EIM measurements

EIM measurements were obtained with the Imp SFB7® (Impedimed, Sydney, Australia) attached via cables to a custom-designed handheld array as previously described (Figure 1).¹¹ As with any electrophysiological test, electrode size and positioning will impact the results; details regarding probe size, angle, depth of penetration, and device specifications are discussed in several previous articles.^18-20 Given that the children ranged in age, 3 different sized electrode arrays were employed consistently on a given subject throughout the study. Measurements were performed on six muscles or muscle groups (deltoid, biceps, anterior forearm, rectus femoris, tibialis anterior, and medial gastrocnemius) on the dominant side; if dominance could not be established, testing was performed on the right side. The probe was placed over the bulk of the muscle using measurement paradigms based on boney prominences and other landmarks. Measurements were performed with the array placed longitudinally (current flow parallel to the muscle fibers) and transversely (current flow perpendicular to the major muscle fiber direction).