The best way to make choku-zuki from Bio Mechanical perspective 謎・直突きと肘の関係 (Part 3)

Kanazawa choku zuki 2This lead us why most of the people prefer to play Shotokan -karate or the direct question why the Shotokan -style is the strongest than the other styles of karate schools. In fact the dynamic of Shotokan karate is the real reason. We look back at the beginning of the 19 century Tote was first demonstrated publicly outside Okinawa in may 1922 at the first National Athletics Exhibition held in Tokyo under the sponsorship of ministry of Education. The man who was invited to give that memorable demonstration was (Master Gichin Funakoshi) who at that time was the president of the Okinawa Shobu Kai (society for the promotion of the martial arts). This martial art was called “Tote” (Chinese hand). Then Tote came to be known as Karate-jutsu and then from around 1929 the Genius Master Funakoshi took the revolutionary step of advocating that the name is changed from Karate-jutsu to Karate-do. The karate would thus be transformed into both appearance and content from techniques of Okinawa origin into a new Japanese martial art.

Special scientific introduction

Kinesiology is the science of study human motion

It brings together the fields of anatomy, physiology, biomechanic, physics, geometry relating to human movement.

Bio refer to living.

Mechanics refers to forces acting on objects and with the results of these forces in terms of equilibrium and movement.

Therefore biomechanic is the application of principles of mechanics to living human body.

Mechanic is divided into static &dynamic. Static, means bodies in balance “equilibrium “. Dynamic means bodies in motion. State of equilibrium is when the sum of forces acting on a body equal zero.

Dynamic system can be divided into kinetics &kinematics.

Kinetics, deals with forces which produce arrest or modify motion of the bodies push or pull them.

Newton’s first law,law of inertia or law of equilibrium. It deals with objects in equilibrium, bodies at rest tend to stay at rest, bodies in motion tend to remain in motion

● An object at rest will remain at rest or in uniform motion unless acted upon by an unbalanced force.Newton

Newton’s third law,, law of reaction forces always come in pairs. For every reaction there is an equal &opposite reaction. Or when an object applies a force to second object, the second object simultaneously applies a force of equal magnitude &in the opposite direction as the first object.

All forces acting on a body must be identified, these are the force system. If all forces are in the same line this called ” Linear force system “example, primary forces which act on the human body are gravity this applies externally resistance muscle contraction

Force System

Linear force system means that all forces are in the same line

Parallel force system means two or more parallel forces acting on the same object but at some distance from each other (lever system is this type).

Lever is rigid bar that can rotate about a fixed point when a force is applied “bone”

Axis is a fixed point about which the lever rotates.

Weight is the resistance that must be overcome. Force, usually muscular contraction in the human body.

Weight arm is the distance between the fulcrum & the weight. Force arm is the distance between the fulcrum & the force.




First class lever





The axis is located between the force & the weight,”resistance ” this system is designed best for balance for example Atlanto occipital joint.

Second class lever






The axis is located at one end resistance is in the middle & the force at the opposite end , designed best for power for example wheelbarrow, rising up on toes.

Third class lever





Axis is at one end, force is in the middle & resistance at the opposite end designed for mobility, most common lever system in human for example [normal muscle contraction, hinged door].

Torque,when a force acts on a rigid bar or lever it may cause a rotatry motion around the fixed point ‘axis ‘.

Torque or a moment of force is the measurement of the ability of a force to cause rotation of the lever.

Torque equal to force (pounds) × distance (foot pounds).

The length of a line drawn perpendicular to the action line of the force from the axis.

Torque is an important measurement because a force applied further from the point of rotation or axis, requires less force to produce movement for example resisting exercise & body mechanics.

Mechanical advantage

Deal with the relationship between the length of the force arm & the length of the weight arm.

Mechanical advantage is related to concept of torque, if force equal to weight and force distance is greater than weight distance this lead that force has the advantage.

The lever arm will move in the direction of the force. Increasing force distance or decreasing weight distance increase the mechanical advantage.

A joint is stabilized when the sum of the net forces acting on it equal zero.

Gravity is probably the most important force. When you consider gravity is the point of application is called (Center of Gravity).

Center of gravity is a hypothetical point at which all mass would appear to be concentrated and is the point at which the forces of gravity appear to act.

1- in a symmetric object center of gravity is the geometric center.

2- in an asymmetrical object center of gravity is toward the heavier end. Center of gravity can be thought of as the balance point. Center of gravity in human is just anterior to S2 sacrum in anatomical position .

(We will explain this in future with Shihan Yokota practically & scientifically in future.)

For an object to be stable the center of gravity must fall within the base of support.

In the principle of body mechanics

The larger base of support the greater the stability of an object or person.

The lower the center of gravity goes towards the base of stability the more stable object or person.

The important thing for us to discuss the third class lever

With that type of lever the force being applied between the axis & the resistance which are designed to produce speed & range of motion movements. Most of the levers in the human body are of this type which requires a great deal of force to move even a small resistance, example the biceps brachii muscle is a typical example in the body.

Using the elbow joint (A) as the axis, the biceps applies force at its insertion the radial tuberosity (F) to rotate the forearm up. With its center of gravity (W) serving as the point of resistance application. Also the brachialis is an example of true third class leverage, it pulls on the ulna just below the elbow.

Relationship of the length of lever armsArm 90 degree

* The resistance arm is the distance between the axis and the point of resistance application.

* The distance between the axis and the point of force application is known as the force arm.

* There is an inverse relationship between force and the force arm just as there is between resistance and the resistance arm.

* The longer the force arm the less force required to move the lever if the resistance and resistance arm remain constant.

* In addition if the force and force arm remain constant a greater resistance may be moved by shortening the resistance arm.

* Decreasing the amount of resistance can decrease the amount of force needed to move the lever.

* The system of leverage in the human body is built for speed and range of movement at the expense of force.

* Short force arms and long resistance arms require great muscular strength to produce movement.

* From practical point of view this means that the muscular system should be strong to supply the necessary force for body movement especially in strenuous activity.

When we apply the leverage law to produce speed and power on choku zuki or gyaku zuki

There are 3 position of the elbow beside the body usually seen from the position of readines.


When the angle less than 90°

Part of tensile recruiting to attract the bone of forearm in the joint direction leading to increase friction and therefore reduce the amount of tensile used in performance, this lead to decrease the speed of starting of choku -zuki and the amount of power produced.

When the angle is greater than 90°

Part of the tensile working upon the lever bone pulling away from the joint so the tensile used will be decreased and you will need more effort to bring the forearm to the correct position to start.

When the angle is 90°of elbow joint

This the best angle of tensile where all the forces of the muscles are recruiting to move the bone of forearm around the axis. This lead to the maximum speeding start of the choku -zuki and that’s what the karate -ka do it in Shotokan karate. By maximum speed will generate the tremendous amount of power. The very important notice the pronation and supination movement is good when elbow is flexed to 90°. The flexors muscles of elbow joint are Brachialis, Biceps, Brachio -radialis, Flexors of forearm and the extensors muscles are Triceps and Anconeus muscles.

  • The most important thing is to make the angle of elbow in the position of readiness of the choku -zuki is 90°(right angle) beside your body , this gives you the maximum fast start for your punch (choku zuki) and this will lead to generate the awesome power which can penetrate the target.

  • All the forces of the muscles of the arm arm and forearm are working on the best way to work for starting action.

  • In decisive technique (kime- waza) there is power that is instantaneous and formidable. The basic techniques of karate are influenced to a very great extent by speed.
  • It may be a bit of an exaggeration to say that in training in techniques speed is first in important and second in importance.1
  • The very important notice is the pronation and supination are good when the elbow is flexed to 90°.
  • This means that the rotation of the fist will be in maximum effects before hitting the target.
  • There are many mechanical laws such as the laws of levers that can be exploited in the production of higher degree of muscular power.
  • The angle of tensile which are used in the muscular work is very important in production of power
  • The angle of tensile is the angle between the tensile line in the working muscle and the mechanic pivot for the bone which the working muscle insert into it.
  • This point is the site of effect of forces in lever bones.


We take the facts of the biomechanic science and applied it on our sport to improve our performance with the least amount of effort to produce the maximum results and decrease the possibility of injury .


The article written by Dr. Ashraf Ragab

Ragab portrait

Pharmacist B.Sc.Ph.Ph.Ch.

Faculty of pharmacy Cairo University

Sport injury specialist with excellent grade in 1/7/1998 from Olympic Academy of Athletic leaders

Karate examiner of Egyptian karate Federation






1-Best karate .Mr. Nakayama.

2-illustrative upper limb.ElRakkawy.

3-Biomechanic Thompson c.w&Floyd R.t (1994)

Manual of structural kinesiology.

4-Wolters klwer health 2009 , Lippincott Williams & Wilkins.

5-Modern sport training. Dr.Mofti Ibrahim.

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