Background There is little information about the effect of hamstrings training on hip and knee joint function, morphology of each hamstring muscle, and the rate of injury incidence.
Objective To clarify the effect of hamstrings training on H:Q strength ratio in hip and knee joint, the morphological adaptations of each hamstring muscle, and the rate of strain injury incidence.
Design Prospective, randomized controlled trial.
Setting Collegiate, elite division.
Participants 23 healthy collegiate Lacrosse players were recruited voluntarily, and 20 (39 limbs) of them finished the study.
Interventions Subjects were randomly divided into 3 groups; Single-leg Deadlift (DL) intervention, Nordic Hamstrings (NH) intervention, and control (CR). DL and NH groups joined the training program in twice a week for 6 months.
Main Outcome Measurements Before (Pre) and 1, 3, and 6 months after training period, isokinetic strength testing was conducted to measure flexion and extension torques in hip and knee joint, and magnetic resonance imaging to determine the cross sectional area (CSA) of each hamstring muscle.
Results After the training of 3 months, only in DL group, significant increase of hip extension torque (+25.2±9.4%) and H:Q ratios in the hip joint (1.28±0.43→1.61±0.48) were found, and significant increase of CSAs were found in biceps femoris long head (+12.0±3.7%) and semimembranosus (+25.5±4.1%) muscle (P<0.05). No strain injury has reported in all groups.
Conclusions Hip extension (Single-leg Deadlift) exercise training may be useful for preventing and rehabilitating from hamstring strain injury by stimulating hypertrophy in biceps femoris long head and semimembranosus muscle and promoting improvements in hip extensor strength and H:Q ratio in hip joint. These data may provide compelling evidence to warrant the further exploration of hip extension oriented exercises in hamstring strain injury prevention protocols.