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Tennis Association

Drop Shots from the Tennis Association
By Paul Danner

In last month's Drop Shots we covered the important health tip of keeping hydrated when playing tennis, especially during these intense hot summer days.  Now let's discuss the effects of not drinking correctly as presented by


What is hyponatremia? Can it happen to me?

Yes! Hyponatremia means ‘water intoxication’. More specifically, it refers to a condition of low (hypo) sodium (na) content in your body as a result of drinking too much (yes too much) water.  The sodium in your bloodstream enables the body to regulate fluid balance. When the electrolyte balance is disturbed, the body can absorb more fluid than your kidneys can excrete. What is the outcome? Milder cases are characterized by fatigue, nausea, and headache. In sever cases, drinking too much water while at the same time losing excessive amounts of sodium through sweat can lead to serious illness that results in seizures, coma and emergency hospitalization. Even professional tennis players have experienced this after playing prolonged matches in hot conditions.  Knowing enough to realize that it was important to re-hydrate, they simply drank lots of water - and suffered the consequences. The lesson - ensure that you drink fluids that will replace lost electrolytes as well as just the water content of sweat..

Why it’s not cool to get dehydrated

Dehydration is basically a condition where the body has an abnormally low water content. A healthy body consists of mainly water - approximately 65% in fact. It should not be surprising, therefore, that any disturbance of the balance of such a large part of the body should have a great impact on the health of the body. We all sweat but, because we have become so good at controlling our environment to maintain a comfortable temperature (through buildings and space heating and cooling to protect against climate extremes;  clothes design; etc.) the amount is usually so small that it evaporates from the skin quickly and without being noticed.

The body uses sweating to regulate body temperature. Warm-blooded creatures need to keep their body temperature within a very narrow and regulated temperature range to avoid discomfort and even life-threatening breakdown of functions. The optimum temperature for humans is 98.6 degrees. Even a few degrees higher or lower produces ill effects. Most of the skin contains sweat glands – small ducts that allow moisture to escape from the body. When the body senses that it is overheating, it opens the sweat glands and allows moisture to flow out. The moisture carries the body’s heat to the surface of the skin where it evaporates on contact with the cooler surrounding air. Those of you who remember your physics classes from school will remember that the process of evaporation (a liquid changing into a vapor) requires energy. The energy source in this case is heat energy. So, as the moisture (sweat) from our body evaporates into vapor, heat is absorbed from the body and cools us.

Liquid (the blood) is also used as the carrier of nutrients and oxygen to the muscles. When you sweat excessively – and thereby lose too much fluid - your heart has to work much harder to deliver nutrients and oxygen to your exercising muscles and it becomes much more difficult to keep your body from overheating which will lead to heat illness if the symptoms are not recognized. 

It is therefore vital to maintain the amount of liquid that is available to the body. The more you sweat, the more you need to replace the lost liquid in order to maintain your body’s ability to regulate its temperature.

Learn to recognize these early warning signs of dehydration:

  •             Dark yellow, often smelly, urine (generally small quantity)
  •             Sudden onset of extreme fatigue
  •             Headache
  •             Dizziness
  •             Cramps

Initially, you will notice that your urine output is low, very dark yellow, and often strong smelling.  If you are exercising, you will become tired quickly or suddenly and your performance will deteriorate.  If you do not take counter measures quickly, you will probably start to cramp from the fatigue. These cramps will quickly progress from a little twinge to uncontrollable and totally incapacitating cramps. Other bad things will also occur quite quickly – you’ll get dizzy, light-headed, become uncoordinated, and feel cold even though you are actually very hot. This is classic heat exhaustion. If nothing is done to cool and rehydrate your body, you will lose consciousness and need immediate hospital treatment.  Sounds like fun, huh!?

Enjoy tennis but follow good hydration practices during these hot summer days and always remember to...Stay Inside The Lines!