In addition to giving a recovery from vertical flight, "humps" provide an excellent platform for vertical rolls, up and down, and  a convenient way to rebuild airspeed (it is not necessary to begin and end at the same altitude). 

This animation depicts the most common form of the Humpty Bump: a "pull-pull-pull," composed of three Positive G changes of direction. Another common variant  involves a "push" across the top instead of a pull.