Cardiorespiratory fitness (CRF) describes an individual’s ability to take in and utilize oxygen, quantifying the effectiveness of the body’s lungs, heart, blood vessels, blood and muscles during exercise. CRF is typically measured in milliliters of oxygen consumed per kilogram of body weight per minute (mlŸ kg^-1Ÿ min^-1) and expressed as maximal oxygen consumption, or VO_2max. Normal values depend on sex, age, physical training, body size and genetics. Maximal exertion testing is not always desirable or feasible in some settings, so submaximal testing is better for the general population. Assessment tests used to predict VO_2max use exercise and post-exercise heart rate during a standardized submaximal exercise performed on a bicycle or step test.

The Modified Canadian Aerobic Fitness Test (mCAFT) is a step test that predicts an individual’s cardiorespiratory fitness. It is an effective way to indirectly measure VO_2max because it requires little equipment to conduct and is safe for the majority of the population. The test requires the individual to step up and down on a standardized step at a set pace, while heart rate is monitored. After the test, the recovery heart rate and blood pressure are measured. The lower the recovery heart rate and blood pressure, the more fit the individual.

The YMCA test is a submaximal cycle test also used to estimate VO_2max. The individual performs three stages, each consisting of three minutes, against a workload on a bicycle. Heart rate response during each workload is monitored to ensure that it stays between 110 beats per minute and 85% of the age-predicted maximum heart rate for the individual. Estimated VO_2max is used to determine CRF rating.