Effect of Massage of the Hamstring Muscles on Selected Electromyographic Characteristics of Biceps Femoris during Sub-maximal Isometric Contraction

Abstract

The aim of this study was to investigate whether a single massage of the hamstring muscles would alter selected electromyographic characteristics of biceps femoris during a sub-maximal isometric contraction. Eleven healthy young males participated in this crossover study. They were randomly assigned to two groups, receiving either a 15-minute hamstring muscle massage or a 15-minute prone rest. One week later they returned to receive the alternate intervention. Immediately pre- and post-intervention, participants were instructed to contract their muscles just sufficiently to maintain right knee flexion (5 degrees from full extension) for 30 seconds. Simultaneous to this contraction, surface electromyography (EMG) was used to record the electrical activity of right biceps femoris. Electromyograms were analyzed by calculating the averaged/integrated EMG (aEMG) and median frequency (MF) for each of 14 one-second windows, sampled every two seconds throughout the 30-second contractions per participant. Mean values of aEMG and MF were calculated per participant (aEMGmean and MFmean), pre- and post-massage or rest intervention. Group means (n = 11) of aEMGmean and MFmean were then calculated and compared using a repeated measures analysis of variance (ANOVA) procedure (p < 0.05). Rates of change of aEMG and MF throughout each 30-second contraction were represented by their respective gradients as functions of time. These gradients were similarly compared pre- to post-intervention using repeated measures ANOVA (p < 0.05). For the young healthy males considered in this study, a single massage of the hamstring muscles had no statistically significant effects on selected electromyographic characteristics of biceps femoris during sub-maximal isometric contractions (p > 0.05).