In this video, you will learn how to do an adductor ball squeeze with hip flexion by Dr. Brian Damhoff.
1. Lay on your back with your legs at 90/90
2. Place a ball or similar object between your knees
3. Squeeze your knees together
I like starting with a simple 30-second isometric squeeze or a 3×10-second squeeze where you go hard for 10 seconds then rest 10 seconds and then do that 3 times total. But, you can vary the squeeze duration and intensity based on your needs.
The nice part about using something like a volleyball is as you get stronger, it will still provide an adequate challenge as it has unlimited resistance.