They say an apple a day keeps the doctor away, but 30 minutes of exercise might be even better. It's true: Just half an hour of aerobic activity each day can reap enormous health benefits. Here's a list of some of the benefits you can enjoy just by getting active 30 minutes each day:

* Reduce your risk for heart disease. Studies keep finding evidence that supports this simple fact: Exercise improves your heart health, lowers your blood pressure, reduces plaque-buildup in your arteries, and lowers your risk for heart attack. Also it strengthens your heart muscle, making it pump blood more efficiently and with fewer beats.

* Increase your stamina. The more exercise you get every day, the more strength and stamina you'll eventually have. Going up a few flights of stairs or hauling a hefty bag of kitty litter into your house won't leave you so winded.

* Increase your life span. People who engage in regular exercise generally live longer than those who don't exercise at all. Exercise keeps your blood pumping and wards off a lot of health risks. In fact, it even strengthens immune system so that it can better fight off viruses, flu, and colds.

* Improve your mood. Exercise is a great release and can help you maintain a more balanced mood. It can also reduce stress.

By just investing 30 minutes of your time each day into exercising, you get all these benefits and more. It doesn't even have to involve expensive gym equipment. Going for a walk, dancing, swimming, running up stairs, or riding a bicycle can all do the trick. You don't even have to do it all at once, either: You can break it all up into 5 or 10 minute sessions. It adds up.