Depending on what problems you have, it's always wise to talk with your doctor or another health professional before starting up any new exercise regime or investing in a home treadmill. However, in general, walking or running on a treadmill is not bad for your back and will not make your back pain or problems any worse. In fact, treadmills are often recommended for those who suffer from back pain or back injuries as walking on a treadmill is a safe and gentle form of exercise that can actually improve your posture, strengthen your spine, and aid in losing weight that might be contributing to your current back issues. Exercising on a treadmill can even trigger the release of natural pain relieving chemicals in your brain, helping back pain fade away and providing comfort and relief when you need it.