Frequency of the VO2max plateau phenomenon in world-class cyclists

Abstract

We aimed to determine the frequency of the VO↓2max plateau phenomenon in top-level male professional road cyclists (n = 38; VO↓2max [mean ± SD]: 73.5 ± 5.5 ml · kg↑-1 · min↑-1) and in healthy, sedentary male controls (n = 37; VO↓2max: 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 VO↓2max plateau phenomenon was defined as an increase in two or more consecutive 1-min mean VO↓2 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 [HR↓max], 82 %; BLa> 8 mmol · l↑-1, 84 %). However, the proportion of cyclists attaining a VO↓2max plateau was considerably lower, i.e., 47 %. The majority of controls met the criteria for maximal exercise effort (RER > 1.1, 100 %; predicted HR↓max, 68 %; BLa> 8 mmol · l↑-1, 73 %), but the proportion of these subjects with a VO↓2max 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 VO↓2max plateau phenomenon are those who perform an absolute maximum effort or there are additional distinctive features associated with this phenomenon.