ACC is concerned by a "dramatic increase" in young sporting stars becoming injured.
Since 2008, there has been a 60 percent increase in sports-related injuries in kids aged between 10 and 14 - twice as high as the average across all age groups.
ACC sports injury prevention specialist Nat Hardaker said kids should be active, and taking risks and learning from consequences was important, but the increase was worrying.
"Some kids are not doing enough sport and may be injuring themselves when they do play because of a lack of conditioning," Hardaker said.
"Then there are some kids engaging in higher levels of structured sport and training, and not getting enough rest."
Hardasker said it was important for experts to do more research and understand the ways children are engaging in sport.
Sport and exercise physician Dr Dan Exeter said while a lack of physical activity was still a major problem for some, there are other kids doing way too much - particularly in one sport.
"It really is about finding that sweet spot. We have to get kids into that spot and not push them out the other side," said Dr Exeter.
Specialising in one sport may mean missing out on developing a range of physical skills, said Hardaker.
"A more diverse approach can mean fewer overuse injuries, less chance of burnout, and a higher chance of staying in that sport for life."
ACC had five things to keep in mind:
The number of hours per week of structured sports training and competition should be less than the child's age. For example, a 10-year-old should do less than 10 hours per week.
Encourage variety and have children partake in different sports and activities. Avoid training in a single sport for more than eight months per year.
Take the focus off winning and encourage children to enjoy the sport.
Allow children to just be kids and play without structure or competition.
Allow for plenty of rest and recovery time.