LuÃs B. Sardinha,
This study analyzes the relationship between intensity and duration of physical activity and composite indices of femoral neck strength and bone-mineral content of the femoral neck, lumbar spine, and total body in 143 girls and 150 boys. It finds that daily vigorous physical activity for at least 25 minutes seems to improve femoral neck bone health in children, although there are discrepancies between genders. The lumbar spine is not affected.
Pediatrics, 122(3), 09/2008, 728-736.