Bone and muscles are still growing in children, making them more susceptible. So-called growth plates, where bone is being built, are especially vulnerable to injuries that may disrupt growth and may lead to chronic health problems.

The recommendations are an “easy to follow list” of steps that can reduce injuries in young athletes, said Dr. R. Jay Lee, an assistant professor of orthopedic surgery at Johns Hopkins Medical in Baltimore, who specializes in pediatrics sports medicine.

“The more we get the full complement of health care providers onto the same page, the more parents, coaches and the athletes themselves will buy into this new approach of mandating rest as a key component to a successful athletic career,” he said.

The new recommendations are more detailed and rigorous than those issued by the American Academy of Pediatrics , which in 2012 suggested that children and adolescents take a day off each week to rest and take a month away from sports each year.

The advice also is more limiting than that offered by the American Academy of Orthopedic Surgeons , which includes restrictions on the number of teams youngsters join each season, and a recommendation against playing a single sport year-round.

The six N.A.T.A. recommendations are endorsed by five societies of athletic trainers, including professional football, hockey, soccer, basketball and baseball trainers, as well as the group’s Intercollegiate Council for Sports Medicine. They include:

Delay specializing in a single sport for as long as possible. To support general fitness and reduce injuries, “adolescent and young athletes should strive to participate, or sample, a variety of sports,” N.A.T.A. said.

One team at a time. Youngsters should participate in only one organized sport per season.

Youngsters should not play a single sport more than eight months per year. Breaks in training give overstressed tissues time to recover, evidence suggests.