Wyatt, F. B., Autrey, L., Colson, S., Fitzgerald, Y., Sterba, T., & Heimdal, J. (2004). Fatigue occurs below VO2max and peak blood lactate at high intensity steady state. Medicine and Science in Sports and Exercise, 36(5), Supplement abstract 826.

This study determined if maximal oxygen utilization and peak lactate are fatigue factors associated with high-intensity steady state. Ss (N = 19) were measured for expired gases (VO2, VCO2, RER), time to exhaustion, blood lactate, and heart rate. Ss performed two tests to exhaustion on a cycle ergometer: 1) graded exercise test (GXT) and 2) performance exercise test (PXT). The GXT established peak capacities and ventilatory threshold. During PXT, Ss pedaled at a prescribed power calculated from the GXT as the median power between ventilatory threshold and volitional fatigue.

Ss exhibited steady state metabolism. The mean VO2 values (83.1% of maximum) during the PXT were below maximal values obtained during the GXT at volitional fatigue. It was concluded that volitional fatigue at high-intensity steady state is not a result of peak blood lactate or limited oxygen utilization.

Implication. High-intensity steady state exercise fatigue is not terminated because of blood lactate levels or limited oxygen utilization.

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