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Treadmill Running - Watch Inaccuracies

Former Member over 8 years ago

Hey guys !
I had a few runs which showed me very different summaries that probably should not have happened, I was wondering what might be the problem.

All three runs:

- 5 min warm up, speed of 11 kph
- 10 min run with intervals of 20 seconds speed of 17 kph and 40 seconds speed of 11 kph
- 5 min cool down, speed of 11 kph

Summary of 1st run - Distance was recorded to be 5.51 km
Summary of 2nd run - Distance was recorded to be 6 km
Summary of 3nd run - Distance was recorded to be 5.67 km

The differences are huge.. I can understand how 5.51 and 5.67 could happen, after all, it's based on movement and not GPS.. but 6 km with the same treadmill speeds ?? Treadmill moves exactly the same way every single time, doesn't make sense for me to run further somehow.

Thanks !

0 timgrose over 8 years ago

In this mode, the distance is modelled by correlating arm swing rates to pace as observed when you are running outdoors.

This can work fairly well for steady state runs when you don't use the arm with the watch on to take a drink or use a towel etc.

It tends to work far less well for short intervals. Trying looking at the distance accumulation on the 5 min warm up/cool down periods and see if any better.

If you regularly use a treadmill, it is best to get a foot pod.

0 NickMN over 8 years ago

Also depending on the runner - cadence and pace are not that closely linked.

Only time I have found it to be very accurate if I run at a nice steady pace without much elevation/slope on the treadmill - right near my easy/conversational pace.

I still use it in 'Indoor Running' mode - its very easy to go online (computer , not that App) and edit the distance after (as well as add in any elevation gain). Typically I am doing quite a bit of hill climb action on the Mill (live in a flat area...) so it likely messes with my cadence/pace relationship.

0 Former Member over 8 years ago

Hey guys, thanks for responding :)
I am assuming that according to interval speeds I'm swinging my arms faster and slower and it counts it as such? I am not using any elevation by the way.
According to the treadmill, the distance is about 4 km which is probably correct. According to the FR235 it is sometimes 5.5 km and can even tell me I did 6 km.. that gap is enormous isn't it?

0 lightmatter over 8 years ago

It all depends on the cadence and distance per stride when on a treadmill. Interval work on the treadmill is going to be the worst, especially when you have a lot of slower speeds in there. At slower speeds your stride length shortens, but the watch has no way to know that. So if you're doing the recovery sections at say 120 strides of 1 meter each minute, the watch will think it was more like 120 strides of 1.2 meters as if you were running. Hence the gross overestimation on your distance.

0 Former Member over 8 years ago

Ok, I tried running for 5 minutes on the treadmill with a steady speed of 11.2 kph.
Result on the watch showed I did 1.40 km, result on the treadmill showed I did 0.9 km.. Still a big gap that I imagine grows the longer the run is.

0 lightmatter over 8 years ago

Simply means it does not have any idea what your stride length is.
Have you ever run with the watch outside with the GPS on, that is how it tries to calibrate stride length.

If you have run with the GPS on, maybe you take ridiculously different stride length on treadmill vs outside? Or have a bizarre arm motion that increases cadence accidentally. The overall distance doesn't tell anything about what is wrong, you need to look at the cadence & stride length numbers per lap to figure out what is out of whack.

0 Former Member over 8 years ago

Simply means it does not have any idea what your stride length is.
Have you ever run with the watch outside with the GPS on, that is how it tries to calibrate stride length.

If you have run with the GPS on, maybe you take ridiculously different stride length on treadmill vs outside? Or have a bizarre arm motion that increases cadence accidentally. The overall distance doesn't tell anything about what is wrong, you need to look at the cadence & stride length numbers per lap to figure out what is out of whack.

Ok I will check it out and get to the bottom of this. Thanks !!

0 Former Member over 8 years ago

I think accuracy can vary depending on where you live (buildings, etc can interfere) and the type of treadmill you are using. Anyway, I always find that it's simply easier to run outside. You have a better cooling system as you're actually moving through the air (some treadmills have fans but they're just not as good).

0 R_Tellis over 8 years ago

The internal accelerometers in the watch will at first be using a generic profile to determine pace/distance on the TM but will self-calibrate when used outside with GPS. What I've found though is that the more I run outside the less accurate it is on the TM to the point where the watch is seeing a pace that is 30 sec/mi faster than the mill is set to.

What works best for me is doing one, or two at the most, easy runs outside with a foot pod set to self-calibrate and then only use the pod on the TM after that and I get readings that are very close to dead on for most paces.

0 Max556 over 8 years ago

I run mostly outside with GPS, but on the occasional cold, rainy day, I jump on the treadmill. Having logged hundreds of outdoor runs (just 5K each), my 5K treadmill runs are almost perfect! Only once did I have a run that was abit off, but I think I can explain that because I was holding onto the treadmill handles for quite a bit during that run (I was comparing the treadmill HR with my watch ... very similar btw)

So, yeah, I think getting some runs outside does help treadmill accuracy a lot!

Max