Effect of preconditioning exercise on biceps brachii myotendinous junction displacement during elbow flexor eccentric exercise

Chih Chiao Ho, Kazunori Nosaka, Kou Wei Tseng, Wei Chin Tseng, Wing Yin Lau, Gregory C. Bogdanis, Trevor C. Chen

Research output: Contribution to journalArticlepeer-review

Abstract

The present study tested the hypothesis that 30 low-intensity (10%) eccentric contractions (10%EC) or two maximal voluntary isometric contractions at a long muscle length (2MVIC) that were performed at two days before maximal eccentric exercise of the elbow flexors consisting of five sets of six maximal eccentric contractions (MaxEC) would reduce increases in biceps brachii distal myotendinous junction displacement (MTJd) over the eccentric contractions during MaxEC. Sedentary young men were randomly placed (n = 12/group) to a control group that performed two bouts of MaxEC (CONT-1st, CONT-2nd) separated by two weeks, or one of two preconditioning groups that performed 10%EC or 2MVIC at 20° elbow flexion at two days prior to MaxEC. All exercises were performed by the non-dominant arm. MTJd of each contraction was assessed by B-mode ultrasound, and its changes over sets were compared among the groups. The average MTJd from the start to the end of six eccentric contractions in the first set was similar among the groups (6.4 ± 0.7 mm). The MTJd increased from the first to fifth set, but the increase was smaller (P <.05) for the 10%EC (13 ± 6%) and 2MVIC (16 ± 9%) groups, and CONT-2nd (3 ± 6%) when compared with CONT-1st (60 ± 12%). Both 10%EC and 2MVIC groups showed smaller (P <.05) changes in all muscle damage markers after MaxEC similarly when compared with CONT-1st, but the changes were greater than those after CONT-2nd. These results supported the hypothesis that protective effect was associated with less MTJd changes, suggesting that this is associated with the mechanisms underpinning the preconditioning effect on muscle damage.

Original languageEnglish
Pages (from-to)813-825
Number of pages13
JournalScandinavian Journal of Medicine and Science in Sports
Volume31
Issue number4
DOIs
Publication statusPublished - 2021 Apr

Keywords

  • low-intensity eccentric contractions
  • maximal voluntary isometric contractions
  • muscle damage
  • myotendinous junction
  • protective effect

ASJC Scopus subject areas

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

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