Changes in Cortisol Awakening Response During 10 Days of High-Intensity Cycling Exercise
Yui Ogasawara1, Takayuki Sugo2, Hironobu Tsuchiya2
1Faculty of Liberal Arts, Sciences and Global Education, Osaka Metropolitan University, 2-1-132 Morinomiya, Joto-ku, Osaka 536-8525, Japan.
Abstract:
Previous studies suggest that the cortisol awakening response (CAR) shows a biphasic pattern-either an increase or a blunting-in response to exercise involving overload, potentially reflecting physiological adaptation. However, its response to continuous high-intensity exercise under controlled experimental conditions has not been sufficiently investigated. This pilot case series examined daily CAR changes during a 10-day high-intensity cycling protocol (20 min/day at 80% of maximal oxygen uptake [V˙O2max]) in two healthy male participants. The CAR increased during Days 1-4 and returned to baseline levels from Day 5 onward, showing similar trends in acute physiological responses. V˙O2max and/or maximum workload improved following the intervention. These findings support the methodological feasibility of longitudinal CAR monitoring during short-term high-intensity exercise under controlled experimental conditions and suggest that CAR may be a promising non-invasive biomarker for assessing short-term physiological adaptation.
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