Hamstrings Shear Wave Speeds Not Altered After 6 Weeks Of Romanian Deadlift Or Nordic Curls

Shear wave speed (SWS) is a reliable quantitative technique to characterize muscle stiffness and is a complementary method to traditional sonography to assess muscle adaptations after resistance training. However, findings from studies that have measured changes in passive muscle stiffness assessed by SWS following resistance training are inconsistent. PURPOSE: To determine regional adaptations in muscle SWS following 6 weeks of Romanian deadlift (RDL) and Nordic hamstring exercise (NHE) eccentric (ECC)-biased training. METHODS: SWS imaging was performed prior to group randomization and immediately following ECC training. Each participant laid prone on an exam table with their hips and knees in a neutral position. Ultrasound SWS images were collected from the biceps femoris muscle of the dominant limb following at least 3 minutes of rest. SWS maps were generated at 33%, 50%, and 67% of the thigh length. SWS values were extracted using three separate 5 mm diameter circles then averaged across each image for subsequent analysis. Pre- and post-training SWS differences were calculated. A full factorial linear mixed effects model with group and imaging location as main effects and subject as a random effect was used to detect between-group and regional differences in SWS. Descriptive data are presented as mean (standard deviation) and model outputs are presented as SWS difference [95% confidence interval]. RESULTS: Thirteen participants were included across the RDL (n = 7 (3 males), age = 20.5 (1.1) years, height = 169.9 (7.4) cm, mass = 69.1 (4.9) kg) and NHE groups (n = 6 (3 males), age = 21.0 (1.3) years, height = 171.0 (11.8) cm, mass = 70.4 (12.9) kg). There was no significant group by location interaction (p = 0.28). Change in SWS was not significant between groups (RDL: 0.00 [-0.07, 0.07] m/s, NHE: 0.07 [-0.01, 0.14] m/s, p = 0.19) or across regions (proximal: 0.05 [-0.03, 0.13], mid-belly: 0.04 [-0.04, 0.12], and distal: 0.01 [-0.07, 0.09] m/s, p = 0.79). CONCLUSIONS: These findings suggest the hip-dominant RDL and knee-dominant NHE induce comparable changes in pre- and post-training SWS differences across the biceps femoris muscle. Future work should investigate the relationship between passive SWS assessed at different hip and knee angles and the relationship between SWS and muscle architecture following ECC training. Grants KL2TR002374 and UL1TR002373 awarded to UW ICTR through NIH NCATS