Oxygen deficit is not affected by the rate of transition from rest to submaximal exercise

Five subjects cycled on an ergometer at power outputs corresponding to 20, 40, 60 and 80% of their maximal oxygen uptake (VO2 max). On one occasion the transition from rest to work was direct (D), while on the other occasion the power output was increased slowly (S) in a stepwise manner for 6-15 min prior to exercise at the predetermined intensity. Oxygen uptake (VO2) was measured, and O2 deficit and O2 debt were calculated. Oxygen deficit increased with the exercise intensities, the peak values being 2.1 +/- 0.2 and 1.9 +/- 0.1 litres (mean +/- SEM) at 80% of VO2 max after D and S respectively. No significant difference was observed in O2 deficit or O2 debt between D and S at any exercise intensity (P less than 0.05). The O2 debt was similar to the O2 deficit at 20, 40 and 60% of VO2 max but lower than the O2 deficit (P less than 0.05) at 80% of VO2 max. Femoral venous blood lactate remained unchanged at 20% of VO2 max but increased at the higher exercise intensities, reaching peak values of 7.6 +/- 0.6 and 7.4 +/- 1.1 mmol l-1 at 80% of VO2 max after D and S respectively. Blood lactate was not significantly different between D and S at any exercise intensity (P greater than 0.05). It is concluded that O2 deficit, O2 debt and blood lactate are not affected by the rate of transition from rest to submaximal exercise. The data contradict the hypothesis that O2 deficit is caused by an inadequate O2 transport at the onset of exercise.