Assessment of double anaerobic threshold in trained subjects

Abstract

Background: Regular training increases Anaerobic Threshold (AT) and improves ventilatory efficiency during exercise. A presence of a Double AT (DT), a delayed ventilatory response to CO₂ increase during exercise, was described in some healthy subjects, and may represent a favorable adaptation mechanism for trained subjects. The aim was to investigate the prevalence of DT in trained individuals and the relationship between training and ventilatory efficiency.

Methods: Maximal CardioPulmonary Exercise Test (CPET) of trained subjects were analysed for assessment of AT with the metabolic (V-slope analysis, MetAT) and the ventilatory methods (end-tidal and ventilatory equivalent methods, VentAT). Trained subjects were assigned to groups DT+ or DT- based on the presence/absence of DT, respectively. Trained subjects were also classified by type of sport practiced. Determinants of ventilatory efficiency were assessed at adjusted multivariate regression analysis.

Results: DT was identified in 52 cases out of 205 enrolled (25.4%). No differences by age, sex, body mass index and peak CPET parameters were observed between groups. DT+ subjects had a longer duration and greater ΔVO₂ values of isocapnic buffering period. Ventilatory efficiency was negatively associated (better values) with the presence of a DT (p = 0.017). Type of sport practiced did not influence the prevalence of DT nor the ventilatory efficiency response.

Conclusion: DT was found in 25.4% of trained people. The presence of DT is not influenced by the type of training and is not related to maximal aerobic capacity; however, subjects with a DT have a greater isocapnic buffering period and a better ventilatory efficiency.

Keywords: anaerobic threshold; cardiopulmonary exercise test; isocapnic buffering period; training; ventilatory efficiency.