A treadmill includes a front leg frame and a connecting arm. The front leg frame has a front end pivoted to a support base. The connecting arm has a lower end pivoted to the leg frame. An upper end of the connecting arm is connected to a threaded sleeve connected telescopically to a motor-driven screw rod disposed at a top side of a tread base. A hydraulic telescopic unit is pivoted to the leg frame and the support base. When the threaded sleeve is driven by the screw rod, the tread base is inclined. When the tread base is folded upward, it is held in position by the hydraulic telescopic unit which is prevented from moving telescopically by engagement with a latch member. The latch member disengages the telescopic unit through a release member provided on the tread base.
