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Biomechanical Analysis of Reverse Punch Technique in Karate & Boxing
The Effectiveness of the Reverse Punch, by Prof. Emeric Arus, Ph.D., MS.
This article describes the biomechanical differences of the reverse punch executed by a karateka and by a boxer. Also try to shed light about the effectiveness of the two sports.
There are great differences of opinion between karateka and boxers over which sport has the better hitting power, which is more effective destroying an opponent. The author hypothesizes that boxers hit harder than karateka. This means, that their punching efficiency (momentum and/or force) is better than a karateka’s. The author has different assumptions about his hypothesis:
1. Boxers in general are better trained athletes.
2. Boxers are better fit and they can generate a greater force, because they have larger mass then karateka.
3. Karateka are more supple athletes with less bulky muscles that is why their force (mass x acceleration) is less effective.
Let us say for the sake of argument boxers train exclusively for arm techniques and karateka train for arm and leg techniques this could mean the time spent on effectiveness for punching techniques is less for the karateka. It is important to differentiate between a punch with a boxing glove and an empty handed. The impact when somebody hit with the boxing glove is dispersed when somebody hit with empty handed it is more concentrated/penetrating because the smaller size of the fist.
Question: Why is there more penetrative power when somebody hit only with the empty fist? Answer: The smaller the target energy is concentrated on a very small point (particularly on the two knuckles of the fist) and with the same amount of energy (which comes from the mass behind) the impact will be more devastating than in the case of hitting with a glove where the energy of impact will dissipate.
Prior to explaining the biomechanical hypothesis of the hitting efficacy of these two sports we will describe the muscular kinematic chain specifically involved in the execution of the reverse punch. It is important to state that everybody knows that in the major hitting, pushing and throwing executions, the first muscular region to be contracted is the pelvic girdle, then from that the accumulated muscular force travels up to the shoulder, arm and finally to the fist. Also at the same time starting with the execution of the body twisting and arm pushing movement, the lower extremity muscles enter into play to stabilize the final pushing action of the arm.
At early stage of techniques in shot putting great champions such as James Fuchs in the early of the 1950’s and later on Parry O’Brien, created different styles to achieve maximum distance in shot putting. They considered hip work (beyond other things) is the guiding force for shot putting. Having stated this, karate coaches put a lot of emphasis on hip rotation while teaching during the early stages.
By the same token, boxers are working more than karateka on weight training and it seems likely, though, that the influence of weight training far exceeds that attributable to improvements in technique. Interestingly everybody knows that weight training does not drastically develop the hip region muscles and by working on other body segments such as the shoulder, back and arm, it seems to give an edge to those athletes who use more the shoulder region muscles, particularly the boxers.
Basically every karate and boxing coach knows that the heavier a body part, (particularly the pelvic region) the more force can be pushed into action. Also the lighter the body part (particularly the arm) the faster the execution.
Let’s start with a short description of the most important muscles involved in a reverse punch. We would like to specify that these muscles have mostly the role of adductor, rotator intern, extensor and pronator.
Here is the kinematic chain in the execution of the reverse punch
From the thigh region down: Ventral part of the thigh between other muscles the quadriceps femoris (the all four parts vastus lateralis, medialis, intermedius and rectus femoris) is the most important. Dorsal part of the thigh and lower part of the pelvic girdle there are musculus gluteus maximus (buttock), semimembranosus & semitendinosus, biceps femoris (long head). The calf and the foot muscles are not described in this article.
The pelvis girdle (region) links the trunk and the lower extremities. Here are the most important muscles active in reverse punch execution.
Ventral part and interior muscles are the musculus iliopsoas, psoas major, iliacus, and psoas minor. These muscles act mostly as flexors, but the dorsal and exterior muscles act as extensor at the time of punching. They are the gluteus maximus which is the most superficial & bulkiest muscle and its action includes: extension, rotation, adduction and abduction on the thigh. Gluteus medius and gluteus minimus are also extensors and rotators.
From the lower ventral part of the torso several muscles are extremely important in reverse punching. They are musculus obliquus externus abdominis, obliquus internus, transverses abdominis. These muscles produce trunk rotation, flexion of the trunk.
The most important muscles of the shoulder girdle are: Deltoideus ventral fascicule which produces internal rotation of the arm, the dorsal fascicule produces external rotation of the arm. The musculus teres major is an internal rotator and adductor of the arm & synergist with latissimus dorsi & antagonist to deltoid. Also the musculus subscapularis is an internal rotator of the humerus.
Upper arm ventral part most important muscles are: Musculus coracobrachialis is a tiny muscle compared to biceps brachii. This muscle is deeply situated somehow under the biceps it is a strong adductor of the humerus and acts as a forward projector of the arm. Musculus brachialis situated at the front and lower part of the biceps, also behind. Is a flexor of the forearm on the upper arm and is a tensor of the articular capsule of the elbow. It is an important muscle protecting the elbow in general.
Upper arm dorsal part most important muscle: Musculus triceps brachii is one of the most important and strongest muscles which is an extensor of the forearm, tensor of the elbow’s articular capsule, adductor of the upper arm through caput longum insertion at the scapula beneath the glenoid fossa. The forearm muscles are not described in this article.
Biomechanical hypothesis of the reverse punch
Recall the previous explanation which explains that in any punching (pushing, tossing, throwing) execution of the force starts from the hip muscular region, then followed by the shoulder, upper arm, elbow, lower arm muscles then finally the force will be transmitted to the punching fist. The leg muscles start contracting at the same time when the hip girdle starts to contract.
It is well known, that none of the beginners (karateka or boxer) cannot use the hip as the first “muscular link” correctly for rotation. During rotation the hip muscles are contracted. In case of a shot putter or discus thrower the beginner has the advantage of the time for delivering the expected force by not only rotating the hip, but also rotating the body. However advanced karateka are indeed using the hip rotation as the first link transmitting the force for the rest of the muscular link. Karate instructors emphasize the importance of the hip rotation.
Analyzing a right hand reverse punch (gyaku zuki in Japanese) the athlete (karateka or boxer) stands with the left foot forward in a fighting position. In both sports this position is very similar. The reverse punch executed by the karateka: At the time of pushing forward the right fist there is a rotation of the fist from a supine position to prone position and the left hand is energically pulled back to the left hip.
By pulling the left fist energetically to the hip, the karateka adds more rotational force to the hip, and more stability to the karateka. By the same token, when a boxer executes the same right reverse punch, he does not rotate the hip as hard, for two reasons:
1. The left fist is not withdrawn to the hip, but only to the left shoulder or eventually in front of the boxer face (used for protecting of the face).
2. Most of the time when the boxer punches he leans forward and using his right shoulder force to augment the punch effectiveness.
Ph.1. Reverse punch executed by a karateka Ph.2. Reverse punch executed by a karateka
Ph.3. Reverse punch executed by a karateka Ph.4. Reverse pushing punch
Photos 1. and 2. Clearly shows the use of the hip by the karateka. Photo 3. During a real match shows that the left arm is open for the possibility of blocking or catching the opponent arm. Photo 4. The writer demonstrates a reverse pushing punch where the shoulder is pushed forward for extra force delivery. This technique can be seen in Wado-ryu, Sendo-ryu styles, perhaps other styles too. Photo 5. and 6. Shows clearly the use of shoulder by the boxers.
Ph. 5. Reverse punch executed by a boxer Ph.6. Reverse punch executed by a boxer
Now we would like to dissect our question about reverse punch effectiveness of karate and boxing. It has been previously stated that boxers have more effectiveness in their executions even if they are not using more efficiently their hip region musculature. The writer will show some other biomechanical considerations. The reader simply can ask why it is so difficult to rotate the hip as the first kinematic chain in punching. The answer is simple. Because the hip region musculature is the heaviest in the human body. A lighter body part is easier to move than a heavier part.
Another consideration about the hip region. The trunk can be divided theoretically in to three parts. The lower part of the trunk is the pelvic or hip girdle, the middle region comprises the abdomen and the upper region comprises the chest and shoulder part. When the hip starts to rotate, almost instantaneously the rest of the trunk parts start to rotate, then continues immediately with the shoulder. At hip level, muscles are contracted less efficiently than at the shoulder level, because at shoulder level muscles are larger and stronger such as deltoideus, trapezius, and pectoralis. They are broad and have greater force production than those long and narrow muscles at the hip level except the gluteus maximus. The intercostals and external abominis muscles have very short fibers and they can deliver force for a very short distance.
Biomechanical considerations
The hip torque magnitude is smaller at the beginning of the rotation time, then in case of a shoulder, where the torque is greater.
If the spine is considered as the axis of rotation then the perpendicular distance from the axis to the line of action of the force (the lever arm) is shorter for the hip than in case of the shoulder. In this case the force which can be utilized is reduced because the short lever arm. Also as longer the lever arm as better the speed. Having described these advantages for the boxer means that they have a better velocity and ultimately they have a better momentum (see explanation later on).
3. Hip and shoulder rotation involves an eccentric force named torque, where torque ( Γ ) or (T) = Force x distance or more correctly in mechanics where the torque is measured by Newton (N) and in this case, Γ = N-m. When the rotating mass (m) where the Greek delta δ represents the magnitude, is multiplied by the square of its distance (r) from the axis of rotation we speak about moment of inertia (I) or transfer of momentum I = ∑r2 ∙ δm, where the Greek sigma (Σ) represents the total sum. The torque ( Γ ) also represented by moment of inertia (I) times angular acceleration (α). Γ = I ∙ α Torque may be increased by increasing the magnitude of force or by increasing the length of the lever (moment arm).
If the mass of an object is concentrated close to the axis of rotation, the object is easier to turn because the radius for each particle is less, thus making the moment of inertia less. Conversely if the mass is concentrated farther away from the axis (in the case of the shoulder), inertia becomes greater and the rotating body will require more force to start or stop it.
Finally when the rotational force (torque) from the shoulder turns into rectilinear (straight) force then, as great the penetrating force then the stopping force will be equally as great in the opposite direction (Newton’s III law). This force comes from the attacker’s body which means that the body of the opponent will react with the same magnitude of force back to the attacker. In our case the kinetic energy will be absorbed into potential energy and also there will be a potential energy dissipation into heat energy. However, the defender’s body will react by absorbing the energy of the attack damaging itself.
It should be kept in mind that a rotating body is more difficult to stop than a body moving in a straight line. A rotating body has more penetrating force than one who has no rotation. E.g., the bullet is rotating around its axis. So far the reader saw the pro and con against the theory using more the shoulder than the hip rotation for getting better penetrating force.
We would like now to describe and clarify the hip and shoulder torque action measured in Newton. Mass, weight, force and gravity has very close relationships. Mass represents the measure (by kg) of the amount of matter that comprises an object and represents the measure of the inertia in kg or lb. Weight is the product of the mass of an object and the acceleration due to gravity (which is approximately 9.80 m/sec2). Force represents an action of pull or push that causes a change in the state of motion of an object or a mass. In mechanics F = m x a, where the F – represents force, m – represents mass and a – represents the acceleration. Force is measured by Newton (N) and in this case Newton = 1kg 1m/sec2. It is known that a body which has 70 kg mass has 686 N force (70 kg x 9.80). But how can we measure the human body segments by Newton? The answer to this question is not simple.
In this article the author will use an approximate description using some anthropometric calculation of different body segments by different authors. According to V.M. Zatsiorsky, PhD., Professor at Pennsylvania State University, describes mass segments of body parts from 100 physically fit young men, where the hip region is approximately 12% and the shoulder region (both shoulders) is approximately 16% of the total 100% body mass. In analyzing the body bone structure, if we take into account the shoulder outer edge of the humerus head (both humerus head in the frontal plane of the body) is larger in diameter with approximately 11 to 13% than the ilium left and right side (pelvic bone) outer edge.
Analyzing this dates results that in any case the shoulder region is larger and also heavier. The reader could ask that what parts (bones and muscles) covers the shoulder region and what parts bones, muscles and internal organs cover the hip region. The reader should consult some anatomical books to find the answer.
Recall about finding out how we can measure the human body segments by Newton, the writer will make connection and uses the aforementioned body mass segments described by Dr. Zatsiorsky. We are interested about the mass of the shoulder region, the mass of the total length of the arm (from shoulder to end of the hand) and the mass of the hip girdle.
Particularly the arm mass (only one arm) is approximately 3.45% related to 70 kg body mass. To calculate the arm force in Newton is 3.45 x 9.8 (1 N) = 33.81 N. The hip region force in Newton related to 70 kg body mass is 8.4%, then 8.4 x 9.8 (1 N) = 82.32 N. The shoulder region force in Newton related to 70 kg body mass is 9.8%, then 9.8 x 9.8 (1N) = 96.04 N. According to these calculations it is obvious that the shoulder can deliver more force than the hip. Also the shoulder is connected to the arm directly so the discharge of the shoulder force is immediately transmitted to the arm. The hip girdle transmitting force is somehow lost because the torso muscles which transmit the necessary force are not directly connected to the shoulder. According to the aforementioned different calculations the difference between the hip and the shoulder girdle is approximately 12 to 14% in favor of the shoulder.
According to the author’s calculations there still remains a big question, which are the acceleration and the impact force of the arm itself? This cannot be calculated without using an adequate and necessary apparatus measuring impact force and/or acceleration.
In order to be more convinced about the aforementioned facts about shoulder and hip, the reader should know something about levers. Levers in human anatomy basically comprised of bones and muscles together. Levers are not only rigid bars; they represent the perpendicular distance from the axis of rotation (fulcrum) to the line of action of a force.
However in mechanics levers are described as long arms or objects which are connected to a rotational axis at one end of the arm and the other end of the arm is connected to a line of action where a force is activated. Lever arm is named also moment arm or force arm. In daily activity using a lever the work is done much easier. We know that there are three kinds of levers. Lever class 1, class 2 and class 3.
Basically it is difficult to describe which segment of the human body uses lever class 1, 2 or 3. However the majority of human levers are classified as lever class 1 and 3. If we analyze the shoulder using the vertebral column as the fulcrum and the head of humerus with its connection to the scapula then this kind of connection is a lever class 2, where the fulcrum is at one end of the lever the load is in the middle of the lever and is considered to be the shoulder muscle and the effort is considered to be the articulation of the humerus which the athlete uses for pushing/punching for the executing of an effort.
However is there a problem? The vertebral column has no connection with any bone to the shoulder, particularly to the humerus. The humerus is connected to the scapula laterally in the glenoid cavity and the clavicle on the dorsal part of the body through the acromion of the scapula.
See the length of the lever arm advantage in case of hip and shoulder (Fig.1.)
The hip does approximately 45 degree turning while the shoulder can do approximately 90 degrees turning. The diagram is viewed from the top of the head.
The lever arm as a rigid entity in this case can be best described is the clavicle. In this case the vertebral column could not represent the axis because the clavicle is attached to the sternum (sterno-clavicular connection). However the sternum is more closed to the vertebral column. So the sterno-clavicular and vertebral column complex should work together as an entity in our case of reverse punch.
For a better understanding about the forces (muscles and bones) acting at the level of the shoulder girdle is easier if we do not use lever description, but just mention “moment of inertia.” The moment of inertia is an important concept in biomechanics where the mass or the body rotates. The inertia is the resistance of a body to changes in its motion. In the case of linear motion, the inertia of a body is measured by its mass; the more massive a body, the greater its inertia and more difficult it is to change its linear motion.
With angular motion a similar state of affairs exists except that it is not only the mass of a body that determines its resistance to changes in motion, but also how this mass is distributed relative to the axis of rotation. If the mass is concentrated close to the axis, it is much easier to alter the angular motion of a body than if the same mass is farther from the axis. The angular rotation equivalent of mass as a measure of a body’s resistance to a change in its motion is termed the moment of inertia.
Please see the earlier described mathematical equation. The reader should know when we speak about moment of inertia, and we refer to body mass, that could be the total mass amount or only a particular portion/particle of the mass of the body/object in question.
The moment of inertia of a body can be determined in a variety of ways. One of these methods is the “segmentation method” where human segments are compared to geometrical shapes if the body is regular shape. E.g., the head is spherical, the upper arm cylindrical, forearm is conical etc. In this case we can find different publications where different authors enumerate body segments and their moments of inertia. The author will use such an example for the following body segments and their moment of inertia (kg-m 2). We need the following segments and their moment of inertia:
Total arm length (upper arm, forearm and hand) = 0.0294 kg-m 2
Upper level of the trunk (both shoulders) = 0.441 “
Lower level of the trunk (hip girdle) = 0.399 “
These dates also show the shoulder region advantage over the hip region. Few words about Impulse and Momentum. Impulse is described as the relation between the force and time. Having a larger magnitude of force or having a longer time to exert the existing force will have a better impulse. Impulse = F x t. When sufficient force is applied to a mass, an acceleration will occur where the acceleration happen because the change in time of velocity. F = m x a from this equation rearranging the following yields that F = m (νf - ν i)/t where the νf = final velocity and the νi = intial velocity and t = time.
To start a punching execution the karateka or boxer needs an impulse. This impulse at the very beginning of the execution of the punch is mostly a nervous impulse where the force comes from the muscular contraction, then turns for momentum.
Momentum represents the relationship between mass and velocity, Momentum = m x ν. Analyzing the importance of the impulse result that the impulse of a force (Ft) is equal to the change of momentum (mνf - mν i) that it produces. In this way the impulse-momentum relationship is basic to an understanding of many sports techniques including our article. The importance of creating as large an impulse as possible is evident in the case of a baseball pitcher. The pitcher uses his bat that allows the longest time over which to apply the force to the ball before releasing it.
Everybody knows that using a ping-pong racket versus a tennis racket (using the same tennis ball), the ball will have a shorter landing distance. Knowing this, we can understand that the hip has a shorter distance by turning and eliberating the force (let’s compare as a ping-pong racket) versus the shoulder (compare as a tennis racket) so the impulse and momentum will be larger. See Figure 1. Shows the hip and the shoulder relationship.
In conclusion we showed the pro and con of the effectiveness of using the hip power versus the shoulder power and we showed the probability of having more effectiveness using the shoulder more than the hip. However the writer’s opinion is that the hip should start turning first with unison of the rest of the torso muscles and shoulder smoothly.
In case of testing the contact force output by using a force testing apparatus between the karateka and the boxer, then both should be bare handed or use a light boxing glove. The best way to reach a conclusion, the reader should test the karateka and boxer reverse punching technique by using different methods and possible different apparatuses.
Note: The reader should have basic understanding the anatomical terminology of the muscles in Latin and basic knowledge of biomechanics or mechanics/physics in general.
Prof. Emeric Arus is the President/Founder of the International Sendo-Ryu Karatedo Federation
For contact: P.O.Box 674, Livingston Manor, NY 12758 or
Prof. Arus is the author of the book “Sendo-Ryu Karate-do, The Way of Initiative.”
