Carbohydrates along with fat are the two main fuel sources for your muscles. Your body can store about 2000 calories in the form of glycogen which will last about 2hrs for the average runner. So, during a long run of 2+ hours, these carb stores will be depleted. If they're not replaced during the run, then the runner will more than likely "bonk" or "hit the wall." Sports drinks and/or sports gels are a great way to restock the glycogen (energy) stores while on the run. But don't wait until you feel fatigued to begin resupplying or it will be too late.
Sodium is needed to help the body properly absorb the fluids you're taking in. Ever have that sloshing-in-your-stomach feeling during a race? The sloshing is probably not due to drinking too much too fast. More than likely the water is remaining in your belly because you've decreased your sodium levels so much that your body can no longer absorb the fluids, so they're just "stuck" with nowhere to go. Ever have calf or quad cramps? This too is often a sign of dehydration and depleted potassium levels.
There are so many different brands of sports drinks on the market all claiming they're the best for you. So what exactly should be in a sports drink? There are some basics you should look for. As for the "extras" in many sports drinks? For the most part, that's exactly what they are—extra. You'll have to decide whether you need the extras or not.
Staples Of A Sports Drink:
Most experts agree that the sodium levels of sports drinks should be in the range of 110 - 220 mg per 8 fl. oz. A newer brand, just recently available—The Right Stuff— contains no carbs, but it contains much higher levels of sodium and other electrolytes. To read a review of The Right Stuff [click here].
The carbohydrate concentration in a sports drink should be 6-8% or
6 - 8 grams per 100 ml
14.2 - 18.9 grams per 8 oz.
21.3 - 28.4 grams per 12 oz.
Sports drinks containing more than these quantities of carbs should be used for refueling after a workout, but not during.
Sports Drink Extras:
Energy drinks and sports drinks are often confused. In general, sports drinks don't contain caffeine. The smaller canned (and some bottled) energy drinks (i.e., Red Bull) often contain very large amounts of caffeine as well as sugar or other sweeteners. Research has shown that some caffeine ingested before a race can boost performance (click here for more info), but drinking large amounts of caffiene throughout a race can have adverse effects and cause stomach issues for many runners.
Some brands of sports drinks have added protein to their formula. Some claim the protein/carb mixture enhances performance. There is mixed results/opinions on whether performance is actually enhanced. The added protein, however, has been shown to speed muscle recovery. Accelerade, Amino Vital, Endurox R-4, and PowerBar Recovery Performance all contain added protein.
Some brands contain a wide array of added vitamins. While this may be good for your general health, there's no research to show that they will help with your performance or benefit rehydration.
There are actually three different types of sports drinks available—Isotonic, Hypotonic, and Hypertonic. Some are designed for use during a run, while others are designed for after activity hydration. Listed below is more info about each type of sports drinks.
Isotonic Sports Drinks—Contain electrolytes and 6-8% carbs. Isotonic sports drinks usually contain about 120-170 calories per 500 ml of fluid. Probably the most common type of sports drink, isotonic sports drinks are good for normal replacement of fluids lost through normal sweating incurred during middle and long distance runs. (Examples: Accelerade, Gatorade [original], Gatorade Endurance Formula, Powerade [original], PowerBar Endurance Sport [powder])
Hypertonic Sports Drinks—Contain about 10-15% carbs and usually about 240-320 calories per 500 ml of fluid. These drinks are designed to replenish carb levels after exercise or to top off the glycogen stores before an endurance run. Hypertonic drinks are good for marathons or ultraruns. Due to the high levels of carbs, if hypertonic drinks are used during exercise, it's very important that a runner also take in some isotonic or hypotonic drinks too to help replace fluids. (Examples: Endurox R-4, Gatorade Performance Series, PowerBar Performance Recovery, Isopure Endurance)