Why do doctors often prescribe muscle relaxants? Is it to treat the muscle spasms?

muscle spasmsInterestingly, one of the most commonly prescribed muscle relaxants, Cyclobenzaprine (Flexiril), is not fully understood. You would think that medical doctors would know exactly which patients they should be prescribed for. But most of the time unfortunately, it is a guess who will respond to muscle relaxants. In my clinic as a Nanaimo Chiropractor, I have always found it interesting that patients tell me that the muscle relaxants that were prescribed has helped with the muscle spasms. Others, it doesn’t make a difference at all. Why and what is going on?

In a recent research paper, some revealing information has surfaced and is in line with what I have been thinking all along. As you know, animal models are important in our understanding of human spine. Sheep are known to be quite close to our own human make-up and they are studied quite extensively. In this recent study, pressure transducers were inserted into the spinal discs and the internal pressures of the discs in the spine were measured throughout the day and night. This has never been done in animals so it was something that needed to be done to compare to the human data we have. Intradiscal (within the discs) pressure has always been at the root of spine pain, especially when the pressures are too high and cause damage. This often occurs with heavy lifting especially when bending forward in flexion.

There were several interesting points that were revealed in this study. One was that the internal pressures inside the sheep’s spine was found to be 2-4 times higher when compared to humans. This, for me, was intuitively backwards as I thought being in a horizontal or quadruped state would decrease the internal pressures in the discs. One would think that being vertical, like we are in humans, would put greater pressure into the discs on the lower spine as they support the weight above. But this is apparently not the case when we compare to our quadruped friends. As it looks, this study indicated muscle contraction to hold the forelimbs and hind limbs together, to prevent the spine from sagging, is significant enough to increase the intradiscal pressure 2-4 fold.

This is very interesting because a lot of the rehabilitation exercises, like dead bug and quadruped, uses concepts of being horizontal while minimizing spinal compression.   Now, the really interesting finding in this study was during the surgical procedure of implanting the pressure tips. During this time when the sheep were anesthetized, the intradiscal pressures were lowest and were thought to be found because of the anesthetic medication used. Muscle relaxants were administered. In other words, the drugs looked to reduce the intradiscal pressures!

Muscle Contraction vs. Muscle Relaxation and Disc

muscle spasms - diagram

So the next time your medical doctor prescribes you medication, and you respond positively to them, I am going to suggest it is because the muscles relax a little to decrease the intradiscal pressure. The disc is the most common cause of low back pain, not the muscles. We know this for sure.