Abstract
BACKGROUND: Cortisol is a steroid hormone that follows a distinct diurnal timeline; however, while healthy ranges exist, it not been determined whether or why individuals differ on baseline cortisol levels. The aim of this study was to test the anecdotal evidence of different levels of responders by classifying these levels in resting cortisol, and to correlate individual cortisol responses to psychological traits. METHODS: Twenty-two male athletes (mean age 22.5 ± 4.34 years) provided two saliva samples at the same time each day over three days in week one of their pre-season to determine individual baseline salivary cortisol levels. Participants also completed self-report psychological traits measures for correlation to cortisol levels. RESULTS: Three levels of cortisol in responders were clearly identified (F(2,19) = 69.00, p < 0.001). Pearson's correlation coefficient showed that there was no significant relationship between baseline cortisol levels and psychological traits (optimism, r = 0.23, p = 0.29; stress, r = 0.05 p = 0.82; decision making, r = 0.19 p = 0.38). CONCLUSIONS: This novel study identified that within an overall healthy range, individual athletes will likely fall into either a low, average or high band of baseline cortisol. However individual responses did not correlate to self-report psychological traits. Caution is required if sports science staff wish to use cortisol to measure psychological stress.