We aimed to determine the frequency of the V·O2max plateau phenomenon in top-level male professional road cyclists (n = 38; V·O2max [mean ± SD]: 73.5 ± 5.5 ml · kg-1 · min-1) and in healthy, sedentary male controls (n = 37; V·O2max: 42.7 ± 5.6 ml · kg-1 · min-1). All subjects performed a continuous incremental cycle-ergometer test of 1-min workloads until exhaustion. Power output was increased from a starting value of 25 W (cyclists) or 20 W (controls) at the rate of 25 W · min-1 (cyclists) or 20 W · min-1 (controls) until volitional exhaustion. We measured gas-exchange and heart rate (HR) throughout the test. Blood concentrations of lactate (BLa) were measured at end-exercise in both groups. We defined maximal exercise exertion as the attainment of a respiratory exchange rate (RER) = 1.1; HR > 95 % age-predicted maximum; and BLa > 8 mmo · l-1. The V·O2max plateau phenomenon was defined as an increase in two or more consecutive 1-min mean V·O2 values of less than 1.5 ml · kg-1 · min-1. Most cyclists met our criteria for maximal exercise effort (RER > 1.1, 100 %; 95 % predicted maximal HR [HRmax], 82 %; BLa > 8 mmol · l-1, 84 %). However, the proportion of cyclists attaining a V·O2max plateau was considerably lower, i.e., 47 %. The majority of controls met the criteria for maximal exercise effort (RER > 1.1, 100 %; predicted HRmax, 68 %; BLa > 8 mmol · l-1, 73 %), but the proportion of these subjects with a V·O2max plateau was only 24 % (significantly lower proportion than in cyclists [p < 0.05]). Scientists should consider 1) if typical criteria of attainment of maximal effort are sufficiently stringent, especially in elite endurance athletes; and 2) whether those humans exhibiting the V·O2max plateau phenomenon are those who perform an absolute maximum effort or there are additional distinctive features associated with this phenomenon.
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