The Best Equipment For Core Strength and Balance: Gaiam Balance Disc If machines aren't quite what you're looking for, you might find yourself interested in the Gaiam Balance Disc ($28). This cushion helps strengthen the core and improve balance as you sit in a chair all day. If you're someone who wants a strong core but can't find time to do a quick plank throughout the day, this could be a quick and easy solution! Image Source: amazon.com Gaiam Balance Disc $28 from amazon.com Buy Now