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Theory of Power

The power of a Taekwon-Do technique such as a punch, strike, kick or block is defined by the rate of energy transferred when it hits the target. That energy is in the form of kinetic energy (energy of a moving object).

Power = E (energy transferred) / t (time taken)

To maximise the power the Taekwon-Do student must:

  • 1. Maximise the kinetic energy of the technique by increasing its speed and mass.
  • 2. Minimise the time taken to transfer that energy to the target by prioritising speed over mass.
  • 3. Maximise the amount of energy transferring to the target by using a rigid tool and adopting a stable stance.

MAXIMISING THE KINETIC ENERGY

The Kinetic energy of a moving object is equal to:

KE=1/2mv2 where m is the mass of the object and v is the velocity (speed) of the object.

So to increase the kinetic energy you need to increase the speed and mass of the technique.

According to this formula:

Doubling the mass will double the Kinetic energy, but doubling the velocity will quadruple the kinetic energy. Hence the importance of speed.

Although speed is more important than mass, it is still worth maximising the mass as long as it doesn’t adversely affect the speed of the technique. This is done by utilising as much body mass in the technique by using sine wave, hip twist, and body shifting.

Also by coordinating the body’s muscles to be tensed at the moment of impact you increase the mass of the attacking technique. If the muscles are tensed too soon it will restrict the movement of the attacking limb which will reduce the speed of the technique. But if the muscles are not tensed on impact then the attacking limb will not be rigid and the mass associated with it will not be effective in the technique. This is why the muscle tension must be ‘focused’ to occur exactly at the moment of impact.

MINIMISING THE TIME TAKEN TO TRANSFER ENERGY TO THE TARGET

The quicker the energy is transferred to the target the greater is the impact force. The damage inflicted by a blow such as a punch, strike or kick depends on the maximum force experienced from the impact of that blow. When a punch, strike or kick makes contact with a target, a force is applied to the target. The effect a force has on a body is to move it and to compress it. For example, when a fist hits a punch bag, a small force is experienced as the fist first makes contact with the bag. As the fist continues to move forward the force increases as the compression of the punch bag also increases. The force on the punch bag will cause it to start moving away from the fist. Since the fist is also experiencing a force it will begin to slow down. Gradually the bag moves away from the fist and the force exerted will eventually reduce to zero. The graph in fig.2 shows how the force varies with time for such a collision

. Figure 1 Figure 2

If we compare two situations:

a) A collision from an object with mass m=400kg and velocity v=1m/s (Fig. 3a)

b) A collision from an object with mass m=1kg and velocity v=20m/s (Fig. 3b)

Figure 3a Figure 3b

Both objects have the same kinetic energy KE=1/2 mv2 but object in situation (b) will provide a larger maximum force, as the graph shows, because the energy was transferred much quicker and consequently the force exerted in (b) had to be greater throughout that short period of time in order to transfer the same amount of energy as (a). The example illustrates why the Taekwon-Do practitioner should make speed a priority over mass.

MAXIMISING THE AMOUNT OF ENERGY TRANSFERRED TO THE TARGET

According to Newton’s third law of motion; the force which body A exerts on body B is exactly equal and opposite to the force which body B exerts on body A. So, not only will the target experience a force from the attacking tool but the attacking tool will also experience a force from the target. This reaction force will work against the attacker so it is often important to adopt a very stable stance to resist that reaction force. A weak stance will result in energy being misdirected. An attacking tool must be rigid to maximise the energy transfer to the target. If a soft attacking tool is used, the energy of the technique will be used to compress the attacking tool rather than the target so less energy gets transferred. This is why most attacking tools are bony parts like the backheel, forefist and elbow. The muscles of the attacking hand or foot must be tensed at the moment of impact to keep it rigid.

CONCENTRATION OF FORCE

The above describes how power can be maximised so as to maximise the force on impact. By applying the impact force onto a small target area, it will concentrate the force and therefore, increase its effect. This is why most attacking tools have a small area such as fingertip, knifehand, and footsword. Blocking techniques are not always required to cause as much trauma as attacking techniques. This is why blocking tools with larger areas such as palm and side instep are sometimes used.