A treadmill comprising: a frame; a looped running belt; a first roller assembly comprising a first roller tube, a first rotating pulley and a second rotating pulley mounted on the first roller tube so that the first and second rotating pulleys rotate together with the first roller tube, a first shaft fixedly mounted on the frame so that the first shaft does not rotate with the first and second rotating pulleys and the first roller tube, a first load bearing, a second load bearing, and a one-way device, a first insert between (a) outside of the first load bearing and the outer ring of the one-way device and (b) inside of the first roller tube, the first insert being on a first end of the first shaft, and a second insert between (a) outside of the second load bearing and (b) inside of the first roller tube, the second insert being on a second end of the first shaft; and a second roller assembly mounted on the frame; wherein: the looped running belt is supported by the second roller assembly, the first rotating pulley, and the second rotating pulley, so that the first and second rotating pulleys rotate with movement of the looped running belt; the first load bearing and the second load bearing are disposed between the first roller tube and the first shaft, so that the first roller tube and the first and second pulleys can rotate around the first shaft; the one-way device comprises an inner ring and an outer ring, the inner ring being fixedly coupled to the first shaft not to rotate on the first shaft, the outer ring is fixedly coupled to the roller tube to allow the roller tube to rotate in a first direction around the first shaft and to prevent the roller tube from rotating around the first shaft, in a second direction that is opposite to the first direction, the first and second directions being such that top surface of the looped running belt can move from front of the treadmill to rear of the treadmill and the top surface of the looped running belt is prevented from moving from the rear of the treadmill to the front of the treadmill. a frame; a looped running belt; a first roller assembly comprising a first roller tube, a first rotating pulley and a second rotating pulley mounted on the first roller tube so that the first and second rotating pulleys rotate together with the first roller tube, a first shaft fixedly mounted on the frame so that the first shaft does not rotate with the first and second rotating pulleys and the first roller tube, a first load bearing, a second load bearing, and a one-way device, a first insert between (a) outside of the first load bearing and the outer ring of the one-way device and (b) inside of the first roller tube, the first insert being on a first end of the first shaft, and a second insert between (a) outside of the second load bearing and (b) inside of the first roller tube, the second insert being on a second end of the first shaft; and a second roller assembly mounted on the frame; wherein: the looped running belt is supported by the second roller assembly, the first rotating pulley, and the second rotating pulley, so that the first and second rotating pulleys rotate with movement of the looped running belt; the first load bearing and the second load bearing are disposed between the first roller tube and the first shaft, so that the first roller tube and the first and second pulleys can rotate around the first shaft; the one-way device comprises an inner ring and an outer ring, the inner ring being fixedly coupled to the first shaft not to rotate on the first shaft, the outer ring is fixedly coupled to the roller tube to allow the roller tube to rotate in a first direction around the first shaft and to prevent the roller tube from rotating around the first shaft, in a second direction that is opposite to the first direction, the first and second directions being such that top surface of the looped running belt can move from front of the treadmill to rear of the treadmill and the top surface of the looped running belt is prevented from moving from the rear of the treadmill to the front of the treadmill. the looped running belt is supported by the second roller assembly, the first rotating pulley, and the second rotating pulley, so that the first and second rotating pulleys rotate with movement of the looped running belt; the first load bearing and the second load bearing are disposed between the first roller tube and the first shaft, so that the first roller tube and the first and second pulleys can rotate around the first shaft; the one-way device comprises an inner ring and an outer ring, the inner ring being fixedly coupled to the first shaft not to rotate on the first shaft, the outer ring is fixedly coupled to the roller tube to allow the roller tube to rotate in a first direction around the first shaft and to prevent the roller tube from rotating around the first shaft, in a second direction that is opposite to the first direction, the first and second directions being such that top surface of the looped running belt can move from front of the treadmill to rear of the treadmill and the top surface of the looped running belt is prevented from moving from the rear of the treadmill to the front of the treadmill.