Updated: August 7th, 2017
STRYD – Review

Summary or, who should get it?

When I asked Stryd who the product is for, they said “We like to say that if you are keen to put in the effort to improve and are already working become better at running–faster, more efficient, stronger, etc–Stryd is likely for you.”

I agree with that. If you want to be a better runner, are willing to use data to improve your running, and don’t mind paying the equivalent of two pairs of running shoes for it, this device might be for you. (Did that last line about price bother you a bit? Read on, it might be worth it).

Power Meter?

Stryd made a running power meter. Let’s step back a bit and go over how cool this could be. In the earliest days of running, before wearable tech, before watches, before short-shorts, runners had almost no clue how far or how long they ran. Sure, there weren’t too many runners back then anyway, but those who ran had a sloppy estimate on how much and how well they ran.

Then came the ability for any runner to measure time on their wrist. Fast forward about 70 years after the wristwatch boom in the 1930s and we had the ability to measure both time and distance on GPS watches. Although one of the first GPS running watches was pretty bulky (The Gamin Forerunner 101 in 2003), it paved the way for what’s now an almost indispensable tool for modern runners.

Something was still missing. Runners could see how long and far they ran, but they had no way to compare one run to another run unless it was on the same course. Did they actually go harder on that hilly course even though their time was slower? Companies started to add heart rate monitors to their watches to fill this gap, however, heart rates aren’t the best indicator of how hard you are actually going. I actually did a study on myself and found it’s ok, but there’s a lot of noise and your state of mind can greatly affect your pulse. The best metric to compare the output of different runs is power.

The cycling community has known this for a while. That’s why some cyclists don’t bat an eye spending $500+ on a power meter. It’s a very pure way of measuring performance. Power is usually measured in watts, and represents how much energy is being used per second. This is somewhat simple to measure on a bike since you just measure the torque and RPM on the shaft connecting the pedals. Pretty straightforward. (I know, some companies found other ways, but the basic math is RPM*Torque=Power).

Running is much harder to figure out since we’re not spinning a shaft or pumping out electricity that can be measured with a multimeter. To accurately measure power on a runner without hooking up O2 analyzers, you’ll need to get a really good model of the runner which includes the runner’s weight and weight distribution, acceleration, rate of acceleration change, rate of that rate, any extra limb movements, resistance of the air, etc. Super hard. So it’s a little crazy to hear that Stryd says they can estimate the power output of a runner for $200. If it works well, it could be a fantastic tool for serious athletes, and if the price drops a bit, it could be the next huge thing in running.

How the device works

So how does the Stryd sensor actually work? Well, it uses lots of sensors in a pod. It features devices like a sensitive accelerometer (sensor that figures out where it’s been moved), a super sensitive barometer (sensor that figures out air pressure which can be used to estimate elevation), and a sensitive gyroscope (device that tells you how you’re rotating). There’s a whole lot more going on inside that pod, but those basic sensors give the device a pretty good idea of where it is in 3D space. Now if you tell the device how much a runner weighs, and give it equations to relate movement in 3D space, runner’s age+weight+gender data to existing data, it can spit out a decent power estimate.

This is where Stryd is coming from. Build the tech, add knowledge from experts, then figure out how to sell this device and improve it. They’re not a huge company that wanted to sell a new gizmo, and they’re not here to trick you with a device that won’t fundamentally work. That’s why their first Kickstarter was a huge success, raising more than 5x their goal, and why they’re already on their second version of the device which I tested.

What’s in the box?

Stryd sensor, Stryd charger, charging cable, two clips, instructions, and that’s it. The box is pretty nice as well.

Device specifications and pairing options

It’s a cute little pod that you just snap into a clip that goes around your shoelaces. The pod resembles a cross between a guitar pic and a topographical map. After you place this pod on your shoes and pair it, you’re good to go. You don’t even need a cell phone or smartwatch. You read that correctly, this data-hungry-number-crunching pod with no ports can figure out all your power data and roughly guess distance traveled all by itself. There are a few catches: you need to eventually sync it with your phone and the estimated distance traveled is estimated without GPS.

The sensor weighs 7 grams (0.25 ounces for you US folks), so you’ll have a hard time telling if you’re wearing it or not. It charges on a similarly styled wireless charging pad that’s powered with a Micro USB cord. You just place the pod on the charger, and then realize it’s not charging. You need to make sure the pod’s flat side is against the flat side of the charger, then you need to orient the pod so it sits practically dead-center on the pod. No magnets to snap it in place, no bumps to let it settle….you gotta get it pretty close yourself. You’ll know when you finished this game of pin the tail on the donkey when the amber light starts to glow. Luckily, this device needs a charge only every dozen runs (their site says every 20 hours of use which is about right).

My guess is Stryd wants to improve this charging experience, but the cheapest and most reliable way to wirelessly charge is to cover the wireless charging elements with plastic and give the user a visual target. Magnets would actually be hard to add since the physics behind wireless charging is that electron movement down a wire makes a magnet, so adding a magnet would mess up the charger. Hopefully Stryd finds a way to make the charging pad a little more user friendly in future versions. However, I’d prefer this existing wireless charger over plugging a wire into the pod itself. That keeps the pod weight down, and keeps it watertight. You can sink it underwater at 1 meter for 30 min, which means puddles will be no problem.

What kind of data do I get, is it legit, and what do I do with that data?

The number one reason why you should get this device is to measure POWER! The power will be displayed live during your runs on either your phone or smartwatch in watts. The harder you run, the more watts, and vice-versa. The power numbers are accurate for flat level running, ok when running up or down hills (thanks to the barometer), good on the treadmill, and no good when running at an incline on the treadmill. If you want to read into the accuracy of the power estimate, check out this data from http://fellrnr.com/wiki/Stryd

Unlike most cool looking new measurement tech to the market (I’m still bugged by the Adidas Fit Smart) the Stryd sensor is legit.

Now, the fun part. If you know your power when running, you can pace yourself by effort. That’s a very powerful tool. If there’s a hill, you slow down until your power matches what you were doing on the flats. If your stride is falling apart and you start to put in more power to maintain the same pace, you catch this bonking situation and slow down. This lets you run smarter.
After you’re done with a run, you can see your power throughout the whole run and use this average power as a target for your next run. If you run enough at various intensities across various durations, you end up with something eye-opening.

I’d like to call it the power-hockey-stick. This is basically a coach in chart form. Know the rough amount of time you want to run? You now know your maximum effort at that duration. Want to go out for an easy 20 min run? Turns out that’s the same effort as a hard 90 minute run. Oh, you can also use this chart to see if there’s a critical duration that has a sudden drop in power and train to increase that to build your overall endurance.

The remaining data you get out of this device is icing on the cupcake.
Leg spring stiffness is a new term to some of you out there. The bad but quick explanation of it is that it describes how springy your legs are. The better explanation is that it describes how much force your legs push back when deflected and is measured in KN/M. You can see your leg spring stiffness (LSS) over the course of a run, and see how you compare to top runners. Stryd lets you know how to improve this number.

Another few bits of data you get is your stride rate and ground contact time. Both are recorded throughout your run.

I’m mentioning distance last since it’s indirectly calculated based off all the sensors and doesn’t give you the path traveled like GPS, but it’s more accurate than some other devices I’ve tested. I’d say it’s good to around +/-5% of your actual distance with 95% confidence (I ran these tests on a flat treadmill). Since this is figured out just on the devices with all the other data points, you can just put on your shoes with the sensor, and GO! No GPS to sync, no watch to bug you, no music to set up, just pure running with a tiny coach riding along on your foot. Once you’re done wandering around the streets of your city, you can see what you did. No buttons needed to be pressed at all! In my conversations with Stryd, they mentioned the device will detect when running started, then collect data as it senses running is happening, then stop recording after a minute or so of no activity. Pretty neat.

Oh, you probably just read over that paragraph, saw numbers, figured “Sounds accurate, maybe not as accurate as GPS though”.



Web interface and app additional notes

The web interface is great, and hosts your data in the clear to understand formats that you’ve seen earlier in this review. Stryd calls it the power center. Setting up the online account is pretty easy as well. What’s neat about the instructions for this device is that they’re 3 steps on a card. Everything else is online. .

What I disliked

I need to tell you something. I feel bad. I lost the Stryd sensor a little after a month of testing. It’s mostly my fault since I think it was forcefully pulled off when I forcefully pushed my shoe into a stationary bike pedal at the gym. Yeah, pretty stupid on my part. Since the device is wonderfully small and unobtrusive, I didn’t notice. The clips are actually very strong so I suspect 99% of you will have zero problems with it. To the 1% of you that abuse everything you get because you either got it for free (like me), or think electronics should suffer, exercise some caution when wearing your Stryd shoes in activities besides running.

My actual gripe with the device is the communication and interface with Garmin devices. This is a bit on Garmin, and a bit on Stryd. I tested the Stryd sensor with a Garmin vívoactive HR with the expectation that I could see my live power while running without a phone. Huge plus for me since I hate running with a phone. The Stryd IQ field and activity had problems on download (Garmin issues), but I figured it would work nicely after loading them on my watch.

It didn’t work well. The first thing the Stryd activity tells you to do is shake your Stryd sensor to activate and go. This was not smooth, and took me a few attempts. I got it working, but then the live power kept dropping out on my runs. I figured it was an issue with the Stryd activity, so I tried something else. I added the Stryd IQ field to one of my data screens on the IQ app. Seemed to work about the same, until the IQ field crashed and filled the watch’s data screen with a IQ crash icon. Darn.

The good part is the data on the Stryd sensor wasn’t disappearing and coming back as my watch suggested; the data was safely stored on the sensor and synced after each run. I could still use the watch to get a run summary in the Stryd activity…sort of.

Before I complain even more, you should know my full time job is in programming and testing systems, so I naturally try to mess with electronics. Also note that many other Stryd testers have had no issues with their device. What I found was the Stryd activity could be crashed if you swiped to a different screen on screens that aren’t set up for you to swipe. I also found that a long enough run after a fresh restart of the watch would sometimes hard-crash the watch. Ouch. I’m not sure if the underlying problem is in Garmin or Stryd software, but I know the issue only started to happen after I got the Stryd sensor. Be aware if you use a Garmin vívoactive! This unfortunate crash happened at the start of the Boston Marathon for me and I lost the first quarter mile of running to a watch reboot. I should mention that I never had issues when using the Stryd sensor with my Google Pixel phone.

I messaged all these issues to Stryd and they were actually pretty great at acknowledging open issues and troubleshooted with me. The great part about new stuff from small companies is that you can get something really groundbreaking. The bad part is that sometimes the product doesn’t have the full testing that a massively produced product gets before shipping. I trust that Stryd will fix any issues on their end and the device will get better.

What I loved

The Stryd team. I was in email conversations with a few Stryd people, and even had a video chat with one of them when I first got the device. They are not a big marketing team that’s hoping a flashy product with questionable internals will ride on the wave of a previous Kickstarter’s hype. They are a real dedicated team that, although started with a Kickstarter, are trying to make the next big thing in running and know how to do it.

The size of the device. Yup, I know I just said I lost it because it’s small, but Stryd managed to get everything they needed in a reasonable and attractive size. Heck, most wireless ankle number transmitters I wear in Triathlons are bulkier.

The hardware. As mentioned earlier, I work with tech, studied engineering, and live running. I usually know when a company is selling something that can’t fundamentally deliver. Stryd did their research and got the components that makes a running power meter possible. It’s also why this is a $200 device and not a $50 one. They looked at what was needed, optimized for size and cost, and wound up at $200. Some companies start with a price point, then try to make the product work, or just throw out fundamental features to get the cheaper price. You are paying a premium for the Stryd device, and it’s for the sensors+research.


If you just read everything I wrote up to this point and figured the device might make sense for you, then you should get the device. I know the cost is high, but you’re serious with your running and this is a genuine training tool. Even if you use it for a handful of runs each month, you’ll get pretty insightful data into where you are as a runner, and what you can do to improve.
Stryd managed to release a running training device that Nike, Garmin, Adidas, and all the other big players will soon want to integrate into their products. I expect running power meters will take off in the next handful of years, and we’ll either see Stryd as a leader in the space, or we’ll see one of the big players buy up Stryd.

Also, if you go to Boston Sports Club in Davis Square and found my Stryd sensor, mind handing it to the staff and tell the to contact me? Thanks 🙂

Me in the staying steady in the Boston Marathon in a Fridge costume with a Stryd sensor.

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