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Glycogen storage disease type V

Glycogen storage disease type V is a metabolic disorder, more specifically a glycogen storage disease, caused by a deficiency of myophosphorylase, the muscle isoform of the enzyme glycogen phosphorylase. This enzyme helps break down glycogen (a form of stored carbohydrate) into glucose so that it can be utilized within the muscle cell. more...

Gardner's syndrome
Gastric Dumping Syndrome
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Gaucher Disease
Gaucher's disease
Gelineau disease
Genu varum
Geographic tongue
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Glycogen storage disease
Glycogen storage disease...
Glycogen storage disease...
Glycogenosis type IV
Goldenhar syndrome
Goodpasture's syndrome
Graft versus host disease
Graves' disease
Great vessels transposition
Growth hormone deficiency
Guillain-Barré syndrome

GSD type V is also known as McArdle's disease or muscle phosphorylase deficiency. The disease was first diagnosed in 1951 by Dr. Brian McArdle of Guy's Hospital, London.

People with this disease experience difficulty when their muscles are called upon to perform relatively brief yet intense activity. The inability to break down glycogen into glucose results in an energy shortage within the muscle, resulting in muscle pain and cramping, and sometimes causing serious injury to the muscles. In addition, rhabdomyolysis—the breakdown of muscle tissue—can cause myoglobinuria, a red-to-brown-colored urine. The myoglobinuria can cause kidney damage. The disease is hereditary and is inherited as an autosomal recessive trait. Anaerobic exercise must be avoided but regular gentle aerobic exercise is beneficial.


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Competition nutrition: finding the winning combination to boost energy, performance and well-being
From American Fitness, 3/1/96 by V. Wade Contreras

You're going for that last intense burn set of leg presses in your quest to add bulk and cut fat--and find you're suddenly out of gas. You just can't go on. Perhaps you're a marathon runner and feel like you've hit a plateau and you'll never get your time down. Or maybe you just exercise for fun and health and want to maximize your energy. Whatever your situation, diet is a crucial factor in providing your body with the energy to be its best.

For men of the '90s, the exercise watchword seems to be "performance." If you're training hard and not seeing the results you want, maybe the place to look is your training diet. If your training table often ends up being the nearest taco or burger joint, it's time to get on a more performance-oriented diet. Strength trainers will insist they need extra calories, no matter what the source, to add extra muscle. But poor foods won't add the muscle. You need a healthy eating plan to give your body a winning edge.

Carbohydrates are an athlete's best friend, according to Susan M. Kleiner, Ph.d., R.D., and Maggie Greenwood-Robinson, authors of High Performance Nutrition: The Total Eating Plan to Maximize Your Workout (Wiley, $16.95) slated for a May release. Their major role is to provide energy, especially during exercise. The body utilizes ca-rbohydrates by breaking them down into blood glucose which is ushered into cells. Glucose can be converted to either liver or muscle glycogen (the storage form of carbohydrates). When you exercise, the body uses muscle glycogen for energy. But be careful, blood glucose can also turn into body fat if you eat more carbohydrates than you need.

There are two type of carbohydrates--complex and simple. Complex carbohydrates are in most plant foods, like cereal, pasta, fruits and vegetables. They contain essential nutrients, including fiber. Some simple carbohydrates, known as sugars, are in fruits and vegetables. Refined sugars, in candies and sweets, are considered "empty calories," which means they supply no nutrients other than calories. Limit these in your diet.

Kleiner, who's been a nutritional counselor for professional football teams, says 60-65% of our calories should come from carbohydrates. Strength trainers need even more. "To develop muscle, you must increase your calories, and the healthiest way to do that is to up your carbohydrate intake, not your protein or fat," she explains. The best way to increase complex carbohydrate intake is to eat more whole grain cereals and breads, pasta, rice, potatoes, yams and legumes. Kleiner also stresses the importance of loading up on carbohydrates during workouts by keeping a sports drink handy.

In strength training, short bursts of effort are needed, and carbohydrates supply about 95% of the fuel for this kind of exercise. However, in mild to moderate intensity aerobics, the fuel mix is about half carbohydrate, half fat. If you keep going for a long workout, your body can deplete stored carbohydrates for energy. So for long workouts, the performance edge goes to people who have the most glycogen stored, and therefore the people who eat the most carbohydrates.

One last note on carbohydrates. After exercise, your muscles are carbohydrate-hungry. You should eat in the first two hours following a workout to maximize recovery. Kleiner suggests fruited yogurt as a good snack because it's high in carbohydrates and contains enough protein for an even release of energy and optimal storage of glycogen.

Beyond carbohydrates, male athletes should know about fat and what it does to their bodies. Before you run cowering from the word that has been touted as the scourge of the nutritional universe, remember that fat is an essential nutrient. It helps form structures of cell membranes, regulate metabolism, and provides a source of energy for exercise. However, you should know which fats are better for you and how to watch your cholesterol.

There are several types of fat. You should limit saturated fat because it can raise cholesterol levels, which everyone knows leads to narrowing of the arteries and other bad consequences. We've all heard about the saturated fat offenders--beef, dairy products, and tropical oils like coconut, palm and palm kernel oils. Keep these to a minimum.

But enough of the nutritional hand slapping. More important is knowing what kinds of fat you can eat with a clean conscience (and clean arteries), because this seems to be where confusion arises. Unsaturated fats are better for you, and there are two kinds--polyunsaturated and monounsaturated. Polyunsaturated fats are vegetable oils such as safflower, sunflower, corn, soybean and cottonseed oil. They actually cut cholesterol, but they cut the "good" cholesterol you want in your body, too. Also, Kleiner says researchers have discovered a correlation between diets high in polyunsaturated fat and a greater risk of cancer.

So we're left with monounsaturated fats. The majority of researchers a-re claiming this is the healthiest fat. As proof of this, Kleiner points to the Eskimos and Greeks. "Even though their diets are high in total fat, their incidence of heart disease is low compared to Americans," says Kleiner. "Scientists have ascertained why. The predominant fat in both cultures is monounsaturated--one from fish, the other from' olives." Monounsaturated fats seem to lower bad cholesterol but maintain higher levels of good cholesterol. So the latest advice seems to be stick to olive, canola, peanut, and fish oils, all monounsaturated sources.

Some other fat facts. Stay away from hydrogenated fats, a commercially processed unsaturated fat that behaves more like a saturated fat. In fact, hydrogenated fats may be more harmful than the tropical oils they are meant to replace. You can learn formulas to calculate your fat intake, but simply cutting saturated fats and reading food labels is more practical. Also, eating plenty of veggies, fruits, grains and beans will help you avoid fats. Finally, a surprising new fact. Some researchers say butter may be healthier than margarine, Margarine contains substances called trans fatty acids that impair cardiovascular health. If you must use margarine, choose a brand with a liquid oil listed as the first ingredient.

Last but not least, one of the most debated topics in men's nutrition--protein. Protein is made up of smaller units called amino acids, which are used to rebuild tissue, including muscle. Some amino acids can be made by the body (nonessential), and others must be supplied by food (essential). Animal proteins are considered higher quality than plant proteins, because they contain all the essential amino acids in larger amounts and better proportions.

Not only will you find a debate raging about what is the best type of protein (egg, whey, rice, animal to name a few), conflicting reports on the necessary amount of protein are also abundant. Recommendations vary these days from mega-dose prescriptions in the muscle magazines to the minimalist approach advocated by many nutritionists. Make your own decision, keeping in mind that "moderation" seems to be a word cropping up in more and more discussions on nutrition, including protein.

According to Kleiner, if you don't work out, you need .36 gram protein per pound body weight. This is the national recommended dietary allowance (RDA). If you strength train, you need .7 gram per pound. Aerobic athletes should strive for .5 gram of protein per pound, and endurance athletes or cross-trainers may need .9 gram per pound.

Before you go out and buy some super protein powder, remember that you get a lot of protein if you eat good foods, and many researchers say getting it in food is the best way. Also, excess' protein can be harmful. "A system overloaded in this manner can endanger the kidneys in people susceptible to kidney problems," says Kleiner. "Also, a diet too high in protein may cause kidney cancer, according to new research from the National Cancer Institute."

Whether you're shooting for muscles of steel or just want to increase your energy and longevity, watch the foods you put into your body. The time you invest in eating healthy will pay off in the long run and give you a competitive edge to push your workout results to a new high.

RELATED ARTICLE: Carbohydrate Loading for Endurance Athletes

One of the few dietary methods that can immediately improve your physical endurance is carbohydrate loading. It is a technique of pushing extra glycogen into muscle storage. Carbohydrate loading should be done the week prior to competition. It works best for endurance events lasting 60 to 90 minutes or more.

There are two components to carbohydrate loading. They are resting prior to the race or event, and eating as many carbohydrates as possible. It works best for athletes already in top shape because the better your condition, the greater your glycogen capacity. Here's the program included in Kleiner's book:

The Go Strong Carbohydrate-Loading Plan


Note: Although you should increase your carbohydrates to 70% two days prior to competition, make sure you're not loading up on snack foods like ice cream and cookies. They're sometimes high in fat, and will fill your stomach but leave muscles unfueled.

Before, During and After

About two to three hours before the event, have a light meal packed with carbohydrates. Ideally, eat about 100 grams of carbohydrates. A combination of fruit, bread, rice, or pasta with skim milk or yogurt is excellent--or have a good sports drink. Twenty to 30 minutes prior to the race get some additional carbohydrates. Another sports drink is probably better than more solid food.

If you're competing in an extended endurance event, have a sports drink during the race. This stabilizes blood sugar levels, maintains fluid levels and delays fatigue. Drink one-half cup of liquid every 15 to 20 minutes to extend your endurance. For 24 hours after the event, eat and drink high carbohydrate foods to replenish your glycogen stores. For the first five hours afterward, eat foods containing 40 to 60 grams of carbohydrate.

So next time you're at the starting line and your opponent is glaring at you, turn to him and politely ask how his glycogen stores are doing. He'll probably be left confused--and definitely be left in the dust.

COPYRIGHT 1996 Aerobics and Fitness Association of America
COPYRIGHT 2004 Gale Group

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