Probably neither, but I would trust the Polar before I would trust the treadmill. Those things have to be recalibrated at regular intervals as the result of wear and treadmill stretch, especially on new treadmills, can affect the accuracy by as much as 8%. Additionally, they are rarely calibrated by a treadmill service professional (TSP) during the initial install. The process is quite involved (depending on the exact make and model of the treadmill, of course) so many places don't bother to do it properly as just having a moving walkway is enough for most people. It makes me angry.

In any case, unless you know your treadmill has been recently calibrated by a certified TSP who is current on their certification, I would take any numbers with a grain of salt. At least the Polar is calibrated. My plan of attack when I must use a treadmill is to base my workout off of time and heart rate.

Sorry for the longer post but treadmill maintenance is just a touchy subject.

I would trust more the one the makes the most sense of PE vs time.

I assume you should be able to differentiate 5 miles in 50min and 5.75miles in 50min

That's some good logical thinking.

jaretj

Have you ever calibrated the V800 using a known distance? If yes, then I would trust it over the treadmill. Most treadmills I run on are pretty awful at reporting the correct pace. Some are off on pace by a minute per mile (tested using Garmin footpod).

A funny thought: if you own the treadmill, you could get a bike with a rear-wheel sensor and test the treadmill for accuracy. Probably while holding the bike and not sitting on it. :)

If you put wings on your bicycle on your treadmill, would it take off?

It definitely would, most likely in a rearward direction. Though I suspect it wouldn't get very far. You should video an attempt.

I was actually about to recommend that. It's hokey as all hell, but if you very careful measure your wheel circumference (and input it into the computer in the proper format), I think this would be the best way to calibrate your treadmill. It'd be pretty easy to do this for a distance longer than most of your runs.

The other option is to use something like this: http://www.amazon.com/...412284182&sr=1-3

Either way, make sure there is no slipping with the wheel!

Works quite well :) This is how I "calibrated" my outside pace to my treadmill speed

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Rodney
TrainingPeaks | Altra Running | RAD Roller
http://www.goinglong.ca

I haven't calibrated either. But the Polar tells me I ran 5.48 outside when Runkeeper says 5.03 and the mapped distance is 5 miles or so and it gives me different readings doing the same route.

I'm gonna try the Polar Beat with the iPod Touch and the Stride.

[quote nickwhite
A funny thought: if you own the treadmill, you could get a bike with a rear-wheel sensor and test the treadmill for accuracy. Probably while holding the bike and not sitting on it. :)[/quote]
Nick,

That is a brilliant idea. I have a NordicTrack treadmill for 3 1/2 years now. I don't think it is off BUT it has never been calibrated.

I will let you all know what comes of the test.

i have done this last year with my Sole treadmill, at speeds in steps of 2 mph and all inclines. Turned out the speed was spot on! Interesting because i did that after thinking my RPE indoors was higher than outdoors and i thought maybe the speed was off, but it wasn't. It was just me bring a pussy.

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Don't forget to attack!

I just used my road bike that has a cateye double wireless computer on it. The computer is dead on, I have found it to be in 100% agreement with mile markers and my Garmin GPS.

I found that the treadmill is .1 miles more than the bike odometer. Meaning I am running an extra .1 mile for every mile on the treadmill. Nothing I can't live with.

You could also use a measuring wheel, something like this. Be sure to test at various speeds. Just because it is spot on at 7MPH does not mean it is at 8MPH. Best to run multiple test in a range of speeds. This way you can always manually adjust if the treadmill is off on certain speeds. It's also good practice to regularly do this.

Trust the Treadmill. However this is a catch. The stride sensor is fooled by the moving treadmill. you cannot have the treadmill calibrate manually for your outdoor runs. I learned that the stride sensor measures a lot of things, one of which is the speed and angle that the foot hits the ground. Given that the treadmill is a moving "ground service" it fools the stride sensor into a false reading. The best way to calibrate the stride sensor and V800 for outdoor running is to go to a high school track and run 4 laps while setting the calibration setting to test distance of 1600 meters. Very important - set your watch to the metric system before you start the calibration session. Otherwise there is a complex formula to convert. This will give you a very solid read for calibration for outdoor running. For running on a treadmill you will have to use a different sports profile with a different calibration setting. Setting the treadmill calibration reading is trial and error. You have to enter the calibration setting manually. It works fine on a treadmill so long as you run at a steady speed - like 8 mph for 45 mins. but if you run "hills" or intervals on the treadmill, the calibration will be off.

calibrate your Polar

I wish there was a way to calibrate it without a track as the nearest track that you can get into here is 45 minutes away or so. Just going to have to take a few hours on Sunday and get it done.

Take your bike out and mark the beginning, then ride a mile or two and mark the end. Now run it. The bike will be close enough

I was hit by a car in May while on a bike and I can't bike or swim without pain (which is why accurate running is so important to me right now, it's all I'm doing). I was thinking of doing it with the car. That, and I don't have a helmet at the moment since the bike and helmet haven't been replaced yet (I had a second bike).