Exercise and the Cortisol Awakening Response: A Systematic Review

Abstract

BackgroundThe 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.MethodsA 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.Results10,292 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.ConclusionsMore 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.

Energy Constraint as a Novel Mechanism Linking Exercise and Health

“…Intense physical training can also blunt the cortisol response to submaximal exercise (82). Studies are mixed as to whether chronic exercise also blunts the cortisol awakening response (CAR); the effect may only be evident with large exercise workloads (2) within-subjects study design in recreational runners found a decrease in cortisol awakening response with greater exercise workload (3).…”

Exercising Caution Upon Waking–Can Exercise Reduce Sleep Inertia?

“…There is limited research on how exercise acutely impacts the CAR. To date, studies which have examined the effect of acute exercise on the CAR have only investigated exercise performed during the evening (Garde et al, 2009;Anderson and Wideman, 2017;Ucar et al, 2018). These studies found that a single bout of exercise performed in the evening had no impact on the CAR (Garde et al, 2009;Ucar et al, 2018).…”

“…Despite the limited research on the effect of acute exercise on the CAR, some evidence suggests that acute exercise does affect circulating cortisol levels (Kindermann et al, 1982;Hill et al, 2008;Crewther et al, 2010;Anderson and Wideman, 2017). This is one of the reasons that it is recommended for study participants to remain sedentary when cortisol samples are obtained (Stalder et al, 2016).…”

“…These processes include the reactivation and deactivation of various brain regions and changes in cerebral blood flow (CBF) (Balkin et al, 2002), the cortisol awakening response (CAR) (Clow et al, 2010), and thermoregulatory processes [e.g., increases in core body temperature (CBT) and cooling of extremities] (Kräuchi et al, 2004). Exercise, especially aerobic exercise, is well known to activate each of these physiological processes (Kindermann et al, 1982;Shellock et al, 1985;Kubitz and Mott, 1996;Ide and Secher, 2000;Nielsen et al, 2001;Drust et al, 2005;Hill et al, 2008;Crewther et al, 2010;Rajab et al, 2014;Anderson and Wideman, 2017). If exercise can speed up the physiological changes which occur upon waking, it may influence the duration and severity of sleep inertia and could be a suitable reactive countermeasure.…”

From Risk to Resilience: How Lifestyle Factors Interact with Early-Life Trauma, Genetic Polymorphisms, and Stress, in Predicting Risk for Depression

“…The HPA axis may be another key mediating factor in the relation between exercise and depression. In a recent review, it was suggested that exercise can play a role in the cortisol awakening response (CAR), however, it seems that this effect was only apparent with higher frequencies of exercise (Anderson & Wideman, 2017). This finding may be particularly relevant, as the CAR is often broader among individuals who chronically perceived distress (Kaspers & Scholz, 2004).…”