Effects of changes in physical activity on blood pressure and sympathetic tone.

We investigated the relationship between the level of physical activity and blood pressure (BP). Twelve sedentary normotensive subjects were studied after consecutive one-month periods at four different levels of daily activity. These were minimal activity; usual sedentary activities; exercise three times weekly for 45 min at 60-70% maximum capacity (Wmax) on a bicycle ergometer and similar exercise performed daily. The order of the various levels of physical activity were randomised according to a Latin square. As expected there was a progressive increase in Wmax, maximum oxygen consumption and fall in resting and exercise heart rate with increasing activity. Supine blood pressure averaged 133/69 mmHg at the end of the sedentary period and fell by 10/8 mmHg after one month of exercise three times weekly and 12/8 mmHg after daily exercise (both P less than 0.001). The fall in resting BP with increased activity was due to lowering of total peripheral resistance. These haemodynamic changes were associated with biochemical evidence of marked reduction in overall sympathetic tone in 10/12 subjects especially after the period of daily exercise. Increased physical activity for one month lowers blood pressure in normotensive subjects. The fall with daily exercise is similar to that after some centrally-acting antihypertensive drugs, and may be due to a reduction in sympathetic nervous activity.