Sports Nutrition Review 1-2, Hydration Status & Electrolytes

Posted by on Jan 31, 2013 in Nutrition, Review Topics | 0 comments

It’s common knowledge that hydration is important. Water affects performance more than any other nutrient. But what we’re concerned about in this post, is what details of hydration we need to know for the CSCS exam.

Voluntary Dehydration
Most athletes will only replenish 2/3 of lost fluids after exercise. This phenomenon, called voluntary dehydration is one that strength and conditioning professionals need to be aware of and encourage athletes to fully replenish their stores after exercise.

When does fluid loss lead to decreased performance?

  • A 1% loss in body weight of water leads to an increase in core temperature, however does not have a measurable effect on performance.
  • A 3-5% loss of body weight results in cardiovascular strain and impaired ability to dissipate heat, leading to performance degradation
  • At 7% loss, collapse is likely.

For example, a 200lb athlete may lose 10lbs while exercising in the heat (5% loss).  This is fairly common, but should be recognized as detrimental to performance.

Monitoring Hydration
A very accurate way to monitor hydration status is by weighing the athlete before and after exercise.  Each pound lost represents 0.5L of fluid loss and must be replaced before the next training session.

Electrolyte Replacement
Electrolytes lost in sweat are higher in untrained individuals vs. trained athletes.  The average concentration of sodium in sweat is 1.15g/L, with concentrations ranging from 0.46 to 2.3g/L (a big range).  Given that the average American salt intake is 4-6 grams per day, electrolyte loss in some athletes is common and can lead to cramping.  Additional salting may be necessary, as well as potassium rich foods such as bananas, potatoes, strawberries, meat, and milk.

In my next post, I’ll go over the general recommendations for hydration before, during, and after training sessions.

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