Importance of proper hydration during exercise

Staying hydrated is particularly important during exercise. Adequate fluid intake is essential to comfort, performance and safety. The longer and more intensely you exercise, the more important it is to drink the right kind of fluids.

Dehydration Decreases Performance
Studies have found that athletes who lose as little as two percent of their body weight through sweating has a drop in blood volume which causes the heart to work harder to circulate blood. A drop in blood volume may also lead to muscle cramps, dizziness, fatigue and heat illness including:
Heat Exhaustion
Heat Stroke

Common Causes of Dehydration In Athletes
Inadequate fluid intake
Excessive sweating
Failure to replace fluid losses during and after exercise
Exercising in dry, hot weather
Drinking only when thirsty

Hydration Needs for Athletes
Because there is wide variability in sweat rates, losses and hydration levels of individuals, it is nearly impossible to provide specific recommendations or guidelines about the type or amount of fluids athletes should consume.

Finding the right amount of fluid to drink depends upon a variety of individual factors including the length and intensity of exercise and other individual differences. There are, however, two simple methods of estimating adequate hydration:

Monitoring urine volume output and color.
A large amount of light colored, diluted urine probably means you are hydrated; dark colored, concentrated urine probably means you are dehydrated.

Weighing yourself before and after exercise.
Any weight lost is likely from fluid, so try to drink enough to replenish those losses. Any weight gain could mean you are drinking more than you need.

Temperature
Exercising in the heat increases you fluid losses through sweating and exercise in the cold can impair you ability to recognize fluid losses and increase fluid lost through respiration. In both cases it is important to hydrate.
Sweating. Some athletes sweat more than others. If you sweat a lot you are at greater risk for dehydration. Again, weigh yourself before and after exercise to judge sweat loss.

Sports Drinks?
Sports drinks can be helpful to athletes who are exercising at a high intensity for 60 minutes or more. Fluids supplying 60 to 100 calories per 8 ounces helps to supply the needed calories required for continuous performance. It’s really not necessary to replace losses of sodium, potassium and other electrolytes during exercise since you’re unlikely to deplete your body’s stores of these minerals during normal training. If, however, you find yourself exercising in extreme conditions over 3 or 5 hours (a marathon, Ironman or ultramarathon, for example) you may likely want to add a complex sports drink with electrolytes.

General Guidelines for Fluid Needs During Exercise
While specific fluid recommendations aren’t possible due to individual variability, most athletes can use the following guidelines as a starting point, and modify their fluid needs accordingly.

Hydration Before Exercise
Drink about 15-20 fl oz, 2-3 hours before exercise
Drink 8-10 fl oz 10-15 min before exercise

Hydration During Exercise
Drink 8-10 fl oz every 10-15 min during exercise
If exercising longer than 90 minutes, drink 8-10 fl oz of a sports drink (with no more than 8 percent carbohydrate) every 15 – 30 minutes.

Hydration After Exercise
Weigh yourself before and after exercise and replace fluid losses.
Drink 20-24 fl oz water for every 1 lb lost.
Consume a 4:1 ratio of carbohydrate to protein within the 2 hours after exercise to replenish glycogen stores.

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