The purpose of this study was to assess trunk muscle fatigue in seated handicraft tasks using surface
electromyography (sEMG) and visual analogue scale (VAS) ratings for trunk discomfort, and to assess the
relationship of these responses. Twenty-three participants were randomly assigned to assumed crossed-leg and
heel sitting postures for 30 min. Normalised median frequency (NMF) slopes for lumbar multifidus (LM) and
internal oblique (IO) muscles and VAS ratings were recorded. Results revealed that the crossed-leg posture produced
significantly steeper NMF slopes for both sides of the LM and IO muscles than heel sitting. Greater VAS
ratings were found in crossed-leg sitting posture than the heel sitting posture. The NMF slopes and the VAS ratings
had significant negative correlations for both postures. Findings support heel sitting in handicraft tasks over
crossed-leg sitting due to greater trunk muscle fatigue and discomfort during the latter posture. Results support
VAS ratings as a complementary method to sEMG for identifying trunk muscle fatigue.
Practitioner Summary: Trunk muscle fatigue in handicraft work is a potential risk for low back pain. Based on
EMG and discomfort analyses, heel sitting is preferred to crossed-leg posture. Discomfort ratings are consistent
with EMG measures in identifying trunk muscle fatigue in such postures.
Keywords: trunk muscle fatigue; body discomfort; surface electromyography; visual analogue scale; normalised
median frequency slope