This is one of my favorite exercises to do on arm days. It not only works your arms but also your core, butt and legs. Not to mention it builds stability. It’s a little difficult and does take a bit balance so be careful if it’s your first time trying.
Get in a pushup position and put one foot on the ball at a time. Find your balance then raise your hips and pull your knees in to your chest. I typically do 4 x 15. That alone gets my arms and abs burning. 💪🏻