Shoulder vibratory exercises improves shoulder external rotation muscle strength and shoulder function: Randomized comparison trial

BACKGROUND: Based on electromyography measurements, shoulder vibratory exercises efficiently stimulate shoulder muscles activity. Yet very few studies have supported that shoulder vibratory exercises increased shoulder muscles strength and function, and the noninferiority compared with conventional elastic resistance exercises remains unknown. OBJECTIVE: This study investigated the effect of vibratory exercises versus conventional elastic resistance exercises with elastic bands on shoulder external rotation muscles strength and functional performance in young adults. METHODS: 26 young adults (7 males and 19 females, with age 23.89 +/- 3.02) were recruited and randomly allocated to shoulder vibratory exercises with FLEXI-BAR (FLEXI-BAR group) or conventional resistance exercises with elastic band (TheraBand group) for 3 times/week, 4 weeks totally. Shoulder external rotator muscles strength test and Underkofler softball distance throw test (USDTT) were performed before and after the training period. RESULTS: After 4 weeks training, shoulder external rotator muscles strength increased 22.25 +/- 15.06 N (P = 0.004, effect size = 1.48) within FLEXI-BAR group and 22.81 +/- 14.94 N (P = 0.007, effect size = 1.53) within TheraBand group. There were no statistically significant differences between groups in the three muscle strength tests (P > 0.65). Regarding shoulder function, FLEXI-BAR exercises increased the throw distance 0.81 +/- 0.92 meters in USDTT (P = 0.041, effect size = 0.88) while TheraBand exercise did not (P = 0.284), yet there was no statistically significant between group effects (P = 0.608). CONCLUSIONS: These findings suggest that shoulder vibratory exercises can improve shoulder muscles strength in young adults and can be a useful alternative to the conventional elastic resistance exercises to improve the shoulder muscles strength and function. This provides therapists with more options in terms of choosing training equipment for rehabilitation programs.