Between-limb Force Variability Relationships During Bilateral Isometric Contractions

Abstract

All steady muscle contractions contain small force fluctuations which have the potential to impact on the control of limb movement. This variability in force production is influenced by many factors including the intensity of the muscle contraction generating the force, the amount of feedback regarding task performance, and the normal ageing process. Whilst many activities incorporate the use of both hands, the majority of research studying variability of movement has only examined a single limb. This Thesis presents three experiments that examine (1) bilateral force variability relationships during a two-handed isometric task, (2) the influence of visual feedback on bilateral force variability relationships, and (3) age-related variability differences during a bilateral force task. Isometric index finger abduction force and first dorsal interosseous (FDI) activity were assessed simultaneously in each hand. In the first experiment, force variability in a single limb was examined when the opposite limb was engaged in a force generating task. Force variability and FDI activity were assessed in thirteen young healthy subjects at target forces from 5% to 60% MVC for the non- dominant limb (unilateral task), and again when the dominant limb was also generating a constant abduction force (bilateral task).