Abstract
In order to determine the ventilatory threshold (VT) and the lactate threshold (LT)
in a reliable way, a new method is proposed and compared with conventional methods.
The new method consists of calculating the point that yields the maximal distance
from a curve representing ventilatory and metabolic variables as a function of oxygen
uptake (V̇O2) to the line formed by the two end points of the curve (Dmax method). Male cyclists
(n = 8) performed two incremental exercise tests a week apart. Ventilatory/metabolic
variables were measured and blood was sampled for later lactate measurement during
each workload and immediately after exercise. No statistical differences were observed
in the threshold values (expressed as absolute oxygen uptake; V̇O2) determined by the Dmax method and the conventional linear regression method (according
to O2 equivalent; EqO2) and venous blood at the onset of blood lactate (OBLA), while VT assessed with the
conventional linear method (according to the slope of CO2 output; Vslope) yielded significantly lower threshold values. Similar results were
obtained from the reproducibility test. Thus, the Dmax method appears to be an objective
and reliable method for threshold determination, which can be applied to various ventilatory
or metabolic variables yet yield similar results. The results also showed that breathing
frequency can be used to determine VT.
Key words
Ventilatory threshold - plasma lactate - oxygen uptake - breathing frequency
