Adaptations In Muscle Architecture Following Volume- And Eccentric Time-matched Romanian Deadlift Versus Nordic Hamstring Exercise

The Nordic hamstring exercise (NHE) places high eccentric (ECC) demand on the hamstrings, which stimulates muscle architectural adaptations in the biceps femoris long head (BFlh). The NHE has been widely used as a primary injury prevention exercise, though hip-dominant hamstring exercises may better target the BFlh. Few studies have compared BFlh adaptations following the Romanian deadlift (RDL) and NHE while matching training volume and ECC time. PURPOSE: To investigate the effects of 6 weeks RDL vs. NHE ECC training on BFlh architecture. METHODS: Twenty-one participants were randomly allocated to either an RDL or NHE group for 6 consecutive weeks of training. Participants laid prone on an exam table with their hips and knees in a neutral position. Longitudinal B-mode images were collected pre- and post-intervention unilaterally along the BFlh using a Logiq P9 ultrasound system (GE Healthcare, Waukesha, WI). BFlh fascicle length (FL) and pennation angle (PA) at the muscle mid-belly were calculated. FL was calculated using trigonomic linear extrapolation methods, while PA was determined as the angle between the same fascicle and the intramuscular aponeurosis. Analysis was performed on the average of three representative fascicles from each participant. Separate linear mixed effects models were used to detect differences in FL and PA between groups. Descriptive data are presented as mean (standard deviation) and model outputs are presented as difference [95% confidence interval]. RESULTS: The RDL group consisted of n = 12 (age: 20.7 (1.0) years, height: 1.75 (0.1) m, mass: 73.4 (6.5) kg, males = 7), while the NHE group had n = 9 (age: 21.0 (1.3) years, height: 1.70 (0.1) m, mass: 68.5 (10.9) kg, males = 4). Group by time interactions were not significant for FL (p = 0.29) or PA (p = 0.18). No between-group differences were noted in FL (p = 0.82) or PA (p = 0.73). FL increased (0.92 [0.45, 1.39] cm; p < 0.01) while PA decreased following training (-1.23 [-1.63, -0.82] degrees; p < 0.01). CONCLUSIONS: The increase in FL and concurrent decrease in PA are primarily due to ECC exercise prescription since no between-group differences were observed. These findings provide practitioners flexibility in exercise selection between the RDL and NHE for eliciting adaptations thought to be beneficial for hamstring injury prevention measures.