MusculRA: The Effects of Rheumatoid Arthritis on Skeletal Muscle Biomechanics

A study nurse will draw up to 150 mL of blood to measure erythrocyte sedimentation rate (ESR) and measures of immune cell function. ESR is a common hematology test that is a measure of inflammation.

Participants in the RA cohort will receive a 28-joint examination by the study physician to assess RA disease activity and report their overall health assessment.

Near-Infrared Spectroscopy (NIRS) will be used to measure oxidative capacity of forearm flexor digitorum profundus and medial gastrocnemius muscles using the PortaMon device (Artinis Medical Systems, The Netherlands). NIRS is a low-cost, non-invasive method that estimates muscle oxidative capacity by measuring oxygen consumption (mVO2) recovery kinetics via assessment of intramuscular oxy- and deoxy-hemoglobin concentration following a sequence of brief, rapid arterial cuff occlusions. NIRS measures mitochondrial oxidative function as the mVO2 recovery rate constant k. In the absence of blood flow, changes in muscle oxygenation occur via oxygen consumption alone. In persons without RA, this non-invasive approach is highly correlated with muscle respiratory capacity assessed via muscle biopsies using in situ permiabilized fiber bundles and the Oroboros O2k system.

After local anesthesia (xylocaine, 2%) is injected, a small incision will be made in the thigh. Four to six small pieces of muscle about the size of a pea will be surgically removed. The incision site will be closed using steri-strips and/or derma-bond, and a light dressing applied.

Body composition assessments include circumference measurements and the BOD POD®. Minimal waist circumference measurements will be taken using a tape measure.

Cardiorespiratory aerobic capacity (VO2 peak), will be assessed using a maximal treadmill test protocol with cardiopulmonary gas exchange. Subjects will be asked to exercise on a treadmill to their perceived maximum ability and effort during which time they will have a mouthpiece in their mouth to determine maximal oxygen use/consumption through breathing. For safety purposes the subject will be monitored by electrocardiogram (ECG) and their blood pressure will be measured at rest and throughout the exercise phase of this test.

Strength assessments will include dynamometry-assessed grip and quadriceps strength (Cybex HUMAC NORM, Comp Sports Med, Inc., Stoughton, MA) tests

Measures include global health, pain, fatigue, physical function, self-efficacy for disease management and sleep.

Passive skeletal muscle stiffness and elasticity measurements of bilateral biceps brachii, flexor carpi radialis, vastus lateralis, and tibialis anterior using mechanical deformation with myotonometry using the MyotonPro device.