Numerous studies have shown that intense exercise stimulates the release of arginine vasopressin AVP (aka antidiuretic hormone). It has been well established that AVP acts directly on the emesis center in the brain to induce nausea. This is why people puke after strenuous exercise. Here is one abstract out of many on medline dealing with topic:
J Appl Physiol 1998 Sep;85(3):835-41
Prolonged exercise increases peripheral plasma ACTH, CRH, and AVP in male athletes.
Inder WJ, Hellemans J, Swanney MP, Prickett TC, Donald RA.
Department of Endocrinology, Christchurch Hospital, Christchurch, New Zealand.
We wished to determine whether the increased ACTH during prolonged exercise was associated with changes in peripheral corticotropin-releasing hormone (CRH) and/or arginine vasopressin (AVP). Six male triathletes were studied during exercise: 1 h at 70% maximal oxygen consumption, followed by progressively increasing work rates until exhaustion. Data obtained during the exercise session were compared with a nonexercise control session. Venous blood was sampled over a 2-h period for cortisol, ACTH, CRH, AVP, renin, glucose, and plasma osmolality. There were significant increases by ANOVA on log-transformed data in plasma cortisol (P = 0.002), ACTH (P < 0.001), CRH (P < 0.001), and AVP (P < 0.03) during exercise compared with the control day. A variable increase in AVP was observed after the period of high-intensity exercise. Plasma osmolality rose with exercise (P < 0.001) and was related to plasma AVP during submaximal exercise (P < 0.03) but not with the inclusion of data that followed the high-intensity exercise. This indicated an additional stimulus to the secretion of AVP. The mechanism by which ACTH secretion occurs during exercise involves both CRH and AVP. We hypothesize that high-intensity exercise favors AVP release and that prolonged duration favors CRH release.
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