Relationship between ultrasound muscle thickness and MRI-measured muscle cross-sectional area in the forearm: a pilot study.

Previous studies have investigated the relationship between ultrasound-measured muscle thickness (MT) and individual muscle cross-sectional area (CSA); however, the forearm muscle had not yet been studied. The purpose of this study was to examine the relationship between forearm MT by ultrasound and the muscle CSA of the forearm obtained by magnetic resonance imaging (MRI). Ten young and middle-aged adults had both ultrasound and MRI measurements at 30% the distance from the styloid process of the ulna to the head of the radius. Handgrip strength (HGS) was also measured. Strong correlations (P<0·001) were observed between MRI-measured muscle CSA (total and flexor and extensor components) and MT-ulna (ranged r = 0·937-0·946) and MT-radius (ranged r = 0·884-0·891). HGS was also correlated (P<0·001) with forearm MT (MT-ulna, r = 0·877; MT-radius, r = 0·852) and MRI-measured muscle CSA (flexor CSA, r = 0·910; extensor CSA, r = 0·923). Our results suggest that forearm MT is closely associated with MRI-measured forearm muscle CSA in young and middle-aged adults and suggest that ultrasound-measured forearm muscle thickness may be a useful variable for evaluating muscle CSA and function in the forearm.