The characteristics of a low resistance breathing valve designed for the measurement of high aerobic capacity.

The study of physical performance capacity has been of particular interest to the exercise physiologist and many accurate techniques have been designed for the measurement of human performance. The use of maximal oxygen uptake has, since its development by Hill et al in 1924, been regarded as a valuable measure of cardiorespiratory function and used extensively as a criterion of performance capacity of endurance athletes (e.g. Taylor et al, 1955; Saltin and Astrand, 1967; Hanson, 1973).