From the perspective of swimmer safety, there have been no quantitative 3-dimensional studies of the underwater phase of racing starts during competition. To do so, 471 starts were filmed during a meet with a starting depth of 1.22 m and block height of 0.76 m. Starts were stratified according to age (8 & U, 9-10, 11-12, 13-14, and 15 & O) and stroke during the first lap (freestyle, breaststroke, and butterfly). Dependent measures were: maximum head depth, head speed at maximum head depth, and distance from the wall at maximum head depth. For all three there were significant main effects for age F(4, 456) = 12.53, p < .001, F(4, 456) = 27.46, p < .001, and F(4, 456) = 54.71, p < .001, respectively and stroke F(2, 456) = 16.91, p < .001, F(2, 456) = 8.45, p < .001, and F(2, 456) = 18.15, p < .001, respectively. The older swimmers performed starts that were deeper and faster than the younger swimmers and as a result, the older swimmers may be at a greater risk for injury when performing starts in this pool depth.
Cornett, Andrew C.; White, Josh C.; Wright, Brian; Willmott, Alexander P.; and Stager, Joel M.
"Racing Start Safety: Head Depth and Head Speed During Competitive Starts into a Water Depth of 1.22 m,"
International Journal of Aquatic Research and Education: Vol. 4
, Article 4.
Available at: http://scholarworks.bgsu.edu/ijare/vol4/iss4/4