Search results for "Terrestrial locomotion"
showing 10 items of 25 documents
In response to the article published by Fukaya et al., entitled: “Relationships between the center of pressure and the movements of the ankle and kne…
2017
International audience
Anticipatory Postural Adjustments During Gait Initiation in Stroke Patients
2019
Prior to gait initiation (GI), anticipatory postural adjustments (GI-APA) are activated in order to reorganize posture, favorably for gait. In healthy subjects, the center of pressure (CoP) is displaced backward during GI-APA, bilaterally by reducing soleus activities and activating the tibialis anterior (TA) muscles, and laterally in the direction of the leading leg, by activating hip abductors. In post-stroke hemiparetic patients, TA, soleus and hip abductor activities are impaired on the paretic side. Reduction in non-affected triceps surae activity can also be observed. These may result in a decreased ability to execute GI-APA and to generate propulsion forces during step execution. A s…
Time and frequency analysis of the static balance in young adults with Down syndrome
2010
The main objective of this study is to understand the differences in equilibrium control between normal subjects and those with Down syndrome. A total of 54 subjects participated voluntarily, divided into control group and Down syndrome group. The equilibrium of the subjects was tested under two conditions: bipedal support with eyes open and closed. The signals were analyzed in a time and frequency domain. The statistical parameters selected (i.e., RMS distance, mean velocity, mean frequency and sway area) to analyze the behavior of the center of pressures (CoP) are calculated employing the result of the combination of the time series data in both directions (i.e. resultant distance). In or…
Analyzing gastrocnemius EMG-activity and sway data from quiet and perturbed standing.
2007
In an experiment, we combined force plate measurements and surface EMG in studying quiet and perturbed standing, involving MS (Multiple sclerosis) and controls. The aim of this paper is to report the results thus obtained on the relation between filtered gastrocnemius (GA) EMG and the anterior-posterior center-of-pressure (A/P COP) coordinate. The main finding is the good correspondence between A/P COP and the filtered GA EMG in the low frequency range. The EMG envelope was calculated using a zero-lag filter. Combining this with time shifts around 250-350 ms produced a high correlation (85.5+/-8.4%) between the GA-EMG envelope and the A/P COP. This EMG-COP relation was closest when using a …
Postural Control Mechanisms in Healthy Adults in Sitting and Standing Positions
2015
This study explored differences in the center of pressure in healthy people in a sitting and standing position and with eyes open and closed. With this purpose, 32 healthy participants (16 men, 16 women; M age = 25.2 yr., SD = 10.0, range = 18–55) were measured with an extensiometric force plate. Using a two–way repeated-measures multivariate analysis of variance (MANOVA), the root mean square, velocity, range, and sway, in both visual conditions, had higher values in the standing task than in the sitting task. In the frequency domain, the low-frequency band had higher values during the standing task. For control mechanism variables, mean distance and time were greater when standing while …
Do equilibrium constraints modulate postural reaction when viewing imbalance?
2011
Abstract Action observation and action execution are tightly coupled on a neurophysiological and a behavioral level, such that visually perceiving an action can contaminate simultaneous and subsequent action execution. More specifically, observing a model in postural disequilibrium was shown to induce an increase in observers’ body sway. Here we reciprocally questioned the role of observers’ motor system in the contagion process by comparing participants’ body sway when watching displays of antero-posterior vs. lateral imbalance. Indeed, during upright standing, biomechanical constraints differ along the antero-posterior (A-P) and medio-lateral (M-L) axes; hence an impact of observers’ post…
Elderly adults delay proprioceptive reweighting during the anticipation of collision avoidance when standing.
2012
The ability to reweight visual and proprioceptive information is critical for maintaining postural stability in a dynamic environment. In this study, we examined whether visual anticipation of collision avoidance (AV) while standing could facilitate the down-weighting of altered proprioception in young and elderly adults. Twelve young (24.91 ± 6.44 years) and 12 elderly (74.8 ± 6.42 years) participants stood upright for 180 s under two task conditions: (a) quiet stance (QS) and (b) standing while anticipating virtual objects to be avoided. In order to disrupt the accuracy of proprioceptive input participants were exposed to bilateral Achilles tendon vibration during the middle 60 s of stand…
Ski Boots Do Not Impair Standing Balance by Restricting Ankle-Joint Mobility.
2018
Objective: This study was undertaken in order to provide new insight into sensorimotor control of posture when wearing high-shaft (HS) boots as ski boots. Background: 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. Method: Eighteen young healthy subjects took part in the experiment. Bilateral postural control was assessed on stable and unstable surfaces, while standing barefoot or weari…
The involvement of ankle muscles in maintaining balance in the upright posture is higher in elderly fallers
2016
International audience; The purpose of this study was to determine whether the mechanical contribution of ankle muscles in the upright stance differed among young adults (YA) (n = 10, age: similar to 24.3), elderly non-fallers (ENF) (n = 12, age: similar to 77.3) and elderly fallers (EF) (n = 20, age: similar to 80.7). Torque and electromyographic (EMG) activity were recorded on the triceps surae and tibialis anterior during maximum and submaximum contractions in the seated position. EMG activity was also recorded in subjects standing still. Plantar flexor (PF) and dorsal flexor (DF) torques generated in the upright posture were estimated from the torque-EMG relationship obtained during sub…
Balance control in aging: improvements in anticipatory postural adjustments and updating of internal models
2015
International audience; Postural stability of older subjects can be estimated during orthostatic equilibrium. However, dynamic equilibrium is also important to investigate risks of fall. It implies different interpretations of measures given by force plates. Same dependant variables (e.g. center of pressure displacement) cannot be interpreted the same ways depending of the type of equilibrium that is investigated. In particular, sways increases during dynamic equilibrium and before movement execution may reflect an improvement of feedforward control.