Investigation of Muscle Oxygenation in Patients With Rheumatoid Arthritis

This study is measuring muscle oxygen levels during exercise in people with rheumatoid arthritis and comparing the results to healthy individuals. Using a non-invasive sensor on the skin, researchers will examine whether rheumatoid arthritis affects how muscles use and receive oxygen during physical activity. **You may be eligible if...** - You have been diagnosed with rheumatoid arthritis - You are between 18 and 65 years old - You are willing to voluntarily take part - Healthy volunteers of similar age are also being recruited as a comparison group **You may NOT be eligible if...** - You have serious heart, lung, neurological, or musculoskeletal conditions that affect your physical ability - You have participated in a structured exercise program in the past 3 months - You have cognitive difficulties that prevent you from understanding exercise test instructions - You have a medical condition that makes exercise testing unsafe (per standard exercise safety guidelines) Talk to your doctor to see if this trial is right for you.