This exercise combines upper and lower register with dynamics from quiet to loud. The aperture between the lips is thereby adjusted from maximun to minimum size. The exercise improves your endurance because you'll have to keep the embochure together with your facial muscles throughout the exercise. Play the loudest part only that loud that you can keep it so, don't overblow and don't let the air escape from the corners of your mouth. Keep the pitch constant.
Sound example: dynamics exercise 1, Tempo=60
created by jjs
You can continue as far as you want as long as you'll avoid excessive mouthpiece pressure.
Caruso, Carmine: Muscial calisthenics for brass