[Standardized aerobic walking on the treadmill by healthy probands and patients with mitochondrial and non-mitochondrial myopathies].

Mitochondrial myopathies are characterized by an abnormal aerobic metabolism. The present study examines the serum lactate concentration during standardized aerobic treadmill ergometry and evaluates its relevance for the diagnosis of mitochondrial myopathies. The present study includes 50 volunteers without neuromuscular disorders (control group), 13 patients with mitochondrial, and 14 patients with non-mitochondrial neuromuscular disorders. All members of the control group were able to walk 15 minutes on the treadmill at a constant velocity of at least 5 km/h without exceeding the aerobic threshold (2 mMol/l lactate, venous blood). Ten patients with mitochondrial myopathies and 4 patients with non-mitochondrial myopathies already exceeded the aerobic threshold at walking velocities of 4 or 5 km/h. Though indicating a reduced aerobic endurance, a pathological test result does not prove the diagnosis of a mitochondrial myopathy. Sensitivity and specificity of treadmill ergometry did not differ significantly from those reported for bicycle ergometry. Thus, using the most common aerobic activity in daily life, treadmill ergometry can be considered as an alternative to bicycle exercise tests in the assessment of mitochondrial abnormalities.