Originally Posted by Colker, Carlon M.

The premier consideration for a sport-drink formulation is something called “tonicity.” The tonicity of a solution is also referred to as the “osmolality” of a solution. These terms refer to the concentration in liquid of sodium, sugar, and to a lesser extent, other electrolytes. Your body has a normal concentration of these substances that can be calculated by and given a numeric value (equal to about 280).

A fluid that contains a higher concentration of sugar and electrolytes relative to this number is said to be hypertonic. A fluid that contains a lower concentration of these substances relative to the human is hypertonic.

Fluid flows through tissues in the direction of the highest concentration. So a hypertonic solution (like so many of the more popular retail sports drinks on the market) will actually draw fluid out of the body and actually temporarily worsen dehydration. Through the body eventually secretes enough water into the intestines to dilute the hypertonic solutions, the temporary water shit into the gut can expose the bodybuilder to sluggishness, and even cramping. Many bodybuilders note excess mucus formation and an ironic persistent need to drink plain water after drinking these types of sports drinks. As a result, you’ll never see a professional bodybuilder quench their thirst with these popular mainstream beverages.

As far as an isotonic solution once in the stomach it won’t go anywhere fast because it has the same osmolality as the body. It’ll just sit in your gut until you system can remove it. As a result, you’re left bloated with abnormal distention.

Finally, a hypotonic solution is rapidly absorbed. Because of its lower osmolality compared to the boy, it empties quickly from the gut for absorption into tissues, nourishing working cells.

Pure water is a most extreme hypotonic solution, with an osmolality of less than 20. Yet while water is well absorbed, it can’t replenish electrolytes and critical micronutrients, because it doesn’t contain an appreciable amount of these electrolytes needed to assist in the cultivation and maintenance of a good pump. Even traditional electrolyte formulas that contain sodium and potassium may not be enough for intense training, because they lack magnesium and phosphorus, which are critical to cell fluid resuscitation and functional recovery after intense exertion.

The rehydration formula you choose should have these electrolytes and the osmolality should be significantly lower than 280 (otherwise it won’t get absorbed quickly enough), and preferably more than 200 (otherwise it’s probably too low in electrolytes). In other words, you wan to be reasonably sure that absorption happens quickly due to the hypotonic aspect while being certain that you are getting an appropriate concentration of electrolytes. By the way, if a company doesn’t publish their osmolality, don’t buy their hydration formula.

Perhaps the most annoying thing about many popular sports rinks is that they’re loaded with sugar. After all I’ve said about focusing on healthy fiber-based carbohydrates in the form of fresh vegetables, the last thing you need to do is blow it by drinking high amounts of sugar during your workout. Also, if the total carbohydrate content of a sports drink exceeds 10 or more grams per eight fluid ounces it’s too much. If that’s the case, you can reasonably be conclude that the solution is either hypertonic and won’t be quickly absorbed, and/or contains too much sugar and not enough electrolytes.