QUOTE (sheila_waters @ Jan 3 2007, 08:17 PM)

Hi. I am a newbee. I have 75+ pounds I want to lose. I have started working out on a new eliptical training machine at my local Y. It has a cardio mode and a fat burning mode. They both measure my heart rate and adjust tention to keep it at a particular level. Question: If the cardio mode wants me to work out at a highter heart rate and the fat burn mode wants me to work out at a lower heart rate, which one is better for me? What is the difference between the two?
To answer your questions;
"If the cardio mode wants me to work out at a highter heart rate and the fat burn mode wants me to work out at a lower heart rate, which one is better for me?"
Both
one day you will work in cardio mode, the next fat burning. Alternate your workouts to get the best benefit.
"What is the difference between the two?"
The difference between the two is how they condition your body. The cardio mode gets your heart rate up to where you can answer someone if they ask you a question but you really don't want to (a good way to gauge it if you don't have a heart rate monitor). This increases what is called your cardio threshhold. You should feel spent after this work out. It basically conditions your lungs to be able to work at a higher heart rate when needed so you can get enough oxygen and makes you faster as a result. The fat burning mode should put your heart rate at a level where you are able to speak in full sentences but it is a little labored. After a fat burning session you should feel like you could do it again immediately, but you really don't want to. The fat burning zone allows you to raise your heart rates just enough to burn fat but not have it be so labored that your body holds on to the fat to use as stored energy. If you stay anaerobic (85% or higher of your heart rate max) that is basically part of what happens (ozzie explains it really well).
Wanting to lose 75lbs, you really want to use both modes. (It will help your body recover on the fat burning days. Going at it full force every day will increase your risk of an injury. You need recovery time and being in the fat burning zone does that. You get to recover and burn fat at the same time.)
I agree with Loou. You may want to put it in a manual mode. While in that mode, try doing a "ladder". It is actually my favorite workout:-) ;warm up for 5 min, then go like crazy for 2min, recover your heart rate within a minute, then go like heck for 3 min.,recover for one, then go like heck for 4, recover 1, glh for 5, recover 1, glh for 6,then come back down the ladder by recovering for 1, glh for 5, recover 1, glh for 4, recover 1, glh for 3, recover 1, glh for 2 recover 5. It is about an hour workout and it goes super fast when you have good music blasting in your ears. That's the cardio workout. The fat burning zone one is a little boring because you try to maintain a 70 - 80% max heart rate (60 - 70% for some) without going under or above. It takes more patience and doesn't give you the anaerobic high but it will burn the fat so stick with it.
I hope this answers your questions.
Have fun!