Drink to Your Health
by Matt Fitzgerald
Every runner who's training for an important race has two great fears: getting sick and getting injured. All too often, these fears are realized. Studies indicate that each year at least 25% and possibly more than 50% of all runners suffer an overuse injury that prevents them from running for at least a few days. Other research has shown that competitive runners in heavy training are more likely to contract an upper respiratory infection than overweight couch potatoes. Most runners are familiar with various methods of illness and injury prevention, from getting adequate sleep to stretching. But one thing you rarely think about in connection with illness and injury prevention is sports drinks. That's a shame, because it's now an established fact that using a well-formulated sports drink before and during workouts can minimize and help fix damage to muscle tissue while bolstering the immune system. In other words, sports drinks aren't just for energy anymore.
Running and The Immune System
In general, cardiovascular exercise strengthens the immune system. However, individual, strenuous workouts are known to result in an acute suppression of immune system function that can last for 2-72 hours, depending on the individual and the precise nature of the workout. The primary cause of this suppression is the hormone cortisol.
Cortisol is released by the adrenal glands in response to all forms of stress. Its main function is to release amino acids from muscle proteins and transport them to the liver for use as an energy source. The release of cortisol tends to occur in the latter portion of long workouts, when the preferred energy source of muscle glycogen has been depleted. As a side-effect, cortisol suppresses immune system function by decreasing production of lymphocytes and antibodies, which are the warriors of your body's immune defense.
By drinking a good sports drink before and during workouts, you can minimize the immune suppression that comes with hard training. Research by David Nieman at Appalachian State University has demonstrated that the carbohydrate in sports drinks can combat the effects of cortisol on two levels. First of all, by taking in carbohydrate during workouts, runners are able to maintain higher levels of blood glucose, which slows the use of muscle glycogen and delays the need for the use of protein as an energy source.
In addition, carbohydrate stimulates the release of insulin from the pancreas. Insulin is a hormone that is responsible for delivering carbohydrate, in the form of glucose, to the working muscles. Insulin also neutralizes cortisol - and thereby reduces its effect on the immune system.
Running and Muscle Damage
Muscle tissue damage is the primary cause of post-workout muscle soreness and may also contribute to some running-related muscle injuries. Sports drinks can help manage two causes of muscle tissue damage.
The first is oxidative stress, also known as free radical damage. Oxygen is a highly reactive type of molecule. During intense exercise, your rate of oxygen consumption increases dramatically. Many of the individual oxygen molecules consumed during exercise lose an electron and become free radicals inside the body. These molecules are extremely unstable; they regain stability by pilfering an electron from a muscle cell membrane, thereby damaging the muscle cell.
The hormone cortisol has also been linked to muscle cell damage. Cortisol is released when muscle glycogen runs low and the body needs to break down more protein for energy. Cortisol does the breaking, and destroys muscle proteins in the process. Sports drinks can delay and reduce this action in the same way they protect the immune system: by conserving muscle glycogen and by stimulating insulin release.
Rebuilding Muscle Protein
Sports drinks that contain a certain amount of protein in addition to carbohydrate are even more effective in combating exercise-induced muscle damage. Like carbohydrate, protein stimulates insulin release. When protein is added to carbohydrate in a sports drink, more insulin is released and a greater amount of cortisol is neutralized.
This increased insulin response also results in faster delivery of glucose to the working muscles. When glucose gets to the muscles faster, the glycogen fuel that is stored in the muscles is conserved. The longer glycogen lasts, the less your body needs to rely on breaking down muscle protein for energy. What's more, the protein in the few sports drinks that contain it works to quickly rebuild the muscle protein that is broken down during a workout.
In a study performed at the University of Texas, subjects who consumed an amino acid-carbohydrate supplement immediately before exercise synthesized more new muscle protein afterward than subjects who consumed the same drink immediately after the workout. (Amino acids are the building blocks of protein.) A sports drink should not contain too much protein, however. When excessive amounts of protein are consumed with carbohydrate, the stomach empties more slowly and, as a result, insulin levels stay lower and glucose and protein are delivered to the muscles at a slower rate.
Current research indicates that the ideal carbohydrate-protein ratio in a sports drink is 4 to 1. You can reduce oxidative stress by consuming a diet high in antioxidant vitamins and minerals such as vitamins A, C and E, beta-carotene and selenium. Several studies have shown that vitamin C supplementation reduces post-exercise muscle soreness in athletes and that vitamin E supplementation has a similar effect on indicators of post-exercise muscle damage. One way you can get extra antioxidants in your diet is by using a sports drink that contains them in large amounts.
New Drinks, New Benefits
Sports drinks were originally designed to prevent dehydration and supply energy during exercise, and they do this well. But a new generation of sports drinks (see listing below) that contain antioxidants and a 4 to 1 ratio of carbohydrate to protein can also help prevent injuries by reducing muscle tissue breakdown and accelerating the rebuilding of muscle protein. These drinks can reduce the risk of infection by reducing the immune system suppression that normally occurs after hard workouts. Simply put, by using this type of sports drink before and during each workout, you can improve your odds of making it to the starting line healthy.