Relationship between Ankle Plantar Flexor Force Steadiness and Postural Control

Abstract

When assessing the muscle condition, maximum muscle strength is often used. However, maximum voluntary strength is always not necessary for daily activities; rather, it is important to control low-intensity muscle contraction. One of the methods to assess the ability is force steadiness, which means force fluctuation during maintaining exerted force at submaximal target value. Force fluctuation is greater in aged people or patients with neurological disorders. Force steadiness during various intensities can be evaluated by setting the target force from low- to high-intensity force level. This article focuses on relationship between ankle plantar flexor force steadiness and postural control. In healthy young adults, force steadiness at 5% of maximum voluntary contraction torque (MVT) was related to postural sway on a stable platform, and force steadiness at 20% of MVT was related to postural sway on an unstable platform. While in older adults, force steadiness at any intensity was not related postural sway on a stable platform, but force steadiness at 20% of MVT was only related to postural sway on an unstable platform. These results suggested that different postural tasks are associated with force steadiness at different intensities.