Oxygen debt, lactate, pyruvate, and excess lactate after muscular work

The effect of activity of large muscles at different work intensities on oxygen debt and on lactate, pyruvate, and excess lactate during work and recovery has been studied. Data are presented for the more extensive testing program conducted on one research subject. Four series of experiments were conducted with the subject riding a Krogh bicycle ergometer at work rates of 300, 700, 1,100, and 1,600 kg-m/min. O 2 debts were contracted at each of the work levels, but no appreciable rises in excess lactate and only small rises in total lactate were found at the lower two intensities. When a critical level of work (O 2 uptake of 1.5 liters/min with an accompanying debt of 1.5 liters) was surpassed there was a rapid rise in O 2 debt values which was parallel to rises in O 2 equivalence values for both total lactate and excess lactate. At all work levels the O 2 debt surpassed in quantity the O 2 equivalents of the maximum increases in total lactate and, to an even greater extent, the O 2 equivalents of excess lactate. This finding supports the theory of separate alactacid and lactacid portions of the O 2 debt. No conclusions could be drawn concerning the rates or methods of payment of the two portions. Submitted on October 23, 1961