The hip lift is done laying on the ground with your feet up on a hard surface, and your knees and hips at 90 degrees. What you’re going to do is push your heels hard into the chair to pick your bum up off the ground about four inches, or the height of your fist.
This is done slowly. It’s a slow exercise, it takes two seconds to go up, one second to hold, and then two seconds down.
When you come down you’re going to touch the floor, but not relax. And you’re going to repeat that for a set of 15.
When you get good at doing that with two legs, you can do it with one leg. Where you pick one foot up off the chair, and using the other leg, repeat the process. Push your heel into the chair, and pick your bum up off the ground for four inches again doing it very slowly.
This exercise engages the hamstrings, and will help strengthen your posterior chain.