McArdle 's Syndrome is a muscle metabolism disorder that is caused by a deficiency of the glycogen enzyme muscle phosphorylase (Quinlivan). Muscle phosphorylase is the enzyme that breaks down glycogen during glycolysis. Without this enzyme, the body has a difficult time going through anaerobic glycolysis and can cause an individual to experience intense muscle pains. It is estimated that 1 in every 100,000 people will get McArdle 's Syndrome (Haller). McArdle 's Syndrome is a genetic disorder, so there is no preventing it. Even the unaffected child of an affected person will have a 50% chance of being a carrier, which means they could pass it on to their own children (Martín). Other common names for McArdle 's Syndrome are Glycogen Storage disease type V (GSDV) and McArdle disease (Martín, Quinlivan).
The symptoms of McArdle 's Syndrome were recognized about 65 years ago by Brian McArdle. In 1959, it was found that all these symptoms were due to a glycogen phosphorylase deficiency in the muscles (Haller). Some of these symptoms include rapid fatigue, myalgia, and muscle cramps in exercising muscles. These symptoms usually occur during the first 10 minutes of exercise. Muscle cramps are one of the major signs of McArdle 's Syndrome. To prevent these muscle cramps, one should avoid high intensity and maximal aerobic exercise. Muscle weakness occurs in 25% of people diagnosed with McArdle 's Syndrome and is more likely to involve proximal muscles and people over the age of 40.