Wow! Good for you for working out like that! :) I have yet to get back to that part of my health regimen, oh dear!

There are probably two issues going on with the post-muscle use exaustion.

First off is the liver stores glycogen which is released during exercise for energy. A congested, weak liver can't store as much glycogen or convert sugars that fast, so your muscles will be depleted of their own glycogen stores (they rely on the liver for glucose to turn into glycogen, they then store the glycogen in preparation for fight-or-flight) for much longer than usual. Eating high GI carbs post-workout should aid this until your liver gets stronger. You should focus on low-GI carbs most of the time.

Also what could be happening is your releasing toxins stored in fat and muscle as you exercise, so the liver is having to deal with this which isn't easy. Flush your body with lemon water after a workout, this should help.

But mostly it's the whole glucose tolerance factor that gets wonky thanks to the liver. IF you take a multi-vit, find one that has GTF chromium instead of just plain chromium. Solaray's Spectro mix is my favorite multi vit-min because it has this and other great things.

Hope that answers your question! :)