Background: The primary disease mechanism underlying mitochondrial myopathies (MM) is impaired energy generation to support muscle endurance. Little is known about muscle contractility before energy becomes deficient during muscle contractions. We investigated muscle contractility in MM to uncover potentially fixed weakness aspects of the disorders. Methods: Contractility of calf and thigh muscles was investigated by comparing strength with contractile cross-sectional area (CCSA) of the used muscles, as measured by stationary dynamometry and MRI, respectively. Results and discussion: Our findings suggest reduced contractile properties in thigh and calf muscles of patients with MM.