Background Despite the fact that swimming is often recommended for the prevention and treatment of hypertension, no study has examined the potential efficacy of regular swimming exercise for lowering the blood pressure in hypertensive humans.

Objective To test the hypothesis that regular swimming exercise lowers the resting blood pressure.

Design A 10-week closely supervised swimming training program compared with a non-exercising control group.

Patients Eighteen previously sedentary men and women [aged 48 ± 2 years (mean ± SEM)] with stage 1 or 2 essential hypertension.

Results The resting heart rate, an index of cardiovascular adaptation, decreased in the swimming training group from 81 ± 4 to 71 ± 3 beats/min (P < 0.01). The body mass and body fat percentage did not show statistically significant changes. The systolic blood pressure of patients in the seated position fell significantly (P < 0.05) from 150 ± 5 to 144 ± 4 mmHg. The seated diastolic blood pressure did not change significantly. A similar magnitude of reductions in systolic blood pressure (P < 0.05) was also found in patients in the supine position. No significant changes in plasma catecholamine concentrations, casual forearm vascular resistance, plasma volume and blood volume were observed. There were no significant changes in any of these variables in the control group.

Conclusion Swimming training elicits significant reductions in arterial blood pressure at rest in individuals with hypertension. This is a clinically important finding since swimming can be a highly useful alternative to land-based exercises for hypertensive patients with obesity, exercise-induced asthma, or orthopedic injuries.