Are back bends (extension) bad for a degenerative and moderately bulging disc? does it put more pressure on the disc causing it to protrude more?

Depends on where: The disk is. However, please discuss this with your doctor, or preferably a neurosurgeon. Proper strengthening exercises, especially of your core muscles cam greatly improve low back pain. However, you need to do the correct exercises and perform them properly. A referral to a physical therapist may be helpful.

DDD: Extension of the lower back is usually hard in patients with degenerative disc diseases. I think more than anything it would be discomforting to do this type of exercises and you would normally quit doing it due to discomfort.

Lumbar extension: Extending the back can excentuate narrowing of the spinal canal but at the same time can have a positive effect on lumbar disc herniations (mckenzie technique). Flexion of the spine has has also been shown to be helpful (williams technique) but on biomechanical testing can result in the highest disc pressures. Pay attention to the symptoms and avoid activites or positions that exacerbate the pain.