Buoyancy, gender, and swimming performance

This study investigated the relationship of gender and buoyancy to sprint swimming performance. The center of buoyancy (CB) and center of mass (CM) were measured using reaction board principles. Performance was evaluated as the time needed to complete the middle 13.7 m of a 22.9-m spring for kicking and swimming trials. Nineteen female swimmers (mean ± SD, 21.9 ± 3.2 years) had significantly more body fat (24.1 ± 4.5%) than 13 male swimmers (21.7 ± 4.2 years, 14.8 ± 5.0%). Males swam and kicked significantly faster (p <.01) than females. Percent body fat, upper body strength, the distance between the CB and CM (d), and the buoyant force measured in 3 body positions all met the criteria for entrance into a regression equation. When gender was not controlled in the analysis, these variables accounted for 70% of the variance in swim time (p < .008). When gender was controlled in the analysis, these variables accounted for 45% of the variance in swim time (p = .06). Percent body fat accounted for the largest amount variance in both regression analyses (39%, p < .001; 18%, p = 0.02, respectively). Upper body strength accounted for 14% of the variance in swim time (p = .006) when gender was not controlled but only 4% when gender was controlled (p = .27). The distance d as measured in a body position with both arms raised above the head was the buoyancy factor that accounted for the greatest amount of variance in swim time (6% when gender was not controlled, p = 0.06, 10%; when gender was controlled, p = .07). Percent body fat, d, and the buoyant force accounted for no significant amount of variance in kick time. These data suggested that a swimmer's buoyancy characteristics did have a small but important influence on sprint swimming performance.