Date of Award
Bachelor of Science (BS)
Health, Nutrition and Exercise Science
Dr. H. Scott Kieffer
Dr. Jodie Haak
Cortisol is a steroid hormone that is produced in the body as a response to stressors, including acute bouts of exercise. One of the roles of cortisol related to exercise involves the enhanced metabolism of fat, carbohydrates, and proteins. Caffeine is the most commonly-used ergogenic aide and has been suggested to improve performance in high-intensity and endurance exercise.However, it is unclear whether the mode used to deliver the caffeine has an effect on performance or whether that effect would be related to the release of cortisol from the adrenal glands. The goal of this double-blind study was to test the differences in performance and cortisol levels between caffeine gum and caffeine pills. Due to the non-invasive nature of saliva collection, and because cortisol is known to accumulate in the saliva in a predictable pattern, this study measured salivary cortisol. Trained cyclists completed three separate 10-mile time-trials, and each time they were given either placebo pill/placebo gum (mean cortisol concentration change of 0.1763±0.2522 nmol/L), placebo pill/caffeine gum (0.0880±0.0689 nmol/L), or caffeine pill/placebo gum (0.1068±0.0901 nmol/L; p = 0.34). Saliva was collected five minutes before and immediately following each time trial. Saliva samples were stored at - 80°C. Samples were analyzed using an ELISA test and a high-sensitivity salivary cortisol kit from Salimetrics, Inc. (State College, PA). No evidence of a relationship was found between caffeine use of either type and change in cortisol level, and evidence of a relationship was observed between each subject’s individual trial times and change in cortisol level for that trial.
Roshong, Anne; Clune, Lauren; Kieffer, H.Scott; and Haak, Jodie, "Effect of Caffeine on Salivary Cortisol during 10-Mile Cycling Time Trial" (2015). Honors Projects and Presentations: Undergraduate. 23.