Seasonal changes in glenohumeral joint isokinetic strength in professional rugby league players

Objective: To assess glenohumeral joint (GHJ) rotation strength across a rugby league season, since strength of rotator cuff musculature may protect against contact injuries to the shoulder.
Design: A prospective cohort study was used to compare GHJ rotation pre-, in-, and post-season.
Setting: Laboratory.
Participants: Twenty-nine players from a professional European Super League club.
Main Outcome Measures: Isokinetic dynamometry for concentric and eccentric muscle actions for shoulder internal and external rotation at 240°/s. Peak torque, traditional strength ratios, and dynamic control ratios were compared.
Results: There were no significant differences between peak torque strength parameters at any time point. Similarly, differences in strength ratios failed to reach statistical significance across the season. Ipsilateral strength ratios were indicative of selective strengthening of internal rotators for concentric and eccentric muscle actions.
Conclusions: The findings suggest that rugby league players are no more likely to sustain a shoulder injury in the latter stages of the season as a result of decreased GHJ rotation strength. Players were able to maintain strength across the season which is valuable to practitioners developing conditioning programmes to optimise performance and minimise the risk of injury. This may afford protection, particularly during forced external rotation following physical contact.