Cardiac output, pulmonary ventilation, oxygen consumption, carbon dioxide output and heart rate during and after exercise are so closely interrelated in an individual performing a standard bout of work that fairly accurate estimates of all other factors can be made from the measured value or a single factor. Post-exercise heart rate is frequently used because of the ease and convenience of its measurement.
The exercises employed in physical fitness tests place the systems of the body (particularly the cardiovascular system) under stress. Running on a treadmill, pedalling a stationary bicycle and stepping up onto a stool are frequently used because they involve large muscle groups in fairly heavy work but do not demand unusual skills.
Performance is measured by the maximal duration of the effort or by the maximal amount of work accomplished. Physiological effect is estimated from the magnitude of the heart rate changes during exercise and from the rapidity of return of the heart rate to normal following the exercise.
There is a voluminous literature on physical fitness tests and testing. The reader is referred to an excellent review and to articles dealing with applications to industry, to physical education and to medicine.
A test of physical fitness for strenuous exertion has been used successfully to detect alterations in physical condition in subjects on reduced calorie intake and with restricted vitamin B complex in the diet. A modification of the test has been used to evaluate the results of programs of physical training.
The test may be administered periodically to determine whether tim the optimal amount of training is being given, to segregate students into classes so that work will not be too hard for some and too easy for others, and to determine when a student has improved enough to be shifted to another class in which he will receive optimal training. Further modifications of the fitness test have been used in programs of rehabilitation and convalescence and in a study of neuro-circulatory asthenia.