Abstract: An isotonic exercise assembly structured to exercise the retractor muscles, such as but not necessarily limited to the rhomboid muscles, in the upper torso of a user's body in an effort to correct poor posture demonstrated by the user. A mounting assembly is provided and structured to be removably attached to the upper torso, and is supportingly attached to a base of the exercise assembly. A pair of arms, are pivotally attached at their respective distal ends to the base in spaced relation to one another and are selectively positionable between a retracted position and an outwardly extended position. A tension assembly is disposed relative to the base and the pair of arms, and exerts a resistance force on the arms tending to normally bias the arms into the retracted position.