Influence of short-term cycling on salivary cortisol levels.

The purpose of this study was to examine the response of salivary cortisol to acute exercise, and to directly compare serum and salivary cortisol responses to sub-maximal exercise. Eight males volunteered to participate in the study. On three separate days following the assessment of maximum oxygen uptake (VO2max), the subjects exercised on a bicycle ergometer at 75% of their VO2max for 30 min. On a fourth day, the subjects rested quietly, and this served as a control condition. On each of these days, five serial samples of either blood, saliva, or both blood and saliva were obtained at 15-min intervals before, during, and after exercise. Submaximal exercise elicited a significant (P less than 0.05) increase in both serum and salivary cortisol above resting control levels immediately and 15 min following exercise under all exercise conditions. In addition, significant correlations (all P less than 0.01) were observed between serum and salivary cortisol at each of the five sampling periods. The correlations were as follows: r = 0.89 at -15 min; r = 0.60 at 0 min; r = 0.72 at 15 min; r = 0.90 at 30 min; and r = 0.93 after 15 min of recovery. Saliva was also obtained immediately before and 5 min following the assessment of VO2max, and there was a significant (P less than 0.05) increase in post-VO2max test (1.07 +/- 0.12 micrograms X dl-1) compared to pre-test (0.71 +/- 0.06 micrograms X dl-1) salivary cortisol levels. The results of this experiment indicate that salivary cortisol is a potentially valid measure of serum cortisol response to short-term cycling.