Hamstring muscle tear with recurrent complaints: An isokinetic profile

The purpose of this study was to determine the isokinetic profile of specialized athletes with previous hamstring tears and recurrent complaints upon return to sports activities, using a Kintrex 500 dynamometer. Twenty-three subjects were examined through a concentric protocol and fifteen of them benefited from a complementary eccentric assessment. Despite the fact that some cases presented normal isokinetic results, the statistical analysis has demonstrated particular features. In reference to the non-involved side performances, the average reduction of peak torque (PT) of the injured muscles surpassed 20% in eccentric contraction. The relationship between bodyweight normalized PT and angular velocity demonstrated significant differences in comparison with those of selected non-injured sprinters, most notably in the eccentric sector. A mixed ratio (Flexors(eccentric)/Quadriceps(concentric)) appeared significantly reduced (0.75 +/- 0.23) for the injured leg, in comparison with the contralateral non-injured limb (0.90 +/- 0.16) and with a control population (0.98 +/- 0.14). For the eccentric mode, the angle of peak torque (APT) of the strained muscle occurred in an abnormal articular sector corresponding to a weaker hamstring muscle lengthening than normal. These observations strongly suggest that, among the causative factors, the persistence of muscle strength abnormalities gives rise to recurring hamstring injuries.