What would you say if I told you that you could burn a lot more calories than you currently are, and without having to increase your time spent exercising? What if I told you there is a way to turn your body into a metabolic furnace, capable of boiling away extra calories while you‘re working at your desk? What if I told you I could do all that for you and cut your time spent exercising? Would you be interested? Then read on to learn how EPOC can lead to epic fat loss.
First off, no, EPOC is not a new app that allows you to put everything from your pocket onto your phone—good guess. EPOC, or excess post-exercise oxygen consumption, is the term we use in exercise physiology to describe the extra oxygen, above resting levels, that is consumed after a physical activity has ceased. Popular culture refers to this term as the exercise “afterburn.” It is well understood in science that for every liter of oxygen you consume, you burn approximately five calories. Therefore, if we measure the oxygen you consume after exercise and subtract the resting level consumption, we can calculate the EPOC and estimate the calories that you burn long after exercise has ended. This provides us with a tool we can use to examine the “afterburn” differences between various modes, lengths, and intensities of exercise.
Why should you care about EPOC?
Think about this parallel: Money is useful, and acquiring money passively through interest, dividends, and growth is even better, because you aren’t trading your time for its acquisition. Burning calories is useful if your goal is to lose fat. Burning extra calories passively even when you’re not exercising is even better, because you aren’t trading your time for the increased burn. This is the basic idea behind much of fitness these days. Many products and services claim to help you burn fat passively so you aren’t trading so much time for the payoff of fat loss. Learning the details behind some of these theories can help you distinguish reality from fantasy.
What influences EPOC?
There are three primary factors that influence increased oxygen consumption after a physical activity has ended: duration, intensity, and intermittent patterning.
First, as duration increases, EPOC increases. The longer one engages in an activity at a given work load, the larger the caloric burn will be after exercise has ended. Studies have shown an increase from 33 calories to 165 calories in afterburn consumption when subjects exercised at 70 percent of their max VO2 for 30 and 60 minutes, respectively. Thus, go longer and have a larger afterburn.
Second, as intensity increases, EPOC increases. For two exercise sessions that are equivalent in caloric expenditure, the more intense session (even if shorter in duration but resulting in a similar overall workload) will result in the larger EPOC. If we each run for an equivalent distance, but you run much faster than I do, you will have a larger afterburn. For example, if two 70-kg men run a mile, one in 4.5 minutes and the other in 8.5 minutes, they’ll both consume roughly the same number of calories. However, the faster runner will have a larger EPOC and will consume more calories overall.
Third, breaking one longer duration exercise session into two or more smaller sessions, or alternating intensities within an exercise session, can increase the EPOC. For example, rather than running at 70 percent of VO2 for 30 minutes, perform three 10-minute runs at 70 percent. The accumulated EPOC would be higher in the latter broken-apart run. Another example would be alternating 30 seconds of sprint exercise with 3 minutes of lower-intensity jogging at 60 percent of your VO2 max for a total of 30 minutes. The intensity of the intervals will increase the EPOC when compared to a steady-state run of 30 minutes at 60 percent of VO2 max.
Does EPOC really matter for me?
Absolutely. It is easiest to think about EPOC as a post hoc measure of exercise intensity. If you worked harder or longer it is going to take your body more time to recover from the exercise session. During this time, your body is burning additional calories as it attempts to return to homeostasis. These extra calories can be quite useful if your goal is weight loss. If you burn off an extra 120 calories after every workout by being a little more intense, these afterburn calories will add up. If you do 100 workouts a year this would add up to an extra 3.4 pounds per year lost on the scale, all because of afterburn.
And in addition to the increased caloric expenditure after exercise has ended, research is continuing to show high-intensity interval training (HIIT) and sprint-interval training (SIT)—the kinds of training strategies that raise EPOC—are also effective strategies for lowering blood sugar and reducing intramyocellular fat deposits. Burning more calories and having a larger impact on meaningful blood measures of health, all in less time, are powerful arguments for considering these strategies. Remember, you only have so much time to exercise, so you want to use that time wisely.
How do I apply these principles to my own training?
I have three strategies incorporating the principles of EPOC that I like to try to push on my clients (always check with your physician before beginning a new exercise program):
Be sure to incorporate at least two days of intense interval training into your workouts each week. Start by alternating 3-4 minutes of lower-intensity cardiovascular exercise (say 50-70 percent of heart rate max) and 30-60 seconds of 90-105 percent of HR max for 20-30 minutes. Be sure your sprint intervals are truly maximal exertion. Slowly increase both the amount of time spent at the higher-intensity intervals, the number of intervals, and the overall length of time of the training session. Eventually your workouts should look like those of elite sprinters: short, highly intense efforts interspersed with brief recovery periods for the entire body of the workout.
One day per month, engage in an extended-duration exercise session. This might be a two hour spin class. It might be doubling your normal distance on your running route. It might mean performing two small group workouts back-to-back. Whatever you do for exercise, multiply it by a factor of two or three at least one time per month. These extended-duration exercise sessions, even if at lower intensity, are great ways to shock the system and elicit a huge EPOC.
If possible, take three ten-minute walks per day during your work day. The amount of time spent sitting is now known to be an independent risk factor for our health. The more time you sit, the sicker you get. But breaking up your day by throwing in three ten-minute walks at 10 a.m., noon, and 3 p.m. is a great way to increase your daily step count and influence EPOC in a positive way. (No time to walk for ten minutes? Honestly, I don’t understand this. People waste more time opening garbage email and joking back and forth with irrelevant weekend details than they could ever possibly waste on a few ten-minute walks each day. If you don’t have time, you are simply wasting time somewhere else.)
Will EPOC lead to epic fat loss? No. A good exercise plan carried out over a long enough period of time is the only way to produce epic fat loss. However, the underlying principles that affect EPOC can help you consume more calories in less time and perhaps even benefit your health in other ways. I strongly suggest considering some of these strategies in your training program to improve results and enhance your health.