Energetics of backstroke swimming in males and females.

The aims of this study were to compare the oxygen demand of back crawl in male and female competitive swimmers and to examine the effect of stroke mechanics on these costs. Twenty-two male and 16 female swimmers participated in the study. The VO2 increased with v2 to a peak of approximately 4.03 l.min-1 in males and of approximately 2.88 l.min-1 in females. Mean VO2 of the males at a given v was significantly higher than that of the female swimmers, but the slopes of the regression lines were identical. Increases of velocity in both groups were related to increases in f and a decrease in distance. Costs per stroke (ml O2.str-1) in males were significantly higher than in females at a v = 1.0, 1.1, and 1.2 m.s-1. The relationship between VO2 and body mass at v = 1.1 m.s-1 was evaluated by deriving the exponent b in the allometric equation VO2 = a Mb. The exponent b was found to be 0.55. These results indicate that submaximal VO2 in back crawl swimming does not increase in proportion to body mass and may explain why VO2 (l.min-1) has been found to be higher in males than in females.