http://www.orthoinfo.org/fact/thr_report.cfm?Thread_ID=410&topcategory=Children
American Academy of Orthopaedic Surgeons
You make the bone that must last your lifetime when you are between the ages of 10 and 18 years old. This bone is known as your "peak bone mass." To reach the best possible peak bone mass, you must get enough exercise and calcium.