This study will be a small randomized clinical trial to test the effectiveness of neuromuscular electrical stimulation (NMES) to improve physical function and reverse muscle atrophy in patients with rheumatoid arthritis (RA). The investigators will also determine the mechanism by which NMES affects muscle hypertrophy and physical function. The proposed study will be the first step in demonstrating that NMES training is an effective alternative to highly intense volitional exercises (VE) in individuals with RA. After baseline testing, 60 individuals with RA will be randomly assigned to a 16-week NMES program or highly intense VE program. Both programs will be applied based on the best current clinical evidence. Subjects will be re-assessed after intervention. Groups will be compared for differences in performance-based and self-reported lower extremity function, muscle volume, muscle strength, proportion and area of type I and II muscle fibers, fat content, and muscle oxidative capacity from pre- to post-intervention. Changes in physical function, muscle volume, and muscle strength will be correlated with proportion and area of type I and II muscle fibers, fat content, and markers of muscle oxidative capacity.

Inclusion Criteria:

• English-speaking
• Age 21 or older
• Diagnosed with RA for at least 5 years according to the criteria of the American College of Rheumatology
• Independent ambulator

Exclusion Criteria:

• History of cardiovascular disease or uncontrolled hypertension (above 140/90 mmHg);
• History of a quadriceps tendon or patellar tendon rupture;
• History of previous adverse reaction associated with electrical stimulation treatment;
• Surgery to the dominant lower extremities within the past 6 months.
• History of a neurological disorder that may affect lower extremity function, such as cerebrovascular accident or neuropathy, parkinson's disease, multiple sclerosis, etc.;
• History of muscle disease such as muscular dystrophy;
• Change in medication regimen (excluding NSAID change) during the month prior to treatment;
• Current use of cholesterol-lowering medication;
• History of malignancy during the last 5 years, excluding skin cancers other than melanoma;
• Current or anticipated pregnancy;
• Less than 70º of passive knee flexion;
• Are not willing to undergo needle biopsy.
• Participated in progressive resistance training or NMES training in the prior year;
• Prior adverse effects with local anesthesia.