Garmin's new "premium" HR straps are notorious for poor performance. If that's the one you have, I'd read some of the user forums for tips, and/or replace it with the old-style hard strap. It's not as comfortable, but if it works consistently and the elastic doesn't wear out within a few months ... I'll take a little bit of chafing on runs over 20 miles. (There's also a shorter elastic strap available for the old-style strap.)
If you're using it exclusively on the bike, one of the things they suggest is to try putting the electrodes on your back. Sometimes between gravity and the curve of your spine, a cyclist's posture can force the HR strap away from your body.
I use aloe vera gel on the electrodes - cheaper and easier to get than real electrode gel. If you go that way, just make sure you use 100% aloe without added oils or emollients that can interfere with reception.
Bra bands can push the HR strap crooked, too. That might be another reason to put the electrodes on your back where everything's flatter and there's more room to operate. I don't suppose it's as easy for you as it is for small-busted me to find a bra where the transmitter just tucks up in between, above the band.
Last edited by OakLeaf; 03-23-2011 at 05:30 PM.
Speed comes from what you put behind you. - Judi Ketteler