Medial-lateral Center Of Pressure Research Articles

The Influence of Dopaminergic Medication on Regularity and Determinism of Gait and Balance in Parkinson's Disease: A Pilot Analysis.

Background/Objectives: Understanding how dual-tasking and Parkinson's disease medication affect gait and balance regularity can provide valuable insights to patients, caregivers, and clinicians regarding frailty and fall risk. However, dual-task gait and balance studies in PD most often only employ linear measures to describe movement regularity. Some have used nonlinear techniques to analyze PD performances, but only in the on-medication state. Thus, it is unclear how the nonlinear aspects of gait or standing balance are affected by PD medication. This study aimed to assess how dopaminergic medication influenced the regularity and determinism of joint angle and anterior-posterior (AP) and medial-lateral (ML) center of pressure (COP) path time-series data while single- and dual-tasking in PD. Methods: Sixteen subjects with PD completed single- and dual-task gait and standing balance trials for 3 min off and on dopaminergic medication. Sample entropy and percent determinism were calculated for bilateral hip, knee, and shoulder joints, and the AP and ML COP path. Results: There were no relevant medication X task interactions for either the joint angles series or the balance series. Instead, the results supported independent effects of medication, dual-tasking, or standing with eyes closed. Balance task difficulty (i.e., eyes open vs. eyes closed) was detected by the nonlinear analyses, but the nonlinear measures yielded opposing results such that standing with eyes closed simultaneously yielded less regular and more deterministic signals. Conclusions: When juxtaposed with previous findings, these results suggest that medication-induced functional improvements in people with PD might be accompanied by a shift from lesser to greater signal consistency, and the effects of dual-tasking and standing with eyes closed were mixed. Future studies would benefit from including both linear and nonlinear measures to better describe gait and balance performance and signal complexity in people with PD.

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.

Kinesiotaping Is Not Better Than a Placebo: Kinesiotaping for Postural Control in Anterior Cruciate Ligament-Reconstructed Patients-A Randomized Controlled Trial.

The primary aim of this study was to investigate the immediate and delayed effects of kinesiotape (KT) on postural control and patient-reported outcome measures under challenging conditions in individuals with anterior cruciate ligament reconstructions. Thirty-two anterior cruciate ligament-reconstructed patients for whom 6months had passed since their operation were randomly assigned to either the KT (n = 16, aged 21.8 [5.5]y) or the placebo KT (n = 16, aged 24.0 [5.1]y) groups. Initially, both groups stood barefoot on a force platform while performing postural tasks in 4 randomized conditions (eyes open, eyes closed, cognitive task, and foam). Before the experiment, patients would bring the 4 conditions, which were written on folded papers, one by one, and in this way, the order of conditions for the examiners was determined. The patients' evaluations were conducted immediately and 48hours after KT application. Postural control measures, with area and displacement of the center of pressure (CoP) in anterior-posterior and medial-lateral directions, and mean total velocity displacement of CoP (MVELO CoP) served as dependent variables. In addition, the International Knee Documentation Committee score was measured pretreatment and 48hours posttreatment. Significant group-by-time interactions were observed for displacement of COP in medial-lateral direction (P = .002) and MVELO CoP (P = .034). MVELO CoP significantly decreased (mean difference = 0.60, P = .009) immediately after KT application compared with preapplication measures. In the placebo group, a statistically significant decrease in MVELO CoP (mean difference = 0.869, P = .001) was observed at 48hours post-KT compared with preapplication values. International Knee Documentation Committee scores significantly improved at 48hours post-KT application in both groups (P < .05). Though observed at different time points, both KT (immediately after the intervention) and placebo KT (48h after the intervention) were found to improve postural control measures. It appears that the changes in postural control may be more related to proprioceptive enhancement due to KT rather than the specific KT pattern.

DFA as a window into postural dynamics supporting task performance: does choice of step size matter?

Introduction: Detrended Fluctuation Analysis (DFA) has been used to investigate self-similarity in center of pressure (CoP) time series. For fractional gaussian noise (fGn) signals, the analysis returns a scaling exponent, DFA-α, whose value characterizes the temporal correlations as persistent, random, or anti-persistent. In the study of postural control, DFA has revealed two time scaling regions, one at the short-term and one at the long-term scaling regions in the diffusion plots, suggesting different types of postural dynamics. Much attention has been given to the selection of minimum and maximum scales, but the choice of spacing (step size) between the window sizes at which the fluctuation function is evaluated may also affect the estimates of scaling exponents. The aim of this study is twofold. First, to determine whether DFA can reveal postural adjustments supporting performance of an upper limb task under variable demands. Second, to compare evenly-spaced DFA with two different step sizes, 0.5 and 1.0 in log2 units, applied to CoP time series. Methods: We analyzed time series of anterior-posterior (AP) and medial-lateral (ML) CoP displacement from healthy participants performing a sequential upper limb task under variable demand. Results: DFA diffusion plots revealed two scaling regions in the AP and ML CoP time series. The short-term scaling region generally showed hyper-diffusive dynamics and long-term scaling revealed mildly persistent dynamics in the ML direction and random-like dynamics in the AP direction. There was a systematic tendency for higher estimates of DFA-α and lower estimates for crossover points for the 0.5-unit step size vs. 1.0-unit size. Discussion: Results provide evidence that DFA-α captures task-related differences between postural adjustments in the AP and ML directions. Results also showed that DFA-α estimates and crossover points are sensitive to step size. A step size of 0.5 led to less variable DFA-α for the long-term scaling region, higher estimation for the short-term scaling region, lower estimate for crossover points, and revealed anomalous estimates at the very short range that had implications for choice of minimum window size. We, therefore, recommend the use of 0.5 step size in evenly spaced DFAs for CoP time series similar to ours.

Precision aiming performance with the paretic upper limb is associated with center of pressure patterns in individuals with chronic stroke

BackgroundIndividuals with stroke commonly demonstrate upper-limb sensorimotor impairments. Upper-limb tasks occur against a background level of postural control and thus require a flexible postural control system to facilitate performance. Anterior precision aiming tasks, for example, benefit from lower medial-lateral (ML) center of pressure (COP) fluctuations (where increased fluctuations erode performance) relative to anterior-posterior (AP) fluctuations (where increased fluctuations do not strongly influence performance). After stroke, individuals may compensate for upper-limb impairments by increasing trunk movement which increases overall COP fluctuations and thus may make it more difficult to modulate COP in a task-sensitive manner. Research questionDo upper-limb task demands modulate COP movement patterns after stroke? MethodsIn this cross-sectional study, adults with chronic stroke (n = 23) and unilateral upper-limb impairments were immersed in a virtual environment displaying an anterior target. Participants aimed to maintain the position of a virtual laser pointer (via handheld controller) in the target with each hand. COP was concurrently recorded. Mixed effects models and correlations were used to detect differences in COP patterns between limbs and movement planes and evaluate associations between task performance and COP patterns, respectively. ResultsParticipants showed greater COP standard deviation and regularity in the AP compared to the ML direction. The magnitude of difference between AP and ML COP metrics was greater using the nonparetic limb. Task performance was moderately and positively associated with task-sensitive COP patterns (i.e., higher AP:ML ratios of COP metrics) using the paretic upper limb. Participants consistently demonstrated high levels of task performance and task-sensitive COP movement patterns using the nonparetic limb. SignificanceImpairments in postural control after stroke may be related to the upper limb used. It is important to recognize the role of directional COP variability and regularity in the context of a task goal after stroke.

Effect of foot progression angle alteration on medial-lateral center of pressure position during single-leg standing.

[Purpose] This study aimed to investigate the effect of altering the foot progression angle (FPA) on the center of pressure (COP) position during single-leg standing. [Participants and Methods] Fifteen healthy adult males participated. The participants performed single-leg standing on the left leg in three different FPA conditions, namely toe-in, neutral, and toe-out, in which the FPA was set to 0°, 10°, and 20°, respectively. The COP positions and pelvis angles were measured using a 3D motion analysis system, and each measurement value among the three conditions was compared. [Results] The medial-lateral COP position differed among conditions in the coordinate system based on the laboratory condition but did not differ in the coordinate system based on the longitudinal axis of the foot segment. Moreover, no changes were observed in pelvis angles that would affect COP position. [Conclusion] Altering the FPA does not change the medial-lateral position of the COP during single-leg standing. Here we show that COP displacement based on the laboratory coordinate system is involved in the mechanism-linking alteration of FPA and changes in knee adduction moment.

Effects of virtual reality immersion on postural stability during a dynamic transition task

ABSTRACT Dynamic postural stability paradigms with virtual reality (VR) provide a means to simulate real-world postural challenges and induce customised but controlled perturbations. The purpose of this study was to determine the effects of a VR unanticipated perceptual sport perturbation on postural stability compared to traditional methods. Sixteen individuals between the ages of 18–23 years (19.5 ± 1.4 years) with no history of injury within 12 months were recruited. A double-leg to single-leg transition task was performed on a force plate in one of the following conditions: eyes open (EO), eyes closed (EC), a sport video with a standard non-immersive computer monitor (SV), and VR. The VR and SV conditions used a pre-recorded tackle avoidance task video where participants shifted to a leg in the opposite direction of a simulated opponent, while EC and EO were completed with auditory prompts. Relative to the EO condition, EC and VR induced greater postural instability. The largest effect sizes were between VR and EO for path length (g = 3.57), mean velocity anterior-posterior centre of pressure (CoP) (g = 3.65), and mean velocity medial-lateral CoP (g = 3.27). By including VR, the difficulty of a clinically based postural stability task was increased to the level of EC while accounting for the sporting environment.

A Wearable Real-time Kinematic and Kinetic Measurement Sensor Setup for Human Locomotion.

Current laboratory-based setups (optical marker cameras + force plates) for human motion measurement require participants to stay in a constrained capture region which forbids rich movement types. This study established a fully wearable system, based on commercially available sensors (inertial measurement units + pressure insoles) that can measure both kinematic and kinetic motion data simultaneously and support wireless frame-by-frame streaming. In addition, its capability and accuracy were tested against a conventional laboratory-based setup. An experiment was conducted, with 9 participants wearing the wearable measurement system and performing 13 daily motion activities, from slow walking to fast running, together with vertical jump, squat, lunge and single-leg landing, inside the capture space of the laboratory-based motion capture system. The recorded sensor data were post-processed to obtain joint angles, ground reaction forces (GRFs), and joint torques (via multi-body inverse dynamics). Compared to the laboratory-based system, the established wearable measurement system can measure accurate information of all lower limb joint angles (Pearson's r = 0.929), vertical GRFs (Pearson's r = 0.954), and ankle joint torques (Pearson's r = 0.917). Center of pressure (CoP) in the anterior-posterior direction and knee joint torques were fairly matched (Pearson's r = 0.683 and 0.612, respectively). Calculated hip joint torques and measured medial-lateral CoP did not match with the laboratory-based system (Pearson's r = 0.21 and 0.47, respectively). Furthermore, both raw and processed datasets are openly accessible (https://doi.org/10.5281/zenodo.6457662). Documentation, data processing codes, and guidelines to establish the real-time wearable kinetic measurement system are also shared (https://github.com/HuaweiWang/WearableMeasurementSystem).

Effects of arch support doses on the center of pressure and pressure distribution of running using statistical parametric mapping.

Insoles with an arch support have been used to address biomechanical risk factors of running. However, the relationship between the dose of support and running biomechanics remains unclear. The purpose of this study was to determine the effects of changing arch support doses on the center of pressure (COP) and pressure mapping using statistical parametric mapping (SPM). Nine arch support variations (3 heights * 3 widths) and a flat insole control were tested on fifteen healthy recreational runners using a 1-m Footscan pressure plate. The medial-lateral COP (COPML) coordinates and the total COP velocity (COPVtotal) were calculated throughout the entirety of stance. One-dimensional and two-dimensional SPM were performed to assess differences between the arch support and control conditions for time series of COP variables and pressure mapping at a pixel level, respectively. Two-way ANOVAs were performed to test the main effect of the arch support height and width, and their interaction on the peak values of the COPVtotal. The results showed that the COPVtotal during the forefoot contact and forefoot push off phases was increased by arch supports, while the COP medial-lateral coordinates remained unchanged. There was a dose-response effect of the arch support height on peak values of the COPVtotal, with a higher support increasing the first and third valleys but decreasing the third peak of the COPVtotal. Meanwhile, a higher arch support height shifted the peak pressure from the medial forefoot and rearfoot to the medial arch. It is concluded that changing arch support doses, primarily the height, systematically altered the COP velocities and peak plantar pressure at a pixel level during running. When assessing subtle modifications in the arch support, the COP velocity was a more sensitive variable than COP coordinates. SPM provides a high-resolution view of pressure comparisons, and is recommended for future insole/footwear investigations to better understand the underlying mechanisms and improve insole design.

Changes in postural sway during upright stance after short-term lower limb physical inactivity: A prospective study.

Previous studies have reported that motor behavior is affected by short-term physical inactivity using cast immobilization; however, the effects of inactivity on postural sway are not well-understood. This study aimed to investigate the effects of short-term lower limb disuse on postural sway in the upright position after cast removal. Twenty-two healthy young adults were enrolled, and each participant’s lower limb on one side was fixed with a soft bandage and medical splint made from metal and soft urethane for 10 h. Fluctuations in the center of pressure (COP) were measured before and after immobilization; the total trajectory length, mean velocity, COP root mean square (RMS) area, mean medial-lateral (M-L) COP, and mean anterior-posterior (A-P) COP were selected as evaluation parameters. Compared with the postural sway before cast application, we noted an increase and shift (from the fixed to the nonfixed side) in the postural sway after cast removal. Our results therefore suggest that short-term disuse may cause acute changes in COP movements during quiet standing. Moreover, patients may maintain their standing posture by adopting a compensatory strategy involving lateral control, similar to individuals with stroke and patients who have undergone total knee arthroplasty.

Objective Evaluation of Neurogenic Intermittent Claudication for Patients With Lumbar Spinal Stenosis Based on Plantar Pressure Analysis.

A cross-sectional study. To quantify the severity of neurogenic intermittent claudication (NIC) for patients with lumbar spinal stenosis (LSS) based on the center of pressure trajectory. NIC is one of the typical symptoms of LSS. So far, the severity level of NIC is mainly evaluated by the subjective description of patients, which might be biased by patients' background differences and thus lead to an ineffective diagnosis or inappropriate treatment for LSS. Therefore, it remains necessary to develop a reliable clinical technique for quantitative evaluation of NIC to achieve more effective therapy for LSS. In the present study, the Footscan pressure system was used to detect the center of pressure trajectory. The real-time walking distance (rtWD) and the corresponding displacement of the medial-lateral center of pressure (ML-COP) were calculated based on the trajectory. The differences of ML-COP between LSS and control groups were analyzed using a one-way repeated measures analysis of variance. Regression and Pearson correlation analysis were used to investigate the correlation between rtWD and ML-COP, as well as the relation between the Oxford Claudication Score (OCS) and clinical evaluation indicators. The present study included 31 LSS patients and 31 healthy controls. There were no significant differences in demographic data between the two groups ( P >0.05). The results indicated that ML-COP would increase with the number of laps in the LSS group while not in the control group. Also, a linear relationship was identified between the ML-COP and rtWD for LSS patients ( R2 >0.80, P <0.05). Since the incremental rate of ML-COP for LSS patients was reflected by the regression coefficients of the linear regression analysis, thus the regression coefficients were defined as the claudication correlation coefficients (CCCs). In addition, it was indicated by the statistical analysis that there was a strong positive correlation between OCS and CCC ( r =0.96; P <0.001) and a medium negative correlation with final walking distance ( r =-0.67; P <0.001). It was also noticed that there was no significant correlation between the average ML-COP and OCS ( r =-0.03; P =0.864). The ML-COP of LSS patients would increase with the patients' walking distance. This incremental rate, characterized by the CCC, would be used as an effective indicator to quantify the severity level of the NIC for potentially more accurate and reliable diagnosis, evaluation, and treatment of LSS. 3.

Postural Control Differences between Patients with Posterior Tibial Tendon Dysfunction and Healthy People during Gait.

Background: Patients with posterior tibial tendon dysfunction (PTTD) may exhibit postural instability during walking likely due to a loss of medial longitudinal arch, abnormal foot alignment, and pain. While many studies have investigated gait alterations in PTTD, there is no understanding of dynamic postural control mechanisms in this population during gait, which will help guide rehabilitation and gait training programs for patients with PTTD. The purpose of the study was to assess dynamic postural control mechanisms in patients with stage II PTTD as compared to age and gender matched healthy controls. Methods: Eleven patients with stage II PTTD (4 males and 7 females; age 59 ± 1 years; height 1.66 ± 0.12 m; mass 84.2 ± 16.0 kg) and ten gender and age matched controls were recruited in this study. Participants were asked to walk along a 10 m walkway. Ten Vicon cameras and four AMTI force platforms were used to collect kinematic and center of pressure (COP) data while participants performed gait. To test differences between PTTD vs. control groups, independent t-tests (set at α < 0.05) were performed. Results: Patients with PTTD had significantly higher double stance ratio (+23%) and anterior-posterior (AP) time to contact (TTC) percentage (+16%) as compared to healthy control. However, PTTD had lower AP COP excursion (−19%), AP COP velocity (−30%), and medial-lateral (ML) COP velocity (−40%) as compared to healthy controls. Mean ML COP trace values for PTTD were significantly decreased (−23%) as compared to controls, indicating COP trace for PTTD tends to be closer to the medial boundary than controls during single-support phase of walking. Conclusion: PTTD patients showed more conservative and cautious postural strategies which may help maintain balance and reduce the need for postural adjustment during PTTD gait. They also showed more medially shifted COP patterns than healthy controls during single-support phase of walking. Dynamic postural control outcomes could be used to develop effective gait training programs aimed at alleviating a medial shift of COP (everted foot) for individuals with PTTD in order to improve their functionality and gait efficiency.

Postural Control in Unipedal Quiet Stance in Young Female Gymnasts and the Effects of Training with Consideration of Transient Behavior of Postural Sway.

The purpose of this study was twofold: (a) to compare postural control between a group of young female gymnasts (n = 15; age: 11.2 ± 1.9 years) and non-trained peers (n = 15; age: 10.9 ± 2.0 years), and (b) to investigate the effect of an 8-week whole body exercise intervention program on postural control in young female gymnasts. Postural control was assessed by recording center of pressure (CoP) movements during unipedal quiet stance. Velocity and amplitude of CoP movement in anterior-posterior (AP) and medial-lateral (ML) directions were considered. In addition to common trial-averaged CoP outcomes, we also considered the transient behavior of CoP movements, by calculating relative differences between the 1st and 2nd, and the 1st and 3rd 10-s intervals within the whole trial (DIF_21 and DIF_31, respectively). The gymnast group had lower total CoP velocity (Cohen’s d = 0.97) and AP amplitude (Cohen’s d = 0.85), compared to their non-trained peers. The gymnasts also had lower CoP AP amplitude DIF21 (Cohen’s d = 0.73), with almost constant values across all intervals. After the training ML CoP velocity was reduced for 13.12% (Cohen’s d = 0.60), while ML CoP amplitude increased (Cohen’s d = −0.89).

Dose-response effects of forefoot and arch orthotic components on the center of pressure trajectory during running in pronated feet

BackgroundFoot orthoses are widely used in runners with pronated feet, who are characterized with large forefoot abduction and arch deformation during gait. However, the relationship between the amount of forefoot and arch orthotic correction and the alterations in foot biomechanics remains unclear. Research questionThis study aimed to determine dose-response effects of foot orthoses with forefoot wedge and arch support components on the center of pressure (COP) trajectories and pressure distribution during running in symptomatic pronated feet. MethodsFifteen recreational runners participated in this study. A pressure plate was used to measure plantar pressures during running with control shoe only and ten foot orthoses, varying in forefoot wedges (5 levels) and arch supports (2 levels). The COP trajectory across the entire stance phase was compared between orthotic and control conditions using one-dimensional statistical parametric mapping. The differences in the force-time integral (FTI) and temporal variables were explored between conditions using repeated measures ANOVAs. The main effect of the two orthotic components and their interaction on tested variables were examined using two-way ANOVAs. ResultsA forefoot wedge, whether laterally or medially located, shifted the COP trajectory laterally during some subphases of running (p < 0.05), while using an arch support only had minimal effect on the COP. Almost all orthoses reduced the FTI on the 2nd metatarsal and medial heel, and only medial forefoot wedges reduced the FTI on the hallux. There was a linear effect of forefoot wedges on the medial-lateral COP displacements during the propulsion phase, but no interactions were found between two orthotic components. SignificanceThese findings suggest that forefoot orthotic components rather than arch supports are effective in altering forefoot dynamics in runners with pronated feet. This study could have implications for foot orthotic prescription and running-related injury prevention for individuals with pronated feet.

Transient characteristics of body sway during single-leg stance in athletes with a history of ankle sprain

BackgroundThe role of the measurements of postural stability in the context of screening for ankle sprain risk is still equivocal. Transient characteristics of body sway have been suggested as an alternative or an improvement to traditional whole-trial analyses. Research questionAre transient characteristics of body sway sensitive to the history of ankle sprain?. MethodsThe assessment of 30-s single-leg body sway was performed on a group of 93 athletes from basketball, soccer, tennis and running who reported at least 1 ankle sprain in the last 12 months, while a group of 244 athletes from the same disciplines served as a control group without an ankle sprain reported for the same time period. We considered the mean center-of-pressure (CoP) velocity, CoP amplitude and CoP frequency. In addition to traditional whole-trial variables, we calculated the relative differences between the 1 st and the 2nd (DIF_21) and 1 st and 3rd (DIF_31) 10-s time intervals within the whole trial. ResultsThe indexes of transient characteristics of body sway (i.e., the DIF_21 and DIF_31) were in trivial or weak correlations with whole-trial variables (all r ≤ 0.29). Athletes with ankle sprain history exhibited smaller CoP ML velocity (p = 0.002) and larger CoP ML frequency (p = 0.001). In the injured group, the injured leg exhibited lower total and medial-lateral (ML) CoP velocity (p = 0.005−0.040), as well as lower CoP ML amplitude (p = 0.002) and higher CoP ML frequency (p = 0.010). The transient characteristics of body sway (DIF_21 and DIF_31) were very similar between the groups and between the injured and uninjured legs. SignificanceTransient characteristics of body sway do not appear to differentiate the athletes with and without a history of ankle sprain. Further research is needed to confirm if the transient characteristics of body sway could be used for detection of risk of falls in older adults or assessment of athletic performance.

The Design and Simulation of a 16-Sensors Plantar Pressure Insole Layout for Different Applications: From Sports to Clinics, a Pilot Study.

The quantification of plantar pressure distribution is widely done in the diagnosis of lower limbs deformities, gait analysis, footwear design, and sport applications. To date, a number of pressure insole layouts have been proposed, with different configurations according to their applications. The goal of this study is to assess the validity of a 16-sensors (1.5 × 1.5 cm) pressure insole to detect plantar pressure distribution during different tasks in the clinic and sport domains. The data of 39 healthy adults, acquired with a Pedar-X® system (Novel GmbH, Munich, Germany) during walking, weight lifting, and drop landing, were used to simulate the insole. The sensors were distributed by considering the location of the peak pressure on all trials: 4 on the hindfoot, 3 on the midfoot, and 9 on the forefoot. The following variables were computed with both systems and compared by estimating the Root Mean Square Error (RMSE): Peak/Mean Pressure, Ground Reaction Force (GRF), Center of Pressure (COP), the distance between COP and the origin, the Contact Area. The lowest (0.61%) and highest (82.4%) RMSE values were detected during gait on the medial-lateral COP and the GRF, respectively. This approach could be used for testing different layouts on various applications prior to production.

The Effect of High-Intensity Intermittent Training on the Acute Gait Plantar Pressure in Healthy Young Adults

High-intensity intermittent training (HIIT) has been successfully applied in various sports activities, as HIIT was considered as one of the most efficient training methods of exercise for improving physical performance and reducing the weight of overweight individuals. However, its acute effects of HIIT on gait and balance performance were not addressed. Thus, in this study we examined the acute effects of HIIT on dynamic postural control compared with steady-state training (SST) by analyzing plantar pressure parameters. In this study, sixteen healthy male adults were examined in 3 days. After exhaustive ramp-like cycle ergometer testing, the maximal heart rate (HRmax) of each participant was determined on the first day, then either a 20 minutes HIIT at 80–90% of HRmax or a 20 minutes SST at 60% of HRmax was randomly performed on the second and third day, respectively. Plantar pressure parameters were collected at comfortable walking velocity immediately after HIIT and SST respectively, and compared with the baseline data of plantar pressure gathered before maximal ramp test on the first day. The results showed significant differences in the plantar pressure in these three conditions of gait. Compared to pre-intervention and pre-SST, peak pressure and maximum force in the middle and lateral metatarsal increased significantly in post-HIIT. Meanwhile, the foot balance data indicate that post-HIIT exhibits more foot pronation than baseline. The center of pressure (COP) trajectory was medially shifted during the stance phase in post-SST, and noticeably in post-HIIT. The displacement and velocity of medial-lateral COP in the initial contact phase were greater in post-HIIT; while during the forefoot contact phase, post-HIIT showed fewer time percentages and greater velocity of medial-lateral COP. In conclusion, a single high-intensity intermittent training session adversely affected the acute dynamic postural control than steady-state training in healthy male adults.

A Randomized Controlled Study Assessing the Effects of a Shoe Lift Under the Nonparetic Leg on Balance Performance in Individuals With Chronic Stroke.

Improvement of balance and postural stability is an important goal in stroke rehabilitation. The purpose of this study was to investigate the effects of a shoe lift under the nonparetic leg on balance function and balance confidence in persons with chronic stroke. Thirty-six individuals with chronic stroke (21 males and 15 females), who were able to walk independently and showed stance asymmetry, were randomized to a shoe insert and a control group. The interventions included a 6-week balance training program, in conjunction with a shoe lift under the nonaffected leg (shoe insert group, n = 18), or balance training alone (control group, n = 18). The outcome measures were weight-bearing asymmetry (WBA), root mean square (RMS) of anterior-posterior (AP) and medial-lateral (ML) center-of-pressure (COP) velocity asymmetry, Berg Balance Scale (BBS), and Activities-specific Balance Confidence (ABC) Scale. These were measured in both groups at baseline, after the intervention, and at a 3-month follow-up. A repeated-measure multivariate analysis of variance was conducted to evaluate the impact of 2 different interventions on balance measures, across the 3 periods. No significant between-group differences were found for demographics and stroke-related characteristics of participants (P > .05). The outcome measures between the 2 groups were not significantly different at baseline (P > .05). There were between-group differences for WBA and the RMS of AP COP velocity asymmetry after the intervention and at the 3-month follow-up (P < .05). No significant difference in the RMS of ML COP velocity asymmetry, BBS, and ABC was identified between the 2 groups after the intervention and at the 3-month follow-up (P > .05). The results indicated that the use of a shoe lift under the nonaffected leg in the context of a balance training program could result in a greater improvement in static standing balance as compared with balance training alone in an individual with chronic stroke. The study was retrospectively registered in the Iranian Registry of Clinical Trials (IRCT20190603043808N1).

Intrinsic foot muscles act to stabilise the foot when greater fluctuations in centre of pressure movement result from increased postural balance challenge

BackgroundIncreased postural balance challenge is associated with more fluctuations in centre of pressure movement, indicating increased interference from the postural control system. The role of intrinsic foot muscles in balance control is relatively understudied and whether such control system interference occurs at the level of these muscles is unknown. Research QuestionDo fewer fluctuations in intrinsic foot muscle excitation occur in response to increased postural balance challenge? MethodsSurface EMGs were recorded using a grid of 13 × 5 channels from the plantar surface of the foot of 17 participants, who completed three balance tasks: bipedal stance; single leg stance and bipedal tip-toe. Centre of pressure (CoP) movement was calculated from simultaneously recorded force plate signals. Fluctuations in CoP and EMGs for each task were quantified using a sample entropy based metric, Entropy Halflife (EnHL). Longer EnHL indicates fewer signal fluctuations. ResultsThe shortest EMG EnHL, 9.27 ± 3.34 ms (median ± interquartile range), occurred during bipedal stance and the longest during bipedal tip-toe 15.46 ± 11.16 ms, with 18.80 ± 8.00 ms recorded for single leg stance. Differences were statistically significant between bipedal stance and both bipedal tip-toe (p < 0.001) and single leg stance (p < 0.001). CoP EnHL for both anterior-posterior and medial-lateral movements also differed significantly between tasks (p < 0.001, both cases). However, anterior-posterior CoP EnHL was longest for bipedal stance 259.84±230.22 ms and shortest for bipedal tip-toe 146.25±73.35 ms. Medial-lateral CoP EnHL was also longest during bipedal stance 215.73±187.58 ms, but shortest for single leg stance 113.48±83.01 ms. SignificanceFewer fluctuations in intrinsic foot muscle excitation occur in response to increased postural balance challenge. Fluctuations in CoP movement during balance must be predominantly driven by excitation of muscles extrinsic to the foot. Intrinsic foot muscles therefore likely play a greater role in stabilisation of the foot than balance control during the postural tasks studied.

Alterations in medial-lateral postural control after anterior cruciate ligament reconstruction during stair use

BackgroundDynamic postural control during everyday tasks is poorly understood in people following anterior cruciate ligament reconstruction (ACLR). Understanding dynamic postural control can provide insight into potentially modifiable impairments in people following ACLR who are at increased risk for second ACL injury and/or knee osteoarthritis. Research questionDetermine whether measures indicative of dynamic postural control differ between individuals with and without ACLR during stair ascent and descent. Methods: Seventeen individuals with ACLR (>1 yr post-surgery) and 16 age and sex-matched healthy controls participated. Centre of pressure (COP) measures included: i) COP excursion, ii) COP velocity, and iii) dynamic time-toboundary (TTB). Mixed linear models were used to compare COP measures for the ACLR leg, non-ACLR leg, and healthy controls during stair ascent and stair descent. ResultsThere were no statistically significant differences observed during stair ascent (all p > 0.05). Several statistical differences were found during stair descent for individual with ACLR, but not between those with ACLR and healthy controls. The ACLR leg had higher medial-lateral COP excursion (mean difference 1.06 cm, [95 %CI 0.08–2.06 cm], p = 0.036; effect size = 0.38) compared to the non-ACLR leg during stair descent. In addition, the ACLR leg had a lower medial-lateral TTB (mean difference −13 ms [95 %CI −38 to 2 ms], p = 0.005; effect size = 0.49) and medial-lateral TTB normalized to stance time (mean difference −5.8 % [95 %CI −10.3 to 1.3 %], p = 0.012; effect size = 0.80) compared to the non-ACLR leg during stair descent. No statistical differences were observed for anterior-posterior measures during stair descent (all p > 0.05). Significance: Taken together, findings indicate that there are small to large differences in medial-lateral postural control in the ACLR leg compared to the non-ACLR leg during stair descent. Further work is required to understand clinical implication of these novel observations.