Multiscale hamstring muscle adaptations following 9 weeks of eccentric training

Max H Andrews; Anoosha Pai S; Reed D Gurchiek; Patricio A Pincheira; Akshay S Chaudhari; Paul W Hodges; Glen A Lichtwark; Scott L Delp

doi:10.1016/j.jshs.2024.100996

Multiscale hamstring muscle adaptations following 9 weeks of eccentric training

J Sport Health Sci. 2024 Oct 16:100996. doi: 10.1016/j.jshs.2024.100996. Online ahead of print.

Authors

Max H Andrews¹, Anoosha Pai S², Reed D Gurchiek³, Patricio A Pincheira⁴, Akshay S Chaudhari⁵, Paul W Hodges⁶, Glen A Lichtwark⁷, Scott L Delp⁸

Affiliations

¹ School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia; Department of Bioengineering, Stanford University, Stanford, CA, 94305, USA.
² Department of Bioengineering, Stanford University, Stanford, CA, 94305, USA.
³ Department of Bioengineering, Stanford University, Stanford, CA, 94305, USA; Department of Bioengineering, Clemson University, Clemson, SC, 29634, USA.
⁴ School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia; School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia; School of Health and Medical Sciences, The University of Southern Queensland, Ipswich, QLD, 4305, Australia.
⁵ Department of Radiology, Stanford University, Stanford, CA, 94305, USA.
⁶ School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia.
⁷ School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia; School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane, QLD, 4000, Australia.
⁸ Department of Bioengineering, Stanford University, Stanford, CA, 94305, USA; Department of Mechanical Engineering, Stanford University, Stanford, CA, 94305, USA. Electronic address: delp@stanford.edu.

PMID: 39461588
DOI: 10.1016/j.jshs.2024.100996

Abstract

Background: Eccentric training, such as Nordic hamstring exercise (NHE) training, is commonly used as a preventive measure for hamstring strains. Eccentric training is believed to induce lengthening of muscle fascicles and to be associated with the addition of sarcomeres in series within muscle fibers. However, the difficulty in measuring sarcomere adaptation in human muscles has severely limited information about the precise mechanisms of adaptation. This study addressed this limitation by measuring the multiscale hamstring muscle adaptations in response to 9 weeks of NHE training and 3 weeks of detraining.

Methods: Twelve participants completed 9 weeks of supervised NHE training, followed by a 3-week detraining period. We assessed biceps femoris long-head (BFlh) muscle fascicle length, sarcomere length, and serial sarcomere number in the central and distal regions of the muscle. Additionally, we measured muscle volume and eccentric strength at baseline, post-training, and post-detraining.

Results: NHE training over 9 weeks induced significant architectural and strength adaptations in the BFlh muscle. Fascicle length increased by 19% in the central muscle region and 33% in the distal muscle region. NHE also induced increases in serial sarcomere number (25% in the central region and 49% in the distal region). BFlh muscle volume increased by 8%, and knee flexion strength increased by 40% with training. Following 3 weeks of detraining, fascicle length decreased by 12% in the central region and 16% in the distal region along with reductions in serial sarcomere number.

Conclusion: Nine weeks of NHE training produced substantial, region-specific increases in BFlh muscle fascicle length, muscle volume, and force generation. The direct measurement of sarcomere lengths revealed that the increased fascicle length was accompanied by the addition of sarcomeres in series within the muscle fascicles.

Keywords: Adaptation; Muscle architecture; Nordic hamstring exercise.