It's been a couple years since I dug into the research myself, but doing a quick search it appears to be related to depleted glycogen, depleting bio-available t

It's been a couple years since I dug into the research myself, but doing a quick search it appears to be related to depleted glycogen, depleting bio-available testosterone, a rise in cortisol, plus various immune system changes. It hard to find specific articles on the internet though, but here's one that's talks in a general way about it, but doens't come out and say one hour. http://chriskresser.com/why-you-may-need-to-exercise-less http://chriskresser.com/why-you-may-need-to-exercise-less Here's another that graphs the cortisol response vs time, but doesn't link to the specific article. http://www.bodybuilding.com/fun/drryan6.htm http://www.bodybuilding.com/fun/drryan6.htm