Kinetic Energy in Kicking
The physics theory about kinetic energy says that energy = m X v X v / 2. That basically means that you take weight on the leg and multiplying by the speed of the leg kick movement. As you see in the formula is the speed with twice. A simple example shows that if my leg weighs 10kg and I have a speed of movement on the kick 10 meters per second. Then my kinetic energy m X v X v / 2 = 10 X 10 X 10 / 2 = 500 kgm2/s2.
If I were to double the weight of the bone becomes energy is 20 X 10 X 10 / 2 = 1000kgm2/s2 If I were to double the speed of leg energy is 10 X 20 X 20 / 2 = 2000kgm2/s2.
From this we learn that it better to build up speed in the technique than to build mass in the body. Therefore, it is perfectly possible for someone who weighs less to kick harder. It should not be forgotten that the kinetic energy is a combination of weight and speed. It is better to be heavy than to be light if the fighter perform the technique with the same speed. Without the weight, the kick does not work.
Speed through relaxed movement
It is important to be relaxed during movements in order to reach the highest possible velocity before impact. In the instant before your attack connects, you can tighten your muscles to gain stability and prevent damage to your leg.