Hair Cortisol as a Reflection of Metabolic, Physical, and Psychological Stress in Male and Female Collegiate Athletes at Different Phases of a Competitive Season
Open Access
- Author:
- Tooke, Anna
- Area of Honors:
- Kinesiology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Nancy Williams, Thesis Supervisor
Mark Dyreson, Thesis Honors Advisor - Keywords:
- Cortisol
Stress
Energy Deficiency
Metabolism
Training load
psychological stress
hair cortisol - Abstract:
- A competitive season represents a multi-stressor environment for athletes, posing various stressors to the body due to increased training volume and energy demands as well as increased psychological pressures. An accumulation of stress due to these factors can result in increased secretion of stress hormones in the body such as cortisol. Circulating cortisol is deposited in hair shafts, and cortisol can be extracted from hair samples and measured according to concentration. Analyzing hair cortisol concentration serves as a retrospective measure of chronic cortisol exposure, with the closest 3 cm of hair to the scalp representing the previous 3 months of hair growth and, thus, cortisol accumulated in hair. This study, as part of a larger longitudinal observational study, aims to evaluate the use of hair cortisol as a reflection of metabolic, physical, and psychological stress in male and female collegiate athletes across a competitive season. This study followed 19 athletes (9 males and 10 females) throughout a competitive season, from pre-season to peak-season to off-season. At each season phase, measurements of metabolic, physical, and psychological stress were repeated, allowing comparison across time. Such measurements included: anthropometrics and body composition via dual energy x-ray absorptiometry (DXA), resting metabolic rate (RMR) via indirect calorimetry and normalized per kg of fat free mass (FFM), energy intake via app-based diet logs, training volume via paper exercise logs, questionnaires to evaluate psychological stress, namely the Perceived Stress Scale (PSS) and Recovery-Stress Questionnaire for Athletes (RESTQ-52), and hair cortisol and cortisone. In addition, a ratio of actual to predicted RMR based on metabolically active tissue measured via DXA was calculated to represent energy status and identify potentially energy deficient individuals, representing metabolic stress, and exercise energy expenditure (EEE) was calculated using data from the exercise logs and metabolic equivalent (MET) values from the 2024 Adult Compendium for Physical Activity, representing physical stress. We hypothesized that lower RMR/kg FFM and RMR ratio, indicating metabolic stress, higher training volume and EEE, indicating physical stress, and higher scores from the psychological stress questionnaires would be reflected by higher hair cortisol levels. The results of this study were that there were no significant relationships between these stress variables and hair cortisol over time, suggesting that hair cortisol does not serve as a reflection of metabolic, physical, or psychological stress across a competitive season. The only significant relationship found was a positive relationship between RMR/kg FFM and RMR ratio and hair cortisol (r=0.6, p=0.018; r=0.646, p=0.009), as well as cortisol/cortisone ratio (r=0.643, p=0.01; r=0.564, p=0.028), within the off-season, possibly explained by increased training volume during the peak-season increasing RMR and stress, as reflected by hair cortisol. Although this study did not produce the results as expected by our hypothesis, there were several limitations, such as a small sample size and variations in the amount of time in between season phases for athletes in different sports, that when addressed in future studies could produce more accurate and generalizable results, presenting a clearer picture of the effects of different types of stress on cortisol exposure.