The effect of exercise intervention on shoulder girdle biomechanics and isokinetic shoulder muscle strength in university level cricket players: a bilateral comparison
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Literature indicates that adaptations such as scapula protraction, altered glenohumeral range of motion (ROM) and strength adaptations are commonly detected in the dominant shoulder of overhead athletes. Previous research has linked these adaptations to shoulder instabilities and a higher risk of injuries, for instance shoulder impingement syndrome, rotator cuff tears and labral tears. This study was aimed at detecting asymmetry in the shoulder rotation ROM and isokinetic shoulder rotation muscle strength characteristics of North-West University (NWU) cricket players (Potchefstroom campus), as well as the relationship of scapula protraction with the detected asymmetry. It also sought to determine the effect of a controlled stability exercise intervention on the bilateral biomechanical and isokinetic shoulder rotation muscle strength deficits in cricket players at the NWU (Potchefstroom Campus). Forty-five cricket players voluntarily completed baseline testing and 30 cricketers completed the intervention phase and follow-up testing (randomly divided into an intervention group, n=15 and a control group, n=15). Scapula protraction, shoulder rotation ROM and isokinetic shoulder rotation muscle strength testing were performed on both groups at baseline, as well as after the six-week exercise intervention. The experimental group underwent two-weekly supervised exercise sessions that focused on correcting postural and biomechanical adaptations usually observed in overhead sports participants in addition to their normal conditioning regime. The reference group, which followed only normal training,was educated on these adaptations and corrective exercises. Some of the players in the reference group also performed the corrective exercises on their own during the intervention period. Baseline testing of the entire group (n=45) indicated that on average, the dominant shoulder of the cricketers was significantly more protracted (p≤0.001), with significantly less internal rotation (IR) ROM (p≤0.001) and more external rotation (ER) ROM (p≤0.001) than the nondominant side. Both the IR and the ER average concentric peak torque were significantly higher in die dominant shoulder (p≤0.001 and p=0.002 respectively). Associations with scapula protraction were only significant on the dominant side, with shoulder ER ROM indicating a significantly negative association (r=-0.3, p=0.05), and shoulder IR average peak torque a significantly positive association (r=0.3, p=0.05). Although improvements in especially scapula protraction and shoulder IR ROM were observed after the six-week intervention period in both the experimental group(p=0.067 and p≤0.001) and the reference group (p=0.006 and p≤0.001),the IR ROM of only the experimental group no longer differed significantly from the norm. The exercise intervention indicated no effect on the concentric muscle strength characteristics. This study indicated that asymmetry does exist in the shoulders of cricket players, cricket being a unilateral overhead sport. The dominant shoulder was more protracted, with less IR and more ER rotation ROM, as well as significantly higher IR and ER rotational muscle strength than the non-dominant shoulder. Exercises performed in season, which were aimed at correcting these adaptations, only indicated a significant improvement in IR ROM under supervision. Future research should investigate the effect of corrective exercises in different periods of the cricket-playing season and ensure that the participants in the control group are not educated on these exercises and are not performing them during the intervention period. Ethically speaking, it might be a challenge to divide a cricket squad; therefore, future studies on this matter should use a different squad with more or less the same training and competition schedules as the control group of that study.
- Health Sciences