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Related Experiment Videos

Muscle substrate utilization and lactate production.

J D MacDougall1, S Ray, D G Sale

  • 1Department of Kinesiology, McMaster University, Hamilton, ON L8S 4K1 Canada.

Canadian Journal of Applied Physiology = Revue Canadienne De Physiologie Appliquee
|June 11, 1999
PubMed
Summary
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Muscle biopsies in bodybuilders revealed that phosphocreatine (PCr) depletion and increased acidity contribute to fatigue during arm-curl exercises. Energy stores and lactate levels were analyzed post-exercise.

Area of Science:

  • Exercise Physiology
  • Sports Science
  • Biochemistry

Background:

  • Understanding the metabolic demands of resistance training is crucial for optimizing performance and recovery in athletes.
  • Muscle fatigue during intense exercise is a complex phenomenon influenced by various biochemical factors.

Purpose of the Study:

  • To investigate the changes in muscle energy stores and metabolites during a typical arm-curl resistance training session.
  • To identify the key biochemical factors contributing to muscle fatigue in bodybuilders.

Main Methods:

  • Biceps muscle biopsies were obtained from 8 bodybuilders during an arm-curl exercise protocol at 80% of one-repetition maximum (1-RM).
  • Analysis of phosphocreatine (PCr), muscle glycogen, and lactate concentrations after one and three sets of exercise.

Related Experiment Videos

  • Assessment of hydrogen ion (H+) concentration changes.

    • Main Results:

    • Significant decreases in phosphocreatine (PCr) by 62% and glycogen by 12% after one set, and by 50% and 24% respectively after three sets.
    • Muscle lactate levels increased to 91 mmol/kg after one set and 118 mmol/kg after three sets.
    • Muscle fatigue was associated with decreased PCr and increased H+ after the first set, and decreased H+ in subsequent sets.

    Conclusions:

    • Resistance exercise significantly depletes muscle PCr and glycogen stores, impacting energy availability.
    • Increased acidity (H+) and reduced PCr are primary contributors to muscle fatigue during intense resistance exercise.
    • Metabolic shifts occur during repeated sets, influencing the mechanisms of fatigue.