You need to buy a treadmill lubricant that works best for your machine (you can contact customer services for help), according to NordicTrack. Unplug your treadmill, loosen the belt, and lift the belt up. Spray the lubricant underneath. Then, lower the belt and switch on the machine to a slow speed for several minutes. Wipe off any excess lubricant and tighten the belt back into place.