Week after week I felt my overall energy and strength to be able to run the long tempo runs and long runs, which are so important to marathon training, gradually deteriorate. In an effort to restore my body I tried everything from nutritional supplements to acupuncture, yet nothing seemed to help. I tried resting from training for three days and I tried cutting all my afternoon runs until a couple of days ago, at which time it was clear that I was out of time and the only solution would be complete rest, which is why I am not going to race again until 2011. I am going to take a good break and then begin a much more gradual training cycle as I begin preparations for a spring marathon -Ryan Hall (Why I Decided To Not Run Chicago)
Besides the obvious (blood test to check for anemia other abnormalities) what should Hall do?
I found this interesting article Overtraining Effects On Performance: If you want to prevent staleness and overtraining, keep a record of your quality of sleep and levels of fatigue! that identifies poor sleep as a leading indicator.
From a personal perspective, I was running well a couple of years ago with a 2:55 at the 2008 Seattle Marathon and again in March 2009 at Napa Valley (see splits here). At the time I was only doing 17 mile long runs, and felt that I might improve if I got that up to 19 or 20. The problem was the longer run led to a longer recovery, and I ended up in a state similar to what Hall is describing. Looking back, I also underestimated the importance of sleep (I had my share of bad nights living upstairs in an adult family home).
Unless Hall is absolutely zapped, my recipe for recovery would be to come down from altitude for a month and just run comfortably as he feels and add some cross training until he snaps out of it. I'm not a believer in extended lay-offs because to do so requires a build-up, and those are never fun. Just my opinion, but I think that's the hard way to do it.
Here is more good insight on overtraining from Owen Anderson (I wondered whatever happend to him!) at educatedrunner.com.