Physiological and Metabolic Responses of Triathletes to a Simulated 30-min Time-Trial in Cycling at Self-Selected Intensity

Abstract

The aim of this study was to investigate the metabolic and physiological responses to a laboratory-based simulated 30-min individual time-trial (ITT₃₀) in cycling at a self-selected intensity. Twelve experienced triathletes (n = 4 women) performed a progressive incremental exercise test on a cycle ergometer to determine V˙O₂max (52 ± 5 ml × min^-1 × kg^-1), maximum power output (300 ± 12 W), and the second ventilatory threshold. Then, the subjects completed an ITT₃₀ at self-selected work intensity on a stationary ergometer equipped with the SRM Training System. In all subjects, during the ITT₃₀, heart rate and minute ventilation increased (p < 0.05) progressively whereas oxygen consumption and power output remained unchanged. Triathletes rode at consistent pacing corresponding to their highest steady state of blood lactate concentration that increased by no more than 1.0 mmol × l^-1 during the final 20-min of ITT₃₀. The self-selected intensity of triathletes during ITT₃₀ represented 88 ± 5 % (mean ± SD) of V˙O₂max and was not significantly different to the energy demand corresponding to the second ventilatory threshold (84 ± 5 % of V˙O₂max). Our data suggest that ITT₃₀ at a self-selected intensity is a good predictor of individual endurance capacity and may be used to estimate racing pace for training purposes. This performance test for the identification of the exercise intensity that demarcate ”steady state” is less troublesome than some of the traditional methods, limiting testing to a single session.

Key words

Blood lactate - heart rate - perceived exertion - pulmonary gas exchange

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