A cushion device for treadmills includes a frame with two rails and a deck has an end pivotably connected to two respective first ends of the two rails of the frame. Two tubes are connected to the two rails of the frame and two activation rods axially extend in the two tubes and are restrained to only can spin relative to the tubes. Each of the two activation rods has a nut member threadedly connected thereto and a slide member is slidably mounted thereto. A spring is mounted to each of the two activation rods and biased between the nut member and the slide member. Two cables have two respective first ends fixed to the slide members and two respectively second ends of the two cables extend through each tube, reeve through the lower pulley and the upper pulley and are fixed to the first end of the deck.
