Yes, a mini stepper will tone your bum, but only if you use it correctly. Using a mini stepper machine while sitting down on a low resistance will not provide you with enough resistance to effectively stimulate your gluteus maximus (bum) muscles. To get a more effective glute workout, you should use a resistance level that is challenging for you and stand while exercising. Slightly leaning into the stair stepper machine will also accentuate glute activation.