Muscle Quality, Architecture, and Activation in Cachectic Patients with Rheumatoid Arthritis

Objective. To explore muscle-specific force (force per physiological cross-sectional area, or PCSA) and muscle activation in cachectic patients with rheumatoid arthritis (RA). Methods. In 14 muscle-wasted patients with RA and age and sex matched healthy controls, vastus lateralis (VL) force and voluntary activation capacity were assessed during maximal isometric contractions with electromyography and superimposed electrical stimulations. VL PCSA was determined from ultrasound measures of fiber fascicle length (Lf), pennation angle, and volume, together with assessments of body composition by dual energy x-ray absorptiometry and objective physical function. Results. Although patients with RA had reduced physical function, lower muscle mass, and VL volume relative to controls, there were no differences in muscle-specific force and activation. PCSA, force, and pennation angle tended to be lower in RA, with no differences in Lf. Conclusion. Muscle-specific force and activation are not compromised and thus are unlikely to contribute to reduced function in cachectic patients with RA.