Electromyographic study of the trapezius (middle portion) and rhomboideus major muscles in free circumduction and pendular movements of the arm.

The authors studied electromyographically the activity of the trapezius (middle portion) and rhomboideus major muscles in circumduction and pendular movements of the arm. They verified that the rhomboideus major muscle presented alternated period of activity and inactivity, while the trapezius (middle portion) muscle showed continuous activity of greater or smaller intensity according to the phases of these movements.