The primary outcome will be measuring muscle stiffness from the biceps brachii using ultrasound elastography, which will be compared between patient groups and control groups. A secondary outcome will be the correlation of muscle stiffness at rest with the modified Ashworth score for elbow flexion. Measures of muscle strength and ultrasound measures of density and thickness will be examined in an exploratory fashion. Elastography of the tibialis anterior will be examined in an exploratory fashion.