Treadmills are one of the most popular pieces of cardio fitness and exercise equipment both at home and in the gyms. Treadmills offer the aerobic benefits of walking running, or hiking outdoors, but without having to worry about inclement weather, dangerous traffic, darkness or crime. Often, treadmill training can provide even greater benefits than outdoor training, due to the consistent pace of the treadmill and the ability to alter the elevation and pace to suit your fitness needs.