Walk or Run?

Which is better walking or running? The Straight Dope has the answers.

The good stuff -> "To return to our main point, running consumes more calories per unit of distance than walking. For a person who weighs 70 kilograms (about 154 pounds), walking at 5 kilometers per hour (3.1 miles per hour) consumes 50 calories per kilometer, whereas running at 10 kph (6.2 mph) consumes 78 calories per kilometer.

Aha, you say, running is better than walking! Not necessarily, even if we narrowly define "better" as "consumes more calories." When you begin a workout your body is metabolizing carbohydrates, but as the minutes tick by you start burning fat--at minute 50 of light exercise, you're chugging along on a 75/25 fat/carb mix. Sixty percent of your maximum aerobic capacity (reached at roughly 75 percent of maximal heart rate, which is generally calculated as 220 minus your age) is optimal for fat burning; as exercise becomes increasingly strenuous you start burning more carbs. Some have seized on these facts to claim that sustained low- to moderate-intensity exercise is a better way to shed flab than going all out. The point is hotly disputed; I merely note that for the significantly overweight, walking can be easier on the heart, joints, etc."

The airy fairy stuff -> "At any rate, calorie consumption isn't the chief goal of exercise; cardiovascular fitness is. The American College of Sports Medicine says you should exercise three to five times a week in 20- to 60-minute sessions intense enough to raise your pulse to between 60 and 90 percent of your maximal heart rate. Such exercise should be aerobic, meaning something like running, brisk walking, biking, swimming, or cross-country skiing, as opposed to, say, weight training. Is running better than walking for this purpose? Depends. Running is certainly more of a workout per unit of time, but if your idea is that 15 minutes of running equals 30 minutes of walking, forget it--sustained exertion is the key. Then again, while any exercise is better than none, if your wife thinks a no-sweat half-hour amble around the neighborhood is the equivalent of your three-mile run, she's kidding herself too."