Participants in this arm will have Inclusion Body Myositis (IBM). All patients will have EIM measurements of selected muscles.

Participants in this arm will be healthy controls. All participants will have EIM measurements of selected muscles.

EIM is a measure of impedance. EIM is a measure of the obstruction of flow of current through the tissue. It is a completely painless assessment of muscle health.

Physical functioning in daily life will be measured using the IBM-Functional rating scale (IBM-FRS). IBM-FRS will be obtained for both IBM participants and healthy controls.

Grip strength will be assessed using the Jamar hand dynamometer and will be obtained by the physician from both IBM participants and healthy controls. The best of three attempts will be used.

Time to stand will be measured using the "Get-up-and-go test". Time will be measured for a participant to stand up from a chair (using arms if necessary), walk 3 meters, turn around, return to the chair, and sit down. The better of two trials will be used. These results will be obtained by the physician from both IBM participants and healthy controls.

Distance walked by a participant in 6 minutes will be measured. Given the general disability of many IBM participants, rather than utilizing two trials, a 2-minute "practice" walk will be performed before the actual test, to familiarize the participant with the task to be performed. Both IBM participants and healthy controls will undergo this procedure.

This is a hands-on assessment that will use the Medical Research Council muscle scales (MRC) to score the strength of the following muscle groups that may be involved in IBM: neck flexor, extensor, deltoid, biceps, triceps, wrist extensor, wrist flexors, finger long and short flexors, finger extensors, hip flexors, hip adductors, hip abductors, knee extensors, knee flexors, ankle dorsi and planti flexors. MRC scores will be obtained by the physician from both IBM participants and healthy controls. A global score can be calculated and will be used. 0 (none) = no contraction, 1 (trace) = visible contraction with no motion, 2 (poor) = full range of motion, gravity eliminated, 3 (fair) = full range of motion against gravity, 4 (good) = full range of motion against gravity, moderate resistance, 5 (normal) = full range of motion against gravity, maximum resistance.