Hamstring force and stretch during progressively increasing running speeds and the eccentric phase of resistance training exercises commonly used for injury prevention and rehabilitation

OBJECTIVES: To compare the force and stretch demands experienced by the hamstrings during seven resistance training rehabilitation exercises and progressively increasing running speeds. METHODS: A cross-sectional design. Ten male and 10 female active participants performed two trials each of four self-paced gait speeds on a treadmill (walk, and jog, run and sprint at 50%, 75% and 100% of maximum effort, respectively) and two sets of six repetitions each of seven resistance training exercises at a rate of perceived exertion ≥8/10. Data from MRI, electromyography and three-dimensional motion capture were used with musculoskeletal modelling to estimate the muscle forces and musculotendinous unit stretch during each task for the biceps femoris long head (BFlh), semimembranosus (SM) and semitendinosus (ST). RESULTS: The bilateral Romanian deadlift (RDL) produced significantly greater peak force in the BFlh (1.6BW, 95% CI 1.5 to 1.7) and SM (1.9BW, 95% CI 1.8 to 2.1) than any other resistance training or gait task (p