How accurate are heart rate monitors?

[FunkyNige]

Question's in the title really, the reason I ask is I bought one to see if I'm progressing much when running/cycling and I'm getting some odd results. Within 5 mins my heart rate's well over 200 (just got back and apparently my max was 236 but I didn't feel that knackered really and wasn't pushing as hard as I could've been) it then settles down to 160, slowly increasing to the high 180 mark.

Is this normal?

[swansea v6]

236??? no way!! was this reading from a Cv machine with built in heart monitor? or from a chest strap with watch??

[TheTardis]

Check that the chest strap is tight enough and does not slip down, even a small amount can cause misreading.
Also make sure you moisten the pick ups on the inside of the strap. When I've been out on the bike, sometimes the readings can go bonkers near overhead powerlines,etc but will quickly go back to normal. Either that or you're about to die suddenly?
Hope that helps
Chris

[Kylie]

Sadly if your training in suburbs it will spike because of overhead powerlines, fken pain in the arse. To rule this out set up the trainer at home or a treadmill and keep and eye out for spikes.

Theres nothing that makes me more grumpy after running 10kms all is sweet and a massive spike, totally fks up the whole analysis. Grrrrrrr. Polar monitors are great and I have a top of the line Nike which measures distance form a foot pod and chest strap. Best invention ever.

Those monitors on gym equipment are complete rubbish.

[FunkyNige]

Cheers for the replies, it's a chest strap/watch one. I do mositen it a bit before putting it on, but maybe as I start sweating it makes a better connection and gives a better reading?
No danger of outside interference (expect maybe my mp3 player) as I'm in deepest darkest Norfolk. Having said that, 236 was on the bike with a wireless computer so maybe that was messing it up a bit for a while.

[ewenm]

I find mine usually takes a while to settle down. For the first 5 minutes or so the readings tend to be high (170+ at warmup pace). Other wireless kit will definitely interfere. I've seen some very strange readings when two friends' Polars interfered with each other, rates of 300+!