Saliva electrolytes as a useful tool for anaerobic threshold determination

The purpose of the present study was to determine the anaerobic threshold by analysis of changes in saliva composition during an incremental exercise test on a cycle ergometer. Thirteen healthy males underwent a submaximal test with an initial load of 50 W and load increases of 50 W per 3 min, until capillary blood lactate exceeded 4 mmol · l^–1. A maximal test for maximum O₂ uptake (VO_2max) determination (initial load of 100 W and load increases of 50 W per 2 min) was also performed. Saliva and blood samples were obtained only in the submaximal test. Saliva threshold (Th_sa) was defined as the point at which the first increase in either Cl^– or Na⁺ occurred. Catecholamine threshold (Th_ca) was defined as the point at which a nonlinear increase occurred in either adrenaline or noradrenaline. The lactate (Th_la) and ventilatory (Th_ve) thresholds were determined according to published criteria. No significant differences were found between Th_sa values and the other methods of threshold determination. A high correlation was found between Th_sa and Th_la (r = 0.82, P < 0.01), and Th_sa and Th_ca (r = 0.75, P < 0.05). These results support the validity of Th_sa as a new method for noninvasive determination of the anaerobic threshold.