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 (r2 = .352, P = .025) and CAR% (r2 = .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, Amy R. Lane and Anthony C. Hackney
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.