Stable patterns of upper limb muscle activation in different conditions of human walking

Abstract

<p>Background: Arm swing during human gait is associated with contractions of upper limb muscles, which have been examined rarely.</p><p>Aim: This study aims to identify basic temporal patterns of upper limb muscle activation during walking conditions involving different modes of arm swing.</p><p>Method: Twenty volunteers were examined during (a) normal forward walking, (b) walking with immobilized arms, (c) walking while carrying loads in one or in both hands. Electromyographic (EMG) data were collected for the trapezius (TRAP), anterior (AD) and posterior deltoid (PD), biceps (BIC), triceps (TRI), latissimus dorsi (LD) and lumbar erector spinae (ES) muscles.</p><p>Results: Principal components analyses identified two basic patterns of muscle activation that remained stable across gait conditions. Some rhythmical EMG signals of arm and shoulder muscles (TRAP, PD, TRI, LD) persisted during walking with immobilized arms, indicating coupled activation of leg and arm muscles. Carrying a load in one hand resulted in stronger ipsilateral EMG activity (TRAP, AD, PD, BIC, TRI) than splitting the same load between both hands.</p><p>Interpretation: Although the amount of upper limb muscle activity varies markedly between different conditions of human walking (with/without arm sing; with/without load carriage), basic temporal activation patterns remain stable, indicating a common motor control strategy.</p><em><br clear="all" /> </em>

Activity of upper limb and trunk muscles during power walking

“…Natural arm swing is not a purely passive movement, but involves shortening and lengthening contractions of arm and shoulder muscles. 11,14,19 Arm swing improves gait stability and decreases angular momentum of the body about the vertical axis. 20,21,22 The deliberate accentuation of arm swing during power walking is known to augment energy expenditure.…”

“…More detailed information concerning electrode placement has been published elsewhere. 14 EMG signal amplitudes were normalized to the highest signal reached during a maximal voluntary contraction (% MVC) to account for variations of the absolute EMG voltages between different muscles and individuals 15 , which may be due to differences in skin conductance. Maximum voluntary contractions were therefore performed with each relevant muscle prior to the gait trials.…”