Adults have lower stroke rate during submaximal front crawl swimming than children.

The aim of this study was to examine the effects of body size and propelling surface size on stroke rate (SR) and stroke length (SL) during front crawl swimming. Eleven children [11.7 (0.8) years] and 13 adults [21.4 (3.7) years] were compared. A third group of swimmers (n=5) had their propelling surface altered experimentally, swimming with hands only and using small- and large-sized paddles. Underwater videography was used to analyze four 25-m submaximal and four 25-m maximal swims for SR, SL, velocity (v) and hand slip. The results showed that adults have a lower SR at any submaximal v and a lower slope of the relationship between SR and workload (v(3)) compared to children. At 1.0 m s(-1) the SR values were 0.38 (0.04) and 0.58 (0.06) cycles s(-1) for adults and children respectively ( P<0.01). Adjusting for body size did not change this relationship [0.46 (0.05) and 0.67 (0.08) cycles s(-1) at a v of 1.0 bodylength s(-1) for adults and children respectively, P<0.001]. SL, adjusted for potential anatomical SL, was found to be longer in adults at submaximal velocities but not at maximal v. Hand slip was found to be lower for adults [-0.19 (0.14) and -0.36 (0.18) m for adults and children respectively, P<0.05]. Thirty per cent of the variations in slip could be attributed to propelling size. Increased propelling surface reduces SR and increases SL. It was concluded that adults have a lower SR both at absolute and size relative velocities compared to children; the causes could not be attributed to differences in body size, but probably the propelling size and swimming technique make the adults more effective swimmers.