The variability of repeated measurements of oxygen debt in man following a maximal treadmill exercise

Abstract

This study was designed to assess the contribution of the intraindividual variability of oxygen debt (O₂ debt) to the range (β5–248 ml/kg) reported for human subjects following exercise which required maximal oxygen uptake (maxV̇O₂). On 5–7 occasions 6 physical education students exercised at three progressive continuous workloads on a treadmill for 15–19 minutes and the O₂ debt measured. Similarly 5 ice hockey forwards, 5 cross-country skiers, 5 track runners and 5 non-athletic control subjects were tested on one occasion. In every case the final exercise elicited a heart rate > 180 beats/min. and a plasma lactate > 70 mg/100 ml. The mean maxV̇O₂ and O₂ debts for the physical education students ranged from 51.9–68.0 ml/kg·min and 81.7–178.3 ml/kg respectively; the smallest O₂ debt recorded was 43 ml/kg and the largest was 228.9 ml/kg. The intraindividual variability for O₂ debt was greater than that for maxV̇O₂ (p < 0.01), the mean individual coefficients of variation being 21.3 and 9.0% respectively. The cross-country skiers and track runners demonstrated greater maxV̇O₂ values (p < 0.05) than the control group, but no significant difference could be shown between any of the groups for O₂ debt. Thus training did not appear to be a major factor contributing to the wide diversity seen in O₂ debts. The variability of the data clearly demonstrates that extreme caution must be exercised in the interpretation of a single measurement of O₂ debt, especially when studies are carried out to examine either the mechanism or magnitude of this parameter.