Hamstrings muscle dynamics during the Nordic hamstring exercise and high-speed running

BackgroundThe Nordic hamstring exercise (NHE) and high-speed running are widely used training modalities to prevent hamstring strain injuries, yet the differences in the muscle lengths, forces, work, and power between these training modalities remain unclear. This study thus compared the dynamics of the most injured hamstrings muscle, biceps femoris long head (BFLH), for 14 participants (8 male and 6 female) performing the NHE and running between 4 and 8 m/s. MethodsWe used motion capture experiments and musculoskeletal simulation to quantify muscle fiber lengths and velocities, and muscle force, work, and power during the NHE and running. ResultsOur results show that peak muscle forces are greater during high-speed running (7.5 to 8 m/s) than the NHE, and that high-speed running also features longer muscle fiber lengths and higher muscle fiber lengthening velocities (p < 0.05). Negative muscle work was significantly greater during the NHE compared to running at all speeds (p < 0.001) because of the greater change in muscle fiber lengths during the NHE (p < 0.001). In contrast, peak negative muscle power was significantly lower during the NHE compared to running at 5 m/s and above (p < 0.01). ConclusionOur analysis reveals dramatic differences in the biomechanical demands of the NHE and running on the hamstrings muscles. Our results suggest that the two training modalities together provide complementary biomechanical stimuli to promote favorable BFLH injury prevention adaptations.