So, my Stryd footpod arrived today. After a somewhat complicated setup process (and though cumbersome to get attached, the pod does stick perfectly fine to my front end shoelaces), I went out in the increasingly hot Vegas sun and ran a couple of brief miles around the neighborhood to give the tracker some data for me to review.
This was as standard and normal a running effort as I could get myself to do, to make sure the data had no abnormalities. Sure enough, the run (though hot and a bit arduous for that reason) felt like a typical effort, so the data should be a roughly objective view of my standard issue effort.
Sure enough, footpod IQ data showed up in Garmin Connect for the run. It’s a bit complicated to get the Garmin data uploaded to Stryd for review (I had thought it would sync automatically, but apparently not), but once I did I had dashboard data to review.
Here you see a lot of data that’s not just typical mileage, times, pace, and heart rate.
(While not pictured, the log also includes a map of my run, so Garmin’s file did port that over just fine.)
Unfamiliar items on the log include:
- Power, Stryd’s hallmark accelerometer metric. An objective measure of the effort you’re putting into your runs, regardless of hills, weather, wind, etc.
- Form Power. Stryd calls this your “running in place” power. It’s basically designed to measure your form economy, the amount of power required for your base running motion. A lower number is better.
- FPR aka Form Power Ratio, of the Form Power to Total Power. Since lower form power is better and toal power should be higher, you also want this number to be low.
- GCT aka Ground Contact Time. The amount of time each step stays on the ground before pushing off.
- LSS aka Leg Spring Stiffness. A nebulous metric of your legs’ ability to absorb the impact of running and create kinetic energy with each step.
- VO aka Vertical Oscillation. This is an estimate of how far you’re rising from the ground with each step.
- Air Power aka the percentage of power required to overcome air resistance. If you’re running into the wind this will be higher than in calm conditions or with the wind at your back. Your speed matters too, e.g. if you’re running 6 mph into a 10 mph wind, you are working against 16 mph of total air resistance.
Now, let’s see what information I get from all this new data. Again, I put in a standard effort representative of my typical runs, so this should be generally useful information.
Power is entirely contextual, unlike pace where for example 9:00 a mile is 9:00 a mile no matter who’s running it. So my 225-228 W of power is relative to:
- My currently weighing 182 lbs.
- The 2357 ft altitude and shifts in that altitude throughout the run. Vegas isn’t flat.
- My cadence and stride length.
- My given effort and pace on this run, and however I was working to maintain it.
- My energy levels at the given time combined with my body’s handling of the warmer conditions, as I tried this around 11:20am and by then temperatures were already climbing into the 80’s and 90’s Fahrenheit.
It’s a different metric that requires a different mindset in training. But in any case, my power was around 225-230 W for the entire run, and did start at 240-245 for the first few minutes before settling back in the 210’s-220’s.
Until I get a few more runs under my belt, I’m not sure what that means or how much that means relative to what I’m capable of or where I want to be.
However, PodiumRunner in 2016 (when Stryd first debuted) produced a useful analysis of Patrick Smyth’s New York City Marathon effort, in which Smyth wore the footpod, from his coach. Here I got a great breakdown of what some of the Stryd data communicates, more specifically what constitutes good readings vs problematic readings.
And, as helpful as he’s been with other topics, Jonathan Savage also uses Stryd and had a helpful writeup on some of the metrics here.
(Do also note that both these writeups were from 2016 at Stryd’s relative infancy, and Stryd possibly has upgraded some of the shortcomings from its reported data.)
The key stat that jumps out from the Smyth piece is his average power of 280-350 W throughout his marathon. As an elite runner, this points to the amount of power a well trained runner of his caliber needs to be able to capably sustain for a 2+ hour effort such as his marathon.
Is it something to reach for? Everyone who discusses Stryd advises you hit the brakes on setting benchmarks for any of these metrics, that most of them are subjective to the runner and generally indicative of things like where you’re losing energy in runs, overusing effort, underusing effort, etc.
And also bear in mind this was Smyth’s marathon effort, and he can finish one in 2:10. Plus, he’s fairly lightweight, and that level of power is easier to sustain at 130 or so lbs than 170-180. He’s also a highly trained elite runner.
If you or I tried to run a 300 W effort over a four hour marathon, it’s possible we’d collapse. Maybe that power output worked for him because he’s fast enough to cover the distance in 2:10. Again, that’s not certain and will take time, research, and practice.
For me, meanwhile, my 210-240 W effort came with a heart rate spending a good chunk of time in Z3 or Z4. But again, I was running in somewhat hot conditions, far from ideal (I would ideally have run early in the morning, but having just got the pod I really wanted to test it when I did). Had it been cooler my needed heart rate would have been a good deal lower (and I might have run longer than the 2 miles I ran). I’m not yet sure if the power output is only objective relative to wind and altitude, but not to temperature.
So I’ll see in future runs how my power output varies, especially in Summerlin runs where the altitude is higher and the hills are a bit steeper.
Separately, this doesn’t surprise me as I’ve always kept low to the ground, but my vertical oscillation is a low 6.0-6.5 cm, with the PodiumRunner stated baseline being 8-14. Apparently being too low means you lack suitable power to maximize stride length (akin to how a cannonball fired at too low an angle won’t travel far).
That said, Stryd recommends the baseline can be 3-15 cm, in which case I’m well within the range. I’d imagine VOsc around 2-3 cm is akin to shuffle stepping and dragging your feet, which I certainly don’t do. But I do keep my feet low to the ground.
Still, I know I need to improve general running power. And I can afford to let each step get me at least a couple centimeters farther off the ground if that’s what it takes.
Smyth’s Form Power was around 65 W, whereas mine is around 75 W. Absent of obvious differences between us, I suspect I have clear room for improvement in my running form. Again, bear in mind that I was running in hot conditions on the spur of the moment. Though not shown on this graph, my FP was consistent from start to finish, so it wasn’t caused by a breakdown in form. There’s probably a general need for improvement, and I’ll keep an eye on changes in FP.
A Form Power Ratio of 0.33 probably isn’t good. I suspect a better value is in the 0.20-0.25 range. An improvement in critical and average power would bring the FPR down as power itself is the denominator. But that doesn’t mean form (and form power) couldn’t use improvement.
One clear item for improvement is Ground Contact Time. I see a sizable agreement that GCT should be in the 150-300 ms range, and my steps drift past the high end at the 280-300 range. My steps need to get lighter and quicker, even given my consistent 170 spm cadence is typical of my effort and an improvement over efforts in past years. A light, quickened effort may show immediate improvement everywhere else.
Leg Spring Stiffness was very consistent at 12.1-12.2 and unshown graphs indicated this didn’t deviate much at all throughout the run.
Now, whether or not I’m reading too much into this data, I’m not sure. As I get more runs with the pod and assemble more data to see trends, I’ll have a better idea where I’m going with all this. In fact, Stryd allows for the setup of training plans, and I’m not about to use those or the Zones provided until I have enough data to get a solid baseline of my critical power and abilities.