Transcutaneous pco₂-Monitoring for the Evaluation of the Anaerobic Threshold

Abstract

The monitoring of transcutaneous pco₂ (pco₂(tc)) is an alternative to the invasive determination of the anaerobic threshold by analysis of arterial lactate concentration or to the uncomfortable determination of the ventilatory threshold. We compared the threshold determination by pco₂(tc)-monitoring to the 4 mmol /1 lactate threshold and to the ventilatory threshold (point where the ventilatory equivalent of oxygen started to increase continuously) in 15 athletes during cycle exercise. The first distinct deflection point in the pco₂(tc) time course after the start of exercise was chosen to indicate the anaerobic threshold. The mean threshold determined by pco₂(tc) occurred at the same workload as the ventilatory threshold but at a lower workload than the lactate threshold. In spite of the good correspondence in the respective means there was a wide range of individual differences between the pco₂(tc) derived thresholds and both reference thresholds. Thus, looking at an individual, the continuous monitoring of the pco₂(tc) does not provide reliable data on the occurrence of the transition from aerobic to anaerobic metabolism.

Key words

Transcutaneous pco₂ - anaerobic threshold - lactate threshold - ventilatory threshold - respiratory compensation