oa At return to play following hamstring injury the majority of professional football players have residual isokinetic deficits

Background: There is an on-going debate regarding the optimal criteria for return to sport (RTS) after an acute hamstring injury. Less than 10% isokinetic strength deficit is generally recommended but this has never been documented in professional football players after rehabilitation. Our aim was to evaluate isokinetic measurements in MRI positive hamstring injuries. Methods: Isokinetic measurements of professional football players were obtained after completing a standardized rehabilitation programme. An isokinetic strength deficit of more than 10% compared to the contralateral site was considered abnormal. Re-injuries within two months were recorded. Results: 52 players had a complete set of isokinetic testing before clinical discharge. There were 27 (52%) grade 1 and 25 (48%) grade 2 injuries. 35 out of 52 players (67%) had at least one out of the three hamstring-related isokinetic parameters display a deficit of more than 10%. The percentage of players with 10% deficit for Hamstring concentric 60°*s-1, 300°*s-1 and Hamstring eccentric was respectively 39%, 29% and 28%. There was no significant difference of mean isokinetic peak torques and 10% isokinetic deficits in players without re-injury (N=46) compared to players with re-injury (N=6). Conclusion: 67% of the clinically recovered hamstring injuries showed at least one hamstring isokinetic testing deficit of more than 10%. Normalisation of isokinetic strength seems not to be a necessary result of the successful completion of a football specific rehabilitation programme. The possible association between isokinetic strength deficit and increased re-injury risk remains unknown.