Bridging with adduction stabilisation ("Bridge" Core/gluteals strengthening, squeezing ball; 01)

Lie on your back with your knees bent and your feet flat on the floor.
Place a medium sized ball between your knees.
Flatten the small of your back against the floor.
Tighten your buttock muscles, squeeze your knees together and lift your hips up.
Keep your hips level as you hold this position.
Maintain the pressure on the ball as you lower your hips back down to rest.