Abstract: An assembly is disclosed. The assembly is movably-disposed upon an underlying support surface. The assembly includes a body having an upper surface and a lower surface. The body defines a pair of front axle-receiving openings and a pair of rear axle-receiving openings. A front axle member extends through the pair of front axle-receiving openings. A rear axle member extends through the pair of rear axle-receiving openings. A first front wheel is connected to a first end of the front axle member. A second front wheel is connected to a second end of the front axle member. A first rear wheel is connected to a first end of the rear axle member. A second rear wheel is connected to a second end of the rear axle member. The upper surface of the body is pitched at an angle with respect to the underlying support surface. An exercise system is also disclosed. A method is also disclosed.