Abstract

Epinephrine responses to hypoglycemia and to identical relative work loads have been shown to be higher in endurance-trained athletes than in untrained subjects. To test the hypothesis that training increases the adrenal medullary secretory capacity, we studied the effects of glucagon (1 mg/70 kg iv), acute hypercapina (inspired O2 fraction = 7), and acute hypobaric hypoxia (inspired PO2 = 87 Torr), respectively, on the epinephrine concentration in arterialized hand vein blood in eight endurance-trained athletes and seven sedentary males. In response to identical increments in glucagon concentrations, plasma epinephrine increased more in T than in C subjects. In response to hypercapnia, the increment in epinephrine was significant in T but not in C subjects. Hypoxia increased epinephrine in T but not in C subjects. The plasma norepinephrine concentration never changed, whereas heart rate always increased, the increase being higher in T than in C subjects only during hypercapnia. The results indicate that training increases the capacity to secrete epinephrine. Verf.-Referat