Abstract: A treadmill contains a body, a support assembly, a resistance unit, and a stop strap. The body includes a holder and a circular running belt. The support assembly includes multiple posts and two columns, wherein each column having a slidable space, and the slidable space having two first chutes. A resistance unit includes two sliding devices, two limitation structures, and a force exerting element. The respective sliding device has a slider and multiple first rollers. The respective limitation structure includes two cylinder units, a resilient unit, a first fixing unit, and a second fixing unit. The force exerting element has two connection rods connected on two ends thereof, and the respective connection rod of the force exerting element is coupled with the coupling portion of the slider of the respective sliding device.

Abstract: A magnetron mechanism of an unpowered treadmill contains: a driving body, a one-way transmission element, and a magnetron mechanism. The driving body includes a frame, a connection fence, a front wheel assembly, and a connection shaft. The one-way transmission element is mounted on the connection fence of the frame. The magnetron mechanism is fixed on the connection fence and includes a rotary shaft, a drive wheel, a driven wheel, a belt, a flywheel, a resistance element, and an adjustment unit. The resistance element has a pair of fixing sheets and multiple magnetic parts. Each of the multiple magnetic parts has a rotatable connection portion. The adjustment unit has a steel cable, an end of which is connected with the resistance element so that the steel cable pulls the resistance element to swing along the rotatable connection portion.