Here's an informative piece about the question of target heart rate, fat-burning zone, and so forth. If you have wondered about these topics, give it a look.
http://www.msnbc.msn.com/id/22710441/
I usually exercise right at the top of the "fat burning zone," myself. Sounds like I could go a bit over into the cardio zone and still be doing good--as long as I can talk while doing it!
Jay
