Background/Purpose: Sporadic inclusion body myositis (sIBM) represents a progressive inflammatory muscle disease, which causes severe loss in skeletal muscle mass and strength, especially in the quadriceps muscles. Loss in muscle strength has been reported as high as 15% per year in sIBM patients¹. The impairment in muscle performance causes reductions in physical function and quality of life, eventually leading to loss of independency. Only few studies have investigated the effects of exercise training in sIBM patients and none have employed a non-exercising control group for reference. Therefore the objective of the present study was to investigate the effect of 12 wks low-intensity blood-flow restricted (BFR) training vs. the natural time course of disease progression on maximal knee extensor muscle strength in sIBM patients.

Methods:  The present data are part of a larger randomized controlled trial reported in clinicaltrials.gov database (NCT02317094). Twenty-two patients diagnosed with sIBM (4 females, 18 males, 69.0±5.6 years) were tested for maximal unilateral isometric knee extensor muscle strength in both legs (mean of right and left leg is presented), using an isokinetic dynamometer (KinCom; Chattecx Corp., Chattanooga, TN, USA). Following baseline testing participants were randomized to a BFR-training group (BFR, n=11) or to a non-exercising control group (CON, n=11). The BFR group performed unilateral BFR-training for both legs (leg press, knee extension, knee flexion, dorsal flexion & plantar flexion, 3-4 sets per exercise) two times per week for 12 wks. Exercise intensity (training loads) was ~25RM and blood-flow restriction was achieved using an inflatable pneumatic cuff applied at the proximal part of the shank/thigh. Cuff pressure (110 mmHg) was maintained throughout all sets and pauses while released by the cessation of the final set of each exercise, before continuing with the next exercise.

Results:  At 12 wks follow-up CON showed a significant reduction in isometric knee extensor strength compared to baseline (-9.1%, p=0.051). In comparison, analyzing patients with satisfactory training compliance (>60%, n=8) BFR showed no change in knee extensor strength (+5.7%, N.S.). Further, a group x time interaction in maximal knee extensor strength was observed from baseline to 12 wks follow-up (p=0.021).

Conclusion:  By extrapolating the present data the disease-related rate of loss in knee extensor muscle function in the present sIBM patients (~30% per year) appeared to be much greater than previously reported in old healthy adults (2-4% per year). Notably, maximal knee extensor muscle strength was preserved in response to 12 wks of BFR training, although on the other hand no specific improvements were observed. These findings indicate that BFR-training may have a protective effect on skeletal muscle function in sIBM patients, preventing or delaying the loss in contractile capacity seen with progression of the disease in the present non-exercising control group.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/effects-of-12-weeks-low-intensity-blood-flow-restricted-resistance-training-on-knee-extensor-strength-in-patients-with-sporadic-inclusion-body-myositis/