Slow component of O2 uptake during heavy exercise: Adaptation to endurance training

C. J. Womack, S. E. Davis, J. L. Blumer, E. Barrett, A. L. Weltman, G. A. Gaesser

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113 Scopus citations


Seven untrained male subjects [age 25.6 ± 1.5 (SE) yr, peak O2 uptake (V̇O2) 3.20 ± 0.19 l/min] trained on a cycle ergometer 4 days/wk for 6 wk, with the absolute training workload held constant for the duration of training. Before and at the end of each week of training, the subjects performed 20 min of constant-power exercise at a power designed to elicit a pronounced slow component of V̇O2 (end-exercise V̇O2 - V̇O2 at minute 3 of exercise) in the pretraining session. An additional 20-min exercise bout was performed after training at this same absolute power output during which epinephrine (Epi) was infused at a rate of 100 ng · kg- · min-1 between minutes 10 and 20. After 2 wk of training, significant decreases in V̇O2 slow component, end-exercise V̇O2, blood lactate ([La-] and glucose concentrations, plasma Epi ([Epi]) and norepinephrine concentrations, ventilation (V̇E), and heart rate (HR) were observed (P < 0.05). Although the rapid attenuation of the V̇O2 slow component coincided temporally with reductions in plasma [Epi], blood [La-], and V̇E, the infusion of Epi after training significantly increased plasma [Epi] (Δ2.22 ng/ml), blood [La-] (Δ2.4 mmol/l) and V̇E (Δ10.0 l/min) without any change in exercise V̇O2. We therefore conclude that diminution of the V̇O2 slow component with training is attributable to factors other than the reduction in plasma [Epi], blood [La-] and V̇E.

Original languageEnglish (US)
Pages (from-to)838-845
Number of pages8
JournalJournal of Applied Physiology
Issue number3
StatePublished - 1995
Externally publishedYes


  • catecholamines
  • epinephrine
  • glucose
  • heart rate
  • lactate
  • muscle fiber type
  • norepinephrine
  • pulmonary gas exchange
  • ventilation

ASJC Scopus subject areas

  • General Medicine


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