Nap Time for Spinal DiscsResting Spine Hydraulics


Many of you heard me recommend napping as a form of spinal exercise. I often get that puzzled look from patients: “A nap for an exercise?” Yes, I say, and let me explain why.


Most forms of spine pain come with a prerequisite of spine compression. I was reading another recent research paper (titled: Role of biomechanics in intervertebral disc degeneration and regenerative therapies: what needs repairing in the disc and what are promising biomaterials for its repair?) of spine back pain and yet again, the most common theme is intervertebral disc height loss. To refresh your memory, and I apologize to those that have this down pat, the intervertebral discs are those soft tissues that span (inter) between the vertebrae (vertebral). This is where the word has been derived from. These discs are supposed to constitute a third of the spine but usually in those that have spinal problems, this is not the case and very often in these people the discs can make up much less—hence the common theme in research papers of this intervertebral disc height loss.



So what causes the discs to lose their height in the first place? To understand this, you have to take a tour inside these structures and find out how they are made and what they like and don’t like.


First off, discs are very unique on several fronts. They are made of three types of cartilage. The nucleus pulposus is probably the most important of the three as it is the most central and designed to resist compression. The annulus fibrosus, which wraps the nucleus, is made of alternating fibrous bands at 30 and 60 degrees and is designed to resist tensile stretch. Finally the endplates, which sandwich both the nucleus and annulus, protects the bone and is the nutrient route source for food supply to all components of the disc. The discs do not have any blood vessels so it relies heavily on the passive diffusion of nutrients.



The nutrient route to the disc is critical and is related to why I recommend naps for the spine. Over the course of the day the discs lose up to 25% of their height. The nucleus, which is mainly water, slowly leaks water out through the endplates and the net result is height loss. When discs are already shrunk in height because of injury or arthritis, this loss in daily height will often bring about pain because the bones get too close together which are laden with tiny nerves. Often people report pain at the end of the day and this is due to the approximating vertebrae and associated tissues. The act of lying down helps restore this height.

Over the course of the night spinal discs can gain up to 17-25 mm of height. This happens over the course of the whole 8hr sleep cycle and thought to happen more so during a phase of sleep called REM. During REM the muscles of the body shut off, also known as atonia, for an average period of 5-7 minutes for three or four times over the course of the night. But it is not necessary for someone to be in REM stage of sleep in order to regain heights in the spine. Lying down in itself helps regain spinal fluid to the discs. This is the foundation of why I recommend naps for only 5-7 minutes in the afternoon for my patients. Even if you get a chance to do this once, it is a benefit that is there for the ones that take advantage of it. You don’t need to nod-off, just lie down flat to unload the spinal discs.


There are some research studies that show that prolonged lying down can actually aggravate a spine. The key work is “prolonged”. And a good example of this is the effect of microgravity on astronauts. They can grow up to 6cm of height due to the over filling of the spinal discs. Astronauts require to perform compression exercises to minimize back pain from the discs stretching too far.


The key is in the timing of the decompression on Earth here. Five to seven minutes is optimal and therefore that is why I recommend these short naps for home care.


Discs lose their height with the normal demands of being in the vertical world of gravity but they lose even more height if they get injured. The most common reason discs lose height comes from a torn annulus fibrosus. With the annulus having the big job to contain the central nucleus, a tear will cause a breach in the wall and a leak of the nucleus through fissures. This is very often the source of pain because the annulus have nerves sprinkled throughout.


herniation model


The demands of today’s workplace may not provide many people with the opportunity to lie down. But if there is an opportunity, try it—just for five minutes. Your spine will love you for it. A decompressed spine is a happier spine.


In another blog, I’ll explain why discs in the morning can be quite stiff.


Dr. Jerome Fryer