• By: Pedro Candeias
  • Date: 06/03/2017


I was at my home re-reading a book dated 2002, written by Martina Sprague. Its title is “Fighting Science: The Laws of Physics for Martial Arts”.


It’s a great 269 pages’ book where the author writes about themes like Physics and Strategy, Center of Gravity, Momentum, Direction, Rotational Speed and Friction, Impulse, Conservation of Energy and Kinetic Energy…


Martina Sprague relates Physics and Martial Arts and I was reading some of the most relevant passages of this book…


… And I wanted to share with you some Questions & Answers that are inside the book. So I wrote this blog post for Karate Science Academy.


I hope it’s useful and can help you to understand better how the human body works when you teaching or training Karate!


1. How can you increase stability?


You can always increase stability by widening your base and lowering your center of gravity.


In a stand-up fight, bend your knees. In a ground fight, spread out.



2. How can you maintain balance when you throw a Geri-Waza, even though your base is very narrow and your center of gravity quite high?


You must have your upper body angled to the rear, your center of gravity directly above your foundation (supporting foot).


In this position, you are in a balanced state. Any time you kick, you must center your upper body above your foundation.



3. Why is a Zuki-Waza or Geri-Waza thrown with your lead hand (foot) naturally less powerful than the same strike thrown with your rear hand (foot)? Are there any advantages to throwing strikes with your lead hand (foot)?


Lead strikes have less distance available to build momentum for power.


The advantage of the lead strike is that it is often faster than the rear, and less telegraphed.



4. How do you solve the less power of the lead strike?


The power of the lead strike can be increased by taking a step forward. This increases the momentum by placing the weight of your body behind the strike.



5. Three ways in which you can place the weight of your body behind your strikes so they can become more powerful.


  1. Take a step forward
  2. Pivot your foot, hip, and upper body in the direction of the strike
  3. Fight from a sideways stance instead of a square stance (like Kiba Dachi)


6. Once you have started the motion of a strike, it is important to keep it going to a sequence of strikes. Why?


Any time you change the state of motion (from rest to moving, from moving to rest, or slowing down or speeding up), you must overcome inertia.


This takes energy and is destructive to power.



7. If you are less massive than your opponent, can you still be as powerful?


You can increase power by throwing your strikes at a greater speed.



8. How can you use your opponent’s momentum against him?


Time your strikes so that your opponent steps into them. Or grab your opponent and pull him forward and into the strike.



9. Name three ways in which you can speed up your strikes.


  1. Use striking that is economical. Avoid any wasted motion
  2. Once you have started a combination, it takes less energy to keep it going than to stop and then restart a second combination
  3. Learn to relax



10. Why is it more beneficial to throw one consecutive combination than many single strikes?


Many single strikes require a constant starting and stopping and restarting of motion (overcoming inertia).


A continuous combination allows you to build speed (which is important to power), with the highest speed occurring at the end of the combination.



11. Name three ways in body mechanics that have the effect of splitting the force into separate directions (bad technique).


  1. Leaning back excessively when kicking
  2. Looping a punch instead of throwing it straight
  3. Moving back when impacting a target



12. The shortest distance between two points is a straight line. How can you utilize the benefits of circular motion without increasing distance?


You can’t!


A circle will always cover a longer distance than a straight line.


Keep in mind that fighting is a give/take situation, where sometimes you must give something up in order to gain a bigger advantage.


Circular motion enables you to increase your speed eliminating the start/stop movement after a Kizami-Zuki, for example.


An elongated oval Zuki-Waza will enable you to increase your speed significantly without increasing distance that much. Don’t open your arm too much before a Furi-Zuki or Mawashi-Zuki.



13. Newton’s Laws Of Motion often seem to contradict our efforts in gaining power. For example, you can’t strike somebody without being struck back equally hard by the target you strike. How do you solve this?


When striking an opponent, you must use a part of your body that is structurally stronger than the target you are striking.



14. Why do we bend our legs more when running than when walking?


Bending your legs helps your body to contract. This reduces the rotational inertia and allows you to speed up the run.


You really should take this into account when you are performing fast Kumite or Kata whole-body displacements.



15. What is meant by striking “through” the target, and how is it accomplished?


Striking through the target means allowing the power of the strike to extend beyond the physical target.


This is accomplished by relaxing to allow full extension of the strike, and by avoiding to subconsciously stopping the strike too soon.



16. What is “snap” striking? In what is it beneficial? What is the danger of snapping back too soon?


A strike that is “snappy” utilizes the minimum time of contact with the target.


The benefit of a “snappy” strike is that the force is increased through a decrease in time.


The opposite of “snapping” is pushing.


When you push, you allow your hand or foot to stay in contact with the target for a longer time, and power is reduced because the time is increased.


We should train to throw our strikes with “snap”, but there is a danger associated with “snapping” too soon.


A strike that is too “snappy” generally utilizes muscular control to reverse its direction, and therefore interferes with proper target penetration.



17. How can a Karateka that falls keep from getting hurt?


In Karate you train and execute throws. It’s important to learn how to fall properly without risking injury.


When the shock is absorbed gradually over a longer period of time, the force is reduced and injury is less likely.


This is accomplished by sequentially touching as many parts of your body to the floor as possible.


A common example is the forward roll, where the impact is absorbed through your hand, forearm, and shoulder.



18. How can distance work either to your advantage or disadvantage?


The longer the distance, the more time you have to build momentum.


This is why your rear techniques often seem stronger than your lead techniques.


But increasing the distance also makes your strike more telegraphed.


Besides that, increasing the distance also increases the workload. When more work is done, more energy is needed, and you will get tired faster.



19. Two ways in which you can conserve energy.


Energy can be conserved by shortening the movement required to execute a technique.


You can get your opponent to expend more energy than you by dominating the center of the fight and making him or her move around you.


A Karateka who is very tired will make much more mistakes in offensive movements.



20. For power, when is the best time to throw an Ushiro-Geri (with spinning) and why?


The best time to throw the Ushiro-Geri is when your opponent moves towards the power of your Kick.


Because the Ushiro-Geri relies on circular movement, and because a fight often moves circular, you should be able to throw the kick whenever your opponent moves in a direction that allows you to spin less than 180º.


This will help you to conserve energy and time through less movement.


21. How can speed outweigh the benefits of a greater body mass?


It takes a lot of energy to set a massive object in motion. When you expend energy, you get tired.


A lightweight Karateka can, therefore, be quicker than a heavyweight, while sacrificing less energy.


Twice the speed increases the kinetic energy by the square.



22. Why is kinetic energy capable of doing so much damage?


A strike that is thrown twice as fast as your opponent’s strike, will have twice the impulse.


But it will have four times the kinetic energy and will penetrate four times as far, and do four times the damage.


In the kinetic energy equation, the speed is squared.


Mass only provides the ability to knock something over, but kinetic energy causes damage.



23. Why is it beneficial to use a striking body weapon that employs a surface area that is small as possible?


Penetrating force is produced best when the force is focused on an area as small as possible because the force per square centimeter will be greater.



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