You have asked a very good question that may not have an exact answer. In the presence of disc disease, exercises can indeed make the situation better or worse. The trick is to keep moving without stressing or overloading the compromised discs.
Care should always be taken to avoid vigorous or sustained loading at the end range of trunk motion. In other words, don’t stay in one position too long. And don’t go to the end range of full flexion or extension and hold that position.
In general, vigorous exercise is not recommended until healing has occurred. The first place to start may be with lumbar stabilization exercises. You may have heard these referred to as core training. The trunk (back and abdominal) muscles are targeted. Strengthening the core improves the spine’s ability to handle loads that might otherwise cause injury.
Timing of the exercise program is also important. In the early morning, the discs are full of fluid and less able to withstand extremes of flexion and extension. It’s best to delay loading the spine until you’ve had a few hours to move about. Movement squeezes some of the excess fluid out of the discs. This makes it less likely that a bulging disc will press against the sensitive spinal nerve roots.
If you are having trouble finding the right exercise program, consider making an appointment with a physical therapist. The therapist can guide you through the process of starting and progressing an appropriate exercise program.