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

Abstract

Background:Â Arm swing during human gait is associated with contractions of upper limb muscles, which have been examined rarely.
 Aim: This study aims to identify basic temporal patterns of upper limb muscle activation during walking conditions involving different modes of arm swing.
 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.
 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.
 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.