Quantification of exercise capability and evaluation of physical capacity in man

(1)Every type of exercise is in a sense a unique situation. However, all forms of muscular work do increase the metabolic rate and therefore it is of particular interest to analyse the involvement of the oxygen transport system. The oxygen uptake gives an accurate measure of the aerobic power, and it is highly related to the cardiac output. The VO2 max is under standardized conditions a highly reproducible characteristic of the individual's aerobic fitness. It is however, subject to variations under certain conditions (i.e., after prolonged inactivity, after training, as a consequence of cardiac diseases). The main factor behind such variations in VO2 max is proportional changes in the stroke volume. Therefore a recording of the heart rate during exercise at a given oxygen uptake will reflect these variations in longitudinal studies. Generally speaking, a high heart rate is usually associated with a low stroke volume. However, from this information it is not possible to tell whether this (poor) exercise response was caused by genetic factors, lack of training, impaired heart function, or other factors. (2) Data have been presented suggesting that the maximal transport of oxygen (cardiac output X oxygen content of arterial blood) is limited by the central circulation rather than by the tissues' ability to utilize the oxygen. (3) A multi-stage exercise test on a treadmill or bicycle ergometer will provide a measurement of the rate of work an individual is able to tolerate without symptoms or electro-cardiographic abnormalities...