Analysis of the
Isshinryu Vertical Punch

From the Book
Karate - The Isshinryu Way
My Philosophy of the Martial Arts and Life
By: Dan W. Jones

In this portion of his book Mr. Jones is discussing the Isshinryu punch with
biology professor, Sensei John Moore. Mr. Moore provides a detailed analysis of the punch.

“The purpose of a punch is to deliver as much kinetic energy as possible to the desired target, i.e., your opponent.  Compared to other martial arts, Isshinryu uses a fist that is somewhat different in terms of both the position of the digits, and the manner in which the punch is oriented and thrown, i.e., the “vertical” punch with the thumb “up” in the 11 – 12 o’clock position.  The Isshinryu fist is formed by flexing/curling the fingers such that the finger tips are pressed against the palm of the hand. The end of the thumb is then pressed down on the proximal phalanx of the index finger. 

As most trained martial artists are already aware, the actual mechanics of a good punch start with a solid or rooted stance, upon which pelvis/body rotation (the amount varying with the martial art style) and arm extension are added.  To be an effective punch, the energy of the body and extending arm must be efficiently transferred through the forearm, wrist, hand, and on into the target.  To understand the path that this energy must take, it is useful to delve into the basic anatomy of the upper limb.

The single upper arm bone, or humerus, actually makes contact (articulates) with two bones of the forearm – the radius and the ulna.  By far, the articulation with the ulna is the strongest and most stable.  It is because of this relationship that the majority of the body and arm extension energy of a punch is transferred from the humerus, and on to the ulna.  A problem occurs, however, as the energy is transferred down the ulna and on towards the wrist.  At the wrist, it is the radius-not the ulna- that actually makes the strongest articulation with the carpal or wrist bones. 

To effectively transmit energy on to the target, a mechanism is needed to transfer a significant portion of the ulnar energy to the radius, which is in a better anatomical position to transfer the energy on to the hand.    A band of very tough connective tissue called the interosseous membrane accomplishes this by connecting the ulna and radius, much like the canvas sling portion of a stretcher connects the two carrying handles.   A significant amount of force, which might actually break the ulna, is “shared” with the radius via this membrane.  The energy transferred to the radius is then directed through the carpal (wrist) bones, then to the metacarpals (between wrist and knuckles), and finally on to the target. 

A key point is that the degree of energy transfer via the interosseous membrane depends on how tight it is, which depends on the amount of twist in the forearm.  The tighter this membrane, as occurs in a vertically oriented punch, the better the forearm bones share the energy – and transmit it from the humerus to the wrist and hand.  The more the hand/fist is turned towards pronation (palm down, as in a horizontal punch) – the more relaxed the interosseous membrane becomes.  Therefore, a full corkscrew punch is done with the membrane in a conformation in which it is least able to transmit force from the ulna to the radius!  A more vertical punch, as in Isshinryu or some of the Kung Fu styles, will allow better sharing and transmission of force, or, to put it another way, a stronger punch.

The vertical aspect of the Isshin Ryu fist is also very conducive to efficient energy transmission from the hand to the target.  The two striking knuckles are aligned with the largest and strongest of the metacarpal bones – those bones that will transfer energy from the radius and carpal bones, on to the knuckles.  Boxers (and other untrained fighters) often hit with the last two knuckles!  This causes the force to be transmitted through metacarpals 4 and 5 (associated with the ring and baby finger, respectively), which simply aren’t as thick and strong as two and three are.  The result can be what is clinically called a “boxer’s fracture” – breakage of metacarpals four and/or five. (Mike Tyson did this many years ago when he got into a “street fight” with Mitch Green in a clothing store.  Mike hit Mitch one time - with an un-taped & ungloved hand!  The result was that Mike received a boxer’s fracture of one of his metacarpals.)

The vertical fist also tends to keep the elbow in close to the body, which has the benefits of both protecting the ribs and of maximizing energy transmission from the body to the arm.  A palm-down fist loses these attributes to a certain degree, especially when punching along a vector that is parallel to the floor.  High-speed films of Tae Kwon Do practitioners doing board breaks show that, at the time that the fist contacts the board, the fist is actually in a vertical orientation – thus allowing for maximum energy transmission!  It is only after the fist passes through the plane of the board that the palm-down position is achieved.

The advantage of the vertical fist is also illustrated, indirectly, by the fact that many defensive tactics instructors teach the more powerful “tilted” palm-heel strike, in which the fingers (of a right-hand strike) are oriented to the 2 o’clock position, as opposed to the “traditional” 12 o’clock orientation. 

In this position, the person is basically throwing an open-hand version of the Isshin Ryu punch!  (If this is unclear, try the following:  Place your hand in a traditional palm-heel position, with the fingers pointing upward to the 12 o’clock position.  Now straighten the hand to align it with the forearm, as you curl the fingers into a fist.  It will be a palm-down fist.  Do the same with the palm-heel in the “tilted” orientation.  When you straighten the hand and curl the fingers, you will be in the standard Isshin Ryu vertical fist!)

As a final consideration of the vertical or Isshin Ryu fist, consider the intrinsic forearm muscles and their effect on punching.  To have the hand in full pronation (palm down) or full supination (palm up) requires the use of some intrinsic muscles of the forearm known respectively as the pronators and supinators. A punch is best thrown when these two muscle groups are in a balanced condition, i.e., when neither is “dominating” the other.  An unbalanced condition occurs whenever there is full supination (e.g., a classic uppercut), or full pronation (e.g., a classic corkscrew punch, ending with the palm facing down.)  The most “neutral” position of the hand is best as far as balancing these two sets of muscles, and when punching with maximum force.  As an example, the forearm/hand group is in a fairly neutral position when someone initially extends their hand to “shake hands” with someone else.  (To use a clock face, the thumb of the right hand would be at approximately 11 o’clock.)  This neutral position is optimum for energy transmission through the arm/forearm.  Energy in a punch is a function of both the mass of the moving limb, and the speed at which the limb moves. 

     A limb can move fastest, thus maximizing energy, when it is told to do as few things as possible.  So – making a fist, and then extending the arm in a vertical punch (i.e., neutral position) will generally be faster than making a fist and extending the arm in a punch while you are also asking the forearm to twist to a palm-down position.

All political and style-based rivalry aside, the above anatomical relationships provide powerful support for the conclusion that the Isshin Ryu vertical fist is better, both structurally and functionally, at delivering the

most energy to a target, in the shortest amount of time, and with the least stress to the arm and hand.”

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