afterburn

Um, what? Who Where? Someone called me?

Oh, ok, I just read through the whole thing. Um AWTY, first, if you REAAAAAALLLYYY want to know your maximum heart rate, pop by the doctor, they should be able to put you on their machine and test you. the 220 - age thing is just a very rough estimate assuming you are average in just about every way. So it's a guideline, not a rule.

For example: my wife is 37 and wears an HRM, it tells her, for instance, during spinning that she's averaging 92% MHR (Max Heart Rate) for the hour class, which she obviously isn't or she would collapse dead . What it's telling her is that she is working at what WOULD be her max heart rate if she were an average athlete with utterly average body function. She isn't so it's wrong, but if you weren't knowledgeable about this stuff, that could be a scarey number to see.


As to the fat burning zone thing. Ugh, I hate that term. But anyway. It's a ramp up process, as we work at a higher and higher heart rate, the body requires more and more energy faster and faster. Unfortunately, stored fat cannot be delivered to muscles fast enough, nor can it be converted to glycogen fast enough to re-supply our muscles when they are at the anaerobic threshold (for most that means about 82 to 88% of Max Heart Rate ).

So as we ramp up exercise and the heart rate approaches the anaerobic threshold , the percentage of energy for those muscles coming from stored glycogen goes up and up, and when the muscles run out of glycogen (called technical failure), we are unable to work for about 30 seconds to 1 minute. You know what I mean, the point where you just can't lift that bench press bar up one more time, or when you just can't do that one more pull up, that's technical failure.

What does all this have to do with fat % burned? Well, at lower levels, the body doesn't need AS MUCH energy, so it deems itself capable of converting stored fat to energy fast enough, so it uses more fat. At higher levels, the body deems itself not able to replenish energy with fat stores, so it opens up the "flood gates" of glycogen, which means less fat used.

Why I think this is a flawed and outdated notion though, isn't because of the above paragraph, it's what happens after. When the energy is depleted, it needs to be recovered, somehow. Part of that will be from the food we have eaten, but part will come from stored fat as well, so while during the exercise, we burn a higher fat % at lower levels; at higher levels, where we approach anaerobic activity, the body needs hours post exercise to replenish it's stored glycogen levels, which means a raised metabolic rate at that time (heat and hormones are needed to break down fat to glucose).

The added benefit to higher intensity activity is increased health. When we work our body close to or to failure, the body compensates by adding muscle, and lung capacity (among other things), thus allowing us to work in that higher zone for longer periods, and burn more calories for longer periods.
The downfall of higher intensity is the possibility for injury or other health problems.

Side note, this is why people who have never worked out or are really obese and work out lightly still see massive body changes in the beginning. Because when you are at that level, almost ANY workout is anaerobic, and the body reacts the same way it would if you were in good shape and working out at a very intense level. Sadly it doesn't stay this way, as our muscles develop, we need to do harder and harder work to get them to the "next level".