Basic Physics for Karate

I have been asked, mostly by young adults who are now in high school, what sciences can help them understand Karate the most. Well outside of all of them, I have to point at physics. I know, I am a biology guy and yet I am saying Physics! But the truth is that no matter how much I can tell you about muscle insertions, biochemical and neural reactions in the body that allow for muscle contractions, Physics…that damn hard subject in class that seems to start off with all that math…is still the king when it comes to interpreting and understanding human movement.

To be more precise I would work in physics and biology to get to a science called biomechanics, or the science of mechanics in respect to movement! In order to properly understand how and why Karate techniques work so well in combat and self defense we need to look at basic physics first.

Early physicist and Mathematician, Sir Issac Newton began studying physics and finding ways to describe movement in a real and mathematically measurable way. He studied all the greats like Kepler and other early theory based physicists. His methods and study lead to three rules of motion that can help us understand why Karate works in a broad sense only.

His first rule or law was “every object remains at rest or in a state of uniform straight line motion unless acted upon by an unbalanced force”. Unbalanced meaning not equal to the force being created by the object or in a direction other than the current trajectory of the object. In other words if a rock is hurtling thru outer space, were there is not friction, and it hits a rock that is staying perfectly still, the result will be that the “perfectly still Rock” will move! So, how does this help Karate? Well, a person’s Jaw sill stay perfectly still and will not move or have any reason to stop moving in its current state…until your fist smashes it and redirects the force or movement of its current state. Not to deep for us but its only his first law people!

His second law is much more interesting for us! “the rate of change of momentum is equal to the force applied or the force acting on the body is directly proportional to the product of its mass and acceleration produced by the force of the body”…..think that’s confusing…read it in Latin! Okay, to make it more real for us…If you hit a guy with a hard punch that is fast his change in momentum will be equal to the force (speed and power/mass) that you use….a light punch will result in a small amount of displacement, a light kick however, same speed…may result in more displacement because the punch may only be the arm…the leg is much bigger. This is why a well placed front kick will always do more damage than a well placed Jab done only with the arm!

His third law suggests the reaction more than the action. “to every action there is an equal and opposite reaction”. Normally that is where people stop reading….the rest is “the action and the reaction act on two different bodies simultaneously”. How does this help us in Karate? One has to remember that while they are punching a person in the face, the actual force of impact is only measured in millimeters; the reaction site is the persons face, neck and spine, along with the body to some degree….as well as the strikers hand, elbow, tissues, shoulder, spine and their body as well. This is why we must condition the body to be a mechanically correct and technically efficient machine! If the shoulder is weak we will end up with a damaged shoulder.

I am going to break down a few terms that may help you analyse your movements and If you train with me in class or just want further info on how to apply this to your Karate, don’t hesitate to ask. The terms I am going to share are commonly MIS-Used by instructors and student and they could be a great way to analyse movement for efficiency and effectiveness, but are not used or are not used correctly!

Acceleration Acceleration is the change in Velocity/speed of an object. This can be cause by increasing the rate of movement of an object or the direction of an object. So, for Karate the speed you move a punch at from rest to maximum speed is acceleration. The first phase of a punch is going to be acceleration, the last phase at impact is Deceleration.

Axis The imaginary line about which a planet or other object rotates. Also the imaginary line from the top of your head to the floor that your body rotates around when turning for a reverse punch, or the line thru the left to right hip that your pelvis moves around when vibrating a front kick, Front to back thru the pelvis when making a side snap kick…ext.

Centrifugal force An apparent outward force on an object following a circular path that. This force is a consequence of the third law of motion, the way a spinning back fist gains power from the center of the body upon the spin.

Centripetal force The force required to pull an object out of its natural straight-line path and into a circular path; centripetal means. When throwing a person the act of pulling them off balance towards the center of your movement is Centripetal. Often this is misused by instructors who think that the act of spinning is going to create a natural inward force, Spinning does not create an inward force, this is a counter natural movement!

Crest The point of maximum positive displacement on a transverse line is called a crest. So the point at which force/power has reached its maximum amount is a crest. If you hit someone the point of impact when the power is at its kinetic most is called a crest. Not very important because it is a split second in time. But the more technically complete your movement and the more Kime you use to reinforce it the higher the crest will be.

De-acceleration the point at which acceleration begins to decline, be it because of friction, a lack of power or a rapid deceleration due to impact with another object. The last phase of a technique as it ends in the air or after impact.

Displacement The change in the position of an object in a particular direction is called displacement. Displacement may also be defined as the shortest distance between the initial and final position of a moving body. This is important when you want to gage what kind of force you are needing and what kind of results you got from a impact on a object. If you want to know the results of a technique on a object this vector measurement is a good indicator of the effectiveness of your technique, however you may have used less acceleration and more force, resulting in less effective damage to an attacker.

Distance The actual length of the path traveled by a body irrespective of the direction is called the distance traveled. The other thing to keep in mind is that some Karate techniques have a limited distance that they travel, a optimum required distance and a required distance for optimum effect. If you start a front kick and the leg has to travel a longer distance than is optimum you start to lose power, a punch can only travel so far before the body must move with it, thus being less effective, and if a target is to close, then the distance needed to create enough impact effective power is limited, thus the punch is weaker.

Lines of force time to fess up, I stole this term from Electricity and electric current and use it in my explanation of Momentum and directionary physics. My use of this term is to describe the path of force and acceleration. This allows us to understand when a line of force is broken, how the energy that is imparted to a target is less because the line of force is not straight. IE if you break at the hip when doing a technique with the arms the connection to the floor is broken and the line of force is then broken…the techniques are then purely upper body and you are losing the efficiency of the technique.

So, now you have just a few basic terms to play within your Karate class or at home….so what. Well, if you understand the way that physics is appropriately applied to techniques you will understand how to make them more efficient. Take out the extra movements for a reverse punch, keep your arms in line when moving and don’t break at the hip…all good starts. If you give me a sturdy stick as a leaver and a hearty fulcrum point I can move the world! Or, if you let me understand efficiency in training and movement I can cause enough force to your rib cage to snap bones like twigs upon impact of my Projectile (foot) along the line of force (from floor to impact site) and using the knee and hip as an axes point for my kinetic energy….or in English, I am gonna kick you hard in the ribs and break em!

A few things that you can use to qualitatively analyze a technique without getting into quantity and actual striking power would be Proper rotation of the hips, Lines of force, Excessive movement and drive into the ground. What does this look like….okay…..some examples of this would be…..

For a reverse punch

· Does the person push into the floor with their back leg

· Does the person rotate the rear hip to the front, the more to the front the better

· Does the person continue to bend the front knee to ensure that the hips don’t move backwards while rotating.

· Does the person limit the bend in the torso to just a slight forwards bent, more a rotation of the shoulder with proper spine bend.

· Has the person allowed for a slight bend in the elbow to absorb shock

· Is their head straight to target

For a front kick

· Does the person use the floor to support and push off of. Heal down!

· Does the person use the pelvis to rotate slightly for a vibration to the target?

· Is the person properly brining the knee up and using it as a rotation point.

· Is the impact site the top ball of the foot

· Is the person leaning into the technique and brining their center to the target.

The point is that, while it may seem a bit scary, we can use physics to explain and learn more about our Karate. Instructors, especially new ones, should be looking at pictures and explaining lines of force, proper form ext to their students as a way of learning to analyse good form and good techniques.

Physics can be a great tool for Karate people to learn more about getting effective and efficient skills out of their training, and it can help point out and correct issues in form and use of techniques.