Systems and methods are presented for performing exercises to strengthen, e.g., the transversus abdominis and related muscles. The systems and methods may involve one or more independent belts, allowing a full range of continuous motion. The systems and methods may further use a resistance-control mechanism that allows a user to adjust the force required to move the one or more belts, thereby controlling the rate of motion in the forward and/or backward directions. The systems and methods may further use a unidirectional resistance mechanism that allows the user to increase the resistance of the one or more belts in one direction, while allowing the one or more belts to move freely in the other direction.