According to an embodiment of this invention, a treadmill is disclosed with a conveyor belt, two assistance devices, and at least a first control member. The two assistance devices are respectively arranged at a side of the conveyor belt with each assistance device comprising a handrail and two supporting bars, and each supporting bar couples to the handrail via a connecting assembly. The first control member is used to lock or release the connecting assembly, so as to adjust the distance between the two handles of the two assistance devices.