Apart from being useful for fitness, treadmills are also used for medical applications. One common medical use of a treadmill is the treadmill test. In this test, doctors make you run on a treadmill for a set period of time while monitoring your body. And this allows them to check for any abnormal signs. If you have arrhythmias, that is abnormal heart rhythms, then it can be easily diagnosed using the treadmill test.