Synergistic trunk dynamics reduces risk of shoulder injury during volleyball hitting.

The follow through phase of volleyball hitting can cause shoulder injuries like rotator cuff tears, which is associated with the high arm angular velocities and the eccentric forces generated by the external rotators to slow the arm after striking the ball. We used musculoskeletal modelling and simulations to optimize the whole-body kinematics during volleyball hitting. We found that trunk motion in the direction of the swing during the follow through reduces the peak shoulder joint moments and arm velocity, which translates to reduced risk of rotator cuff injury.