A resistance system for an exercise device may include: a drive shaft configured to be operably connected to a movable part of an exercise device such that movement of the movable part causes the drive shaft to rotate; and a resistance source operably connected with the drive shaft and configured to resist rotation of the drive shaft. An exercise device may include: a drive shaft rotatably supported by a frame; a resistance source operably connected with the drive shaft and configured to resist rotation of the drive shaft; and first and second treadle assemblies pivotally connected with the frame and including respective moving surfaces. In such an exercise device, the first treadle assembly and the second treadle assembly may be operably connected with the drive shaft such that pivotal movement of the first treadle assembly and pivotal movement of the second treadle assembly cause the drive shaft to rotate.