Effect of varied lactate levels on bicycle ergometer performance

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Abstract
Six subjects exercised on the bicycle ergometer on three separate occasions. Each of the three tests that each subject performed consisted of a 5-min work period [95% maximal O2 uptake (VO2max)], followed by a 4-min rest period, and then a performance task to exhaustion (90% VO2max). Each test varied only in the inspired O2 fraction (FIO2) (16, 21, or 60% O2 in N2) that was breathed during the initial 5-min work period. The remainder of each test was carried out with 21% O2. Total power output was the same for each subject during the initial 5-min work bout. However, the varied FIO2 breathed during this initial work period resulted in significantly different mean blood lactate (and H+) concentrations at the start of the performance task (P less than 0.05). Mean performance time was significantly greater (P = 0.04) after the hyperoxic treatment (14.8 min) when compared with the hypoxic (9.1 min). Mean blood lactate and H+ levels at exhaustion were not significantly different. These data demonstrate that when various blood (or muscle) lactate and H+ levels were induced on different occasions by leg muscles, the subsequent performance of those muscles was significantly affected.

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