Abstract: A linkage structure of a treadmill, including a frame assembly and two tread board racks pivotally disposed on the frame assembly side by side. Two buffering cylinders are disposed between the tread board racks and the frame assembly. Two support arms are respectively pivotally connected with the tread board racks and slidably mounted in the frame assembly. The support arms are respectively pivotally connected with two linkages. Two ends of the two linkages distal from the support arms are respectively pivotally connected with two ends of a linking rack. The linking rack is pivotally mounted in the frame assembly. Via the support arms, the linkages and the linking rack, the side by side arranged tread board racks are drivingly connected with each other to move in reverse directions.

Abstract: A height adjusting device includes two lifting arms pivotally mounted to a main frame of a treadmill. Each lifting arm has a first end pivotally mounted to the main frame and a second end upwardly extending therefrom. The second end of each of the two lifting arms is pivotally connected to two opposite sides of the platform. A lateral rod has two opposite ends respectively secured on the two lifting arms such that the two lifting arms are synchronously operated and a pivot seat formed on a middle section of the lateral rod. A telescopic rod has a first end pivotally connected to the pivot seat and a second end pivotally mounted to a bottom of the platform for reciprocally driving the lateral rod and the two lifting arms to adjust a height of the platform.