Muscle length influence on rectus femoris damage and protective effect in knee extensor eccentric exercise

Ryoichi Ema, Kazunori Nosaka, Ryosuke Kawashima, Akihiro Kanda, Koya Ikeda, Ryota Akagi

Research output: Contribution to journalArticlepeer-review

Abstract

This study tested the hypothesis that the magnitude of rectus femoris (RF) damage and the repeated bout effect (RBE) would be greater after knee extensor eccentric exercise performed in a supine (long RF lengths) than a sitting (short RF lengths) position, and the muscle length effects would be more prominent at the proximal than distal RF. Young untrained men were placed to one of the two groups (n = 14 per group). S group performed the knee extensor eccentric exercise in the sitting position for the first bout and the supine position for the second bout, and L group performed the exercise in the supine position for two bouts, with 4 weeks between bouts. Dependent variables included evoked and maximal voluntary isometric contraction (MVC) torque, electromyography (EMG) during MVC, muscle soreness, and shear modulus, which were measured before and 1-3 days after each exercise bout. After the first bout, L group in comparison with S group showed greater (P <.05) changes in hip flexor MVC torque (average of 1-3 days post-exercise: −11.1 ± 9.4% vs −5.0 ± 7.5%), proximal RF EMG (−22.4 ± 16% vs −9.0 ± 21.9%), and proximal RF shear modulus (33.2 ± 22.8% vs 16.9 ± 13.5%). No significant differences between groups were evident for any of other variables after the first bout including knee extensor MVC torque, and for the changes in all variables after the second bout. These results supported the hypothesis that RF damage would be greater for the spine than sitting position especially at the proximal region, but did not support the hypothesis about the RBE.

Original languageEnglish
Pages (from-to)597-609
Number of pages13
JournalScandinavian Journal of Medicine and Science in Sports
Volume31
Issue number3
DOIs
Publication statusPublished - 2021 Mar

Keywords

  • hip flexion
  • maximal voluntary contraction
  • muscle soreness
  • repeated bout effect
  • shear modulus

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

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