Anteroposterior Center Of Pressure Research Articles

Effects of Combining Transcranial Direct Current Stimulation With Balance Training on Anticipatory Postural Adjustments in Persons With Chronic Ankle Instability.

The combination of transcranial direct current stimulation (tDCS) with balance training could integrate central and peripheral neural mechanisms. This study aimed to investigate the effects of concurrent balance training and tDCS over the supplementary motor area (SMA) on anticipatory postural adjustments during gait initiation (GI) in persons with chronic ankle instability (CAI). Balance training will increase the center of pressure (COP) velocity and displacement during GI phases in all participants, and those receiving real tDCS will show greater increases. Randomized controlled trial. Level 2. A total of 32 subjects were allocated to 2 groups: (1) intervention (balance training plus real tDCS) and (2) control (balance training plus sham tDCS). Outcome measures were COP-related parameters (displacement and velocity) during phases of GI (anticipatory, weight transition, and locomotor). The results showed that, in the anticipatory phase, the anteroposterior displacement of the COP was increased significantly at posttest relative to pretest across both groups, F(1,30) = 5.733, P = 0.02. In addition, both groups revealed an increase in the mediolateral COP velocity at posttest, F(1,30) = 10.523, P < 0.01. In the weight transition phase, both groups had higher mediolateral COP velocity at posttest, F(1,30) = 30.636, P < 0.01. In the locomotor phase, in both groups, the anteroposterior COP velocity was increased significantly at posttest compared with pretest, F(1,30) = 5.883, P = 0.02. Both groups demonstrated improvements in the anticipatory and execution phases of GI. Since no between-group difference was found, it can be interpreted that the anodal tDCS applied over the SMA has no added value over sham stimulation. Balance training is beneficial for persons with CAI and can improve the anticipation and execution phases of GI without the aid of brain stimulation.

Influences of cognitive load on center of pressure trajectory of young male adults with excess weight during gait initiation.

Introduction: Falls and fall-related injuries in young male adults with excess weight are closely related to an increased cognitive load. Previous research mainly focuses on analyzing the postural control status of these populations performing cognitive tasks while stabilized walking progress but overlooked a specific period of walking known as gait initiation (GI). It is yet unknown the influences of cognitive load on this population's postural control status during GI. Objective: This study aimed to determine the influences of cognitive load on the center of pressure (CoP) trajectory of young male adults with excess weight during GI. Design: A controlled laboratory study. Methods: Thirty-six male undergraduate students were recruited and divided into normal-weight, overweight, and obese groups based on their body mass index (BMI). Participants' CoP parameters during GI under single and dual-task conditions were collected by two force platforms. A mixed ANOVA was utilized to detect significant differences. Results: Compared with the normal-weight group, the obese group showed significant changes in the duration and CoP parameters during sub-phases of GI, mainly reflecting prolonged duration, increased CoP path length, higher mediolateral CoP displacement amplitude, and decreased velocity of anteroposterior CoP displacement. During GI with 1-back task, significantly increased mediolateral CoP displacement amplitude occurred in the obese group. During GI with 2-back task, the obese group had increased CoP path length, higher mediolateral CoP displacement amplitude, as well as a decreased velocity of CoP displacement. Conclusion: Based on the changes in CoP parameters during GI with cognitive tasks, young male adults with excess weight, mainly obese ones, have compromised postural stability. During GI with a difficult cognitive task, obese young male adults are more susceptible to deterioration in their lateral postural balance. These findings indicate that the increased cognitive load could exacerbate obese young male adults' postural control difficulty during GI under dual-task conditions, putting them at a higher risk of experiencing incidents of falls. Based on these findings, we offer suggestions for therapists to intervene with these young male adults to ensure their safety of GI.

Subthreshold white noise vibration alters trembling sway in older adults

BackgroundSomatosensory deficit is a significant contributor to falls in older adults. Stochastic resonance has shown promise in recent studies of somatosensation-based balance disorders, improving many measures of stability both inside and outside of the clinic. However, our understanding of this effect from a physiological perspective is poorly understood. Therefore, the primary goal of this study is to explore the influence of subthreshold vibratory stimulation on sway under the rambling-trembling framework. Methods10 Healthy older adults (60–65 years) volunteered to participate in this study. Each participant underwent two randomized testing sessions on separate days, one experimental and one placebo. During each session, the participants' baseline sway was captured during one 90-s quiet standing trial. Their sensation threshold was then captured using a custom vibratory mat and 4–2-1 vibration perception threshold test. Finally, participants completed another 90-s quiet standing trial while the vibratory mat vibrated at 90% of their measured threshold (if experimental) or with the mat off (if placebo). While they completed these trials, an AMTI force plate collected force and moment data in the anteroposterior (AP) and mediolateral (ML), from which the center of pressure (COP), rambling (RM), and trembling (TR) time series were calculated. From each of these time series, range, variability (root-mean-square), and predictability (sample entropy) were extracted. One-tailed paired t-tests were used to compare baseline and during-vibration measures. ResultsNo significant differences were found during the placebo session. For the experimental session, significant increases were found in AP TR range, ML TR RMS, AP COP predictability, and AP & ML TR predictability. The TR time series was particularly sensitive to vibration, suggesting a strong influence on peripheral/spinal mechanisms of postural control. SignificanceThough it is unclear whether observed effects are indicative of “improvements” or not, it does suggest that there was a measurable effect of subthreshold vibration on sway. This knowledge should be utilized in future studies of stochastic resonance, potentially acting as a mode of customization, tailoring vibration location, duration, magnitude, and frequency content to achieve the desired effect. One day, this work may aid in our ability to treat somatosensation-based balance deficits, ultimately reducing the incidence and severity of falls in older adults.

Comparison of Dynamic Postural Control in Youth Athletes with and without a History of Lateral Ankle Sprain : A Case-control Study

PURPOSE The purpose of this study was to compare the dynamic postural control of youth athletes with and without a history of lateral ankle sprains. METHODS Twenty-eight youth athletes (14 lateral ankle sprain, 14 healthy control) participated in this study. All participants answered the Foot and Ankle Ability Measure questionnaire and were subject to the Star Excursion Balance Test (SEBT) for dynamic postural control evaluation to collect the joint angles of the lower extremity, a center of pressure (COP) path, and COP velocity. Independent sample t-test or Mann-Whitney U-test were performed to analyze the difference between the groups. RESULTS The lateral ankle sprain group (LAS) was found to have a long experience in participating in sports, and low Foot and Ankle Ability Measure scores were identified when compared to the healthy control (CON; p&lt;0.05). LAS was observed with a short reach distance, less hip flexion, and dorsiflexion angles during the anterior direction of SEBT when compared to CON (p&lt;0.05). Furthermore, LAS showed a slower anteroposterior and mediolateral center of pressure velocities in the posteromedial aspect of SEBT and a slower anteroposterior COP velocity in the posterolateral aspect of SEBT when compared to that of CON (p&lt;0.05). There were no differences between the groups with respect to the other variables (p&gt;0.05). CONCLUSIONS Based on these results, decreased anterior reach distance of SEBT may be affected by changing the dynamic posture control strategy of the lower extremity joint on the sagittal plane in LAS.

Perturbation-Based Balance Exercise Using a Wearable Device to Improve Reactive Postural Control.

Reactive postural control is an important component of the balance function for fall prevention. Perturbation-based balance exercises improve reactive postural control; however, these exercises require large, complex instruments and expert medical guidance. This study investigates the effects of unexpected perturbation-based balance exercises using a wearable balance exercise device (WBED) on reactive postural control. Eighteen healthy adult males participated in this study. Participants were assigned to the WBED and Sham groups. In the intervention session, participants in the WBED group randomly underwent unexpected perturbation in the mediolateral direction, while the Sham group performed the same exercises without perturbation. Before and after the intervention session, all participants underwent evaluation of reactive balance function using air cylinders. Peak displacement (D), time at peak displacement (T), peak velocity (V), and root mean square (RMS) of center of pressure (COP) data were measured. For mediolateral and anteroposterior COP (COPML and COP[Formula: see text]), the main effects of group and time factors (pre/post) were investigated through the analysis of variance for split-plot factorial design. In the WBED group, the D-COPML and V-COPML of the post-test significantly decreased compared to those of the pre-test (p = 0.017 and p = 0.003, respectively). Furthermore, the D-COPAP and RMSAP of the post-test significantly decreased compared to those of the pre-test (p = 0.036 and p = 0.015, respectively). This study proved that the perturbation-based balance exercise using WBED immediately improved reactive postural control. Therefore, wearable exercise devices, such as WBED, may contribute to the prevention of falls and fall-related injuries.

Estimating Ground Reaction Force and Center of Pressure Using Low-Cost Wearable Devices.

Ambulatory monitoring of ground reaction force (GRF) and center of pressure (CoP) could improve management of health conditions that impair mobility. Insoles instrumented with force-sensitive resistors (FSRs) are an unobtrusive, low-cost, and low-power technology for sampling GRF and CoP in real-world environments. However, FSRs have variable response characteristics that complicate estimation of GRF and CoP. This study introduces a unique data analytic pipeline that enables accurate estimation of GRF and CoP despite relatively inaccurate FSR responses. This paper also investigates whether inclusion of a complementary knee angle sensor improves estimation accuracy. Seventeen healthy subjects were equipped with an insole instrumented with six FSRs and a string-based knee angle sensor. Subjects walked in a straight line at self-selected slow, preferred, and fast speeds over an in-ground force platform. Twenty repetitions were performed for each speed. Supervised machine learning models estimated weight-normalized GRF and shoe size-normalized CoP, which were re-scaled to obtain GRF and CoP. Anteroposterior GRF, Vertical GRF, and Anteroposterior CoP were estimated with a normalized root mean square error (NRMSE) of less than 5%. Mediolateral GRF and CoP were estimated with an NRMSE of 8.1% and 6.4%, respectively. Knee angle-related features slightly improved GRF estimates. Normalized models accurately estimated GRF and CoP despite deficiencies in FSR data. Ambulatory use of the proposed system could enable objective, longitudinal monitoring of severity and progression for a variety of health conditions.

Balance control in unstable sitting in individuals with an acute episode of low back pain

BackgroundLow back pain (LBP) is associated with altered postural control, mostly observed at later stages in the LBP trajectory. It is unclear whether postural control differs in the acute phase of LBP. Research questionIs postural control different in the acute phase of LBP (<2 weeks) and do differences depend on pain intensity, psychological features and/or availability of vision to control posture? MethodsCross-sectional study design. An unstable sitting paradigm (to reduce the contribution of the legs) assessed postural control of participants with acute LBP (n = 133) and pain-free controls (n = 74). Centre of pressure (CoP) reflected seat movements. Participants balanced with eyes closed, open, or with visual feedback of the anteroposterior CoP position. Balance performance was expressed by CoP displacement and velocity, and stabilogram diffusion analysis. Generalised estimating equations (GEEs) including body mass index, sex, and safety bar touch, tested differences between groups and between balance conditions. Separate GEEs were used to model performance measures and bar touch (yes/no) including pain intensity, disability and psychological features. ResultsCoP displacement and critical point coordinates (time and distance where CoP diffusion rate or spread slows) were larger in LBP than pain-free controls independent of balance condition. Long-term diffusion rate was greater in LBP than controls with eyes closed. CoP velocity measures (RMS, short term diffusion rate) were not different between groups. Pain intensity and psychological features were not linearly related to balance performance in participants with acute LBP. Higher pain catastrophizing was associated with touching the safety bar. SignificancePostural control differs in acute LBP than pain-free controls. Findings might be explained by altered sensory processing, lesser ability to reweight proprioceptive information and/or less accurate trunk muscle control. Although not linearly related to pain-intensity or psychological features in the acute stage, reduced balance performance could potentially have impact on LBP recovery.

Pelvic Floor Muscle Strength and the Postural Balance in Middle-Aged Women: A Pilot Study

Aim To investigate if pelvic floor muscles’ (PFMs’) strength is associated with postural balance in middle-aged women. Methods The participants were 22 middle-aged women (age: 57 ± 6 years). They completed a clinical and urogynecological evaluation, PFMs’ strength testing using a perineometer, and balance testing on a force platform. The balance variables analyzed were anteroposterior (AP) and side-to-side (SS) center of pressure (COP) displacement; 95% elliptical COP area (cm2), AP and SS COP displacement median frequency. Results PFMs’ strength was moderately correlated with SS COP displacement and with AP COP median frequency in semi-tandem. Age and educational level affected the relationship between PFMs’ strength and balance. Conclusion PFMs’ strength had the strongest associations with SS COP displacement in eyes-open semi-tandem and AP COP median frequency in eyes-closed semi-tandem. Thus, these results allow us to conclude that there may be some relationship between pelvic floor muscle strength and postural balance in middle-aged women.

Effects of load carrying techniques on gait parameters, dynamic balance, and physiological parameters during a manual material handling task

PurposeSince construction workers often need to carry various types of loads in their daily routine, they are at risk of sustaining musculoskeletal injuries. Additionally, carrying a load during walking may disturb their walking balance and lead to fall injuries among construction workers. Different load carrying techniques may also cause different extents of physical exertion. Therefore, the purpose of this paper is to examine the effects of different load-carrying techniques on gait parameters, dynamic balance, and physiological parameters in asymptomatic individuals on both stable and unstable surfaces.Design/methodology/approachFifteen asymptomatic male participants (mean age: 31.5 ± 2.6 years) walked along an 8-m walkway on flat and foam surfaces with and without a load thrice using three different techniques (e.g. load carriage on the head, on the dominant shoulder, and in both hands). Temporal gait parameters (e.g. gait speed, cadence, and double support time), gait symmetry (e.g. step time, stance time, and swing time symmetry), and dynamic balance parameters [e.g. anteroposterior and mediolateral center of pressure (CoP) displacement, and CoP velocity] were evaluated. Additionally, the heart rate (HR) and electrodermal activity (EDA) was assessed to estimate physiological parameters.FindingsThe gait speed was significantly higher when the load was carried in both hands compared to other techniques (Hand load, 1.02 ms vs Head load, 0.82 ms vs Shoulder load, 0.78 ms). Stride frequency was significantly decreased during load carrying on the head than the load in both hands (46.5 vs 51.7 strides/m). Step, stance, and swing time symmetry were significantly poorer during load carrying on the shoulder than the load in both hands (Step time symmetry ration, 1.10 vs 1.04; Stance time symmetry ratio, 1.11 vs 1.05; Swing time symmetry ratio, 1.11 vs 1.04). The anteroposterior (Shoulder load, 17.47 mm vs Head load, 21.10 mm vs Hand load, −5.10 mm) and mediolateral CoP displacements (Shoulder load, −0.57 mm vs Head load, −1.53 mm vs Hand load, −3.37 ms) significantly increased during load carrying on the shoulder or head compared to a load in both hands. The HR (Head load, 85.2 beats/m vs Shoulder load, 77.5 beats/m vs No load, 69.5 beats/m) and EDA (Hand load, 14.0 µS vs Head load, 14.3 µS vs Shoulder load, 14.1 µS vs No load, 9.0 µS) were significantly larger during load carrying than no load.Research limitations/implicationsThe findings suggest that carrying loads in both hands yields better gait symmetry and dynamic balance than carrying loads on the dominant shoulder or head. Construction managers/instructors should recommend construction workers to carry loads in both hands to improve their gait symmetry and dynamic balance and to lower their risk of falls.Practical implicationsThe potential changes in gait and balance parameters during various load carrying methods will aid the assessment of fall risk in construction workers during loaded walking. Wearable insole sensors that monitor gait and balance in real-time would enable safety managers to identify workers who are at risk of falling during load carriage due to various reasons (e.g. physical exertion, improper carrying techniques, fatigue). Such technology can also empower them to take the necessary steps to prevent falls.Originality/valueThis is the first study to use wearable insole sensors and a photoplethysmography device to assess the impacts of various load carrying approaches on gait parameters, dynamic balance, and physiological measures (i.e. HR and EDA) while walking on stable and unstable terrains.

Biomechanical characteristics of handstand walking initiation

BackgroundThe initiation in human locomotion is defined as the transition between upright stance and steady-state gait. While past literature abundantly investigated the initiation in bipedal gait, the initiation of handstand walking remains unexplored. Research questionThe current study aims to characterise the centre of pressure (CoP) and centre of mass (CoM) trajectory of handstand walking initiation as well as the spatiotemporal and kinematic parameters and balance strategy of this task. Also, the study examined the CoP trajectory similarity within- and between-participants using a coefficient of multiple correlation analysis. MethodsNineteen gymnasts took part in this study. Handstand walking initiation trials were recorded using force plates and a stereophotogrammetric system. CoM and CoP trajectories were analysed during the Baseline, Preparation and Execution phases of the motor task. ResultsWe found that to successfully perform the handstand walking initiation, a shift of the CoM forward and towards the stance hand is required as a result of a lateral and posterior CoP shift. All participants performed a similar CoP pattern in the mediolateral direction, whereas two anteroposterior CoP displacement strategies were identified across participants based on different timing execution of posterior CoP shift. While CoP and CoM kinematic differences were identified during the Preparation Phase due to the adopted strategy, no significant difference was found in the Execution Phase for the spatiotemporal and kinematic characteristics. SignificanceA better understanding of the required CoP/CoM patterns and balance control provides the basis for further neuromechanics research on the topic and could contribute to individualise training protocols to improve the learning of the task.

The Effects of Static Stretching On Dynamic Postural Control During Maximum Forward Leaning Task

The purpose of this study was to determine how the application of static stretching to ankle plantar flexors affects postural control during maximum forward leaning. Twenty-six volunteer males (age 21.4 ± 1.2 years) were randomly assigned to stretching and control conditions. Participants conducted 5-min stretching on a stretch board for the stretching condition and were kept standing for 6-min for the control condition. Before and after intervention, the range of motion (ROM) at ankle dorsiflexion and the center of pressure (COP) excursion during maximal forward leaning were determined. Mean anteroposterior COP position, COP velocity and COP areas were calculated to compare the change in postural control. After stretching, ROM was significantly increased. During maximal forward leaning after stretching, both COP position and velocity showed significant increases compared to before stretching. Moreover, COP position and velocity in the stretching condition were significantly higher than in the control condition after stretching. No significant differences were found in COP area before and after stretching. Five-minute stretching increased not only ROM but also the anterior limit of stability while maintaining posture and led to faster COP shift than before stretching. These results indicate that static stretching would improve dynamic postural control as well.

The relationship between attention and static balance disturbance in patients with Parkinson’s disease

Balance disturbance is one of the main complications of the Parkinson's disease (PD). As studies have shown that impairments in some cognitive processescan lead to balance problems, we investigated the relationship between focused and divided attention and static balance in patients with PD and a healthycontrol group. We included 111 patients with PD (M age = 49.41, SD = 6.33 years) and 142 healthy individuals (M age = 50.62, SD = 6.07 years). All participants wereevaluated with the Trails Making Test A and B (TMT), and all participants' balance was evaluated with a Wii Balance Board, from which we measured theantero-posterior (AP), medio-lateral (ML), and total center of pressure (COP) velocity. We compared the two groups in terms of TMT-A, TMT-B, and COPvelocity tests in both eyes-open and eyes-closed conditions with independent t-tests, and we calculated Pearson's correlation coefficients between thebalance board-derived outcomes and the TMT scores. The two groups differed significantly on TMT-A and TMT-B scores, in total and ML COP velocity in both eyes-closed and eyes-open conditions, and in APCOP velocity only in eyes-open condition. Among patients with PD, TMT-A and TMT-B scores were positively correlated with total, ML, and AP COPvelocity, in both eyes-open and eyes-closed conditions. Associated attention deficits may be among the causes of balance disturbances in patients with PD, though both attention and balance may have a commonroot in brain circuitry.

Oscilação do centro de pressão, equilíbrio e mobilidade funcional em pacientes com úlceras venosas crônicas

Introdução: Sabe-se que o equilíbrio é reduzido no envelhecimento, no entanto, as alterações do equilíbrio em portadores de úlceras venosas é pouco conhecido. Objetivo: Avaliar a oscilação do centro de pressão, mobilidade funcional e equilíbrio de portadores de úlcera venosa em membros inferiores. Materiais e Métodos: Trata-se de um estudo transversal. Participaram do estudo 8 pacientes portadores de úlceras venosas crônicas (66,87 ± 8,82 anos) de ambos os sexos, que apresentavam úlcera venosa unilateral ou bilateral. O equilíbrio foi avaliado pela escala de equilíbrio de Berg, a mobilidade funcional pelo Timed Up and Go e a oscilação do centro de pressão (COP) pela plataforma de baropodometria e estabilometria. Resultados: Observou-se risco de quedas em pacientes com feridas venosas em ambos os membros inferiores enquanto ausência de risco de quedas foi observada em pacientes com úlcera venosa crônica unilateral, maior oscilação do COP ântero-posterior em comparação à médio lateral na condição de olhos abertos e fechados em pacientes com úlcera venosa crônica unilateral, enquanto percebeu-se maior oscilação do COP ântero-posterior em comparação à médio lateral apenas na condição de olhos fechados no grupo de pacientes com feridas nos dois membros inferiores. Conclusão: Esses achados apontam para a necessidade de se repensar as intervenções direcionadas para pacientes portadores de ulceras venosas crônicas, com utilização de estratégias empregadas para promover a cicatrização da ferida e a melhora do equilíbrio e reduzir riscos de quedas, proporcionando o cuidado integral da saúde desses indivíduos.

신발의 뒤꿈치 형태가 보행 시 충격과 생체역학적 특성에 미치는 영향

Objective: The purpose of this study was to investigate the effects of a curved shoe design of the heel of a shoe on the impact variables, ankle joint angle, and COP (center of pressure) during walking.BRBRBackground: Shoe design is one of important characteristics in the development of walking shoes as it has to be considered for the mechanism of human movement. BRBRMethod: Twenty healthy male adults (age: 23.6±2.9 years, body mass: 71.0±8.7kg, height: 175.8±5.0cm) participated in the study. The data was collected using eight infrared cameras during walking at a speed of 1.3m/s and 1.7m/s on an instrumented treadmill.BRBRResults: The impulse and peak VGRF (vertical ground reaction force) were statistically smaller for the RHS and RLHS compared with the NS during walking of 1.3m/s & 1.7m/s (p .05). The ankle plantarflexion angle at toe off, the ROM (range of motion) of dorsi-plantarflexion, and ROM of inversion-eversion were statistically smaller for the RHS and RLHS compared with the NS during walking of 1.7m/s (p .05). The antero-posterior COP range and jerk were statistically smaller for the RHS and RLHS compared with the NS during walking of 1.7m/s (p .05).BRBRConclusion: It is concluded that RLHS is slightly effective in reducing shocks, RLHS and RHS help walk smoothly and naturally compared to NS, and RLHS improves the stability of the ankle joints compared to NS, and RLHS during walking. BRBRApplication: The findings would be helpful when developing the walking shoes with biomechanical functions.

The Characteristics of Feet Center of Pressure Trajectory during Quiet Standing

To investigate the level of bilateral symmetry or asymmetry between right and left foot center of pressure (COP) trajectory in the mediolateral and anteroposterior directions, this study involved 102 participants (54 females and 48 males). Ground reaction forces were measured using two Kistler force plates during two 45-s quiet standing trials. Comparisons of COP trajectory were performed by correlation and scatter plot analysis. Strong and very strong positive correlations (from 0.6 to 1.0) were observed between right and left foot anteroposterior COP displacement trajectory in 91 participants; 11 individuals presented weak or negative correlations. In the mediolateral direction, moderate and strong negative correlations (from −0.5 to −1.0) were observed in 69 participants, weak negative or weak positive correlations in 30 individuals, and three showed strong positive correlations (0.6 to 1.0). Additional investigation is warranted to compare COP trajectories between asymptotic individuals as assessed herein (to determine normative data) and those with foot or leg symptoms to better understand the causes of COP asymmetry and aid clinicians with the diagnosis of posture-related pathologies.

Head and neck extension more than 30° may disturb standing balance in healthy older adults

Although there is clinical evidence of postural instability at extreme angles of head extension, the effects of lower angles on balance have been not investigated. This study aimed to investigate the effects of different head and neck extension angles on standing balance in older adults, and to determine the critical angle of instability. Twenty-eight healthy older adults were tested at 0°, 20°, 30° and 40° head and neck extension. The center of pressure (COP) parameters were recorded with a force plate. Significant differences were observed between 30° and 40° compared to 0° in anteroposterior and mediolateral COP displacement and total COP velocity, and between 40° and 0° in mediolateral COP velocity. Head and neck extension at 30° was the critical angle associated with the appearance of instability, and this value should be considered in the ergonomic design of work and living spaces, exercise programming and daily activities in older adults.

Changes in center of pressure velocities during obstacle crossing one year after bariatric surgery

Adults with obesity have atypical gait with poor balance leading to an increase in fall risk. After massive weight loss, their gait improves. However, we know little about changes in postural stability after massive weight loss. The present study aimed to examine how massive weight loss after Roux-en-Y bariatric surgery affected adjustments in center of pressure (COP) velocities during flat ground walking and obstacle crossing. Before and one-year post-bariatric surgery, nineteen female adults walked under four conditions: baseline walking on flat ground and obstacle crossing with three different obstacle heights for a total of 20 trials. COP data were obtained from raw pressure time series data extracted from a gait carpet. Massive weight loss increased anteroposterior COP velocities under the midfoot of both trailing and leading legs (ps<.01) and decreased mediolateral COP velocities under the forefoot of trailing leg (p < .05). Decreased BMI from pre- to post-surgery was correlated with an increase in anterior-posterior and decrease in medial-lateral COP velocities and with increased velocity (ps<.05). Massive weight loss not only improved gait but also facilitated effective balance control strategies. Examining how massive weight loss affects adjustments in COP velocity may help create ways to better understand why individuals with obesity have atypical gait with poor balance and how we can facilitate participation in physical activities.

Enhancement of posture sway with backpack weight carrying by eye closure and reduced support polygon surface

ObjectiveIn a previous study (Hanan and Jammes, Obesity Medicine, 2019) we showed that backpack carrying mimicking obesity elicited marked changes in postural sway during upright standing. Our objective was to study, separately or combined, the postural effect of weight carrying, eye closure, and/or reduced support polygon when healthy people stayed upright for 10 min. MethodsYoung adults had to maintain their eyes open or closed when standing upright for 10 min with or without added backpack weights. The postural effects of a 30–35% reduction of the support polygon (directed feet position) were also examined. We measured the surface and length of displacement of the centre of pressure (CoP), and amplitude and velocity of changes of its deviations in mediolateral and anteroposterior directions. ResultsEye closure during weight carrying in the condition of spontaneous feet placement significantly increased the CoP length and surface and the anteroposterior and mediolateral CoP deviations. Reduction of the support polygon (directed position) during weight carrying significantly increased both the CoP surface and the mediolateral CoP deviation. ConclusionAltered postural control with backpack weight carrying is augmented by reduction of the support polygon and the suppression of visual information. These conditions should be avoided in obese subjects. Clinical trial registrationCPP Sud Mediterranée 1, September 9th 2015, N° 2014-AO1969-38.

The Location of the Center of Pressure on the Starting Block Is Related to Sprint Start Performance.

Force application locations [i.e., center of pressure (COP)] on the block surface are not necessarily the same for individuals even if the same block locations and angles are used. The purpose of this study was to examine the association of block clearance performance with COP location on the starting block surface. Twenty-one male sprinters performed 60 m sprints from the starting blocks, during which the ground reaction forces (GRFs) on the starting blocks were recorded using two force platforms. Using a previously validated method, changes in COP location on the block surface during the block clearance for each block was calculated from the marker coordinates on the block surface, GRF signals, and moment data around the center of the force platform at the ground level. Moreover, average horizontal external power (AHEP), which was considered the key performance criterion, was computed. Statistical parametric mapping (SPM) 1D linear regressions were used to test relationships between AHEP and COP location curves in the anteroposterior and vertical directions. The COP for both legs moved backward and upward (0.042 and 0.042 m for the front block and 0.030 and 0.034 m for the rear block) at first and then forward and downward (0.113 and 0.094 m for the front block and 0.095 and 0.087 m for the rear block) toward the toe-off. Based on SPM results, AHEP was correlated with front block anteroposterior and vertical COP locations from 12.9 to 20.8% and from 10.4 to 22.2% of the force production phase, respectively, while it was correlated with rear block vertical COP location from 31.9 to 37.4% of the force production phase. In conclusion, the current results demonstrate that, regardless of the starting block location and angle, better sprint start performance is accomplished with a higher and more to the rear COP on the starting block surface, when COP is located close to heel during the middle phase of the block clearance. The fact that the COP location is related to sprint start performance will be useful for sprinters and coaches who intend to improve sprint start performance.

Mimicking obesity and pregnancy by adding load mass elicits minor postural oscillations compared to backpack weight carrying.

Structured abstract Objective An excess load mass of anterior or antero-posterior body part is encountered in pregnancy and android obesity, or gynoid obesity, respectively, whereas occupational backpack weight carrying occurs in soldiers, firefighters and school children. We questioned the consequences of different placements of added loads (backpack, anterior or antero-posterior, i.e., around the trunk) on the postural sway during upright standing. Methods Thirty six young subjects with normal body weight were examined. Cast iron disks were introduced into the backpack and/or the ventral pockets of a waistcoat (total added load = 30% of body weight). A baropodometric platform measured oscillations of the centre of pressure (CoP) at the end of a 10-min period of upright standing in double limb stance in control condition (no weight carrying) and at the end of each 10-min weight carrying session. A 10-min rest period elapsed between two consecutive carrying sessions. Results Backpack carrying elicited the highest changes in postural sway, increasing the CoP surface and length, the velocity of anteroposterior and mediolateral deviations and the magnitude of mediolateral deviations. On the other hand, anterior load mass placement only increased the velocity of changes in the anteroposterior CoP deviation and antero-posterior weight carrying solely increased the mediolateral CoP deviation. Conclusion Added load mass mimicking pregnancy, android or gynoid obesity elicits discrete changes in postural control compared to backpack weight carrying which may accentuate the risk of fall during occupational activities. Clinical trial registration CPP Sud Mediterranee 1, September 9th 2015, N° 2014-AO1969-38.