JJ asked a Question on another thread about what it is I train people for, and I have also heard a lot of folks complaining about the fatigue they are feeling after a long day on the road or track.
Here is the down & dirty of how not to "Bonk" or "Hit The Wall".
If this doesn't work, Twist the throttle more, you'll get there faster ... Let me know how that works for ya'
http://sportsmedicine.about.com/od/anatomyandphysiology/a/LT_training.htm 
