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Hypothalamic-Pituitary-Adrenal Axis Response and Recovery from High-Intensity Exercise in Women: Effects of Aging and Fitness

Stress and Neuroendocrine Research Center, Exercise and Sport Research Institute, Department of Kinesiology, Arizona State University, Tempe, Arizona 85287-0404

Address all correspondence and requests for reprints to: Kathleen S. Matt, Department of Kinesiology, Arizona State University, Tempe, Arizona 85287-0404. E-mail: kmatt{at}asu.edu.

This study tested the hypotheses that aging is associated with prolonged recovery after a challenge to the hypothalamic-pituitary-adrenal axis (acute exercise) and that aerobic fitness is associated with a blunting of the age-related loss of negative feedback sensitivity. Young (27 ± 2.8 yr, n = 9), older (64.6 ± 1.4 yr, n = 11), and older-fit women (66.3 ± 2.2 yr, n = 11) underwent a short bout of treadmill exercise at high (but submaximal) intensity. The exercise trial elicited significant increases in heart rate, blood pressure, ACTH, and cortisol (P < 0.001). Although the young and the older women exhibited similar cortisol response to the trial and throughout the recovery period, the older women had a slower decrease of ACTH levels (P < 0.05), suggesting reduced negative feedback sensitivity with aging. Between the two groups of older women, the older-fit group had significantly greater rate of recovery of ACTH levels (P < 0.05) compared with the older unfit women. However, older fit women had greater cortisol production during the recovery period (P < 0.05), suggesting greater adrenal sensitivity to ACTH. These results suggest that aging is associated with changes in the dynamic function of the hypothalamic-pituitary-adrenal axis and that these changes are attenuated by aerobic fitness.

Present address for T.T.: Kronos Longevity Research Institute, Phoenix, Arizona.

Abbreviations: AUC, Area under the curve; AURC, area under the response curve; HPA, hypothalamic-pituitary-adrenal; NS, not significant; VO₂ max, maximum oxygen consumption.

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