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  • Writer's picturePSBN David

Falling with Style: the Science Behind Breakfalls

Breakfalls are incredibly important to all kinds of Martial Arts, sports, and activities like parkour. Much as it sounds, you’re breaking up what would otherwise be a pretty nasty fall. This is one of the scariest things for new people to learn, and for good reason! We spend a lot of time and energy as children learning how to generally avoid it.


This is exactly why we start right from the beginning teaching breakfalls. You want to be able to work on a technique and come out the other side unscathed. Eventually they become engrained enough that as soon as you start to fall, your body will naturally go through the motions.


Or at least the most important ones.


But what’s happening exactly with a breakfall so you’re not being injured? They can still look quite dramatic, so people assume that it hurts. However, the whole idea of the breakfall is to prioritize the safety of the important bits (your head and internal organs). Unfortunately, I couldn’t find a good source that really breaks this process down, so you’ll have to make do with watching SBN Ryan throwing me around.


I went through 4 different techniques, each with a slightly different breakfall:


 

Ki Bohn Soo # 1


This is one of the very first techniques you’ll learn in Kuk Sool Won. Granted, this is done significantly faster (and much more in the air) than we’d be doing with new students. However, you’ll see in the data exactly what I describe: the head and body don’t actually move that quickly.



Let’s break this up a bit slower:


The head leads the charge. By the time the body has just started to move, the head is already about halfway to the final spot:


When being thrown, the head moves first
Ki Bohn Soo No 1 - Beginning

You’ll also notice that my center of mass is now well past where my feet are. The technical term for this point is “falling down”.


A bit further along and now my feet have started to catch up with the rotation. Notice that body is now moving at just over 1 meter/second (about 3.3 feet/second for the metrically-impaired) and my head at 0.8 m/s (2.6 feet/s). To give some context to that, Wikipedia puts the average speed of people at a crosswalk at 1.4 m/s (https://en.wikipedia.org/wiki/Walking).


Aerial breakfall for Ki Bohn Soo No 1
Ki Bohn Soo No 1 - Falling

“But David,” I hear you say, “Your feet are going so much faster!”

This is true. However, if we look at the moment where my body has landed, you’ll notice that my left foot has halved its speed already (5.8 m/s down to 3 m/s).


Point of impact for the breakfall
Ki Bohn Soo No 1 - Impact

Now – brace yourself – I’m about to use MATH.


First, some weight references: I weigh about 66kg (145lbs). Using these ratios https://www.timesdaily.com/archives/weighing-in-on-individual-body-parts/article_4729f5a7-c039-5649-910e-ee18a03435e0.html, that gives each part here an approximate weight of (rounding to the nearest whole number):


Head: 5kg

Body: 32kg

Foot: 2kg


And using those, we can use the Acceleration (positive for speeding up, negative for slowing down) mapped out here to use our Mass x Acceleration = Force formula! The X’s denote the point of impact for each piece (note that the head never contacts the ground).


Graph of acceleration experienced in the breakfall for Ki Bohn Soo No 1
Ki Bohn Soo #1 - Acceleration on each body part

We can see the maximum force on the head was right at the beginning where most of that movement happened. At about 20m/s x 5kg, we get 100 Newtons of force. This would feel like 10 kilograms (just over 20 lbs) squishing your head for a split second, which is pretty good for throwing yourself to the ground!


The body peaks out at about 65 kg (144 lbs) worth of force (remember, spread evenly across the entire area) for a fraction of a second. Your average 17 year old guy weighs about that much, so you can imagine a teen sitting on your chest for a second (https://www.disabled-world.com/calculators-charts/height-weight-teens.php). You’d be uncomfortable, but moreso from the strange teenager who just sat on you.


The feet are the fastest, but also the lightest part. Each experiences about 25kg (50lbs) worth of force on them.


 

Ki Bohn Soo # 15


This one is one of the first couple Hip Throw style techniques you learn. Before, I was a lot more in control of how I was falling. With nothing in my way, I could move pretty normally. This time around, SBN Ryan has full control. I pretty much just have to tuck my head in and keep control over my limbs. You can actually see the exact point where SBN Ryan’s better nature kicks in and he slows the throw just before impact!



You already know the gist of how this goes now, so let’s skip a few steps and check out the Acceleration chart again:


Graph of acceleration experienced in the breakfall for Ki Bohn Soo No 15
Ki Bohn Soo #15 - Acceleration on each body part

And right into the breakdown!


Head: This time, it maxes out at a measly 4 kg (9 lbs) worth of force!

Body: On hip throws, the body travels a bit more of a straight up-straight down motion, so it’s a bit harder than the last one. Now it maxes out at about 75 kg (165 lbs)

Feet: The data is throw off a bit here, given that I couldn’t map the arc they would have taken backwards (darn 2 dimensional videos), but we’re seeing about 14 kg (30 lbs) this time.

Add a bit extra onto the Head and Feet to better account for the 3rd dimension that was missed out, but you get the idea!


 

Joo Muhk Maka Ki Bohn Soo # 8


A more advanced version of the initial Ki Bohn Soo set that you learn, Joo Muhk Maka Ki Bohn Soo is taught just before Dahn Bo Nim (Black Belt Candidate), about 2 years in. Now that you know how to move around your opponent a bit better and faster, the techniques ramp up in speed and complexity.

Theoretically, this is the point where you’d be starting to do the kinds of breakfalls I was doing with Ki Bohn Soo # 1 above.



And the chart!


Graph of acceleration experienced in the breakfall for Joo Muhk Maka Ki Bohn Soo No 8
Joo Muhk Maka Ki Bohn Soo #8 - Acceleration on each body part

And it’s the same-old for the data! Head moves fairly quickly into position, then stabilizes as much as possible; body doesn’t shift much at all; the legs launch up quickly to act as a counterbalance to the body and head which relieves some of the forces off of them.


Head gets a max force of 12 kg (28 lbs).

Body gets an easy 49 kg (108 lbs).

Feet get 19 kg (43 lbs).



 

Too Ki # 13


The last one we’ll look at is Too Ki # 13, one of my favourites! This set is taught closer to the end of your Dahn Bo Nihm, when you’re closing in on your First Degree Black Belt. This particular technique is interesting in a similar way to the hip throw: your opponent is largely controlling the fall. This time, however, they’re planting their foot right at your center of mass and launching you with that (which makes for a really run fall).



And one last chart to look at! You’re almost done!


Graph of acceleration experienced in the breakfall for Too Ki No 15
Too Ki #15 - Acceleration on each body part

Let’s break it down one more time:


For all the razzle-dazzle, the head gets 8 kg (17 lbs) of force.

The body, however, takes a bit more this time (as you may have guessed)! At the point of impact, the body takes 82 kg (180 lbs) of force.

And the feet max out at 22 kg (50 lbs) again.


So what’s going on with this breakfall? It’s not actually too bad, despite what you might think from the video and data! You may notice that the point of impact on the body doesn’t quite look like the others: I’m slightly curled for the impact, rather than taking it all at once. This is the Rolling Breakfall that everyone loves so much (and is very popular in parkour).


That curled position and momentum helps me to turn that force from pointing straight down into the ground – where it would promptly and painfully stop me – and redirect it down my body, piece by piece. Part of the force is going down into the ground, but part of it is being used to slide me down the mat.


Let’s imagine the position and momentum helps move that force from a 90 degree angle to a slightly more forgiving angle. Now we can think of our 82 kg instead as the hypotenuse of a triangle.


Changing the force of impact through angles
Angles of force

And use that grade school SOH-CAH-TOA to figure out how much force is going into the painful Down part of the equation! In this case, H = our 82 kg, and we can just plug in various angles to COS(x) = [Adjacent Down Force] * 82 to see the effects of different angles.


Graph of the force of impact experienced at different angles
Graphing out the force of the fall

The more angle we can get, the less “Down” we get! Though good luck figuring out how to get closer to that 90 degree mark.


 

By now, you can see the gist of what’s going on here. Even if they’re higher-level and purposefully throwing and falling harder (for science!), in each breakfall, the head and body are nowhere near the forces the limbs are experiencing.


The center of mass is going to be your main pivot point, so it makes sense as it’s essentially going from point A to B without getting extra momentum from pivoting around. That said, it’s still the heaviest part of your body, so it’s got some inertia going there. Much like if that weird skinny teen is sitting on your chest, you’ll naturally tighten up your core and maybe give an “oof!” right as they sit on you. That’s exactly what we teach everyone to do as well! Everyone can see the teen coming, but Gravity is a cruel, invisible mistress.


The interesting – and key – piece to this is what’s going on with the head: it’s basically the same acceleration your body is experiencing, except it’s not hitting the ground and it doesn’t weigh as much, so the forces on it are miniscule. Try to get it somewhere safe, then use your legs to add the force needed to keep it there


Your limbs may take a bit of a whack, but they can take a lot more punishment than your brain and other organs!


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