Twelve-year-old Amanda Starr and her 10-year-old sister, Natalie, use medicine-ball exercises to build muscle. "I can do 15 military-style pushups," says Natalie, a San Diego fifth-grader, noting that six months ago she could do only seven.
The Starr sisters are part of a nascent muscle-strengthening craze among the nation's young. Strength training, once limited to high school football teams, has become a standard workout feature for participants in youth soccer, swimming, wrestling, basketball and baseball. And it is fast catching hold among kids who don't play organized sports at all.
The percentage of health clubs and community gyms offering youth fitness and strength-training programs is on the rise. Meanwhile, even as gym class fades as a school requirement, weight training as an elective is growing in popularity. At Walter Payton College Prep in Chicago, the student body recently persuaded administrators to open the school's weight room an hour before classes start each morning. "There are 20, 30, sometimes 40 kids in there lifting weights before school—girls and boys," says Arlene Bertoni-Mancine, Payton's physical education chief.
Sandy Huffaker for The Wall Street Journal
Natalie Starr, in pink, and her sister, Amanda, practice strength training at home in San Diego with their mother.
The trend is heartening to public-health officials who once opposed strength training for kids but now recommend it as a way to control weight, improve motor skills, increase bone density, normalize blood sugar, lower cholesterol and build confidence. "In the past, PE teachers always emphasized aerobic programs that left bigger kids feeling like failures," says Stephen Ball, a University of Missouri exercise physiologist. "But the weight room is where those kids will develop a love of physical activity."
A large-scale embrace of youth strength-training faces a Catch 22, though. Even the most passionate advocates warn that children should engage in weight training only under expert supervision. But expertise is most common at gyms, health clubs and community centers, where strength-training equipment has often been off-limits to minors. Meanwhile, as more school districts have minimized or eliminated physical education, many school gyms have become the exclusive province of sports teams. "That's the real challenge—providing supervised opportunities for kids in the weight room," says Boyd Epley, director of coaching performance at the National Strength and Conditioning Association, in Colorado Springs, Colo.