Exercise intolerance in patients with mitochondrial myopathies: perfusive and diffusive limitations in the O2 pathway

Mitochondrial myopathies are a heterogeneous group of disorders characterized by genetically determined defects that impair oxidative phosphorylation at the mitochondrial level. Exercise intolerance is a clinical hallmark in most of these patients, who present fatigue and dyspnoea during low levels of exertion, including moderate activities of daily living. This review aims to discuss the principal limiting factors of muscle oxidative metabolism during exercise in patients with mitochondrial myopathies, investigating the effects of perfusive and diffusive impairments along the O transport pathway from ambient air to muscle mitochondria. Possible therapeutic effects of exercise training will be also highlighted.