The benefits of resistance weight training include weight loss, body definition and boosts to metabolism and self-esteem.
Yet the belief persists that weight training is ill-advised for children, leading to stunted growth and other injuries.
According to the American Academy of Pediatrics, strength training does not hamper growth development and could even help prevent sports-related injuries.
"It's safe as young as age 8," says Dr. Eric Small, chairman of the committee on sports medicine and fitness for the American Academy of Pediatrics.
"There's no evidence of loss in flexibility. That's an old wives' tale," says Dr. Erol Yoldas, a Fort Lauderdale sports medicine physician. "The studies don't show any risk if an 8-year-old wants to do some basic weight training. It seems OK but basic supervision is an issue."
Dr. Tracie Miller, a professor of pediatrics at the University of Miami, agrees. Miller has encouraged her three older children, Emma, 11, and Hannah, 17, both soccer players, and Zach, 15, a pitcher, to lift weights.
Weight training can help children learn to control their muscles and can aid bone growth and development, the AAP says.
However, there are caveats.
Don't expect - or push - Junior to become an Ahnold Mini-Me.
Small notes that children younger than 10 will not derive that much of a benefit from resistance training.
Parents should concern themselves with issues beyond chronological age and look to psychological maturity, notes Dr. Shawn E. Hunt, a physical therapist with the University of Miami. A weight room is not a playroom.
Training for specific sports requires different methodologies. Football players try to bulk up, requiring lifting heavier weights with less repetitions. Tennis players, gymnasts and swimmers want to improve muscle and endurance so they use lighter weights and more reps.
In general, the latter is recommended for avoiding injuries. One set of 10 to 15 repetitions, twice a week, combining upper and lower body muscle groups, for instance.
Above all, "at any age, but especially under 15, people should be supervised by a qualified adult," Small says.
Still, not everyone is a proponent of starting children on weights early.
Personal trainer Marco Borges, owner of South Beach's The Sporting Club, says prepubescent children should be doing sit-ups, push-ups and jumping jacks - but not weights.
"They are still growing and the growth plates are not closed yet. I'd rather see them doing calisthenics, which builds endurance and muscular strength without placing undue stress on the skeletal frame."
(c) 2004, The Miami Herald. Distributed by Knight Ridder/Tribune News Service.