TIME-COURSE OF THE ANTIHYPERTENSIVE AND AUTONOMIC EFFECTS OF REGULAR ENDURANCE EXERCISE IN HUMAN-SUBJECTS

To assess the role of different factors on the long-term antihypertensive effect of regular exercise we examined the time course of changes in haemodynamics, oxygen consumption and plasma noradrenaline in 10 normal healthy subjects. For 12 weeks, subjects performed alternating months of training and detraining in a random order. Training involved 40 min of bicycle exercise three times per week at 60-70% of maximum work. Steady-state changes at the end of 1 month's exercise were: (1) falls in resting blood pressure when supine and erect by 8/5 and 10/6 mmHg, respectively (P < 0.01); (2) a reduction in the total peripheral resistance index of 14%; (3) an increase in maximum oxygen consumption of 14% (P < 0.005); and (4) a fall in plasma noradrenaline of 21% (P < 0.05). A significant fall in blood pressure occurred at the third training bout (P < 0.005), at the beginning of the second week, and no further reduction occurred beyond the fourth bout of exercise. The reduction in plasma noradrenaline concentration was confined to the second half of the month in which exercise took place and lagged behind the blood pressure changes. There were significant differences between the rates of the initial fall of blood pressure and noradrenaline, and the times taken for the maximum changes to occur (P < 0.05). During detraining, blood pressure remained low for 1—2 weeks after cessation of exercise, as did plasma noradrenaline. Both then rose gradually towards the initial sedentary levels. We conclude that non-autonomic factors related to the fall in total peripheral resistance are likely to be important in the initial lowering of blood pressure, while autonomic factors contribute to the maintenance of lower blood pressure later in training and for some time during the detraining period. © Current Science Ltd.