Improving cardiorespiratory endurance shouldn’t be a goal for athletes only. Here’s what personal trainers need to know about this important general fitness variable.

Cardiorespiratory Endurance = Efficiency

Regular aerobic exercise enhances cardiorespiratory endurance by improving the body’s ability to take in and utilize oxygen. A fit cardiorespiratory system has been found to lower the risk of death from heart attacks, strokes, and pulmonary disease – hardly just a bunch “hot air.”

Endurance is defined as the ability to keep moving for long periods of time, preferably in a rhythmic and steady state. Physical endurance can be divided into two types: cardiorespiratory and muscular. Here, we will focus on cardiorespiratory endurance, which is the prolonged ability of the heart and lungs to supply muscles with nutrients and oxygen. For the purposes of training and conditioning, the performance of aerobic activities can be measured in terms of speed, duration, and distance, which can also serve as indicators of an individual’s progress toward a fitness goal.

Developing the Aerobic Phase

Endurance exercise is typically viewed as the primary means of increasing aerobic capacity. The following principles should be applied when developing the aerobic phase of a general fitness exercise prescription to enhance cardiorespiratory fitness:

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

Intensity: The average conditioning intensity for healthy adults is 60-70% of their functional capacity, referred to as maximum heart rate (these terms can sometimes be interchangeable). Monitoring a target heart rate training zone during exercise is a good way to measure intensity.

Duration: The duration of the exercise will depend on the intensity of the exercise. Activities of lower intensity, such as walking, can be maintained longer with ease than a high-intensity exercise, like running. Aerobic fitness can also be accomplished by alternating high and low-level intervals, as in walking between brief periods of jogging for 15 to 60 minutes of discontinuous aerobic activity.

Frequency: Aerobic activity should be performed from 3 to 5 days a week.

Rate of Progression: Sedentary clients should start with just 10-15 minute bouts of activity to acclimate for the first 4-6 weeks. At the 6-8 week point after commencing 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.

Progression of the Aerobic Phase

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

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.

The Improvement Conditioning Stage: At first, there is a slight increase in exercise intensity. Thereafter, duration of the activity is increased every 2 to 3 weeks. Older people may take longer to adapt to increases in conditioning.

The Maintenance Conditioning Stage: Usually after 6 months of aerobic training, the average individual has achieved his or her goal of general fitness and may simply wish to maintain it. Once achieved, this conditioned state can be maintained with as few as three 30-minute workouts per week, training at 60-70% of maximum heart rate.

It should be readily apparent why having a “conditioned” cardiorespiratory system sets the stage for the development of endurance in muscular, muscle strength, and flexibility.

From a functional fitness standpoint, building any kind of physical endurance pays real dividends in terms of higher and more sustainable energy levels, something anyone can appreciate and enjoy each and every day.


1. National Federation of Professional Trainers (2008). Personal Fitness Trainer Manual – The Fundamentals for the Certified Personal Trainer (CPT) (5th ed.) Lafayette, IN: NFPT

2. American College of Sports Medicine, The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness in healthy adults. Med Sci Sports Exerc. 1998;30975-991



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 with questions or for more information.