title: Relationship between force fluctuation in the plantar flexor and sustainable time for single-leg standing.
abstract: The purpose of this study was to investigate the relationships between force fluctuation during isometric plantar flexion and the sustainable time for single-leg standing. Fourteen healthy males (21+/-1 years) performed unilateral (preferred leg) force matching tasks and single-leg quiet standing. Force matching tasks were performed to maintain isometric plantar flexion for 15 s at levels corresponding to 10% and 20% maximal voluntary contraction (MVC) with the visual feedback of force. Force fluctuation during force matching tasks was quantified as the standard deviation of force. Sustainable time for single-leg quiet standing was performed to maintain a single-leg quiet standing barefoot on a platform using the preferred leg with their eyes closed. Force fluctuation was significantly greater in 20% MVC task compared to 10% MVC task. The sustainable time for single-leg quiet standing was strongly correlated with force fluctuation in 20% MVC task (r=-0.56, p=0.04). However, it was not related to force fluctuation in 10% MVC task (r=0.19, p=0.52) or MVC value (r=0.13, p=0.65). These results suggest that a specificity of contraction intensity is observed between force steadiness and the posture stability during single-leg quiet standing; force steadiness during 20% MVC plantar flexion is one of the important components for posture stability during single-leg quiet standing.
authors.affiliation: Graduate School of Human Development and Environment, Division of Human Environmental Science, Kobe University, Nada-ku, Kobe, Japan. 062d844d@stu.kobe-u.ac.jp
authors.forename: Kazushige
authors.initials: K
authors.lastname: Oshita
authors.forename: Sumio
authors.initials: S
authors.lastname: Yano
mesh_terms: D001696:Biomechanical Phenomena; D005528:Foot / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult