Biomechanical evaluation of healthy shoulder joints in elite junior javelin throwers and volleyball players

The painful throwing shoulder is a very common and serious problem among overhead throwing athletes. Repetitive overload on the throwing shoulder is the acknowledged cause for physiologic adaptations and degenerative lesions of the shoulder’s soft-tissue and bony structures. However, the etiology of throwing-related shoulder injuries is complex and not conclusively understood yet. There is a need for preventive diagnostics at a presymptomatic stage for an early detection of the individual injury risk. Furthermore, primary prevention strategies for shoulder overuse injuries in young athletes must be developed. The main objective of this work was to prospectively evaluate the effect of a 1-year preventive exercise intervention on shoulder joint rotational mobility and strength as well as scapular kinematics, since these factors are thought to be crucial components for the shoulder joint function. A comprehensive biomechanical screening was developed in order to assess these factors. The test set-up consisted of standard goniometry, maximum strength testing using the IsoMed2000 isokinetic dynamometer and 3-D motion capture of the scapulae during multiplanar active humeral elevation using a 6-camera VICON MX-3 system. For the standardized exercise program, stretching and strengthening exercises were newly assembled based on literature recommendations. 13 male javelin throwers (age 17.5 ± 0.8 years) and 14 male volleyball players (age 16.7 ± 1.0 years) followed the 1-year exercise program and completed all pre- and post-intervention tests.