Progressive effect of endurance training on metabolic adaptations in working skeletal muscle

Am J Physiol. 1996 Feb;270(2 Pt 1):E265-72. doi: 10.1152/ajpendo.1996.270.2.E265.


We investigated the hypothesis that a program of prolonged endurance training, previously shown to decrease metabolic perturbations to acute exercise within 5 days of training, would result in greater metabolic adaptations after a longer training duration. Seven healthy male volunteers [O2 consumption = 3.52 +/- 0.20 (SE) l/min] engaged in a training program consisting of 2 h of cycle exercise at 59% of pretraining peak O2 consumption (VO2peak) 5-6 times/wk. Responses to a 90-min submaximal exercise challenge were assessed pretraining (PRE) and after 5 and 31 days of training. On the basis of biopsies obtained from the vastus lateralis muscle, it was found that, after 5 days of training, muscle lactate concentration, phosphocreatine (PCr) hydrolysis, and glycogen depletion were reduced vs. PRE (all P < 0.01). Further training (26 days) showed that, at 31 days, the reduction in PCr and the accumulation of muscle lactate was even less than at 5 days (P < 0.01). Muscle oxidative potential, estimated from the maximal activity of succinate dehydrogenase, was increased only after 31 days of training (+41%; P < 0.01). In addition, VO2peak was only increased (10%) by 31 days (P < 0.05). The results show that a period of short-term training results in many characteristic training adaptations but that these adaptations occurred before increases in mitochondrial potential. However, a further period of training resulted in further adaptations in muscle metabolism and muscle phosphorylation potential, which were linked to the increase in muscle mitochondrial capacity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological*
  • Adult
  • Citric Acid / metabolism
  • Energy Metabolism
  • Glucose / metabolism
  • Glucose-6-Phosphate / metabolism
  • Glycogen / metabolism
  • Humans
  • Lactic Acid / metabolism
  • Male
  • Muscle, Skeletal / enzymology
  • Muscle, Skeletal / metabolism*
  • Phosphates / metabolism
  • Physical Education and Training*
  • Physical Endurance*
  • Pyruvic Acid / metabolism
  • Triglycerides / metabolism


  • Phosphates
  • Triglycerides
  • Citric Acid
  • Lactic Acid
  • Glucose-6-Phosphate
  • Pyruvic Acid
  • Glycogen
  • Glucose