Hamstring injuries are common in professional football and have been related to the imbalance between knee flexor and extensor strength. The aim of our study was to relate the maximum strength values of flexor eccentric/extensor concentric (Flexexc30/Extcon240) and peak torque angle with the hamstring injuries incidence sustained by football players during a season to provide reference values of this parameter to allow injuries prevention. Twenty players of a Second Division team of the Football Professional League bilaterally performed an isokinetic test of eccentric knee flexion at 30º/s and concentric knee extension at 240º/s during the pre-season. The Flexexc30/Extcon240 ratio and the knee angle of peak torque were calculated, and the players` injuries were registered throughout the season. The results showed that two of the five injured players had Flexexc30/Extcon240 ratios lower than 0,89, value that has been previously used to determine the imbalance between knee flexor and extensor strength and the risk of injury (Croisier, Ganteaume, Binet, Genty, and Ferret, 2008). In addition, another two injured players obtained ratios between 0,93 and 1,00. On the other hand, no differences in the knee angle of peak torque between injured and non-injured players were found. These results indicate that the Flexexc30/Extcon240 ratio may be a useful index to determine the risk of hamstring injury in professional football players.
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