In better understanding these electrolytes and their significance relating to the subject matter, it is accurate to say that Potassium is the electrolyte that pulls fluids into the muscles while Sodium pulls water out of the muscles. When sodium is more concentrated outside the muscle than the potassium is inside the muscle water shifts out of the muscle (undesirable). This will cause cramping and heat injuries. When sodium is less concentrated outside the muscle than the potassium is inside the muscle water shifts into the muscle (desirable).
An ongoing chemical reaction called the sodium/potassium pump works continuously in an effort to maintain a balance of these electrolytes. In fact, 2/3 of all the energy being used at rest is needed by this pump to maintain this crucial water balancing act. Moreover, be aware that water is also brought into the muscles along with carbohydrates (Insulin-carried glucose), at a ratio of 3 to 1. This is a contributing factor to muscle size increase during carbohydrate loading.
There is no established dietary requirement for sodium but it is generally observed that the usual intake far exceeds the need. The average American ingests 6-18 grams of sodium chloride each day. The National Research Council recommends a daily sodium chloride intake of 1 gram per kilogram of water consumed. An excess of sodium ingestion may cause an increased amount of potassium to be lost in the urine. A prolonged abnormally high amount of sodium in the body will result in fluid retention accompanied by dizziness and swelling of areas such as the legs and face. An intake of 14 to 28 grams of salt daily is considered excessive. It should be known that diets consisting of excessive amounts of salt contribute to the increasing incidents of high blood pressure. The simplest way to reduce sodium intake is to eliminate the use of table salt.
It is generally correct that blood concentrations of sodium, found in salt, is directly related to the regulation of safe body fluid levels as a part of the process previously discussed. Another benefit to the presence of sodium is the re-absorption of water (otherwise excreted) in the kidneys.
While there are various neurotransmitter and hormonal actions that play vital roles in this delicate balancing act, water intake and sodium level manipulation are the only means by which to consciously attempt to control fluid levels (without physician assistance and/or the use of prescription dose medication).
At first glance, the ingestion of large amounts of sodium would appear to be a must for any dehydrated condition, regardless of its cause. This is simply not the case, especially in regard to exercise induced fluid loss. During exercise, especially in a warm environment, water loss is attributed to perspiration, increased water dissipation due to heat generated during accelerated chemical reactions, increased respiration, and lastly, water losses from inside working muscles due to the friction caused by increased contractile component movement. Significant amounts of sodium (3.0 to 5.0 grams) ingested less than 1 hour prior to the performance of intense and/or prolonged activity in hot and humid climates, should be avoided. The basis for this recommendation lies in the complete understanding of the above sodium concentration concept as touched upon below.
If the vascular system is maintaining a certain concentration of sodium throughout, and a great amount of sodium is ingested in a single dose just prior to, or during exercise, the vascular system will immediately direct fluid to the localized area where the sodium is now too concentrated (mostly in the gut) in order to “dilute” this sodium down to the normal concentration levels. This is accomplished by drawing upon “reserve fluids”, in most instances from the intramuscular areas. This temporarily pulls desperately needed water out of the working muscles, and in extreme cases, the heart, leading to severe dehydration, muscle cramping, and in the case of the heart, this short-term fluid loss could result in cardiac failure. For these reasons it is obvious that “salt tablet” use, still practiced by some coaching staffs on various levels of athletics, should be discontinued.