Most runners tend to focus on miles and paces. Improvements in fitness, however, occur during the recovery period between training sessions, not during the training itself. Physiological adaptations to training occur with a correctly timed alternation between stress and recovery.
When you finish a long run or a race, you are weaker, not stronger. How much weaker depends on the severity of the training stress. If the stress is too great and you don't recover before your next workout or race, your performance and ability to adapt to subsequent training sessions declines. Therefore, what you do the rest of the day when you are not training is just as important as the effort you endured.
Possibly the single most important aspect of optimal recovery from training and racing is refueling nutrient-depleted muscles, and the most important nutrient to replenish is carbohydrates. Endurance performance is influenced by the amount of stored carbohydrates (glycogen) in skeletal muscles; intense endurance exercise decreases muscle glycogen stores.
Glycogen resynthesis is most rapid if you consume carbohydrates within the first 30 to 60 minutes after your run. Delaying carbohydrate ingestion for two hours after a workout significantly reduces the rate of glycogen resynthesis within the first few hours.
To maximize the synthesis and storage of glycogen, consume 1.5 grams of simple carbohydrates (sugar, preferably glucose) per kilogram of body weight every two hours for a few hours after your workout or, if you can eat or drink more often, consume 0.4 to 0.6 grams every 15 to 30 minutes.
Some studies have found that eating protein and carbohydrates together maximizes recovery, although the total amount of calories consumed seems to be more important than the carbohydrate-protein mix. Since consuming protein helps rebuild skeletal muscle fibers that have been damaged during training, protein has its own merit for optimal recovery.
Initially, consume carbohydrates from fluids. For most commercial sports drinks, such as Gatorade, the above recommendations correspond to about five 8-ounce glasses every hour for a 154-pound runner. Admittedly, this is a lot to drink. To meet your recovery needs, "carbohydrate replacement" drinks are a better option than "fluid replacement" drinks like Gatorade. Chocolate milk, with its high carbohydrate and protein contents, is an effective post-run recovery drink.