Part of a pop song on the simpsons in which 3 women chant it in a slow, kind of egyptian fashion. This is really just join the navy spelled backwards, designed for subliminal advertizing.
(Otto waiting for Navy bus)
Lisa: Hey Otto, what are you doing?
Otto: I dunno, I just got this craving to join the navy. Yvan eht nioj! (gets on bus)
While our lifespan is the number of years we will live, our healthspan is the number of healthy years we will have and our sexspan is is the number of years we will continue to be healthy enough to continue having an active sex life.