Shoulder joint kinetics of the elite wheelchair tennis serve

Background: The shoulder is a key joint in wheelchair locomotion and commonly implicated in injury among virtually all wheelchair populations. In tennis, quantification of the shoulder joint kinetics that characterise the wheelchair serve could enhance injury prevention and rehabilitation practices as well as assist coaches evaluate the efficacy of their current technical instruction. Methods: A 12-camera, 250 Hz Vicon motion analysis system (Oxford Metrics Inc., UK) recorded the 3D flat (WFS) and kick serve (WKS) motions of two male top 30-ranked international wheelchair players. Mechanical comparisons between wheelchair players, as well as to the previously captured data of 12 highperformance able-bodied players executing the same types of serves, were undertaken. Results: Without the benefit of a propulsive leg action, wheelchair players developed lower peak absolute (similar to 32 m/s) and horizontal (similar to 28 m/s) pre-impact racquet velocities than able-bodied players (similar to 42 m/s, similar to 38 m/s). Wheelchair serve tactics nevertheless necessitated that higher pre-impact horizontal and right lateral racquet velocities characterised the WFS (similar to 29 m/s, WKS: similar to 26 m/s) and WKS (similar to 4 m/s, WFS: similar to 11 m/s) respectively. The shoulder joint kinetics that contributed to the differential racquet velocity profiles were mostly developed independent of wheelchair serve type, but varied with and were likely related to the level and severity of spinal cord injury of the individual players. Conclusions: Compared with able-bodied players, wheelchair players experienced matching pre-and post-impact shoulder joint loads, such that wheelchair and able-bodied playing populations appear subject to similar shoulder joint injury risk.