Stryd vs Runn 15% difference on treadmill

If you email support at stryd dot com they can help take a look at the data and your setup!

I use both Stryd and RUNN.

Stryd is the most accurate by a long shot. More accurate than GPS when you are running outside. Use this if you have it!

RUNN is a great alternative but you will be off by 10-15% occasionally. You can calibrate RUNN but I am not sure how much this helps.

ZWIFT run pods suck. A total waste of money.

Try measuring your heart rate with a non-watch HRM (chest strap or precision optical arm band).

I've found that once I had my Stryd calibrated to a track, that my HR to pace tracks very closely between subsequent treadmill and outdoor runs provided I'm using Stryd to measure distance/pace in all scenarios.

Since the Stryd was calibrated to a track (which I believe is safe to use as a gold standard), then it's safe to say that is correct on the treadmill as well, especially if the heart rate measurements are the same between treadmill and outdoor runs.

I've run on multiple treadmills that were also reporting FAR off from what my Stryd was reporting but in all of those cases, my heart rate data and perceived effort were consistent to the pace coming off the Stryd and not the treadmill display.

wazzu1452 wrote:

I use both Stryd and RUNN.

Stryd is the most accurate by a long shot. More accurate than GPS when you are running outside. Use this if you have it!

RUNN is a great alternative but you will be off by 10-15% occasionally. You can calibrate RUNN but I am not sure how much this helps.

I have both Stryd (the wind version) and Runn, and have found the opposite to be the case. I've tested my treadmill by measuring the belt and then counting rotations for a set period of time at various speeds. My treadmill is very accurate. And the Runn Sensor matches the treadmill pace exactly.

In contrast, even after calibrating the Stryd on a track it can be off (both on the treadmill and the road, as well as when I return to the track). More importantly, it is not consistently off. It will be fine for 8 or 9 runs out of 10 and then then it starts reading very off - up to 20 seconds fast or slow per mile. And even within the run it will not be consistent. I could be running a consistent pace on the treadmill (as assessed by the speed on the treadmill, my perceived effort, and my heart rate) and my mile splits as reported by Stryd will vary notably both up and down.

Perhaps I got a bad Stryd - I don't know. I spent about 6 months using it instead of GPS, and I've gone back to GPS for outside and the Runn Sensor on the treadmill.

Crazy. I calibrated my Stryd by taking it down to the gym and running on a new treadmill. It's spot on every other treadmill I use.

The RUNN I am still tinkering with. There are less ways to calibrate it it seems.

My uses it for virtual runs on ZWIFT.

darkwave - The problem with that experiment is runner load on the belt, how the treadmill's controller handles different speeds and the machine heating up.

For example, on my machine, if I wear the Stryd while walking it will be absolutely dead nuts on. I mean almost exactly the same distance read over time with no variation. However when I start running, the machine and the motor windings start heating up and the distance and speed start to drift slightly from the target. I really doubt that many treadmill manufacturers invested a lot of extra cost just to dial in the accuracy of the display to the belt speed over the range of speeds with any person loading it at their various cadences and ground contact times. It's just not that "tight".

On my particular machine (NordicTrack Commercial 1750), at 9 minute pace it will drift slowly by up to about 10 to 15 seconds per mile off from the Stryd measurement. It takes about 65 to 70 minutes to get all the way to max error where it stabilizes and stops drifting. My heart rate follows it and also stops drifting once the pace reading on the Stryd also stops. It's not just the pace but it's also the Power reading. It all matches.

It's slightly worse at 8 minute pace (about 20 seconds per mile off) and again at 7 minute pace (about 30 seconds per mile off). I assume this is from greater heating. The same is true at high speeds for intervals (over 30 seconds per mile off). One could probably plot the %error vs speeds over time. Again, these are loaded conditions with me running on it with my weight and ground contact time. And at low speeds where the machine remains cool, there is no drift at all. And the speeds are spot on right at the start of the workout.

My point is that there are a TON of variables affecting the actual belt speed over time. In my experience the Stryd pace and power feedback track with my heart rate. I believe a great test to check that accuracy is to either wear a heart rate monitor and compare to outdoor conditions OR repeat your test but do it with a runner on it over a variety of steady speeds over time curves. At appears to me that the Stryd is consistent and accurate. It could be that my pod is good and yours is bad though (as you mentioned)

The NPE Runn is very consistent if you have enough marks on the belt. The Stryd is super consistent on the road but not necessarily accurate. On the treadmill the Stryd is crazy wrong and is unable.

Many people on the their forum report this is. I have a manual curved treadmill so the difference is more pronounced

its only 5k wrote:

The NPE Runn is very consistent if you have enough marks on the belt. The Stryd is super consistent on the road but not necessarily accurate. On the treadmill the Stryd is crazy wrong and is unable.

Many people on the their forum report this is. I have a manual curved treadmill so the difference is more pronounced

I'm sure the NPE Runn is accurate but to say the Stryd is inaccurate based on the forum responses isn't a very scientific method of coming to that conclusion. I've read those forums and nearly everyone there claims the Stryd accuracy sucks because it doesn't match the treadmill.

No one stating that seems to consider the fact that the treadmill speed may vary over the course of the workout.

BHViking wrote:

darkwave - The problem with that experiment is runner load on the belt, how the treadmill's controller handles different speeds and the machine heating up.

Fair enough. But...a few points:

1) I'm less than 110 pounds, using a treadmill that says it can handle someone weighing 375 pounds, with a 4CHP motors. My understanding is that the issues that you highlight are generally associated with heavier runners and weaker motors (the idea being that the belt is slowed with each footstrike and then speeds up during the float part of the stride).

2) If the treadmill was overheating and changing speeds on my longer runs, I would expect that to be reflected in the RUNN sensor as well (i.e. there would be a difference between the pace on the console and the pace reported by the RUNN Sensor). Nope - they're both in sync all the way, while the Stryd pace varies. (I've been testing by using two watches on my treadmill runs - one synced to the RUNN Sensor but also using Stryd for power, while the other takes distance, pace, and power from Stryd.

3) the inconsistencies I've noted with Stryd apply both inside and outside.

darkwave,

With this new information, I'd say the RUNN sensor is accurate and something is wrong with your Stryd. My Stryd is consistent with every run regardless of what I'm doing.

I had a friend purchase a Stryd that was wildly inconsistent that he returned, so I know it's possible to get a bad one. I must have just got lucky!

BHViking wrote:

I'm sure the NPE Runn is accurate but to say the Stryd is inaccurate based on the forum responses isn't a very scientific method of coming to that conclusion. I've read those forums and nearly everyone there claims the Stryd accuracy sucks because it doesn't match the treadmill.

"Your product sucks because it doesn't match the result of wildly inaccurate and uncalibrated gym devices"

The Stryd is sensitive to where you put it on your shoe. You will get inconsistent values if you change shoes, etc.

You have to understand how the data is gathered and recorded.

You don't say how the data was recorded, I assume you are using the stryd powercenter and the pod's own recording vs going through your watch.

In that case the stryd doesn't record every second, they use a kind of recording every few seconds. If it goes through a watch the recording can be every second so there is more precision.

Secondly, it's guessing distance ove rtime based on your time in the air between impacts and forward velocity.

Except you are not on a hard surface, you are bouncing on a surface that is slightly moving up and down and recoiling with impacts.

If the treadmill is using a meter that is like an old-school bicycle meter that uses a physical rotation counter so it knows exactly how far the belt has moved on each rotation, well then it's the most accurate.

It occurs to me if someone had a home treadmill they could lean their bicycle wheel against the tread so it spins and use one of the old-school meters to check real speed/distance. Even the newer meters might be as accurate with the spinning magnets if there is no interference or dropout.

BHViking wrote:

its only 5k wrote:

The NPE Runn is very consistent if you have enough marks on the belt. The Stryd is super consistent on the road but not necessarily accurate. On the treadmill the Stryd is crazy wrong and is unable.

Many people on the their forum report this is. I have a manual curved treadmill so the difference is more pronounced

I'm sure the NPE Runn is accurate but to say the Stryd is inaccurate based on the forum responses isn't a very scientific method of coming to that conclusion. I've read those forums and nearly everyone there claims the Stryd accuracy sucks because it doesn't match the treadmill.

No one stating that seems to consider the fact that the treadmill speed may vary over the course of the workout.

Ah come on, even stryd owners say that they know about the inaccuracies on a treadmill with the Stryd pod compare to on road/track and it’s something they have been working to fix for several years.

For some the differences are minor and others far more but it’s 100% repeatable. As the treadmill speed increases the scaling continues to draft from expected and very noticeable if you have other goes multiple sources to compare.

If you have many stryd pods you will notice the consistency is there but the accuracy is not a scaling needs to be applied, I’ve been using various different stryd pods for years and it’s just something to be mindful off.

Also shoe stack height seems to play with their accuracy too.

Yeah, my experiences with the Stryd pod mirrors your points exactly.

For me, the scaling factor is off when running outside as well. And I can’t fix it with calibration, because a single calibration factor will only skew where on the pace curve the Stryd tracks accurately. It’s quite annoying, to be honest. I essentially have to choose whether I want accurate pace and distance readings for my easy, moderate, threshold or hard runs.

Also shoe stack height definitely affects accuracy on the treadmill. Running at the same pace on a treadmill in a pair of Floatride Run Fast (pretty low stack) vs Vaporfly (high stack) will result in a 10 sec/km difference in pace reported by Stryd.

It’s only useful on the treadmill because it offers some sort of consistency and repeatability over time. Outside, I’ve dropped it and just use GPS because it is generally more consistent over a range of different paces.

Add in the known problems with getting accurate readings with asymmetric lacing (Vaporfly Next%) and it is not reliable enough to rely on in race settings. Or training in varied conditions over time, for that matter.

Like darkwave I did loads of advanced tests of Runn vs TreadTracker vs footpods vs watch / chest strap accelerometers etc. I used measuring wheels on the belt, stickers and high speed video, HR, RPE etc. I can assure you the Runn is by far the most accurate followed by TreadTracker. Footpods and accelerometers were useless.

I can also confirm that the treadmill speed feedback is rubbish and results in the belt speeding up anything up to 5% over the course of a steady speed (according to treadmill) run. E.g. 11 to 11.5 kph.

I have a NordicTrack C2950 so top of the line kit.

The recent 100k treadmill record was done with a Runn. Bottom line it's the only one worth using on a treadmill.

I meant to say the treadmill DOES speed up over an hour like BHViking reports and it's perfectly recorded with the Runn and TreadTracker but of course the treadmill says it's stayed constant.

Might be a NordicTrack quirk, who knows?

Indeed throughout long runs I have to dial the speed DOWN gradually but ultimately 0.5 kph on the treadmill to actually keep the belt speed (which is all that matters) constant. E.g. 5 min/k starts out at about 12.1kph on treadmill and finishes at about 11.6kph.

I'm using the Stryd this way indeed. Stryd is on the shoe and Garmin Fenix + HRM-Tri+NPE Runn as the concurrent measuring setup.

Thank you for pointing this out. It was intended because I wanted to compare Stryd to Runn before switching from one to another. I'll try with Stryd connected to the watch, but the general picture stemming out from the other responses is that the Runn is still better for treadmill pace. I'll check Stryd this weekend outdoor also to compare results with the Garmin GPS and also try if possible to use Runn for pace and Stryd for power at the same time.

The idea to use HRM to verify Stryd is also good I think, and in my case it just confirms that Stryd is way off on treadmill, about 60sec/km.

The other thing I was wondering was to which of the shoes should I put my Stryd on? The stronger left leg or weaker right? Or maybe it always should be right or left? What do you think?

LTHR hurts wrote:

I meant to say the treadmill DOES speed up over an hour like BHViking reports and it's perfectly recorded with the Runn and TreadTracker but of course the treadmill says it's stayed constant.

Might be a NordicTrack quirk, who knows?

Indeed throughout long runs I have to dial the speed DOWN gradually but ultimately 0.5 kph on the treadmill to actually keep the belt speed (which is all that matters) constant. E.g. 5 min/k starts out at about 12.1kph on treadmill and finishes at about 11.6kph.

Like you, I have noticed this on my previous NordicTrack T12. Pace got progressively faster as reported by Runn sensor (no calibration), without me changing the speed on the mill itself.

Very similar Stryd experience here. I had the thing track calibrated to every shoe I own. My pace/distance started to show fast/long. Re checked some shoes and the calibration factor was now different. Same shoes, track, protocol, etc. Stryd told me there was nothing they could do to help and would not even exchange me out for a new unit.

Nothing is ever their or the products fault. The blame was always given to something else. My error, treadmill, shoe placement, track, didnt follow protocol, maybe a future update will fix your issue, etc. etc.