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Doug_Meyer
01-10-2016, 07:34 PM
Hi community,
I was wondering if anyone else has been seeing any issues with abnormally low heart rate sensing during cold weather activity? I have owned my 235 since late December 2015 and have had two activities where the heart rate was abnormally low for the corresponding physical exertion. Anecdotally, these activities were both instances where the watch was "cold soaked" for a period of time before starting the activity. One was on a hike, and the other was a trail race this past weekend where we were waiting at the starting line. Data here: https://connect.garmin.com/modern/activity/1008817642

It seems like in these cases, the optical HR monitor resides in a very low BPM and then all of a sudden spikes up to the actual HR. This occurred on the aforementioned run at about the 28 minute mark while going downhill (usually a regime where your HR is not massively rocketing upwards). Maybe this is the point where my arm warmed the sensor enough to coax it into working again? Anyways, I expect the HR should have been in the 160s/170s the entire race.

I remember hearing on the DCRainmaker website (or podcast) that many optical heart rate monitors have issues with cold weather.

Does anyone know the reason behind these cold weather inaccuracies, and does anyone have any tips on how to prevent this anomaly? BTW, my watch was exposed to the air, but the temperature was only approximately 52F / 11C, so not really THAT cold. Also, I made sure that the watch was very snug on my arm prior to the start. I've run in 20F / -7C temperatures starting from my house (non cold soaked) where I have had absolutely no problems.

Thanks,
Doug

P.S. If you haven't tried out the LiveTrack feature yet on the Connect App, it worked like a champ! My friends and family had a blast watching the race in real-time. Try it out some time!

WEPRERUNNER
01-11-2016, 01:55 AM
I believe it's something to do with the blood flow to the hands being less in cold weather (hence why my hands are always freezing!)

gpb11
01-11-2016, 08:50 AM
Yes, I've heard the same thing about optical HRMs in the cold and it being related to blood flow. I've also heard that wearing gloves can help, presumably keeping the hands warm helps?

My experience in 30s/40s/low-50s (F) is that I've not seen a low HR reading; however I'm adding sleeves and running gloves at least for the first part of runs when its in the 30's and 40's until I've warmed up.

R_Tellis
01-11-2016, 11:57 AM
The first time I experienced trouble with oHRM in the cold was with my 225. The temp was decent when I started so I went with a sleeveless shirt but once the sun went down my arms got cold and it kind of made up it's own numbers that were somewhere between my expected HR and my cadence.

Doug_Meyer
01-12-2016, 12:22 PM
Unfortunately, I was already wearing gloves and a jacket. The watch was the only exposed portion of my arm (so that I could monitor pace / distance as the race went on). I can live with some inaccurate readings on these rare circumstances like this. I just really enjoy not having to put on my heart rate strap (which has it's own issues in cold weather too btw).

Thanks to everyone that responded!

vhFlores
01-13-2016, 07:16 PM
https://connect.garmin.com/modern/activity/1014116890


It told me i started on zone 6, and just went from there. 6.1, 6.2 . . (i was getting scared)
then it dropped. -i stopped before climbing the bridge waiting for the light, and I let the HRM drop.
It is a pretty steep climb, and i did not want to see the thing registering over 200, when my max is supposedly 185-



the altitude is not accurate either- going over the bridge, i swear thats gotta be at least 100 feet up in the air.

I left a portion of my wrist exposed- folding the glove and the sleeve, so i could see the watch...BIG MISTAKE
The wind chill was brutal. 40 minutes later, my left hand was in pain (frostbyte? not quite), and my right hand
was completely normal

R_Tellis
01-14-2016, 05:31 AM
https://connect.garmin.com/modern/activity/1014116890


It told me i started on zone 6, and just went from there. 6.1, 6.2 . . (i was getting scared)
then it dropped. -i stopped before climbing the bridge waiting for the light, and I let the HRM drop.
It is a pretty steep climb, and i did not want to see the thing registering over 200, when my max is supposedly 185-



the altitude is not accurate either- going over the bridge, i swear thats gotta be at least 100 feet up in the air.

I left a portion of my wrist exposed- folding the glove and the sleeve, so i could see the watch...BIG MISTAKE
The wind chill was brutal. 40 minutes later, my left hand was in pain (frostbyte? not quite), and my right hand
was completely normal

You need to make the run viewable to others before we can see it. Click on the lock icon in the upper right corner and select "everyone" and we'll be able to see it.

As far as the elevation goes. This watch doesn't have an altimeter so when the run is uploaded Garmin Connect will look at the GPS trace and apply GIS data to get the elevation info so bridges will end showing the terrain of that the bridge is going over.

You can however go to the area where it shows the watch on the right of your screen in Connect and disable "Elevation Correction" and it will show the GPS elevation instead which will give you a better idea of what the climb on the bridge was like.

vhFlores
01-14-2016, 06:31 AM
did it- i also disabled elev correction, but it looks the same- elev 25 ft over bridge

i know this cant be, as i can see boats going under the bridge as i am running . . . . way down under.
So the GPS info is not accurate either. Not much can be done.

gpb11
01-14-2016, 06:54 AM
i did not want to see the thing registering over 200, when my max is supposedly 185

There is no "supposedly" -- any formula you calculate just tells you the average for your age/gender/etc. Your personal maxHR is based on your individual genetics and the only way to reliably find it involves sweating a bunch.

Think it through: You don't use a formula to find your pants inseam, or your jacket size, or your shoe size, or your weight, you measure those. Maximum HR is different for everyone and VERY easily can be far above or below the "average" number the formulas spit out. Sure, use the formula to get in the ballpark, but you need to actually measure your heartrate at/near maximum effort to figure out your own maxHR.

See here for more info: http://www.howtobefit.com/determine-maximum-heart-rate.htm

Looking at your track it seems you experienced a bad case of "cadence lock" for the first part of the run, where the watch was picking up your running cadence instead of your heartrate. This is a known issue currently, and it seems to affect different people to different degrees. I've never seen it more than momentarily, others have seen bad instances like yours. We (the people on this user-to-user forum) believe Garmin is actively working on the matter.

As to elevation; while GPS does provide elevation data it is notoriously less accurate than horizontal location data. Especially so when running in an environment with a lot of tall buildings around. This is true for any GPS, it's a matter of the physics of how GPS works. For this reason most sports devices have the option of correcting their tracks on their respective web service using GIS elevation data. Your track doesn't have this correction enabled; click on "Disabled" next to Elec Corrections under the picture of your watch and switch it to "Enabled".

For more info see:
http://gpsinformation.net/main/altitude.htm
http://www.dcrainmaker.com/2010/05/understanding-sport-device-gps.html

R_Tellis
01-14-2016, 07:31 AM
did it- i also disabled elev correction, but it looks the same- elev 25 ft over bridge

i know this cant be, as i can see boats going under the bridge as i am running . . . . way down under.
So the GPS info is not accurate either. Not much can be done.

That's odd how it still shows 0 elevation with the elevation correction turned off. I do a half marathon every fall that goes across the Woodrow Wilson bridge and corrected elevation will show as if I ran across the river but when I turn it off it'll show a rough approximation of the elevation of the bridge.

The high HR at the start could be a cadence lock like gb11 said, or it could also just be that it couldn't get a good lock until you got warmed up a bit and got the blood flowing. That happens to be from time to time on colder weather runs.

R_Tellis
01-14-2016, 07:33 AM
Your track doesn't have this correction enabled; click on "Disabled" next to Elec Corrections under the picture of your watch and switch it to "Enabled".


I told him to turn the elevation correction off to see if that would give an idea of the elevation of the bridge.;)

gpb11
01-14-2016, 07:49 AM
Yeah, apparently I missed that.

I wonder if the GIS dataset being used included bridges or just includes the surface info? It would seem the latter based on this.

R_Tellis
01-14-2016, 09:11 AM
Yeah, apparently I missed that.

I wonder if the GIS dataset being used included bridges or just includes the surface info? It would seem the latter based on this.

Weird.

I just went to a run that goes over the Wilson bridge and it still had elevation correction disabled from when I was playing with this feature awhile back and it showed properly on the graph with an elevation gain of 417'. I enabled the correction and it showed flat on the graph and 62' elevation gain as I expected, but when I turned the correction off again the elevation gain went back to 417' but the graph stayed flat.

I went back to the other users linked run and with elevation disabled it's showing an elevation gain of 1988' so I wonder if that will change if they turned it back on but still left a graph showing flat terrain.

Doug_Meyer
01-15-2016, 12:40 PM
There is no "supposedly" -- any formula you calculate just tells you the average for your age/gender/etc. Your personal maxHR is based on your individual genetics and the only way to reliably find it involves sweating a bunch.

Think it through: You don't use a formula to find your pants inseam, or your jacket size, or your shoe size, or your weight, you measure those. Maximum HR is different for everyone and VERY easily can be far above or below the "average" number the formulas spit out. Sure, use the formula to get in the ballpark, but you need to actually measure your heartrate at/near maximum effort to figure out your own maxHR.

See here for more info: http://www.howtobefit.com/determine-maximum-heart-rate.htm

Looking at your track it seems you experienced a bad case of "cadence lock" for the first part of the run, where the watch was picking up your running cadence instead of your heartrate. This is a known issue currently, and it seems to affect different people to different degrees. I've never seen it more than momentarily, others have seen bad instances like yours. We (the people on this user-to-user forum) believe Garmin is actively working on the matter.



Agreed about the cadence lock. Here is a screen shot of two heart rates from the same run last night:

31678

I was doing a maxHR test. Warm-up of 1.75 miles followed by 3 minutes as hard as I could run on a track, two minute jog, 3 more minutes as hard as I could run, then a cool-down. As you can see, the blue line (FR410 w/HRM-3 chest strap) clearly has issues at first with finding my HR. It spikes like crazy during the easy warm-up before settling down. The orange line (FR235 oHRM) is working great until after the first 3 minute interval. Then it cadence locks for the rest of the run. When viewing in GC, the cadence and oHRM numbers are virtually identical! BTW, I don't trust the heart rate strap either because there is no way my max HR is 165 for my age (35). Maybe I wasn't running as hard as I could, maybe it's because I'm coming off an illness... but when both a chest strap and an optical HR method seem completely out to lunch, it makes it extraordinarily difficult to find your MAX HR. I guess I just go with the old formula method and accept the potentially inaccurate HR zones and calorie burns. Unless Garmin can find a firmware solution...

gxceb0tty
01-15-2016, 01:07 PM
Or just try it again. I have occasional problems with the ohr and the strap, but not all the time. In any case, what is the max hr you have observed prior to this?

gpb11
01-15-2016, 01:26 PM
when both a chest strap and an optical HR method seem completely out to lunch, it makes it extraordinarily difficult to find your MAX HR
I'm venturing off into speculation a bit so take my words with a grain of salt...

Outside of a medical/sports-lab treadmill test, I don't think most of us mortals ever experience our real maxHR. Fatigue, training, mental fatigue, etc. all get in the way. Particularly the subconscious "I'm not home so I'm going to hold back some" aspect.

What we can do is over time refine an approximation of our maxHR. Do a test like you did to get a ballpark idea and add a few BPM. Monitor your performance in 5K and 4M races and adjust. Do some hill tests sometime when you're well rested and adjust. End up with a number that seems to work for you; even though it's an educated approximation it's still way better than subtracting your age from 220. It's an ongoing process; I look at race results and see if I'm still happy with the estimate.

BTW, here's how bogus 220-age can be. I've run 5K races where my average HR was higher than what 220-age would say is my max. :cool:

Oh also, as to calorie counts: IMHO unless you're wearing a mask connected to a machine measuring O2 input and CO2 output, it's all a bunch of estimates on top of averages on top of guesses. I'm just happy if I get consistent figures that relate well across different workouts. Whether the watch says 500kcal and I really burned 400 or 600 doesn't really matter, I'm in the ballpark. Again, JMHO.

Doug_Meyer
01-15-2016, 01:50 PM
Haha. Ok. I get it. I need more data and time to get a good ballpark Max HR. Point taken. I've only been running for about 3 years, but this is something I've never put much thought into until recently, so I'll probably be paying more attention to this now.

In general, I guess I'm just getting a little impatient with the myriad issues having now experienced the oHRM failure to initially perform in cold weather, the failure of cadence lock, and on a previous run, the failure of the GPS + GLONASS to continue to record data while all other sensors continued to record: https://forums.garmin.com/showthread.php?339226-GPS-GLONASS-trail-stopped-recording-in-middle-of-a-run-all-other-stats-recorded

Waiting on that magic firmware unicorn to soar in and sprinkle rainbow dust on all of the outstanding software/firmware issues ;)

FraderT
01-18-2016, 10:33 PM
I'm having the same problem in cold weather. I used the watch on some runs in the 70s and 80s and the heart rate sensor seemed to be just as good as my old TomTom Cardio Runner. Below 50F, though, and the 235 seems to read consistently low. Doesn't seem to matter whether it's in the 40s or 20s. I am not having any significant problems with cadence lockmy readings tend to get stuck somewhere around 120-130 when I'm expecting 140-160 (depending on pace/workout).

I hope this improves soon. Would be great to get some commentary from Garmin's engineering/product management teams. Transparency is a good thing.

ascii256
01-19-2016, 08:07 AM
I had a 6 mile tempo run last week while vacationing in Dallas, my heart rate read approx. 115 the whole time. I had planned on running on the hotel treadmill (called ahead and confirmed it was working) but found it slipped and was in disrepair. So I wasn't dressed for low 30s but ran outdoors anyway. I tried warming my wrist, doing hand exercises, even ran for a but with my wrist under my arm pit. Nothing seemed to resolve the problem.

Ran a long run out-doors (upper 20s) last Saturday. This time things started in the 115s again, it locked only my cadence at around 174, and then finally found my pulse for the remainder of the run.

Agepi7o
01-20-2016, 06:09 AM
I'm having the same problem in cold weather. I used the watch on some runs in the 70s and 80s and the heart rate sensor seemed to be just as good as my old TomTom Cardio Runner. Below 50F, though, and the 235 seems to read consistently low. Doesn't seem to matter whether it's in the 40s or 20s. I am not having any significant problems with cadence lockmy readings tend to get stuck somewhere around 120-130 when I'm expecting 140-160 (depending on pace/workout).

I hope this improves soon. Would be great to get some commentary from Garmin's engineering/product management teams. Transparency is a good thing.


Im experiencing this issue as well and its kind of annoying. Yesterday I was doing fast intervals with great effort (probably my HR was 170-175) and my forerunner read 140-145 (sometimes even 150bpm). It was cold (around freezing because there was ice and it was before sunrise) but I had my arm covered with 2 layers and gloves.

Its disappointing because sometimes I hold back some extra effort not only by feelings; I use my sensations plus the HR to try harder or not. I d like to know how can I fix it.

Heres my run
https://connect.garmin.com/modern/activity/1020103945

Doug_Meyer
01-20-2016, 07:37 AM
Agepi7o,
gpb11 posted these articles in a different thread on this forum. I found them to be extremely helpful in understanding the current engineering challenges associated with oHRM. Hopefully there can be some algorithmic software solutions from the Garmin engineers in the not too distant future, but until then, it seems that there are pretty strict limitations to what we can affect as end users of the product (sensor placement, reduction in ambient noise, etc).

http://www.edn.com/electronics-blogs/embedded-insights/4440217/Optical-heart-rate-measurement-s-top-5-challenges
http://www.valencell.com/blog/2015/1...-you-need-know

P_W_P
01-20-2016, 05:23 PM
Thanks for those article pointers.

The Electronic Design News link didn't work for me, but I found the article here (http://www.edn.com/electronics-blogs/embedded-insights/4440217/Optical-heart-rate-measurement-s-top-5-challenges).

Doug_Meyer
01-20-2016, 07:26 PM
Sorry,
I think I must have deleted the last post when I was trying to fix the broken links. The below articles shed some light on the inherent challenges with our physiology, current technology, and what might be corrected by Garmin via new algorithms.

Again, thanks to gpb11 for the links (in a different thread):

http://www.valencell.com/blog/2015/10/optical-heart-rate-monitoring-what-you-need-know

http://www.edn.com/electronics-blogs/embedded-insights/4440217/Optical-heart-rate-measurement-s-top-5-challenges