The anaerobic threshold of lactate and its relation with salivary proteins and electromyographic activity was investigated under conditions of physical stress. Twelve cyclists (age: 22.6 ± 3.5; height: 1.78 ± 0.2 m; weight: 71.8 ± 5.76 kg) were subjected to a progressive effort test on a cycloergometer.  Blood and saliva samples were taken during the test and the electric signals captured from the vastus lateralis and vastus medialis muscles of both legs. Blood lactate, salivary total protein concentration and its electrophoretic profile, salivary alpha-amylase and muscle electric activity were also measured. The lactate anaerobic thresholds were found to be closely correlated with the total protein (r=0.97, p<0,05) and electromyographic thresholds of the right vastus lateralis muscle(r=0,89, p<0,05). The protein profile was not altered by the exercise except for the salivary alpha-amylase polypeptide, whose concentration increased. The densitometric results of the alpha-amylase band were plotted in relation to the work load, showing the occurrence of a threshold. Exercise-induced stress was found to alter the concentration of lactate, salivary total protein and alpha-amylase activity during and after the exercise. These data suggest that the concentrations of salivary total protein and salivary alpha-amylase are good predictors of the anaerobic threshold (AT) as well as indicators of physical stress.