A fitness apparatus which allows for simultaneous strength training and core muscle building/strengthening, the apparatus incorporating an inflatable exercise ball. The apparatus includes a base which allows for selectively controlling the lateral movement and compressibility of the ball while performing various exercise routines. Also incorporated in the base are adjustable resistance training devices which allow for a variety of strength training, the resistance training devices allowing routines ranging from very light to sufficiently strenuous to challenge advanced users. The apparatus is collapsible and stowable, and may be used without the exercise ball to facilitate both strength/flexibility training, as well as aerobics.