Isometric hip adduction combo (Hip adduction series - Squeezing ball with legs straight, legs bent, legs in 90/90, in supine; 01)

Lie on your back with a ball between your knees and legs straight.
Squeeze your knees together, pushing into the ball.
Bend your knees so your feet are flat on the floor and squeeze the ball again.
Lift both legs up until your hips and knees are at ninety degrees and again, squeezing the ball.
You can reverse this sequence back down to the starting position.