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08/29/2003 Archived Entry: "Friday - August 28, 2003 (Hyponatremia & Rhabdomyolysis)"
Ladies and Gentlemen,
I would like to introduce to you the Weblog’s first technical paper, written by APRR’s Yong H. T., through his own expertise and opinion. His paper hits home to APRR, as at least four of us had a direct and self-impacting experience from that of the topic of his words, during last year’s A2A. Please read this paper carefully, and take its contents to heart, because I, as one of the casualties of Rhabdomyolysis during last year’s event, can attest to the severity of its consequences.
The Proper Intake of Sodium-Concentrated Fluid for Events of Physical Extra-Endurance Exercise - Such as A2A
By Yong H. T., MD, PhD.
(Physical Medicine and Rehabilitation Specialist)
In physical endurance events and extreme exercises of physical endurance, the average athletic body loses about 1.52 liters of fluid per hour. An amount of fluid loss was initially determined through a scientific study; where, the participants were marathon runners and had participated in the Boston Marathon (26.2 miles) race [Buskirk & Beetham, 1960]. In that initial study, the amount of fluids that the participants had consumed was not carefully monitored. However, it can now be surmised that the actual loss of fluid from their bodies was even greater than reported.
Today, a number of subsequent studies have found that the amount of fluid loss through the body (i.e. breathing and perspiration/sweating) can fluctuate with changes in ambient temperature, humidity, training adaptation & acclimation to the environment, as well as in an individual’s own body weight. From the various studies, and through a medical perspective, three factors must be taken into full consideration for the proper replacement of a body’s fluids:
1. The VOLUME of fluid taken into the body,
2. The extent of OSMOLARITY of this fluid with the body, and
3. The proper BALANCE of ELECTROLYTES within the body itself.
VOLUME: A proper volume of fluid intake is necessary in order to maintain an adequate circulation of blood, as well as to perfuse body organs and systems for their proper functions.
OSMOLARITY: Is the concentration and/or density of molecules or ions that are dissolved in a certain type of fluid.
ELECTROLYTES: Are both ions and anions. They are integral in providing osmolarity, and maintaining the "excitability" of its muscular and nerve systems.
The composition of the human body is approximately 70% fluid. These fluids are distributed into two major compartments:
1. Inside the body’s cells, and
2. Outside of the body’s cells.
The osmolarity in each compartment maintains the correct volume of fluid inside that particular compartment. If the osmolarity outside the cells is low, water will therefore be drawn into the cells. If excessive water enters into a particular cell, that cell will expand and burst (like a balloon). In this situation, excessive intake of pure water, by endurance type athletes, has shown to result in frequent hyponatremia (low sodium in the blood stream- which in turn adversely affects cellular osmolarity). Hyponatremia in turn may cause abnormal electrophysiological functions of muscle mass and the nerve system. Rhabdomyolysis (Rhabdo) is a result of this situation. Rhabdo is the literal destruction of those muscle cells that are associated with frequent electrolyte disturbances (i.e. hyponatremia). If the amount of dead or dying muscle cells are massive enough in number (as they enter into the bloodstream), then the body's kidneys will become adversely affected, if not clogged. Interestingly, a greater incidence of hyponatremia has been found to occur in women than in men.
The only way to minimize the risks of hyponatremia is through the proper replacement of fluids that are known to contain high concentrations of sodium. Published in the August, 2003 issue of British Journal of Sports Medicine, Twerenbold and colleagues studied the prevention of hyponatremia by comparing the effects of various concentrations of sodium, within drinking fluids. In this study, thirteen female athletes performed three segments of running exercises. Each exercise segment had a duration of four hours. During the exercise, the subjects consumed one liter of fluid per hour. The intake of fluids for this study were as follows:
1. One trial running exercise with a high concentration of sodium (680mg/l),
2. One trial exercise with a low concentration of sodium (410mg/l), and
3. One trial with only water - as a control.
The results of the above study revealed that liquids with a higher concentration of sodium (680 mg/l) permitted a lower incidence of hyponatremia (i.e. 46% of the participants), than did the liquids with a lower concentration of the same sodium (410 mg/l) (i.e. 69% of participants). The intake of water, exclusively, resulted in the highest incidence of hyponatremia (i.e. 92% of the participants). The study therefore concluded that a replacement of at least 680 mg/h of sodium is recommended for similar endurance activities.
Unfortunately, there are no liquid products on today's market that approximate this level of sodium concentration. The closest product known to be offered to the public is that of Gatorade, which contains a 458 mg/liter concentration. In terms of preventing the effects of hyponatremia, Gatorade, and the various other sports drink products are never the less superior to the consumption of pure water, exclusively. Moreover, the various commercial products contain the benefit of carbohydrates, which refuel the muscles.
Since the commercial industry's highest sodium concentrated product, Gatorade, does not approximate the body’s ideal concentration of sodium, one solution is that of a homemade remedy. Such a remedy can be created very simply and easily. The following is the established correct formula: Add two (2) grams of table salt (sodium chloride, equivalent to 793 mg of sodium) to one (1) liter of water.
It is not currently known whether an even greater concentration of sodium would be more beneficial for athletic endurance events. There may never be a single type of fluid that best fits all athletes. Athletes who are less well trained, are female gender, or those with a larger body surface area generally require a greater sodium intake than those who are well acclimated, male, or else lean in body mass.
Since the concentration of sodium found in perspiration (i.e. sweat) is about half of the serum sodium concentration, and the body has additional water loss through breathing, the sodium concentration taken into the body should not exceed that of half-normal saline. In other words, when making a homemade remedy, do not use more than 4.5 grams of table salt in each liter of water (i.e. over twice the stated amount).
Even though sodium is extremely important for endurance events, you must consider it equally important, if not mandatory, to consume foods with a high carbohydrate value. These foods must be consumed before, during, and after the endurance event. By properly doing so, you will: 1) maximize the storage of muscle glycogen; 2) prevent hypoglycemia; as well as, 3) optimize post-event repletion of endogenous carbohydrates. But keep in mind that a high-fat concentrated diet has not shown to benefit an athlete's performance. Only a diet with a high carbohydrate value can properly maximize such performance.
In summary, it is strongly recommended to drink plenty (at least 1 liter per hour) of salty water, preferably containing 793 mg of sodium (i.e. 2 grams of table salt) in each liter of water, and to eat sweets before, during and after exercises. Do this especially for physical endurance activities, such as A2A.
(As a footnote): A slight overload of sodium is a much lower risk to the body, as well as less dangerous, than is a deficit of sodium. Regarding potassium, many people are generally misled about the balance of potassium, as read on container labels.
Yong H. T. at an APRR event.