Feeling sore from hauling around both your dance and your school bags? According to Matthew Dobbs, M.D., young girls are more prone to back pain than boys since girls usually weigh less, but carry the same amount. Solutions? Dobb advises lightening your load by limiting personal items. He also recommends choosing a backpack, which has two straps, evenly distributing the weight on both shoulders. A University of Alberta study says that weight lifting, rather than aerobic exercise, gives fast improvement. So try doing a couple of sets of back rows with five pounds weights three times a week. You can also load up on foods packed with Vitamin D (like dairy or eggs). Vitamin D helps your bones absorb calcium, making your back stronger.