Trained versus untrained men: different immediate post-exercise responses of pituitary adrenal axis

Abstract

The hypothalamo-pituitary-adrenal axis is involved throughout the exercise-recovery cycle. Nevertheless, differences in hormone responses during early recovery between sedentary and endurance trained subjects are not well known. The aim of this preliminary study was to monitor plasma cortisol and adrenocorticotropic hormone (ACTH) concentrations both during and after the end of running exercise performed by four endurance trained adults (marathon men) compared to four sedentary subjects. Two parameters, i.e. intensity and duration, were changed on 4 consecutive days. The 1st day (D0) was spent in the laboratory: all blood samples were obtained at rest to determine diurnal variations of each hormone. On the following days (D1-D4) the subjects exercised: D1 and D2 brief (20 min), light (50% maximal heart rate HRmax, D1) or strenuous (80% HRmax, D2), D3 and D4 prolonged (120 min), light (D3) or strenuous (D4). In both groups, neither brief (D1, D2) nor prolonged light exercise (D3) induced any significant variation in plasma ACTH or cortisol concentrations. Plasma ACTH and cortisol concentrations increased only if the exercise was intense and prolonged (D4). The training factor did not modify the intensity or duration thresholds for the activation of the pituitary-adrenocortical response to exercise in the conditions of our experiment. However, during immediate recovery from the four exercise regimens, the plasma ACTH concentrations of the marathon men were constantly above the values of the sedentary subjects, although plasma cortisol concentration remained similar in both groups. As an indirect means of evaluating the relationships between ACTH and cortisol we compared the areas under the cortisol and ACTH curves (AUC) from 0.5 to 3.5 h during recovery from D1 to D4 compared to D0 at the same time. Cortisol AUC were similar in the sedentary subjects and marathon men although the ACTH AUC were different in the sedentary subjects and marathon men, suggesting a change in the pituitary-adrenal relationship at some yet indeterminate level. During the immediate recovery from exercise whatever its intensity, the magnitude of the ACTH response was increased in the trained subjects but with a reduced effect upon its target, the adrenal glands. This phenomenon has not been described in the literature. Two non-exclusive phenomena may be involved, i.e. a decreased adrenal sensitivity to ACTH stimulation, and/or a decreased hypothalamo-pituitary axis sensitivity to cortisol negative feedback.

Decreased pituitary sensitivity to glucocorticoids in endurance-trained men

“…More specifically, when sedentary and healthy ET men are compared in resting, unchallenged conditions, no difference in HPA axis activity is seen. Indeed, we and others have previously reported normal plasma cortisol values with preserved nycthemeral cortisol rhythm in ET men compared with sedentary subjects (2,3), as well as normal 24 h UFC after a day with no training (4). By contrast, when the HPA axis is challenged, results from ET men differ from those of sedentary men.…”

“…By contrast, when the HPA axis is challenged, results from ET men differ from those of sedentary men. For example, after an exercise-induced cortisol increase, the subsequent stimulation exerted by a meal does not elicit a rise of cortisol levels in sedentary men, whereas in ET men a marked cortisol increase occurs (3). These findings suggesting a decreased sensitivity to glucocorticoid negative feedback in healthy ET men may reflect allostatic modifications of the HPA axis due to repeated exercise-induced HPA axis activation (5).…”

Prevention, diagnosis and treatment of the overtraining syndrome: Joint consensus statement of the European College of Sport Science (ECSS) and the American College of Sports Medicine (ACSM)

“…Accordingly, morning plasma cortisol concentration and 24 h urinary free cortisol (UFC) excretion in resting endurance-trained men are similar to those of age-matched sedentary subjects (Kern et al 1995;Duclos et al 1997;Gouarne et al 2005). Since UFC represents an integrated measure of the 24 h cortisol secretion, this is in accordance with the previously reported normal diurnal HPA axis rhythm in endurance-trained men (Duclos et al 1997(Duclos et al , 2007. Finally, endurance-trained men maintain the seasonal rhythmicity of cortisol excretion; as in sedentary men the highest concentrations of urinary cortisol, morning plasma cortisol and saliva cortisol are observed during autumn and winter compared with spring and summer (Gouarne et al 2005).…”

“…For example, the HPA adaptation to normal training is characterised by increased ACTH/cortisol ratio only during exercise recovery (due to decreased pituitary sensitivity to cortisol) (Lehmann et al 1993b;Duclos et al 1997Duclos et al , 1998, and by modulation REVISION : Consensus Statement "Overtraining" (17-07-2012) 10 of tissue sensitivity to glucocorticoids (Duclos et al 1999(Duclos et al , 2003). However, it should be emphasized that during a resting day, in endurance-trained athletes 24 h cortisol secretion under non-exercising conditions is normal Duclos et al 1999Duclos et al , 2003.…”

Interactions of Metabolic Hormones, Adipose Tissue and Exercise

“…[63,181] The mechanism for the decline apto decline with training, [77,193] apparently as a result pears to be hypothalamic in origin, possibly involvof altered ACTH functioning. [193,194] ing opioids, prolactin, CRH, or gonadotrophic horStudies have reported that resting concentrations mone-releasing hormone. [58] In contrast to the anof leptin may decline with endurance or resistance drogens, we know little about the estrogen response training.…”