Electromyographic Analysis of Shoulder Girdle Muscles in Volleyball Throw: A Reliability Study

Study aim: The aim of this study was to investigate the reliability of the electromyographic activity of selected shoulder girdle muscles during the overhead volleyball throw.

Material and methods: The test-retest reliability of EMG activity of selected shoulder muscles during an overhead volleyball throw was investigated in 15 non-symptomatic university-level female volleyball players for within-day sessions (with a one-hour interval) and between-day sessions (with a one-week interval). Time broadness (a measure of coordination) and root mean square of electromyography signals were obtained. Results: A high within-day (0.85-0.99) and moderate to high between-day (0.68-0.93) intraclass correlation coefficient for normalized RMS activity and a high within-day and between-day intraclass correlation coefficient (0.94 and 0.80; respectively) for time broadness were observed. Absolute agreement of measurements had small values (0.15-1.96). Trends toward higher intraclass correlation coefficient values and lower standard error of measurements, minimum detectable change, mean differ­ences and limits of agreements values were observed for within-day reliability in all test results compared with between-day reliability.

Conclusions: The results suggest that the activity of shoulder muscles can be reliably assessed during the overhead volleyball throw with the described procedure both in the amplitude domain (normalized average root mean square) and the time domain (time broadness of the activities).