Darcy...I've been perusing the Garmin forums for the past 2 days. I've found several threads discussing the "low calorie burn" issue, but haven't really come across a solution for it. So...my plan of action is to test the unit against my own pulse rate before I ride, and then change the battery in the HR strap to see if that helps. I've only had it for a little over a month, so I'm guessing it's not a low battery issue...but for $5, I'll give it a shot. I'm also going to buy a bottle of HR gel to use on the contacts. I'm fairly certain that my bra is not the cause, because I position the HR strap underneath the bottom band of my bra and it generally doesn't budge at all. IF, after all these attempts, I'm still not getting any love...then I will contact Garmin about getting a replacement strap...maybe I got a bum one.