An exercise apparatus for cooperating with an exercise ball during performance of core exercises thereon. The exercise apparatus comprises: (i) an exercise platform comprising a framework defining a first opening approximate its proximal end for receiving therein a first padded exercise mat and a second opening approximate its distal end for receiving therein a second padded exercise mat; (ii) an upright framework engaged with the exercise platform framework at its proximal end, the upright framework having a vertically adjustable backplate with an adjustable headrest and an adjustable handlebar grip, a handgrip support rail and a stabilizer bar integrally engaged with the proximal end of the exercise platform; (iii) a first padded exercise mat for demountable installation into the first opening defined in the exercise platform framework; and (iv) a second padded exercise mat for demountable installation into the first opening defined in the exercise platform framework.