Doctors say it’s never too early to start protecting against bone problems.
Swedish researchers followed more than 800 children for six years.
The kids had 40 minutes of physical activity a day during school.
The researchers documented reports of fractures and compared the results to those of a similarly-aged control group that had 60 minutes of physical activity over a week.
Children who exercised daily had about half as many fractures as those who exercised less.
They also showed higher bone density.