Hands on a ball that wants to roll, core that refuses to let it.
Squeeze the ball gently and brace your core, the wobble is the workout so stay rigid.
Pressing off a ball that wants to escape in every direction turns the push-up into a stability contest: the chest still drives the rep while the triceps and shoulders work overtime steering the ball as they assist. Squeezing your hands into the sides adds an inward pressing element floor push-ups do not have. The control it builds shows up later in your dumbbell pressing.
Much harder, because force that would normally move you now goes into stopping the ball wobbling. If your floor push-ups are not crisp yet, build them first, the ball punishes shaky pressing.
A fully pumped ball is rounder and wobblier, letting a little air out flattens the contact area and makes it slightly more forgiving. Start softer, progress firmer.
Drop to your knees while keeping the same straight line from knees to head. It shortens the lever while you learn to control the ball, then walk back out to a full plank position.
