Charge 4 Heartrate not picking up at higher heart rate levels.

[SeirinNo7]

I walk along a regular route which includes a steep hill where I can feel my heart beating faster. On hotter days, I need to stop before the top sometimes. I've noticed at those times my tracker will say my heart rate is only 99-104 or so despite being around 120+ a few steps after the crest when I start feeling things getting easier again. 

When I do stop to sit down on swletering days, however, I see it spikes up to the expected higher 140-150 zones. But only until I start walking upwards again. On the attached picture you can see where I stopped and when the reading spiked to a correct reading, and the incline on which I'd expect to see the build up. 

Imgur link to heart rate and elevation charts 

I've tried wearing it more lightly as well as more loosely. Any suggestions? It seems to do well enough picking up the difference between jogging and walking on relatively flat terrain. 

[SebWotan]

Hello @SeirinNo7 

Does it happen consistently, anytime you walk this hill ? Or just a few times ?

[SeirinNo7]

Any time on this particular hill. But today I did some heavy outdoor yardwork and it picked up I think pretty accurately in the 140 range. This hill is one of my daily defaults so it's a shame if it won't pick that up regularly.

[SebWotan]

This is a bit bizarre, I admit. 

Maybe borrow another fitness monitor next time you do the walk on that hill and see if they pick up your HR accurately ? 

[SeirinNo7]

Another interesting quirk; if I change my workout type from 'walking' to 'outdoor workout' it seems to pick up much more accurately. I wonder if putting it in exercise mode for walking it assumes that getting into the upper cardio zones must be impossible and docks it down? I'll try on a flatter route tomorrow and throw in some jogging to see what it does at higher levels when in walk mode. 

This is odd to me as when I don't put it in any particular exercise mode at all, it usually picks it up on its own accurately, such as the afforementioned yard work.