Fueling For Endurance Ten Mistakes Endurance Athletes Make and How You Can Avoid Them

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by Steve Born

Steve Born is a technical advisor for E-CAPS with over a decade of involvement in the health food industry. He is a three-time RAAM finisher, the 1994 Furnace Creek 508 Champion and 1999 runner-up, and is the holder of two UMCA records.

Over Hydrating.
Too many times endurance athletes fall for the "if a little is good, a lot is better" myth. Nowhere is this truer than when it comes to hydration. All it takes is one race where you've had to DNF due to cramping and you start thinking, "hmm, maybe I didn't drink enough". Next thing you know, you're drinking so much fluid that, while your thirst is quenched, your belly is full beyond the point of comfort; and you're still cramping. What's happening is that over hydrating causes what is known as "dilutional hyponatremia", or a state of over-diluted blood serum sodium. This is almost as bad as under hydrating. The results are similar: cramping with the added disadvantages of stomach discomfort, bloating, and extra urine output. It is now believed that about 24 ounces of fluids per hour is the most your body can absorb. If you feel it is necessary to consume more, remember that you will need to consume even more electrolytes to offset what is being flushed out of your system prematurely.

Consuming Too Much Simple Sugar.
For general health purposes simple, refined sugars should be avoided because of a direct link with a myriad of diseases and health ailments. Simple sugar, not immediately required for energy, is stored as glycogen in the muscles or liver. If these two storage areas are full and there is no need by the body for more energy, then excess glucose is converted by the liver into triglycerides.

Triglycerides make up most of the fat that you eat and most of the fat that circulates in your bloodstream. They're essential for good health and your tissues rely on triglycerides for energy. But as with that other essential molecule, cholesterol, high triglycerides may also be linked to heart disease. Sugar in the diet has a proportionate relationship to elevating triglyceride levels in the blood stream. Triglycerides comprise the largest proportion of fats (lipids) in the diet, in the adipose tissue, and in the blood. Eating excess sugar loads the body with excess calories that will eventually turn to fat. For more on this please check out the "Why Should I Avoid Simple Sugar" link on the Hammer Gel website.

Simple sugar absorption into the bloodstream causes an excess burst of insulin. Athletes are concerned with the quick insulin "spike". We've all experienced this quick burst of energy followed by the ensuing "crash" characterized by fatigue, lethargy, and mood swings — i.e. bonking!

Simple sugars, unlike complex carbohydrates, take longer and require more fluid to empty from the stomach and GI tract. Osmolality is the solution concentration of particles carrying an electric charge. If the osmolality of the solution you are drinking deviates from body fluid levels of 280-303 mOsm (an osmolality unit measure), it will be delayed from absorption until gastric organs can either add more fluid or the electrolytes necessary to create osmolality within body fluid or blood serum level. Because a drink mixture containing simple sugar does not match the same osmolality of regular body fluid (unless it is limited to a 3-5% concentration by weight) it will remain in the stomach until sufficiently diluted. This may cause stomach distress that is detrimental to performance.

Further, a 3-5% solution will provide no more than 100 calories per serving, far too little on an hourly basis to sustain energy levels. The solution is to use complex carbohydrates instead of simple or refined sugars in your diet and for your fuel during exercise. Energy drinks with complex carbohydrates and solid foods such as bagels, sandwiches, and pretzels are all better fuel options than candy bars and other sugar filled energy bars and sports drinks.

Eating Too Much Solid Food During Exercise.
In the 1985 Race Across America, Jonathan Boyer rode to victory using a liquid diet. Since then it has become the norm for endurance and athletes. Liquid nutrition is the easiest and most convenient way to get a calorie and nutrient dense fuel. Solid food for the most part cannot match the nutrition of the best liquid food supplements. In addition, too much solid food consumption will divert blood from working muscles for the digestive process. This and the amount of digestive enzymes and fluids required in breaking down the constituents of solid food taxes the body and can result in a feeling of bloating and/or nausea. Some solid food intake is okay during endurance exercise, particularly during ultras, but for a more rapid utilization of nutrients with less chance of stomach distress, a liquid energy source is preferred.

Training On Too Few Calories.
You may be training your muscles to do what you want them to do (riding 100 miles for example) but are you also training your stomach? If you want to be able to comfortably ingest X calories per hour during a 5-6 hour (or longer) event, you need to be practicing that in training. Exercising at a maximum intensity level and assimilating a lot of calories hour after hour are not things that the body would normally prefer to do simultaneously. Just like running or cycling far and fast, eating is a learned skill that requires the same amount of practice and attention to detail. If you plan on consuming 300 calories an hour (for example) during your race you need to practice consuming 300 calories an hour in your training. Don't skimp on calories during training!

All it takes is getting dropped by someone on a hill climb during training and it's easy to start thinking that "maybe if I just lost a couple of pounds!". The problem with trying to diet while training is that the lack of calories and the accompanying nutrients wreaks havoc on your muscles and immune system. For example, a 165-pound athlete in training requires in the neighborhood of 500 calories from protein alone. The same athlete may need 2,000-2,200 calories from carbohydrates if training an average of two hours a day. Consuming far fewer calories than what the body requires may result in the body cannibalizing it's own tissues, resulting in a a weakened muscular and immune system. Training, building muscle and following a sound diet are the best way to lose weight because it comes off slowly. The endurance athlete's diet should contain 12-20% of total calories from protein, 50-60% from carbohydrates, and 20% from fat.

Not Taking In Enough Calories During Competition.
In the heat of the battle it sometimes becomes hard to maintain the discipline of calorie intake. Endurance athletes can get so wound up with trying to keep up the pace that they sometimes forget to "fuel the engine" or don't give it enough fuel. Consistent intake of calories, allowing for adaptations due to weather conditions, provide consistent fueling of the body, prolonging endurance, and protecting the muscle tissue from being cannibalized. If you want to be strong in the latter stages of a race, you must have consumed sufficient calories in the earlier stages of the race. Calorie intake in the range of 200-350 an hour, (perhaps up to 400 on occasion), is necessary to prevent energy levels from dropping. Again, as mentioned earlier, you will be able to determine what your calorie needs are only by practicing fuel consumption during training.

Conversely, taking in too many calories during competition can present a real problem. The belief that "if a little is good, a lot must be better", creates this problem. The body can only process a given amount of calories an hour and to force additional food down, in the hopes of "getting ahead of" calorie needs, will usually backfire. Instead of having more calories available for fuel, they will sit in your stomach causing at least bloating and perhaps nausea and vomiting. Few things will slow you down faster or cause you to have to stop than taking in more calories than your body can handle. Listen to your body and don't get caught up in the idea that mega-calorie intake is ideal. Going slower as a result of lower calorie intake is far better than getting sick and having to stop.

Not Taking Supplemental Electrolytes.
An athlete who's suffered from painful and debilitating cramping usually need only cross that bridge once. While consuming enough calories during workouts is vital, it is equally important to provide the minerals necessary for proper cellular metabolism, cardiac function, and muscle contractions. All too often the endurance athlete finds out too late that these electrolytes have been depleted through bodily fluids and perspiration, the signs of which are muscle weakness, nausea, and cramping.

In addition, too many athletes rely on salt tablets, believing them to be the cure for the prevention of cramping and other heat related problems. A balanced blend of calcium, magnesium, potassium, sodium (in the form of sodium chloride), and manganese provides protection for the athlete training and competing in hot weather. Remember though, that even when it's not 100 degrees outside, electrolyte replacement is still vital (any cross-country skier will tell you that). You may not need as much as you would in hotter weather, but your body still requires them during workouts, especially ones over two hours in length.

Even if you've never cramped or don't see this as a real issue, there are other problems that arise from electrolyte depletion, problems that will negatively affect your performance. A deficiency in calcium, for example, can lead to achy joints, heart palpitations, nervousness, and hypertension. A deficiency in potassium will manifest itself in muscular fatigue, diminished reflex function, fluctuations in heartbeat, headaches, and edema. The signs of magnesium deficiency include insomnia, chronic fatigue, poor digestion (to the point where the stomach will shut down), and irritability. A lack of manganese can result in excess perspiration, rapid pulse, and hypertension. During an endurance event and in particular an ultra marathon type of event, these problems become more realistic. Making sure your electrolyte needs are met will help you avoid not only cramping, but a host of other potential disasters.

There is no sports drink in existence that provides electrolytes in substantial amounts. Electrolyte needs can vary several hundred percent, depending on heat levels, while caloric intake may only fluctuate by 25-50% and fluid intake may only vary 20-30%. This makes sports drinks, with their set amount of electrolytes and calories per serving, incompatible for meeting the unique and individualistic needs of athletes. Effective electrolyte replacement can and should come from a source not tied in with calories.

Consuming Too Much Protein During Exercise.
During endurance exercise, approximately 8-15% of the calories required should come from protein, with the remaining 85% from complex carbohydrates. Many Meal Replacement Drinks (MRPs) that are used as endurance fuels during exercise contain too much protein with very little carbohydrates. The human body, while able to handle 20-30 grams of protein in one intake, cannot tolerate that on an hourly basis. Too much protein fills the blood with too many amino acids. These excess amino acids are converted into carbon dioxide, water, and ammonia. This ammonia is toxic to the body and is a primary cause of premature fatigue. While the body is equipped to handle excess ammonia by converting it to urea then filtering it through the kidneys, too much puts a burden on the kidneys.

Not Consuming Any Protein During Exercise.
The primary source of muscle energy production is adenosine triphosphate (ATP). Each muscle stores its own supply of glycogen, which is a long-chain carbohydrate having a chemical structure similar to the carbohydrates found in a common potato. When we exercise the body can more easily break down muscle glycogen into ATP than convert either fat or the limited amounts of protein donated from lean muscle mass.

However, after 90 minutes, and becoming more important the longer a workout or race is, the body will begin to utilize protein for fuel as glycogen reserves are reduced. This metabolic process, called gluconeogenesis, allows for the synthesis of glucose from protein (along with the glycerol part of the fat molecule). The body will cannibalize protein from muscle tissue if adequate amounts of protein are not ingested. This process not only deteriorates lean muscle tissue but hampers fat burning capabilities and speeds up the production of ammonia.

To prevent this from happening the endurance athlete should make sure carbohydrate intake is consistent and that some protein is consumed during endurance exercise. In addition, it is believed that soy protein is the preferred choice during exercise as it has less chance of producing ammonia than whey protein.

Staying With Your Game Plan When It's Clearly Not Working.
Endurance athletes tend to be strong willed and uncompromising. Most have a game plan in place for training and racing. This is a good idea and something we strongly recommend. Problems arise when the athlete's game plan is no longer working, due to any number of unforeseen circumstances, but he or she makes the mistake of thinking that deviating from the game plan will be worse than making a change on the fly.

One of the more common times this happens is after a poor race. Many athletes think the cure for a poor race is to train harder and harder. Instead of recuperating and focusing on optimizing their training, many athletes will train themselves into the ground. The vicious cycle continues as the "cure" for fatigue and lethargy is all too often more training. This only digs a deeper hole for the athlete who needs to recognize the symptoms of over training and spend enough time recovering completely.


The most common symptoms of overtraining are irritability, restless sleep, elevated resting heart rate and inability to reach peak heart rates during training. As an endurance athlete, make sure that time spent recovering is taken as seriously as the time spend training.

Another time it's not a wise idea to stick to a game plan that isn't working is during an event. While it is important to maintain a fairly consistent supply of calories to the body, when it's hot outside the body's ability to process fuel becomes compromised. It's important to recognize this and to listen to your body. Continuing to force down X amount of calories an hour (the original game plan) even when your body cannot properly assimilate them puts a burden on your stomach and can cause feelings of bloating and nausea or worse, hindering performance. During the heat it becomes more important to stay hydrated and maintain electrolyte levels. Be willing to cut back on calorie consumption when your body tells you to and focus on maintaining hydration and proper electrolyte levels. It is okay to do this and resume regular caloric intake when you start feeling better and your stomach has had some time to assimilate the calories it already has.

Not Consuming Enough Calories and Nutrients After Workouts.
After a hard workout or race, it's easy to neglect the proper replenishment of your body. Sometimes all that sounds good is lying down and not moving for several hours. This is a mistake as this is the best time for the athlete to provide the body with the carbohydrates, protein, vitamins, and minerals necessary for proper recovery. This is when your body is most receptive to replenishing nutrients because it is going into high hear to recover from and adapt to the stress it has just experienced. Habitually consuming 50-75 grams of carbohydrates and 15-20 grams of protein within 30-60 minutes.
 
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