Bed Assisted Squat
You have to test the springs on your bed somehow so why don't you use these squats to see how much spring the bed has? If it sinks down too much and you cant get yourself back up, you know it's time for a new bed. Squats get your legs more limber and especially strengthen up your glutes, hamstrings, quads and calves.
While standing by your bed, get yourself a little away so you have to reach your bottom back to make it onto the bed. Your first motion should be to bring your bottom back like you are going to sit down and bend your knees. Keep yourself upright and try to touch your bottom down onto the bed before coming back up to standing.