Personally I really like to run. I run almost every day of the week a hard as I can and I have been doing this for almost 2 years. It has become second nature to me and is by far my strong point in Parkour, but can you run too much. I remember my uncle (who is more or less a body builder) saying that the first 5-10 minutes your body burns all the nutrients in your blood stream, next 5-10 minutes it's your digestive system, then your fat, and after an hour or so it will begin to burn muscle. That makes sense because if you marathon runners the obviously have good running legs but they seem awful skinny. Being that I am standing at only 5-6% body fat and don't have a lot of muscle to burn I just thought it might be nice to hear what some of you might have to say on the matter of running too much. Thanks.

physiologically, what you're saying makes no sense to me.  Like steve said, need to read up on your physiology.

I suggest these posts from the CF board where Steve explains how energy is used in detail...

Physiology of Energy Pathways (Posts 1, 2, 3, 14 and 15)
http://www.board.crossfit.com/showthread.php?t=34319

You don't use the nutrients from your digestive system.  I don't even know what that means.

Depending on your goals running a marathon is too much.  Depending on your goals, running a half marathon is too much.  Depending on your goals, running a 10K is too much.  Depending on your goals running a 5k is too much.  Depending on your goals, running 1 mile is too much.  Depending on your goals running 400 m is too much.

Notice a trend?  Depends on your goals

Steve doesn't run more than 400m.  I never ran more than 10k.  Most of the population will never run a marathon.

Haha, from what you guys said I'de have to agree that my uncle most likely doesn't know what he's talking about. Also from the fact that I haven't actually found any article or research about what he said reiterates that fact.

All I have found is: the 10% rule of increasing no more that 10% of your running distance a week, and that the human body is better suited to shorted exertions of energy better that long periods of less strenuous activity, though the human body can adapt to really anything.

SO, let me revise my question: I should run based on my goals, but is there a point where I am running too much to the point where it actually harms me?

Agreed.  This is why we are stressing goals so much.

If you want to a a powerhouse (40 inch vertical, 11 foot broad jump, etc) then running more than 400m at a time may be overkill in and of itself.

If you want to be an endurance beast (i don't know why one would really want this, but whatever) then running higher volumes isnt so bad.

Either case, if you want to improve performance over a long distance or short one, you need to structure your program with attainable goals.

Running just to run is as silly as lifting weights just to lift.

Should be constantly progressing towards a goal.

That is so sad...

I never really ran much because I was asily winded, I used to think that I had a cardio-vascular system that needed major work, but after reading Charles Morland's, (I hope that I remembered the name right), Approach to proper running technique article, I have found that my cardio-vascular system is at least 15 times more efficient than I had formerly thought. I have made a goal for myself, it's very recent, to be able to run two-miles in 20 minutes, without sore legs and without being winded. I this a good ide since before, I generally avoided running?

And your goals are.. what exactly? You never specified.

When I was in high school, during the summer I would run 8-14 miles a day at between 7-8 minute miles everyday except Sunday.  There a runners who can handle running that much everyday, but they build up to it over many years.  I was doing this to prepare for cross-country season in the fall.  But something would always happen that would make me have to stop training for a few weeks right before cross-country season.  One year it was damage to my knee cartilage so bad I could barely walk.  Another year it was anemia caused by the destruction of too many red blood cells and not enough iron in my diet to rebuild them.  Every year it was colds that took weeks to go away. The point is running long and hard everyday is really hard on your body.  I got to be a decent all-around runner.  I could run a 23 second 200 meters and 37:20 10k.  But I always think how much better I could have been if I had been constantly plagued by the setbacks caused by overtraining.  As far as your goals go, it is very hard to be good at everything.  If you like endurance and sprinting, you might want to concentrate on something like the 800 or the mile.