In July, more than 90,000 people jammed the Rose Bowl to see the U.S. team beat China. But you didn’t have to visit the stadium to see team star Mia Hamm – you could watch her in a Gatorade commercial, going one-on-one with basketball legend Michael Jordan.

Fueling the team’s popularity, nearly 4 million girls between ages 7 and 17 play soccer – up from 3 million just eight years ago. Many girls’ sports are posting similar increases, and groups such as the Women’s Sports Foundation say that can improve girls’ health and success in life.

Girls get many of the same benefits from sports as boys: a positive body image, more strength and more self-esteem. But girls often approach games a bit differently.

“Guys tend to take everything as, ‘it’s got to be a win,’” says Dr. Suzanne Corrigan, a spokesperson for the American Academy of Pediatrics. “But women’s attitude is, ‘you do your best.’ In some ways, it’s a better approach.” There was a time when girls “did not do sports,” adds Dr. Corrigan. “We rode bikes; we ice-skated.”

But girls’ interest in sports is encouraged by high-profile role models. “As the girls begin to see more women in key positions on more teams, that will encourage more girls to participate,” says Dr. Corrigan.

Besides soccer’s Mia Hamm, girls can look to such stars as tennis pro Venus Williams and basketball standout Ruthie Bolton-Holifield.

“Any time you play sports, it does something for your self-esteem,” says Ms. Bolton-Holifield, a star of the Sacramento Monarchs of the Women’s National Basketball Association (WNBA). Ms. Bolton-Holifield also played on the U.S. team that won the gold medal at the 1996 Olympics in Atlanta.

“Being an athlete is an example of the power of women,” Ms. Bolton-Holifield says. She spends much of the off season talking to youths about fitness, staying in school and staying drug- and alcohol-free.