You don’t need fancy exercise equipment to strengthen your core. But tools like the Rolling Resistance Core Strengthener could help you push the right areas in your body. The device combines wheels and adjustable resistance bands to work muscles in your body’s core. Just set the desired resistance of the bands, grip each pair of non-skid wheels, and go to work. The device weighs 3 lbs and fits on a closet shelf easily. Sets you back $50.