Abstract: An exercise device is described. An exercise device including a body, the body having a top, a bottom, a first end located at one edge of the body, a second end located at an opposite end of the body, and first and second sides extending between the first and second ends; one or more wheels; and an energy storage device applying resistive and restoring force to the wheel. Optionally, a shaft can be present that rotationally locks two or more of the wheels.

Abstract: An exercise device is described which includes a platform having a first end and a second end opposite the first end; first and second wheels, wherein the first wheel is positioned proximate the first end and the second wheel is positioned proximate the second end and the first and second wheels are configured to roll across a surface as the exercise device is displaced along the surface; a first motor configured to apply a first torque to the first wheel where the magnitude of the first torque is related to the distance of the exercise device from a zero position and the direction of the first torque urges movement of the exercise device toward the zero position. Versions are also described with more wheels and more motors.

Abstract: An exercise device is described. An exercise device including a body, the body having a top, a bottom, a first end located at one edge of the body, a second end located at an opposite end of the body, and first and second sides extending between the first and second ends; a first axle connected to a first wheel, the first axle also connected to the body proximate the first end at a first hub; a first spring having a first spring end, the first spring positioned at least partially within the first axle, with the first spring end slidably connected to one of the first wheel and the first hub at a first junction, wherein the first junction is configured to convey torque between the one of the first hub and the first wheel and the first spring end.

Abstract: An exercise device is described. An exercise device including a body, the body having a top, a bottom, a first end located at one edge of the body, a second end located at an opposite end of the body, and first and second sides extending between the first and second ends; a first axle connected to a first wheel, the first axle also connected to the body proximate the first end at a first hub; a first spring having a first spring end, the first spring positioned at least partially within the first axle, with the first spring end slidably connected to one of the first wheel and the first hub at a first junction, wherein the first junction is configured to convey torque between the one of the first hub and the first wheel and the first spring end.

Abstract: An exercise device is described. An exercise device including a body, the body having a top, a bottom, a first end located at one edge of the body, a second end located at an opposite end of the body, and first and second sides extending between the first and second ends; a first axle connected to a first wheel, the first axle also connected to the body proximate the first end at a first hub; a first spring having a first spring end, the first spring positioned at least partially within the first axle, with the first spring end slidably connected to one of the first wheel and the first hub at a first junction, wherein the first junction is configured to convey torque between the one of the first hub and the first wheel and the first spring end.