FR935 with a treadmill

How do you know the distance displayed by your treadmill is correct?

It will only ever work properly with some form of foot pod. Interpreting arm movement to guess running pace is not an exact science.

However, does it really matter? You are on a treadmill, the distance you have covered is zero. The only thing that matters as far as training input is concerned is the duration and the intensity.

Do a quick search for 'treadmill' and 'calibration' here on the forum and you'll see that this very subject has been discussed many tines in the past.

To answer your last question. Yes it is possible to have that information direct from the treadmill. You'll either need a treadmill with that functionality built in, or something like the NPE RUNN

Thanks - I've found a fancy dongle called NPE GEM Retro - it connects to the CSAFE port of the treadmill and transmits workout data via ANT+ and BT. If NPE RUNN does it, then this GEM should do as well. 

Well, distance and speed matters for me, as I would like to refer my treadmill workouts to the real ones outside. I think, that the treadmill shows more or less real values - it knows how fast the engine rolls and how fast the belt is moving. 

CloggyAbroad said:

To answer your last question. Yes it is possible to have that information direct from the treadmill. You'll either need a treadmill with that functionality built in, or something like the NPE RUNN

Are you sure it will work like that? I've contacted NPE, and they say, that it is based on ANT+ FE profile which is no more supported nowadays.

I use my 935 with the Garmin footpod and a Nordictrack C2950 treadmill several times per week.  With the right calibration value I get distances on my 935 that are within 2-3% of the treadmill value.  Note that the calibration does vary a bit between slower paces and faster ones so I choose a value that works on average. 

Yes, RUNN is able to mock footpod, but GEM doesn't, according to NPE:

"We have thought about adding support for the footpad ANT+ profile but the radio chipset used in the GEM RETRO has very little room for additional services to support."

Nevertheless, it's strange, that Garmin decided not to continue support for ANT FE-C profile. It was intended to provide communication between sport watches and fitness equipment. 

But there's workaround - GEM is able to send data over BT to Zwift, which will transmit workout to Garmin Connect. 

If you can get it connected to your 935 the GEM will make sure that the 'distance' and 'pace' on your watch match the 'distance' and 'pace' on your treadmill, because both come from the same source. The GEM just transmits what the treadmill thinks it is doing in terms of speed and distance, but there is no way of knowing if the information is correct. However, you'll be happy because the two are the same. The reality is that you still don't know 'far' you ran.

FE-C was meant to be a two way thing, so for instance your device would be able to control the speed and incline of your treadmill. As the control side of things was never really implemented by any gym equipment manufacturers there is no real reason why Garmin would put a lot of effort in supporting the protocol.

The thing is, that I will not connect this dongle to my 935, as it supports only FE-C. But it doesn't matter - as I will be able to record my workout using Zwift or Strava, I'm home. 

Control side is implemented, my treadmill supports both incline and speed control by means of CSAFE protocol - it's kind of surprising that it is widely used in case of bike trainers, and abandoned in cased of treadmills. Garmin doesn't need to put any big effort - their wearables from 2000s supported it pretty well - it was possible to connect early forerunners to FE-C supported gym equipment, including treadmills. 

Regarding treadmill's accuracy - how accurate it is depends on the treadmill's mechanics - its quality and condition. Number of revolution of the belt determines distance without any doubt. Inaccuracies appear when the belt is not revolving as expected, when it slides, stops, or the engine is not capable to sustain given revs constantly. I've got top of the line Precor C966i with only forty hours in operation, so I believe, that non of the above could happen, and yes - I'm rather confident that it shows actual distance. Whether this distance reflects the same outdoors is totally different story.

I've found that the only accurate way to record treadmill running is with Stryd

just for info, i've reached a 2% accuracy with Runscribe linked with 935 as an ANT+ footpod. i've calibrated my treadmill while running on it in the "classic" way (measured lenght, set a mark, get more or less 40 crono laps while running, get a disappointing -6% between real speed and display speed...), then set a proper calibration factor into Runscribe. i'm getting full Runscribe analisys + real time parameters + pace/distance into 935