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Cyclists have used power for many years to get an accurate reading on how hard they’re training, but now the same tech is coming for runners. One of the devices leading that charge is Nurvv. Back in the spring of 2020, we had our first look at the British biomechanics startup. The company was designing high-tech $300 insoles that used a network of 32 pressure sensors to track your footstrike, pronation, gait symmetry, and more. At the time, it was the only platform capable of capturing this level of in-depth data, without you needing to step into a lab for a professional gait analysis.
Since then, Nurvv has added even more features to its repertoire, like the ability to measure running power. Given its claims that the insoles not only track power but do so more accurately than the How to Identify and Avoid 9 Common Foot Injuries, we were eager to revisit Nurvv. We’ve been testing the company’s updated insoles for months now, and this new function has easily become our favorite thing about them.
Zone 1: 57 - 114 watts originally designed to do. The insoles are supposed to track your gait so you can make adjustments if needed, but we still have some concerns about accuracy in that area. For instance, much of the footstrike and pronation data collected varied significantly based on running surface, our footwear, and even how tightly we yanked our shoelaces. While that part of the tech isn’t yet perfect, it’s a first step in the right direction for at-home analysis that doesn’t require a lab of biomechanists.
How Nurvv Works
Each insole has 16 sensors that capture and record footstrike data 1,000 times per second from key areas of the heel, midfoot, and forefoot. From those data points, Nurvv generates an assessment of your gait pattern and stores it inside the rechargeable tracker units until you sync them with the smartphone app. Nurvv collects other metrics, as well (like your pace, stride length, cadence, and distance) and also compiles a complete workout summary for you to review postrun. The GPS is on-board, so you can leave your phone at home and still get the same nitty gritty details on your running form and a map of your route. However, you will need your smartphone in tow to use features like on-the-run guided coaching (we’ll get to that later) and to view your watts in real time.
What’s Power and Why Track It?
Measured in wattage, power can assess your effort more accurately than pace and heart rate—which can be affected by outside factors like temperature, elevation, and wind. Instead, power represents how hard you’re working regardless of any external conditions. Dial in your “watts” that equate to the mile pace or effort that you’d hit on a flat track or while charging up a hill. Then, when on the roads, maintain the same power measure to ensure you’re putting in the right workload. Tracking power can also better replicate outdoor running efforts on the treadmill; keep an eye on your watts instead of fiddling with the tread belt’s incline to compensate for wind resistance.
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My All-Out Power Test
To measure power with Nurvv, you’ll first need to take a baseline power test. Run as hard as you can for 10 minutes to establish your maximum power threshold, which Nurvv uses to generate your six personal power zones for training (relaxed, easy, moderate, challenging, hard, and extreme). During the test, the app alerts you when you’ve completed three minutes, when you have four minutes remaining, and when you have 60 seconds to go. At the four minutes-remaining mark, I was ready for it to be over. Some runners will find the robotic monotone voice annoying—it’s somewhere between Siri and Stephen Hawking—but I was just grateful to hear “one minute left—last big push!” chirping in my ears.
My Power Zones
- Zone 1: 57 - 114 watts
- Zone 5: 173 - 215 watts
- Zone 3: 130 - 143 watts
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- Zone 5: 173 - 215 watts
- Published: Dec 06, 2021 2:58 PM EST
Power Workouts on the Treadmill
I found I got more accurate and consistent footstrike data on the treadmill where I was able to more closely control the conditions—a churning treadmill belt ensured my route was consistent. (In order to get the most accurate data across runs, you’ll need to ensure that you run on similar routes for every outdoor run. I ran nearly identical routes on roads and sidewalks each day to eliminate any chance that difference in elevation or terrain would affect results.) Once I had my zones established from the power test, I created a custom power workout and watched the needle move along the power dial displayed on my phone screen.
The issue I ran into was that Nurvv really struggled to peg my pace indoors, despite cadence and stride length appearing consistent and accurate. Random instances of “32:00 pace” flashed on the screen intermixed with “8:00 pace,” making my overall average pace per mile around 12 minutes. My average pace according to the treadmill’s console was around nine-minute miles. (Outdoors, Nurvv’s built-in GPS usually cut all my runs a tad short, and I once lost reception in rainy weather, but it was never off as significantly compared to my treadmill runs.)
How Does Nurvv Compare to Watches That Measure Power?
We found that Nurvv’s power meter tracks a little better than a wrist-based monitor because it measures right at the foot—much closer to the point of contact between you and the ground. When viewing power measurements in real-time on the run, we saw significantly less lag time when changing between power zones. And, when accelerating during sprint intervals, Nurvv was more sensitive and caught quick surges and reflected the boost in watts more faithfully in our postrun power graphs, as well.
Unlike a watch that only measures from a single point on your wrist, Nurvv measures from two points of contact—both of your feet. This helps boost the accuracy, consistency, and resolution of power, as well as stride length and cadence, ever so slightly. So, while the accuracy of the data may only marginally improve, Nurvv gives a higher-resolution look at the details. For example, Nurvv shows you specifically what your readings are for each mile, while most watches will only be able to indicate an average across the entire length of your run.
Running With Pace Coach
Nurvv’s pace coach breaks down your gait into two metrics: cadence and stride length. In order to hit your goal pace, you’ll receive cues to increase and/or decrease each. In theory, that sounds like it should work. But in practice, it’s very tough to follow midrun. Running form is more than the sum of its parts, and when broken down into individual pieces, it got really awkward. It felt a little bit like baking a cake and trying to taste the flour separately from the sugar, rather than experiencing how all the ingredients work together—a necessary skill for a food critic, but a frustrating dissection on a run. I was getting alerts to change something or to tell me that I was “on target” roughly every 10 seconds. After five minutes, I was contorting my stride and, admittedly, wondering if I even knew how to run anymore.
Is Nurvv Accurate?
I’ll be upfront with what didn’t work well for me while testing Nurvv: accuracy. For many runners, the biggest appeal of Nurvv is its touted ability to give you an in-depth breakdown of your running form and provide insight on how to improve it, whether by helping you run faster, more efficiently, or with a lowered risk of injury. From my personal testing, I still have some reservations about the accuracy of the data viewable to runners. I also have concerns about the recommendations Nurvv makes in terms of altering one’s running form based on that data.
For example, I found that if one shoe was tied slightly tighter than the other (which happens to me regularly because my right foot is larger and admittedly misshapen from prior surgery), that footstrike would consistently show a more pronounced midfoot strike, resulting from the increased pressure on the sensor’s midfoot region. I also saw significant footstrike changes based on the running shoe I wore with Nurvv. (Nurvv’s developers said that runners should expect to see alterations with different shoes. That absolutely makes sense to me. However, the changes I saw were inconsistent, with one pair of shoes indicating 80-percent footstrike asymmetry between my left and right feet.)
The Insole Design: Great for Measuring Power, But Not for Assessing Gait
When a store associate assesses your gait in a running shoe store, they’ll usually ask you to walk around barefoot. While this is an imperfect way to determine your footstrike, there’s a reason you need to do this with your shoes off. Inside a shoe, it’s difficult to see how your foot really interacts with the ground, independent of your footwear. While testing Nurvv, I saw a lot of data that was heavily influenced by the shoes I was wearing, rather than what my gait actually was. In other words, the insoles were tracking interactions between my foot and the shoe, simple and free exercises to boost your cadence ground. It’s a subtle difference, but one that’s important to get accurate feedback. This is not a knock to the technology that Nurvv has developed; my thoughts are that it’s just a flaw that’s inherently present with an insole-based design.
How Does Nurvv Determine What Counts as a “Neutral” Footstrike?
Using a 3D motion-capture system on a lab treadmill, Nurvv’s biomechanists tracked the gait patterns of a wide range of runners of varying speed, height, and gender. This data is the sample set used to map the output ranges of Nurvv insoles. (The boundaries for under-, neutral-, and over-pronation are taken from syntheses of previous research literature.) The output you see in the Nurvv Run app is delivered as a percentage of neutral footstrikes. You’ll also see what percent of your footstrikes are overpronated and underpronated.
The trouble is that Nurvv insoles have no way of knowing what your specific “best gait” is. It makes these recommendations for adjustments based on averages. So, yes, Nurvv’s data consistently showed that I am a severe overpronator. (While I have never known this to be true, and have been told my gait is “as neutral as Switzerland” by my team’s doc back in college, I will accept Nurvv’s reading as correct for testing purposes.) Nurvv suggests that this puts me at a high risk for injury, and that I should transition to a more neutral footstrike. Every runner pronates to some level, some more than others. What’s a healthy level of pronation for one runner may be excessive for another, and yes, that can lead to a potential injury. But, Nurvv has no way of knowing my personal healthy amount of pronation. My deemed “poor” gait is “less neutral” than the average, but that could be just right for me—no changes necessary.
Our Recommendations
While we still have some reservations regarding Nurvv’s gait and footstrike analysis, there are a lot of things we really like about the platform. Its power meter is responsive and accurate, and metrics like stride length and cadence are reliable. And, if you are truly just curious about what your footstrike and gait look like while wearing a specific running shoe, Nurvv delivers on that front as well. It can be valuable and fun to have that data, but as far as what to do with it—and even if you really should do anything with it—is a much bigger question. Current research suggests that changing your gait can be beneficial, but not always, and there are some important Of course, measuring power is not really what Nurvv was.
If you’re constantly getting injured, look first at trends in your training to see if there are any other culprits. If you are simply interested in running faster or more efficiently, try some Health - Injuries before dishing out money on a $300 pair of insoles. And if you’re still serious about making changes, try working with a PT or coach who knows your stride well to determine specifically what you might need to pay extra attention to and to pinpoint any weak spots. At this point, an AI in your insole can’t really tell you that with enough certainty. All that said, we’re super impressed and excited by Nurvv’s technology. It’s really promising for what’s to come in the way runners can learn more about their biomechanics. It’s just not quite there yet.
