A mechanical advantage device includes a base, a beam pivotably connected to the base at a fulcrum between a first end of the beam and a second end of the beam, a seat at the first end of the beam, and a load at the second end of the beam. In some embodiments, the mechanical advantage device includes structure, such as a linkage, for effecting oscillation of the beam by shifting weight along the beam. The mechanical advantage device may be a single-person seesaw.