The coordination of the trunk, limbs, and pelvis during walking is the subject of research today. Advanced technology is making it possible to record movements at different speeds and look for patterns. These movement patterns are then compared for people with and without low back pain.
Researchers have found that at slower speeds the coordination pattern of the trunk and pelvis is the same with or without back pain. When the walking speed increases, the "normal" person (without pain) changes the movement pattern, and movement is no longer coordinated between these two body parts. For the person with back pain, however, the pattern stays the same at all speeds.
This suggests that the person with back pain contracts muscles to hold the spine rigid or locked in one position. Using muscles to protect or guard in this way is called splinting. Once the back pain is gone, the body may not be able to return to normal movement. The protective splinting is no longer needed, but the body is stuck in that phase.
Physical therapists are using this kind of information to develop exercise programs. Specific exercises to "unlock" the spine may be helpful in these cases.