Burning Muscle???

acknan

The other day I noticed that someone wrote on a forum topic that if you work out for more than 40 minutes, you start burning muscle rather than fat. Even with my limited knowledge of anatomy and nutrition I feel that I can safely say that that is total baloney... BUT, I just wanted to check in.

Does that makes sense? Is it accurate? I work out much longer than 40 minutes at least five days a week, wouldn't I be muscle free by now? Sorry for the sarcasm, but it just sounds preposterous.

Thoughts?

KSU93Amy

I saw that as well....and thought the same thing. I'm thinking if that were true, we wouldn't have hour long cardio classes.

corpus_validum

Depends. And there is some truth to that.

Take for instance professional bodybuilders, the individuals most concerned with muscle loss. You'll rarely see them performing intense cardio for more than 40-60 mins being afraid of catabolizing their muscles (unless they're in their cutting stage, but even then).

There are studies that have proven that too much cardio along with large caloric deficits can actually hinder fat loss. Here's a good article that helps explain it:
http://www.bodyrecomposition.com/fat-loss/why-big-caloric-deficits-and-lots-of-activity-can-hurt-fat-loss.html

For the beginner and/or obese individuals, it's not something to be terribly concerned with though. It's generally recommended that they start off doing a lot of cardio to raise their fitness level first so that they can better implement weight resistance training, HIIT, etc. later on.

javamonster

I am trying to wrack my poor tired brain and recall my nutrition and physiology courses from university. At 40 mins and a certain HR and certain level of fatigue your muscles start to work anaerobically rather than aerobically, using lactic acid as fuel rather than glycogen (when glycogen stores are depleted). As far as I know that just means you are using a different muscle type (slow twitch rather than fast twitch) when your body switches from aerobic to anaerobic.

I know that when you first start to diet, severe caloric reduction produces an initial loss that is catabolic, and you are actually losing muscle mass (and water). Also there comes a point where if your body fat is so low and you're not getting enough calories your body will start to break down muscle - starvation will do this.

Maybe what they are talking about is when your metabolism is using glycogen (from the muscles) for fuel instead of burning fat? Glycogen is depleted and restored with exercise/nutrition/rest.

Someone feel free to correct me! It's been a while! I'm sure there are holes and/or errors in what I remember.

Heather75

acknan, I saw that too and it freaked me out for about 10 seconds. I'm not an athlete - I'm just a chubby girl trying to lose some weight, so I am not going to get bogged down in the science of it all. I'm just going to keep moving my body and watching what I eat so I can feel better and get stronger.

My body would have to work pretty hard to even FIND a muscle to consume. Good luck, body.