor alterations in patients with CAI.

Sport dependent effects on the sensory control of balance during upright posture: a comparison between professional horseback riders, judokas and non-athletes.

Compared to judokas (JU) and non-athletes (NA), horseback riders (HR) may develop specific changes in their sensory control of balance. Thirty-four international-level JU, twenty-seven international-level HR and twenty-one NA participated. Participants stood upright on a plateform (static condition) or on a seesaw device with an instability along the mediolateral (ML) or the anteroposterior (AP) direction (dynamic conditions). These conditions were carried out with eyes opened (EO) or closed (EC), and with (wF) or without a foam (nF). Experimental variables included conventional (linear), non-linear center-of-pressure (COP) parameters, Romberg Quotient (RQ) and Plantar Quotient (PQ). Group effects. COP Surface (COPS) and standard deviation of COP along AP (SDY) were lower in HR than in JU in Static. SD Y was lower in HR than in JU in Dynamic AP. COP velocity (COPV) was lower in both HR and JU than in NA in Static and Dynamic. Sample entropy along AP and ML (SampEnY and SampEnX) were higher in HR than in JU in Static. SampEnY was higher in HR than in JU in Dynamic ML. Sensory effects. In EC, COPV was lower in JU than in NA in Dynamic AP, and lower in JU than in both HR and NA in Dynamic ML. In EO, COPV was lower in both JU and HR than in NA in Dynamic ML. RQ applied to COPS was lower in JU than in both HR and NA in Dynamic AP, and lower in JU than in HR in Dynamic ML. RQ applied to COPV was lower in JU than in both HR and NA in Static and Dynamic. PQ applied to COPS was higher in JU than in both HR and NA in Dynamic ML. Results showed that the effects of sport expertise on postural control could only be revealed with specific COP variables and were directionally oriented and sport-dependant. HR seem to rely more on vision than JU, thus revealing that the contribution of the sensory inputs to balance control is also sport-dependent. Results open up new knowledge on the specificity of sport practice on multisensory balance information during upright posture.