This is a follow-on to the BMI/Body Fat % thread from a few days ago: Today as an experiment, I ran for one hour (like always) instead of striving for a 9-minute mile pace, I only ran based on my heart rate. I tried to keep my heartrate at 135-140 instead of 170-180. Amazingly, I can breathe a lot better at the slower pace! [/duh] I started off at a 13.5 minute pace, but had to keep cutting it down until it was something in excess of 15 min/miles. The low-end of the Fat Burning scale on the treadmill is 111 for my age, and the high end of the Cardio Scale is 152....so I tried to stay as close to the middle of that range at possible. An interesting surprise was that I was just as drenched with sweat as I usually am at the "fast" pace of 9 min/mile, even though my breathing was quite relaxed and the pace was downright snail-like. I'm not sure if I'm going to get more benefit this way, given that I am limited to 1-hour on the treadmill regardless of pace..... but I figure I'll try it for a couple of weeks and see what happens.