Do you enjoy doing other things like watching t.v. or reading while you walk on your treadmill? Make sure your attention isn't being diverted from the task at hand. Pay especially close attention to your form and posture. Is watching t.v. causing you to bend forward? If reading is slowing down your pace, try forgoing the reading material a time or two to see how much faster you are easily able to walk when you're not distracted - chances are you walk better and at a steadier pace.