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If you are looking Garmin Forerunner 970You may be attracted to its two buzz-worthy features: running economy and step speed loss. But there’s a catch: you can’t access any of the metrics without buying a compatible Garmin accessory ie HRM-600 Heart Rate MonitorThat will run you $170.
Is this extra training insight worth the extra investment? To find out, I’ve worn one on my runs for the past several weeks, including a half-marathon race in early May. Here’s what I learned about mine and what you need to know before buying an accessory to get the most out of your running data.
What is “running economy” and how does Garmin calculate it?
running economy Technically it refers to how much oxygen you consume at a given pace. But when runners talk about it, we’re referring to a basic principle that says the more efficient you are, the less energy you burn to run faster. Garmin translates this into a practical score by analyzing your heart rate, speed and running dynamics. A key input to their calculation (which requires a heart rate monitor) is called “step speed loss.”
To give you a score, Garmin says it needs data from at least 5-7 runs. After that, you can find your running economy score in Garmin Connect app By tapping More (bottom right) > Performance Statistics > Running Economy.
What is “step speed loss” and how does Garmin calculate it?
Simply put, “step speed loss” (SSL) is a measure of braking. Garmin defines it As the difference between your forward motion when your foot first contacts the ground and your Minimum Forward motion during the stance phase of that step. Picture a short window when your foot is planted and your body is passing over it. It is measured on the chest by a heart rate monitor, and is expressed in centimeters per second. You want that number to be as low as possible.
To understand why SSL is important, it helps to think about what is physically happening with each step. A high SSL means that your body is somehow braking when your foot hits the ground, and you have to do a lot more work to get back to where you were. A lower SSL means your foot is spending less time dragging against the ground and your stride is closer to a smooth, continuous wheel (rather than brake-accelerate-brake-accelerate on a loop).
A few things can lead you to SSL: low speed, overstriding (landing with your feet too far in front of your hips), or anything that makes heavy, stomping contact. You can try to lower your SSL by running with a light, short stride, landing your leg right under the body (rather than reaching forward or pulling back).
One thing I discovered while digging into all of this: some gait metrics, like cadence and ground contact time, seem to improve on their own when you run faster, because speed itself encourages better mechanics. It’s like a “chicken before the egg” scenario, but for proper running form and speed.
What Garmin’s Running Dynamics Taught Me
I’ll spare you all my usual face-saving disclaimers about how I’m an extremely average runner – in fact, almost always in the 50th percentile in every race I run. Let’s take a look at the numbers. In this graph, each dot represents a percentile band compared to other runners. Purple sits at the top (95th percentile and above), blue covers 70-95%, green is the middle range at 30-69%, orange comes in at 5-29%, and red represents the bottom fifth percentile. Garmin says green, blue or purple zones are typical for more experienced runners, which tracks for me.
Decreased average step speed for my half-marathon race.
Credit: Meredith Dietz
Average step speed loss percent for my half-marathon race.
Credit: Meredith Dietz
If graphs aren’t your thing, here are the run stats listed in my Garmin Connect app.
Credit: Meredith Dietz
My average step speed for the race was loss 8.2 cm/sAverage SSL translates to percentage 2.85%. That means that at any given step, I was losing about 2.85% of my forward momentum during ground contact.
The one bright spot for me is that there is no obvious upward spiral in the second half of the race, where I would expect my form to collapse due to fatigue. I checked the green spikes around the 0:49-1:15 mark, and it turns out they correspond to the downhill portion of the race. It made sense that I was subconsciously breaking my stride instead of firing up my quads and charging down those hills.
What do you think so far?
My SSL shot up when the elevation shot down.
Credit: Meredith Dietz
Other numbers that catch my eye are cadence and vertical ratio. My cadence averages 181 steps per minute, which tickles me, since 180 spm is by far the most common “optimal running cadence” that all runners know. Unfortunately, my vertical ratio isn’t as pretty a picture: the vertical ratio also measures running efficiency, but by dividing the vertical oscillation by the stride length. At 8.5%, I’m below average in this metric. Instead of digging into that right now, let’s turn to the second measure of efficiency I’m concerned with today: running economy.
How useful is Garmin’s Running Economy Score?
Credit: Meredith Dietz
The Running Economy screen shows the score (race date on Saturday, May 16). 214Puts me in the “trained” category. Garmin’s own description of the score is that my running economy is at a good level with room for improvement, and that meaningful gains will require gradual increases in both intensity and volume. Progress at this level may come more slowly, he tells me, but it is achievable.
For now, I’ll take it at face value. As I’ve covered before, There are tangible ways to improve this metricBut a lot of it comes down to genetics. What this number does is give me something concrete to track. If the score moves into green, blue, or purple territory over the coming months, that’s a sign that my training is translating into measurable performance gains. If it stabilizes while increasing volume and intensity, it’s worth investigating. The running economy score is only as meaningful as the underlying data, so I plan to log more runs with the HRM-600 to build a better picture.
Do you really need the HRM-600?
Personally, the running economy score is an interesting metric, especially with my new understanding of how SSL works. Beyond single-race snapshots, I think there’s real value in just wearing the HRM-600 consistently and tracking my personal SSL range over time.
For most runners, I don’t think SSL is worth considering. Percentile comparisons can be fun, but there comes a point where it’s better to tune them out. What is more important? Yours SSL is trending in a useful direction.
Whether or not it’s worth paying $170 for the HRM-600 depends on how deep you want to go. Regardless of the number, SSL is a helpful form-check tool for me. When it creeps up while running, it’s a useful nudge to do a mental audit to figure out what’s going on: Am I over-striding? Is my leg coming forward instead of under my hips? How’s my cadence going? A few pointers I come back to: shorten the stride, let the legs go under the body, and think “light and fast” instead of “push and drive.”
If you’re a data-oriented runner who’s already squeezing value out of your Forerunner 970 and looking for the next level of insight, running economy and step speed loss are natural next steps. If you’re still working on nailing the basics, you’ll pay off more with more consistent running. Save that money for race registration fees instead.
