Your metabolism is the sum of all energy being used in your body. At rest, you burn approximately 1 calorie per kilogram of body weight each hour to satisfy your metabolic needs. During exercise, you burn more because your muscles need energy to contract. Once you stop exercising, you also burn more to recover from what you have done. The number of calories your metabolism burns after exercise can be estimated by measuring how much oxygen you take in compared to what you would normally require at rest. For every liter of oxygen you consume, you burn approximately 5 calories.
EPOC
On average, a person consumes 3.5 mL of oxygen per kg of body mass each minute at rest. Oxygen consumed above this amount after exercise is called excess post-exercise oxygen consumption, commonly abbreviated EPOC. A rapid component of EPOC is present for approximately one hour, while a prolonged component decays monoexponentially with a half time in the order of several hours. This means that the prolonged component can still be present 12 hours after you complete your workout, according to research published in 2003 in the journal "Sports Medicine."
Causes
Processes responsible for rapid EPOC include replenishment of blood and muscle oxygen stores and resynthesis of adenosine triphosphate and creatine phosphate, compounds your body uses to transfer energy. The rapid component is also caused by lactate removal and increases in body temperature, circulation and ventilation. Processes responsible for prolonged EPOC are less well understood. A likely contributor is the energy cost of returning unused fatty acids that had been circulated during exercise to their storage form.
Endurance Exercise
EPOC will be greater after longer, harder bouts of endurance exercise. For example, after 30 minutes of running at a challenging speed on a treadmill, EPOC over a nine-hour period averaged 7 L in eight male middle-distance runners, researchers reported in the "Journal of Applied Physiology" in 1997. This equates to an additional 35 calories burned. Interval training composed of 20 repetitions of high-intensity 60-second sprints separated by two minutes of rest resulted in a nine-hour EPOC of 15 L, which means that 75 additional calories were burned. Gender and training status also affect the amount of oxygen you consume after your workout.
Resistance Training
Your resting metabolic rate can be elevated for up to 48 hours after you train with weights. Studies assessing EPOC after resistance training indicate that its magnitude is influenced by the intensity of the exercise. For example, EPOC was greater from 0 to 20, 45 to 60 and 105 to 120 minutes post-exercise after high-intensity lifting compared to low-intensity lifting.
References
- "Sports Medicine"; Effect of Exercise Intensity, Duration and Mode on Post-Exercise Oxygen Consumption; E. Borsheim and R. Bahr; 2003
- "Journal of Applied Physiology"; Comparison of Energy Expenditure Elevations after Submaximal and Supramaximal Running; J. Laforgia, et al.; 1997
- "Medicine and Science in Sports and Exercise"; Effects of Resistance Exercise Bouts of Different Intensities but Equal Work on EPOC; M. Thornton and J. Potteiger; 2002
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