Boys Age 10-and-Under Swim Faster Than Girls In Most Long And Short Course Events

Although sex-based differences in youth sports performance have previously been considered minimal or inconsequential, recent research indicates that age 10-and-under boys consistently and statistically significantly run and swim faster, and throw and jump farther, than girls of the same age. However, the swimming data have primarily been comparisons of top ranked swimmer’s best times and not evaluations of race performances within the same swimming meet. PURPOSE. The purpose of this project was to determine if there are sex-based differences when competing at the same swim meet in long course and short course swimming events in athletes under age 10 (who can reasonably be assumed to be prepubertal). METHODS. The top eight performances for males and females from the USA Swimming Eastern Zone Long Course Age Group Championship and Short Course Age Group Championship for the years 2013-2023 for the 10-and-under age group were analyzed for sex-based differences. RESULTS. For the long course (meters) events the males were 1.10% faster (P < 0.05; Cohen’s d 0.336-0.473) than females in the 50 m freestyle, 100 m freestyle, 200 m freestyle, 400 m freestyle, 50 m backstroke, 100 m backstroke, and 100 m butterfly. There were no differences between males and females in the 50 m breaststroke, 100 m breaststroke, 50 m butterfly, or 200 m individual medley (IM). For the short course (yards) events the males were ~ 1.36% faster (P < 0.05; Cohen’s d 0.308-0.638) than females in the 50y freestyle, 100y freestyle, 200y freestyle, 500y freestyle, 50y butterfly, and 100y butterfly. There were no differences between males and females in the 50y backstroke, 100y backstroke, 50y breaststroke, 100y breaststroke, 100y IM, and 200y IM. There were no events for either long or short course in which the females were significantly faster than males. CONCLUSION. Although the present data indicates that the presence or absence of male sex-based advantages in swimming in the 10-and-under age group vary based on course and event, the lack of female sex-based advantages in any event is an important consideration in the ongoing discussion regarding the necessity for sex segregated youth sports.