Regional changes in muscle activity do not underlie the repeated bout effect in the human gastrocnemius muscle

Research output: Contribution to journalArticlepeer-review

Authors

  • Patricio A Pincheira
  • Rodrigo Guzman-Venegas
  • Marta I Garrido
  • Andrew G Cresswell
  • Glen A Lichtwark

External organisations

  • The University of Queensland
  • School of Sport
  • Escuela de Kinesiología
  • University of Melbourne

Abstract

The repeated bout effect (RBE) confers protection following exercise-induced muscle damage. Typical signs of this protective effect are significantly less muscle soreness and faster recovery of strength after the second bout. The aim of this study was to compare regional changes in medial gastrocnemius (MG) muscle activity and mechanical hyperalgesia after repeated bouts of eccentric exercise. Twelve healthy male participants performed two bouts of eccentric heel drop exercise (separated by 7 days) while wearing a vest equivalent to 20% of their body weight. High-density MG electromyographic amplitude maps and topographical pressure pain sensitivity maps were created before, two hours (2H), and two days (2D) after both exercise bouts. Statistical parametric mapping was used to identify RBE effects on muscle activity and mechanical hyperalgesia, using pixel-level statistics when comparing maps. The results revealed a RBE, as a lower strength loss (17% less; P < .01) and less soreness (50% less; P < .01) were found after the second bout. However, different muscle regions were activated 2H and 2D after the initial bout but not following the repeated bout. Further, no overall changes in EMG distribution or mechanical hyperalgesia were found between bouts. These results indicate that muscle activation is unevenly distributed during the initial bout, possibly to maintain muscle function during localized mechanical fatigue. However, this does not reflect a strategy to confer protection during the repeated bout by activating undamaged/non-fatigued muscle areas.

Details

Original languageEnglish
JournalScandinavian Journal of Medicine and Science in Sports
Publication statusE-pub ahead of print - 30 Dec 2020