Structural Differences Affecting Performance

Variations in the position of the muscular attachments, the structure of the joints and the lengths of the bony levers all affect the performance of physical activity. Usually when the anatomical structure is particularly advantageous for strength, it is disadvantageous for speed. Large joints are strong, but they also may limit motion. Long distance runners are observed to have the flattest longitudinal arches and sprinters have smaller feet and higher arches.

Although physique plays an important part in severe exercise it plays only a minor role in determining a person's response to moderate exercise. Severe exercise is best performed by those with a slim body build. In general, those with thin legs have better endurance. Those with a normal or stocky build have, on the average, the greatest speed, the greatest strength and the greatest ability to sustain prolonged moderate muscular effort. Good muscular development is required for success in activities requiring speed and strength.

Size and Energy Exchange During Work

Differences in body size affect the energy exchange during physical activity. Even at rest a large man may consume as much as 58 per cent more oxygen than a small man. During light work (simulating operation of an airplane), the large man may require 42 per cent more oxygen than the small man. Among men the correlation coefficient between the oxygen consumption and body surface was plus 0.76 at rest and plus 0.82 at work. Because of the larger energy requirement during work the large man accumulates heat under conditions in which the smaller man attains a heat balance. The ratio of heat production to surface area in a 218 pound man was observed to be 20 per cent greater than in a 97 pound man.