Abstract
[Purpose] To measure the activities of the upper, middle, and lower trapezius and serratus anterior muscles during shoulder abduction at two angles and compare their relative isolation. [Subjects and Methods] Ten men were enrolled. The tester measured the isolation ratios of upper, middle, and lower trapezius and serratus anterior muscles during shoulder abduction exercises at 60° and 120°. [Results] Neither the upper nor the lower trapezius isolation ratios differed statistically between 60° and 120°. The middle trapezius showed higher isolation ratio at 60° than at 120°. The serratus anterior showed higher isolation ratio at 120° than at 60°. [Conclusion] The upper, lower, and middle trapezius can be strengthened sufficiently with exercises at a low range of angles.