A strenuous workout, whether you're training for a 10K or sweating your way through a tough body-sculpting routine, can leave your body depleted of important nutrients, especially protein and carbohydrates. After you exercise, your body uses proteins and carbs from your post-workout munchies to repair damaged tissues and to restock energy supplies.
Resistance training, such as weightlifting, breaks down the proteins that make up your muscle fibers. After your workout, your body uses amino acids, the building blocks of proteins, to rebuild your muscles, making them stronger than they were before. Proteins can also be broken down to provide energy, particularly during a long bout of endurance training, such as a marathon. Whether you chug a shake or chow down on a steak, including some protein in your apres-workout nutrition will give your body the raw materials it needs to repair damaged tissues.
Your muscles store carbohydrates in the form of glycogen. When you exercise, glycogen is broken down into glucose, or blood sugar, to provide energy. Intense exercise, such as sprinting or interval training, can rapidly drain your glycogen stores, as can a long run or bike ride. After your workout, your body uses carbs to replenish muscle glycogen. Because glycogen is synthesized most rapidly during the first few hours after exercising, carbing up soon after you train will help max out your glycogen supply.
If your body doesn't have enough carbs available, such as during a long bout of intense glycogen-depleting exercise, your liver can convert amino acids into glucose to provide energy for your muscles. This leaves fewer amino acids available to repair muscles and other tissues after your workout. Post-exercise carbs have a protein-sparing effect. By maintaining your blood sugar levels, carbs free up amino acids to be used for protein synthesis.
In a 2009 joint position paper, the American College of Sports Medicine, the American Dietetic Association and Dietitians of Canada recommended that athletes consume six to 10 grams of carbohydrates per kilogram of body weight per day. Endurance athletes such as distance runners should aim for 1.2 to 1.4 grams of protein per kilogram of body weight, while strength athletes such body builders may need to consume up to 1.7 grams. Eating a meal that contains both carbs and protein within two hours after you work out will help maximize glycogen storage and protein formation.
- Journal of the American Dietetic Association: Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance
- Nutrition for Sport and Exercise; Marie Dunford and J. Andrew Doyle
Joe Miller started writing professionally in 1991. He specializes in writing about health and fitness and has written for "Fit Yoga" magazine and the New York Times City Room blog. He holds a master's degree in applied physiology from Columbia University, Teacher's College.