Effect of Powerball on shoulder muscle activity and maximum strength

Muscles around the shoulder are important for its dynamic stability. Strengthening them is a necessity of muscle rehabilitation. This study attempted to investigate the effect of Powerball (as a relatively new method) on shoulder muscles strengthening exercises. Seventy-five healthy subjects were randomly divided into experimental (n =50) and controls (n=25) groups. Evaluation of shoulder muscles activity was conducted using electromyography of middle deltoid, upper Trapezius, Latissimus dorsi and Infraspinatus muscles in 90 degree arm abduction with an active powerball (experimental group) and an inactive powerball (control group) immediately and again after 12 days of training. In the experimental group, muscle activity increased significantly in all four muscles while using the Powerball compared to resting mode (P <0.01). However, these values were not significant in the control group. In the case of deltoid and upper Trapezius, muscle activity increased significantly after 12 days of exercise in the experimental group (P = 0.04). A significant increase in muscle activity was observed before and after 12 days of exercise in the experimental group compared to the control group (P <0.01). In the control group, muscle activity was not statistically significant compared to pre-exercise. Regarding Latissimus dorsi, there was no significant increase in muscle activity in the experimental and control groups compared to pre-exercise and also between the experimental and control groups (P> 0.05). The results of this study showed that using the Powerball and exercising with it in 90 degrees of abduction can significantly increase the maximum strength and muscle activity of deltoid and upper trapezius muscle activities.