The effects of salivary cortisol phase on the stress hormone response to an acute anaerobic exercise challenge

Participants will provide saliva samples every 15 minutes from awakening for approximately 8 hours. Endogenous cortisol levels will begin to be measured in the samples in real-time using a biosensor beginning approximately 4 hours after awakening. The salivary cortisol phase (successively rising or falling concentrations of cortisol) will be identified. Participants will be randomised into groups where either a rising or a falling cortisol phase is sought, and the alternate phase will be sought from the same subject on a second crossover study day as described below. During the identified cortisol phase, the subject will complete two back-to-back 30 second Wingate anaerobic exercise challenges on a braked cycle ergometer using a brake weight of 10% of the subject's body weight. Saliva sampling will continue for the remaining 4 hours. Plasma samples will be collected via lancet immediately before, immediately after, 30 minutes after, and 60 minutes after the Wingate challenge. A washout period of at least seven days will be used before repetition of the study protocol using the alternate salivary cortisol phase. Including this washout period, the total study time is approximately eight days.