Article

The purpose of this study was to describe and examine the variations in
recruitment patterns of motor units (MUs) in biceps brachii (BB) through a range
of joint motion during dynamic eccentric and concentric contractions. Twelve
healthy participants (6 females, 6 males, age=30+/-8.5 years) performed
concentric and eccentric contractions with constant external loading at different
levels. Surface electromyography (EMG) and mechanomyography (MMG) were recorded
from BB. The EMGs and MMGs were decomposed into their intensities in
time-frequency space using a wavelet technique. The EMG and MMG spectra were then
compared using principal component analysis. Variations in total intensity, first
principal component (PCI), and the angle theta formed by first component (PCI)
and second component (PCII) loading scores were explained in terms of MU
recruitment patterns and elbow angles. Elbow angle had a significant effect on
dynamic concentric and eccentric contractions. The EMG total intensity was
greater for concentric than for eccentric contractions in the present study. MMG
total intensity, however, was lower during concentric than during eccentric
contractions. In addition, there was no significant difference in theta between
concentric and eccentric contractions for both EMG and MMG. Selective recruitment
of fast MUs from BB muscle during eccentric muscle contractions was not found in
the present study.
CI - Copyright (c) 2011 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS