Hi,

I was reading through the Top 10 Myths of exercise and one of them said that after 60 minutes of cardio you stop burning fat and start burning muscle, which in the long run of course will make you burn less calories when you are resting and will make your body look flabby if you lose muscle.... well i am just wondering how is it that the Biggest Loser contestants exercise for HOURS and HOURS..... and they all gain muscle and have lost huge amounts of weight. I need to lose some weight and want it gone in a quicker amount of time(i know slow and steady is beter) but anyway I have been doing 90 minutes of cardio, instead of 60.... to try to get it to come off a little faster. Is this bad? Is it really true that after 60 you burn muscle and are basically screwing yourself? help please.... thaks!

No. After 60 minutes of cardio you do not stop burning fat and start burning muscle. For the first roughly 90 minutes of exercise you burn a combination of fat and glycogen (carbohydrates stored in the muscle). The higher your intensity the more of what you burn is glycogen and the faster you will deplete it. Theoretically you COULD burn all your glycogen in 60 minutes but very few "regular folk" have the aerobic fitness to do so.

If you deplete all of your glycogen your energy level will plummet and you will be unable to maintain the intensity. You will also notice that you get some interesting mental processes. At that point if your body is totally depleted of carbohydrates it will be primarily burning fat for fuel. It will burn a small amount of protein to feed the processes that can not live on the byproduct of fat burning - mainly the brain.

Both the glycogen and the muscle can be restored by eating a mix of protein and carbohydrate following the workout, although muscle may build more slowly.

Your best bet for weight loss is to SOME days do longer sessions and SOME days do shorter sessions at higher intensities.

TBL contestants gain muscle by lifting weights. They workout 6 hours a day but only short sessions of that are at high intensity. The bulk of the time is at low intensities where you burn primarily fat as fuel. (but fewer calories/hour)

"Both the glycogen and the muscle can be restored by eating a mix of protein and carbohydrate following the workout, although muscle may build more slowly."

A bit off topic but related.... My coach was just saying today too that it's best to eat some recovery food within 15-30 minutes after a hard workout to help restore those glycogen stores... Otherwise if it was an especially high intensity day you'll take much more time to recover. After 30mins or so you lose that "window" so that's something to keep in mind if you plan on doing the 90mins daily. Keep a recovery snack on hand.

As far as The Biggest Loser most average people will only "lift" enough to keep muscle loss at bay during weight loss. They don't tend to gain much as much as you might assume. (Because otherwise not only do you lose muscle mass from dieting but also because your not carrying around the same heavy weight on your legs every day)

90 mins really is a reasonable amount of exercise and not excessive so I wouldn't worry too much.

I agree with Ennay-- 90 minutes a day EVERYDAY is a little excessive...change it up a little!! The body needs "easy" days toos!!
Ennay- That was interesting what you wrote about depleting glycogen and "interesting mental process"--i.e; the body burns protein from the brain to keep going...i never knew that! I thought "hitting the wall" was entirely in your body, so to speak!

Ahhh mk - if you hit the wall in denver then you will know. But you may not, it is not given that one will hit the wall in a marathon. Most people fade and think they hit the wall but if you go from say 10 mm to 10:30's that isnt the wall. The wall takes you from 8 mm to 11-12 mm. Or to a dead stop.

Anyway as you approach the wall your rational thinking decreases mightily. The ability to do mental calculations fades. Some people get down right funny. If you ever do hit the wall you will know without a shadow of a doubt.

(the protein burned isnt FROM the brain, its from your working muscles to keep the brain going)

That's the thing though she said it's good to mix up the intensity/time lengths... There is nothing wrong with say on your shorter more intense days (say 30mins) to add in a reasonable easy walk of an hour to get to her goal of 90mins a day.

90 mins isn't over doing it as long as it's not 90mins of high intensity everyday.

I think they are no cannabilizing muscle because 1 - they are so fat, 2) I am sure it is not 6 hours at one time and
3) they are mixing cardio and resistance training.
Six hours of just cardio on a daily basis would stress their body and cause them to release cortisol and too much of that causes the body to start burning muscle as fuel.

I agree with the protein/carb snack after weight training. I do also believe if you do cardio on depleted glycogen stores you dig into fat faster. Not everyone agrees with that.

I think 90 minutes at a time is a little excessive too. But if you want to break it up into 3 30 min increments that should be fine.

This is what a physician friend states:

Two days a week I run for more than 90 mins (I also do aerobics 60 mins and HIIT 20 mins on one day a week) and I lift weights for strength and building three times a week and I've been doing this since October 2008. I'm leaning out, gaining muscle mass and I'm getting stronger *shrugs*. I guess it all depends on the person.

Not really...because as we say...that whole 60 minute catabolism is basically crap.