'Physical Fitness cannot be defined nor can differences be detected by means of a few simple physiological measurements ... obtained during limited tests ... to do so results in focusing attention on some erroneous concept. Man is not a pulse rate, a rectal temperature, but a complex array of of many phenomena ... into performance enters the baffling yet extremely important factor of motivation - the will to do.

This cannot be measured and remains an uncontrollable, quickly fluctuating, disturbing variable which may at any time completely alter the performance regardless of physical or physiologic state.'