Who said girls can't hang with the boys? At least according to one study, the young ladies can perform just as well in certain sports as their male counterparts.

Researchers from Indiana University examined data from USA Swimming-registered boys and girls ages 6 to 19. The total data included 1.9 million swims between 2005 and 2010.

The research showed no difference in swim performances among girls and boys younger than 8 years old. The study also found little difference in 11- and 12-year-olds. It was only when children started hitting puberty, around 13 years old, that boys started beating the girls.

It is a commonly held belief that girls and boys cannot compete equally due to differences in physique and skill, Joel Stager, professor in the School of Health, Physical Education and Recreation at Indiana University at Bloomington and lead author of the study, wrote in an email to ABCNews.com.

"Our data would seem to argue that this is not always the case," he said. "Due to differences in developmental pace it seems to be true that at least in some sports there are periods of time during which girls and boys might be athletic equals."

The increased muscle mass found in boys compared to girls does not happen until puberty, said Dr. David Rubin, a psychiatrist at NY-Presbyterian/Weill Cornell Medical Center.

"As a result, the finding that boys and girls aged 8 and under perform the same in a task driven by muscle mass and function makes sense," said Rubin. "The 11 to 12 year old group is interesting, in that the girls overall are likely taller, and more of them would be in puberty compared to the boys.

The relatively fewer boys that are in puberty in this group, however, are likely developing more muscle mass and increasing performance," Rubin continued. "Overall, the groups again even out."

After everyone hits puberty full swing, results begin to mirror what is expected in adults. Boys, due to their increased muscle mass, will often outperform in tasks specifically related to muscle mass.

"It's important to remember, however, that sports often rely on more than just muscle," said Rubin.

Sports are a place to foster the development of identity, self-esteem, social skills, collaboration, discipline and the ability to perform under stress, experts said.

While authors said they are not suggesting that boys and girls compete against each other, the findings indicate they could.

Nevertheless, Dr. Stephen Cook, a fellow in pediatrics at University of Rochester Medical Center, said "it is far better to participate in regular exercise and active forms of leisure that can be lifelong, like biking, jogging, hiking, swimming, versus competitive sports. Parents can and do role model this in good ways to their children, both boys and girls."