@Walloon:
Ok, so you are basing the cardio range on what the machine is telling you. The problem is that the formula used by those machines, simply based on age and weight, are horribly inaccurate. They’re trying to use a one-size-fits all approach - and I’ll bet that if you look at the people in the gym (assuming you use the elliptical machine at the gym) - you know that one size does not fit all.
There is no way I can prove it, but I also believe that the manufacturers must legally base their zones on the lowest common denominator for health - ie, the 2 pack a day smoker who is 200 lb overweight, and who decides on January 1 that they are going to get fit, and they join a gym. For that person - starting training right away and reaching anywhere close to their true HR max could be deadly. Then there is a lawsuit that follows, where the prosecution says that the now-deceased family member was just following the training zones provided on the machine - shouldn’t they be safe?
Anyhow - more scientifically, Here is a cite from Perdue North Central University where they discuss all kinds of factors in HR training. It discusses how the 220-age (which the machines use to create that graph and those zones you mention) are very inaccurate - but commonly used because it at least gets you in the ballpark for HRmax (note the author indicates specifically that its useful for determining HRmax only). He also goes on to say that for determining the zones, he prefers the Karvonen formula (cited above in a previous post).
RE: aerobic and anaerobic zones - here are some excerpts from Galloways Book on Running. Unfortanately since its in book form, I cannot give a link, but I can give page numbers I am finding the information in (ISBN number 978-0-936070-27-8) if you want to cross reference/verify on your own. Also - while this book is centered on running - the concept is essentially the same regardless of activity.
Page 27 (the bold is my calling out of an important indicator when you are crossing into anaerobic territory):
Aerobic means “in the presence of oxygen.” You are running aerobically when you run slowly and comfortably and do not exceed the pace or distance for which you have recently trained. Here your muscles are strong enough to carry the load and there is enough oxygen available from the blood stream. The few waste products that are produced are easily whisked away in the blood before building up and obstructing muscle function.
anaerobic running is when you exceed the speed and/or distance for which you have trained. The muscles are pushed beyond their capacity and need more oxygen than the body can supply. For a limited period of time, muscles continue to function by utilizing checmical processes that free oxygen from within the muscle itself. The aount of oxygen available this way is quite limited, large amounts of waste build up, and the muscles get tight and sore. You find yourself hugging and puffing and slowing down.
My whole point in this case is not specifically what is meant by the term ‘fat burning’ and ‘cardio’, because those are just labels. Incredibly and very oversimplified labels. Rather, my point is to demonstrate that its more complicated, because its person-specific.
I’d bet that if you used the Karvonen formula (referenced in the Perdue cite) and recalculated your zones based on that - you’d find your HR zones (60-70%, 70-80%, etc) FAR higher than the graph thingie on the machine shows.
And yes, you are right - weight loss occurs no matter where you are in the range. Afterall, you are exerting effort and calories are being burned. The whole thing with the ‘fat burning’ zone is that it is a way of saying ‘the majority of calories used in this zone are from fat’.
