An advanced sexual maneuver. First, make a girl run on a treadmill till she has to take a shit. Then fuck her in the ass and till your dick is covered in shit. Then have her squeeze her legs together. Fuck her squeezed together sweaty legs till you get to the arches of her feet. Fuck the arches of her feet till you skeet.
Merry Christmas dear, its a new treadmill, now we can do the Rusty Sawmill without you having to do so many squat-thrusts.