from WHO-ISH 1999 Guidelines

Increased physical activity
Sedentary patients should be advised to take up modest levels of aerobic exercise on a regular basis, such as a brisk walk or a swim for 30-45 minutes, 3-4 times a week. Such mild exercise may be more effective in lowering the blood pressure than more strenuous forms of exercise such as running or jogging, and may lower the systolic pressure by about 4-8 mmHg. Isometric exercise (e.g. heavy weight lifting) can have a pressor effect and should be avoided.