Annoying issue with Polar S720i and running on treadmill

[Speed_Metal]

i usually use this HRM on the bike, but when i cant ride i like to run on the treadmill.
the following issue has only just cropped up fairly recently
i'll first get a steady reading on the s720, then start out at a walking pace.
then when i start running, the heart rate reading goes completely haywire.
the pulse icon will be totally inconsistent, and the number readout will "stick" at one rate for a long time.
then i'll start walking again, and everything goes back to normal. normal pulse icon. normal number reading.
i'm wondering if the chest strap is moving around too much when i start running, and creating its own interference?
i could try a new battery in the chest strap, but i put in a new one earlier this year. and i don't know why a stale battery would work when walking, and not work when running.

this didn't start happening up until about a month ago or so.

does anybody know what could be the cause?

[vetboy]

I haven't used mine in some time, but I never had any issues like you describe. I would try a new battery first - HR monitors do weird things when batteries are low (try new batteries in both watch and HR transmitter). Also worth investigating the location of the treadmill - perhaps there is some interference coming from something.

[bq_or_bust]

+1 on new battery. when the charge is low, battery doesn't really work.

i have another polar product and started getting weird readings as the battery was dying, but, NOT DEAD.

IMPORTANT
a NEW battery does NOT mean it is @ FULL CAPACITY.

here's an example with a motorcycle battery:
. it's a 12.0 volt
. if it registers 12.4 volts, it is considered DEAD
. the battery NEEDS to maintain at LEAST 12.8 volts by itself for some time to be consider GOOD.

double check your battery as well as the replacement !

[Sean.B]

I have an FT7, the treadmill itself has some kind of signal for HRM's. My watch doesnt act crazy but the display on the treadmill will say my HR is at 227-230 when its only at 100-110 during the walking I do. I havent figured a solution out yet.

[Speed_Metal]

i had the watch battery replaced this past summer.
i'll try a new batter in the transmitter.

[Akirasho]

... outside interference?

I've got a 710 and so far, no unexpected issues, but I know that the bandwidth landscape has changed dramatically since these monitors first hit the marketplace (from digital TV to 4G networks to the dog's lost and found chip).

Also, it might not hurt to use an electrolytic contact gel/lotion to ensure the best possible conductivity (sweat is generally good, but depending on contact, might not be enuff).