A forearm exercise screening test for mitochondrial myopathy.

Background: The authors hypothesized that impaired oxygen extraction in mitochondrial myopathy (MM) results in a high oxygen saturation in venous effluent blood from working muscle and that this phenomenon can be used as a diagnostic tool for MM.

Methods: Twelve patients with MM, 10 patients with muscular dystrophy, and 12 healthy subjects were studied. All subjects performed intermittent static handgrip exercise (1/2 Hz) at 40% of maximal voluntary contraction (MVC) for 3 minutes.