A 55-year-old obese woman wishes to begin an exercise program to lose weight, reduce her risk for heart disease, lower her blood pressure and lower her cholesterol. How should she proceed? First, she should see her doctor and make sure her heart is healthy enough to exercise. If it is, what is the correct dosage of exercise for her? Ideally she should be given an exercise prescription that follows the FITT principle.

FITT is an acronym that stands for Frequency, Intensity, Time and Type. The exercise prescription should give a recommendation, or “dosage”, for each of these parameters. The Frequency of exercise should specify the number of days per week dedicated to an exercise session.  The initial exercise frequency should be three times per week for those just starting an exercise program, like our 55-year-old woman, or for those who are not in good shape.  The frequency can then be advanced to five to seven days per week over time.  For those who already engage in exercise, start at five days per week and then advance.

"I" is for the intensity of exercise or how hard a person works to do the activity.  Intensity may be prescribed in two ways, either based on a person’s perception of how hard the exertion is or to determine a target heart rate.  Perception of exertion can roughly be broken down to moderate and vigorous intensities.  During moderate exertion a person should at least break into a sweat and can talk, but not sing.  With vigorous intensity exercise, a person cannot say more than a few words without pausing for a breath.  A target heart rate approach is based on determining the person’s maximal heart rate.  This can be done in a couple of ways.  A general formula for maximal heart rate is 220 minus the person’s age. For our 55-year-old woman that is 165 beats per minute.  If moderate activity is prescribed, the target heart rate is about 70 percent of the maximal heart rate (or about 116 beats per minute in the example).  For vigorous activity, the target is 85 percent of the maximal heart rate.  A better way to determine the maximal heart rate is with an exercise stress test.  With the stress test, the person exercises to their peak capacity, they can go no further on the treadmill. The heart rate at peak capacity is their maximal heart rate.  The target heart rate can then be prescribed at 10 percent below the maximal heart rate, since it is known that the person can safely exercise to that level.

Sign Up for E-News

The first T is the length of Time in an exercise session.  The session should start with light stretching, followed by 5 to 10 minutes of a low-intensity exercise, such as walking.  The bulk of the session should be exercising at, or near, the target heart rate.  The duration of exercise, or the Time in an exercise session, is typically from 15 to 45 minutes.  This of course depends on the person’s level of fitness; those less fit would start at 15 minutes per session and build up, while those in better shape can start at 30 minutes. The idea is to exercise at or near the target heart rate for the entire Time.  After finishing, cool down with a low-intensity exercise and end with stretching.

The second T refers to the Type of exercise.  Any aerobic activity will do: walking, running, swimming, bicycling, dancing and gardening are all fine.  Aerobic exercise, or cardio, is preferred to weight lifting.  Patients often ask, “What is the best exercise?” The answer is the activity that you would like to do.  Choose an exercise that you enjoy, so the exercise sessions will be more fun and something that you look forward to, rather than being another dreary chore. 

The goal of exercising is, at a minimum, 150 minutes per week of moderate aerobic activity (or about 21 minutes per day) or 75 minutes per week of vigorous activity (about 11 minutes per day).  For better results, target 300 minutes per week of moderate exercise and 150 minutes per week of vigorous exercise. 

What would an exercise prescription look like for our 55-year-old woman?  It would start with a Frequency of three days each week.  Her target heart rate would be 116 beats per minute with a moderate Intensity of activity.  She would be given an exercise Time of 15 minutes and be advised about what Type of activity to engage in.  So to get FITT, head to your doctor and obtain an exercise prescription FITT to your personal specifications.