For athletes and nonathletes alike, stretching to keep muscles limber may help prevent cramping later in life. Ian Stewart/AP hide caption

itoggle caption Ian Stewart/AP

Despite public health messages about exercise and eating healthfully, many children are acquiring what used to be considered "adult diseases," like diabetes and high blood pressure. M. Spencer Green/AP hide caption

itoggle caption M. Spencer Green/AP

After being treated with shampoos and lotions containing insecticides for many years, some lice have become resistant to treatment. Dr. David Phillips/Corbis hide caption

itoggle caption Dr. David Phillips/Corbis

As we age, our muscles deteriorate, and they don't repair as quickly as they used to. But the good news is that exercise and weightlifting can still make muscles stronger. Al Bello/Getty Images hide caption

itoggle caption Al Bello/Getty Images

A weakening immune system makes inoculations both more important and less effective for the elderly. But scientists can "trick" the immune system into a younger response by adding a little extra oomph to vaccines for older people via chemicals called adjuvants or larger doses of the vaccines. Nick Ut/AP hide caption

itoggle caption Nick Ut/AP

Many schools have made an effort to get rid of unhealthy snacks and educate students about nutrition. Elementary students in Gilbert, Ariz., check out the fruit and vegetable choices as a part of a school lunch program called "A to Z Salad Bar." Tim Hacker/AP/East Valley Tribune hide caption

itoggle caption Tim Hacker/AP/East Valley Tribune
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