Dehydration in Sports
We all know that we lose water and electrolytes (dissolved "salts") when we exercise, although we may just think of the loss as "sweat"or "perspiration" and that the more strenuous the activity, the more we'll lose. Many also know that this loss can cause muscle cramps and, the next day, muscle aches and soreness. Most active people also notice that, as they get dehydrated, even before they feel thirsty they just don't do as well. For many years exercise physiologists have insisted that "all you need is water; you don't lose enough electrolytes to affect your performance" and "water is absorbed faster than anything else" even though both statements are contrary to the experiences of most athletes. And, should you push yourself too far, they're not going to give you "plain water" in that IV.
When cells do their work, changes in electrolyte concentrations inside and outside the cell take place; often the changes that are causing the cellular activity, or just changes that are a result of the activity. For example, in a resting muscle cell, there is a higher proportion of potassium ions inside the cell than outside, and the reverse is true for sodium ions. When the muscle contracts, potassium escapes from the cell and sodium diffuses in. For the cell to relax again, the excess sodium must be pumped out and potassium pumped into the cell, all of which require energy from glucose in the cell, while more energy is also used to "jack" the cell into the stretched or "relaxed" condition. The cell must have enough water and the proper ions in the immediate vicinity and in the cell for these transfers to take place. But, circulation and the loss of water (and the dissolved electrolytes) in the perspiration necessary to keep us from overheating also causes water and electrolytes to be lost from the active cells. Soon these losses begin to affect the cells' ability to recover and you begin to falter, muscles begin to tighten up and, eventually, to cramp and they'll tear if you try to continue your efforts. The primary cause of pulled muscles is dehydration; that tight muscle yesterday will often tear with a sudden effort today. For example, tennis players getting dehydrated one day will feel a little tight the next if they don't replace the water and electrolytes and, in an abrupt lunge, the muscle will tear. Athletes in sports that involve periods of inactivity and sudden intense efforts, like baseball players abruptly going after a ball or lunging into a run to the next base, are especially prone to muscle pulls; circulation to the muscles is diminished while they are inactive and, if they are getting dehydrated, the abrupt activity will tear muscle, tendon or ligament fibers. Muscle cells are not the only cells that suffer from dehydration and electrolyte loss; all cells are affected and most especially the cerebral cortex, even though you may not be aware of it; the very effects that help to keep you from noticing this. As a matter of fact, the very first noticeable symptom of dehydration is diminished mental acuity; you don't think as clearly, reaction times are slowed, and judgment and quick decisions are affected long before you even feel thirsty. For most, the first effect noticeable is the inability to recall a name or word that you know or you may stumble over the word, often coming up with another term that is not quite what you wanted.
For example, back to the tennis player, they will be a little off in reactions, placing shots or decisions that can cost a match, even before their muscles begin to feel tight. The next symptom is irritability, often at about the same time that the muscles begin to function less smoothly. For bicyclists, the stroke rhythm gets off; in tennis, softball or baseball, timing, reactions and judgment are also off. Can you see how your performance, whatever your sport, can be seriously affected even before you begin to feel any muscle tightness?
Sports drinks were supposed to be designed to replace these vital electrolytes and the water to prevent and relieve the muscular effects. However, they turn out to be designed to sell to the general public who would like to think that they are getting something that will help them play "like the pros." Therefore, they have to have so much flavor and sugar to taste good that absorption into the system is not only delayed, but water is actually pulled from the body into the stomach or intestines. Energy drinks contain even more sugars and, usually, loads of complex carbohydrates that, while emptying from the stomach fairly quickly, must be digested in the intestines, pulling even more water from the system; definitely not what a dehydrated athlete needs! If you are already dehydrated, almost to the point of a muscle cramping, a few swallows of one of these concentrated drinks will cause water to be pulled from muscles all over the body resulting in "whole body" or "chain-reaction" muscle cramps. This is what happened to swimmer Amy Van Dyken after her first race of the Atlanta Olympics. Many sports drinks also contain far too much sodium (some have five times as much sodium as potassium) which causes you to lose your own potassium reserves, keeping up with the sodium losses. Sodium also pulls water from circulation into the tissues, effectively removing the water from use in circulation, cooling the body and muscle function.