Double Anaerobic Threshold in Athletes

During an incremental cardiopulmonary exercise test (CPET) performed with a ramp protocol, it is very important to determine the anaerobic threshold, defined as the point at which the metabolism switches from being predominantly aerobic to also being anaerobic. The anaerobic threshold can be determined invasively, by identifying the increase in blood lactates with an arterial sampling, or, more commonly, non-invasively by three methods: the V-slope method, the ventilatory equivalents method and by using end-expiratory oxygen and carbon dioxide pressure (PETO2 and PETCO2 respectively). Normally, the anaerobic threshold is determined by the first method and the other two are used to confirm the value. The finding of different anaerobic threshold values using these three methods has been reported anecdotally in the past, while a prevalence of 11% in a healthy population has recently been described. Regular training, particularly that aimed at endurance sports, is able to shift the anaerobic threshold to higher exercise intensities. At present, the physiological reasons for the presence of a double threshold are unclear.

The aim of the study is to identify the anaerobic threshold by means of the V-slope method and by means of the ventilatory equivalents method in athletes who have performed an incremental ramp CPET at the laboratories of the investigating centres, to assess in how many athletes a double threshold is present and to try to interpret the physiological/ pathophysiological significance of this finding.

In this retrospective and prospective observational study, healthy male and female athletes who have had a cardiopulmonary test at our laboratories from 2007 to the present (retrospectively recruited) and prospectively recruited until the calculated sample size is reached will be enrolled.