Splitting up Cardio?

[xlxBigSexyxlx]

I dont know about cortisol and burning muscle and all that. Protein accounts for less than 4% of total energy expenditure during exercise. Burning protein as an energy source is very energy demanding and takes a long time to convert protein to a usable energy source.

Glycogen is the most available energy source that the muscle cells have to produce ATP. The Phospho creatine system will only recycle ATP for about 1-2 seconds before its depletion during cardio. Then the next source of energy would be glycogen stores being converted to free form glucose 6 phosphate. Until O2 debate is payed back if you will. The muscles will be under anaerobic conditions and will produce ATP via glycolysis. As the body begins to adapt to exercise, fatty acids will start to be more and more mobilized as an energy source.

Then you throw in the process of after burn or the calories being burned after exercise has been stopped. The fat burning mode can be extended for another hour or two too account for the raised metabolic state of the body and to replenish glycogen stores in the muscle. Recent research has suggested that by doing two shorter bouts of exercise twice a day burned more calories than doing on longer bout of the equal amount in total. Again the mechanism is believed to be from the process of after burn.

interesting. so 30 min in the morning, and 30 min postWO?
or 30 min in the morning, and 30 min pre wo?

[MuscleScience]

interesting. so 30 min in the morning, and 30 min postWO?
or 30 min in the morning, and 30 min pre wo?

Yeah I would say based on all the literature that I have read that cardio should always be done post workout never pre workout. I say never but I personally do cardio before my back days as it just seems to help with my lower back and warming it up, which i have a lot of problems with my lower back.

The common conclusions and what I have always been taught is that depleting glycogen before working out cause additional stress on the muscle hence less growth and repair and can actually retard the metabolism. Some would think that since your glycogen stores are depleted that when you start lifting that its at such a low metabolic demand compared to aerobic exercise. That your body would have enough time to burn fat as an energy source. Which it does to an extent, but what a lot of people forget about is that after your done doing cardio it doesnt mean your body is.

What I mean by that is your heart rate and metabolism will still be elevated for some time. Couple that with the fact that now your adding additional demand to the muscles they will not have as much time to produce energy via oxidative metabolism. What ends up all that lactic acid your muscles produced during cardio is shuttled to the liver and converted to pyruvate. Pyruvate is then shuttled back to the muscles and is used as part of the metabolism so no new carbohydrates are being used as an oxidative source. It is using the end product of glycolysis which is ten enzyme pathways shorter than that of using glucose as the starting substrate.

So naturally you can see how your body is going to use the fastest energy source with the least amount of energy to covert it to ATP. Where as doing cardio after resistance exercise already has the fat burning process ramped up and going strong, which spares to an extent muscle glycogen. Lets not forget about elevated epinephrine levels which cause fat mobilization to increase also.

[xlxBigSexyxlx]

what about PWO shake?
if i was to do 30 min of cardio pwo, when would i take my shake? Cuz if I wait, and do 30 min of cardio, it would be 45min-1hour after actually lifting weights by the time i get home and down a shake.