First-Division Softball Players with Shoulder Injuries Exhibit Upper-Body Compensatory Strategies Compared to Healthy Controls: A Case Study Using Wearable Inertial Sensors

The aim of this study was to assess the kinematic differences in the upper limb and trunk between healthy and shoulder-injured softball position (non-pitchers) players. Eleven first-division softball players (mean age: 25.9 ± 8.1 years) were enrolled: five players who had experienced a shoulder injury with consequent surgery (time from surgery to test: 0.9 years) and six healthy matched controls. The position players performed their typical throw motor task after receiving the ball from a buddy. Wearable inertial sensors (Xsens MTw Awinda) were used to collect the kinematical data on the shoulder, elbow, and trunk. Peak joint kinematics and range of motion (ROM) were compared between healthy and injured players separately for the “Pickup” and “Pass” phases. In the pickup phase, a higher internal/external rotation ROM of the shoulder was found in healthy players than in the injured ones (p = 0.016). Similarly, elbow flex/extension ROM was higher in the healthy players (p = 0.039). A higher peak of trunk flexion was also found in healthy players than the injured ones (p = 0.002). In the pass phase, shoulder internal/external rotation, adduction/abduction, and flex/extension ROM were greater in healthy than injured players (p = 0.050, p = 0.001, and p = 0.007, respectively). Healthy players also showed a higher elbow peak flexion (p = 0.022). The shoulder-injured players showed a lower ROM than the healthy ones during both the pickup and pass phases of a throw motor task. Despite being cleared to return to play, the injured players could voluntarily or unconsciously perform the motor task in a more conservative way than the healthy controls.