Electromyographic analysis of selected shoulder muscles during a rugby football tackle

Background: Epidemiological studies have shown that the incidence of shoulder injuries is increasing in rugby and the majority are related to the contact/tackle phase of play. However, no data currently exists that describes preparatory muscle activity during tackle. This information could aid in guiding training and rehabilitation, if available. The purpose of the study was to assess the sequence of onset of EMG activity of selected scapulohumeral muscles during rugby tackle. 15 healthy professional rugby players participated in the study. Surface EMG activity was assessed for timing of onset relative to time of impact during a modified tackle activity in pectorialis major, biceps brachii, latissimus dorsi, serratus anterior and infraspinatus muscles. Results: Onset of activity occurred in all muscles prior to impact. Factorial ANOVA showed significant differences between muscles in activation timing (p = 0.0001), paired t-tests revealed that serratus anterior was activated prior to all other muscles tested (p < 0.04, for all comparisons), with comparison between all other muscles showing no significant differences (p > 0.05), except pectorialis major on all comparisons showed significantly later activation timing than all other muscles (p < 0.001). Conclusion: Muscle activation timing may if not properly balanced around the shoulder girdle expose the glenohumeral joint to excessive load and stress. This paper demonstrates a simple method which sets out some preliminary normative data in healthy players. Further studies relating these data to injured players are required.