Typically, a programme comprises three phases. Warming up for 5 to 10 minutes by stretching and other gentle activity is followed by an endurance or aerobic phase of 20 minutes or longer according to fitness, and finally by a cool-down period of progressively decreasing vigour that permits cardiovascular responses and heat production to subside gradually. In persons who have been sedentary in recent months, in those with known cardiovascular disease or at high risk, and in persons aged more than 40 years, the initial duration and intensity of the endurance phase should be suitably reduced. Ten minutes of gentle activity such as walking may be an appropriate first step, increasing at intervals of one week or longer according to tolerance, as fitness increases. Increments are first achieved by increasing duration.
Later intensity is increased, for example by walking briskly, or by alternate walking and jogging.
Dosage is affected by duration, intensity and frequency of exercise. Intensity can be judged subjectively, or objectively by instructing the subject to monitor pulse rate during exercise. Appropriate pulse rate during aerobic exercise. Mild shortness of breath during exercise should abate within four minutes or less of resting. These target rates are not applicable to patients taking beta blockers and other cardioactive drugs.