Shoulder internal and external rotation strength and prediction of subsequent injury in water-polo players.

Water-polo players have greater isokinetic shoulder strength than age-matched controls. Due to the repetitive demands of throwing, however, water-polo players demonstrate an altered strength ratio, with greater internal rotation (IR) strength relative to external rotation (ER). The relationship between shoulder strength and risk of shoulder injury is unknown. In addition, the effect on test position for strength testing on the reliability of handheld dynamometry (HHD) in this population is not known. The aims were to determine the: (a) Inter-rater reliability of HHD testing of IR and ER strength in two positions: neutral and 90°abduction-90°ER (90-90) and (b) relationship between preseason shoulder strength and occurrence of future injury in sub-elite water-polo players. Two assessors measured shoulder IR and ER strength using HHD in 15 water-polo players across two testing days. Athletes were followed over a 6-month period, and injury was assessed and recorded by the team physiotherapist. Measurement of water-polo players' isometric IR and ER strength in the clinical setting had good to excellent inter-rater reliability; however, systematic error was observed in the neutral position but not the 90-90 position. Irrespective of testing position, the neutral and 90-90 test position showed a significant difference (P = 0.01) in absolute preseason IR and ER mean strength between prospectively injured and non-injured players. There was no significant difference in strength ratio or strength normalized for body mass index. These results suggest that preseason strength testing may help identify players at risk of in-season shoulder injury.