The determinants of performance in master swimmers: a cross-sectional study on the age-related changes in propelling efficiency, hydrodynamic position and energy cost of front crawl

The decrease in swimming performance (v (max)) that occurs with age is a not only consequence of the physiological decrease in maximal metabolic power () but can also be expected to depend on an increase in the energy cost of swimming (C) In turn, for a given speed and stroke C = W (d) / (eta(P)eta(o)) where W (d) is hydrodynamic resistance, eta(P) is propelling efficiency and eta(o) is overall efficiency. The aim of this study was to measure C in 47 male masters (31-85 years old) swimming the front crawl at sub-maximal, aerobic, speeds. During the experiments propelling efficiency and projected frontal area (A (eff), an index of W (d)) were also determined by kinematic analysis. "Elder" masters (60-80 years) swam at a significantly slower pace (0.65 vs. 0.91 m s(-1)), with a lower eta(P) (0.23 vs. 0.31) and a larger A (eff) (0.39 vs. 0.23 m(2)) than "younger" masters (30-60 years). No significant differences in C (1.45 kJ m(-1), on the average) were observed as a function of age or speed, but C values were significantly higher than those assessed in young elite swimmers at the very same speeds; the difference increasing with age with a rate of 0.75 % per year. With the due considerations (in this study the observed changes in eta(P), A (eff) and C can be either attributed to changes in speed or age) these data confirm the hypothesis that an increase in C contributes to the decrease in swimming performance that occurs with age.