Background Sporadic inclusion body myositis (sIBM) represents a progressive inflammatory muscle disorder associated with severe loss of skeletal muscle tissue and impaired muscle function, which eventually results in drastically lowered physical function, reduced quality of life, and loss of independency1–4. No previous study has investigated the potential linkage between functional capacity and health-related quality of life and the relations to mechanical muscle function in sIBM patients.
Objectives To investigate the associations between self-reported physical function, functional capacity and mechanical muscle function in patients with sIBM.
Methods Twenty-two patients with sIBM volunteered to participate in the study. All participants filled out the short form (36) health survey, and performed a 2-min walk test (2MWT), a Timed up & go test (TUG) and a 30-sec chair stand test (CS), followed by evaluations of unilateral leg extension maximal muscle power (POW; Nottingham Power Rig) and maximal isometric knee extension muscle strength (MVC; KinCom dynamometer). Multiple linear regression analyses were applied to analyze associations between the investigated variables.
Results All functional capacity tests revealed positive relationships with self-reported physical function (SF-36, physical function domain). TUG performance was the strongest predictor of self-reported physical function among the functional capacity tests (TUG: r2=0.56; CS: r2=0.43; 2MWT: r2=0.42; p<0.05). MVC and MVC asymmetry (%inter-limb deficit) combined were the strongest indicators of TUG performance (r2=0.50; p<0.05), with MVC exerting a positive effect and asymmetry a negative effect on TUG score. MVC asymmetry alone showed the strongest association (negative) with 2MWT performance (r2=0.49; p<0.05). CS performance, was not correlated to MVC, but was predicted by POW and POW asymmetry combined (r2=0.33, p<0.05) with a positive coherence for POW and a negative coherence for POW asymmetry.
Conclusions The Timed up & go test appears to be the functional capacity test that best predicts self-perceived physical function in sIBM patients. Notably, it was found that between-limb asymmetry in maximal knee extensor strength had a clear negative impact on motor tasks involving gait function. This finding underlines that increasing attention should be directed to evaluate inter-limb strength asymmetry in sIBM patients in order to prevent function loss and achieve more effective rehabilitation in this patient group.
Rose MR et al. Neurology 2001;57(3):548–50.
Benveniste O et al. Brain 2011;134(Pt 11):3176–84.
Badrising UA et al. J Neurol 2005;252(12):1448–54.
Cox FM et al. Brain 2011;134(Pt 11):3167–75.
Disclosure of Interest None declared