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Originally Posted by kfisherx
Are there any generally accepted ideas, articles, studies or references on fat burning and cardio or is this just a subject of too much controversy for people to generally agree? I am looking around this site and the web for my and not being succesful on finding articles that do no conflict somewhat. I fear this is sort of like the whole squat debate and that I will have to go through another long series of questions to really get what I think is right amongst all the opinions.
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Hi Karla,
IMO, here are the best articles you're gonna get on this subject (pardon me for including my own):
Myths Under the Microscope Part 1: The Low Intensity Fat Burning Zone - AlanAragon.com - Fitness Based on Science & Experience
Myths Under the Microscope Part 2: False Hopes for Fasted Cardio - AlanAragon.com - Fitness Based on Science & Experience
Myths Under the Microscope Part 3: Discussion & Afterthoughts - AlanAragon.com - Fitness Based on Science & Experience
Steady State vs. Interval Training: Summing Up Part 1 | BodyRecomposition - The Home of Lyle McDonald
Steady State vs. Interval Training: Summing Up Part 2 | BodyRecomposition - The Home of Lyle McDonald
Steady State vs. Interval Training: A Conclusion | BodyRecomposition - The Home of Lyle McDonald
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Specifically I am looking for answer to the following?
At what point in a cardio routine does a person go from fat burning to LBM burning?
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Regarding your bolded question, it really all depends on the nature of the fed status of the trainee, but more importantly, the diet as a whole. The most useful answer I can give you is that you generally don't have to worry about muscle protein loss resulting from intense cardio unless your overall protein and calorie intake is insufficient. If you train fasted, or if there are no exogenous substrates (ingested fuels such as protein or protein & carbs) being absorbed into circulation during training, a loss of muscle protein can occur to varying degrees depending on the intensity and/or duration of the training bout. But keep in mind that this can be a temporary condition reversible by feeding. Overall, I'll caution you against overthinking this and arguing with ignorant folks...
The rest of the stuff I'll mention really isn't that important but might give you more food for thought. Muscle protein loss is measurable by various indexes including elevations creatine kinase levels and/or 3-methyhistidine levels. Muscle protein loss can more directly be measured by arterioveinous amino acid balance, and even more directly through needle biopsy. Another thing to throw in here is that when you speak of LBM loss, there is nonessential (water, glycogen, etc) & essential LBM (the protein components). The net loss of essential LBM is a bit more of a long-term process as a result of insufficient dietary factors, whereas nonessential LBM loss is either a neutral or bad thing depending on the goal of the trainee. Unfortunately, none of this stuff has been systematically investigated to the degree that would satisfy your question, Karla.