How to Measure Cardiorespiratory Fitness

What's your aerobic endurance?

Woman running on pier in front of city skyline
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Cardiorespiratory fitness is the ability of the body's circulatory and respiratory systems to supply fuel and oxygen during sustained physical activity. It is a good indicator of how much physical activity you routinely perform. It can be objectively measured in metabolic equivalents (METs) or maximal oxygen uptake (VO2 max) using treadmill or cycle ergometer tests or estimated by using simpler tests.

Cardiorespiratory fitness is an important health indicator and it can predict cardiovascular diseases mortality. Most people can improve it through regular physical activity.

How Is Cardiorespiratory Fitness Measured?

The best test of cardiorespiratory fitness is the peak oxygen uptake, VO2 max, and testing for it is used in research studies. But directly measuring this is difficult, it's usually done on a treadmill wearing breathing apparatus and hooked up to an ECG. That's not something you find in every gym. Instead, you will often perform a submaximal test that has been correlated with VO2 max.

Popular methods to measure your cardiorespiratory fitness include the 1-mile walk test. This is a simple test that requires only a stopwatch, a measured one-mile course (laps around a track is an easy choice), and a way to measure heart rate. It has been well-correlated to estimate VO2 max. It has advantages in that it can be performed by people who may not like to run. 

The 12-minute run test is another popular submaximal test, developed by Dr. Ken Cooper and used by fitness trainers and the military. You warm up and then run or walk as far as you can in 12 minutes. You would need an accurate means to measure the distance, such as how many laps you were able to make around a track, but you don't need to take your heart rate.

With these tests, there are normal values by age and sex to compare yourself to. By taking a test before and after starting an exercise program, you can measure improvements.

Improving Your Cardiorespiratory Fitness

In the case of cardiorespiratory fitness, it's both the years and the miles that determine how fit you are. It goes downhill with age, but you can improve it by putting in the miles on your feet, a bicycle, swimming, skiing, skating, etc.

You can improve your cardiorespiratory fitness in two ways - increasing the intensity of exercise or increasing how much exercise you do. Both will result in improvements. If you prefer moderate-intensity exercise, such as brisk walking, to vigorous-intensity exercises, such as running, you will still have improvement if you work out longer or more frequently.

The minimum amount of aerobic exercise recommended for fitness by the American College of Sports Medicine and the American Heart Association is 30 minutes of moderate-intensity exercise five days per week or 20 minutes of vigorous-intensity exercise three days per week. This is a minimum that people who have been inactive should progress to with steadily increasing their activity. Short bouts of at least 10 minutes of activity can be used to build up to longer durations. 

But you don't have to stop there, more is better. You can increase the length of your workouts by 10% per week as you build your fitness with less risk of injury.

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