A muscle-back iron golf club head includes a blade-like upper mass, a muscle-like lower mass, a planar front surface, a top surface, a sole surface, a heel surface, a toe surface, and a rear surface having a first contour. A recess is in the rear surface, the recess having a first portion in the blade-like upper mass and a second portion in the muscle-like lower mass. An insert may be provided in the recess, and such insert may substantially fill the recess and may include a back surface having a second contour which is different from the first contour of the club head rear surface.