Slow component of O2 uptake during heavy exercise: adaptation to endurance training.
Seven untrained male subjects [age 25.6 +/- 1.5 (SE) yr, peak O2 uptake (VO2) 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 VO2 (end-exercise VO2-VO2 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-1.min-1 between minutes 10 and 20. After 2 wk of training, significant decreases in VO2 slow component, end-exercise VO2, blood lactate ([La-] and glucose concentrations, plasma Epi ([Epi]) and norepinephrine concentrations, ventilation (VE), and heart rate (HR) were observed (P < 0.05). Although the rapid attenuation of the VO2 slow component coincided temporally with reductions in plasma [Epi], blood [La-], and VE, the infusion of Epi after training significantly increased plasma [Epi] (delta 2.22 ng/ml), blood [La-] (delta 2.4 mmol/l) and VE (delta 10.0 l/min) without any change in exercise VO2. We therefore conclude that diminution of the VO2 slow component with training is attributable to factors other than the reduction in plasma [Epi], blood [La-] and VE.
Womack
C J
CJ
Exercise Physiology Laboratory, University of Virginia, Charlottesville 22903, USA.
Davis
S E
SE
Blumer
J L
JL
Barrett
E
E
Weltman
A L
AL
Gaesser
G A
GA
D000222:Adaptation, Physiological / Q000187:drug effects / Q000502:physiology*; D000328:Adult; D004837:Epinephrine / Q000008:administration & dosage; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D007262:Infusions, Intravenous; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000187:drug effects / Q000502:physiology*; D012129:Respiratory Function Tests; D013566:Sympathomimetics / Q000008:administration & dosage
D007773:Lactates; D013566:Sympathomimetics; D019344:Lactic Acid; D009638:Norepinephrine; D004837:Epinephrine