Abstract

Background. The ventilatory anaerobic thresholds are often evaluated during incremental tests (Winc), leading to exhaustion in less than 15 minutes.1 Main aim of this work is to assess the variability of the relationship between physiological responses during Winc and constant load exercise (Wcons). Methods. Thirteen elite mountainbikers performed a Winc with 26 W x min-1 steps and 5 min of warm up at 135 W. Mechanical power corresponding to 3.5 mM of blood lactate concentration ([LA]cap) was chosen for a Wcons with a 12 min target time. Results. Ten subjects were able to perform the task. At the end of . Wcons heart rate (HR ) and [LA]cap were similar to those found at the end of Winc but O2 uptake (V.O2) and ventilation (V.e) were significantly lower (­8.0% and ­11.8%, respectively). During . Wcons, HR and V.e increased from 6th to 12th min and [LA]cap from 4th to 12th but V.O2 did not change. All physiological variables at the end of Wcons were computed as a fraction of the same variables at the end of .Winc. These fractions had larger SDs for [LA]cap (0.43) than for V.e (0.012), V.O2 (0.06) or HR (0.03). [LA]cap increased and end-tidal pCO2 (PETCO2) decreased almost linearly during Wcons. The SD of (PETCO2) was about 3 mmHg and the intersubjective variabilities of (PETCO2) and [LA]cap were unrelated. Conclusions. In well-trained endurance athletes 1) the relationship between physiological variables measured during Winc, and Wcons do not seem very strict, 2) the V.O2 slow component during heavy work is insignificant, 3) the respiratory compensation to metabolic acidosis is variable. Verf.-Referat