“Training low” (with low carbohydrate stores) and "competing high" (with muscles fully loaded with glycogen) as a means to enhance competitive performance is receiving attention from coaches, elite athletes, and researchers alike. A 2005 study (1) with untrained subjects suggests that training with deplete glycogen stores can enhance adaptive muscle responses to conditions that might occur at the end of a competitive event. Training low might also reduce reliance on limited glycogen stores. When Hansen’s subjects“competed” with loaded glycogen stores, they performed better.
These results have raised questions and controversy. If you restrict your carbohydrate intake during training, you will become unable to train hard, and that can hurt your athletic ability. Sports dietitian Louise Burke PhD of the Australian Institute of Sports suggests inserting a few “training low” sessions into the training program where the focus is on making “aerobic” gains. You would want to target the sessions in the week where quality, intensity, or techniques are not as important.
You can train low by having either low blood glucose or low muscle glycogen; both scenarios can happen during a second training session in a day. Note: Adding caffeine to a “low” training session can enhance power by about 9%, but this still does not match the power generated by fully glycogen-loaded muscles plus caffeine.
Training low is not much fun. For most ordinary mortals, staying well fueled on a daily basis is a smart investment. I suggest you fuel your muscles on a daily basis with quality grains, fruits and vegetables. By being well fueled, you'll be able to work hard and enjoy improving your performance.
(1) Hansen A, C Fischer, P Plomgaard, J Andersen, B Saltin, B Pedersen 2005.Skeletal muscle adaptation: training twice every second day vs.training once daily. J Appl Physiol88(1):93-9
For more information on how to win with good nutrition: Nancy Clark's Sports Nutrition Guidebook