It is well documented you will burn significantly more calories while running compared to what you burn at rest or during less demanding physical activities. There is more controversy regarding what happens after your exercise bout. Any elevation of your metabolism after a running session will contribute to the energy you expend throughout your day and help to reduce your fat stores. This is why it is important to determine whether running provides benefit beyond the direct calorie burn during the bout.
Calorimetry
Metabolism is the sum total of processes occurring in a living organism. Metabolic processes are energetic events that require the conversion of chemical energy in the foods we eat to usable form. This transformation is not 100 percent efficient, so heat is given off. This is why metabolic rate is indicated by the rate of heat production. Direct calorimetry involves measuring heat produced by a living organism to obtain a measure of metabolism. This is technically difficult, so researchers typically use indirect calorimetry, which is based on the fact that all metabolic processes ultimately depend upon oxidation. This means that the amount of oxygen you consume can be used to estimate your metabolic rate.
Resting Metabolic Rate
Your resting metabolic rate (RMR) is the amount of energy you expend at rest. The average person consumes 3.5 milliliters of oxygen per kilogram of body mass each minute to satisfy their RMR. While it depends upon the fuel that is metabolized, on average, five kilocalories are expended when a liter of oxygen is consumed. This means that a person burns approximately one kilocalorie per kilogram each hour at rest. Any oxygen consumed above RMR indicates increased metabolic activity.
Running Calorie Burn
The American College of Sports Medicine has developed formulas to estimate the additional oxygen that must be consumed to support the energy expense of running. These formulas indicate that running 6 mph on a flat surface requires 10.2 times the resting oxygen consumption. This means that a 150-lb. person will consume 2.4 liters of oxygen each minute while running at this pace and this equates to a kilocalorie burn of 12 per minute. Increasing the speed and/or grade will increase oxygen consumption and calorie burn beyond these levels.
Post-Exercise
In the recovery period following exercise, oxygen consumption is increased. This is called excess post-exercise oxygen consumption or EPOC. As suggested by researchers Borsheim and Bahr, the duration of EPOC is affected by differences in the intensity and duration of the preceding exercise bout. This is why some prior studies have shown it to be substantial while others indicate it is transient and minimal. Differences in exercise mode and conditioning level of subjects might also explain previous disparate findings, the researchers conclude.
EPOC after Running
According to Borsheim and Bahr, EPOC increases linearly with increasing exercise duration and curvilinearly with increasing exercise intensity. This means that you will burn more calories after running if you run for a longer and at a higher speed and/or grade. There is also evidence to suggest that high-intensity interval running results in greater EPOC compared to a continuous sustainable bout.
For example, 20 repetitions of 60-second sprints at extremely high speed with two-minute rest periods resulted in a nine-hour EPOC that averaged 15 liters of oxygen compared to seven liters after 30 minutes of the sustained effort. This means that after high-intensity interval running, subjects burned approximately 75 kilocalories more than they would have had they not performed the exercise bout. However, the EPOC of 15 liters was only 14 percent of what was required to perform the actual bout, which means that the major contributor to calorie burn was still the amount of oxygen subjects consumed while they ran.
References
- "Exercise Physiology: Human Bioenergetics and Its Application"; G.A. Brooks, et al.; 2005.
- "ACSM's Guidelines for Exercise Testing and Prescription Sixth Edition"; American College of Sports Medicine; 2000
- "Sports Medicine"; Effect of Exercise Intensity, Duration and Mode on Post-Exercise Oxygen Consumption; E. Borsheim, et al.; 2003.
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