February 7, 2025

Here’s how your Garmin smartwatch estimates your EPOC and how you can use it to improve your training.

If you ever struggle to choose how hard to push yourself in a workout or can’t tell if you’re overtraining, Garmin is here to help.

You already know compatible Garmin devices provide data on your activities. Like, a lot of data. But just knowing your stats isn’t enough. You need to know what those numbers mean to inform your training and help you reach your training goals.

Let’s focus on one in particular: excess post-exercise oxygen consumption (EPOC).

What’s the definition of EPOC?

EPOC (also called oxygen debt or the afterburn effect) measures how much work your body does to get back to normal after exercise by looking at how much extra oxygen you’re taking in. This is measured in milliliters of oxygen per kilogram of bodyweight (ml-O2/kg).

After you work out, your body continues to use a higher rate of oxygen than usual. It takes time for your body to reset. This is a good thing. Your body will build back up to normal — and then some. That’s called “supercompensation” and helps you get into better shape.

While EPOC is usually measured in a lab, your compatible Garmin smartwatch provides an estimate based on your heart rate¹ data during exercise.

How you can use EPOC

How you use EPOC depends on your training goals. Generally, the harder you train, the higher your EPOC.

Your exercise intensity contributes exponentially to EPOC, though the length of your workout also plays a role, according to a study published in the American College of Sports Medicine’s Health and Fitness Journal. The EPOC effect, according to the Cleveland Clinic, is greater after anaerobic exercise such as high-intensity interval training or sprinting.

EPOC adds up slowly during light exercise at less than 65% of maximum heart rate. High intensities can cause EPOC values to rise quickly.

For example, a 30-minute run around 50% of maximum heart rate could add up to an EPOC value of 10 ml-O2/kg. Adding another 15 minutes at 75% of maximum heart rate could raise EPOC to 40 ml-O2/kg.

A 45-minute run at 75% of maximum heart rate could result in an EPOC value of around 50 ml-O2/kg.

How Garmin uses EPOC

The Garmin estimate of your EPOC is your exercise load for an activity, which is then personalized for you as a training effect.

Your training effect builds throughout your workout, and you can see it in real time to tailor your workout by adding this as a data field to your compatible device. When you’re trying to improve, you know when to push yourself harder. And you can slow down before you push too hard.

If you’re already in good shape, you’ll need a higher EPOC to get the same training effect as someone with a lower fitness level. That means that the fitter you are, the more you need to exercise to keep seeing progress.

Additionally, your training effect could be aerobic or anaerobic; both are mapped on a 0 to 5 scale. Your aerobic training effect shows you if your workout had a maintaining or improving effect on your fitness level. Your anaerobic training effect tells you how a workout affects your ability to perform at high intensities.

Seven primary benefit labels — recovery, base, tempo, threshold, VO2 max, speed and anaerobic — tell you how your activity helped you.

Acute training load is a weighted sum of your recent EPOC values (exercise loads), which shows the cumulative recent impact of your activities on your body and informs your recovery needs. The training load focus data screen tells you how your training intensity has been distributed for about the last three weeks. For example, it could be balanced, too high or too low in a category for best fitness progress.

Plus, acute training load is an important factor in your training status, a feature that helps connect the dots between your training and your results.

Use a compatible Garmin smartwatch — or cycling computer with a heart rate monitor and power meter — to take advantage of training effect, training load and training status features to help reach your fitness goals.

_{¹See Garmin.com/ataccuracy}