Regular exercise is integral to our health, but one must exercise properly to avoid inadvertently doing
harm. Often this means proper clothing, shoes, and warm ups. Equally important, however, are the risks of dehydration and depletion of the body’s carbohydrate stores.
We maintain our core body temperature by sweating. This will lead to a loss of water, electrolytes and minerals, which might prove costly to performance if not compensated for.
Witness the effect of fluid loss upon performance
| 2% body weight lost as sweat | Impaired performance |
| 4% lost | Capacity for Muscular work declines |
| 5% lost | Heat Exhaustion |
| 7% lost | Hallucinations |
| 10% lost | Circulatory collapse and “heat stroke” |
Carbohydrates are stored as glycogen in the liver. When called upon, they are released in the form of glucose, which is a highly efficient source of energy. It’s efficiency stems from less oxygen needing to be expended during glucose utilization than with either protein or fat.
During rigorous exercise, carbohydrates can be depleted to such an extent that within two hours muscle performance can be impaired. Recovery of carbohydrate stores (glycogen) will normally require 24 to 48 hours. An athlete who consumes carbohydrates before, during, and after exercise will largely prevent blood glucose from plummeting, and also will preserve glycogen stores.
Obviously it’s not realistic to presume one can eat during exercise, so formulated beverages which provide carbohydrates are an excellent option. According to the American College of Sports Medicine, performance is improved by consuming carbohydrate-containing beverages at a rate which will provide 25 to 30 grams of carbohydrate each hour. This translates into consuming fluids with 6 to 8% carbohydrates at a rate of 4 to 8 ounces every 15 to 20 minutes of exercise. Five or six swallows will yield 4 to 8 ounces. A good start is to consume 10 to 12 ounces just before exercise.
Not all forms of carbohydrate are appropriate. Glucose and Sucrose are good sources, as they are, if in low concentration, absorbed as easily as water. The best concentration is in the 6 to 8% range. It’s felt that higher concentrations impede liquid absorption, however sustained exercise for longer than four hours may require such high concentration formulas. Up to 15 % concentrations have been found to improve such sustained performances versus 5 %, without significant slowing of absorption.
Fructose is not a good source of carbohydrate. Fruit juices are comprised of fructose, and accordingly they are regarded as inferior sources of hydration and energy during exercise. Fructose reduces the rate of water absorption, so that cells have a delay in rehydration. Furthermore, it cannot be metabolized rapidly enough to spare liver carbohydrate (glycogen) stores. Finally, fructose often causes gastrointestinal distress and even diarrhea if consumed during exercise.
For most exercise regimens, the quantity of electrolytes and minerals lost is not significant, so that a sports drink is most important as a hydration and carbohydrate source. With prolonged exertion, exceeding four hours, the electrolyte and mineral composition do become important. For less rigorous exertion, those elements have some value in that they speed up absorption.
The next time you exercise remember that if your exertion is for less than one hour, water alone will suffice. If you exercise for longer than an hour, a sports drink with 6 to 8% carbohydrate in the form of glucose or sucrose is best. This is typical of the most popular sports drinks we see at the grocery store. Consume liquids in the quantities discussed above. For those exerting for longer than four hours, one might consider a higher concentration, in the 10 to 15% carbohydrate range.
Unlike the carbohydrate concentration, the actual amounts of electrolytes and minerals (e.g. calcium, phosphorus, magnesium) in sports drinks available at grocery stores are not that important. By remaining aware of your hydration and energy needs, you can enjoy yourself amidst the beauty of our special state.


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