A hollow golf club head having face end and tail ends, a strike face at the face end, a crown, a sole, and a structural response modifying constraining member having first and second ends, the second being forward of the first and spaced from the strike face, the constraining member extending vertically and in contact with the sole and the crown at its first and second ends, and extending horizontally distance that is substantially less than the sole length, when the club head is in address position.