The cortisol awakening response (CAR) is a distinct component of the circadian cortisol profile and has promise as a biomarker for the monitoring of athlete readiness and training status. Although some studies have suggested the CAR may be affected by the development of overtraining syndrome (OTS), this has yet to be systematically investigated. Purpose: To compare the CAR and diurnal cortisol slope between athletes diagnosed with OTS, healthy athletes, and sedentary controls. Methods: This study was a secondary analysis of data from the Endocrine and Metabolic Responses on Overtraining study. Male participants were recruited to either OTS, healthy athlete, or sedentary control groups. The participants produced saliva samples immediately after waking (S1), 30 minutes after waking (S2), at 16:00 hours, and at 23:00 hours. Salivary cortisol concentration was determined by an electrochemiluminescence assay. Mixed-effects models were used to assess the conditional effect of group (sedentary controls, OTS, and healthy athletes) on the change in cortisol over time. Separate models were fit for the awakening samples (S1 and S2) and for the diurnal slope (linear change across S1, 16:00 h, and 23:00 h). Results: The models demonstrated significant time-by-group interaction for OTS for the 2 cortisol concentrations collected during the awakening period (β = −9.33, P < .001), but not for the diurnal cortisol slope (β = 0.02, P = .80). Conclusions: These results suggest the CAR may be associated with OTS and should be considered within a panel of biomarkers. Further research is necessary to determine whether alterations in the CAR may precede the diagnosis of OTS.
Travis Anderson, Laurie Wideman, Flavio A. Cadegiani, and Claudio E. Kater
Travis Anderson, Amy R. Lane, and Anthony C. Hackney
The cortisol awakening response (CAR) is commonly used as a marker of psychological stress; however, it is unknown whether CAR is affected by regular physical-exercise-induced stress. Purpose: To assess the relationship between training load and CAR. Methods: Recreational endurance athletes were recruited from local running clubs. Subjects (n = 15) completed training logs for 2 wk, with various training loads, including psychometric analysis (Recovery-Stress Questionnaire for Athletes). Subjects provided saliva samples each day immediately after waking and 30 min postwaking. Samples were analyzed for cortisol concentration via enzyme-linked immunosorbent assay and subsequently were analyzed for CAR and CAR%. Daily training load was calculated and analyzed as training impulse. Simple linear regression was used to assess the relationship between CAR and training impulse. Results: CAR (r 2 = .352, P = .025) and CAR% (r 2 = .373, P = .012) both showed a significant negative relationship with training load. Conclusions: These results suggest that CAR is affected by regular exercise training loads in recreational athletes. It is recommended that future CAR research control for fitness level and exercise training load in physically active populations.
Travis Anderson, Sandra J. Shultz, Nancy I. Williams, Ellen Casey, Zachary Kincaid, Jay L. Lieberman, and Laurie Wideman
Evidence suggests menstrual cycle variation in the hormone relaxin may have an impact on ligament integrity and may be associated with risk of anterior cruciate ligament injury in physically active women. However, studies to date have only detected relaxin in a small number of participants, possibly due to inter-individual variability, frequency of sample collection, or analytical techniques. Therefore, the purpose of this study was to analyze serial serum samples in moderately active, eumenorrheic women to identify the proportion of women with detectable relaxin concentrations. Secondary analyses were conducted on two independent data sets. Data Set I (DSI; N = 66) participants provided samples for 6 days of menses and 8–10 days of the luteal phase. Data Set II (DSII; N = 15) participants provided samples every 2–3 days for a full menstrual cycle. Samples were analyzed via a relaxin-2 specific ELISA assay. Limit of detection (LOD) was calculated from the empirical assay data. LOD was calculated as 3.57 pg·ml−1. Relaxin concentrations exceeded the LOD in 90.91% (DSI) and 93.33% (DSII) of participants on at least 1 day of sampling. Actual peak values ranged from 0.0 pg·ml−1 to 118.0 pg·ml−1. Relaxin was detectable in a higher proportion of young women representing a broad range of physical activity levels when sampled more frequently. Future studies investigating relaxin should consider sampling on more than 1 day to accurately capture values among normal menstruating women.