GG,
I tried replying to your pm, but this forum only allows about 1,000 characters (about 3 paragraphs) and I'm evidently incapable of being brief
If you sendme your email address I'll send my reply in whole.
Lemme take a shot at this topic, in simple terms:
For the most part your body uses 3 sources of energy:
1) Creatine-Phosphate/ATP
2) Glycogen
3) Fat
The simple fact is, when your body is active, it's using a COMBINATION of all 3 of these fuels....but the proportions vary based on demand. All too often people are consumed with the notion that we have a fuel-selector switch and we can, by manipulation, choose which fuel we wish to burn. Well, we can't quite select it, but to some extent we can facilitate and focus on trying to burn more of one then the other. And so the confusion begins....
The general consensus suggest that you will burn the greatest PROPORTION of fat when you are exerting yourself in a manner such that your heart-rate is at 80% maximum. This is determined by a simple forumula:
220 - (your age) x .80
Accordingly a person of 40 years would have a maximum heart rate of 180 and would be burning the greatest proportion of fat when their heart-rate is at 144. Heck, let's give that a range, call it 140-150.
So...if you don't wear a heart-rate monitor how else could you determine when you're within this range? Well...don't freak, modern-day scientist have brought us a swell way to figure this out. The Talk Test.
Let's say you're biking along with your buddy and you want to start discussing how fat Britney Spears tummy looked at that awards show...so as you bike along you start talking. If you are huffing & puffing so hard youcan barely get a word out, your probably well above the 140-150 range. On the other hand, if you can just talk like your sitting on the phone...then your probably well below the 140-150 range. When you are in the 140-150 range, you'd be able to talk but here and there you'd be breathing pretty heavy:
Did you see...huff huff.....on that show...huff....how she had....huff huff....her gut sticking out....huff huff...and it was...huff huff....
That's all it is. If you can carry-on a conversation with just mild to moderate difficulty, then you're probably in your ideal zone for maximizing the greatest proportion of fat being burned.
So....what if you push harder??? Well, the body can only oxidize/metabolize/burn fat at a slow rate, so you'd have to start dialing in more glycogen to the mix....and when a mountain lion or my sister-in-law show up, you'll go into fight/flight mode and you'll be all over your creatine-phosphate/ATP.
But now, just to ensure I get into my novel-length mode, let me go one step further and explain something that many trainers say "yes, thank you!" for explaining:
When you push past your "maximum fat burning proportion" zone....you don't burn less fat, you just start burning a greater proportion of other fuels. By the numbers.
All hypothetical...but as an analogy for understanding:
Let's say you are biking along at 145 HR (Heart Rate) and you're putting out 600 calories per hour. Of those 600 calories, let's say you're burning 35% Fat, 55% Glycogen and 10% Creatine-Phosphate/ATP. As fat goes, you're burning 210 calories per hour. (600 x 35%)
Now...let's kick it up a notch and bring the HR upto 165. Now you're putting out 850 calories per hour (forget taking a cell-phone call, you're all lungs!). Boom: the body NEEDS MORE ENERGY to fuel those muscles. New mixture: Fat 28%, Glycogen 58% and 14% creatine-phosphate/ATP.
Hmmmm.....let's examine this. Well, the percentage of fat being burned has DROPPED to 28%...whereas it was 35%, so you would think this is detrimental and you're no longer in your primo fat-burn zone? eh??? But wait, look at your calories per hour derived from fat: 850 x 28%....whereas you were burning 210 calories per hour, you are now burning 238 calories per hour from fat. An INCREASE in overall fat-calories burned despite the DECREASE in percentage.
So pushing harder/faster is not a bad thing, you'll still burn more calories and even derive other benefits as well. It's just one of these commonly misunderstood things. I think the basic notion is to workout at least hard enough to get some good fat burning...and you'll know you're at least getting some good value for your effort using the talk-test.
There are so many other variables; what you ate, when you ate, your age, condition, training, etc....but on the whole, this is the theory and I sincerely hope you found it understandable & readable.
