Center Of Pressure Parameters Research Articles

McConnell patellar taping on postural control of women with patellofemoral pain syndrome: randomized clinical trial

Abstract Introduction: The effects of McConnell patellar taping on the postural control of women with patellofemoral pain syndrome (PFPS) are controversial. Objective: To evaluate the effects of McConnell patellar taping on the static one-leg stance postural control and during squatting in women with PFPS. Method: A randomized, blinded clinical trial that comprised 40 women with PFPS, aged between 18 and 35 years. The study sample was allocated to two groups: McConnell patellar taping group (MPTG) and Placebo taping group (PTG). The analysis included the one-leg static support and squat on the lower limb with PFPS. The center of pressure (CoP) displacement parameters recorded by a force platform were analyzed using two-way ANOVA and Cohen’s d. Results: For the static postural control, no significant differences were found between the groups in terms of time or interaction (p>0.05); with small effect size. For the postural control during the one-leg squat, significant differences were found regarding the time of intervention for both groups, with reduced CoP parameters after the application of taping. However, the MPTG demonstrated a large effect size in frequency of oscillation and medium effect size in speed of oscillation, both during the squat exercise. Conclusion: McConnell patellar taping and placebo taping improved postural control during the one-leg squat. It should be observed that the changes and effect sizes determined for the MPTG were significantly higher compared to the PTG, emphasizing its clinical importance in the treatment of individuals with PFPS, during dynamic activities.

Postural stability of 5-year-old girls and boys with different body heights.

Postural stability is one of the determinants of proper body posture and a condition for developing motor abilities in every human being. The measurement of the centre of pressure (COP) location and displacement is the most common technique of postural stability assessment. The aim of this study was to assess differences in postural stability depending on sex of 5-year-old children with different body heights. A study included 435 healthy children (200 girls and 235 boys) born in 2010 whose parents gave a written consent to their participation in the project. Postural stability was assessed with the use of the dynamographic platform (Zebris FDM 1.8). The assessment of postural stability was based on COP shift parameters (sway path length of COP and average velocity of COP) and COP surface area parameters (area of the ellipse, length of ellipse in the anterior-posterior direction and length of the ellipse in the medial-lateral direction). Body height was measured with Holtein anthropometer and the obtained values were compared with percentile ranks determined by the WHO. The analysis of the parameters describing postural stability in the examined children revealed dimorphism. For the COP shift parameters and COP surface area parameters, the level of statistical significance was recorded for girls and boys. Girls achieved lower results of these parameters than boys regardless of their body height. In the groups of normal- and tall-statured children, differences between the genders were statistically significant. The present study characterised sex differences in postural stability of 5-year-old children. Sex-related differences were found during a natural stance for all COP parameters. Girls maintained a two-legged standing position with lower sway velocity and a smaller range of sway than their male counterparts. Normal- and tall-statured girls demonstrated better postural stability significantly more often than boys.

Balance Performance across the Lifespan Assessed by the Leonardo Mechanograph®: A Cross-Sectional Study.

Reference values of sway parameters have not been published for the Leonardo mechanograph® so far. The aim of this cross-sectional study was to determine normative values on postural control measured by the force plate Leonardo Mechanograph® and to analyze the influence of age and sex on balance performance. A set of standardized standing positions with eyes opened (Romberg, semi-tandem, tandem, unipedal standing) was carried out. Analysis of covariance (ANCOVA) was used to detect age-and sex-related differences in center of pressure (COP) parameters (path length, velocity, elliptical area, anterior-posterior, and medio-lateral directions). Measurements were available for 570 subjects aged 20–86 years. Statistical analysis showed a high effect of age group on postural control (partial n2 between 0.1 and 0.4) with a U-shaped dependency between postural control and age for all area- and path-related COP parameters, with the largest sway in the youngest (aged 20–40) and the oldest age group (aged 60–86). For velocity of COP, a linear deterioration with increasing age was found. Medio-lateral components of COP are likely to indicate the extent of postural control. Significant sex differences were not clearly supported by current findings. Age- and sex-related normative values are a useful resource for diagnostic, research, and training.

Correlational study of the center of pressure measures of postural steadiness on five different standing tasks in overweight adults.

This study applied the posturography framework on five static standing tasks from the Berg Balance Scale (BBS). Thirteen participants were recruited and the trajectory data of the center of pressure (CoP) were collected. To analyze the postural performance, two approaches were taken: the scores from the BBS and statistical analysis. For the statistical analysis, Spearman's method was applied to determine the correlation of CoP parameters. The results revealed the correlations between CoP parameters in the anterior-posterior (AP) and medial-lateral (ML) directions, and on the statokinesgram (SK) plane for all tasks. To obtain the in-depth detail between normal weight and overweight groups, the differences in the postural control mechanism were defined by correlations of CoP parameters. The Mann-Whitney U test was conducted to define the difference in postural control in terms of difference in weight gain and standing task factors, while Cohen's d was used to investigate the influence of the difference in standing tasks and weight gain on postural control. The results showed that the correlations of CoP parameters could distinguish the balance impairment in the overweight condition from the normal postural control. Otherwise, the scores of BBS, the Mann-Whitney U test and Cohen's d did not separate this slightly compensatory movement during equilibrium. Therefore, the correlations of CoP parameters could provide more information to analyze the balance function in each individual, especially in terms of slight compensation.

ONE-LEGGED STANCE BALANCE OF OLDER ADULTS WITH AND WITHOUT FALLS

Balance impairment is a common problem among older adults. Poor balance in older adults is often associated with mobility impairments, activity limitations and fear of falling in older adults. Thus, balance assessment is useful for early detection of postural control deficits to prevent mobility impairments and falls in older adults. The aim of this study was to assess if balance measures based in center of pressure (COP) parameters during one-legged stance could differentiate between older adults with and without falls in the past 12 months. One-hundred and seventy older adults (50 fallers and 120 non-fallers, age range: 63-72 years) performed three 30s one-legged stance trials with eyes open on a force platform with 30s of rest between each trial. The following variables were evaluated: COP 95% elliptical area, COP velocity in the anterior-posterior and medio-lateral directions, and test duration (how long the participant was able to stay in one-legged stance, up to 30s). Fallers had poorer balance than non-fallers (P ≤0.004). The COP parameters presented an area under the curve between 0.65-0.72, with sensitivity varying from 66 to 78% and specificity from 54 to 68%. There were no significant differences between fallers and non-fallers on test duration (17 vs. 18s, respectively). The findings showed that the fallers had similar duration time, but poorer balance than the non-fallers during one-legged stance. The COP parameters were able to differentiate the balance between fallers and non-fallers with acceptable area under curve, sensitivity and specificity.

Arm crank ergometer "spin" training improves seated balance and aerobic capacity in people with spinal cord injury.

There is some evidence that upper-body training modalities can improve not only aerobic capacity but also seated balance in people with spinal cord injury (SCI), even in those classified with motor-complete paralysis above T6. Here, we evaluated the effect of arm crank ergometry (ACE) "spin" training on trunk muscle recruitment and its effects on seated balance and aerobic capacity. Eight individuals with high-level complete and 6 with either a low-level complete or a motor-incomplete SCI participated in this study. Participants completed 5weeks of a group ACE "spin" training protocol which featured modulations in cadence and resistance as well as back-supported and unsupported bouts. Surface electromyography was used to confirm trunk muscle recruitment during unsupported ACE. Changes in aerobic capacity (peak oxygen consumption) and seated balance control (center of pressure parameters) were assessed at pre- and post-intervention. Unsupported ACE was effective for eliciting trunk muscle activity (P<.05). Following training, peak oxygen consumption significantly improved by an average of 16% (P=.005). Static sitting balance significantly improved from pre- to post-intervention, but only when tested with eyes closed as measured by a reduction in area (P=.047) and velocity of center of pressure (P=.013). No significant changes were observed in static sitting balance with eyes open or in dynamic sitting balance. Group ACE "spin" classes may benefit not only aerobic fitness but also static seated balance control in people with SCI.

Asymmetric dynamic center-of-pressure in Parkinson's disease

BackgroundGait disturbance gradually worsens as Parkinson's disease (PD) progresses, which significantly affects the quality of life of PD patients. Treadmill-based gait analysis systems can measure gait parameters including the dynamic center-of-pressure (COP) trajectory during ambulation. In this study, we hypothesized that altered dynamic COP changes are new gait characteristics for PD patients. MethodsDynamic COP parameters and classic spatiotemporal parameters were obtained for each patient using a treadmill-based system at the maximal comfortable treadmill speed (MCTS). We compared dynamic COP parameters between 44 PD patients and 31 controls, correlated these parameters with clinical and spatiotemporal data, and adjusted for age and MCTS to determine whether the parameters were independent from the treadmill speed. We also evaluated characteristics of COP parameters in relation to the more and less affected sides in PD patients. ResultsDuring treadmill walking the length of the COP trajectory in the stance phase was decreased, an effect that was more prominent on the more affected side in PD patients. COP parameters related to this change were significantly altered in patients when compared to controls. Asymmetry of the COP trajectories compared between both feet was identified as a significant gait characteristic after adjusting for age and MCTS. The overlaid graphical display of dynamic COP trajectory in PD patients showed “distorted butterfly with asymmetric wing” feature. ConclusionDynamic COP asymmetry provides a new and intuitive way to analyze gait abnormalities of PD patients. Further studies with prospective designs will substantiate the clinical usefulness of this feature of gait.

POSTURAL ADJUSTMENTS OF ACTIVE YOUTHS IN PERTURBATION AND DUAL-TASK CONDITIONS

ABSTRACT Introduction Cognitive components are necessary to maintain posture during external perturbations. However, few studies have investigated postural control when external perturbations are associated with a concomitant cognitive task (DT). Objectives To analyze the behavior of reactive adjustments after perturbation with different intensities and displacements in active young adults; and to analyze the influence of DT on predictive and reactive adjustments in different perturbation conditions. Methods Twenty-eight physically active young adults stood on an item of equipment that produced displacements of the base. Four experimental conditions were introduced in a single task (ST) and DT (cognitive-report how many times a pre-established number appeared in the audio): 1 (5 cm and 10 cm/s); 2 (5 cm and 25 cm/s); 3 (12 cm and 10 cm/s) and 4 (12 cm and 25 cm/s). Three attempts were carried out for each condition (total=24). Center of pressure (CoP) parameters were analyzed considering the following windows: predictive (-250 to +50 ms), reactive 1 (+50 to +200 ms) and reactive 2 (+200 to +700 ms), in comparison to the start of the CoP activity. One-way ANOVAs were performed to analyze predictive adjustments, while two-way ANOVAs with factor for task (STxDT) and condition (1x2x3x4), with repeated measurements, were performed for the reactive adjustments. Results One-way ANOVA (predictive) indicated that the subjects had higher CoP parameters in ST vs DT. In reactive adjustments 1 and 2, ANOVA indicated greater CoP parameters in condition 2 and 4 when compared to 1 and 3, and in the ST vs DT. The subjects took longer to recover stable position in conditions 1 and 3 than in conditions 2 and 4. Conclusion Perturbation intensity has a greater influence on postural adjustments to maintain balance than on magnitude. Moreover, the association of cognitive tasks with external perturbation decreases CoP oscillation. Therefore, cognitive resources play an important role in postural control after perturbation. Level of evidence III; Study of nonconsecutive patients, with no “gold” standard applied uniformly.

Center of pressure characteristics from quiet standing measures to predict the risk of falling in older adults: a protocol for a systematic review and meta-analysis

BackgroundFalling is the most common accident of daily living and the second most prevalent cause of accidental death in the world. The complex nature of risk factors associated with falling makes those at risk amongst the elderly population difficult to identify. Commonly used clinical tests have limitations when it comes to reliably detecting the risk of falling, but existing laboratory tests, such as force platform measurements, represent one method of overcoming this lack of a test. Despite their widespread use, however, Center of Pressure (COP) signal analysis techniques vary and there is currently no consensus on which features should be used diagnostically. Our objective is to identify, through a systematic review and meta-analysis, the COP characteristics of older adults (≥ 60 years old) during quiet bipedal stance which will allow fallers to be distinguished from non-fallers.MethodsThe systematic review will include both prospective and retrospective articles. Five databases will be searched: PubMed, Cochrane CENTRAL, EMBASE, and ScienceDirect. In addition, a search of gray literature will be performed using Google Scholar and ClinicalTrials.gov. Searches will be circumscribed to include only older adults (aged over 60 years) who underwent a bipedal quiet standing measure of their balance and for whom the number of falls was reported. Two authors will independently assess the risk of bias for each included article using a 26-item checklist. Funnel plots will be drawn to attest of possible publication biases for each COP parameters. The results will be synthesized descriptively and a meta-analysis will be undertaken. When trial methodological heterogeneity is too great for pooling of the data into a meta-analysis, evidence strength will be evaluated using best evidence analysis.DiscussionDespite the numerous advantages of posturography, the diversity of studies exploring balance in older fallers has led to uncertainty regarding the method’s ability to reliably identify fall-prone older adults. It is expected that the findings from this systematic review will help clinicians use bipedal quiet standing measures as a diagnostic test and allow researchers to explore COP characteristics to create better models for fall prevention care.Systematic review registrationPROSPERO CRD42018098671

Postural control in girls with adolescent idiopathic scoliosis while wearing a Chêneau brace or performing active self-correction: a pilot study.

BackgroundIt is known that adolescent idiopathic scoliosis (AIS) is often accompanied by balance deficits. This reciprocal relationship must be taken into account when prescribing new therapeutic modalities because these may differently affect postural control, interacting with therapy and influencing its results.ObjectiveThe purpose was to compare postural control in girls with AIS while wearing the Chêneau brace (BRA) or performing active self-correction (ASC) with their postural control in a quiet comfortable stance.MethodsNine subjects were evaluated on a force plate in three series of two 20-s quiet standing trials with eyes open or closed; three blocks were randomly arranged: normal quiet stance (QST), quiet stance with BRA, and quiet stance with ASC. On the basis of centre-of-pressure (COP) recordings, the spatial and temporal COP parameters were computed.Results and DiscussionPerforming ASC was associated with a significant backward excursion of the COP mean position with eyes open and closed (ES = 0.56 and 0.65, respectively; p < 0.05). This excursion was accompanied by an increase in the COP fractal dimension (ES = 1.05 and 0.98; p < 0.05) and frequency (ES = 0.78; p = 0.10 and ES = 1.14; p < 0.05) in the mediolateral (ML) plane. Finally, both therapeutic modalities decreased COP sample entropy with eyes closed in the anteroposterior (AP) plane. Wearing BRA resulted in ES = 1.45 (p < 0.05) while performing ASC in ES = 0.76 (p = 0.13).ConclusionThe observed changes in the fractal dimension (complexity) and frequency caused by ASC account for better adaptability of patients to environmental demands and for their adequate resources of available postural strategies in the ML plane. These changes in sway structure were accompanied by a significant (around 25 mm) backward excursion of the mean COP position. However, this improvement was achieved at the cost of lower automaticity, i.e. higher attentional involvement in postural control in the AP plane. Wearing BRA may have an undesirable effect on some aspects of body balance.

Do the type of walking surface and the horse speed during hippotherapy modify the dynamics of sitting postural control in children with cerebral palsy?

BackgroundHippotherapy is described as a rehabilitation method for postural control in children with cerebral palsy. Horse's movements can be manipulated during hippotherapy's sessions with horse walking on different surfaces and at different speeds. The purpose of this study was to assess if dynamic sitting postural control in children with cerebral palsy in hippotherapy is modified when surfaces (sand or asphalt) and horse's walking speed (slow or faster) are changed. MethodsSixteen children participated in this crossover study. Eight bilateral spastic cerebral palsy children, age range (6–12 years), with Gross Motor Function Classification System levels III to IV, practicing hippotherapy and eight children with typical development (reference group), matched for age and sex. All children were evaluated during riding a horse on sand and asphalt surfaces and at slow (self-selected) and faster (30%) horse's walking speed. Center of pressure parameters were determined by a portable pressure measurement system positioned on the saddle. FindingsMediolateral displacement amplitude of the center of pressure was larger when the horse was on sand. Mediolateral and anteroposterior displacements amplitude and velocities of the center of pressure increased at horse's faster walking speed. InterpretationOur study test empirical procedures used in clinical practice and with a population widely reached by hippotherapy. In order to increase the demand for sitting postural control in children with cerebral palsy during horse riding, faster horse speed or riding on sand should be used.

Effectiveness of vestibular rehabilitation in patients with vestibular dysfunction

Vertigo and instability due to vestibular dysfunction have been a frequent cause of work absence, with a clearly upward tendency observed in recent years. Uncompensated vestibular hypofunction requires vestibular rehabilitation, but access to this form of treatment remains limited. Therefore, innovative methods of rehabilitation utilizing new technologies, which could promote this therapy, are searched for. Virtual reality (VR) is becoming a popular method of rehabilitation used, for example, in the treatment of stroke or schizophrenia. The aim of this study was to compare and evaluate 2 methods of vestibular rehabilitation in patients with unilateral vestibular disorders. Forty-three patients with unilateral vestibular disorders diagnosed at the Balance Disorders Unit, 1st Otolaryngology Department of the Medical University of Lodz, were included in this study. The patients, divided into 2 groups, received 10 sessions of rehabilitation. Group 1 (N = 22) was rehabilitated using a VR unit consisting of a forceplate and a motion sensor, while Group 2 (N = 21) performed training on a static posturography platform under physiotherapist supervision. The patients were examined at the baseline, 1 month and 3 months after rehabilitation. During each assessment, posturography was performed which recorded the center of pressure (CoP) displacement. The patients also filled out a questionnaire to quantify vertigo symptoms. The CoP parameters decreased in both groups, with no superiority of either form of training. Analysis of the subjective symptoms reduction revealed a decrease in the Vertigo Syndrome Scale - short form (VSS-sf) score in the second evaluation in both groups, which was slightly greater in the VR group. The improvement remained stable 3 months after rehabilitation. Both forms of rehabilitation are effective in increasing postural stability and reducing subjective symptoms. Virtual reality training achieves a slightly greater subjective improvement. Med Pr. 2019;70(5):545-53.

How many balance task trials are needed to accurately assess postural control measures in older women?

SummaryTaking the average of different trials is recommended for better balance assessment, but few studies have really proven this point under different balance conditions. ObjectiveTo assess the effects of averaging trials of five different balance tasks on postural control measures in older women. MethodsA total of 90 older women (means: Age: 68 years; Weight: 67 kg; Height: 1.56 m; Body mass index, 27 kg/m2) participated in this study. The participants completed five balance tasks with three performance trials for each task on a force platform in random order. The participants completed a total of three 30-s trials of tasks with 30 s of rest between trials. Repeated measure ANOVA and coefficient of variation were computed to compare differences for one trial vs. averaging across two or three trials on center of pressure (COP) sway values. ResultsThere were no significant differences (P > 0.05) in COP sway values when comparing one vs. the average of two or three trials for all balance tasks. However, the coefficient of variation was higher for three trials (10–40%) than two (6–37%) or one trial (3–23%) for COP parameters. ConclusionsBased on reduction of variability, the present study recommends the averaging of a minimum of two trials for balance assessment in older women.The results of the current study have implications for balance assessment in older people in fall prevention programs.

Alterations in Center of Pressure During Single-Limb Loading in Individuals with Patellofemoral Pain.

Altered foot loading during weightbearing is suggested to play a role in the development of patellofemoral pain (PFP). This study aimed to determine foot-loading characteristics associated with PFP by assessing center of pressure (COP) during single-limb loading in individuals with PFP compared with noninjured controls. Thirty recreationally active patients with PFP and 30 noninjured control participants had barefoot plantar pressure assessed during single-limb squats (SLSs) from which COP parameters (COP velocity and COP index) were obtained. Groups were compared using independent t tests. Individuals with PFP demonstrated a greater COP index (P = .042), indicating a more lateral foot-loading pattern, and exhibited increased overall COP velocity (P = .013) and anteroposterior COP velocity during SLSs compared with control participants (P = .033). Greater lateral foot loading and increased COP velocity during SLSs demonstrated by individuals with PFP may indicate reduced dynamic balance in this patient group, which may be implicated in the development of PFP.

Utility of center of pressure measures during obstacle crossing in prediction of fall risk in people with Parkinson’s disease

IntroductionPostural instability during walking and tripping over obstacles are the main causes of falls in people with Parkinson’s disease (PD). Preliminary limited evidence suggests that the length of the prospective follow-up period affects falls prediction in PD, with shorter periods leading to more accurate prediction. Thus, the primary aim of the present study was to test the performance of center of pressure (CoP) variables during obstacle crossing to predict fall risk in people with PD during subsequent periods of four, six, and 12 months. We also compared CoP variables during obstacle crossing between fallers and non-fallers. MethodsForty-two individuals with PD, in mild to moderate stages, completed the baseline obstacle crossing assessment and reported falls for 12 months. Participants walked at their self-selected pace and were instructed to cross an obstacle (half knee height) positioned in the middle of an 8-m long pathway. A force platform was used to analyze CoP parameters of the stance phase of the trailing limb (most affected limb). The ability of each outcome measure to predict fall risk at four, six, and 12 months was assessed using receiver operating characteristic curve analyses. ResultsTen individuals (23.8%) were considered fallers at four months, twelve individuals (28.5%) at six months, and twenty-one individuals (50%) at 12 months. CoP amplitude and CoP velocity in the mediolateral direction significantly predicted fall risk at four, six, and 12 months. As judged by the area under the curve, mediolateral CoP velocity showed the best performance at four months, while mediolateral CoP amplitude showed the best performance at six months. Fallers presented greater values of mediolateral CoP velocity and amplitude than non-fallers. ConclusionThese findings suggest that mediolateral CoP velocity and amplitude during obstacle crossing might be useful to predict fall risk in people with PD. Therefore, larger studies are encouraged.

Effects of water immersion on quasi-static standing exploring center of pressure sway and trunk acceleration: a case series after incomplete spinal cord injury.

This work is a case series. We assessed the influence of the aquatic environment on quasi-static posture by measuring center of pressure (COP) sway and trunk acceleration parameters after incomplete spinal cord injury (iSCI) in water and on land. Tertiary Rehabilitation Hospital, Ontario, Canada. Six adult participants with iSCI (4 cervical/2 thoracic injuries, AIS D) were enrolled. Baseline balance was assessed by the Berg Balance Scale and Mini-Balance Evaluation System Test. Participants stood on a waterproof force plate for one minute per trial on land and in water; participants completed testing with their eyes open or closed in random order over 10 trials. Individuals' perceptions of their standing balance were obtained. COP and trunk acceleration parameters were analyzed in the time-domain. COP sway and upper to lower trunk acceleration ratios in the AP direction increased in water, which was in contrast to standing on land in both visual conditions for 5/6 participants. Three participants (P1, P3 & P4) with greater sensorimotor deficits had larger COP sway in water with the eyes closed. Two (P1 & P4) of six participants reported more discomfort standing in water than standing on land. Increased COP sway seemed to reflect the balance and sensorimotor impairments of the participants, especially when standing with eyes closed in water. Although most participants (4/6) perceived that they swayed more in water in contrast to on land, 5 out of 6 participants reported that water felt like a safer environment in which to stand.

“Study of Neuromuscular and Proprioceptive Training Program on Postural Stability in Active Middle-Aged Men”

Background: The risk of falling increases with age, and the outcome might sometimes be severe injury or even death. Objectives: This study was designed to determine whether a 12-week neuromuscular and proprioceptive training (NPT) plan was impressive on postural stability of active middle-aged men. Methods: The study had a quasi-experimental design with a control group. In 2016, 50 middle-aged males of the Ukrainian Sports Medicine Center (Kiev) were randomly divided to experimental (performed the NPT program, rather than general warm-up routines) and control groups (maintained the general warm-up routines). The mean center of pressure (CoP) fluctuations of postural stability was assessed during eyes open (EO) and closed (EC) using a force platform in the two directions, before and after the 12-week study. Results: The intervention leads to a significant improvement in the mean CoP velocity in both planes (P < 0.05) in the experimental group compared to the control. All CoP parameters used in this study showed very large correlations. Conclusions: The NPT program had a positive effect on postural stability. This may have a direct impact on reducing lower limb injury in middle-aged men.

Postural control after unexpected external perturbation: Effects of Parkinson’s disease subtype

Different clinical subtypes of Parkinson’s disease (PD) have long been recognized. Recent studies have focused on two PD subtypes: Postural Instability and Gait Difficulty (PIGD) and Tremor Dominant (TD). PIGD patients have greater difficulties in postural control in relation to TD. However, knowledge about the differences in reactive adjustment mechanisms following a perturbation in TD and PIGD is limited. This study aimed to compare reactive postural adjustments under unexpected external perturbation in TD, PIGD, and control group (CG) subjects. Forty-five individuals (15 TD, 15 PIGD, and 15 CG) participated in this study. Postural perturbation was applied by the posterior displacement of the support surface in an unexpected condition. The velocity (15 cm/s) and displacement (5 cm/s) of perturbation were the same for all participants. Center of pressure (CoP) and center of mass (CoM) were analyzed for two reactive windows after the perturbation (0–200 ms and 200–700 ms). The Bonferroni post hoc test indicated a higher range of CoP in the PIGD when compared to the CG (p = 0.021). The PIGD demonstrated greater time to recover the stable posture compared to the TD (p = 0.017) and CG (p = 0.003). Furthermore, the TD showed higher AP-acceleration peak of CoM when compared to the PIGD (p = 0.048) and CG (p = 0.013), and greater AP-acceleration range of CoM in relation to the CG (p = 0.022). These findings suggest that PD patients present worse reactive postural control after perturbation compared to healthy older individuals. CoP and CoM parameters are sensitive to understand and detect the differences in reactive postural mechanisms in PD subtypes.

Neural control of postural sway: Relationship to strength measures in young and elderly adults.

Age-related changes in postural sway are well-established, and studied from a control perspective using an inverted pendulum model. The purpose of the present work was to expand previous research in this area by investigating relationships between sway-related control parameters and musculoskeletal measures of muscle function and health. Eleven female older adults and eight female young adults completed blood draw, grip, leg extension, and balance tests. Serum levels of skeletal muscle-specific troponin T (sTnT), a biomarker for muscle health, were obtained from blood samples. Maximal grip force and leg extension torque were obtained from dynamometer tests. Center of pressure parameters were derived from force platform records obtained during eyes open and eyes closed balance tests. Sway control parameters were derived from an inverted pendulum model with PID-feedback control. Regression analyses were used to quantify the relationship between model parameters and grip strength, leg strength, and sTnT. Model integral gain (Ki) was observed to significantly predict grip strength in the eyes open condition. In the eyes closed condition, model derivative gain (Kd) was observed to significantly predict sTnT, and both proportional (Kp) and noise (Kn) model gains were observed to significantly predict grip and leg strength measures. Collectively, the relationship between control (Ki, Kd, Kp) and musculoskeletal health (strength, sTnT) parameters suggests a compensation mechanism, which may have served to minimize effects of reduced muscle function on sway amplitude, overshoot, and accuracy. Most associations were observed during eyes closed conditions, suggesting that visual input plays a larger role in regulating balance than the proposed compensation mechanisms. This work highlights the potential use for both strength and sTnT tests as biomarkers for postural control and balance impairment in older adults.

Ski Boots Do Not Impair Standing Balance by Restricting Ankle-Joint Mobility.

This study was undertaken in order to provide new insight into sensorimotor control of posture when wearing high-shaft (HS) boots as ski boots. Previous studies into the effects of HS boots on postural control have produced controversial results. Some studies reported postural control impairments with ski boots in bipedal postural tasks due to ankle movement restrictions without quantifying the actual restrictive effect of these boots and specifying the adaptations of the postural control system. Eighteen young healthy subjects took part in the experiment. Bilateral postural control was assessed on stable and unstable surfaces, while standing barefoot or wearing ski boots. Center of pressure (COP) parameters, ankle, knee, and hip joints movements were calculated and EMG activity from main postural muscles was recorded. Ski boots did not restrict the amplitude of ankle angular movements and largely impacted COP parameters and EMG activity on stable ground. In conditions of mediolateral instability, COP data illustrated an enhanced postural control in the frontal plane when wearing ski boots. Ski boots do not affect bipedal postural balance by restricting the ankle angular motions but induce complex adaptations of the postural control system which combine factors of a mechanical, motor, and sensorial nature. They impede postural control mainly when standing on stable ground without producing similar deleterious effects on unstable surfaces. Our results show that HS boots as ski boots can improve lateral balance on unstable surfaces, which can contribute to prevent fall risk and ankle sprain.