Effects of muscle fatigue on force coordination and performance in manipulation tasks
Date
2013
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
The effects of muscle fatigue on force coordination and task performance
during various handheld object manipulation tasks are explored. In both of the studies,
grip force (GF; normal force component acting at the digits-object contact area) and
load force (LF; tangential component that lifts and holds objects) were recorded prior
to and after a specific fatiguing protocol. In the first study, a fatiguing protocol was
applied with the aim of fatiguing both the distal (DAM; i.e., GF-producing) and the
proximal arm muscles (PAM; LF-producing) at an equal rate using an oscillatory
motion. Results revealed a marked fatigue-associated decrease in GF scaling (i.e., the
magnitude of GF relative to LF) and GF–LF coupling (correlation between GF and
LF), while task performance regarding the accuracy of exertion of the prescribed LF
profiles remained unaffected. In the second study, two distinct fatiguing protocols
were applied during different testing sessions in order to separately fatigue DAM and
PAM. The results revealed a deterioration of GF scaling, GF-LF coupling, and task
performance (i.e., the ability to exert a prescribed LF pattern) associated with DAM,
but not PAM fatigue. In conclusion, muscle fatigue both partly decouples GF from LF
and reduces the overall GF magnitude, which could potentially explain why hand-held
objects are more likely to drop when manipulated with fatigued muscles. The
unaffected task performance seen in the first study could be explained either by the
relatively low level of muscle forces required by the tested tasks, the moderate level of
the fatigue imposed, or both. Additionally, the observed selective effects of DAM and
PAM fatigue represent a novel finding deserving of further research.