Just read the Chicago marathon thread on some on here who trained and posted training on Chicago and their results.
Seems like common theme is "was feeling great through 1/2 but then at 20, the wheels came off".
Is this a problem of
- Overtraining. People training too hard and arriving at the race fried already.
- Unrealistic goals of what they can actually run and going out too fast.
Being on pace at half way does not qualify for running within your capabilities.. Being on pace at 22 miles, qualifies as running a capable race.