1. An electric treadmill, comprising:a base comprising a front frame, a rear frame and a connecting assembly, wherein tread boards are provided within the front frame and the rear frame, and the front frame and the rear frame are hinged together by the connecting assembly to enable the base to be folded; and
an armrest comprising a vertical tube and a cross tube, wherein one end of the vertical tube is connected to the cross tube, and an other end of the vertical tube is rotatably coupled to the base to fold the armrest with respect to the base,
wherein the vertical tube comprises an armrest tube, a side rest is detachably connected with the armrest tube, and a connecting portion is provided on the armrest tube, corresponding to the side rest;
wherein the side rest comprises a main body, a spring is provided at an end of the main body, and a ball connected to the spring; and the ball is abutted against a connecting portion by a force of the spring;
wherein the vertical tube further comprises a hollow tube, and a controllable gas spring, wherein the armrest tube is disposed in the hollow tube, one end of the controllable gas spring is connected to the armrest tube, and an other end of the controllable gas spring is connected to the hollow tube, and the armrest tube is telescoped relative to the hollow tube to adjust a length of the armrest; and
wherein a tab is further provided at the end of the main body; a slot is provided on the connecting portion; and the tab is inserted into the slot to connect the main body to the connecting portion.