Energetics of swimming in man

Body drag, D(b), and mechanical efficiency, e, during actual swimming were measured by a new method on 10 men swimming the overarm crawl at velocities, v, of 0.55 and and 0.9/ms in a 60 m circumference annular pool. D(b) measured during swimming was double that for passive towing, as was e. The ratio, e/D(b), was observed to be the same for a given individual at the two velocities, averaging 0.8 kg^-1 x 10^-2, but varied from 0.42 to 1.05 kg^-1 x 10^-2 among individuals. It can be shown theoretically that v = VO₂(net) (e/Db) for aerobic swimming; hence the ratio e/D(b) establishes the velocity a person can achieve for a given VO₂(net) and is an index of individual proficiency in swimming. The reciprocal of e/D(b) is equivalent to VO₂/v, i.e. the energy cost of swimming 1 m. This proved to be independent of the two velocities studied and averaged 58.5 ml O₂/m^-1, about four times the cost of running for men of this size. The basic approach and the quantitative analysis of swimming proficiency in terms of the ratio e/D(b) have promise for the study of many forms of locomotion on or under the water surface.