The influence of fitness on neuroendocrine responses to exhaustive treadmill exercise

Magnitude of exercise-induced β-endorphin response is associated with subsequent development of altered hypoglycemia counterregulation

CONTEXT

β-Endorphin release in response to recurrent hypoglycemia is implicated in the pathogenesis of hypoglycemia-associated autonomic failure.

OBJECTIVE

We hypothesized that exercise-induced β-endorphin release will also result in the deterioration of subsequent hypoglycemia counterregulation and that the counterregulatory response will negatively correlate with the degree of antecedent β-endorphin elevation.

DESIGN, SETTING, PARTICIPANTS, AND INTERVENTIONS

Sixteen healthy subjects (six females, aged 26 ± 4.3 yr, body mass index 26.1 ± 5.6 kg/m(2)) were studied with three experimental paradigms on 2 consecutive days. Day 1 consisted of one of the following: 1) two 90-min hyperinsulinemic hypoglycemic clamps (3.3 mmol/liter); 2) two 90-min hyperinsulinemic euglycemic clamps while subjects exercised at 60% maximal oxygen uptake; or 3) two 90-min hyperinsulinemic euglycemic clamps (control). Day 2 followed with hyperinsulinemic (396 ± 7 pmol/liter) stepped hypoglycemic clamps (5.0, 4.4, 3.9, and 3.3 mmol/liter plasma glucose steps).

MAIN OUTCOME MEASURES

Day 2 hypoglycemia counterregulatory hormonal response and glucose turnover ([3-(3)H]-glucose) as indicators of recovery from hypoglycemia.

RESULTS

There was a significant inverse correlation between plasma β-endorphin levels during exercise and catecholamine release during subsequent hypoglycemia. Subjects with an exercise-induced rise in β-endorphin levels to above 25 pg/ml (n = 7) exhibited markedly reduced levels of plasma epinephrine and norepinephrine compared with control (2495 ± 306 vs. 4810 ± 617 pmol/liter and 1.9 ± 0.3 vs. 2.9 ± 0.4 nmol/liter, respectively, P < 0.01 for both). The rate of endogenous glucose production recovery in this group was also much lower than in controls (42 vs. 89%, P < 0.01).

CONCLUSIONS

The physiological increase in β-endorphin levels during exercise is associated with the attenuation of counterregulation during subsequent hypoglycemia.

Impaired adrenergic- and corticotropic-axis outflow during exercise in chronic obstructive pulmonary disease

Exercise stimulates coordinated release of the sympathoadrenal hormones adrenocorticotropic hormone (ACTH), cortisol, norepinephrine (NE), and epinephrine (Epi). The study hypothesis was that chronic obstructive pulmonary disease (COPD) is marked by heightened sympathoadrenal outflow at comparable relative workloads. The location of the study was at a clinical research unit. Eight healthy men and 9 men with stable COPD (forced expiratory volume at 1 second <75% predicted) were studied. Volunteers rested (baseline) or exercised at individual submaximal (35% ± 5%) or maximal oxygen consumption. Blood was sampled every 2 minutes for 40 minutes concurrently. Two-way analysis of covariance was applied to examine group (healthy/COPD) and exercise (3 levels) effects on ACTH, cortisol, NE, and Epi release and regularity (estimable by approximate entropy). The timing of peak hormone concentrations was Epi, 14 minutes; NE, 16 minutes; ACTH, 22 minutes; and cortisol, 34 minutes in both cohorts. Type of exercise regimen influenced all 4 hormones (each P < .001), and subject group (control vs COPD) affected cortisol (P < .001) and Epi (P = .048) responses. Exercise regimen and group together controlled ACTH, cortisol, and Epi (each P < .001), but not NE, responses. In particular, endocrine responses were attenuated in COPD compared with control subjects. Approximate entropy analysis also identified loss of maximal exercise-induced ACTH-secretory regularity in COPD patients (P = .042). These outcomes demonstrate impaired rather than augmented exercise-associated sympathocorticotropic-axis outflow in patients with COPD even when outcomes are normalized to maximal oxygen consumption, suggesting that factors other than fitness are at work.

Advocating neuroimaging studies of transmitter release in human physical exercise challenges studies

This perspective attempts to outline the emerging role of positron emission tomography (PET) ligand activation studies in human exercise research. By focusing on the endorphinergic system and its acclaimed role for exercise-induced antinociception and mood enhancement, we like to emphasize the unique potential of ligand PET applied to human athletes for uncovering the neurochemistry of exercise-induced psychophysiological phenomena. Compared with conventional approaches, in particular quantification of plasma beta-endorphin levels under exercise challenges, which are reviewed in this article, studying opioidergic effects directly in the central nervous system (CNS) with PET and relating opioidergic binding changes to neuropsychological assessments, provides a more refined and promising experimental strategy. Although a vast literature dating back to the 1980s of the last century has been able to reproducibly demonstrate peripheral increases of beta-endorphin levels after various exercise challenges, so far, these studies have failed to establish robust links between peripheral beta-endorphin levels and centrally mediated behavioral effects, ie, modulation of mood and/or pain perception. As the quantitative relation between endorphins in the peripheral blood and the CNS remains unknown, the question arises, to what extent conventional blood-based methods can inform researchers about central neurotransmitter effects. As previous studies using receptor blocking approaches have also revealed equivocal results regarding exercise effects on pain and mood processing, it is expected that PET and other functional neuroimaging applications in athletes may in future help uncover some of the hitherto unknown links between neurotransmission and psychophysiological effects related to physical exercise.

Exercise and brain health--implications for multiple sclerosis: Part II--immune factors and stress hormones

Part I of this review addressed the possible modulatory role of exercise on neuronal growth factors to promote brain health in neurodegenerative diseases such as multiple sclerosis (MS), which is characterized by varied patterns of inflammation, demyelination and axonal loss. Part II presents evidence that supports the potential neuroprotective effect of exercise on the modulation of immune factors and stress hormones in MS. Many current therapies used to attenuate MS progression are mediated, at least in part, through alterations in the relative concentrations of pro- and anti-inflammatory cytokines. Exercise-induced alterations in local and systemic cytokine production may also benefit immune function in health and disease. Exercise immunomodulation appears to be mediated by a complex interaction of hormones, cytokines and neural factors that may favorably influence immune variables in MS. The promising interplay between exercise and brain health in MS deserves further investigation.

Effect of a 12-Month Randomized Clinical Trial of Exercise on Serum Prolactin Concentrations in Postmenopausal Women

Prolactin is associated with an increased risk of postmenopausal breast cancer; however, few modifiable factors are known to reduce prolactin concentrations. Therefore, we examined the effect of a 12-month moderate-intensity exercise intervention on serum prolactin concentrations as a secondary end point (primary end points were estrogens and androgens). We randomly assigned 173 postmenopausal women who were sedentary, overweight (body mass index >24 kg/m(2), body fat >33%), ages 50 to 75 years, and not using hormone therapy to an exercise intervention or stretching control group. The intervention was facility- and home-based (45 min, 5 days/wk moderate-intensity sports/recreational exercise). One hundred and seventy (98%) women completed the study. Prolactin concentrations were similar at baseline (P = 0.25, geometric mean exercisers = 6.9 and controls = 7.5 ng/mL). Overall, the intervention was not associated with changes in prolactin concentrations between exercisers and controls at 3 months (P = 0.46) or 12 months (P = 0.29). The intervention effect did not vary by baseline age, body mass index, parity, or change in percent body fat during the intervention. Among exercisers, there was a significant difference in prolactin concentrations by change in fitness (VO(2)max) between baseline and 12 months. Exercisers whose VO(2)max changed by <5% had a 5% increase in prolactin concentrations, whereas those who increased their VO(2)max by 5% to 15% and >15% had a 11% (P = 0.03) and 7% (P = 0.01) decrease in prolactin concentrations, respectively. Although the exercise intervention had little effect on prolactin concentrations overall, increasing physical fitness was associated with reduced prolactin concentrations among postmenopausal women.

Effects of endurance training on endocrine response to physical exercise after 5 days of bed rest in healthy male subjects

The study was designed to evaluate how a bout of endurance training (ET) influences the endocrine response after head-down bed rest (HDBR). Eleven healthy males completed the study, which consisted of a 6-wk ET followed by 5 days of -6 degrees head-down HDBR. Treadmill exercise at 80% of pretraining maximal aerobic capacity (VO(2max)) was performed before and after ET as well as after HDBR. ET increased VO(2max) by 13%. The response of norepinephrine was attenuated after ET and exaggerated after HDBR (P < 0.001). The differences in epinephrine responses were not statistically significant. The responses of cortisol and plasma renin activity (PRA) were unchanged after ET and were enhanced after HDBR (P < 0.001). The response of growth hormone after HDBR was reduced (P < 0.05). Only the change in cortisol response was associated with the increment of VO(2max) after ET (r = 0.68, P < 0.01). Endurance training failed to completely prevent changes in endocrine responses seen after HDBR. Improvement of physical fitness was associated with an enhancement of the cortisol response to exercise following the period of bed rest.

Effects of tourniquet-induced ischemia on the release of proopiomelanocortin derivatives determined in peripheral blood plasma

Proopiomelanocortin (POMC) is expressed in pituitary, central nervous system, and in a few peripheral tissues. This study addresses the hypothesis that metabolic stressors, such as acidosis, may induce the release of POMC derivatives into the cardiovascular system not only from the pituitary but also from other sites of POMC expression. In our study, we investigated the liberation of POMC derivatives from peripheral tissues under a state of acidosis achieved by tourniquet-induced ischemia, alteration of lactate concentration, and base excess. In eight patients undergoing knee arthroplasty under spinal anesthesia, catheters were inserted into the femoral vein proximally to thigh tourniquet location. Blood was drawn from these catheters 5 min before and 40 s, 5 min, and 10 min after tourniquet deflation to measure plasma concentrations of N-acetyl-beta-endorphin immunoreactive material (IRM), beta-endorphin IRM, authentic beta-endorphin, adrenocorticotropin, lactate, pH, and base excess. In five of eight patients, we found a significant increase of beta-endorphin IRM levels 40 s after tourniquet deflation compared with predeflation levels; 5 and 10 min after tourniquet deflation, the beta-endorphin IRM levels were below the detection limit. Thus beta-endorphin IRM was released from ischemic limb tissues into the cardiovascular system. Only a small part of the determined beta-endorphin IRM corresponded to authentic beta-endorphin. Forty seconds after tourniquet deflation, the beta-endorphin IRM concentration correlated with base excess (r < 0.71; P < 0.05); no significant correlations were found with pH or lactate levels. Thus it was shown here for the first time that ischemic stress may induce the release of beta-endorphin IRM from nonpituitary tissues.

Exercise increases prolactin-receptor expression on human lymphocytes

Plasma prolactin has been shown to increase during stress; the immune system is responsive to prolactin and affected by stress. Therefore, this study was undertaken to investigate the effects of acute graded, maximal treadmill exercise on prolactin-receptor expression by lymphocytes. Eight healthy men underwent one exercise and one nonexercise session. Blood was sampled immediately before and after the exercise. On the day of the nonexercise session, two resting blood samples were obtained at the same times as the exercise session samples to act as baseline data. Plasma prolactin concentrations were significantly elevated in response to exercise and correlated positively with total prolactin-receptor expression per B lymphocyte. An increase in total prolactin-receptor expression per B lymphocyte in response to exercise also was observed. In addition, exercise significantly increased the total number of circulating B lymphocytes expressing prolactin receptor as well as the total number of circulating B lymphocytes. These data support the idea that exercise may enhance the interaction between immune target cells and prolactin, a stress hormone capable of enhancing immune function.

Influence of fitness on the integrated neuroendocrine response to aerobic exercise until exhaustion

A group of trained and sedentary men performed an incremental graded exercise-test to exhaustion in order to assess the organic response of the two main stress-activated systems: the sympathetic nervous system with its endocrine component (the adrenal medulla), and the hypothalamic-pituitary-adrenal (HPA) axis. Maximal plasma concentrations of ACTH, cortisol and endogenous opioids (beta-endorphins) were obtained at the end of the exercise-test in the trained group. Thus ACTH increased from basal value of 21.25 +/- 2.5 pg/ml to 88.78 +/- 11.8 pg/ml at the end of the exercise (p<0.01); cortisol, from 16.56 microg/dl +/- 4.94 microg/dl to 23.80 +/- 4.57 microg/dl in min 15 of the recovery period (p<0.001); and beta-endorphin from 21.80 +/- 8.33 pmol/ml to 64.36 +/- 9.8 pmol/ml in min 3 of the recovery period (p<0.05). Catecholamine levels were increased from initial values at the end of the effort test in both control and trained groups. Control subjects exhibited a higher responsiveness compared to trained and showed superior intrinsic stimulation of the sympathetic nervous system. These results reveal a different response according to fitness in a physical stress situation.

Beta-endorphin (1-31) in the plasma of male volunteers undergoing physical exercise

beta-Endorphin is an opioid peptide representing the C-terminal 31 amino acid residue fragment of proopiomelanocortin (POMC). The release of beta-endorphin from the pituitary into the cardiovascular compartment under physical or emotional stress has been frequently reported. However, besides beta-endorphin (1-31), nine acetylated or non-acetylated beta-endorphin analogues exist - in addition to N-terminally elongated beta-endorphin derivatives such as beta-lipotropin (beta-LPH). Since conventional radioimmunoassays (RIAs) and even commercially available two site-RIAs pick up at least some of those beta-endorphin derivatives, only "beta-endorphin immunoreactive materials" and not authentic beta-endorphin have been determined in those studies. We have developed a highly specific two site-RIA for beta-endorphin (1-31), which does not cross-react with all beta-endorphin derivatives known to occur as yet. Using this RIA as well as further assays for determination of beta-endorphin (1-31), beta-endorphin immunoreactive material (IRM), ACTH and Cortisol in the plasma of 14 volunteers upon intensive physical exercise, we found authentic beta-endorphin only in about 50% of the plasma samples, representing therein only a minor portion of the beta-endorphin IRM.

The effects of exercise duration on adrenal HSP72/73 induction in rats

This study investigated the effects of varying durations of exercise training on heat shock proteins 72 and 73 (HSP72/73) induction in the rat adrenal gland. Female Sprague-Dawley rats (120 days old) were assigned to either a sedentary control group (C) or one of the three endurance exercise training groups. Trained animals ran on a treadmill at approximately 75% VO2max for 10 weeks (4-5 days week-1) at one of the three different exercise durations (30 min day-1=T30, 60 min day-1=T60, or 90 min day-1=T90). All durations of exercise training resulted in an increase in the HSP72 levels (P < 0.0001). The magnitude of the training-induced elevation in the HSP72 levels in the adrenal gland increased as a function of the training duration ( approximately 60-fold increase in T90; approximately 40-fold increase in T60; and approximately 15-fold increase in T30). Longer exercise durations (>60 min day-1), also resulted in small but significant increase in HSP73 level ( approximately 1.2-fold increase in both T60 and T90; P < 0.05). These results demonstrate that the physiological stress created by chronic treadmill running can induce both HSP72 and HSP73 in rat adrenal gland. Increased levels of adrenal HSP72/73 expression during rigorous exercise, may be one of the adaptive mechanisms of the adrenals to cope with an increased dose of stress.

Activity wheel running blunts increased plasma adrenocorticotrophin (ACTH) after footshock and cage-switch stress

We examined whether chronic circadian physical activity attenuates hypothalamic-pituitary-adrenal hormone responses after footshock with or without cage-switch stress. Young (45 g) male Fischer 344 rats were randomly assigned to individual suspended home cages (HC) or cages with activity wheels (AW) (12 h:12 h light-dark photoperiod). After 6 weeks, each animal from a pair matched on mass (HC and AW) and average weekly running distance (AW) was randomly assigned to controllable or uncontrollable footshock on 2 days separated by 24 h. Half the animals were returned to the HC after the first day of shock, and half were switched to a new shoebox cage. One animal of each pair could end the shock for both rats by performing an FR-2 lever press. The yoked animal could not control the shock. After shock on Day 2, trunk blood was collected after decapitation. Plasma adrenocorticotrophin (ACTH), corticosterone, and prolactin were determined by radioimmunoassay. ANOVA for a 2 Group (AW vs. sedentary) x 2 Test (controllable vs. uncontrollable shock) x 2 Condition (HC vs. cage-switch) design indicated a Group x Test x Condition effect [F(1, 48) = 5.07, p = 0.03] and a Test main effect [F(1, 47) = 6.93, p = 0.01] for ACTH. ACTH was higher for sedentary animals after uncontrollable footshock under cage-switch conditions and higher after uncontrollable versus controllable footshock when averaged across groups and cage conditions. No effects were found for corticosterone or prolactin. Our results extend to activity wheel running prior findings of a cross-stressor attenuation in plasma [ACTH] in response to cage-switch after treadmill exercise training, though the cross-stressor effect was additive with footshock. Consistent with our prior reports, the cross-stressor effect of wheel running was not apparent after footshock administered under home-cage conditions.

Brain monoamines, exercise, and behavioral stress: animal models

This paper summarizes our studies examining whether changes in levels of brain monoamines after chronic exercise are associated with altered behavioral and endocrine responses to stressors other than exercise. The focus is on using animal models relevant for understanding reports by humans that regular physical activity reduces depression and anxiety. We studied the effects of chronic activity wheel running or treadmill exercise training on levels of norepinephrine (NE) measured in brain cell bodies and terminal regions at rest and after behavioral stress. We also measured brain levels of serotonin, i.e., 5-hydroxytryptamine (5-HT), dopamine (DA), and gamma aminobutyric acid (GABA), which function as both antagonists and synergists with NE. In general, we found that chronic activity wheel running increased NE levels in the pons medulla at rest and protected against NE depletion in locus coeruleus cell bodies after footshock; the concomitant reduction in escape-latency was consistent with an antidepressant effect. Wheel running also decreased the density of GABAA receptors in the corpus striatum while increasing open-field locomotion, consistent with an anxiolytic effect, but had no effect on hypothalamic-pituitary-adrenal cortical response to footshock measured by plasma levels of adrenocorticotropic hormone (ACTH), corticosterone, and prolactin. In contrast, treadmill exercise training increased the metabolism of NE in brain ascending terminal areas for NE, increased the secretion of ACTH after footshock and immobilization stress and had no effect on GABAA receptor density or open field locomotion. The validity of animal models for studying depression and anxiety after forced versus voluntary exercise is discussed. Recommendations are offered for improving the methods used in this area of research.

beta-Endorphin and adrenocorticotrophin after incremental exercise and marathon running--female responses

Investigations of exercise-induced increases in beta-endorphin, adrenocorticotropic hormone (ACTH) and cortisol concentration have been carried out mainly in men. Data concerning the female reaction are sparse and less clear. In a comparison between incremental exercise and marathon running 14 experienced female marathon runners volunteered to run to exhaustion according to an incremental treadmill protocol. They ran a marathon 4 weeks later. Blood was analysed for beta-endorphin, ACTH and cortisol concentration immediately prior to the laboratory treadmill test, 3, 30 and 60 min later, as well as prior to the marathon, after 60 min and 120 min of running and 3, 30 min, and 24 h after completion of the run. At each blood collection, lactate concentration, heart frequency and perceived exertion were determined. The mean marathon running time was 3.22 h. Baseline concentrations for beta-endorphin of 22 pmol.l-1 before the marathon and 19 pmol.l-1 before the treadmill exercise increased 1.4-fold 30 min after the marathon and 1.9-fold after the treadmill exercise; for ACTH the baseline of 4.7 and 4.0 pmol.l-1 was increased by 8.3- and 10.3-fold, respectively. Cortisol concentration rose exponentially from a baseline 17 micrograms.dl-1 and peaked at 2.2-fold 30 min after the run, when the maximal concentration also had been reached after the treadmill test, increasing 1.3-fold from a baseline of 21 micrograms.dl-1. The maximal values for cortisol concentration after both exercises differed from each other, while the maxima of ACTH and beta-endorphin concentrations were similar. The ACTH and beta-endorphin concentration declined more slowly during the recovery after the marathon than after the treadmill. Cortisol concentration was below baseline 24 h later. In comparison with men studied earlier, female marathon runners showed higher baseline concentrations and lesser increases in beta-endorphin and lower baseline concentrations and larger increases in ACTH concentration after both types of exercise. The delayed decrease in concentration of the hormones after the marathon was similar in male and female runners.

Treadmill exercise training and estradiol differentially modulate hypothalamic-pituitary-adrenal cortical responses to acute running and immobilization

It is generally believed that physical fitness promotes health by attenuating responsiveness to other stressors. The experimental evidence for this belief is limited and does not extend to interactions between the hypothalamic-pituitary-adrenal cortical (HPA) and hypothalamic-pituitary-gonadal (HPG) axes. We tested the hypothesis that treadmill exercise training would lead to an estrogen-dependent hyporesponsiveness of the HPA axis that would generalize to immobilization stress. Ovariectomized female Sprague-Dawley rats (N = 74) that had been treadmill trained (TT) or sedentary for 6 weeks received intramuscular injections of estradiol benzoate (Eb) or sesame oil on each of 3 days prior to 15 min of acute treadmill running or immobilization. Plasma (adrenocorticotrophin) (ACTH), (corticosterone) (B) and (prolactin) (PRL) were determined from trunk blood by radioimmunoassay and compared in a 2 group (TT vs. sedentary)-by-2 treatment (Eb vs. oil)-by-2 acute stressor (running vs. immobilization) design. Home-cage (HC) animals (N = 24) provided baseline hormone levels. ACTH and B levels were elevated after stressors in animals treated with either Eb or oil compared to HC, but increases in PRL after stressors were dependent on Eb. Treadmill exercise training led to an attenuation of ACTH and prolactin to running, but the attenuation did not generalize to immobilization. In contrast, treadmill exercise training led to a hyperresponsiveness of ACTH. Treadmill training did not modulate prolactin responses to immobilization. The modulating effects of the estradiol treatment are consistent with an interaction of the HPA and HPG axes in response to stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Stress and endogenous opioids: behavioral and circulatory interactions

Endogenous opioid peptides are the basis of a diverse system of complex neuroregulatory and endocrine mechanisms. While relatively quiescent in the resting state, these peptides are released during intense stimulation and modify, in a number of ways, circulatory homeostatic mechanisms. The endogenous opioids, primarily via endorphins and enkephalins, are capable of influencing circulatory responses to stress at the behavioral, the endocrinological, and the neural level. Recent research in humans and animals has described several roles for opioids in regulation of the circulatory stress response, and has also provided clues about the significance of opioid dysregulation in the pathophysiology of stress. Increased understanding of the basic mechanisms of stress and endogenous opioids will clarify the potential roles of opioids in important pharmacologic and behaviorally based therapeutics.

Aerobic fitness and opioidergic inhibition of cardiovascular stress reactivity

The role of endogenous opioids in aerobic fitness-induced decrements in cardiovascular stress reactivity was examined by comparing the effects of opioid antagonism with naltrexone on responses to stress in young adults with high versus low levels of aerobic fitness. Two hundred forty subjects were given an activity questionnaire and males with the highest (Fit) and lowest (Nonfit) aerobic activity profiles were recruited for maximal oxygen consumption (VO2max) treadmill testing and psychological stress testing (final sample N = 28). Heart rate and blood pressures were measured during performance on a computer-controlled arithmetic task after pretreatment with either naltrexone (Trexan, DuPont) or a placebo. During placebo challenges, Fit subjects, compared with Nonfit, showed lower heart rate reactivity during stress and lower mean arterial blood pressures immediately before and during recovery from stress. Naltrexone eliminated these reactivity differences by increasing heart rate reactivity and raising mean arterial blood pressure in Fit subjects. These data suggest that aerobic fitness is associated with enhanced opioidergic inhibition of circulatory stress reactivity. Opioidergic modulatory effects on stress reactivity may comprise an important mechanism in fitness-associated risk reduction for cardiovascular disease.

Hormonal responses to fighting in hamsters: separation of physical and psychological causes

Male Syrian hamsters were paired and allowed to interact with a conspecific for 15 min a day for 4 days. On the fifth day, the animals were again paired, but they were kept physically separated by a mesh partition that allowed visual, olfactory, and auditory contact between the animals. Controls were placed with conspecifics on each of the 5 testing days, but the partition between them was never removed. Hamsters that were submissive on days 1-4 exhibited elevated plasma adrenocorticotropin-like immunoreactivity (ACTH-LI), beta-endorphin-like immunoreactivity (B-EP-LI), and cortisol on day 5 even though no fighting occurred on that day. Dominant hamsters did not differ from controls. These data support the hypothesis that there is an important psychological component to the pituitary-adrenocortical response in defeated hamsters.

Cholecystokinin, gastrin and stress hormone responses in marathon runners

The purpose of this investigation was to determine the influence of long-distance running on the secretion of the gastrointestinal peptide hormones cholecystokinin (CCK) and gastrin. Several known stress hormones, ACTH, cortisol and norepinephrine, were also measured. The hormones were estimated before and after a competitive marathon run of 46.5 km and under control conditions a few weeks later. Except gastrin, all hormones were significantly higher under prerun conditions than under control conditions and were highest after the run. The most marked prerun elevation was in CCK. Therefore, CCK seems to be an important regulation factor in response to anticipatory stress.