This will vary greatly between treadmills. However on the same one, 12km/t is most likely the same as 12km/t the next day. Youre fine to track fitness increase vs previous tests on that same tread, but dont compare different treads og tread/outdoors.

We just had this discussion on a tangent from some guys thread about his shitty treadmill..Here it is:

http://forum.slowtwitch.com/...ill%20speed#p6568314

Cliff note version is that if you run low 7 minute mile or faster, around 1% incline, if slower then leave it at 0. But of course if that is true, then why not .5% for the middle speeds around 7 minutes per mile, increasing the faster you go? Of course this all assumes you are on a good treadmill that is closely calibrated to begin with, some are just way off and you just need to figure this all in when setting speeds.

And apparently it is to simulate what wind resistance would hit you in the real world, so I actually run on one in the open with a headwind, so problem solved!!! (-;

Put your treadmill at 10mph and then take your bike and put the back wheel, or whatever wheel has your speed sensor on it, on the belt and see what speed comes up on your bike

At my gym some "identical" treadmills are definitely faster than others. I marked the belts on two of the ones next to each other with a tape square and ran them both at 12mph and you could clearly see that one tape square was "lapping" the other.

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ECMGN Therapy Silicon Valley:
Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)

Unfortunately the treadmill could be slowing down when your foot hits it then speeding up while both feet are in the air, the average speed would be right but not what you actually are running. Probably a bigger problem on a treadmill with a weak motor. My theory is people who claim the treadmill is easier because it 'pulls your leg back' are subconsciously causing this to happen more.

I use a foot pod when I run on the treadmill, they seem quite different from each other and even they same one will sometimes 'drift' during the workout.

That's brilliant!

Also

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"What's your claim?" - Ben Gravy
"Your best work is the work you're excited about" - Rick Rubin

Hah - for me, anyone that is 'racing' me on the treadmill next to me, isn't fast. If they were fast, they wouldn't bother, or they'd just blow my doors off.

I get impressed when someone jumps on the TM next to mine and drops 6:30/mile for 10 miles, but it's pretty rare. I never feel any urge to race any of the folks around me - I'm doing my thang, and it's gonna hurt. But I do take pleasure in probably inspiring more than a few walkers/joggers to amp it up when I'm next to them dying on intervals or tempo runs, and they're just strolling along enjoyably. Most of the time, these happy strollers shut down their music and even break out into brief jogs, which is def good for them!

That reminds me of an encounter a couple years ago

I got to the Gym as a severe thunderstorm rolled over us; yes, thunderstorm in February [or Feb-tober, as I'd been calling it]

There weren't many folks there, so I was able to select a good treadmill for myself. After, laying my stuff out, I realized that I'd left my FitBit in the locker room, so I scampered back to retrieve it. When I returned, I saw that a dude had grabbed the 'Mill right next to me, even though there were several to choose from elsewhere on Cardio Row. He was tall, maybe 10-15 years younger than me, and wearing a tank shirt, split shorts and a baseball hat

[if you're running indoors, on a treadmill, why a hat? You're not gonna get rained on and the sun won't be in your eyes]

I did a light stretch and monkeyed with the TV while he fooled around with the dashboard on his machine. He got himself going just a few seconds before me. He had a pretty decent stride, and wasn't landing heavily enough to make a lot of racket on the deck.

As he settled in, and I began to chug along myself [with not nearly the same fluidity] I made the mistake of peeking at his stats. He was plugged into a pace 1 mph faster than me

'Don't worry about that' I told myself 'he's younger and taller, so he's naturally going to be quicker. Just focus on your numbers, watch the game and do your workout'

I followed my own advice pretty well, with only a couple more peeks to my left to see how far "ahead" of me he had gotten

I had given myself three goals to run to: a certain distance, then a certain time, and if I still fell good, "next commercial break" which then became, "next even mile marker after play resumes"

Finally, I came to the point where I had to stop to get my cool down and get on home. He was still striding along beside me as I plugged my earbuds in, and began my post-run stroll. About halfway through the second song on my playlist, he shut down as well and hopped off to get paper towels & spray to clean off his station

I dismounted as well, to say to him "That was fun"

"Yeah, it was" he replied "I probably would have stopped earlier if you weren't there"

Imagine that, little old me, persuading the better man to keep at it

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"What's your claim?" - Ben Gravy
"Your best work is the work you're excited about" - Rick Rubin

Buy a Stryd footpod and never worry again about treadmill speed variation.

As other people have said consistency between treadmills is pretty poor, but the same one is normally constant, but may not be precise.

The Landice I have is .5mph off. It is consistently off by this though. I have a Garmin footpod and it is always the same between days. The thing has been moved a few times so I think the speed sensor somehow got messed up from moving.

The only time I have issues with it not matching up is when I have a bump in speed it’ll throw the footpod off but running outside will easily recalibrate it.

This.