The Definition of Fitness

After spending countless hours in the gym lifting weights and doing aerobics, how will you know when you’re physically fit? Many of your clients will tell you they just want to get fit. Therefore, it is important to know just what constitutes a general state of physical fitness.

According to the President’s Council On Physical Fitness, being physically fit means, “having the energy and strength to perform daily activities vigorously and alertly, with energy left over to enjoy leisure activities or meet emergency demands.” Your heart, lungs, and muscles should be strong. Your weight and body fat should be within a desirable range. For women, fat should not exceed 25% of their body weight. For men, fat should not exceed 18% of their body weight.

 To determine a level of physical fitness, the Council breaks fitness into 3 measurable parts: Endurance, Strength and Flexibility. Endurance is defined as “the ability to keep moving for long periods of time.” There are two categories of endurance, Cardiorespiratory and Muscular. Cardiorespiratory is the ability of your heart and lungs of supply muscles with nutrients and oxygen. Aerobic exercise like biking, jogging, and swimming can be measured for speed, duration and distance.

Building endurance promotes higher energy levels. Aerobic exercise also burns calories and fat to keep your weight under control. A fit cardiorespiratory system lowers your risk of death from heart attacks, strokes and pulmonary disease.

According to the American College of Sports Medicine, ACSM, the following principles should be applied when developing an exercise prescription to enhance cardiorespiratory fitness:

1. Type of Activity: The activity must use large muscle groups and must be maintained for a period of time.

2. Intensity: The average conditioning intensity for healthy adults is from 60-70% of their functional capacity, referred to as maximum heart rate. Monitoring a target heart rate training zone during exercise is a good way to measure intensity

3. Duration: The duration of the exercise will depend on the intensity of the exercise. Usually activities of lower intensity, such as walking, can last longer than a high intensity exercise like running. Aerobic fitness can also be accomplished by alternating high and low level activities as in walking between brief periods of jogging. The ACSM recommends 15-60 minutes of continuous or discontinuous aerobic activity.

4. Conditioning Frequency: The aerobic activity must be performed from 3 to 5 days a week.

5. Rate of Progression: In the first 6-8 weeks of exercise, significant conditioning effects will occur. The fitness professional will have to adjust the intensity and duration of the activity if progress is to continue.


There are three stages of progression in the aerobic or endurance phase of the exercise prescription:

1. The Initial Conditioning Stage… During the first 4 to 6 weeks, low level activities of 10-15 minutes, at 60-70% of maximum heart rate, are recommended for the average healthy individual. You should also include some stretching and light calisthenics, such as abdominal work.

2. The Improvement Conditioning Stage… Initially, there is a slight increase in exercise intensity. Thereafter, duration of the activity is increased every 2 to 3 weeks. The ACSM warns that older individuals may take longer to adapt to increases in conditioning.

3. The Maintenance Conditioning Stage…Usually after 6 months of aerobic training, the average individual has achieved their goal of general fitness and just wants to maintain. The ACSM states that aerobic conditioning can be accomplished in as few as three 30 minute workouts a week, training at 60-70% of your maximum heart rate. The second type of endurance one must develop to be physically fit is Muscular Endurance.

The President’s Council defines Muscular Endurance, as the ability of your muscles to perform contractions for long periods of time. The number of curl ups one can perform, is a measure of abdominal endurance. Strength is another measure of fitness, and is categorized into two types:

1. Static Strength: How much weight you can hold in place.

2. Dynamic Strength: How much weight you can move.

It is desirable to be strong in order to perform heavy work with less chance for injury. Maintaining strength is more difficult with age and the increasing loss of lean weight. According to the ACSM, strength can be increased through static contractions, as in isometric exercise, or by low repetition exercises. Three sets of an exercise in a 5-7 rep range, will initiate optimal strength gains, when performed three times a week.

The final measure of fitness is Flexibility. The President’s Council defines flexibility as your ability to move muscles and joints through their full range of motion. One way to measure flexibility is to see how close you can come to touching your toes with your legs straight.

Flexibility of muscles and joints will help prevent injury and maintain mobility as you age. Of particular concern, is flexibility in the posterior thigh and lower back. Lack of flexibility here increases your risk of chronic lower back pain.

It is important that stretching is done slowly with gradual increases in the range of motion. The stretch should be sustained from 10 to 30 seconds, and should not cause pain. Stretching exercises need to be performed at least 3 times a week. It is safer to stretch muscles that are already warm. Stretching is best performed after an aerobic session or between sets of resistance exercise. The development of Speed, Agility and Coordination will also enhance overall physical performance. It is also important to do the exercise relative to the area you wish to improve. Exercise is Specific to the activity being performed. If you wish to grow stronger, you will have to lift heavier weights. If you wish to be flexible, you will have to practice stretching, etc.

Now that we know the elements of fitness, let’s translate what we have learned into an exercise prescription for general conditioning. A well balanced exercise session aimed at maintaining overall fitness for the average individual could consist of the following:

1. A 5-minute warm-up doing a low level aerobic activity, such as walking.

2. Twenty minutes of aerobic activity performed at 60-80% of your maximum heart rate, such as jogging or walking on a treadmill , or a combination of walking and jogging.

3. Five minutes of abdominal work to cool down.

4. Twenty-five minutes of weight training. Performing three sets in the 5-7 rep range of the following exercises; Lat. Pull downs or Bent over Rows for a total of 12 sets.

5. Five minutes of stretching, paying particular attention to hamstrings, lower back, calves, and shoulders. The above one hour of exercise, performed a minimum of 3 times a week, will maintain an average level of overall fitness for most people.


The President’s Council On Physical Fitness and Sports, Get fit. How to get in shape to meet the President’s Challenge.

American College of Sports Medicine, Guidelines for Exercise Testing And Prescription, Third Edition, 1986, Lea & Febiger.


These resources are for the purpose of personal trainer growth and development through Continuing Education which advances the knowledge of fitness professionals. This article is written for NFPT Certified Personal Trainers to receive Continuing Education Credit (CEC). Please contact NFPT at 800.729.6378 or [email protected] with questions or for more information.