While I would agree that strengthening exercises are not necessarily the best solution for low back pain, I would also venture that most of the exercises in the Copenhagen protocol may not be appropriate for all types of low back pain. Some of them are great while some of the others are known to have high spinal loading values (e.g. crunches, modified or not).

The key to resolve low back pain is to figure out what the cause is. Each person will have a different or unique cause for their pain and dysfunction. Some people won't tolerate flexion or extension. Some won't tolerate compression or shear forces. Once these causes have been elucidated, it's about removing them as much as possible to allow the injured tissues to heal.

In most cases, I would actually avoid stretching the low back while working on lumbar spine stability and hip mobility. Instead of focusing on low back strength, I would focus on core muscle endurance capacity (this includes the muscles of the low back).

I have written quite extensively on low back pain and possible solutions on my blog at http://devchengkalath.com. I've also compiled videos of some of the exercises I use with my clients in clinical practice.

Hope that helps.

Regards,
Dev Chengkalath
http://devchengkalath.com