You may have heard of the “R4” system, shorthand for restore electrolytes and water, replenish glycogen, reduce muscle and immune system stress, and rebuild muscle protein. Exercise physiologist Ed Burke and others claim the R4 system is the path to optimal muscle recovery, and there is ample scientific evidence to back them up. In this installment of Training Talk, we’ll discuss the first two “R’s” – restore electrolytes and water and replenish glycogen.
To train day in and day out at your full potential, you must be properly hydrated and have sufficient muscle glycogen stores to fuel your workout. Workouts over 90 minutes long decrease muscle glycogen, and not replenishing these stores may put you in a carbohydrate deficit that prevents you from reaching your training and racing goals.
How do you go about rehydrating and restoring muscle glycogen after exercise? Numerous studies have tackled these issues. Based on the results of these studies, it is now known that a series of steps can be taken post-workout that will optimize your rehydration and glycogen synthesis and allow you to train and perform at your best.
Rehydrate – Adequate fluid intake during training and racing keeps body temperature levels in check and maintains cardiac output. For different reasons, fluid intake during training and racing is usually not enough to prevent a net loss of body fluids. It is therefore important to begin rehydrating immediately after exercise. It is not uncommon for someone exercising in hot and humid environments to lose 8 to 12 pounds of water weight after four hours of exercise. Even cold weather athletes can lose a significant amount of water during exercise.
Rehydrating with a carbohydrate drink mix containing sodium and other electrolytes is preferable to rehydrating with water alone. In one study, subjects who exercised to a point of mild dehydration replaced 82 percent of their lost fluids when drinking a sodium solution during a three hour rehydration period. The subjects who drank water alone restored 68 percent of lost fluids during this period. Carbohydrates also increase water absorption by interacting with sodium in the intestinal wall. The glucose molecules that make up a carbohydrate stimulate sodium absorption, and sodium, in turn, is necessary for glucose absorption. As these two substances are absorbed into the intestinal wall, they pull water with them, thus increasing absorption into the bloodstream.
Replenish – As you’ve just seen, this actually begins during rehydration with the ingestion of a carbohydrate/electrolyte drink that enhances fluid uptake. The timing, amount and type of carbohydrate you take in after training all determine how effectively you replenish glycogen stores.
The glucose molecules that make up muscle and liver glycogen are the primary fuel for moderate- to high-intensity exercise. In order to replace muscle glycogen used during the day’s training, carbohydrates must be consumed. Carbohydrates ingested immediately after training result in the greatest muscle glycogen synthesis. Studies show that restoration of glycogen stores is not as great when carbohydrates are eaten two hours after exercise. Eating nothing after a workout is strongly advised against, even for individuals trying to lose a few pounds. You will only become run-down and unable to continue your training regimen, in addition to playing havoc with your body’s metabolic processes.
Exercise scientists recommend athletes eat 1-1.5 g of carbohydrates/kg of body weight as soon as possible after training. Additional feedings should occur every two to four hours thereafter.
The type of carbohydrate you take in also determines the rate of glycogen synthesis. High-glycemic-index foods induce greater glycogen synthesis than low-glycemic-index foods. Thus you may want to look for a recovery drink with sucrose or glucose (high-glycemic-index) rather than fructose (low-glycemic-index).
*Side Note: Insulin Enhancers – Insulin has been called the “master recovery hormone” for the role it plays in the exercise recovery process. Among the tasks insulin performs are:
Transport glucose into muscle and liver tissues, where it is stored as glycogen
Stimulates the release of the enzyme glycogen synthase, which helps convert glucose to glycogen
Stimulates the transport of amino acids into the muscle cell, thus speeding the protein rebuilding process
Blunts the rise in the catabolic (muscle destroying) hormone cortisol following exercise.
Research shows that a beneficial insulin release can be achieved by the addition of protein and the amino acid arginine to the post-exercise carbohydrate/electrolyte drink. The protein should be 1/4 the amount of carbohydrates in the drink. More than that may slow gastric emptying and delay the nutrient and water uptake into the bloodstream.