I Used a Garmin Heart Rate Monitor to Measure My “running Efficiency” and Here’s What I Found Out.
If you’re considering the Garmin Forerunner 970 , you might be drawn to its two impressive features: running economy and gait reduction. But there’s a catch: you can’t access either of these metrics without purchasing a compatible Garmin accessory, such as the HRM-600 heart rate monitor , which will set you back $170.
Is this extra training data worth the extra investment? To find out, I used it on runs over the past few weeks, including a half marathon in early May. Here’s what I learned about myself, and what you need to know before buying the accessory to get the most out of your training data.
What is running economy and how does Garmin calculate it?
Technically, running economy refers to how much oxygen you consume at a given speed. But when runners talk about it, we’re talking about the basic principle: the more efficiently you run, the less energy you’ll expend running at the same speed. Garmin translates this into a practical metric by analyzing your heart rate, speed, and running dynamics. The key parameter in their calculation (which requires a heart rate monitor) is what’s called “gait loss.”
Garmin says you need data from at least 5-7 runs to see your results. You can then find your running economy score in the Garmin Connect app by tapping “More” (bottom right) > “Performance Stats” > “Running Economy.”
What is “gait loss” and how does Garmin calculate it?
Simply put, “striding speed loss” (SSL) is a measure of deceleration. Garmin defines it as the difference between your forward momentum at first foot contact and your minimum forward momentum during the stance phase of that stride. Imagine the short period of time when your foot is planted on the ground and your body passes over it. This is measured on your chest with a heart rate monitor and expressed in centimeters per second. You want this value to be as low as possible.
To understand why SSL (Single Stroke Expected Strokes) is important, it’s helpful to imagine what physically happens with each step. A high SSL means your body somehow “brake[s]” as your foot strikes the ground, requiring you to exert much more effort to return to your starting position. A low SSL means your foot spends less time dragging on the ground, and your stride is more like a smooth, continuous wheel (rather than a vicious cycle of “brake-accelerate-brake-accelerate”).
Several factors can increase your straight-line running speed: a slow cadence, a stride that’s too wide (foot landing too far in front of the hip), or any other factor that creates a hard, sharp contact with the ground. You can try to decrease your straight-line running speed by running with a lighter, shorter stride, landing with your foot directly under your body (rather than extending it forward or dragging it back).
While researching all this, I discovered one thing: some gait metrics, such as stride frequency and ground contact time, improve naturally with increasing running speed, as speed itself contributes to improved technique. It’s a bit of a “chicken or the egg” situation, but for proper running technique and speed.
What Garmin Running Dynamics Taught Me
I’ll spare you my usual face-saving disclaimer about being a very average runner—almost always in the 50th percentile of every race I enter. Let’s look at the numbers. In these graphs, each dot represents a percentile range compared to other runners. Purple is at the top (95th percentile and above), blue covers 70-95%, green is the middle range (30-69%), orange is 5-29%, and red is the bottom fifth percentile. Garmin claims that green, blue, or purple zones are typical for more experienced runners, which is certainly true for me.
If graphs aren’t your thing, here are the run stats as they appear in my Garmin Connect app.
On average, I lost 8.2 cm/s² of velocity per stride during the race, which corresponds to an average velocity loss per stride of 2.85% . This means that with each stride, I lost approximately 2.85% of my forward momentum upon contact with the ground.
A positive for me was the lack of a noticeable climb in the second half of the race, exactly where I’d expect my form to decline due to fatigue. I looked at the green peaks around the 0:49-1:15 mark, and it turned out they corresponded to a descent. It’s logical to assume I was subconsciously slowing down, rather than tensing my thigh muscles and racing down those slopes.
Other metrics that catch my attention are cadence and vertical ratio. My cadence averaged 181 steps per minute, which is encouraging, as 180 steps per minute is by far the most common “optimal cadence” known to all runners. Unfortunately, vertical ratio isn’t as appealing: vertical ratio also measures running efficiency, but by dividing the vertical amplitude of your oscillation by your stride length. At 8.5%, I’m below average in this metric. Instead of delving into that now, let’s move on to another efficiency metric I’m interested in today: running economy.
How useful is Garmin’s running economy metric?
The “Running Economy” screen (data from my run on Saturday, May 16th) shows a score of 214 , placing me in the “Trained” category. According to Garmin, my running economy is good, but there’s room for improvement, and significant improvement will likely require a gradual increase in training intensity and volume. Progress at this level may be slower, the system tells me, but it’s achievable.
For now, I’ll take this at face value. As I mentioned earlier, there are measurable ways to improve this metric , but a lot depends on genetics. This metric gives me something concrete to track. If the score approaches the green, blue, or purple zone in the coming months, that will be a sign that my training is leading to measurable efficiency gains. If it remains the same while my training volume and intensity increase, that’s worth investigating. Running economy metrics are only as meaningful as the underlying data, so I plan to log more runs with the HRM-600 heart rate monitor to get a more complete picture.
Do you really need the HRM-600 heart rate monitor?
For me personally, running economy is an interesting metric, especially given my new understanding of how SSL works. Beyond analyzing individual runs, I believe there’s real benefit in simply wearing the HRM-600 consistently and tracking my personal SSL range over time.
I think most SSL runners shouldn’t obsess over this metric. Percentile comparisons can be interesting, but there comes a point when it’s best to put them aside. What’s more important is whether your SSL is moving in a useful direction.
Whether the HRM-600 is worth $170 depends on how deeply you want to dive into it. Even without getting hung up on the numbers, the SSL is a useful tool for me to check my running form. When I encounter problems during a run, it’s a helpful nudge to mentally analyze the situation: am I stride too wide? Do my feet land in front of my hips rather than under them? What’s my running cadence? Here are a few tips I constantly return to: shorten your stride, let your feet land under your body, and think of a “light and quick” stride rather than a “push and jerk.”
If you’re a data-driven runner already getting the most out of your Forerunner 970 and are looking for new ways to gain insights, the next step is to learn about running economy and how much speed you lose with each stride. If you’re still working on the basics, you’ll get more benefit simply by running more regularly. Save that money for race registration fees.