Forums >Gears and Wears>Garmin footpod accurate on treadmill?
Evolving body parts
So last year I bought a footpod to measure + help increase my turnover. I was amazed how accurate it was compared to what the GPS yielded. My typical route is a ~10.7 km loop and the GPS measures it between 10.65 and 10.80. The footpod measures it 10.7 to 10.8. On other distances they are matching as well.
I don't really care, thea are both really accurate and consistent, the footpod being (surprisingly) the better one at repeatibility.
Now, when I use the pod on the mill, it measures 7% to 10% faster speeds than what the treadmill display tells me. I use whichever TM is available at the gym and they are all off compared to the footpod by about the same margin. Most of the time I set 1% incline.
This makes me wonder:
a) Are the treadmills accurate and both my GPS and footpod are off?
b) Is there a difference in physics / the way the footpod is moving when on the treadmill? (I know this has been discussed before)
c) Are all the treadmills inaccurate, perhaps deliberately?
Anyone experienced this amount of difference?
There are a few good posts in this thread regarding the difference between the TM and the foot pod. It's worth looking at them. But it does seem typical to have that amount of difference.
http://www.runningahead.com/forums/topic/16e811b8f2b4443286aafdd00966df34/0
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And we are the dreamers of dreams,
Wandering by lone sea-breakers,
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World-losers and world-forsakers,
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Yes, it is quite good, within 1-2%, IF first calibrated to a known distance outdoors (or autocalibrated by GPS on some of the newer watches).
- Joe
We are fragile creatures on collision with our judgment day.
Treadmills, particularly those in gyms, are often quite far off. I have used my calibrated footpod on numerous gym treadmills (about 15 total). I have found them to be as far off as 0.1 of a mile per mile to being right on. Just about every treadmill's display shows I am gong slower and covering less ground than my Garmin with calibrated footpod.
I suspect there is some difference in physics. The big question is whether your cadence inside on the treadmill is the same as your cadence outside.
Most gyms do not spend a lot of time initially calibrating their treadmills when they first set them up and keeping them calibrated given the amount of use they get. So no they are not deliberately inaccurate, just generally not calibrated.
Thanks guys, I kinda hoped that the footpod was more or less reliable. BTW I never calibrated it, it was a very close match to the GPS out of the box, so I didn't mess with it (maybe autocalibrated itself?)
My average cadence is about 170 outside and about 174-176 spm on the mill. There is room for improvement, but I'm a tall guy (6'6) and it's pretty awkward for me to move my legs fo fast. Higher cadece are much easier on my legs & feet, that's why I want to improve in this, but soemtimes feels like my feet are tied together
The question now is why can I run so much faster on treadmills than outside Okay, it does not let you slow down when you are a little out of breath or unfomcortable, and outside runs are dark and cold, but still. This 5-10% faster tempo feels about the same as the slower runs outside. Some of you can compare these tempos to the seconds and know which ones are the same exertion level and I wonder how you do it. The are so much different...
Not the end of the world either way, but now that I'm running 200mi/mo I'd like to know more about my progress and limitations.
My average cadence is about 170 outside and about 174-176 spm on the mill. There is room for improvement, but I'm a tall guy (6'6) and it's pretty awkward for me to move my legs fo fast.
At your height, 170-176 is probably just fine and doesn't need "improvement." http://sweatscience.com/how-limb-length-affects-running-cadence/
I use a footpod on my treadmill and believe it to be more accurate than my treadmill. My treadmill will vary in speed, sometimes slow and sometimes fast. Calibration would be an exercise in futility.
I calibrated my footpod on the track and was able to get it so consistent it always turned a quarter mile about 3-4 steps past the 400 line.
A big benefit of using the footpod is logging your mile splits. This is nice when you want to see workout splits, a progression, or whatnot.
I think the footpod might be of use to ultra runners. If you turn the GPS off and just use the footpod I'd bet battery life is probably a couple days. It's still about as accurate or inaccurate as a gps.
The Garmin 220/620 (and probably the big wrist pc version that gives you email and texts while running) have built in accelerometers that are almost as accurate so anyone with one of those watches can use them on the treadmill and log distance and splits.
I got a 220 recently and I've hesitated to use the accelerometer on the 'mill yet because since I've owned the thing I've only done 3 runs outside and they were all at least partially in snow and so I doubt the thing has "auto calibrated" correctly. But I think I'll give it a whirl just now and see how it does compared to the treadmill's version of distance and pace.
Runners run
It (internal accel.) will not do well on the dreadmill I am sad to report. It will do OK on an indoor track (after a few good runs outdoors that is -- not sure if your snowy runs would qualify). There is something that changes enough biomechanically between running over ground and on a treadmill that the integration of the acceleration on the wrist doesn't work out very well, whereas the footpod still does pretty well.
You are correct, Joe, it was pretty far off. Not a big deal ... it was more a curiosity than anything. I don't really need my watch to keep track of my time and distance on the 'mill.
The interesting thing is my watch pretty much thought I was running about 8:11 pace regardless whether I was running 7:40 or 7:18 or anything in between.
Joggaholic
That's interesting, I have an ambit2r that uses internal accel. and its always off when calculating distance on the TM. I don't really care but it's a curiosity that I noticed, because I always have to change the mile split after I upload to RA. I usually hit the lap button as the TM hits 1 mile, and after I upload the file, the "mile" split will be at 1.1 miles, 1.3 miles... etc, just way way off.
Well, on the subject of cadence and the magic 180 spm. I tend to agree with you, but being an experinting spirit, I am testing different cadences to see what value works best. Internet wisdom (well, half of it) says that one should go up to 180 no matter how tall he/she is, because the biomechanics behind it (elasticity etc.). If a tall guy, like me runs with the same cadence, keeping the same hip opening would mean that I'd be faster than a shorter runner. The speed would be proportional to the height difference. Needless to say, I am not any faster.
That leaves using a smaller hip opening (so that the stride length is similar), resulting in an awful short-step shuffle, as if walking on eggs. My feeling is that strange leg angles could be as bad as overstriding when it comes to efficiency / injury prevention.
Here's a primitive sketch as to what I mean (excuse my drawing skills) - assuming constant cadence:
So any tall + not too fast + 180 spm guys around here?
I don't think you are considering the human gate cycle correctly, at least not for running. In running, you are forgetting that your knee actually bends, and that, regardless of the length of your leg, your foot should land pretty much directly under your center of mass with each foot strike.
With the same hip angle, your knee may project out farther in front of you than a shorter runner's knee, but that on its own doesn't matter a whole lot to running speed. And you also can't assume the same hip angle as a shorter/lighter/more fit runner. Power to weight ratio, hip extension, cadence ... these things are all parts (and I would say effects) of running fitness just as much as endurance, VO2max and LT. You can't artificially change one variable just by deciding to and expect it to make you faster.
It's like saying that any sprinter as tall as Usain Bolt who runs with the same cadence and same stride length as Usain Bolt, should be able to run as fast as Usain Bolt. No shit, Sherlock--but that's getting your cause and effect backwards.
Of course I get it that the gait is a complex thing. There are no knees on my drawing, I simlpy wanted to make a point regarding the awkwardly short stride length with the high turnover.
In my case, going from 160-165 to 170-175 and keeping the grund contact under my cetner of mass already made a huge difference. I feel the runs with same percieved effort much less taxing on my legs & feet.
I really don't want to overanalyze this, but can't help wondering how I'm supposed to move my legs fast AND have my heels up to my butt (for a decent form / gait) without speeding up too much - to a pace I can't keep up for long. So the result is a ridiculous far-from-graceful, quick, short-step (albeit injury-free) shuffle
I'm 6'6" and have a turnover of about 178 when running easy, something like 185 when running 10k speed, and 195 when running mile-ish speed. I don't overthink my cadence, I happen to know it because I often run on an indoor track with a foot pod. I'm a fore/mid foot striker if that info is of any use.
Some people say I look funny when I run because I have a rather short stride. But having a short stride doesn't mean you can't lift your heels high to your butt IMO.