Peripheral Muscle Dysfunction in Interstitial Lung Disease: A Scoping Study

Purpose: To characterize the state of the evidence for peripheral muscle dysfunction in individuals with interstitial lung disease (ILD). Method: A scoping study was performed by searching multiple electronic databases for published papers and conference abstracts of any study design that included a measure of peripheral muscle dysfunction and/or structural and metabolic characteristics of muscle. All sub-types of ILD were eligible. Result: Forty-five studies representing 2522 individuals with 34 sub-types of ILD were included in this study. Data were charted using descriptive numerical analysis of study characteristics. Peripheral muscle dysfunction was predominantly reflected by reduced volitional isometric strength (17 studies), whereas the evaluation of muscle endurance was rare (2 studies). Volitional muscle force or torque was measured in the quadriceps (14 studies) and handgrip (8 studies), with strength preferentially reduced in the lower limbs. Eight studies measured structural or metabolic characteristics and found evidence of reduced muscle size and oxidative stress. Findings of muscle injury and muscle inflammation (e.g. serum markers, electromyography and muscle biopsies) were reported primarily in individuals with idiopathic inflammatory myopathies and connective tissue diseases. Conclusions: Reduced volitional muscle strength was the most common finding of peripheral muscle dysfunction in ILD. Further quantification of peripheral muscle dysfunction and identification of structural and metabolic characteristics are needed to target specific interventions and optimize muscle function.