Cortisol Awakening Response and Heart Rate Variability in the Menstrual Cycle of Sportswomen

Abstract

<b>Purpose</b>: This study aimed to examine the activities of heart rate variability (HRV) and cortisol secretion as markers of the autonomous nervous system (ANS) and the hypothalamic-pituitary-adrenal axis (HPA) during the menstrual cycle in female athletes. <b>Method</b>: Saliva samples of the participants (<i>n</i> = 28) were collected successively at 0, 15, 30, and 60 min after awakening to assess cortisol awakening response (<i>CAR</i>) during each of four phases of the menstrual cycle (the menstruation, ovulation, luteal, and premenstrual phases). Diurnal saliva samples were collected at noon, in the evening (17:00) and 22:00 for cortisol analysis. HRV was measured in the menstrual and premenstrual phases at rest (12:00-14:00). <b>Results</b>: There was no difference between <i>CAR</i> parameters in the menstrual phases. <i>CAR</i> parameters and diurnal cortisol levels were significantly correlated with each other throughout the menstrual cycle. Mean cortisol was a strong predictor of the area under the curve (<i>AUC</i>: S = 0.042; R-Sq = 98.4%). Time-dependent parameters of HRV (standard deviation of the N-N interval [SDNN; <i>P</i> = .049] and the root mean square of the successive R-R differences [rMSSD; <i>P</i> = .038]) were significantly higher in the menstrual phase. There were no correlations between <i>CAR</i> and HRV parameters. <b>Conclusions</b>: We suggest that the hypothalamic-pituitary-adrenal axis activity and the autonomic nervous system work in a separate manner that is not affected by the menstrual phases in sportswomen. The present study contributed to a better understanding of the relationship between the dynamics of cortisol release and the autonomic nervous system in different phases of the menstrual cycle in female athletes.