Blood Flow and Metabolic Control at the Onset of Heavy Exercise

抄録

The rate of increase in oxygen uptake (VO₂) at the onset of a bout of heavy exercise is faster if it is preceded by a similar bout of heavy exercise. We tested the hypothesis during heavy leg exercise that leg blood flow (LBF) and VO₂ would both be elevated during the adaptive phase. On three separate days, six healthy young men completed two bouts of 6-minutes of knee extension / flexion exercise at about 85% VO₂peak separated by 5-minutes 0-watt exercise on an electrically braked ergometer. LBF was determined by Doppler ultrasound. In the second exercise bout, LBF and VO₂ were significantly elevated in the baseline before exercise and throughout the exercise. Both the mean response time (time to 63% of difference between baseline and calculated end value) and the difference in VO₂ between minutes 3 and 6 of exercise indicated significantly faster attainment of the end exercise value in the second heavy exercise bout. These data showing the elevated LBF in the second bout of heavy exercise support the link between O₂ delivery and the adaptation of oxidative metabolism at the onset of heavy exercise.