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Saturday, May 1, 2021

The Physics of High Blocks

What is the optimal angle for a high block?

Very often high blocks are really strikes.  But getting your arm over your head to intercept a blow is not an insane thing to do, and that's what we're looking at today.

First, let's look at the physics of something you probably don't want to do.

Louvre material, for sure.

At 0° your forearm is parallel to the ground.  In this scenario, you're taking the full force of the blow on your arm that would otherwise hit your head.  This is usually a pretty good trade, but it could be better.

Once your arm is angled, there's the potential to let the blow slide off the arm.  In terms of physics, part of the blow's momentum will go into your arm (ouch) and part of it will be deflected harmlessly away (yay).  

I did math so you don't have to!

This all boils down to two equations:

momentum transferred into the arm = momentum x sin (90° - arm angle)
momentum deflected by the arm = momentum x cos (90° - arm angle)

Or more simply:

Ouch = 100% x sin(90° - arm angle)
Yay = 100% x cos(90° - arm angle)

Traditionalists are welcome to adjust their glasses, pull a pencil out of their pocket protector and tap this into a calculator.  I'm going to just ask my phone because I'm a hip young whippersnapper and not cringey at all, bruh, YOLO!  Also you just lost The Game.

Here's a nice little chart:

The percentages don't add up to 100% on all of them because adding vectors doesn't work quite like adding plain old numbers.  But the math is sound.  If you multiply those percentages by how hard you're getting hit, that will tell you how much momentum is going into the arm and how much momentum is deflecting the weapon.

So, from this chart, it looks like the best angle is 90° because ALL of the momentum is deflected and NONE of it goes into the arm.  Which sounds great until you think about what a 90° block actually looks like:

"I could have blocked, but the stupid author insisted on a stupid
90° angle."

So at 90° against a blow coming straight down, you're not protecting your head at all.  At 80° you're covering a tiny part of your head.  If you do manage to line it up just right, you're deflecting almost all of the impact and taking very little damage to the arm.  But that is extremely risky and ill-advised in the chaos of a situation where you need to deflect a blow to the head.  At the other extreme, a 0° angle covers the most head area, but you deflect nothing.  And it's a good idea to deflect SOME because then the attacker's body can follow along to the side as you deflect, giving you a little control over their movement.  

What's the best angle?  The best angle is the steepest angle that actually catches the blow.  But in high-stakes situations there are no guarantees, so some margin for error is a good thing.  Also, in the spirit of recognizing that there are no guarantees, there are no guarantees that the blow is going to come straight down.  

So ultimately, the optimal angle isn't even the right question.  Better questions are, did you deflect the attack?  Did you take serious damage?  Can you still fight?  With all that in mind, happy training!