Try utilizing the recumbent bike if you experience chronic back pain. Initially start with a 5-10 minute warm-up producing a light sweat, then into your target zone of between 60-85% of your HRmax. Stay within this for approx 30-60 min.
A commercial level treadmill that folds up for easy storage. Automatic incline and decline, plus a large screen make this a great treadmill for your home gym.