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

Patricio A. Pincheira, Eduardo Martinez-Valdes, Rodrigo Antonio Guzmán Venegas, Deborah Falla, Marta I. Garrido, Andrew G. Cresswell, Glen A. Lichtwark

Research output: Contribution to journalArticlepeer-review

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.

Original languageEnglish
Pages (from-to)799-812
Number of pages14
JournalScandinavian Journal of Medicine and Science in Sports
Volume31
Issue number4
DOIs
StatePublished - Apr 2021

Bibliographical note

Funding Information:
The authors would like to thank ?Fondo de Ayuda a la Investigaci?n (FAI: INV-IN-2017-01), Universidad de los Andes, Santiago, Chile? for its support to this research. The authors would like also thank to Oscar Valencia, Felipe Palma, Gunther Redenz and Carlos de la Fuente for their help during data collection and processing.

Publisher Copyright:
© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Keywords

  • exercise-induced muscle damage
  • high-density electromyography
  • medial gastrocnemius
  • statistical parametric mapping

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