Effect of regular exercise on 24-hour arterial pressure in older hypertensive humans

Abstract

The experimental goals were to determine if regular low-intensity aerobic exercise reduces 24-hour arterial blood pressure in middle-aged and older (aged 50 years or older) humans with mild diastolic (90-105 mm Hg) essential hypertension and, if so, whether this is accurately reflected by changes in casual recordings made at rest. Fourteen subjects walked 3-4 days/wk for 6 months, with 10 exercising an additional 6 months; 12 other subjects served as nonexercising controls. In the exercising subjects, maximal oxygen consumption increased 7-14% (p<0.05) with little or no change in body weight or fat. Conventional casual readings of systolic, mean, and diastolic arterial pressure at rest were lower (5-10 mm Hg, p<0.05) in all body positions after 6 months of exercise and changed little thereafter. Casual recordings made during additional circulatory measurements showed 6-month decreases of only half this magnitude and were specific to a particular blood pressure phase and body position; however, all changes were significant after 12 months of exercise. The reductions in arterial pressure at rest were associated with decreases in heart rate (p<0.05) and cardiac output (p<0.05). Ambulatory-determined 24-hour arterial pressure was unchanged after 6 months of exercise, but mean levels were slightly lower (4 mm Hg, p< 0.05) after 12 months due to reductions in daytime (7 mm Hg, p< 0.05) and nighttime (4 mm Hg, NS) systolic pressure; diastolic pressure was unchanged throughout the year of training. In the controls, conventionally recorded casual blood pressure levels were lower after 6 months (p<0.05), but no other changes were observed in any other variable over the 12 months of study. We conclude 1) regular low-intensity aerobic exercise at best produces only small reductions in 24-hour levels of arterial pressure in middle-aged and older humans with mild (diastolic) essential hypertension and 2) training-associated changes in casually determined blood pressure at rest are dependent on the measurement conditions and, most importantly, do not necessarily reflect the magnitude or even the direction of changes in arterial pressure throughout an entire day.