The Pathophysiology of Exercise and Effect of Training in Mitochondrial Myopathies

Abstract

Patients with mitochondrial myopathy often have multiorgan affection, but exercise intolerance is the most common symptom. This is so, since mtDNA mutation load is often high in skeletal muscle and oxidative demand of skeletal muscle can increase up to 100-fold from rest to maximal exercise. In a clinical setting, the degree of exercise intolerance is difficult to grade and distinguish from limited physical fitness due to sedentary lifestyle or cardiopulmonary diseases. Exercise limitations in patients with mitochondrial myopathy can be assessed with provocative exercise tests. In the following chapter, we describe the pathophysiological result of mitochondrial defects in skeletal muscle during exercise and how exercise tests can be used to reveal differences between intact and dysfunctional mitochondrial function in skeletal muscle.