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Tip: This is not the original design purpose of these insoles.

For years, cyclists have been using strength to accurately understand their training intensity, but now the same technique is also applicable to runners. One of the leading devices is Nurvv. As early as the spring of 2020, we saw this British biomechanics startup for the first time. The company is designing a high-tech insole worth $300 that uses a network of 32 pressure sensors to track your footsteps, pronation, gait symmetry, etc. At that time, it was the only platform capable of capturing this kind of in-depth data, and you didn't need to enter the laboratory for professional gait analysis.

Since then, Nurvv has added more features to its functions, such as the ability to measure running power. Given its claim that insoles can not only track power, but are also more accurate than running watches currently on the market, we are eager to revisit Nurvv. For several months, we have been testing the company's updated insoles, and this new feature can easily become our favorite thing.

Of course, measuring power is not the purpose of Nurvv's original design. The insole should be able to track your gait, so you can adjust it when needed, but we still have some concerns about the accuracy of this area. For example, most of the foot impact and pronation data collected vary greatly depending on the running surface, our shoes, and even how tightly we pull the laces. Although this part of the technology is not yet perfect, it is the first step in the right direction for home analysis that does not require a biomechanics laboratory.

Each insole has 16 sensors that can capture and record foot impact data from key areas of the heel, midfoot, and forefoot 1,000 times per second. Based on these data points, Nurvv generates an assessment of your gait pattern and stores it in the rechargeable tracker unit until you synchronize them with the smartphone app. Nurvv also collects other indicators (such as your pace, stride length, stride frequency, and distance), and compiles a complete exercise summary for you to review after running. Car GPS, so you can leave your phone at home and still get the same detailed information on the running form and route map. However, you need to bring your smartphone with you to use functions such as running guidance (which we will introduce later) and check your wattage in real time.

Measured in wattage, power can be a more accurate assessment of your effort than speed and heart rate-the latter may be affected by external factors such as temperature, altitude, and wind. On the contrary, power represents how hard you work, regardless of any external conditions. Enter your "watt", which is equivalent to the speed or effort you reach in miles on a flat track or when going uphill. Then, while on the road, keep the same power measurement to make sure you put in the right amount of work. Tracking power can also better replicate outdoor running efforts on a treadmill; pay attention to your wattage instead of fiddling with the inclination of the tread band to compensate for wind resistance.

To use Nurvv to measure power, you first need to perform a baseline power test. Run as much as you can for 10 minutes to establish your maximum strength threshold. Nurvv uses it to generate your six personal strength zones for training (relaxed, relaxed, moderate, challenging, hard and extreme). During the test, the app will remind you when you finish three minutes, four minutes remaining, and 60 seconds remaining. With four minutes left, I was ready to end. Some runners will find the monotonous voice of the robot very annoying-it is somewhere between Siri and Stephen Hawking-but I am happy to hear "One minute left-the last big push!" twittering in my ears.

I find that I get more accurate and consistent footstep data on the treadmill, where I can more closely control the conditions-the treadmill belt ensures that my route is consistent. (In order to get the most accurate data in running, you need to ensure that every outdoor run is running on a similar route. I run almost the same route on roads and sidewalks every day to eliminate any possibility of altitude or terrain differences. Affect the results.) Once I established my area based on the power test, I created a custom power exercise and watched the pointer move along the power dial displayed on the phone screen.

The problem I encountered was that although the pace and stride seemed consistent and accurate, it was really difficult for Nurvv to control my pace indoors. "32:00 Pace" appears randomly on the screen, mixed with "8:00 Pace", making my overall average pace per mile approximately 12 minutes. According to the treadmill console, my average pace is about 9 minutes mile. (Outdoors, Nurvv’s built-in GPS usually shortens all my running time. I used to lose reception in rainy weather, but compared to running on my treadmill, it’s never been so obvious.)

We found that Nurvv's power meter has better tracking performance than wrist-based monitors because it measures the foot-closer to the point of contact between you and the ground. When viewing the power measurement value in real time during operation, we found that the lag time when switching between power zones was significantly reduced. Moreover, when accelerating during the sprint interval, Nurvv is more sensitive, able to capture rapid surges, and more faithfully reflects the increase in watts in our post-run power graph.

Unlike watches that only measure from one point on the wrist, Nurvv measures from two points of contact (both feet). This helps to slightly improve the accuracy, consistency and resolution of the strength, as well as the stride length and rhythm. Therefore, although the accuracy of the data may only be slightly improved, Nurvv can view details at a higher resolution. For example, Nurvv will specifically show you the readings per mile, while most watches can only indicate the average value of the entire running length.

Nurvv's pace coach breaks down your gait into two indicators: rhythm and stride length. In order to reach your target pace, you will be prompted to increase and/or decrease each pace. In theory, this sounds like it should work. But in practice, it is very difficult to follow halfway. The running form is not just the sum of its parts, it is really awkward when broken down into separate parts. It feels a bit like baking a cake and trying to taste the flour and sugar separately, instead of experiencing how all the ingredients work together-this is a must-have skill for food critics, but it is frustrating in running. About every 10 seconds, I receive an alert to change something or tell me that I "reached my goal." After five minutes, I began to twist my pace. There is no denying it, I want to know if I already know how to run.

When testing Nurvv: Accuracy, I will frankly solve problems that do not work well for me. For many runners, Nurvv’s greatest appeal lies in its touted capabilities. It can provide you with in-depth breakdowns of running styles and provide insights on how to improve it, whether by helping you run faster, It is more effective, but it also reduces the risk of injury. From my personal tests, I still have some reservations about the accuracy of the runner's visible data. I am also concerned about Nurvv's suggestion to change the form of running based on this data.

For example, I found that if one shoe is tied a little tighter than the other shoe (this often happens to me because my right foot is bigger and it did get deformed during the previous surgery), the stepping Will always show more pronounced midfoot pedaling due to increased pressure in the midfoot area of ​​the sensor. Based on the running shoes I wore in Nurvv, I also saw significant changes in footsteps. (The developers of Nurvv say that runners should expect to see changes in different shoes. This is absolutely meaningful to me. However, the changes I see are inconsistent. A pair of shoes shows that 80% of my left and right feet are asymmetrical. .)

When the clerk evaluates your gait in a running shoe store, they will usually ask you to walk barefoot. Although this is an imperfect way to determine your steps, there is a reason why you need to do this with your shoes off. Inside the shoe, it is difficult to understand how your feet really interact with the ground independently of your shoes. When testing Nurvv, I saw that a lot of data is greatly influenced by the shoes I wear, not my gait. In other words, the insole tracks the interaction between my feet and shoes, not the interaction between my feet and the ground. This is a subtle difference, but it is important to get accurate feedback. This is not a knock on the technology developed by Nurvv; my thinking is that this is just an inherent flaw in the design based on the insole.

Using a 3D motion capture system on a laboratory treadmill, Nurvv's biomechanics tracked the gait patterns of runners of various speeds, heights, and genders. This data is a sample set used to map the output range of Nurvv insoles. (The limits of under-pronation, neutrality, and over-pronation are taken from a synthesis of previous research literature.) The output you see in the Nurvv Run application is provided as a percentage of neutral footsteps. You will also see the percentage of your foot that is over-pronation and under-pronation.

The trouble is, Nurvv insoles cannot know what your specific "best gait" is. It makes these adjustment recommendations based on average values. So, yes, Nurvv's data has always shown that I am a severely hyperintroverted person. (Although I never knew this was true, and the doctor on my team told me that my gait was "as neutral as Switzerland" when I was in college, I would accept Nurvv's reading as the test purpose to be correct.) Nurvv suggested this I have a high risk of injury and I should transition to a more neutral footstep. Every runner will pronation to a certain extent, some more than others. The level of healthy internal rotation of one runner may be excessive for another runner, and yes, this can lead to potential injury. However, Nurvv has no way of knowing my personal healthy internal rotation. I think the "bad" gait is "less neutral" than the average gait, but it might be just right for me-no need to change.

Although we still have some reservations about Nurvv's gait and footstep analysis, we really like many aspects of the platform. Its power meter is sensitive and accurate, and its stride length and cadence are reliable. And, if you really just want to know what your footsteps and gait look like when wearing certain running shoes, Nurvv can also help in this regard. Having this data can be valuable and interesting, but how to deal with it—even if you really should do anything with it—is a bigger problem. Current research suggests that changing gait may be beneficial, but it is not always the case. Before making adjustments, you should ask yourself some important questions.

If you get injured frequently, first check your training trends to see if there are other culprits. If you are just interested in running faster or more efficiently, try some simple and free exercises to improve your rhythm, and then spend money to buy $300 insoles. If you are still serious about making changes, try to work with a PT or coach who knows your pace very well to identify specific things you may need to pay special attention to and identify any weaknesses. At this point, the AI ​​in your insole can't really tell you with certainty. Nevertheless, Nurvv's technology left us deep impression and excitement. This is really promising for the way that runners can learn more about their biomechanics. It's just not in place yet.