Impact of an isometric or eccentric hip extension exercise intervention on hamstring strength, architecture, and morphology: a randomised intervention trial

Introduction: Hamstring strain injury (HSI) is the leading cause of time lost from competition in running-based sports. Following return to sport, individuals with previous HSI often have persistent deficits hamstring muscle strength, architecture and morphology. Considerable research effort has gone into identifying ways address these variables, as they been associated future risk. Eccentric knee flexion exercises shown modify although implementation interventions prevention programs not widespread. Conventional hip extension can also improve morphology, but eccentric variations this intervention investigated. Isometric are prescribed another way load hamstrings, however, their impact on morphology unknown. Therefore, study aimed investigate architectural, strength morphological adaptations following an or isometric exercise intervention. Methods: Twenty-four recreationally active males were randomly allocated perform either (n=12) intervention, twice per week for six weeks, followed by a four-week detraining period. Biceps femoris long head (BFlh) was assessed pre-intervention, mid-intervention, post-intervention, post-detraining via two-dimensional ultrasound. post-intervention during isokinetic flexion, extension, Nordic single leg bridge repetitions fatigue test. magnetic resonance imaging prior testing sessions. Results: The significantly increased BFlh fascicle length (+19.7%; p<0.001; d=1.57), torque (ECC60°.s-1; +12%; p<0.005; d=0.66; ECC180°.s-1; +8.3%; p<0.05; d=0.41), (+13.3%; d=1.96) semimembranosus (SM) volume (+12.5%; d=2.25). four weeks detraining, reduced back baseline group (-14.8%; d=-1.25), while torque, SM volumes unchanged. (+10.4%; d=0.54), force (+12.4%; semitendinosus (ST) (+15%; p=0.054; d=1.57). No significant changes observed any other outcome measures Conclusions: effectively length, which might Both demonstrated contraction mode-specific increases strength. However, resulted preferential hypertrophy led selective ST. Application field: may risk factors if implemented rehabilitation programs. lesser modifying key factor could be used increase ST volume, relevant anterior cruciate ligament reconstruction using graft. authors report that no conflict interest exists. My co-authors I acknowledge we relevance submission