Article

This study investigates how altering wrist posture influences the relationship
between the time and frequency measures of the electromyography (EMG) signal of
extensor digitorum communis (EDC) and flexor carpi ulnaris (FCU). Thirteen
participants exerted handgrip force related to maximum voluntary contraction
(MVC) in four tests: 20%MVC and 50%MVC in neutral wrist posture and 20%MVC in
full wrist flexion and extension. EMG measurements from EDC and FCU were used to
calculate normalized values of amplitude (nRMS) and mean and median frequency of
the power spectrum (nMPF, nMF). During muscle shortening (wrist flexion for FCU
and wrist extension for EDC) nRMS was approximately twofold higher than in
neutral posture for FCU and fourfold for EDC. All measures obtained at 20%MVC in
neutral posture were significantly different from 20%MVC in wrist flexion for FCU
and 20%MVC in wrist extension for EDC (p<0.05). Differences between 50%MVC and
20%MVC at neutral posture (nRMS) were significant for both muscles, although in
nMPF and nMF for EDC only. Muscle shortening changed the pattern of statistical
significance when the time and frequency domain measures were compared, whereas
muscle lengthening did not. It can be concluded that muscle shortening caused by
altering wrist posture influences the relationship between the time and frequency
measures in both muscles.
This suggests that in studies using EMG in different
wrist postures, changes in the relationship between the time and the frequency
measures should be considered.
CI - Copyright (c) 2012 Elsevier B.V. All rights reserved.

Langue : ANGLAIS