Pulling on nerves for fun and therapy

Neurodynamic stretching (AKA neural mobilization and AKA neurodynamics) is a technical type of stretching, a loose collection of experimental stretching and positioning treatments for neuropathy. It’s based on the idea that “unhappy” nerve tissue can be cheered up, which sounds like I’m making fun of it, but not really: this is an interesting old idea, a bit obscure, but worthy of consideration.

Although this kind of stretching is mostly not a DIY thing, here’s one simple example anyone can understand: toe touching stretches for sciatica. That position puts tension on the sciatic nerve itself.

I wrote a review of neurodynamics last year, and reader Brenden T. pointed out that I’d missed a key point about why sensible therapists might be trying to stretch nerves: not so much the usual story about “freeing” nerves from “adhesions” (which might not exist) and more just for the value of neural stimulation. Motion is lotion.

I agreed. This post is my clarification.

A humbler goal: maybe it’s just nerve exercise?

The goal of neurodynamic stretching is to stretch nerve tissue specifically — not muscles.

Rather than breaking icky sticky adhesions, maybe the point of neural mobilization is to pull on nerves without optimizing for “glide” of the nerve within its sheath to break adhesions. Any old pulling will do, as long as it pulls on nerves of clinical interest, because it’s just a way of stimulating them, and stimulation is a Good Thing. “It is known.”

And maybe it is, and maybe it’s good enough, and that is probably all that many pros ever had in mind.

Everything in physiology really does seem to thrive on just-right levels of stimulation. And stagnancy of nerve tissue itself — not just the tissues they are connected to — might actually be a factor in neuropathy, an exaggerated version of how uncomfortable we get when stuck in one position for too long

Do nerves need their own exercise?

Stretching nerves just to stimulate them seems more plausible to me than “it’s all about the entrapments,” but it’s still far from a slam dunk. I don’t think anyone doubts that stimulation is good for nerves in some sense, but … do we have to specifically stretch nerves to achieve it? Is it clinically important to do so?

It could be. Not everything in biology functions or heals well solely with the stimulation of normal activity! A simple example: deliberately washing wounds is dramatically better at preventing infection than just letting nature take its course. Simple mechanical flushing is powerful.

On the other hand, many medical interventions and “crutches” that supposedly facilitate healing have turned out to be surprisingly useless or even harmful. It is rarely obvious how we can help biology.

Why indeed would one want to ”drag at" an inflamed nerve? In 1880, Dr. Bramwell reckoned it was to break up adhesions. And he might have been right. But it also might be simpler than that. (Hat tip to Tom Jesson for this old citation.)

Science to the rescue? As usual, not really

Rigorous study is the only way we’re ever really going to know if specifically stretching nerves is truly helpful — as opposed to, say, something else specific like stretching blood vessels, or something general like just doing some calisthenics.

So, do we have that? Hardly! A 2022 paper reviewed just eight studies of neural mobilization for back pain (see Peacock), and six had results in the “technically positive” category, but nothing impressive. This is good fuel for wishful thinking for now, and that’s about it.

This is just a little excerpt. Read the full review here: