A long-term program of intense exercise, such as training for a
marathon, may cause blood pressure to increase, according to data presented at the American College of
Sports Medicine meeting.
Dr. Rong Zhang, of the Presbyterian Hospital of Dallas, Texas, and colleagues analyzed the effect of a
12-month progressively intensive exercise regimen in 11 normotensive sedentary adults. They evaluated
the supine blood pressure, cardiac output and total peripheral resistance of the six male and five female
trainees at baseline and 3, 6, 9 and 12 months later. The mean age of the trainees was 29 years.
Dr. Zhang told Reuters Health that the greatest blood pressure benefits were obtained when the exercise
regimen consisted of a 30-minute walk or jog three times a week. After 3 months of such exercise, the
group's mean blood pressure dropped to 116/62 mmHg from a baseline mean of 126/74 mmHg.
The researchers detected only a slight dip in blood pressure at 6 and 9 months. And by the 12-month end
point, when the regimen intensified to running 7 to 9 hours a week and included high-intensity 3.5-hour
runs, the group's mean blood pressure had risen to 123/69 mmHg. This blood pressure reversal reflects
the phenomenon of "overtraining," Dr. Zhang told Reuters Health.
The researchers noted an increase in the group's cardiac output and a decrease in total peripheral
resistance from baseline through 3, 6 and 9 months. By 12 months, cardiac output had decreased and
total peripheral resistance had increased to near baseline levels.
Exercise seems to decrease blood pressure by decreasing peripheral vascular resistance, Dr. Zhang said.
At a higher intensity level, however, exercise seems to trigger peripheral constriction, thus reversing some
of the benefits obtained through moderate exercise.