You’ll need a scooter board and a medicine ball and a towel (or carpeted area).
The goal of this exercise is to do these two moves in a combination fashion without much rest at all in between. The first exercise is a switch arm medicine ball push up using a medicine ball and keeping your feet on a scooter board. You should feel this in your triceps and your entire core due to the instability of holding the scooter board in place and holding the plank motion. Aim to do 8-10 reps.
Next, move right into balance work of holding the medicine ball and doing a dual leg mountain climber with your feet on the scooter board for another 8-10 reps. You should feel this in your triceps, abs, and possibly a little bit in your quadriceps. Repeat 3x.
Modifications: 1) Do pushups without the medicine ball (no switch arm). Still keep your feet on the scooter board. 2) Do dual leg mountain climbers without holding the medicine ball. This will make this exercise easier.