Every year in more than 300 cities, over 1 million people participate in the American Heart Association's Heart Walk to raise money and awareness about heart disease. And you can reduce your risk of heart disease by participating.

Walking is great for heart health, but you need to keep it up. A new review reveals how you can do just that.

It looked at evidence from 18 studies that followed healthy adults, tracking whether they walked in groups, alone or not at all.

The researchers found that those who participated in group walking were most likely to stick with it (the researchers checked in at six months). That's because a buddy system builds the 3Cs: commitment, community, and continuity.

So if you and your friends have been talking about starting a walking routine:

• Make a plan with a pal (or two or three or more) and sign a Buddy Exercise Agreement. Google "Making a Buddy Exercise Agreement" for tips and a form.

• For your walks, try different neighborhoods, local trails, or parks.

• Check in regularly with anyone who misses a session to help them get back on track (you'll benefit too).

And don't put it off: Getting outside in the winter sunshine can raise your spirits, boost your vitamin D and help strengthen your bones.

Plus, exercise helps make you less vulnerable to this winter's colds and flu.