The Wall???

Yep, it's glycogen depletion... lots of resources online, this might be a good start http://en.wikipedia.org/wiki/Hitting_the_wall

While I've never hit it, I spend a lot of time with hardcore runners. I believe a 'wall' is a limit you reach well within a run- you start out fine, you run for miles, you go further/harder/faster than you usually do, and at some point everything about your body stops working. There are videos of it online where people are literally crawling because their leg muscles don't coordinate properly. Not a normal 'tired' situation and there isnt much to get past it, just better energy conservation and pacing practices before you get there.

What you've experienced is probably just short-term overtraining. You've used up all your glycogen stores, and you need to take at bare minimum a day to recover.

There's my 2cents ;D

It's absolutely possible to hit "the wall" at any time. Basically, this just happens when your body runs out of glycogen. If you ran a lot more than you normally do and didn't up your carbohydrate intake, it's very likely that your body ran out. It's harder and takes longer for your body to convert fat to energy, which is why everything starts to feel harder. Carb up!

Could be glycogen depletion or dehydration...try some good carbs and water then try again. You can definately overtrain...running every other day gives your body time to repair and restore itself...running everyday may be too much. Be careful.

Also, do you use gels of any kind during a log run? Over 4 or so, you may find then useful to sustain.

my boyfriend reads men's health religiously and I remember his mentioning something about carbs, fat and protein before a big workout (60 min??? or was it 30??) and then protein after. Not sure how much or exactly when since it didn't really apply to me, women have slightly different needs when working out.

I bonked on runs when I was running every single day. I was also trying to stay lower carb at the time, so it was likely a double whammy.

Now days I mix up my run days with strength days and cross training days (bike, elliptical or skating). And I only do one "long" run a week, the others are shorter. Plus I take an entire day off every week for recovery. I also stopped trying to eat lower carb. Even so, I still have difficulty keeping my carbs up any higher than 40-43% of my daily calories (I'm aiming for 50%) simply because I got so used to the foods I ate on a regular basis before.

Since I made those changes I've only bonked on one run. And it was likely my own fault cuz I did a little over an hour of strength before the run and I hadn't eaten before I went to the gym, so by the time I got to my run it had been over three hours since I'd last eaten, and that was only a small snack. So I was ridiculously hungry and had no energy whatsoever. It literally felt like I was running on empty.

I don't run what's really considered long distance, so the idea of "carbo-loading" isn't really needed. But I tend to do well with runs when I stick something like a Luna Bar around 30-45 min before a "long" run or any normal meal about two hours before. Then a small bit of something that's mostly carbs, with a little protein, after the run. I only do higher protein/lower carb after strength only nights. (1.5-2 hrs of strength only)