Stryd vs Stryd – Some Data Comparisons
Must Read: in-depth Stryd Review
I’ve noticed some anomalies with the new Stryd footpod over the last few weeks. Here they are and please feel free to share your results, comments or criticisms below.
Tests – What I Did
This article has the results from 3 different run types over varying speeds and mostly on flat, hard terrain on near-windless days.
Two of the tests have an Old Wind Stryd on one foot and the latest Stryd on the other foot…swapped over at the halfway point. Both were on Nike Vaporfly shoes using the exact same calibration parameters albeit the distance factor was measured on a running track on different shoes.
The third test uses both Stryds on one foot and also enables autocalibration for each device at the start of the run. Both the Stryd pods are on my weaker right side…two pods on one shoe is not the best mounting position as the pods might touch and the Vaporfly laces point in a weird direction at the best of times. Be that as it may, very similar results carry over from the first two tests to this third test.
I am not concerned with the differences in the recorded distance in the first two tests. These differences are easily explainable by changing pods from one foot to the other and by using a manual calibration factor determined a few weeks ago on an entirely different pair of shoes.
The third image shows the run where the two Stryds are autocalibrating to distance. There’s a slight overall discrepancy and again I’m not overly concerned with that for this test as I was aiming to look here at how the recorded pace changed throughout the calibration process.
At the end of the 3rd test, the calibration factor on one device was unchanged and the other had changed by 0.1 (I can’t remember which)
As we would expect, similar distance measurements equate to similar speeds. The old Stryd is coming in a tad faster but this is not significant. They are close enough for this test.
Clearly, something has changed when we look at the Vertical Oscillation calculations between the two different Stryd models. Either model is plausibly correct and, although I haven’t shown it, neither ties in with the VO from the Garmin HRM-PRO strap. IDK which is correct.
The point is that New Stryd shows a notably increased Vertical Oscillation and I wasn’t expecting that.
I’m not especially concerned about the VO metric.
However, could something have changed in the sensor management that causes the difference? Vertical movement (though perhaps not this metric per se) must be a factor in Stryd’s power calculation. Maybe the higher VO taken into account in a new algorithm. IDK
Stance Time (Ground Contact Time, GCT)
My GCT is lower with the new pod. Again, I wasn’t expecting this and the results are consistent when I switch pods on my feet and when the pods on are the same foot.
Perhaps this is linked to the change in VO from the previous section.
So now we come to the important running power metric. Stryd claims that the new power metric is more responsive than before due to more frequent data points. Fair enough. I was also under the impression that this only impacted sprinting speeds.
In these tests, I wouldn’t classify any speeds as sprinting. I think the first test was the slowest at 4:20/km or something like that.
With 20-second power smoothing, the new Stryd power is clearly higher. I’d guestimate it to often be 5% higher.
Air power is a constituent of total power.
In these tests, there was effectively no wind. Yet the new Stryd reports notable Air Power.
If you told me that the old Stryd’s air power was the extra power required to overcome the wind, I’d believe you. It’s mostly recorded as zero so that would make sense.
If you told me the new Stryd air power is the extra power required to both overcome wind AND move your body through the air then, again, I’d believe you. But the thing here is that something has changed and I wasn’t expecting that.
Maybe my original Stryd pod has a faulty air pressure sensor? I did check that the hole wasn’t clogged up and washed it. I did check that the new and old cradles were compatible with the hole position on each Stryd pod and they seemed to be identically placed.
I am aware that other early adopters of the new pod have noticed differences in air power.
I don’t quite know what to make of these results and I reached out to Stryd for comment a while back.
I could be wrong but it looks like the impact of both the movement sensor and air pressure sensor has changed between models. Furthermore, the running dynamics metrics and the power metrics are impacted by some changes.
I don’t especially care about the efficiency metrics and the speed/distance metrics look as correct as they always were. However, I don’t see why power has changed so much. If it’s because Stryd has a better way of measuring air power…great, say so. No competitor measures air power so what Stryd gives here is a bonus.
So. What I said in this link probably isn’t quite right.
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