Is treadmill running speed accurate?

is it accurate? thats a bit of a generalisation. Is the one in my gym accurate? yes. Is the one you used? I couldnt say.. By in larger yes. Tredmill running in a well conditioned area takes away a lot of the envrionmental issues you would incounter running outdoors. heat, wind etc

junior wrote:

Is the one in my gym accurate? yes.

Unless you calibrated it yourself, I'm not sure how you would know that.

Things to consider: From what I have seen, even quality treadmills can be off by 10 seconds/mile (yes, sometimes faster, but slower seems to be the norm). Then there is the often cited 1% to 2% incline to compensate for lack of wind resistance. Unless this treadmill is in some beat-up old building, it is probably safe to assume that the floor is level.

In any case, if the treadmill was set for 0%, then I'd say it is most probable that the indicated speed was effectively slower (easier) than the same speed outdoors run on a level surface.

dukerdog wrote:

Unless you calibrated it yourself, I'm not sure how you would know that.

could it be that he's saying his treadmill is accurate because an effort there (with wind taken into account) corresponds to an effort outside on a measured course?

I've never been so sure about using incline to compensate for the wind resistance. I agree that without the 9mph headwind effectively generated by running at 6:40/mile (for example), treadmill running is that much easier. But I've always preferred to make up for it by just setting the machine to 5-10s/mile faster (I'll do 5 miles at 6:00, but log it as 6:10). Running on an incline makes things harder by changing mechanics -- isn't it better to make things harder by going faster?

I've done it both ways (incline vs. faster), but I'll use 1% for base runs and 1.5 to 2% for faster work (as the wind load is not linear with velocity). I don't think 1% or even 2% changes mechanics much. I think JTD recommends using the incline in DRF instead of going faster.

JimFiore wrote:

From what I have seen, even quality treadmills can be off by 10 seconds/mile (yes, sometimes faster, but slower seems to be the norm).

I have to say the same thing to you Jim. How do you know?

I think there are very few people that can estimate their pace that accurately. There's a lot that think they can. But if you have them run 4 laps on a track without a watch they'd be lucky to guess their time +-5 seconds.

the way you run on a treadmill is nothing like that which you run outside. You dont have to propel yourself forward on a treadmill, this changes your entire style. If you simply bounce higher and let the ground float under you you are saving energy. You cannot account times on a treadmill for real running.

you have clearly never run on a treadmill.

I would think that the energy expended and efficiency lost to "bounce higher" on a treadmill would completely negate any benefits one might get by letting the "ground float under you, saving energy." Or maybe I just wasted the last minute of my life replying to a post specifically meant to get uner peoples skin. Only my 2 cents.

yeah there is no benefit to jumping high on a treadmill. you're still going to have to jump "forward" (in the belt's frame of reference) as fast as the belt is moving to stay in the same position in the earth's frame of reference.

dukerdog wrote:

I have to say the same thing to you Jim. How do you know?

That's a fair question. I certainly wouldn't do it by trying to estimate pace by "feel". I don't think I could be accurate to within 10 secs/mile given other variables such as incline.

When I say that my experience tells me that this is so, it's because I have measured a couple of different treadmills (my own) and have also scanned the literature. I've calibrated my TMs by measuring the belt and then running on them while counting revolutions for a specific period of time. I compare the results to what the TM display reads. Being an engineer, I naturally repeat this test more than once (also, it helps if you're just plain obsessive-compulsive). A few years back when I was researching my first TM purchase I came across an article from RWOL wherein they checked the speed calibration of the TMs under test. My results and their results showed that many TMs were not "spot-on", but tended to be within 10 secs/mile, and more often than not, on the slow side rather than on the fast side. My Pacemaster Pro was about 10 secs/mile slow by my calcs and RWOL measured approximately the same discrepancy for it. My current TM (a Bodyguard) came out 2 or 3 secs/mile slow by my calcs (this model didn't exist when the RWOL article was written).

thanks for all the responses....a bit of clarification:

my question was not whether the posted time on the treadmill was accurate (i have no reason to suspect it wasn't) but rather about the mechanics of runningon a treadmill. I never thought about the wind resistance effect.

The only way to tell if a treadmill is accurate is to measure the belt, put a piece of white adhesive tape on it, then measure the revolutions per minute at different speeds.

I did this with 6 or 7 different treadmills in 1988 or so, and only one of them was accurate. It was a Trotter treadmill, but very expensive. None of the others were close.

The treadmill I have now is not accurate, but I have calibrated it and account for the difference.

There is another issue. Even if the treadmill itself IS accurate, you may not be running at the exact pace the treadmill is set to. In other words, while you certainly will not run slower (you would not be able to keep up), I have found that I can lapse into running faster than a set pace (I don't know by how much but I can tell that I am moving faster than the belt it moving). Genrally, however, they seem to be accuarate within about 10 seconds per mile which, for the types of workouts most of us do (i.e., tempo runs or easy recovery runs or longer easy or pace runs) should suffice.

but were the inaccurate ones within 10 seconds as Jim Fiore said?

Also, readers should scan this other thread for possible answers:

http://www.letsrun.com/forum/flat_read.php?thread=625093&page=0

I should have known better than to think Jim Fiore would say something without having data to back it up. I figured you had calibrated your own treadmill but didn't think about the possibility that RW or some other magazine might have done several.

One caveat to both your tests is that you were testing relatively new ones. With that in mind I decided to finally go to the basement and test out my 10-year-old mill. I paid about $2400 for this guy 10 years ago, so it is a pretty serious machine.

The results:

Pace set to 7:04/mile - actual pace was 6:54/mile.

Pace set to 8:00/mile - actual pace was 8:13/mile.

Don't believe everything an electronic display tells you!

the_truth wrote:

my question was not whether the posted time on the treadmill was accurate (i have no reason to suspect it wasn't) but rather about the mechanics of runningon a treadmill.

Short answer: Basically they're the same once you compensate for wind resistance (1% to 2% as noted). Also, using a fan helps to remove the microenvironment of warm air that builds up around you. If you do those two things I'd say that the mechanics/effort are as close as any two road circuits you might compare. The psychology of TM running is another matter (some like it, some don't).

I have no idea how Swamprunner manages to run at a faster pace than the TM without slamming into the console. Turnover might be quicker than it is outside, but you can't run faster (or slower) than the belt and not eventually run off the end of the TM.

dukerdog: I am surprised that you found errors both fast and slow, especially within a fairly narrow pace range. I have never seen that. If anything, I would expect the TM to be slow at higher speeds due to slippage and the extra force required by the motor (unless the designers overcompensated for those factors).

As others note, you are neglecting air resistance (even on a calm day you still expend some energy moving the air out of the way).

IF the treadmill is calibrated, it would probably be close although heat stress on the TM could be higher (depending on a lot of factors there).

As for the 1% or 2% claim, it comes from this paper

J Sports Sci. 1996 Aug;14(4):321-7. Related Articles, Links

A 1% treadmill grade most accurately reflects the energetic cost of outdoor running.

Jones AM, Doust JH.

Chelsea School Research Centre, University of Brighton, Eastbourne, UK.

When running indoors on a treadmill, the lack of air resistance results in a lower energy cost compared with running outdoors at the same velocity. A slight incline of the treadmill gradient can be used to increase the energy cost in compensation. The aim of this study was to determine the treadmill gradient that most accurately reflects the energy cost of outdoor running. Nine trained male runners, thoroughly habituated to treadmill running, ran for 6 min at six different velocities (2.92, 3.33, 3.75, 4.17, 4.58 and 5.0 m s-1) with 6 min recovery between runs. This routine was repeated six times, five times on a treadmill set at different grades (0%, 0%, 1%, 2%, 3%) and once outdoors along a level road. Duplicate collections of expired air were taken during the final 2 min of each run to determine oxygen consumption. The repeatability of the methodology was confirmed by high correlations (r = 0.99) and non-significant differences between the duplicate expired air collections and between the repeated runs at 0% grade. The relationship between oxygen uptake (VO2) and velocity for each grade was highly linear (r > 0.99). At the two lowest velocities, VO2 during road running was not significantly different from treadmill running at 0% or 1% grade, but was significantly less than 2% and 3% grade. For 3.75 m s-1, the VO2 during road running was significantly different from treadmill running at 0%, 2% and 3% grades but not from 1% grade. For 4.17 and 4.58 m s-1, the VO2 during road running was not significantly different from that at 1% or 2% grade but was significantly greater than 0% grade and significantly less than 3% grade. At 5.0 m s-1, the VO2 for road running fell between the VO2 value for 1% and 2% grade treadmill running but was not significantly different from any of the treadmill grade conditions. This study demonstrates equality of the energetic cost of treadmill and outdoor running with the use of a 1% treadmill grade over a duration of approximately 5 min and at velocities between 2.92 and 5.0 m s-1.

PMID: 8887211 [PubMed - indexed for MEDLINE]