This is an excerpt from Practical Guide to Exercise Physiology-2nd Edition by Robert Murray & W. Larry Kenney.
It is now clear that altering the composition and timing of food intake can enhance the adaptations that occur in response to training. For example, purposefully varying the content of muscle glycogen by changing the intensity and duration of training along with the carbohydrate content of the diet and the use (or non-use) of carbohydrate during training can enhance metabolic signals inside muscle cells and thereby improve adaptations to training. (Less clear is whether these strategies consistently improve performance.) These strategies have been shown to stimulate muscle cells to rapidly restore glycogen when adequate carbohydrate is consumed, produce more muscle mitochondria, enhance fat oxidation, and stimulate angiogenesis (new capillaries) in muscle. Here are some examples of periodized nutrition strategies:
- Train high, compete high. Consume a high-carbohydrate diet with additional carbohydrate intake before, during, and after training to ensure that muscle and liver glycogen content remains high and that muscles—and the gastrointestinal tract—are accustomed to handling carbohydrates consumed during training.
- Train low, compete high. Consume a low-carbohydrate diet before, during, and after 7 to 10 days of training and do not emphasize carbohydrate in the diet except for the three days leading up to competition.
- Recover low, sleep low. Avoid consuming carbohydrate before, during, and after training and particularly after a hard afternoon or evening workout. Sleeping with low muscle and liver glycogen turns on intracellular signals for glycogen storage when more carbohydrate becomes available.
- Sleep low, train low. Complete a hard afternoon or evening training session to lower muscle glycogen stores, restrict carbohydrate intake to ensure that you sleep with low muscle glycogen, then complete a morning training session before consuming carbohydrate to further reduce muscle glycogen. Resume carbohydrate intake after the training session.
Nutrition periodization can parallel training periodization (see chapter 5) to optimize training adaptations. For example, in early season training when many athletes may be trying to shed fat weight, reducing energy intake (calories) and increasing protein intake can help. In midseason training, periodically limiting carbohydrate intake while maintaining energy intake will augment training responses. Leading up to important competitions, a reduced training volume should be combined with a high-carbohydrate diet to maximize energy storage.