The potential relevance of altered muscle activity and fatigue in the development of performance-related musculoskeletal injuries in high string musicians

Background: Muscle fatigue has been reported as a risk factor for the development of performance-related musculoskeletal disorders (PRMD) in musicians. However, little research exists to support this claim. The aim of this study was to investigate whether changes occur in muscle activity patterns during high string performance over a prolonged playing period, and whether this is influenced by PRMD. Methods: High string musicians were divided into a PRMD and a non-PRMD group. They played a chromatic scale pre and post and a self-chosen “hard” (Borg scale 16-17) piece of music for one hour. Electromyography data recorded from arm, shoulder and trunk muscles was analyzed: the amplitude to measure muscle activity characteristics and the lower frequency to measure muscle fatigue. Differences between and within groups and the frequency spectrum were analyzed using linear mixed models. Results: Fifteen musicians participated (7 PRMD: 22.8 years, 2 male/5 female and 8 non-PRMD: 34.3 years, 2 male/6 female). Changes in muscle activation patterns were observed between and within both groups, however changes varied significantly depending on group affiliation. Significant low frequency spectrum changes between groups were observed in overall muscles of the right arm (p=0.04) and left forearm flexors (p=0.05) following one hour of playing. Conclusions: Muscle activity and frequency spectrum shifts differ in high string musicians with and without PRMD, suggesting possible differential muscle fatigue effects between the groups

The Effect of Muscle Fatigue on Activation Patterns of the Biceps Femoris and Semitendinosus Muscles in Healthy Soccer Players Aged 19 to 35 Years

Introduction: Hamstring injuries are among the most common injuries in soccer players. Especially the danger of hamstring injuries increases in the final third of each half, with the biceps femoris muscle being highly susceptible, but currently there is no supporting evidence in soccer players. It is important to investigate to provide a basis for further clinical investigations in order to reduce the risk of hamstring injuries. Objective: To investigate a soccer-specific muscle fatigue protocol has an effect on the activation patterns of the biceps and semitendinosus muscles and correlates with the subjectively perceived exertion of the soccer players. Methods: 19 healthy soccer players aged 19 - 35 years were included and underwent a standardized procedure that included: (1) performance of the nordic hamstring curls (NHC) and a 10m sprint (pre-test), (2) a soccer-specific muscle fatigue loading protocol for 30 minutes with subsequent rating of perceived exertion (RPE), (3) re-assessed like pre-assessment (post- test). Electromyography (EMG) data were recorded the biceps and semitendinosus muscles of both legs. Two parameters were analyzed: the peak amplitude during the NHC and the mean amplitude during the 10m sprint. Results: The RPE score (9.5, p<0.001) and 10m sprint shows significant differences between pre- and post- test for the biceps (standing leg: -82.45, kicking leg: -81.77; p<0.01) and semitendinosus muscle (standing leg: -60.08, p=0.001); kicking leg: -65.30, p=0.03). Significant correlation exists between RPE score and biceps muscles at posttest (standing leg: r=-0.54, kicking leg: r=-0.51; p<0.05). Conclusion: Muscle fatigue leads to significant changes in the activation behavior of the hamstring muscles. In particular, the biceps muscle shows a correlation with perceived exertion, the higher the exertion, the lower the muscle activity. This may help explain the higher prevalence of the biceps muscle in hamstring injuries and offers a basis for further clinical investigation