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The maximally attainable V̇ o 2 during exercise in humans: the peak vs. maximum issue

2003; American Physiological Society; Volume: 95; Issue: 5 Linguagem: Inglês

10.1152/japplphysiol.00024.2003

8750-7587

Jonathan Day, Harry B. Rossiter, Edward M. Coats, A. Skasick, Brian J. Whipp,

Muscle activation and electromyography studies

The quantification of maximum oxygen uptake (V̇o 2 max ), a parameter characterizing the effective integration of the neural, cardiopulmonary, and metabolic systems, requires oxygen uptake (V̇o 2 ) to attain a plateau. We were interested in whether a V̇o 2 plateau was consistently manifest during maximal incremental ramp cycle ergometry and also in ascertaining the relationship between this peak V̇o 2 (V̇o 2 peak ) and that determined from one, or several, maximal constant-load tests. Ventilatory and pulmonary gas-exchange variables were measured breath by breath with a turbine and mass spectrometer. On average, V̇o 2 peak [3.51 ± 0.8 (SD) l/min] for the ramp test did not differ from that extrapolated from the linear phase of the response in 71 subjects. In 12 of these subjects, the V̇o 2 peak was less than the extrapolated value by 0.1-0.4 l/min (i.e., a “plateau”), and in 19 subjects, V̇o 2 peak was higher by 0.05-0.4 l/min. In the remaining 40 subjects, we could not discriminate a difference. The V̇o 2 peak from the incremental test also did not differ from that of a single maximum constant-load test in 38 subjects or from the V̇o 2 max in 6 subjects who undertook a range of progressively greater discontinuous constant-load tests. A plateau in the actual V̇o 2 response is therefore not an obligatory consequence of incremental exercise. Because the peak value attained was not different from the plateau in the plot of V̇o 2 vs. work rate (for the constant-load tests), the V̇o 2 peak attained on a maximum-effort incremental test is likely to be a valid index of V̇o 2 max , despite no evidence of a plateau in the data themselves. However, without additional tests, one cannot be certain.