Showing papers by "Stephen D. Perry published in 2021"
TL;DR: In this article, the authors investigated the effect of pre-perturbation variability on stability and found that increased step width variability was neither beneficial nor detrimental to stability, however, the increased variability in medio-lateral foot placement suggests that participants adopted an exploratory strategy in anticipation of a perturbation.
9 citations
TL;DR: In this article, the authors investigate motor output changes from enhanced tactile feedback during perturbed gait termination, and find that the added tactile feedback under the plantar surface of the foot increases the ability to generate an earlier muscle response, consequently improving response ability to an unexpected platform perturbation.
Abstract: Purpose/aim of the study: Generation of smooth movement relies on the central nervous system (CNS) having information from the visual, vestibular and somatosensory systems to effectively execute motor behaviour. Recently, cutaneous afferent inputs have been linked to lower leg motorneuron pools, resulting in a growing interest of adding texture to the plantar foot sole interface as a novel method to facilitate cutaneous feedback. The aim of this study was to characterize the changes in magnitude and temporal organization of muscle activity, and to investigate motor output changes from enhanced tactile feedback during perturbed gait termination.Materials and methods: Thirty young adults experienced an unpredictable platform perturbation when completing planned gait termination. The study manipulated two experimental variables: 1) direction of platform tilt (anterior, posterior, medial, lateral), and 2) foot sensory facilitation (non-facilitated, facilitated). Upper and lower leg EMG onset, cessation time and integrated EMG (iEMG) were measured in addition to common gait parameters (walking velocity, step length, step width).Results: Gait termination over a textured surface resulted in significantly earlier upper leg EMG onset times and modified iEMG of rectus femoris, vastus medialis and biceps femoris muscles.Conclusions: Results of this study suggest that the addition of cutaneous feedback under the plantar-surface of the foot increases the ability to generate an earlier muscle response, consequently improving response ability to an unexpected perturbation. Secondly, enhanced tactile feedback appears to inform the CNS of the magnitude of the threat to the balance control system, providing additional insight into how the CNS uses enhanced tactile feedback during a gait termination task.
2 citations
TL;DR: In this paper, the authors determine the between-and within-session test-retest reliabilities of various force plate-derived measures of reactive stepping, such as step onset, foot-off, swing, and restabilization times.
1 citations
TL;DR: In this paper, the role of the transverse head of the adductor hallucis (AddH-T) muscle during walking was investigated using fine-wire EMG during locomotion.
TL;DR: In this article, the relationship between lower limb muscle strength and explosive force with force plate-derived timing measures of reactive stepping was investigated, and it was shown that improving function of specific muscles associated with reactive stepping may improve features of reactive balance control.
Abstract: Reactive stepping is one of the only strategies that can lead to successful stabilization following a large challenge to balance. Improving function of specific muscles associated with reactive stepping may improve features of reactive balance control. Accordingly, this study aimed to determine the relationship between lower limb muscle strength and explosive force with force plate-derived timing measures of reactive stepping. Nineteen young, healthy adults (27.6 ± 3.0 years of age; 10 women: 9 men) responded to 6 perturbations (~13-15% of body weight) using an anterior lean-and-release system (causing a forward fall), where they were instructed to recover balance in as few steps as possible. Foot-off, swing, and restabilization times were estimated from force plates. Peak isokinetic torque, isometric torque, and explosive force of the knee extensors/flexors and plantar/dorsiflexors were measured using isokinetic dynamometry. Correlations were run based on a priori hypotheses and corrected for the number of comparisons (Bonferroni) for each variable. Knee extensor explosive force was negatively correlated with swing time (r = -0.582, p = 0.009). Knee flexor peak isometric torque also showed a negative association with restabilization time (r = -0.459, p = 0.048), however this was not statistically significant after correcting for multiple comparisons. There was no significant relationship between foot-off time and knee or plantar flexor explosive force (p > 0.025). These findings suggest that there may be utility to identifying specific aspects of reactive step timing when studying the relationship between muscle strength and reactive balance control. Exercise training aimed at improving falls risk should consider targeting specific aspects of muscle strength depending on specific deficits in reactive stepping.