Compression Locks

Science Concepts: torque, pressure, anatomy

I watch a lot of martial arts videos online.  I’m always on the lookout for new drills or insights into techniques and concepts.  I’ll watch just about anything having to do with fighting: boxing, BJJ, kali, silat, muay thai, dumog, sikaran, sambo, stick and knife videos.  The list goes on.  There’s a topic that I don’t see covered nearly enough (my opinion, of course), and that is compression locks.  I suppose that many grappling schools refrain from teaching them to lower ranks for fear that they might hurt someone in practice.  This is evidenced by the fact that the rules on prohibit compression locks for anyone other than brown and black belts.  Since I lean more towards self-defense than competition, I’ll teach just about any technique to someone of any level that can provide an advantage for them in a fight, including compression locks.

I love compression locks.  Just ask any of my students.  They often have the (mis)fortune of being of the receiving end of my demo techniques.  I’ll slip a compression lock into a series of moves, which will inevitably evoke a drastic reaction out of the recipient.  Then that recipient has to have the move done to them another three or four times so everyone can pick up on the nuances of the technique.  (I do feel bad about that…but how else are they going to learn?!)

Now, in case you’re not hip to the hotness that is compression locks, let me provide a definition.  From Wikipedia, “A compression lock, a muscle lock, muscle slicer or muscle crusher, is a grappling hold which causes severe pain by pressing a muscle into a bone.”  The Wikipedia article then goes into all the gory/awesome details of what kind of damage compression locks can do.

There are several things that I like, in particular, about compression locks.  First, they work better on people with bigger muscles.  So they’re a bit of an equalizer.  Second, they are often available when someone defends against a regular joint lock.  Third, they are easier to apply if you have really bony forearms and shins, which I do.


Some Compression Locks

Ankle Lock

Now, there is one compression lock that is popular.  That is the straight ankle lock.



Technically, the pain first comes from the radial bone crushing the Achilles tendon against the fibula bone.  In my experience though, the person taps out because of the pain of the ankle hyperextending, which is a regular joint lock.  (Unless of course, the person isn’t willing to suffer through the pain of their tendon being crushed.  Then they tap right away.  But in competitions or when your training partner is the dojo jerk that thinks every drill is a life or death war and refuses to tap, they wait until the ankle feels like it’s going to pop out of socket.  While I’m thinking of it, here’s a public service announcement: Don’t be a dojo jerk.  Just because you can power through something doesn’t mean that it’s good to do so.  More often than not, you’re being a bad training partner, and you’re also reducing the longevity with which you will be able to train…because you will force your training partners to go full force, every time.  Injury city.  Population: you)

Bicep Slicer

There are literally so many ways to do a bicep slicer that I couldn’t possibly list them all here.  I willcover several of them to give you some ideas though.

Off of a punch – You could use a split entry or a zone block or whatever, just capture the arm and lay the bony part of your wrist as far into the crease of the elbow as possible and then push your opponent’s wrist towards his shoulder with your other arm and/or shoulder.  Some downward pressure from your body weight may help as well.

Here I’m using my shoulder to push the wrist down and out while
sinking my knees a bit and crunching my abs to get a bit more
pressure and velocity on the technique

Dominant ground position – Sometimes you can trap the arm with your shin on the ground to inflict extra pain with the pain you’re inflicting 🙂

Here I’m crushing Mike’s bicep by driving my hips into his wrist towards
his shoulder while I wind up for a big hit…probably an elbow to the
solar plexus because it’ll help push my hips lower to make the slicer
that much more effective
  • Counter to arm bar defense – One of the quick ways to save your arm from getting locked out on the ground is to grab it with your other hand in some form or fashion.  Well, if someone does that to you then you can hurt their arm by compressing it rather than extending it.
I’m just using my left arm to crank down on his wrist for the picture, but
if you want to get some strength on this technique then get a leg involved.
Every time I am able to get into this position, the person either taps out
immediately or lets go of their arm and I arm bar them

Calf Slicer

There are a number of ways to get to a calf slicer.  The mechanics are essentially the same as the bicep slicer.  This tends to be a ground move, but I’ve pulled it off at least once in sparring while both me and my opponent were standing up.

Here I use my forearm as the fulcrum and push his foot towards his
hip with my shoulder, driving from the ground with my legs for strength.
The same lock but applied with my shin.  Again, I’m driving forward with my hip
and I also have a grip on his shoulder with my right arm to help pull me forward
and stabilize me in the event he decided to try to squirm out of it.

Deltoid Crusher? (I don’t know the official name of this one)

This is a compression lock that I’ve seen in Kali and Silat circles and not so much with the BJJ crowd.  It requires either more finesse or a nice diminishing attack to pull off, but luckily getting an eye shot on the way to setting it up is quite natural.  I like to do this from (what I’ve heard called) a reverse split entry, which is where your outside arm goes to the inside and the inside arm goes to the outside, which is a lot less awkward than it sounds.

This lock is admittedly a fair bit different than the “slicers” but it’s a muscle crusher just the same.  It either puts the guy on his knees or his attempted escape leads right into a puter kepala takedown.

I keep a hold of Mike’s wrist to prevent him from escaping and then
torque my arm so that it pivots around the midpoint of my forearm, driving
my wrist down and my elbow up.  As Mike would say, I’m using the “magic judo
finger” here to make sure that my arm is as uncomfortable as possible for him.

The Science

Rather than break down each of the techniques above, I’ll just focus on one.

In the above picture, I’ve drawn in the important pieces for a compression lock.  The green base that is drawn over the upper leg isn’t going anywhere because of the ground.  The blue arrow is the force I’m applying to the other green line.  My ankle is acting as a fulcrum for this lever.  The part labeled “A” is the part of the leg from the toes up to the point where my ankle is touching.  The part labeled “B” is the part of the leg from where my ankle is touching up to the knee.

When I apply the force with my ankle (or whatever) in there, it generates torque at the location of the fulcrum.  The longer I can make the “A” part by pushing my ankle closer to his knee, the more torque I can get out of the force I’m using.  One of three things is going to happen.

  1. He is able to counter-act my torque by using his quads to extend his leg.  If he’s really strong or I’m really light weight, then this might happen.  It’s unlikely though because he will have to provide A/B times the force that I am just to hold me steady.  That’s why I want the “A” part to be as big as possible.
  2. His shin bones can’t take the torque and snap at the red dot.
  3. His shin bones CAN take it, but the ligaments in his knee can’t and his shin bones are literally pulled away from his femur, dislocating his knee at the orange dot.

The situation you end up in is going to depend highly on the person you’re doing the move to.  I’ve found that people with more developed muscles tap earlier because they just have more muscle to crush.  Those people also feel the pain earlier (in terms of angle of the knee or elbow) because the muscle is taking up more room, giving you more distance to apply the move while in “locked” position.

As a point of application, you want the fulcrum to be as wide and hard as possible.  You want it to be wide so the pain is felt earlier in the motion, giving you that increased distance.  You want the fulcrum to be hard because that increases the pressure (remember Pressure = Force / Area).  You also want the little triangle that your fulcrum and opponent’s bones make to be as isosceles as possible.  For those of you who can’t remember your geometry vocabulary words, that means that the two green parts of the triangle up in the picture are the same length.  This has the effect of getting the fulcrum to push into the opponent’s body at a perpendicular angle, which means that you don’t have to use muscles to keep it in place (yay vectors).


If you’ve never experienced a compression lock, then you may not fully appreciate all of the pain and muscle destroying goodness that these types of moves have to offer.  The concept is simple.  Just use leverage, pressure, and some basic vector math to crush a muscle against a bone.  Compression locks are not only effective on their own, but they also complement “traditional” joint locks extremely well because they work in opposite directions.  Try it out slowly (for the sake of your training partners) and see for yourself.

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