Running, cortisol and Catabolism

[epimetheus]

Ok, myth or fact. Does running cause muscle loss? Long distance running that is.
What causes muscle loss when doing too much Cardio? Elevated Cortisol levels? The low bodyfat % of the bodybuilder? (meaning the average joe shouldn't worrry) Burning off of the protien in the muscles (which should only occur when starved of all Carbs, and fats.)?

 

[Loomer]

From what I understand, it is when cortisol is released that glyconeogenesis begins, breaking down muscle protein. Cortisol also releases fatty acids, so it leads to muscle and fat loss in conjunction.

The problem is when does exercise get to the point where it releases the "stress hormone"? I don't think that BF% or the amount of available nutrients (carbs, fats, protein) plays a major part as much as your individual pituitary gland (which signals the adrenal glands to secrete cortisol) functions might. Maybe it's an individual thing? It would be great to know when an exercise goes from beneficial to "stressfull", maximizing (and possibly saving) our time and effort, for those of us over/under training.

Maybe keeping your heart rate and temperature down during your workouts, will assist at keeping the stressor at bay. Also, cortisol levels are highest (naturally) in the early morning between 6 and 8 am (which makes prebreakfast morning cardio seem very catabolic) and lowest around midnight. Cortisol is a little higher after eating too. (which lends support to prebreakfast cardio )

I guess I'm not being helpful, cause now I'm confused.

 

[Manu]

Good question

I don't know what's the answer.
I would had one also: and the effect of glutamine to prevent muscle breakdown? how does it works?