#565 Extensor substitution in runners what is it? - DOC

#565 Extensor substitution in runners what is it?

Today on the Doc On The Run podcast, we’re talking about extensor substitution in runners.



I was just seeing somebody who, I watched her walk. She had a bunch of issues had been bothering her, and she asked me what I actually saw. I was explaining to her that one of the things I saw was that she had this thing called extensor substitution, and she was very curious about that. She wanted to know how it contributed to the issues she’d been having when she was running. We’re going to talk a little bit about that, and it may help you understand why you might be getting some particular issues that have been really hard to fix in the past.

The first thing is extensor means to pull up, right? So, when we look at your foot, oh, and by the way, I know my handwriting’s bad. You can comment all you want. I’m not going to be able to change it. I’ve been trying for like 50 years to change that. It’s not going to happen. Also, my drawings are terrible. I’m not an artist. I’m a podiatrist. I’m a foot doctor. So, if you don’t like my drawings, well, I’m doing the best I can, so you can comment on that all you want as well.

But when we look at your foot, basically what you have is, well, you’ve got a whole bunch of stuff in here, but you’ve got the heel bone. You have the talus sitting on top of the heel bone. Your shin bone or tibia sits on top of that. You have the navicular, and the cuneiformis, and the metatarsal bones. Then you have the cuboid and the other metatarsals, and a whole bunch of other stuff. But that’s what you more or less have.

Now, extension means to pull up. Okay? So, that means to dorsiflex, dorsal, like dorsal fin. If you flex it or pull it up, that’s in that direction. That’s dorsiflexion, and dorsiflexion is what is happening at the toes when you get extensor substitution. So, you have, the tibialis anterior tendon is probably the strongest of the tendons on the front of your leg, the strongest of the muscles that actually pull your foot upward. But you also have tendons that go all the way down and attach to the bones at the end of the toes. You have the extensor hallucis longus, that pulls the big toe up. You have the extensor digitorum longus, that goes out to little toes. So, when we look at your foot on the top, you have the extensor hallucis longus or EHL for short. So, extend means pull up. Hallucis is just the fancy name for the big toe.

Then on each of the little toes, you also have that, but these kind of come together like that as one unit, and then go up in your legs. So, those go to the little digits. So, we call that one the extensor digitorum longus or EDL for short. Well what’s happening in extensor substitution is that you’re using this extensor tendon, the ones that pull the toes up to try to help fight a tight Achilles tendon because if you’re Achilles tendon that comes down in the back, which is the largest of all the tendons in your body. If your Achilles tendon is tight, then it takes a lot of force to pull your foot upward when you’re swinging through and you’re walking to not trip over your toes.

What happens is that the extensors that goes to the little toes is actually pulling really hard to crank and pull up, and actually fight the tight Achilles tendons as it comes through. We see this most pronounced in people that have some neuromuscular disorders, but it’s not that common, so don’t start thinking you have a neuromuscular disorder just because you have this.

This is very common with runners but what happens is you’re pulling really hard to swing through and pull your toes up. When I’m watching someone walk, what I see that someone has a tight Achilles tendon and they’re using extensor substitution to fight that tight Achilles tendon, they swing through and their heel hits the ground, and their toes kind of hang up in the air for a minute, like just sort of a delay before they actually come down to the ground. That’s what I actually notice, is this thing that we call extensor substitution.

If you have it really bad, you can actually get hammer toes, because the toes are pulling so hard that you start getting all contracted from trying to pull and fight the tight Achilles tendon. But what most runners actually get, believe it or not, from this is a consequence, is black toenails. So, you’re swinging through, and your toenails are actually kind of scraping the upper material on the inside of the shoe, and then when they come down, it’s very, very, very slightly traumatizing the nails with each one of those swing through phases of gait. If you’re running uphill, it’s even worse, because you’re having to fight the slope that’s in front of you a little bit harder. So, if you’re getting black toenails that could be stemming from this tight Achilles tendon and your compensation where you’re actually using the extensor tendons to pull hard to fight the Achilles tendon.

Of course, if that’s the case, the simplest fix would be to do some Achilles tendon stretches but what you should do before that is actually set your phone up in your home, just in the living room or somewhere where you have a long distance you can walk in some hallway. Set it down and record it at ground level and look and see how much the toes are hanging up in the air before they come down, and how long that little drag is, that little lag before they actually come down. Then start doing Achilles tendon stretches. Then after you’ve been doing them consistently for a while, videotape yourself with your phone in exactly the same way, and take those same recordings and look at them side by side, and see if the toes are coming down sooner.

If they are, then you’ve reduced the amount of extensor substitution, and it might help you prevent from getting all of the host of problems that actually can come as actual overtraining injuries, due to a tight Achilles tendons. But it can also help you avoid some of those more common, more mundane things like black toenails or bruised toenails that you might get during a marathon or one of your races.

So, if you found this helpful, please like it, share it, subscribe to the channel. If you haven’t seen it yet, you can join me in the 12 steps presentation, where I go into a deep dive on all the things that I would do, step by step if I was in your living room or if you booked a one-hour webcam call, so that you can understand whether or not you can actually run with your injury, and what to do to get back to training as quickly as possible. So, go check it out. It’s at doconrun.com/12steps, and I’ll see you in the training.