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The cortisol awakening response (CAR) is often assessed in the saliva and considered to be representative of serum cortisol. However, free cortisol is rapidly converted into cortisone as it passes from the serum into the saliva. Because of this enzymatic conversion, the salivary cortisone awakening response (EAR) may be more closely related to serum cortisol dynamics than the salivary CAR. Therefore, the purpose of this study was to measure the EAR and CAR in saliva and compare it to the serum CAR., Methods: Male participants (n = 12) had an intravenous catheter placed for serial serum sampling and completed two overnight laboratory sessions, wherein participants slept in the laboratory and saliva and serum samples were collected every 15 min after volitional awakening the following morning. Serum was assayed for total cortisol and saliva for cortisol and cortisone. The CAR and EAR was assessed in saliva and the CAR in serum via mixed-effects growth models and common awakening response indices (area under the curve [AUC] relative to the ground [AUC G ] and relative to the increase [AUC I ], and change scores [Δ])., Results: There was a distinct rise in salivary cortisone following awakening demonstrating the presence of a discernable EAR (β Quadratic = -41.18, [95%CI = -68.90 to -13.46], p < 0.004, Conditional R 2 = 0.641). Two EAR indices (AUC G : p < 0.001 and AUC I : p = 0.030) were associated with the corresponding serum CAR indices., Conclusion: We demonstrate for the first time a distinct cortisone awakening response. The results suggest the EAR may be more closely related to serum cortisol dynamics during the post-awakening period, and thus, may be a biomarker of interest in addition to the CAR for assessing hypothalamic-pituitary-adrenal axis functioning., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The effects of acute exercise on the cortisol awakening response (CAR), characterized by the rapid increase in cortisol concentrations within the 30-45 min following sleep offset has yet to be fully elucidated. Thus, our study investigated the effects of late-evening acute exercise on the CAR the following morning. We hypothesized that exercise would have a significant effect on the CAR the following morning. Twelve participants (mean (SD): age = 23 (4) years; mass = 76.8 (8.7) kg; height = 175.6 (5.0) cm; [Formula: see text]O2max = 48.9 (7.5) ml.kg -1 .min -1 ) reported to the laboratory in the evening (1800 h) on two occasions and were randomly assigned to either exercise for one hour (70-75% of maximal power output) or rest condition. Blood and saliva samples were assayed for cortisol. Mixed-effects models determined the effect of exercise on the cortisol response post-waking in both blood and saliva. Participants demonstrated an average exercise-induced increase in circulating cortisol of 477.3%, with actual mean (SD) heart rate relative to maximum of 87.04% (6.14%). Model results demonstrated a negative effect for exercise condition when modeling the serum and salivary cortisol responses to awakening via a quadratic growth model (serum, β Condition  = - 42.26 [95% CI - 64.52 to - 20.01], p < 0.001; saliva, β Condition  = - 11.55 [95% CI - 15.52 to - 7.57], p < 0.001). These results suggest that cortisol concentrations in saliva and blood are significantly lower the morning following a prior evening exercise session. Therefore, the CAR may serve as a useful biomarker to monitor responses to exercise training, although the underlying mechanism for these decreases in the CAR should be investigated further., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

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.

The cortisol awakening response (CAR) describes the increase in cortisol within the first 30-60 min after waking from nocturnal sleep, and is a common biomarker used within psychoneuroendocrinology, but the effect of sleep on the CAR is currently unclear. A previous study suggested that reported discrepancies may be due to other lifestyle behaviors such as physical activity; given the role of the CAR in energy regulation and preparation for the day, it is theoretically plausible that activity level would influence the CAR. However, no study has yet utilized objective monitoring of day-to-day sleep and physical activity to investigate potential effects on the CAR. This study aimed to test the hypotheses that either sleep duration or sleep quality would interact with the prior 24 h' physical activity to predict the CAR on the following morning. Salivary samples were collected from 85 young adults (mean = 19.1 years, SD = 1.89) immediately after waking from nocturnal sleep and again 30 min after waking; two complete and consecutive days were used. Participants wore accelerometers (ActiGraph, wGT3X-BT) throughout this phase of a larger study, which provided objective measures of sleep duration, number of awakenings, and amount of physical activity. Mixed-effects models with post-hoc regions of significance decompositions tested the hypothesized interaction effects. Results demonstrated a significant interaction between prior day sleep duration and physical activity predicting the next day CAR, wherein short sleep duration and high levels of physical activity resulted in an augmented CAR. Although more sleep clearly predicted a smaller next day CAR in main effect, this study provides additional support that sleep duration effects are also moderated by prior day physical activity. Both behavioral factors should be considered when assessing the CAR and the association between the CAR other psychoneuroendocrine outcomes., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

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.

Purpose: Cortisol (C) and testosterone (T) are impacted significantly by prolonged endurance exercise with inverse responses. Increases in C are witnessed concurrently with decrements in T, possibly impacting recovery. This study was conducted to assess the dynamics of C and free T (fT) concentration and recovery time following an exhaustive endurance exercise session (EES)., Methods: 12 endurance-trained males (X ± SD: VO2max 66.3±4.8 ml/kg/min, age 22.8 ± 3.1 years, body fat 11.0 ± 1.4 %, training 7.1 ± 3.2 years) completed a treadmill EES at ventilatory threshold (74.7 ± 4.6 % of VO2max; 96.9 ± 10.8 min). Basal blood C and fT were collected at baseline: -48, -24 h, and immediately before (0 h) the EES as well as immediately (+0 h), +24 h, +48 h, and +72 h after the EES. Blood glucose (G) was measured to confirm no undue influence on C. Statistically data were analyzed with repeated measures ANOVA (LSD post hoc)., Results: C (nmol/L) increased significantly from -48 h (321 ± 59) to +0 h (701 ± 178) (p < 0.001), and displayed a baseline overshoot with +24 h (209 ± 67) being significantly lower than -48 and +0 h (p < 0.03). fT (pmol/L) decreased significantly from -48 h (161 ± 40) to +0 h (106 ± 38) (p < 0.01) and remained lower at +24 h (110 ± 33) and +48 h (129 ± 30) (p < 0.001). G remained stable throughout. A moderately negative correlation (r = -0.636, p < 0.026) was found between C and fT at +0 h., Conclusions: EES recovery may require 48 h for C and 72 h for fT to return to baseline values. Furthermore, C and fT were only correlated immediately post-exercise. Future research should perform more frequent measurements throughout time course.

Background: The cortisol awakening response (CAR) has been used as a biomarker of stress response in a multitude of psychological investigations. While a myriad of biochemical responses have been proposed to monitor responses to exercise training, the use of CAR within the exercise and sports sciences is currently limited and is a potentially underutilized variable. Therefore, the purpose of this review was to collate studies that incorporate both exercise and CAR, in an effort to better understand (a) whether CAR is a useful marker for monitoring exercise stress and (b) how CAR may be most appropriately used in future research. Methods: A systematic review of the literature was conducted, following PRISMA guidelines. Searches were conducted using PubMed, SportDISCUS, Scopus, and PsychInfo databases, using search terms related toCAR and exercise and physical activity. Results: 10,292 articles were identified in the initial search, with 32 studies included in the final analysis. No studies investigated the effects of laboratory-controlled exercise on CAR. Variable effects were observed, possibly due to inconsistencies in study design, methodology, population, and CAR analysis. The available literature suggests a threshold of exercise may be required to alter the HPA axis and affect CAR. Moreover, CAR may represent a combination of previous exercise load and upcoming stress, making current interpretation of field-based observational research challenging. Conclusions: More research is needed to fully elucidate the influence of exercise on CAR and address a number of gaps in the literature, including controlling exercise load, consistent sample collection, and CAR calculation and analysis. [ABSTRACT FROM AUTHOR]

The free testosterone to cortisol ratio (fTC) and heart rate variability (HRV) indices have been independently proposed as objective biomarkers of physiological resilience and readiness, respectively. It is hypothesized that individuals that enter a training period with high resilience and readiness would have a greater positive response to the training. PURPOSE: Therefore, the purpose of this study was to investigate the association between fTC and HRV with fitness changes in division I male college soccer players. METHODS: Two division I teams were recruited to participate in this study. Participants completed an orthostatic HRV challenge (supine, sitting, standing) and provided blood samples prior to the 6-week Spring training period. The HRV indices of root mean square of successive differences (RMSSD) and high frequency power (autoregressive, normalized; HF) were calculated in all postural conditions. Blood samples were assayed for free testosterone and cortisol using competitive binding ELISAs. Participants completed the yo-yo intermittent recovery test (YYIR) before and after the 6-week training period and the absolute increase in distance (m) achieved during the YYIR represented the change in fitness (YYIRΔ). Separate linear regression models tested the association of fTC and all HRV indices and their interactions with YYIRΔ. All predictors were first centered and scaled and alpha level was set at p < 0.05 for all models. RESULTS: Participants (n = 21, age = 19.5±1.0 years, height = 179.0±6.4 cm, weight = 76.9±9.4 kg, body fat = 12.6±4.3 %) from the two teams did not differ in YYIRΔ (mean±SD = 438±212, p = 0.64). A significant association with YYIRΔ was observed for the interaction between fTC and HFsitting (F(3,17) = 4.31, β = 4.92,p = 0.02, R² = 0.33). No other indices or interactions were significantly associated with YYIRΔ. CONCLUSIONS: These results suggest that HRV and fTC represent potential objective pre-training biomarkers capable of identifying athletes that will be most responsive to individualized fitness and conditioning programs. Further research is necessary to confirm the utility of these specific objective biomarkers in larger cohorts and across multiple training situations. [ABSTRACT FROM AUTHOR]