A support deck for a treadmill is disposed under an upper stretch of an endless tread belt to support the tread belt and a user thereon. The support deck includes a plurality of indentations on a top surface thereof. Lubricant or lubricating oil is received in the indentations for lubrication between the support deck and the tread belt, thereby reducing friction between the support deck and the tread belt. Thus, the wear of the tread belt decreases, and the life of the tread belt increases. Moreover, the support deck may further include a plurality of ridges on the top surface thereof to offer foot reflexology.