Exercise Intensity Based on the Skeletal Muscle Quality and Physiological Cost Index of Patients with Immune-mediated Necrotizing Myopathy: A Case Report

[Purpose] To set exercise intensity for individual patients with immune-mediated necrotizing myopathy (IMNM) using limb skeletal muscle quality (LMQ) and physical cost indices (PCI). [Participant and Methods] A male patient in his 40s with IMNM performed resistance training, walking, and stair climbing exercises with exercise intensities based on weekly assessments of LMQ and PCI. The MRC muscle strength score, 6-minute walk test (6MWT), serum-CK level, and fatigue assessment scale (FAS) were evaluated before the start of physical therapy and at discharge. [Results] Exercise intensity could be increased to 60% (moderate intensity), MRC muscle strength score and 6MWT improved, and the patient was discharged to home with no worsening of the serum-CK level or FAS. [Conclusion] The results suggest that evaluation of efficiency using LMQ and PCI may be an indicator for setting appropriate exercise intensity for individuals with IMNM.