Neural adaptations to fatigue: Implications for muscle strength and training

D. A. Gabriel, J. R. Basford, K. N. An

Research output: Contribution to journalArticle

30 Scopus citations

Abstract

Purpose: This paper investigates the neural mechanisms responsible for the increase in strength that occurs during serial isometric contractions. Methods: A three-session design was used. Thirteen subjects (N = 13) were asked to perform five maximal isometric elbow extension strength trials to serve as baseline. After a 5-min rest, the subjects were administered a 30-trial fatigue protocol. This process was repeated two more times at 2-wk intervals. Elbow extension torque and surface electromyography (EMG) of the triceps and biceps brachii were monitored concurrently. The criterion measures were elbow extension torque, root-mean-square EMG amplitude, and mean power frequency (MPF). Results: Intraclass reliability ranged from good to excellent. Within each experimental session, the fatigue protocol resulted in a decrease in maximal isometric elbow extension torque as well as biceps and triceps EMG amplitude and MPF (P < 0.05). However, the mean of the 30 trials and the magnitude of the linear decrease in elbow extension torque increased across the three sessions (P < 0.05). Biceps and triceps EMG amplitude increased and MPF decreased as the number of sessions increased (P < 0.05). Conclusions: These findings suggest that the fatigue protocol served as a training stimulus to down regulate motor-unit firing frequency.

Original languageEnglish (US)
Pages (from-to)1354-1360
Number of pages7
JournalMedicine and Science in Sports and Exercise
Volume33
Issue number8
StatePublished - 2001
Externally publishedYes

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Keywords

  • Antagonist coactivation
  • Elbow extension
  • Electromyography
  • Isometric contraction
  • Motor-unit activity

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Public Health, Environmental and Occupational Health
  • Physical Therapy, Sports Therapy and Rehabilitation

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