By the way PWG - this is incorrect.
"when u run u use the energy supply called "glycogen" instead of fat, and when you walk you burn both just so u know ;)"
if PWG is incorrect, what's the right fact? just curious
It can be a bit complex.
There are two basic energy systems - Aerobic and anaerobic
Aerobic is when the body is able to meet the demand for oxygen, such as when you run at low intensities, walk, or do other repetitive movements..and even when you sit in a chair. The Aerobic energy system will use fat
and/or glycogen for energy.
Anaerobic is when the body can no longer meet the demand for energy, such as a set of curls to momentary muscle failure. The anaerobic energy system relies upon glycogen.
Basically, the closer to the lactate threshold (the point where you feel it burns too much and you eventually have to stop) you train the more you rely upon glycogen for energy. Think of an all-out sprint at the end of a run...at first the energy system is fat and glycogen, then, as the lactic acid builds up due to the body's inability to keep up with removal..and the burn gets more notable, you start to reach the point of momentary exaustion...that is the lactate threshold. At that point you are using primarily glycogen.
However if you ran and never crossed that threshold, you would continue to burn fat and/or glycogen. The more easily you are able to meet the oxygen needs, as in lower intensity levels at 55% - 70% of maximum, the more it may favor fat burning.
Walking is lower intensity...say 35%-55% of Max..and so also relies on fat and/or glycogen.
So what is the
and/or?
If you are loaded with glycogen when you set out to walk or run..you will use more glycogen while burning fat.
If you do it after you lift (lifting being anaerobic and only being able to use glycogen) then your glycogen stores may be depleted and so you will likely use more fat.
HOWEVER!!!
The body has another source for glycogen!!!
MUSCLE and dietary proteins.
If your calories are below BMR, then your body will not likely supply fat for energy. Instead it will hoard fat and store all available calories as fat and burn muscle and dietary proteins.
If your diet does not favor fat release, then you will burn muscle and dietary proteins.
If you eat too few carbs and do not favor fat release...then you burn muscle and dietary proteins when you lift AND when you do cardio...
If you only do cardio and do not challenge muscle...then you surrender muscle faster.
This is just the tip of the iceberg. It is even more complex than this. You could take a physiology class and get the whole scheme, and even then only a few instructors understand the whole effect...so you might not understand all the interactions in a real world application...
Example: Lipoprotein lipase is released under certain dietary circumstances. When it is released the body is not able to burn fat. If, at the same time there is insufficient dietary protein and carb intake...then the body will break muscle down to meet energy needs ALL DAY LONG! Simultaneously, the thyroid is altering its release of hormones that determine metabolism...slowing it so that you may not need to lose as much muscle - while you are burning muscle and storing available calories as fat....that is a combination of 4 separate factors that are generally not connected in text books.
When I work with a training client, I teach them to control the hormonal state that the body is in, in order to favor the state that helps them achieve their goal...either muscle gains, fat burning, more energy...we can control all that.
Misinformation and simply being mislead and not "getting it" is why so many people fail to achieve their fitness goals.
Hope that ...errr... helped!
