Close the Door: Gate Control Theory

Special thanks to Bump, Birth and Baby - Doula Support and Birth Photography for contributing the picture! www.spotofserendipityphoto.com

Special thanks to Bump, Birth and Baby - Doula Support and Birth Photography for contributing the picture! www.spotofserendipityphoto.com

You smack your ankle - what do you do? Chances are, you rub or put pressure on it without even thinking about what you’re doing. Or what about when you have a raging headache and put a cool washcloth against your forehead? It helps ease the pain, doesn’t it? Now think about labor and birth.

We’ve all heard it before - that you need to get a massage, use counter pressure and apply hot or cold packs, to name just a few comfort measures for labor. You may have heard it so much, in fact, that you tend to think of it as mumbojumbo natural birth talk - the kind of thing people tell you to do, but that doesn’t really work.

Truth be told, there is fascinating science behind the advice to try massage, heat, cold, counter pressure and water - the same science that is behind you rubbing your hurt ankle or using a cold washcloth on your forehead. It’s called the gate control theory.

According to Marcy White’s book, Teaching, Pregnancy, Birth, and Parenting, “Gate-control is a theory that suggests that the transmission of the pain message, which travels to the brain via small diameter nerve fibers, can be modified or inhibited by stimulating large diameter nerve fibers..” (1) Simply put, gate control theory states that stimulating nerves that do not transmit pain signals can interfere with, or even override, signals from pain fibers. Brought to light as a theory in 1962 by Ron Melzack and Patrick Wall, the concept of gate control has been extensively studied throughout the years and is still used to explain many facets of pain.

There are two types of sensory nerves, also called afferent, that transmit pain messages to the brain: A-delta nerve fibers and C-fibers. As their name suggests, sensory nerves bring sensory information from parts of the body to the spinal cord. A-Delta nerve fibers are the immediate, acute pain messengers. They transmit pain to the brain quickly - at about 40mph. C-fibers, in the other hand, carry slower, continuous pain messages to the spinal cord at about 3 mph. They are known as "small diameter" fibers and tend to be the transmitters of chronic pain.

There's another nerve that comes into play here, too - noninceptive fibers. They don't transmit pain. Instead, they transmit the sensations of pressure, heat, cold and touch. Noninceptive fibers, also called large diameter nerves (not to be confused with thick fiber A-Delta nerves), travel faster than sensory nerves and tend to override them.  

How do large diameter nerves override sensory nerves? Large diameter fiber activity stimulates inhibitory cells. These cells tend to inhibit transmission (pain) cell activity. In other words, the more large fiber activity relative to thin fiber activity...the less pain is felt.  Because of this, "In theory, the gating mechanism is activated by massage, pressure, hot and cold applications, which stimulate large nerve diameters in order to modify or inhibit the pain impulse before it reaches the brain." (2) 

http://commons.wikimedia.org/wiki/File:Gate_control_no_A.svg

http://commons.wikimedia.org/wiki/File:Gate_control_no_A.svg

Now, all of this sounds a bit complicated and abstract, so let's talk examples. When you hit your elbow, rubbing it often seems ease the discomfort (try this next time you bang a limb). Why? Because rubbing the affected area activates noninceptive nerves that are even "faster" than the sensory nerves. These noninceptive fibers send information about pressure and touch that reach the spinal cord and brain to override some of the pain messages carried by the A-delta and C-fibers

And if all that wasn't amazing enough, your brain can actually interpret different types of pain. For example, when you put on a pair of shoes that is just a little too tight, you quickly tend to forget the discomfort. Or try pinching some skin with a clothespin. It hurts quite a bit at first but eventually the pain fades. This is your brain interpreting these pain signal as nonthreatening. So if the sensation isn’t going to hurt you, your brain often doesn’t bother letting you know about it!

In a normal unmedicated birth, the pain of labor isn’t pathologic. It’s actually productive, signaling your body how much oxytocin to make, when your body needs you to push and when something is wrong.

So what does all this scientific talk mean for birth?

It means, that unlike a lot of advice people give, you should actually get a massage, use counter pressure, water, hot and cold for comfort during labor. It actually works because all these actions stimulate large diameter nerves, which override pain signals.

When using gate control theory to ease the discomfort of labor, keep a few things in mind. First, large diameter nerves habituate faster than small diameter nerves. That means that getting your back massaged may work like a charm for about twenty minutes and then suddenly "stop". That's just your body's way of saying it is time to try something else. Second, it can be helpful to use visualization techniques or focal points as you try the gate theory because this focuses you and can help distract you from the discomfort.

What questions do you have about gate control theory? Did you apply the concepts in your labor? Start the conversation below!


Special thanks to Bump, Birth and Baby - Doula Support and Birth Photography for contributing the picture! Please check out here website www.spotofserendipityphoto.com and give her a "like" on Facebook! https://www.facebook.com/pages/BUMP-BIRTH-BABY-Doula-Support-and-Birth-Photography


Sources

(1) Teaching, Pregnancy, Birth, and Parenting, Marcy White, page 112

(2) Teaching, Pregnancy, Birth, and Parenting, Marcy White, page 113

http://en.wikipedia.org/wiki/Gate_control_theory_of_pain

http://psychology.about.com/od/gindex/g/gatecontrol.htm

http://www.spine-health.com/conditions/chronic-pain/modern-ideas-gate-control-theory-chronic-pain