Most people do dumbbell chest flys on a bench, but I don’t like it because my arms can go too far back and the last time I did chest flys on a bench my left arm bent backwards and the weight dropped to the floor. That hurt.
Now I do chest flys on a ball. It’s nice and cushy on my back. I can use heavier weights and I engage my glutes, hamstrings and abs. Sweet!
Roll back onto the ball with shoulders, head and neck onto the ball. You should be in bridge with feet about hip-width apart. My trainer has me doing five chest flys and then alternating chest flys which works balance and core too.
Now you have something to do on that ball that’s sitting in the corner collecting dust.