FITT Factors of CR Endurance


As mentioned in Unit 1, a person must integrate several factors into any successful fitness training program to improve their fitness level. These factors are summarized by the following words which form the acronym FITT.

Frequency, Intensity, Time, and Type.

They are described below as they pertain to cardiorespiratory fitness. A warm-up and cool-down should also be part of each workout.


Conditioning the CR system can best be accomplished by three adequately intense workouts per week. People should do these on alternate days. By building up gradually, you can get even greater benefits from working out five times a week. However, you should recognize the need for recovery between hard exercise periods and should adjust the training intensity accordingly. You must also be aware of the danger of overtraining and recognize that the risk of injury increases as the intensity and duration of training increases.


Significant changes in CR fitness are brought about by sustaining training heart rates in the range of 60 to 90 percent of the heart rate reserve (HRR). Intensities of less than 60 percent HRR are generally inadequate to produce a training effect, and those that exceed 90 percent HRR can be dangerous. You should gauge the intensity of your workouts for CR fitness by determining and exercising at your training heart rate (THR).

The Percent MHR Method

With this method, the THR is figured using the estimated maximal heart rate. A person determines their estimated maximum heart rate by subtracting their age from 220. Thus, a 20- year-old would have an estimated maximum heart rate (MHR) of 200 beats per minute (220 -20 = 200).

To figure a THR that is 80 percent of the estimated MHR for a person in good physical condition, multiply .80 times the MHR of 220 beats per minute (BPM) minus age in years. The following example is for a 15-year-old person in good health.


% x MHR = THR

Calculation for a 15-year-old:

.80 x 205 BPM = 164 BPM

A person who is in poor shape should exercise at 70 percent of his MHR; if he is in relatively good shape, at 80 percent MHR; and, if he is in excellent shape, at 90 percent MHR.

A person who maintains their THR throughout a 20- to 30-minute exercise period is doing well and can expect improvement in their CR fitness level. They should check their exercise and post-exercise pulse rate at least once each workout. If they take only one pulse check, they should do it five minutes into the workout.


Time, or duration, refers to how long one exercises. It is inversely related to intensity. The more intense the activity, the shorter the time needed to produce or maintain a training effect; the less intense the activity, the longer the required duration. To improve CR fitness, you must train for at least 20 to 30 minutes at your THR.


Only aerobic exercises that require breathing in large volumes of air improve CR fitness. Worthwhile aerobic activities must involve the use of large muscle groups and must be rhythmic. They must also be of sufficient duration and intensity (60 to 90 percent HRR).

Last modified: Sunday, 19 August 2012, 5:57 PM