Applying ‘Impulsive Force’ to striking.

 An essay by

Lee Taylor

In recent lesson’s we have discussed the fundamentals of foot work and body composition when throwing an attack, with our examples being the jab or a low kick, with an emphasis on being relaxed during the application. During practice it was evident that often too much tension was present throughout the body, namely through the back and shoulders, during the jab or tension in the hips and lower back during a low kick. This was often a result of over thinking the movement. With this in mind I have decided to research a bit further in what it means to throw an effective strike and try to understand the science behind it.

 First of all let’s understand the science.

 When we talk of a punch or a strike, the obvious aspects of physics are Force, Momentum and Impulse. With the latter maybe being the less obvious!

 Force:

 Force is an influence that causes a still body to accelerate.  

 Meaning that Force is defined/calculated by multiplying an objects mass by its acceleration (Change in speed).   

 Mass x Acceleration

 The problem with using the force equation to measure punching power is that if your fist is moving at a constant speed, no matter how fast, your force is zero.  

 An example of this:

A 1 ton car moving at a constant 100 MPH hits a brick wall.  What was the force of that massive impact?  

 The force was zero because the car was not accelerating.  

 Momentum:

 Momentum is how fast and heavy an object is.  

 Momentum is defined by physics as: P=MV.  P is the momentum, M is mass, and Velocity is the speed and direction of the object.  

 What that has to do with striking someone is: the more mass or velocity behind your kick the more momentum your kick has.  The more Momentum, the more force an object needs to stop your kick.  Momentum can also be thought of how much force is backing a moving object. 

 Impulse:

 Impulse is the time needed to stop and object’s momentum over a given distance and time. 

 In other words, the greater your impulse the less force you need to stop a moving object.

 A lot of force in a short time is needed to stop a punch when it hits your unmoving face.  But if you lean and roll with the punch, far less force at any given time is needed to stop the punch.  (Think Mohammed Ali’s Ropa Dope).

By the way, using more force with your face equates to a broken nose and teeth.  Rolling with the punch increase your impulse and decreases the force over time of the fist. Force spread over time is equal to the change in momentum.  Remember, the greater your impulse, the less you get hurt.   Force over time is a lot less damaging that force all at one time.

 ….and so when we combine these three aspects together, it leads me back to the principal I raised that why snapping punches and kicks back cause so much damage.  

 The less time your fist or foot is in contact with a part of the body, it will receive force in less time.  

Blood vessels, bones and other tissue can only withstand a certain amount of force at any given time.  So snapping your strikes deliver enough force in enough time to break the damage threshold of body tissues. 

 If your force is given in a short time you will shatter your object. 

 If your force is given over longer time, the more you will push or crush the object.

 A good example of this would be to compare the punch of a boxer to that of say a Wing Chun or JKD practitioner. Both are equally quick and powerful however the nature of the two strikes are different. 

 When a boxer throws his fist, he usually ends the movement with the follow-through. This gives the punch maximum momentum and it can help knock an opponent down. But the impact itself is diffused: This is due to the strike being thrown with the back and should muscles being contracted, in what western thinking has believe will generate more FORCE.

 With that being said the Wing Chun or JKD practitioner would look to throw the strike from a much more relaxed position and looking to coil the explosive movement throughout the whole of the body starting at the feet, not just through an isolated group of muscles, and then recoiling the strike back to its origin.

You are giving the same level of energy to the object but depending on how long it takes to deliver your energy determines what affect you will have.

 A difficult topic to try and explain but I hope it offers some food for thought.

 LT