Differences in the energy cost between children and adults during front crawl swimming

There is little information available about the swimming economy of children. The aim of this study was to examine any possible differences in swimming economy in children and adults, swimming front crawl submaximally. Swimming economy was compared in adults [n=13, aged 21.4 (3.7) years] and children [n=10, aged 11.8 (0.8) years] tested at four submaximal 6-min workloads. Oxygen consumption (V̇O₂) was measured with Douglas bags in a 25-m pool and pacer lights were used to control the velocities. Swimming economy was scaled to body size using mass (BM), body surface area (BSA) and body length (BL). Children had lower V̇O₂ (litres per minute) at a given velocity than the adults, with 1.86 (0.28) and 2.39 (0.20) l min⁻¹ respectively (at 1.00 m s⁻¹). When scaling for size, children had higher V̇O₂ measured in litres per square metre per minute and millilitres per kilogram per minute (divided by BSA and BM) than adults. The V̇O₂ divided by BL was found not to differ between the two groups. The O₂ cost of swimming 1 m at a velocity of 1.00 m s⁻¹ was lower in the children [31.0 (4.6) ml m⁻¹] than in the adults [39.9 (3.3) ml m⁻¹ P<0.01], probably due to a lower total drag in the children. The results also showed that for children a relationship between swimming velocity cubed and V̇O₂ exists as shown earlier for adults. It is concluded that, when scaling for BSA and BM, children are less economical than adults, when scaling for BL, children are equally economical, and when considering energy cost per metre and absolute V̇O₂, children are more economical than the adults.