Aim: 

The aim of the present study was to determine the salivary lactate threshold (LT) and to compare the anaerobic threshold (AT) values based on computerised calculations of different respiratory gas indices with those obtained from salivary lactate measurements in physically active subjects.

Methods: 

Twelve healthy male subjects (age, 20.1 4.9 years; body mass, 72.3 13.5 kg; body fat, 17.2 6.8%) performed a stepwise incremental cycle ergometer test until exhaustion, according to the Mader protocol. Respiratory gases were measured continuously, and salivary samples were drawn every 2 min for subsequent determinations of lactate concentration.

Results: 

At rest, HR was 106.3 12.5 bpm; VO₂, 12.8 6.5 ml/kg/min; the respiratory exchange ratio (RER), 0.83 0.04 VCO₂/VO₂; lactate, 0.28 0.1 mM. The AT was determined, based on RER > 1. Subjects reached the AT at the workload intensity of 148 37 watts, corresponding to 77.2 4.6% of the maximal intensity reached during the test. Within the AT, HR was 152.2 13.2 bpm; VO₂, 28.1 5.3 ml/kg/min; RER, 1.1 0.1 VCO₂/VO₂; lactate, 0.45 0.2 mM. At exhaustion HR was 176.9 14.8 bpm; VO₂, 37.7 7.4 ml/kg/min; RER, 1.3 0.02 VCO₂ /VO₂; lactate, 0.8 0.4 mM. As expected, the curve representing measurement data of salivary lactate run flat at the beginning until individuals reached the AT. Significant correlation between gas exchange indices and salivary lactate was found for VCO₂, RER and VE/VO₂.

Conclusion: 

Salivary LT correlated well with ventilatory and gas exchange-based determination of AT. Thefore, salivary lactate-based AT determination represents a reliable, non-invasive and simple method able to correctly predict the onset of anaerobic metabolism during exercise.