Nielsen, L., Garver, M. J., Dickinson, J. M., Campbell, D. S., & Papadopoulos, C. (2006). Physiological and metabolic responses during two self-selected cycling time trials. Medicine and Science in Sports and Exercise, 38(5), Supplement abstract 2595.

The purpose of this study was to investigate physiological and metabolic responses during two self-selected cycling time trials and to compare these responses to three lactate threshold definitions (1.0 mmol above resting blood lactate concentration; fixed blood lactate of 4.0 mmol; and the Dmax method). Trained, competitive cyclists (N = 5) served as Ss. Ss completed three testing protocols, each separated by at least one week. The first test consisted of an incremental maximal exercise test on a cycle ergometer. A self-paced 20 kilometer and a 40 kilometer time trials were completed on the other two occasions. Power output, heart rate, and blood lactate responses were measured.

Power output, heart rate, and the mean lactate concentration during the 20 kilometer time-trial were significantly higher than during the 40 kilometer time-trial. Mean lactate concentration during the 20 kilometer time-trial was significantly higher than those at the three lactate threshold definitions.

Implication. Results at different lactate thresholds are not representative of responses during two different self-selected time trials.

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