Cross-sectional Study of Upper Trapezius Muscle Activity and Self-Reported Neck/Shoulder Pain

Abstract

The purpose of this cross-sectional study was to compare the observed associations between upper trapezius muscle activity, as estimated with several summary measures obtained from surface electromyography (EMG), and self-reported neck/shoulder pain among a sample of 231 manufacturing workers. EMG methods used in this study included mean root-mean-square amplitude, the amplitude probability distribution function (APDF), EMG gaps analysis, and clustered exposure variation analysis. The observed seven-day prevalence of neck/shoulder pain was 13.9%. Of the EMG summary measures, only the 90 th percentile of the APDF was significantly associated with symptoms, with crude and adjusted odds ratios of 2.57 (1.02–6.49) and 2.78 (1.07–7.21) per natural log unit, respectively. This study was largely inconclusive due to the similarity in the distributions of the summary measures between symptomatic and non-symptomatic participants, and explicit measures of posture and repetition may produce stronger associations with symptoms.