by Sue Beckham PhD
With swimsuit season around the corner you might be looking for new ways to lose those last few pounds. Since squeezing in an extra workout may be hard to do with a busy schedule, you might consider increasing the intensity of one or two workouts each week to boost calorie burning post exercise.
A recent study published ahead-of-print in Medicine and Science in Sports and Exercise1 examined the effect of 45-minutes of vigorous exercise on metabolism. Ten conditioned, healthy males participated in initial testing for body fat and aerobic capacity. Then their caloric expenditure was measured on two different days in a metabolic chamber, a specially designed living chamber that measures the heat produced by the body to determine caloric expenditure. (Note: A metabolic chamber is the gold standard for measuring caloric expenditure. The subjects actually exercise and live in the chamber for 24 hours at a time.)
Previous studies have used a different technique to measure caloric expenditure called indirect calorimetry. This method estimates caloric expenditure based on the amount of gases exhaled during a variety of activities. This method is not as accurate as using a metabolic chamber and most of these studies did not tightly control the amount of activity that subjects performed throughout the day or their food intake. Another advantage of the metabolic chamber is that subjects don’t have to wear a face mask while performing their activities while one is required when using indirect calorimetry. The metabolic chamber creates a testing environment which is very similar to performing activities of daily living outside the lab.
After completing the initial testing, subjects returned to the lab for two other days of testing. On both days they performed the same activities at the same time including activities of daily living like eating, bathing, and changing clothes. One of these days they also exercised in the chamber riding a stationary bicycle for 45 minutes at 73% of their aerobic capacity. This intensity is equivalent to a steady state workout at 87% of maximal heart rate.
On the day subjects exercised, they burned approximately 520 calories from the exercise and their energy expenditure stayed elevated for 14 hours after the exercise bout. They expended an additional 190 calories during the 14 hours following exercise compared to the day they did not exercise. This means they expended an additional 37% of the workout calories post exercise. Other studies measuring caloric expenditure after moderate-intensity exercise bouts have reported subjects burn an additional 10-15% of workout calories post exercise.
Researchers have found that other forms of high-intensity training such as intervals can also elevate metabolism post exercise. Intensity seems to be more important than workout duration for increasing post workout calorie burn. Certainly, if vigorous exercise is not appropriate for you or not enjoyable, the duration can be extended to burn more calories but you won’t get as much elevation in calorie burn post exercise with moderate vs. vigorous exercise.
Just remember it is easy to get distracted during a workout by others, music or just by ‘zoning out’ which can lead to a drop in intensity. This not only decreases calorie burn during the workout but also post exercise. If your goal is to burn as many calories as possible and you are healthy and ready for vigorous exercise, increasing workout intensity might be enough to help you lose those last few pounds that have refused to go.