Physical function and muscle strength in sporadic inclusion body myositis

Introduction: In this study, self‐reported physical function, functional capacity, and isolated muscle function were investigated in sporadic inclusion body myositis (sIBM) patients. Methods: The 36‐item Short Form (SF‐36) Health Survey and 2‐min walk test (2MWT), timed up & go test (TUG), and 30‐s chair stand performance were evaluated. In addition, patients were tested for knee extensor muscle strength (isokinetic dynamometer) and leg extension power (Nottingham power rig). Results: TUG performance was the strongest predictor of self‐reported physical function ( r 2 = 0.56, P < 0.05). Knee extension strength and between‐limb strength asymmetry were the strongest multi‐regression indicators of TUG performance ( r 2 = 0.51, P < 0.05). Strength asymmetry showed the strongest single‐factor (negative) association with 2MWT performance ( r 2 = 0.49, P < 0.05). Discussion: TUG assessment appears to sensitively predict self‐perceived physical function in sIBM patients. Notably, between‐limb asymmetry in lower limb muscle strength had a substantial negative impact on motor tasks involving gait function.