Metabolic myopathies are muscle disorders caused by abnormalities of muscle energy metabolism that result in skeletal muscle dysfunction. McArdle disease (Glycogen storage disease type V) is a disorder caused by a mutation in the PYGM - gene that is inherited in an autosomal recessive pattern. The mutation causes metabolic myopathy, where the deficiency of myophosphorylase enzyme causes a dysfunction to the glycogen metabolism of skeletal muscles. The PYGM - gene has also been detected in the central nervous system, retina of the eye, kidneys and bones.

The incidence rate of the disease has been estimated to 1/100 000, which would denote to about 50 cases in the total population of Finland. The onset of the disease symptoms occur in childhood, but the disease often remains undiagnosed until adulthood. Since the symptoms of the McArdle disease are associated with exercise intolerance and muscle tissue damage, the affected individuals have been generally advised to avoid resistance training and to participate in only light aerobic exercise. Muscle atrophy and weakness of the shoulder girdle and paraspinal muscles have also been observed with those affected by the disease. However, according to studies, resistance training has been shown to have positive impact on the symptoms deteriorating performance ability in especially adolescent McArdle patients. A well designed training regimen comprising aerobic and resistance training can have a positive effect on the physical performance ability of the person as their strength and aerobic capacity advances. According to studies, exercise can also decrease exercise intolerance and the symptoms related to it.

This thesis includes a written report and a guide for exercising, based on the results gathered for the written report on the characteristics of McArdles disease and its impact on performance ability. The target groups for the thesis are the occupational groups working in the field of health and rehabilitation, people who are affected by the McArdles disease and their family members. General exercise recommendations and exercises sustaining muscle strength have been applied and integrated according to the characteristics of McArdle disease that may affect the possible intensity of exercise.