Fitness Testing: Cardiovascular Fitness

Cardiorespiratory endurance, often called aerobic fitness, is one of the primary components of overall fitness. Aerobic fitness is enhanced when large muscle groups of the body are involved in continuous and rhythmic activity for sustained periods of time, several times a week. This activity strengthens your heart and lungs and makes your muscles more efficient at utilizing oxygen. Cardiorespiratory endurance is important because it has been consistently linked with a markedly lower risk of premature death associated with most of the major causes of death.

Having good cardiorespiratory endurance is exemplified by such feats as being able to run, cycle, and swim for prolonged periods of time. When the large muscle groups of the body are involved in such exercise, the circulatory and respiratory systems increase their activity in order to provide sufficient oxygen to burn fuel and furnish energy for the working muscles.

In the laboratory, scientists assess aerobic fitness by measuring the body's overall ability to use oxygen. This measure is called "Vo2Max" and it is affected by all stages of oxygen use: intake into the lungs, transportation via the blood, efficiency of the heart in pumping the blood, and utilization at the site of the work (the muscles). If you have a fitness assessment performed at our facility, you may see the "Vo2Max" measure on your assessment. The units shown on a Vo2Max test - "mkm" - stand for milliliters of oxygen used per kilogram of bodyweight per minute.

In a lab, a cardiovascular test uses an exercise like running or biking that gets harder and harder as time goes on. While exercising, the person being tested wears a "gas exchange" mask that precisely measures the oxygen and carbon dioxide being inspired and expired. When the subject reaches the limit of their ability to do work, their maximal oxygen usage - Vo2Max - is measured.

Because laboratory measurement of VO2max is expensive and requires highly-trained personnel, various other tests have been developed as substitutes to allow people to estimate their VO2max. While not quite as precise as laboratory measurements, these tests are very good at helping you understand your fitness level and, especially, at seeing your improvement over time.

The fittest athletes in the world range from 65 to 94 mkm, and include cross-country skiers, long-distance runners, and cyclists. "Good" levels for men are above 45 mkm (equivalent to running a mile in under eight minutes), and for women, 40 mkm (a mile in under nine minutes).

To improve cardiorespiratory endurance or VO2max, most experts recommend that the basic aerobic program be conducted three to five times a week, 20 to 60 minutes per session, at an intensity of 50 to 85 percent VO2max (or 60 to 90 percent of the maximal heart rate). As the frequency, duration, and intensity are increased, greater gains in VO2max will be experienced. When improvement of health alone is the goal, lower-intensity physical activity spread throughout the day appears sufficient.