An exercise device can include a pair of pedal members, each of which can be rotatably connected on at least one end to a planet gear that is rotatable about a sun gear on each side of the device. The pedal members and the planet gears can be rotated to provide an elliptical exercise motion. The device can include a mechanism for simultaneously rotating each of the sun gears together to change the orientation of the elliptical exercise motion relative to a user. The orientation of an elliptical exercise motion can be changed dynamically from one orientation to another, for example, from horizontal to uphill or downhill, during a particular workout period. The exercise device can change the orientation of an elliptical exercise motion while maintaining a user's ankles at a substantially constant angle during the exercise cycle.