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Exercise Hydration Needs – Customizing Individual StrategiesExercise hydration needs must be met in order to complete the workout without becoming dehydrated which hinders exercise performance. Once dehydration occurs then muscle fatigue with muscle cramps which can be painful and loss of coordination occurs. Exercise generates heat and heavy exercise can increase heat production. When body heat increases then sweating occurs in order to cool the body down as the sweat evaporates from the surface of the skin. Exercise hydration needs should be addressed immediately before, during and after exercise.
The rate that the body sweats is affected by: • The temperature of the environment whether it is extremely hot or extremely cold • By humidity with higher humidity producing a higher rate of sweat production but with decreased efficiency of evaporation from the skin surface • The type of clothing worn for exercising • The individual’s level of fitness • The initial balance of fluid in the body Blood must flow to the skin to keep the body from overheating, so that evaporation of sweat can dissipate heat. The demand for blood flow to the skin for cooling competes with the demand of the cardiovascular system for blood flow to deliver fuel in the form of ATP to working muscles. If the body is allowed to become dehydrated this adds stress to both systems making each work less efficiently. This is why it is crucial to hydrate both before exercise begins and during exercise. Signs of dehydration include: • An elevated heart rate at a given exercise intensity • An increased rate of feeling that you are working harder than you really are • A decrease in performance • A feeling of lethargy • More concentrated urine output • Decrease in the frequency of urination • A loss of appetite Drinking fluid during exercise at a rate to balance sweating and fluid loss will offset these symptoms. Those who are physically active have to train themselves to consume adequate amounts of fluid before, during, and after exercise, hydration shouldn’t stop after exercise. Fluid consumption should be customized to the individual, since fluid needs are based on the individual’s electrolyte losses, body weight, genetic makeup and metabolism. There is no one size hydration fits all. Hydration Strategy – Before, During, and After Exercise – Why? Hydrating before exercise is designed to begin the workout with normal plasma electrolyte levels and it is recommended that hydration begin at least four hours before exercising begins. By drinking fluids with sodium thirst will be stimulated and the body will retain needed fluids. By hydrating during exercise the goal is to prevent excessive dehydration greater than 2% of body weight and excessive changes in electrolyte balance. By hydrating after exercise fluid and electrolyte status will return to normal quicker if hydration continues after exercise has been completed. Hydration Choices The question is whether water, sports drinks or other beverages are best as choices for hydration before, during and after exercise. During exercise that lasts less than 60 continuous minutes, water is a great replacement fluid to replace the fluid lost through sweating and can help to offset a rise in body temperature. As exercise continues beyond 60 continuous minutes the stores of muscle and liver glycogen become depleted. At this stage consuming fluids that contain carbohydrate and sodium can delay fatigue and promote fluid retention. At this stage sports drinks which contain glucose or sucrose along with electrolytes may work well. Drinks such as fruit juice and soft drinks are not a good choice because the primary sugar is fructose not glucose the primary energy source and these types of drinks empty from the stomach slower and may cause abdominal cramping, rather than moving along quickly to energy production sites. Alcohol should never be used since it slows reaction time, impairs coordination and upsets balance, and its diuretic action speeds up dehydration and can impair the regulation of body temperature. By addressing exercise hydration needs at each stage of the workout dehydration that can hinder peak performance as well as present health risks can be avoided.
For other information on nutrition including exercise hydration needs some great references are: • Nutrition – Fourth Edition by Paul Insel, Don Ross, Kimberley McMahon, and Melissa Bernstein
Exercise and Vitamins
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