Margaria, R., Edwards, H. T., & Dill, D. B. (1933). The possible mechanism of contracting and paying the O2 debt and the rate of lactic acid in muscular contraction. American Journal of Physiology, 106, 689-715.

This abstract is an interpretation for swimming coaches when talking about ultra-short training in the controversial USRPT format.

Traditional swimming coaches often refuse to accept the possibility that lactate does not accrue in a training set no matter what its form or duration. It is often argued that "lactate tolerance" sets involve high-intensity swimming and they do cause lactate to accrue. Thus, USRPT's claim of no to low lactate build-up in a set of repetitions is not "believed". A very seldom referenced study by Margaria, Edwards, and Dill (1933), showed that no extra lactic acid appears in the blood after exercise involving an oxygen debt of less than 2.5 liters. When exercise requires a larger amount of oxygen, lactic acid accumulates at the rate of 7 g for each liter of additional oxygen debt. USRPT repetitions are short enough to limit an oxygen debt to be in the vicinity of 2.5 liters or less. Consequently, that explains why lactic acid does not accumulate in ultra-short and more specifically, USRPT. Occasionally, the oxygen debt of a USRPT repetition slightly exceeds 2.5 liters, particularly nearing the end of a set when avoidance of failures starts to be an aim of the swimmer. That accounts for the very slight fluctuations in lactate concentrations (see Astrand et al., 1960) throughout an ultra-short repetition exercise. In practical terms, lactate is not problematical in USRPT because it does not accrue during a full set of repetitions. The brevity of the work periods and the limited demands for oxygen debts in the region of 2.5 liters or more prevent lactate accumulation.

Reference. Astrand, I., Astrand, P-O., Christensen, E. H., & Hedman, R. (1960). Intermittent muscular work. Acta Physiologica Scandinavica, 48, 448-453.

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