Hey everyone, quick question. I am a runner, run about 4 times per week anywhere from 5K to 8 or so miles each day. I wear my heart rate monitor each run and I am always in zone 4. I know this zone burns carbs and very little fat. I'm not overweight, about 109 lbs. 5'2". But I'd like to spend a little more time in the 3rd , fat burning zone without compromising my time. I can't seem to figure out how to do it. Is it okay to always run in zone 4 oreven 5? When I see my heart rate monitor going to the 5th zone I only stay there for a few minutes and back off to bring heart rate down. I'm a little confused on the whole "zone" thing. Any help is appreciated.