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Electrolytes and Bodybuilding

Electrolytes, Sports Drinks, And Fluid Absorption

There are two fluid compartments in the body. The first is Intracellular, which refers to the fluid inside the cells. The second is Extracellular, which the fluid that flows within the microscopic spaces between cells, known as Interstitial fluid, and the fluid which is in the bloodstream in the form of blood plasma.

Electrolytes are the mineral salts Sodium, Chlorine, Potassium, and Magnesium. They are dissolved in the body as electrically charged particles called ions which modulate fluid exchange within the body's fluid compartments allowing for a constant, well regulated exchange of nutrients and waste products between the cell and its external fluid environment. Sodium and Chlorine represent the chief minerals contained in blood plasma and Extracellular fluid.

The movement of water is controlled by the concentration of these electrolytes on either side of the cell membrane. For example, an increase in the concentration of Sodium outside a cell will cause water to move to it from the inside of the cell. This is why people with a diet high in salt have less defined muscles and have muscles which feel soft. The opposite is also true. A drop in Sodium concentration will cause water to move from the outside of the cell to the inside of the cell. Potassium draws water across a membrane, so a high Potassium concentration inside cells increases the cell's water content.

Much of the fluid lost through sweating comes from Extracellular fluid, predominantly from blood plasma, which therefore decreases the amount of nutrients and waste products that can pass to and from the cells via the blood plasma. This is the reason why a well hydrated athlete will always function at a higher physiological and performance level than a dehydrated one.

Sports Drinks

Hypotonic Drinks

These have a relatively low osmolality and a lower osmolality than the body's own fluids. Osmolality is a measure of the number of dissolved particles in a fluid. This means that these drinks contain fewer particles, i.e. fewer carbohydrates and electrolytes per 100 ml than the body's own fluids. As these drinks are more dilute than the body's own fluids, they are absorbed faster than plain water. Hypotonic drinks contain less than 4 grams of carbohydrate per 100 ml.

Isotonic Drinks

These have the same osmolality as the body's own fluids. This means that these drinks contain about the same number of particles, i.e. the same amount of carbohydrates and electrolytes per 100 ml as the body's own fluids. As these drinks contain the same amount of particles as the body's own fluids, they are absorbed as fast as, or faster than plain water. Most Isotonic drinks contain between 4 grams and 8 grams of carbohydrate per 100 ml.

Hypertonic DrinksThese have a higher osmolality than the body's own fluids. This means that these drinks contain more particles, i.e. more carbohydrates and electrolytes per 100 ml than the body's own fluids. As these drinks are more concentrated than the body's own fluids, these are absorbed slower than plain water. Most Hypertonic drinks contain more than 8 grams of carbohydrate per 100 ml.

Fluid Absorption

Gastric emptying is the process whereby the small intestine absorbs fluids only after they pass into it from the stomach. As a result, you need to take into account the negative effects that the ingredients in sports and other drinks have on water absorption from the digestive tract, just as when considering which type of sports drink best suits a given need, as discussed above. You also need to consider the following factors:

• Caloric ContentThe higher the energy content, the slower the rate of gastric emptying will be.

• Exercise Intensity Exceeding 75% MHR:

• Hydration Level

The greater the level of dehydration, the slower the rate of gastric emptying will be.

• Temperature

Fluids at body temperature will empty from the stomach slower than cold fluids.

• PH Levels

Marked deviations from a PH level of 7.0 decreases gastric emptying.

References:

The Complete Guide To Sports Nutrition - Anita Bean

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