How to Use the COROS Efficiency Score to Optimize Your Training

In the world of endurance sports, every detail matters. Understanding how efficiently your body moves is just as important as tracking mileage or heart rate. That’s where the COROS Efficiency Score comes in—a powerful tool designed to help runners analyze how effectively they turn effort into performance.

The Efficiency Score is available for most outdoor runs on the COROS App and Training Hub

What Is the COROS Efficiency Score?

EvoLab calculates an Efficiency Score for each eligible run you perform. At its core, the Efficiency Score uses your last 42 days of running data to calculate an expected heart rate value at any given pace. If your HR is above the expected value, your efficiency is lower. If HR is lower than expected, your efficiency is higher. If your efficiency is the same as expected, the score is 100%.

Simply put, it tells you how much "return" you're getting for your effort. What helps me with this concept is efficiency means “it costs less”. If you are running at a pace that is difficult, your HR is going to be higher and will require more effort. Once you are stronger and more fit, that pace will feel comfortable and cost you less effort.

Beyond Biomechanics: How COROS Measures Efficiency Differently

Running efficiency can be measured in various ways, with running economy and biomechanics being two key factors traditionally used to assess a runner’s performance. Running economy refers to how much oxygen a runner consumes at a given pace—essentially, how efficiently the body converts oxygen into forward motion. Factors like stride length, cadence, muscle fiber composition, and even footwear can influence running economy.

Biomechanics, on the other hand, focuses on the movement patterns that contribute to efficiency, such as ground contact time, vertical oscillation, and joint angles. Many studies and wearable technologies analyze these metrics to help runners optimize their form and reduce energy waste, leading to better overall performance.

While COROS’ Efficiency Metric doesn’t measure running economy or detailed biomechanics directly, it provides a unique analysis based on effort and output. Instead of oxygen consumption or movement patterns, COROS evaluates efficiency using pace and heart rate data from previous runs. This approach allows runners to track their internal effort vs. external performance—essentially measuring how hard the body is working to maintain a given pace. While a runner with excellent biomechanics might naturally be more efficient, COROS' metric helps gauge whether fitness improvements (such as better aerobic capacity) are leading to lower heart rate at the same pace. This makes it an effective tool for tracking training progress without needing a lab test or motion analysis, providing practical insights for everyday runners.

Coaches Tip: While efficiency doesn’t measure running dynamics like cadence or stride length, improving these metrics can improve your efficiency score. Try taking our Running Form Test to see how you can improve your running dynamics.

How to Improve Your COROS Efficiency Score:

Since your Efficiency Score is based on the last 42 days of training, improving it means becoming more efficient than you have been recently. If your fitness is progressing, you’ll naturally outperform EvoLab's expectations and see higher scores, but intentional training adjustments can help target these gains.

Work on building your aerobic base with plenty of easy miles and a incorporating 1-2 higher-intensity workouts per week. Workouts like threshold intervals and tempo runs will train your body to handle higher intensities more efficiently, ultimately improving your efforts and heart rate response. These strategies helped my Efficiency Score jump from 95% to 110% on my runs after coming back from injury.

A bonus tip that worked for me - my efficiency score is always higher if I'm running a majority of my run in Zone 2, and some portions of my run in Zone 3 then a few minutes in Zone 4. These progression runs work slowly through multiple heart rate zones and give you a broader view of your efficiency.

Things to Consider With Efficiency

Weather

While the Efficiency Score is a valuable tool for tracking your progress, it’s important to know that external factors can influence your heart rate and, ultimately, your score. Environmental conditions like wind, heat, and humidity can increase your heart rate even during efforts that feel comfortable. These factors can produce Efficiency Scores below 100%, but they don’t necessarily reflect a decline in your fitness.

Illness & Stress

There are also internal factors that can affect your heart rate, aside from the exercise itself. High stress from school, work, and life can lead to a higher heart rate than expected. Illness is another culprit to increasing heart rate, and will almost always result in lower efficiency scores.

Warm-Ups

A proper warm-up helps your body transition into higher-intensity efforts more effectively and sets the tone for a productive workout. Sometimes we can start off a little stiff and unsteady before settling in. We don't want that to impact your Efficiency Score, so EvoLab excludes the first 10 minutes of your run from its calculations. This means your warm-up period allows you to ease into the run without negatively affecting your score.

A run with a low score while coming back from injury

Your Efficiency Score is a great way to analyze how each run compares to your fitness, but remember that progress takes time. Focus on smart training, manage what you can control, and use your score as a guide. If you want personalized insights into your own Efficiency Scores, reach out to coach@coros.com and our team of coaches will help analyze your training!