Miriam E. Nelson, Ph.D Responds:

Miriam E. Nelson, PhD, of Tufts University and the best-selling author of the Strong Women book series, responds: You're doing great! It's best not to mess with a good thing, but since you asked-ideally you need to pump iron two or three times a week to help maintain muscle mass and bone. You could swap out a swim or walk to do some weight training-and target all major muscles in just 20 minutes. Along with helping you maintain your weight and reduce the risk of osteoporosis, this change may increase your flexibility, balance, and coordination. Another benefit: Everyday tasks that require short bursts of strength, such as lifting grandkids, carrying groceries, and hoeing your garden, may be easier.