| 摘要 |
A treadmill includes a frame, two tracks, a wheel, two keels and two treads. The frame includes a front portion and a rear portion. The tracks are extended from the rear portion of the frame. The wheel is provided on the front portion of the frame. Each of the keels includes a front end connected to the wheel and a rear end movable on a related one of the tracks. Each of the treads is carried on a related one of the keels.
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