probably neither, but seeing you have an expensive ass treadmill i'd wager that.

I always use time on a treadmill and effort. My Fenix5 is all over the place in terms of pacing and the treadmill I was using was fairly old.

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You have four things (at least) working against one another. So, the short answer is that it is probably unknowable...

1. The Treadmill's calibration
2. The foot pod's calibration
3. Your stride & cadence changes while on a treadmill versus your stride & cadence while running outdoors (where the pod likely calibrated)
4. The belt's behavior of slowing during the moment you are in contact and then unloading and speeding up while you are momentarily airborne

You got a 3% difference, which is pretty much a home run in this situation.

I tend to agree with the previous responses, but thought I would mention how intrigued I have been to see my Stryd measure distance/speed on different treadmills.

My home treadmill is a cheap "Commercial" Nordic Track that measures fairly consistently 2-3% longer than my Stryd.

I have spent around 6 weeks this year on work trips (spaced across the year, 1 week at a time) at the same hotel. On each trip I have run on their treadmill and noted my Stryd measured 1% longer than the treadmill each time.

During the last year I also ran on another treadmill at a hotel, it felt really funny like it was even slipping as I landed on the belt and my Stryd came out much lower (~10%) than the treadmill claimed.

The wrist based treadmill distance (even "calibrated") on the newer watches is neat but really has given random results in my use. It's better than nothing for recording that an activity happened, but can be way off (as I think you'd possibly expect).

Are you using a footpod? If so have you done any type of calibration?

Only the finish line counts.

Sounds like you need one of these:

https://www.dcrainmaker.com/...admill-accuracy.html

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Practise doesn't make perfect, practice makes permanent. Only perfect practice makes perfect!

Does 3% difference really matter? Pick one method of measuring and stick with it. Better yet - go by time.

Problem solved.

Wouldn't having another indicator of intensity while on the treadmill make it easier to compare to other runs on the treadmill?

I agree. Especially with the idea of measuring by time.

My $.02... Up till a month ago, I ran the treadmill with a Garmin footpad... The footpad always had my pace 20-30sec faster than the treadmill reading, I always suspected that the footpad was off... Fast forward to now, I have a Stryd footpod... Turns out the treadmill's speed was damn near spot on compared to the Stryd.

I used to run on a woodway at a previous gym and used the treadmill setting on my 935. The Garmin was within 1-2% for runs under 90 minutes and 3% for 2hr+ runs, probably due to fading form. I think woodways are pretty accurate but at 3%, just pick one for consistency.

I moved to a country that uses km so I changed the distance units on my 935 and now it is giving me stupid paces no matter how many times I "calibrate" the distance. It's nearly 50% off, telling me I'm doing 4 min miles that are actually 7 min...

Unless the treadmill slows when you foot lands and speeds up when you have both feet in the air. Has anyone figured a way to account for this?

The accuracy of the treadmill is pretty easy to determine. Just use a measuring wheel for a given time. Do it at a range of speeds if you think it might vary.

EDIT - actually, the Woodway complicates this since it isn't powered. I guess you could have someone hold the wheel on the belt while you run.

I know this is an out thread, but I wonder what I should use when running on an older treadmill at my gym. Should I use the watch pace/distance or the treadmill's? I generally don't care that much, as I'm running mostly based on time. But if I have intervals and the weather outside is too bad, what device should I use?

I assume the treadmill, because my Fenix 7 can't really measure distance when I'm not going anywhere. But I suspect, based on effort, the treadmill I normally use is way off (harder effort than I would expect for the reported pace).

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Not a coach. Not a FOP Tri/swimmer/biker/runner. Barely a MOP AGer.
But I'm learning and making progress.

The tempo run before I bought my Stryd:

Woodway: 7mi
Garmin Fenix 6 Pro: 5.65mi

Woodway is accurate within 2% of the Stryd on all runs, 1% on most, and dead on for a respectable amount, DWIW.

I used to think this was a factor but now I doubt it.

I hooked up a Runn sensor to my TM - it uses stickers on the belt and can measure the distance between them as well as the pace they're flying by to give you your TM pace.

On my Sole F80, if I set it to 7:00/mile, it'll take like 90 seconds to get to around 7:20/mi, then another entire minute to get to 7:00-7:05. But then it settles it pretty much exactly to the speed the treadmill says it does. Kinda amazing, actually.

I think the treadmill does small adjustments once you're at a certain speed that compensate for your weight/footstrokes, which seems to be why the Sole takes so long to get to speed. If I do the same TM test without me on it, it gets to that target 7:00/mi a lot faster (haven't measured it, but it's a good deal faster for sure.)

The Runn is good, I'd recommend it to anyone who's doubting their TM accuracy. I put velcro tape on the back side of the treadmill and velcro the Runn unit to it when I'm running, then remove it once I'm off so it doesn't get kicked.

Most woodways are powered. I would assume the op is using a powered one.

Woodways don’t have nearly the same pause on the belt that a belt treadmill has when you foot lands. I’ve never noticed any pausing when my foot lands but definitely notice it on a belt. You probably need a high speed camera to see if there is really any pause in the slats.

I find woodways follow my stryd pretty damn closely. Any other treadmill is all over the place compared to my stryd.

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The runn is the only option imo. Treadmills are very rarely stable in speed because of foot fall and engine dynamics, the runn can account for that. I have as many lines as is allowed to maximize accuracy. The only problem is if you don’t have a treadmill at home or travel.

Other people have shown good reports of accuracy with garmins and stryds but that hasn’t been the case for me. Stryd, garmin pro hrm, and garmin watch were all way off on anything other than slow steady state. The runn is the only thing I’ve found semi accurate.

Fwiw my landice l7 is within about 3% of the runn depending on speed. It gets up to speed pretty quick but does drift a bit as time goes on. But still was closer to the runn than any other devices I’ve tried.

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