Muscle activity and kinematics during three hamstring strengthening exercises compared to sprinting: A cross-sectional study

Abstract

Background
 Sprinting is a crucial task in many sports and remains the major activity during which hamstring muscle injuries occur (Schache et al., 2012). Though the biceps femoris long head predominantly gets injured (Grange et al., 2023), hamstring strengthening exercises frequently seem to activate the semitendinosus more effectively (Bourne et al., 2017). A better understanding of how joint dominance influences activation levels of hamstring muscles may offer more clarity on the appropriate exercise selection in strengthening programs.
 Purpose
 This study compared 3 hip-dominant hamstring exercises (the rocker, perpetuum mobile fast and slow; PMfast and PMslow) and the Nordic Hamstring exercise (NHE) on their potential to simulate sprint-like activity and kinematics.
 Methods
 Muscle activity of the posterior kinetic chain (mm. biceps femoris, semitendinosus, gluteus maximus and gastrocnemius medialis) was measured with surface electromyography (sEMG) during every exercise and treadmill running at 75% of the individual maximal sprint velocity in 8 male athletes (age: 24.0 years ± SD 2.9; body mass: 76.8 kg ± 7.7; height: 1.79 m ± 0.08). sEMG data was normalized to maximal sprinting. 3D-motion capture was employed to assess hip and knee angles.
 Results
 This study revealed higher activity of the hamstrings for the explosive exercises ranging from 63.9% [95%CI: 56.3-71.5%] (rocker) to 49.0% [95%CI: 40.4-57.6%] (PMfast) vs. 34.0% [95%CI: 29.1-38.9%] (NHE) to 32.1% [95%CI: 26.9-37.3%] (PMslow). The rocker especially showed highest hamstring and m. gluteus maximus activity. M. biceps femoris consistently showed higher activity than m. semitendinosus across all exercises in peak (mean difference: 0.16, [95%CI: 0.07-0.26]) and average (mean difference: 0.06, [95%CI: 0.01-0.11]) activity. PMfast, PMslow and NHE demonstrated lower hip flexion angle of peak hamstring activity than the rocker and high-speed running and every exercise showed lower hamstring elongation stress than during high-speed running.
 Discussion
 Hamstring activity is comparable to high-intensity treadmill running for NHE and PMslow, and higher for the rocker and PMfast. M. gluteus maximus activity varied, with the rocker and PMfast showing higher activity than in sprinting. All examined exercises demonstrated their peak activity at short hamstring muscle length.
 What this study adds to the existing knowledge
 This study generated first data on sprint-specificity of two not yet investigated versions of a unilateral hip thrust. Similar or higher activity than during sprinting and BFlh selectivity was reached through explosive, closed kinetic chain, hip-dominant movement.
 References
 Bourne, M. N., Williams, M. D., Opar, D. A., Al Najjar, A., Kerr, G. K., & Shield, A. J. (2017). Impact of exercise selection on hamstring muscle activation. British Journal of Sports Medicine, 51(13), 1021-1028. https://doi.org/10.1136/bjsports-2015-095739
 Grange, S., Reurink, G., Nguyen, A. Q., Riviera-Navarro, C., Foschia, C., Croisille, P., & Edouard, P. (2023). Location of hamstring injuries based on magnetic resonance imaging: A systematic review. Sports Health, 15(1), 111-123. https://doi.org/10.1177/19417381211071010
 Schache, A. G., Dorn, T. W., Blanch, P. D., Brown, N. A., & Pandy, M. G. (2012). Mechanics of the human hamstring muscles during sprinting. Medicine & Science in Sports & Exercise, 44(4), 647-658. https://doi.org/10.1249/MSS.0b013e318236a3d2