Energetics of swimming: a historical perspective.

The energy cost to swim a unit distance (C(sw)) is given by the ratio (E) over dot/v where (E) over dot is the net metabolic power and v is the swimming speed. The contribution of the aerobic and anaerobic energy sources to (E) over dot in swimming competitions is independent of swimming style, gender or skill and depends essentially upon the duration of the exercise. C(sw) is essentially determined by the hydrodynamic resistance (W(d)): the higher W(d) the higher C(sw); and by the propelling efficiency (eta(P)): the higher eta(P) the lower C(sw). Hence, all factors influencing W(d) and/or eta(P) result in proportional changes in C(sw). Maximal metabolic power ((E) over dot(max)) and C(sw) are the main determinants of swimming performance; an improvement in a subject's best performance time can more easily be obtained by a reduction of C(sw) rather than by an (equal) increase in (E) over dot(max) (in either of its components, aerobic or anaerobic). These sentences, which constitute a significant contribution to today's knowledge about swimming energetics, are based on the studies that Professor Pietro Enrico di Prampero and his co-workers carried out since the 1970s. This paper is devoted to examine how this body of work helped to improve our understanding of this fascinating mode of locomotion.