Something I just learned (and anyone who knows more about aerobic workouts, please correct me) is that if your aerobic workout pushes you too far past your target hart rate you start burning muscle, which, of course, would be counter productive to strength training.
Actually no. Pushing your cardio workout too far past your target heart range means you redline your heart...which can get dangerous. Your heart does have a 'max' rate that it can go.
The lower section of the heart rate range (60-80% of max) is the aerobic zone (aerobic = with oxygen). It takes about 20 minutes of exercise in this zone for the body to start buring fat. A 30 minute cardio excercise is 20 minutes of getting to the point where the body can burn fat, then 10 minutes of burning fat.
Body fat is a complex molecule that has an inner layer of Carbon and Oxygen and an outer layer of Hydrogen. The fat burning process starts by burning off the outer layer of Hydrogen. (H2).
Oxygen (O2) is required for any kind of combustion, including the burning of fat.
2 H2 + O2 = 2 H20. Water. This is why water is very important for those trying to lose weight.
Excercise in this range usually feels good. An unscientific way to judge if you are in range is the "talk test." Can you hold a conversation while you are excercising at that range? If yes, you are still in the aerobic zone of exercise. If no, you have gone up to anaerobic zone of excercise.
80-90% of your max heart rate is the anaerobic zone. (Anaerobic = without oxygen).
So...since now the process has no more oxygen, whatever gets combusted must have its own oxygen supply. What gets burned is glycogen, a sugar fuel in the muscle tissue.
[SIZE=-1]So...muscles have this complex polymer called Glycogen C24H42O21. Since there is no water involved the body's phosphates break off some of the oxygen molecues and start the combustion process.
At some point in this process...the body reaches an anabolic threshold. (anabolic - muscle building). This is when you feel your heart rate climb and you start breathing hard.
Glycogen gets burned and breaks apart in to amino acids...which strengthen the muscle tissue.
Burn, baby, burn.
And...burn it does, in more ways than one...because the result is...
C3H6O3
Lactic Acid. Ouch!
For folks that can deal with the lactic acid burn...this is what is making your muscles stronger, the burning of the glycogen in to amino acid.
The body can sustain a good amount of activity at the anabolic threshold.
However, if the excercise stays constant, the body will reach a point where it runs out of glycogen. It is at this point where the process becomes catabolic and muscle tissue is burned.
The amount of glycogen burned is going to vary by activity. Weightlifting burns up more glycogen faster than jogging does. This is why folks that belong to a gym should do weights before cardio....the muscles still have their full amount of glycogen in them.
Above 90% heart rate is your hearts redline zone.
Danger Will Robinson.
Short training can improve the condition of some of the slow twitch muscles...don't exercise this hard unless you really know what you're doing. Plus lactic acid hasn't gone away....ouch!
That's the excercise zones.
The other element to glycogen levels is diet. Lean protein, lots of veggies, avoiding junk...
I hope that wasn't too nerdy.
[/SIZE]