FREQUENCY, INTENSITY AND DURATION

To provide guidance on how much exercise an individual should do, exercise physiologists have developed equations based on research. It is generally agreed that to develop and maintain physical fitness, the exercise must be performed on a regular basis.

A frequency of about every other day or three days per week appears minimally sufficient. Many individuals exercise more frequently than this, and of course, such additional exercise is acceptable provided that one does not become overtrained and suffer illness or injury.

The intensity of exercise required to produce benefits has been much debated. Regular exercise at 45 to 50 percent of one's maximal capacity is adequate to improve one's physiological functioning and overall health. This level of intensity is generally comfortable for most individuals.

A reliable way to gauge exercise intensity is to measure your heart rate during exercise. An exercise heart rate that is 65 percent of a person's maximal heart rate corresponds to approximately 50 percent of his maximal capacity. Thus, a sedentary 40-year woman has an estimated maximal heart rate of 180 beats per minute. Sixty-five percent of this maximal rate is 117 beats per minute; thus by exercising at 117 beats per minute, this individual is working at about 50 percent of his maximal capacity.

There is a relationship between the recommended duration of exercise and the intensity of exercise. If one exercises at a very high intensity, the duration of the exercise need not be as long to produce physiological changes. At lower intensities, duration must increase. The table presents guidelines for reasonable intensity, duration, and frequency.