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by Dr. Aparna Pandit
B.Sc. Home Science, M.Sc. Foods & Nutrition, Ph.D. Food Science and Nutrition
Mar 2003


Athletes who train hard frequently complain about "energy drain" and fatigue. Because they are regularly reminded to consume adequate fluids and fuel to minimize early fatigue and to maximize performance and recovery. Having more energy can improve oneís capacity for work, a very desirable characteristic for all and especially for active individuals (Bonsi, 2002). So athletes will always be attracted to products that claim to have performance-enhancing effects.

Following training & competition an athlete's glycogen stores are depleted. In order to replenish them the athlete needs to consider the speed at which carbohydrate is converted into blood glucose and transported to the muscles. The rapid replenishment of glycogen stores is important for the track athlete who has a number of races in a meeting. Sweating is the way in which the body maintains it's core temperature at 37 degrees centigrade. This results in the loss of body fluid and electrolytes (minerals such as chloride, calcium, phosphate, magnesium, sodium and potassium) and if unchecked will lead to dehydration and eventually circulatory collapse and heat stroke. Among the important electrolytes are sodium, chloride, potassium, magnesium and calcium, which are often included in glucose-containing electrolyte drinks. Sodium helps maintain proper body fluid volume. A weight loss of greater than 2% resulting from dehydration can fatigue the athlete, cause a loss of concentration, increase heart rate and lead to circulatory collapse. Small amounts of sodium improve water and glucose absorption in the body. Glucose electrolyte solutions maintain body fluid balance better than glucose drinks alone. Sodium also plays an important role in muscle contraction and in the condition of nerve impulses. A slight deficiency of sodium may impair performance, cause nausea, vomiting, headache, loss of appetite, muscular weakness and leg and abdominal cramps.

The electrolyte requirements of most physically active people can be more than adequately met by consuming a balanced diet. Imbalances may occur under special circumstances such as during the initial stage of acclimation to a hot environment, during prolonged repeated exposure to exercise and heat, and during exercise lasting several hours. Electrolytes, especially sodium and potassium, in a drink will reduce urine output, enable the fluid to empty quickly from the stomach, promote absorption from the intestine and encourage fluid retention. For PR-seeking runners, sports drinks can be a quick-and-easy way to hydrate and refuel on the fly. Supplying fluid, carbohydrate (the body's preferred fuel during exercise) and electrolytes, sports drinks and energy gels should be an integral part of any runner's nutrition program.

With regard to fluid absorption, there are two main factors that affect the speed at which fluid from a drink gets into the body. They are the speed at which it is emptied from the stomach and the rate at which it is absorbed through the walls of the small intestine. The higher the carbohydrate levels in a drink the slower the rate of stomach emptying. Isotonic drinks (These drinks are the choice for most athletes) with a carbohydrate level of between 6 and 8% are emptied from the stomach at a rate similar to water. However Hypertonic fluid drinks with High level of carbohydrate are used to supplement daily carbohydrate intake normally after exercise to top up muscle glycogen stores. In ultra distance events high levels of energy are required and Hypertonic drinks can be taken during exercise to meet the energy requirements. If used during exercise Hypertonic drinks need to be used in conjunction with Isotonic drinks to replace fluids.

Water is the most common beverage consumed. However, Drinking plain water causes bloating, suppresses thirst and thus further drinking. It stimulates urine output and therefore is inefficiently retained. A poor choice where high fluid intake is required. Water contains no carbohydrates or electrolytes.

Majority of the Sports drinks are designed for use during exercise typically contain more than one type of carbohydrate. Check the ingredient list and youíll find a combination of simple carbohydrates (sucrose, glucose and fructose) and complex carbohydrates, such as glucose polymers and maltodextrins. The better-formulated (and tasting) drinks usually contain both, with a higher percentage of complex than simple carbohydrates.(Labels list ingredients by weight from most to least). While hydrating with water should be adequate, the rapidly absorbable carbohydrate supplied by a sports drink can provide the extra energy needed to mount a strong finishing burst.

During long races, such as half-marathons and marathons, itís imperative that competitors drink a sodium-containing beverage to avoid the potentially life-threatening condition known as hyponatremia (low blood sodium level). Middle and back-of-the pack runners should especially rely on a sports drink rather than drinking plain water. Running at a slower pace often translates into more opportunities to drink. This can result in a dangerous disturbance of the bodyís fluid-to-sodium ratio if a runner ingests copious amounts of plain water without also attending to sweat-induced sodium losses. If muscle cramps have been holding you back, experiment with a sports drink that provides the recommended amount of sodium at least 110 milligrams per eight-ounce serving. While the exact cause of muscle or heat cramps is unclear, most experts believe salt depletion plays a critical role.

Fluid replacement is a must before, during and after activity in order to safeguard the athletes' health and for optimizing athletes performance. The ideal fluid replacement beverage is one that tastes good to the athlete, does not cause gastrointestinal discomfort when consumed in large quantities, promotes rapid fluid absorption and maintenance of extracellular fluid volumes and provides energy to working muscles. Research states that sports drinks containing 6-8 percent carbohydrate solution actually enter the bloodstream as rapidly as plain water. The 6 percent carbohydrate beverage not only entered the blood as fast as water but, was associated with improved exercise endurance. Both drinks had the same favorable influence on cardiovascular and thermoregulatory function. The key is to experiment with different brands and flavors in training to find the winning combination to use on race day.

Other than water, most of the products marketed as energy and sports drinks contain carbohydrate and caffeine as their principal ingredients the carbohydrate to provide nutrient energy and the caffeine to stimulate the central nervous system, but they may also contain a wide variety of other ingredients. The other ingredients generally found in energy and sports drinks are taurine, ribose, ginseng, carnitine, guarana, inositol, vitamins, Schizandrae, Glutamine, Galactose, protein, chromium, green tea, Ginkgo biloba, Pyruvate, royal jelly, bee pollen, damiana, Stabilized oxygen, aloe vera, medium-chain triglycerides, borage oil, branched-chain amino acids, electrolytes. All these ingredients are claimed to be the power enhancers, but most of them are not proven scientifically. Since there is little or no evidence of athletic performance effect by these ingredients, athelets should be cautious before consuming energy and sports drinks. Examine sports drinks carefully and think before buying. Before buying a sports drink, be sure to check for nutritional/ingredient information, claim given by the company, dosage etc. Avoid herbal additives if you are taking prescription medications because there may be adverse interactions among the herbal chemicals and your medicine. Avoid products containing ephedra, yohimbe, and mate, all of which are unsafe.

Sports drinks are not adequate substitutes for the time, training, rest, recovery, and fueling required for sports. Athletes must take the responsibility for what goes into their bodies, which includes being informed as well as cautious about dietary supplements. Eating an optimal amount of calories and being well hydrated are certainly critical components of athletic success. Sports drinks can supply energy and fluid, and they may have a role to play in carbohydrate loading during recovery from exercise. But sports drinks typically are not optimally formulated to work best to improve strength, speed, stamina, and other requirements for sport performance when consumed shortly before or during exercise.


Leslie Bonci, M.P.H., R.D. Director, Sports Medicine Nutrition, Department of Orthopedic Surgery and the Center for Sports Medicine, University of Pittsburgh Medical Center, Nutritionist, Pittsburgh Steelers, Pittsburgh, Pennsylvania, Sports Science Exchange 84, VOLUME 15 (2002) NUMBER 1

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