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SHOULDER INJURY PREVENTION IN VOLLEYBALL: PERFORMANCE AND KINEMATICS ANALYSIS OF ALTERNATIVE SPIKE TECHNIQUES

Background Repetitive stresses during spike movements in volleyball, make the shoulder one of the most commonly exposed body parts, bringing athletes to prematurely interrupt their career. Objective Different spike techniques are supposed to be associated to different risk shoulder damage. Here we compared the kinematics of the 2 most diffused spike techniques, also with respect to performance. Design Cross sectional-experimental study. Setting Subjects were selected from high-level National teams. Participants 10 female and 11 male (22.4±6.5 years, 1.88±0.07 m, 79.08±9.41 kg). Interventions Subjects performed the traditional (TT) and alternative (AT) spike movement technique without jumping, jumping with and without hitting the ball. 3D kinematic of the upper right limb and trunk was recorded with an optoelectronic system. Glenohumeral joint was set as the centre of an imaginary sphere intersected by the distal end of the humerus. In order to obtain intersection angles (azimuth: longitude and elevation: latitude) independently from the overall body's movements, the sphere was considered attached to trunk. Humerus intra-extra rotation was calculated with Eulerian angles. Linear and angular velocities have been measured as well ball speed and jump height. Main outcome measurements Humerus trajectory of the 2 techniques travels along significantly different paths on the imaginary sphere. Results: Maximal humerus elevation was reduced by 7% in AT, while azimuth was significantly higher, when compared to TT. No difference between TT and AT was found for extra-rotation angles, while intra and extra-rotation angular velocities were significantly higher when adopting the AT. Conclusions Our method shows that AT could be potentially a preventive solution to the shoulder chronic pathologies, while maintaining, or even enhancing, athletes' performance. Furthermore it proved to be effective in visualizing the risks associated to different spike manoeuvres, showing in the same 3D space information regarding both humerus angles and velocities.