Biomechanics of Power – Jari Peuhkurinen

”The degree of clarity with which you define something determines its usefulness to you” -Blauer Maxim

This article is part of a larger project of mine where I’m going to make laws of physics more understandable for martial arts and self-defense. My interest does not lie in the calculations or measurements of conventional physics, but in the practical part of physics; how can understanding basic physics make your action, training and teaching better?

My laboratory for these biomechanical basics is training and teaching concept called Improvement in Action. It´s not a martial art nor is it a system, but a structure of concepts and principles how to improve your training and teaching of self-defense.

When I started this project a few years back, I was looking for the right field of study what to follow, so that I can make sense of the laws that affect us all regardless of the art or a system of training that you follow. Finding the right field of science was not easy. Physics and laws of mechanics provide the basis for these concepts, but they do not tell us how to apply those in training. Biomechanics is a field of study what includes the human (bio) element into the picture, but biomechanics are a lot about measuring the performance. The only measurement in self-defense that we truly need is the effect of our action in the opponent, how can we measure that so that every time I perform a technique, the result is the same? Effect of action is not something we can measure in self-defense, we can only presume what the effects could be and train so that the technique we perform gives us the best possible probabilities of maximum effect.

Also biomechanics do not include the psychological part of the action in to the equation. As we all know, psychological part plays a huge part in our performance under stress and also in training. However, there is another field that includes the psychological part also, it’s called kinesiology. Kinesiology addresses biomechanical, and psychological mechanisms of movement. There is very little or no information on kinesiology and martial arts available. So you can see there is a lot of fields that need to be studied to make the information of basics physic laws applicable to self-defense training.

In this article I will address the proper terms that should be used when we talk about power – effect in the training and teaching.

Basic biomechanical terms

Power (P)is the rate of doing work. It is the amount of energy consumed per unit time. Power does not have direction and it is a vector quantity. and it is measured in watts (w). So power, when used normally in training context does not have the right properties to describe the energy in the movement. Of course we are interested in energy consumption, but since power dos not have a direction, it is not the proper term to use when talking about the energy that we deliver to our opponent during altercation via technique. Still just as a term, power is most commonly used, so there is nothing wrong with as long as you understand and can explain the real meaning of power.

Force (F) causes an object with mass to change its velocity. The original form of Newton’s second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time. Equation for force is F=ma (mass x acceleration) and it is measured in Newtons. This sounds more what could be used in training. So basically if we want to develop more force we can train on two things; increasing the mass or increasing the acceleration of that mass. In my opinion concentrating on acceleration in technique is too precise, if we compare it to developing over all speed in our technique. But we do use concept of force when we create force against the ground to cause motion. Motion enables production of momentum.

Momentum (p) is the product of the mass and velocity of an object, quantified in kilogram-meters per second.So momentum is measured in kilograms-meters per second. Mass and velocity of that mass; that´s something we can use in training. In my opinion, momentum is the proper term that should be used when talking about “power” in techniques. Momentum has direction and it has the element we can develop; velocity. We produce momentum with the movement of our body mass and the velocity of that mass.

Speed (v) is a scalar quantity that refers to “how fast an object is moving.” Speed can be thought of as the rate at which an object covers distance. A fast-moving object has a high speed and covers a relatively large distance in a short amount of time. Contrast this to a slow-moving object that has a low speed; it covers a relatively small amount of distance in the same amount of time.

Velocity (v) is a vector quantity that refers to “the rate at which an object changes its position.” Imagine a person moving rapidly – one step forward and one step back – always returning to the original starting position. While this might result in a frenzy of activity, it would result in a zero velocity. Because the person always returns to the original position, the motion would never result in a change in position. Since velocity is defined as the rate at which the position changes, this motion results in zero velocity. If a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. Every step must go into moving that person further from where he or she started. For certain, the person should never change directions and begin to return to the starting position.

So simply but, the speed of an object is the magnitude of its velocity, the rate of change of its position. 

While velocity is the magnitude of speed in the movement, Impulse is force over the time interval for which it acts on the target. You need to separate these two; velocity of the movement and the time which the force of that movement acts on the opponent.
This is very simple and useful concept to understand. If you have a force of 100 units and that force acts on the target period of 10 seconds. The target receives 10 units of force per second. However, if that 100 units of force acts for only 2 seconds (which is extremely long time for example for a strike) it delivers 50 units per second to the target. What you would prefer is the force of 100 units to act 10 seconds on the target, deliver the force of 100 every second. So basically you want the impulse to contain as much force as possible, for the longest time possible.

There a several ways we can use this concept:

  • We can shorten the time of our movements impulse as in striking. This means recoiling the movement. According to Newton´s III law every force has an equal counter force in opposite direction. So in reality when we strike our opponent, his counter force acts on us in opposite direction and collision transfers our momentum to the opponent. The sum of the momentums stays the same after a collision.
  • We make the acting time longer and utilize movement as a pushing movement. Still we want to have as much force as possible as long time as possible in the impulse. We don’t recoil the movement but keep applying the pressure forward.
  • Proper timing enables to increase the impulse by hitting the target while it has opposite direction to our movement. This two-way movement can be used with proper timing or by making it happen by pulling opponent or keeping target in place.
  • In defense we can utilize impulse by moving with the force so it affects us longer time and this way reducing the force acting on us. Basically the movement acts as shock-absorber so impulse time grows and movement loses its momentum.

Energy/Power Potential

Power potentialis a term that I use to clarify importance of proper body biomechanics in training. Power potential is always present, no matter what the position of our body is, or the situation we are in. It is simply the capacity what we have (not yet produced), in that moment to produce momentum or muscle force and direct it to our opponent. Think of it as stored energy we have in our body, cause of our body´s positioning, ready to be delivered. We should train to maintain proper structure of our body in relation to our opponent’s body, so that in every situation we have the maximum power potential in our use.

Do not confuse this with the physics term potential energy, which is energy that accumulates in our body when we have the possibility to drop our body weight.

We don’t always have the distance required to produce a lot of momentum. As you remember, momentum is a product of mass and its velocity. What happens when we do not have the distance to produce a lot of velocity, but we have the possibility to produce movement? I have separated three different situations:

  1. There is no distance between your tool and the target, you are already in contact and the starting velocity is zero. You cannot produce momentum, but you can produce muscleforce. So this is the situation where you use what you have in your muscles. For an example, a pushing movement with your hands to create distance between your bodies.
  2. There is short distance between the tool and the target. For example, in clinching position, you don’t have the room for maximum momentum, so it requires force; acceleration of the mass. Think about Bruce Lee´s 10-inch punch.
  3. You have the distance to produce momentum and you always try to maximize your body movement.

All these three positions need to be practiced. Be well versed in different distances so you can maintain the maximum power potential in all situations.

Balance is crucial if we want to produce and direct momentum. There can be no effective movement with direction if there is no balance. There can be no controlled movement without balance. So if there is not balanced structure, there is no power potential.

Definition for power potential could be something like this: balanced position, from where we have potential to use our muscle force to produce controlled, explosive linear or angular movement and direct it as needed.

Delivery Potential

(Power) Delivery Potential is another term of mine and it describes the variety in quantity of power potential. We always aim to have to have the maximum potential in our use in any particular position and situation, but we also need to understand that there is always loss of force during the movement. We should train to be better at delivering the whole potential and lose less in the delivery. So if we have power potential of 100 units, the maximum what we can have, there will always be less than that 100 units delivered to the opponent. There are several components that effect on the delivery:

Distance is an element in the equation of our technique and its effect. To put it simply. If you are too far away from the target you need to reach. That affects your structure and balance and it has direct effect on your delivery. If the distance is too short, you don´t have distance to build maximum momentum. Proper delivery movement has to choose based on distance.

Friction is the force resisting the relative motion of solid surfaces. If there is no friction, the power potential will have little or no effect on the target since most of the power potential will be lost from the ground to opposite direction. This is the reason why hockey players grab the opponent when they hit during a fight. This clarifies the importance of proper structure also. Friction force will work for us, when we deliver momentum.

Structure is composed of bones, joints, articular cartilage, ligaments, tendons, muscles and that kind of tissue that keeps internal organs at their place. This is our engine and vehicle that produces and delivers the energy to our opponent during altercation. Structure needs to be without a weak links, for us to optimize its energy production and delivery. Most common examples of poor structure you can see when people hit something and their joints give in and bend during impulse. That is force leaking from the delivery. Remember that according to Newton’s 3rd law every force has an equal and opposite force acting on the objects. That bent wrist during impulse is the Newton’s law in action. Contact with the opponent produces the opposite force acting on our structure.  

Pressure (p) is multi versed term in martial arts and can be used to describe for example the psychological pressure you need to create for your opponent. In here it is a physics term that measures the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Pressure is measured in Pascals. Again to put it simply, we want to deliver and focus our power potential into small area to gain more pressure to the target and create more penetration. Think if could focus the power of our low roundhouse kick to a surface in size of a pin? It would have more penetrating power than a boot tip. The idea of pressure is the same as in impulse. Think about a bullet shot towards you, if you could divide the pressure bullet creates to your whole body area, you would hardly feel it, but because the momentum of that bullet is concentrated to a small area, it has a huge penetrating capacity.

But again there are situations where we want the momentum to effect on larger surface, for example to create more stopping movement.  

Angle in which the momentum is deliver to the target is also of consequence. As mentioned in the pressure is force applied perpendicular to the surface. So we look for 90-degree angle of delivering the momentum. Anything other than that and part of the force is redirected from the target and has no effect.

Effect Potential

Effect Potential is the last part of the movement. Maximum effect potential is ideal result that we look for in any movement we make. It is the proper delivery and directing of power potential that enables the maximum effect. From physical point of view, following two components create the maximum effect in our opponent, if the power potential and delivery are in order:

Tool and Target are important factors of effect. You need to deliver momentum with proper tool and choose the right target for that tool. To put it plainly, do not hit opponent’s kneecap with your fist. Even when you have the momentum and delivery potential, the effect will most likely be not in its maximum. However, if you change the tool, for example to tip of a boot, the effect will probably be closer to maximum what we could hope for.

These two components of effect potential could have been included in the earlier sections too, since all of the other components that result in the overall effect our movement has, is dependent on the opponent’s psychology and physiology.  Basically there are only six desired effects we can hope to achieve with our action:

  1. Pain in order to make opponent give up and comply
  2. Make him out of balance to better our position
  3. Cause unconsciousness (striking)
  4. Disrupt the flow of blood to the brain (strangle)
  5. Disrupt the flow of air to the lungs. (choking)
  6. Stop the heart from beating.

If you really think the whole concept on potential (power-delivery-effect) you can understand why the laws of physics, mechanics, biomechanics and kinesiology are not completely straight forward when talking about self-defense and martial arts and they need to be applied. Of course if we only want to measure how much force or momentum we have in our straight punch, we can use the biomechanical basics to better our movement that way, but for actual self-defense situation it holds almost no meaning, since the effect is only thing that matter, and that cannot be measured effectively.

What we can learn from these concepts is how to make our action and our training better. What to look for in the training.

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