My pal Ian at MEL Magazine came to me with an interesting question. How taut does your butt need to be to bounce a quarter off it? While I had to defer to Alex Klotz, a professor in the department of physics and astronomy at California State University, Long Beach, with the technicals of the "Coefficient of Butt Restitution", as a booty-building specialist I lent my tips for "firming up dat ass" you may find helpful.