The effect of short-term strength intervention on muscle activity of shoulder girdle during simulated crawl in elite swimmers

Objective: The aim of this study was to assess the effect of strength intervention on muscle activity and pain during simulated crawl in elite swimmers.

Methods: Fifteen elite Czech swimmers (4 females, 11 males) within the age of 22.8 ± 3.4 years participated in this study. At the baseline, muscle activity and pain evaluation was performed. For the shoulder joint pain assessment, the visual numeric scale (VNS) and the Swimmer's Functional Pain Scale (SFPS) questionnaires were used. Participants underwent surface electromyography (SEMG) examination of 8 evaluated muscles (trunk and upper arm) during simulated a 100 metres crawl race on swimming ergometer (VASA SwimErg, Essex Junction, Vermont, USA). After a 30 minutes long strength intervention, 100 metres crawl SEMG, VNS and SFPS were evaluated again. The smallest important change in muscle activation was set to 10%.

Results: The effect of strength intervention on muscle activity was not significant in all muscles, however effect size evaluation showed small effect of intervention in biceps brachii (p = .311, d = 0.33), upper part of trapezius (p = .033, d = 0.46) and serratus anterior (p = .103, d = 0.22) and medium effect in lower part of trapezius (p = .053, d = 0.62). Magnitude-based decision analysis showed a highly increased muscle activity in biceps brachii. Also in serratus anterior muscle activity increased as well. Difference in shoulder joint pain before and after intervention of the dominant upper limb according to the SFPS questionnaire and VNS was not statistically significant.

Conclusion: A 30 minutes long strength intervention had a significant effect on the muscle activity of the upper part of m. trapezius. There was no significant effect of the intervention on pain.