Measurement of O2 deficit at the beginning of exercise and O2 debt after exercise

We measured the O₂ deficit at the beginning of exercise and the area under the curve (AUC) during the recovery‐period VO₂ (O₂ debt) (Figure 3 ).

O₂ deficit at the beginning of exercise and O₂ debt after exercise. VO₂, oxygen uptake; W‐up, warming up. (a) and (e): O₂ deficit at the beginning of exercise. (b): total warming up VO₂. (f): total exercise VO₂. (d) and (g): O₂ debt after exercise. (c): O₂ deficit presumed to occur during incremental load in RT. (c) was not actually measured as it is not measurable. Dotted line: theoretically speculated ATP requirement for the exercise.

As shown in Figure 3 A, the O₂ deficit at the beginning of the RT (a) was calculated by subtracting the AUC of the VO₂ curve over the 4 min warming‐up period (b) from the area of the rectangle whose height was the difference between rest VO₂ and VO₂ at the end of the 4 min warming‐up period and whose width was 4 min (a + b). We actually measured only A and D because the O₂ deficit, which was speculated to be generate during the incremental loading of RT, was not measurable (c).

The O₂ deficit during the submaximal CT (e), as shown in Figure 3 B, was calculated by subtracting the AUC of the VO₂ curve over the 6 min testing period (f) from the area of the rectangle whose height was the difference between rest VO₂ and VO₂ at the end of exercise and whose width was 6 min (e + f).

Post‐exercise O₂ debts (d and g in Figure 3 A and 3 B, respectively) were calculated by taking the exercise‐final VO₂ as the peak of the curve and integrating VO₂ from there until it decayed to the rest value. VO₂ at measurement was calculated without the use of moving averages. Finally, we calculated the ratio of O₂ debt to O₂ deficit (O₂ debt/O₂ deficit) for each exercise intensity. We calculated the percentage of the O₂ deficit [e/(e + f)] and that of the O₂ debt [g/(e + f)] in O₂ consumption during exercise in CT.