I read on the Biggest Loser they exercise 6 hours a day, 2 hours at a time. On Jillian Michael's radio show she says not to workout for more than 2 hours at a time because your body will release stress hormones. How long in between the 2 hours should you wait to workout again?

I'm no expert, just stating here the few things I think I know.
I can hike on the mountains for 12 hours per day, non stop, so is it calld workout?
At the same time I know I read somewhere that after 1 hour exercise the body releases substances that don't allow you to burn any more fat. Not sure. But honestly I find that 6 hours per day is excessive!

There's alot of variables with things like that. Is that two hours strenuous? Continuous? Cardio? Running on the treadmill for two hours is alot different than lifting weights at intervals for two.

2 hours of anything... nothing all out strenuous or running for that long. Maybe an hour of weight training (one day upper body, next lower body, next pilates), then an hour of walking, than take a break for a few hours and do a kickboxing video and do some stretching. Just to move and burn some extra calories.

6 hours might be too much, but just a reference they do it on the Biggest Loser show. Not all at once, 2 hours at a time 3x a day.

I think on TBL they have medical support staff/etc to monitor heath. In any event, it seems to me that there are a whole bunch of factors involved: how intense is the exercise, what exactly are you exercising, how long are you doing it for at one time, and how much time are you taking off inbetween sessions.
Overtraining is often mentioned with respect to exercise, where you don't give your body enough time for muscles to repair themselves -- this especially applies to weight training.
Stress fractures and tendon/ligament damage can happen if you overdo it.
If you burn up a whole bunch of calories during these exercise periods and don't eat enough calories, you can bring your whole system to a halt.
You see all of this on TBL -- knee problems, leg problems, stress fracture to a hip, no weight loss even if the contestant really hit the gym and cut their calories...
I suspect that TBL is doing 2 hours of endurance type activities and/or flexibility and stretching exercises (long hikes, yoga, for example), then resting, then 2 hours of intense weight-training activity, then resting, then 2 hours of cardiovascular interval-type training, then resting. Probably so that one system doesn't get overworked -- ie 2 hours lower body weight training, next day 2 hours upper body weight training, next day 2 hours core training...and so on...to try to minimize injury.
Personally, I have enough trouble doing my yoga workout (90minutes) but I can see adding running and weights to this without too much difficulty. But I'll have to balance it out -- yoga/swim in am, evening walk/weights.
I think people are far more resilient that we give credit, and that amazing things can be done physically if one puts one's mind to it. You just have to be super-aware of muscle/joint pain and tightness, and pull it back ASAP and heal up if there is a problem.
Kira

In real life, if you're finding yourself spending 6 hours a day working out on a regular basis it's time to get treatment for exercise anorexia.

I think it depends on your physical condition and exercise intensity. Low intensity activity can be maintained for a long time, the higher the intensity, the less time you can sustain the effort. Training allows you to sustain a higher intensity, for a longer period of time.

Hiking is one of my favorite activities, and we'll do a 15 miler day hike over a period of 7 or 8 hours. Or think nothing of kayaking for 4 hours. You have to be in shape for it, fuel appropriately, and go at a pace that is moderate and sustainable for you.

<warning, rant mode on>
C'mon people, humans used to work out in the fields, HARD, all day long!! They had to chop wood, pump water, milk the cows, and that was before breakfast. We are built for work, we've just gotten so sedentary as a society, that now we have to start slow and work ourselves up to it. Now we think that working our muscles hard for 2 hours is excessive? Our perspective has certainly changed.

Sorry -- hot button topic for me .... rant mode off.

I just wish I had the TIME to even consider such a thing! I'm not saying my body couldn't do it - esp. if you're talking maybe 2 hours of gym-type workout & then some more recreational stuff like hiking or bike riding or walking with the dog - but no way would my schedule allow it!

Ditto, wonderful rant ....

i agree witht he above quote. By working 8.5 hours a day and chasing after a one year old and 5 other boys. I think when I get 30 minutes to exercise I am doing great. If I was able to stop working, cleaning, cooking, and driving I still think I would not exercise more than 2 hours a day.

That's a different issue though -- ability vs. availability. One of the reasons that TBL folks lose weight the way they do is because they CAN devote so many hours to being physically active. I wish I could too, but I'm right there with most of you; working a full time desk job, mom, wife, volunteer, etc. There are only so many hours in the day that can be available for physical exercise, unless you're on vacation or you carve it out of weekends somehow.

But we have the genetic capability to do MUCH more than the average person actually does. In our modern age of cars, computers and conveniences, our daily-life physical activity has decreased significantly. And then we have to try to make up the difference in intense short work-outs.

There's no way my body could handle 6 hours a day. I don't think that's healthy. Also, I'm sorry but Jillian isn't a doctor. I will stick to what works and lose weight as God wills me to.

And a gentle warning from the opposite side ...

If you try to go from doing absolutely nothing, to working out 2 hours a day, you are going to get injured. If you've been sedentary, you really do have to work up slowly. Been there, done that.

It depends what you are doing with respect to the post above. There is absolutely no doubt in my mind that if you put a truck with a MILLION dollars CASH in it and said to a sedentary person that they had to walk for two hours to collect it, it wouldn't be an issue. But swap the truck with money out for a big pot of GOOD OL' HEALTH, and people "can't do it". It is amazing what a person CAN do even if they have been inactive. I personally think
---rant---warning---
that there are a HUGE number of of over-coddling chickens who really limit themselves and their capabilities by pre-determining what they think they can do. And when one argues for those limitations, one generally get to keep them.
Now, in no way do I mean that you can run a marathon tomorrow without training, but you'd be surprised at what you can do if and when you have to. And I really believe that those who think that moderation in everything is "best" severely underestimate what they are actually doing vs what they are capable of doing vs what they need to do IF they want to get fit and/or healthy. Often, people do what exactly what they think it will take, and not what it WILL take to accomplish a goal. And then complain when they don't reach their goal! This. Drives. Me. Nuts.
--ok rant over--
Kira

Absolutely!!

Also, our bodies have this remarkable way of saying, "hey! take a break! I'm tired!" or, "Hey! Could you get off the couch?"

I KNOW when I'm overtraining. I can feel it. I also know when I should probably be burning off a little more energy.

Listen to your body. Don't ignore its cues