Effects of high-intensity isokinetic exercise on salivary cortisol in athletes with different training schedules: relationships to serum cortisol and lactate

Physical exercise is associated with increases of serum and salivary levels of cortisol. The concomitant increase in serum lactate has been implicated as one of the mechanisms responsible for adrenocortical activation. We evaluated the responses of serum lactate and serum and salivary cortisol to an acute bout of high-intensity isokinetic exercise in eleven non-competitive and twenty competitive athletes (NCA and CA, respectively). The latter group was composed of endurance- and power-trained athletes (EA and PA, respectively). Aims of the study were to determine interindividual differences in the lactate and cortisol responses as a function of type and intensity of training and to search for relationships both between lactate and cortisol production and between serum and salivary cortisol levels. The isokinetic exercise test elicited significant cortisol and lactate responses. No difference was evident in the lactate responses between NCA and CA, while the PA showed a higher response during and after the exercise in comparison to EA (peak levels immediately after the exercise: PA 15.0 +/- 1.5 mmol/l vs. EA 11.1 +/- 2.6 mmol/l, p < 0.01). Serum cortisol was higher in the CA in comparison to the NCA group at 30 and 120 minutes after the termination of the exercise, while no differential response was evident between EA and PA groups. Salivary cortisol response was higher in the CA group in comparison to NCA immediately after the exercise and at 90 and 120 minutes after the termination and was higher in PA in comparison to EA at 60, 90, and 120 minutes after the termination (peak levels at 60 minutes: PA 51.2 +/- 18.5 nmol/l vs. EA 27.5 +/- 20.8 nmol/l, p < 0.05). No significant correlations were found between serum or salivary cortisol and lactate levels. The relationship between serum and salivary cortisol was markedly non-linear, the slope of the serum-saliva regression line being lower for serum cortisol concentrations over 500 nmol/l than for concentrations below that value (0.019 and 0.037, respectively, p < 0.01). We have confirmed in this particular setting the existence of an important adrenocortical response that can be reliably and non invasively assessed by a serial saliva sampling and have supported the concept that cortisol and lactate responses to a high-intensity isokinetic exercise are independent. The interindividual differences in cortisol changes are likely to be related to the training status and mode as well as to the correspondence between the evaluation protocol and the discipline individually performed.