Polar Vantage V Power vs RunScribe Plus vs STRYD vs Garmin Running Power

This is one of those ‘YAY days’. I tried something a bit techy & convoluted and it all worked out.

What I tried to do

It was my first run for a while to check out my Achilles (mostly OK, thank you for asking). Also with RunScribe Plus now going LIVE with their “Sensor Fusion” pace algorithm it seemed a sensible time to properly upgrade that AND to the assume that the RunScribe running power data field would be as accurate as it could be for now. My Forerunner 235 was already set up for power from RunScribe Plus so …why not use that?

Then why not compare that to the Polar Vantage V’s own version of running power?

And you can guess the rest: Garmin Running Power came from the Forerunner 935 and STRYD was conveniently recorded onto the Polar Vantage M.

What I did

I was a running with a friend and a bit rushed. I pressed ‘Go’ four times and hoped for the best without testing any of them were paired properly and working (they are usually not paired with the right device and usually don’t work)

It was an easy 50 minute run with a couple of notably increased efforts of about a minute, just so that the numbers varied from steady state.

I then combined the numbers in SportTracks (please don’t ask how as it is complicated) and then I eventually got this

click to enlarge

They seemed to trend broadly similarly. Kinda.

Here is a second run of a similar type. There were two stops and one tunnel. I tried to keep a steady easy pace. The Polar Vantage V power data dropped to zero in the long tunnel which is highlighted at 26:00 (I was at one point looking at the watch and holding the arm it was on still).


And here is yet another easy run. I woudl say it was a pretty constant effort with only mild gradients. RunScribe and STRYD reflect possibly the constant effort I felt in executing this. What has changed on this one compared to the previous two is that I fiddled with the RunScribe on-lace position and I also calibrated the RunScribe distance in the online dashboard to correct what I think was a falsely reported asymettry. It’s still not quite right but before it was probably overestimating distance and, perhaps, also power as a result. Having said that there is still not much diference now between RS and STRYD, below.


What to conclude

This post is really a cry for help. What do you guys/girls actually want me to do with ‘user testing‘ this running power data? It clearly is not easily comparable across the 4 technologies.It probably NEVER will be.  Sure I could smooth the curves further and look at comparing averages over 1km intervals with scaling factors.

But that just seems like it will be a waste of time as no-one will truly believe the raw data.The recommnedation will always be ‘don’t change or mix running power technologies’…at least for the foreseeable future.

I don’t have a running lab in my back garden either. Although I do have a very nice park and running track.

Please also bear in mind that I have a life and a real job and not THAT many of you have taken up the option to be a supporter to this blog so I really, really need to do that other job 😉

I went through a similar critical look at Garmin’s Running Power when it first came out and those posts are referenced through this link if you are interested: https://the5krunner.com/tag/RunPow/

RunScribe Plus Review – Footpod & Running Power Meter


ESSENTIAL READING: STRYD Review – In Detail, Every Aspect

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Matthew LongbottomM DJeffMarkus GStefan Recent comment authors
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To me, the most important thing to find out is precision of the data, so which device will give me the same result for the same work. I don’t believe raw numbers across devices will ever be comparable, just as they won’t be comparable between people. But if a device is able to give me the same number for the same work, then I can compare the numbers between and across my own workouts.

Markus G
Markus G

I can only second that. It’s just a number. Using “Watt” as it’s name is understandable from a marketing point. But it makes those numbers debatable for scientists. Although being a scientist myself I don’t see it like that because for me as a runner that raw number (when reproducible for the same effort) is just what I need.

Therefore I found that chart quite interesting. It shows me that both units deriving their data from GPS showed the same “bouncing” (e.g. around 35min) while the pod-based solutions were not attracted by that.

BTW: You might check the ConnectIQ datafield “Running Power Estimator II” which I recently tested. The same basic idea was already available for the Suunto Ambit 2 (back in those days when Suunto supported something like that 🙁 ). For me it’s just the same as what Polar is now marketing as being the first who ever did that. Just mentioning…


Based on my own experience with Stryd, I’m very skeptical that these can do more than provide an estimate of instant, grade-adjusted pace. I’ve shared the same pod with other runners (leaving the same personal stats), and I’ve found that “watts” corresponds to pace, despite significant differences in stride and technique.

Markus G
Markus G

Yes, when you look at how that ConnectIQ datafield is implemented, it’s basically just that: “grade-adjusted pace” converted to a “power” number. Quite clear because it has no other inputs than pace and the self-calculated gradient.
When I tested it, that datafield showed a quite good constant relation to my Stryd values on flat and on inclines. The factor of the relation went completely off when running downhill (it became too low)
In that situation Stryd was also telling me that my form-power got worse. E.g. I probably spent some additional energy in “braking” or whatever 🙂
A solution that only relies on GPS/barometer (IMHO that is what Polar told us they are doing) has no chance to detect that. It would take some additional hardware to make use of other metrics, too.
Or it just adds in some magic “common” constants like “most runners brake on downhills”. But that’s not very individual, isn’t it.


Stryd does not detect incline. So flat and incline give the same power reading.


For my part i think the graph show alot of what i need. Comparison between different technologies – I don’t really see the need, for my part i prefer to use on (Polar) and stick to it imstead of having dozens of watches, pods HRmonitors etc. I did that with Footpods early this year, after having tored on slow response on pace shifts by GPS on my M430, I been using Polar stride sensort and all worked fine. For some stupid reason I thought RunScribe Pro would be better, but it never got instant pace as I had hoped, seems all effort went into the Plus. Then I switched to milestone Pod but the calibration always seemed to drift so now I am back to poars stride sensor again, despite not having running metrics and being BIG, i still prefer that one and spent money on pods that are now sleeping in a box… I do see that It might be insteresting to dig out the RS now and then to use to see how my stride have changed, but that was not my originally intended purpose. back o track with running power, it seems to me that all 4… Read more »