“One of my favorite routines for keeping my rear in good form is to sit down on the floor and 'walk' across it on my buttocks, holding my arms out straight in front for balance, and then 'walk' back again, backwards.
[...]
For more hip improvement - and the waist, too - I lie on my back with my elbows on the floor at my sides. With my legs straight out I make my knees touch the floor on either side, keeping my shoulders and elbows firmly on the floor.
Then I stretch my arms out to the sides, I raise my knees as far as I can and bring them over my left shoulder to my left elbow, and then back and over to touch my right elbow. [...] When you succeeded in touching your elbows with your knees, then try to touch the floor.”