Experts say there is no magic to exercise: You get out of it what you put in. That doesn't mean you have to work out for hours each day. It just means you need to work smart. That said, experts agree that not all exercises are created equal. Some are simply more efficient than others, whether they target multiple muscle groups, are suitable for a wide variety of fitness levels, or help you burn calories more effectively. So what are the best exercises? We posed this question to four fitness experts and compiled a list of their favorites.

1. Walking Any exercise program should include cardiovascular exercise, which strengthens the heart and burns calories. And walking is something you can do anywhere, anytime, with no equipment other than a good pair of shoes.

It's not just for beginners, either: Even the very fit can get a good workout from walking.

"Doing a brisk walk can burn up to 500 calories per hour," says Robert Gotlin, DO, director of orthopaedic and sports rehabilitation at Beth Israel Medical Center in New York. Since it takes 3,500 calories to lose a pound, you could expect to lose a pound for every seven hours you walk, if you did nothing else.

Don't go from the sofa to walking an hour day, though. Richard Cotton, a spokesman for the American Council on Exercise, says beginners should start by walking five to -10 minutes at a time, gradually moving up to at least 30 minutes per session. "Don't add more than five minutes at a time," he says. Another tip: It's better to lengthen your walks before boosting your speed or incline.