Association between psychosocial factors and dose of neuromuscular electrical stimulation in subjects with rheumatoid arthritis

Background: The therapeutic effect of neuromuscular electrical stimulation (NMES) on muscle strengthening and hypertrophy depends on its dose. Patients must tolerate high doses of NMES to maximize gains in muscle function. It is unknown why some patients are able to achieve high NMES dose while others are not. Disability and psychological attributes may play a role in a patient's tolerance of NMES dose. PURPOSE: To explore if disability and psychological attributes associate with the ability to achieve high doses of NMES in patients with rheumatoid arthritis (RA). Methods: Cross-sectional study. Forty subjects with RA participated in 2 sessions of NMES intervention to the quadriceps muscles. The highest NMES dose achieved by each subject was recorded. Dose was defined as the torque produced by the NMES as a percentage of the torque produced during a maximum voluntary isometric contraction. Subjects were then grouped in high or low NMES dose. Variables investigated in this study included disability, pain coping strategies, pain acceptance, sense of mastery or control, anxiety, and depression. Correlations were sought between these factors and NMES dose. MAIN Results: In unadjusted models, disability, coping self-statements, catastrophizing, and anxiety were predictors of NMES dose. In adjusted models only disability (OR = 0.17 [95% CI: 0.04, 0.77]) and catastrophizing (OR = 0.85 [95% CI: 0.72, 0.99]) predicted NMES dose. CONCLUSION: Patients with RA with lower disability and lower catastrophising achieve higher doses of NMES. Identifying factors associated with achieving high NMES dose may guide strategies to improve effectiveness of this intervention.