Knee flexor muscle fatigue during repeated Nordic hamstring exercise.

Background: Nordic hamstring exercise is an effective method for preventing hamstring strain injury. In this study, we investigated the response of knee flexors regarding increased muscle force and fatigue when the Nordic hamstring exercise was performed repeatedly to further understand how it can prevent hamstring strain injury.

Methods: The Nordic hamstring exercise was performed 10 times by 53 athletes; knee flexor peak tensile force and the respective flexion angle were compared at different phases during this sequence: phase 1, 1 Nordic hamstring exercise force; phase 2, mean value during the 2-4 repetitions; phase 3, mean value during the 5-7 repetitions; and phase 4, mean value during the 8-10 repetitions.