A new and improved exercise treadmill may include a frame having a first end and a second end, wherein the second end is parallel to the first end. Two sidewalls interconnect the first and second end. The treadmill may further comprise a motor in order to drive a belt, which is trained over a front roller and a rear roller. A deck is positioned underneath the belt in order to support the user. The treadmill may also comprise a belt tensioning device, which provides a visual indicator so that the rear roller may be moved on each end in equal distance relative to the front roller. Another feature of the invention is a slot between the side rails and the frame so that an extended member can be inserted therein to lubricate the belt.