Running in extreme temperatures may increase calorie burn, according to the American Council on Exercise. In very hot weather, the body uses extra energy for perspiration to keep cool. In the winter, runners wearing heavy footwear might see a slight increase in caloric expenditure. However, a University of Utah study suggests that the added calorie burn is quite small, especially compared to other factors like running intensity, duration and body weight. For busy moms looking for an efficient calorie burn, it's important to know which are the really significant factors.
A Matter of Time and Pace
Two of the biggest calorie-burning factors for runners are speed (or intensity, for other cardiovascular exercise) and duration. A runner keeping pace at 8-minutes-per-mile will burn considerably more calories during a medium or long-distance run than someone running 12-minute miles. Another factor affecting calorie burn is duration, or time spent running. Increasing the duration and total distance of your runs will directly increase calorie burn, regardless of outdoor temperature.
Body Weight Counts
A third major factor affecting calorie expenditure during exercise is body weight. For example, a 150-pound woman running 3 miles at 10 minutes-per-mile will burn approximately 340 calories. At the same pace and distance, a 120-pound woman will burn about 272 calories, or 20 percent less. This is because additional weight increases exertion and effort of working muscles. Use a heart rate monitor or reference ACE's calorie expenditure calculator to accurately measure your own calorie burn.
Keep on Burning
When you run, your body continues to burn calories at an increased rate even after your workout is over. This afterburn effect, or post-exercise oxygen consumption, is due to a prolonged elevation in metabolism and hormones after vigorous exercise. According to a study in the "American Journal of Sports Medicine," the greatest afterburn occurs following strenuous, high-intensity exercise. Another study from the "European Journal of Applied Physiology" showed effects of after-burn for as long as 38 hours after exercise.
Calories Still Count
The food you eat won’t necessarily affect calorie burn during exercise, but it does impact overall health. Exercise is an excellent way to burn calories, but physical activity does not warrant "carte blanche" in the kitchen. In fact, the amount of exercise required to compensate for food calories may be surprising. For instance, a 130-pound woman would have to run approximately 3 miles (at a 10 minutes-per-mile pace) to burn the caloric equivalent of a chocolate glazed donut or one slice of medium-crust pizza.