The meal that athletes eat after a workout could be said to be the most important meal of their day. During this time, there is a unique window of opportunity wherein the muscle cells are most able to take up glucose and amino acids. Both these nutrients are necessary for physical recovery from the stress of the workout. For the average person, one gram of carbohydrate for every two pounds (about one kilogram) of body weight, combined with a serving of protein, will allow sufficient nutrition for the replenishment of glycogen stores, and the synthesis of new proteins.
Glycogen is a form of carbohydrate that is stored within muscles cells, and is the primary source of fuel for most exercise. During a workout, glycogen becomes depleted as the cells utilize it to power muscular activity. The carbohydrates that athletes eat after a workout are used to replenish glycogen stores, a process that takes at least 20 hours, and under extreme conditions can take up to seven days. For athletes training daily, the best carbohydrates to eat after a workout are those that enter the bloodstream rapidly, such as pasta, potatoes, or a commercial, meal replacement drink. Those training less frequently will usually do well with lower glycemic index carbohydrates, as rapid absorption is typically less of a concern.
Protein is another nutrient that is important to eat after a workout. Muscle fibers become damaged during intense exercise and require amino acids, the building blocks of proteins, for cellular repair. This repair is the means by which muscles are able to gain size and strength, but in the absence of proper nutrition other body tissues will need to be broken down to supply the necessary nutrients. In the post-workout state, muscle cells are more permeable to both carbohydrates and amino acids, making this the optimum time to consume foods that provide raw materials for cellular growth.
Additionally, when athletes eat carbohydrates and protein in combination after a workout, muscle cells are more able to absorb carbohydrates than if either nutrient is eaten alone. Protein eaten after a workout also gives the added benefit of suppressing catabolic hormones, such as cortisol, that would normally stimulate the breakdown of cellular material to compensate for energy lost during exercise. At the same time, protein eaten after a workout stimulates the production of anabolic hormones, such as insulin and testosterone, to assist in the repair of muscle tissues.
The optimal carbohydrate-to-protein ratio varies depending on the fitness level of the athlete, and the nature of the activity. In general, the optimal carbohydrate to protein ratio ranges from 1:1 to 1:4. Low-intensity, long duration activities, such as distance running, will require a higher proportion of carbohydrates. High intensity exercise, such as weight lifting, will do more damage to the muscle tissue and require a greater proportion of protein after working out.