Motor unit conduction velocity during sustained contraction after eccentric exercise

Research output: Contribution to journalArticle

Authors

  • Nosratollah Hedayatpour
  • Deborah Falla
  • Lars Arendt-Nielsen
  • Carolina Vila-Chã
  • Dario Farina

Colleges, School and Institutes

External organisations

  • Centre for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.

Abstract

BACKGROUND: Eccentric contractions induce muscle fiber damage that is associated with a decreased capacity to generate voluntary force and increased fiber membrane permeability. Changes in fiber membrane permeability results in cell depolarization that is expected to have an effect on the action potential propagation velocity of the muscle fibers.

PURPOSE: The aim of the study was to investigate the action potential propagation velocity in individual motor units before and 24 and 48 h after eccentric exercise.

METHODS: Multichannel surface and fine-wire intramuscular EMG signals were concurrently recorded from two locations of the right vastus medialis muscle of 10 healthy men during 60-s isometric contractions at 10% and 30% of the maximal force.

RESULTS: The maximal force decreased by 26.1 ± 16.1% (P < 0.0001) at 24 h and remained reduced by 23.6 ± 14.5% (P < 0.0001) 48 h after exercise with respect to baseline. With respect to baseline, motor unit conduction velocity decreased (P < 0.05) by (average over 24 and 48 h after exercise) 7.7 ± 2.7% (10% maximal voluntary contraction (MVC), proximal), 7.2 ± 2.8% (10% MVC, distal), 8.6 ± 3.8% (30% MVC, proximal), and 6.2 ± 1.5% (30% MVC, distal). Moreover, motor unit conduction velocity decreased over time during the sustained contractions at faster rates when assessed 24 and 48 h after exercise with respect to baseline for both contraction forces and locations (P < 0.05).

CONCLUSIONS: These results indicate that the electrophysiological membrane properties of muscle fibers are altered by exercise-induced muscle fiber damage.

Details

Original languageEnglish
Pages (from-to)1927-33
Number of pages7
JournalMedicine and Science in Sports and Exercise
Volume41
Issue number10
Publication statusPublished - Oct 2009

Keywords

  • Action Potentials, Adult, Analysis of Variance, Electromyography, Exercise, Humans, Isometric Contraction, Male, Muscle Fibers, Skeletal, Muscle, Skeletal, Young Adult, Journal Article, Research Support, Non-U.S. Gov't