Altered cardiovascular responsiveness to adrenaline in endurance‐trained subjects

The influence of physical training on responses to i.v. adrenaline infusions and to exercise were investigated in 10 endurance‐trained men (mean age: 35 y; Vo2max: 61.9 ml kg‐1min‐1) and 10 age‐matched and sedentary controls (36 y, 37.5 ml kg‐1min‐1). The untrained subjects were reinvestigated after a 4 month training period which increased their Vo2max by 18%. Resting heart rate and diastolic blood pressure were significantly lower in the trained state. The venous plasma adrenaline concentrations attained during infusions (4 dose levels, 8 min each) were lower in the well‐trained than in the untrained subjects(2.15vs.3.59 nmol 1‐1at the highest dose level,P< 0.01). The adrenaline‐induced increases in heart rate and in plasma cAMP and decreases in pre‐ejection period (PEP) and PEP/LVET ratio were not dependent on the training state. The adrenaline‐induced decrease in diastolic blood pressure was more pronounced (P< 0.05) in the well‐trained than in the untrained group and tended (0.05 <P< 0.1) to be enhanced by training in the latter group. The increases in systolic blood pressure were greater in the well‐trained subjects (P< 0.01) but training did not alter this response in the untrained subjects. The plasma noradrenaline response to maximal cycle ergometer exercise (Vo2maxtest) was significantly greater in the well‐trained than in the untrained subjects, while no difference was seen for adrenaline. The submaximal exercise systolic blood pressure was similar in all training conditions when related to the absolute rate of work. In summary, the present results indicate that both the vasodilator and systolic pressor responses to adrenaline are enhanced in endurance‐trained subjects. The cardiac chronotropic and inotropic effects of adrenaline seem, however, to be independent of the training state.