Sean Mackey, M.D., Ph.D.

A-beta fibers are your touch fibers. When you touch or stroke your skin, those get activated. When you stand up and you stand on one leg, they're also responsible for position sense. They have a heavy coat of insulation around them and they are wicked fast. C-fiber is one meter a second. A-delta fiber is 10. A-beta fiber is 100 meters a second. Fast. That's why you can dance.

A-beta fibers are your touch fibers. When you touch or stroke your skin, those get activated. When you stand up and you stand on one leg, they're also responsible for position sense. They have a heavy coat of insulation around them and they are wicked fast. C-fiber is one meter a second. A-delta fiber is 10. A-beta fiber is 100 meters a second. Fast. That's why you can dance.

That's why you can walk because you've got those fast reacting A-beta fibers. Now, let's go back to your thumb, Peter. You just hit your thumb with a hammer. Sharp jolt of pain goes to your brain. Got a little delay. Oh damn, this is really going to hurt. Hot burning flooding sensation comes over your thumb. What is the next thing that you do? Everybody does this a little differently.

That's why you can walk because you've got those fast reacting A-beta fibers. Now, let's go back to your thumb, Peter. You just hit your thumb with a hammer. Sharp jolt of pain goes to your brain. Got a little delay. Oh damn, this is really going to hurt. Hot burning flooding sensation comes over your thumb. What is the next thing that you do? Everybody does this a little differently.

Before or after swearing? There you go. A lot of people swear, so it's after swearing. You swear and then- Shake it. Shake. Okay. You're a shaker. Or a squeeze. Squeeze. Proximal to it. There you go. You squeeze, you shake it. Sometimes you run it underwater. What are you doing when you're squeezing it and shaking it?

Before or after swearing? There you go. A lot of people swear, so it's after swearing. You swear and then- Shake it. Shake. Okay. You're a shaker. Or a squeeze. Squeeze. Proximal to it. There you go. You squeeze, you shake it. Sometimes you run it underwater. What are you doing when you're squeezing it and shaking it?

Yeah, that's beautiful. And you're talking about longer term things which are all perfect. Because cold does those things, and also cold, by the way, reduces action potential velocities and firing in those A-delta C fibers. But what you're doing most of all when you rub it is you're activating A-beta fibers. you're actually not influencing much your A delta or C fibers, those nociceptive fibers.

Yeah, that's beautiful. And you're talking about longer term things which are all perfect. Because cold does those things, and also cold, by the way, reduces action potential velocities and firing in those A-delta C fibers. But what you're doing most of all when you rub it is you're activating A-beta fibers. you're actually not influencing much your A delta or C fibers, those nociceptive fibers.

You're not really impacting it there. That horse left the barn. That horse left the barn. You got horses still running out the barn. You can squeeze all you want for the time being and the horses are still heading out and hitting your spinal cord. But where things get interesting is the A beta fibers, those touch fibers,

You're not really impacting it there. That horse left the barn. That horse left the barn. You got horses still running out the barn. You can squeeze all you want for the time being and the horses are still heading out and hitting your spinal cord. But where things get interesting is the A beta fibers, those touch fibers,

They're coming into a slightly different area of your spinal cord, and they're sending over projections into where those nociceptive fibers are in your spinal cord. And they have an inhibitory role. That's the take-home message. So the A-beta fibers are inhibiting the signals coming in from where you hit your thumb with a hammer and preventing them from going to your brain.

They're coming into a slightly different area of your spinal cord, and they're sending over projections into where those nociceptive fibers are in your spinal cord. And they have an inhibitory role. That's the take-home message. So the A-beta fibers are inhibiting the signals coming in from where you hit your thumb with a hammer and preventing them from going to your brain.

It's a beautiful example of neuromodulation. You're doing your own neuromodulation with that. And we're all hardwired to do that thing. And there's a medical device that takes advantage of that. You're familiar with the TENS unit? TENS is T-E-N-S, Transcutaneous Electrical Neural Stimulation.

It's a beautiful example of neuromodulation. You're doing your own neuromodulation with that. And we're all hardwired to do that thing. And there's a medical device that takes advantage of that. You're familiar with the TENS unit? TENS is T-E-N-S, Transcutaneous Electrical Neural Stimulation.

Now, what it originally did, there's been modifications of it, is what you do with the TENS, I know you know this, is typically little black pads that you put over the area that hurts. You put an electrical stimulation through these pads. They're activating A-beta fibers. And so you do them over here and it's having a neuromodulatory effect back in the spinal cord. Pretty cool when it works.

Now, what it originally did, there's been modifications of it, is what you do with the TENS, I know you know this, is typically little black pads that you put over the area that hurts. You put an electrical stimulation through these pads. They're activating A-beta fibers. And so you do them over here and it's having a neuromodulatory effect back in the spinal cord. Pretty cool when it works.

I would just build on that, that I would say my job, our job as pain docs is to help reduce the pain and help them down a path of functional rehabilitation. So absent that second piece, I typically fail. I'm leading them down a road of functional rehabilitation, which involves physical, psychological, social, emotional health, all things you talked about beautifully in your book.

I would just build on that, that I would say my job, our job as pain docs is to help reduce the pain and help them down a path of functional rehabilitation. So absent that second piece, I typically fail. I'm leading them down a road of functional rehabilitation, which involves physical, psychological, social, emotional health, all things you talked about beautifully in your book.

Somebody with, I think, more, you know, there's no susceptible musculoskeletal pain. I tend to think of somebody for whom TENS is more likely to work, something that has more of a classic nociceptive type of pain problem. Beyond that, Peter, it's a trial and error.

Somebody with, I think, more, you know, there's no susceptible musculoskeletal pain. I tend to think of somebody for whom TENS is more likely to work, something that has more of a classic nociceptive type of pain problem. Beyond that, Peter, it's a trial and error.