Twelve weeks of BFR training did not improve self-reported or objective physical function in these sIBM patients. However, the training protocol had a preventive (retaining) effect on the disease-related decline in leg muscle strength, which may aid the long-term preservation of physical function and postpone the need for healthcare assistance.

Sporadic inclusion body myositis (sIBM) is a systemic disease that is characterized by substantial skeletal muscle weakness and muscle inflammation, leading to impaired physical function. The objective was to investigate the effect of low-load resistance exercise with concurrent partial blood flow restriction to the working muscles (blood-flow-restricted (BFR) training) in a patient with sIBM. The training consisted of 12 weeks of lower extremity BFR training with low training loads (~25-RM). The patient was tested for mechanical muscle function and functional capacity before and after 6 and 12 weeks of training. Maximal horizontal gait speed increased by 19%, which was accompanied by 38-92% improvements in mechanical muscle function (maximal isometric strength, rate of force development and muscle power). In conclusion, BFR training was well tolerated by the patient with sIBM and led to substantial improvements in mechanical muscle function and gait speed.

Sporadic inclusion body myositis (sIBM) is an idiopathic inflammatory muscle disease associated with skeletal muscle inflammation and a parallel progressive decline in muscle strength and physical function. Eventually, most sIBM patients require use of wheelchair after about 10 years of diagnosis and assistance to perform activities of daily living. This study presents data from a randomized controlled intervention trial (NCT02317094) that examined the effect of 12 weeks low‐load blood‐flow restricted (BFR) resistance training on maximal muscle strength, power, rate of force development (RFD), thigh lean mass (TLM), and voluntary muscle activation (VA) in sIBM patients. A time‐by‐group interaction in knee extensor strength was observed in the stronger leg (p ≤ 0.033) but not the weaker leg. Within‐group changes were observed with BFR training (BFR) manifested by increased knee extensor strength in the strongest leg (+13.7%, p = 0.049), whereas non‐exercising patients (CON) showed reduced knee extensor strength (−7.7%, p = 0.018). Maximal leg extensor power obtained for the stronger leg remained unchanged following BFR training (+9.5%, p = 0.37) while decreasing in CON (−11.1%, p = 0.05). No changes in TLM were observed. VA declined post‐training (p = 0.037) in both BFR (−6.3% points) and CON (−7.5% points). The present data indicate that BFR resistance training can attenuate the rate of decline in mechanical muscle function typically experienced by sIBM patients. The preservation of muscle mass and mechanical muscle function with BFR resistance training may be considered of high clinical importance in sIBM patients to countermeasure the disease‐related decline in physical function.

BackgroundSporadic inclusion body myositis (sIBM) is clinically characterised by progressive proximal and distal muscle weakness and impaired physical function while skeletal muscle tissue displays abnormal cellular infiltration of T cells, macrophages, and dendritic cells. Only limited knowledge exists about the effects of low-load blood flow restriction exercise in sIBM patients, and its effect on the immunological responses at the myocellular level remains unknown. The present study is the first to investigate the longitudinal effects of low-load blood flow restriction exercise on innate and adaptive immune markers in skeletal muscle from sIBM patients.MethodsTwenty-two biopsy-validated sIBM patients were randomised into either 12 weeks of low-load blood flow restriction exercise (BFRE) or no exercise (CON). Five patients from the control group completed 12 weeks of BFRE immediately following participation in the 12-week control period leading to an intervention group of 16 patients. Muscle biopsies were obtained from either the m. tibialis anterior or the m. vastus lateralis for evaluation of CD3-, CD8-, CD68-, CD206-, CD244- and FOXP3-positive cells by three-colour immunofluorescence microscopy and Visiopharm-based image analysis quantification. A linear mixed model was used for the statistical analysis.ResultsMyocellular infiltration of CD3−/CD8+ expressing natural killer cells increased following BFRE (P < 0.05) with no changes in CON. No changes were observed for CD3+/CD8− or CD3+/CD8+ T cells in BFRE or CON. CD3+/CD244+ T cells decreased in CON, while no changes were observed in BFRE. Pronounced infiltration of M1 pro-inflammatory (CD68+/CD206−) and M2 anti-inflammatory (CD68+/CD206+) macrophages were observed at baseline; however, no longitudinal changes in macrophage content were observed for both groups.ConclusionsLow-load blood flow restriction exercise elicited an upregulation in CD3−/CD8+ expressing natural killer cell content, which suggests that 12 weeks of BFRE training evokes an amplified immune response in sIBM muscle. However, the observation of no changes in macrophage or T cell infiltration in the BFRE-trained patients indicates that patients with sIBM may engage in this type of exercise with no risk of intensified inflammatory activity.

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 selfreported physical function (r 2 5 0.56, P < 0.05). Knee extension strength and between-limb strength asymmetry were the strongest multi-regression indicators of TUG performance (r 2 5 0.51, P < 0.05). Strength asymmetry showed the strongest single-factor (negative) association with 2MWT performance (r 2 5 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.