Train Low and Race High is a recent concept that is gaining popularity with the endurance crowd in the last few years. There is growing research that it is indeed a valid training concept for training. Essentially, train low race high refers to training with lower glycogen stores and racing with high glycogen stores.
This can be accomplished a few ways; daily training with incomplete post exercise nutrition, twice a day training, and training in a fasted state. Significant time to exhaustion and total work performed were noted in the 2x training a day groups. The ability of the muscles that were trained in low conditions showed significant ability for the muscles to burn fat for energy and and to uptake carbs for glycogen storage.
This is turning the concept of never going into muscle glycogen debt into consideration. It is perhaps giving up the workout that is done in glycogen depletion in order to make physiological adaptations for a future race.
Training with low glycogen levels don't seem to impart any significant value to strength training.
Although there has been shown some cool aerobic metabolism changes that occur, no real performance gains have been noted on race day for high intensity activities. Only longer distance may show some gains. So that is a huge point to take into consideration.
It is more stressful to train this way. Stress hormones will increase. The lowering of post exercise immunity can lead to more colds and sickness. There will be less training volume as you can't last as long in each session.
There are some points for training this way for some physiological adaptations, but how much this translates into performance is still up for debate. There will be some definite drawbacks for training this way full time, but perhaps early in a training cycle makes sense.
This is a great paper from pponline. Sports Nutrition: The latest in low glycogen training. This was a great video on High Performance Training and Nutrition.
Jamie Scott—High Performance Evolutionary Fitness - Using EvoBio to Optimize Training for Endurance (AHS12) from Ancestral Health Society on Vimeo.