Aim: 

Alactic (AlacDO2) and lactic (LacDO2) O2 deficit were estimated during supramaximal (SM) cycling exercise performed at 120% V'O2max in 14 male subjects. Breath-by-Breath V'O2 and net peak lactate concentration ([La]p) were measured during and after three SM tests, respectively.

Methods and Results: 

Total DefO2 (TDO2) was obtained by subtracting the volume of O2 consumed during the test (òV'O2) (average of three runs) from the total metabolic energy (in litre of O2) required to complete the exercise. LacDO2 was then computed as the difference between: 1) the volume of O2 that the subject would have consumed if he had hypothetically attained a V'O2 equal to 120% V'O2max following a kinetics identical to that prevailing at moderate intensity exercise and; 2) òV'O2. Finally, AlacDO2 was obtained as TDO2 - LacDO2. TDO2, LacDO2 and AlacDO2 amounted to 77.6 ± 14.5 mlO2 kg-1, 39.1 ± 15.1 mlO2 kg-1, 38.5 ± 7.6 mlO2 kg-1, respectively. LacDO2 divided by net [La]p was 3.4 mlO2 kg-1 mM-1, a value not significantly different from the metabolic energy equivalent of lactate in vivo (eqLa).

Conclusions: 

These results suggest that LacDO2 can be estimanted by multiplying eqLa times net [La]p and they do not contradict the view that bioenergetics processes may be represented by a three-component hydraulic model wherein lactic acid production and lactic metabolic power are proportional to the difference between the levels of the vessels representing lactic capacity and [PCr+ATP].