To lose one pound, you have to burn 3,500 calories. Sound tough? Not if you break it down. To lose a pound a week, do an hour each day of any activity that burns an extra 500 calories.

The number of calories you'll burn during aerobic exercise is affected by your body weight, the intensity of your workout, your conditioning level, and metabolism, so burn rates are only an estimate. But here are ten aerobic activities and exercises that blast about 500 calories per hour, based on the weight of a 130-pound woman.

1. Rowing (vigorous effort): 502
2. Running 5.2 mph (11.5 minute mile): 531
3. Ice skating 9 mph: 531
4. Kickboxing: 590
5. Rock climbing (ascending): 649
6. Cross-country skiing (vigorous effort): 531
7. Swimming laps freestyle (vigorous effort): 590
8. Bicycling 14 - 15.9 mph (vigorous effort): 590
9. Walking up stairs: 472
10. Running up stairs: 885

The more you weigh, the more calories you burn while exercising.

Richard Cotton, chief exercise physiologist with MyExercisePlan.com and an advisor with the American Council on Exercise (ACE), a nonprofit organization that certifies fitness professionals, "You may want to try circuit training -- say, 20 minutes on a stationary bicycle, followed by 20 minutes on a treadmill, followed by 20 minutes on a stair climber."

New exercisers should start slowly, advises Cotton. "Anything you're doing will be more than what you were doing, so keep a positive attitude but don't overdo it." He suggests that beginners exercise for half an hour a day with the goal of burning 250 calories, and achieve the remaining 250-calorie deficit through diet.

Those who are acclimated to exercise may face other challenges. "Efficiency is the bane of weight loss," Cotton says. "Muscles naturally work toward efficiency and over time you can hit a weight-loss plateau." When this happens, he advises, circuit training can help you push through. Or try interval training. "While you are going uphill, you are pushing," explains Cotton. "This is followed by recovery time, then, when you're going uphill, you're pushing again." On stationary machines in the gym this pattern looks like "hills" and "valleys."

Circuit training and interval training can be valuable tools in helping you break through a weight-loss plateau.