Heart Rate

Have any of you guys ever worn a heart rate monitor while riding? I've been messing around with mine and the results are very surprising. I had it on while riding tonight, Click Here to view some of my results. (make sure you're in the "graph" tab) The first 3:20ish minutes is the sight lap, but after that you can pretty much see my lap times. :lol: I'm trying to figure out which section causes the dip, but there isn't really any "slow" areas.

But damn, at that rate I'm burning around 1,000 calories/hour.
I bouhgt a Heart rate monitor so I could do this this spring. Just to see what happens. I will probably have a heart attack oh well. Least I'll go out doing what I love.