Objective: To describe the fat-oxidation rate in triathlon and different modalities of endurance cycling. Methods: 34 endurance athletes (15 male triathletes, 4 female triathletes, 11 road cyclists and 4 male mountain bikers) underwent a progressive cycloergometer test until exhaustion. Relative work intensity (VO2max), minimal lactate concentration (La-min), lactic threshold, individual lactic threshold (ILT), maximal fat-oxidation rate (Fatmax, Fatmax zone) and minimal fat-oxidation rate (Fatmin) were determined in each of the groups and were compared by means of one-way analysis of variance. Results: No significant differences were found for Fatmax, Fatmin or for the Fatmax zone expressed as fat oxidation rate (g/min). Intensities -20%, -10% and -5% Fatmax were significantly lower for mountain bikers with respect to road cyclists and female triathletes, expressed as % VO2max. Intensities 20%, 10% and 5% Fatmax were significantly lower for mountain bikers with respect to male triathletes and female triathletes, and for male triathletes in comparison with female triathletes, expressed as % VO2max. Lactic threshold and La-min did not show significant differences with respect to Fatmax. Lactic threshold was found at the same VO2max with respect to the higher part of the Fatmax zone, and La-min at the same VO2max with respect to the lower part of the Fatmax zone. Conclusions: The VO2max of Fatmax and the Fatmax zone may explain the different endurance adaptations of the athletes according to their sporting discipline. Lactic threshold and La-min were found at different relative work intensities with respect to those of Fatmax even though they belonged to the Fatmax zone.
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