Biomechanical Analysis of the Reverse Punch Technique in Karate and 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 one with empty hand. The impact is dispersed when somebody is hit with the boxing glove. The empty hand concentrates impact because of the smaller size of the fist.
Question: Why is there more penetrative power when somebody hits with the empty fist? Answer: 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 in hitting, pushing and throwing executions, the first muscular region to be contracted is the pelvic girdle. From there, the accumulated muscular force travels up to the shoulder, arm and finally to the fist. The muscles of the lower extremities enter into play at the same time, starting with the body twisting/arm pushing movement. These stabilize the final pushing action of the arm.
During the early development of shot-putting, great champions such as James Fuchs in the 1950 have and later on Parry O’Brien, created different styles to achieve maximum shot put distance. They considered hip work (more than anything else) as the prime mover in shot-putting. 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 that weight training far exceeds benefits attributable to improvements in technique. Interestingly, weight training does not drastically develop the muscles of the hip region. But working on other parts of the body – such as the shoulder, back, and arm – seems to give an edge to those athletes (particularly boxers) who use the shoulder region muscles more. Karate and boxing coaches know that the heavier a body part, (particularly the pelvic region) the more force can be pushed into action. Additionally, the lighter the body part (particularly the arm) the faster the execution of the technique.
Let’s begin 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, the quadriceps femoris (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 amp; semitendinosus, biceps femoris (long head). The calf and the foot muscles are not described in this article.
The pelvic girdle (region) links the trunk and the lower extremities. Here we find the most important muscles for reverse punch execution.
Ventral and interior muscles include the musculus iliopsoas, psoas major and iliacus). These act mostly as flexors, but the dorsal and exterior muscles act as extensor at the time of punching. The gluteus maximus is the most superficial and bulkiest muscle, and its action includes extension, rotation, adduction and abduction on the thigh. Gluteus medius and g. minimus are also extensors/rotators. Gluteus minimus is the only muscle between the gluteus family which medially rotate the hip joint and abducts the femur.
Several muscles from the lower/ventral part of the torso are also extremely important in reverse punching. They include the musculus obliquus externus abdominis, obliquus internus, and transversus abdominis. These compress the abdomen, helping to support the abdominal viscera against the pull of gravity, they contribute for the hip rotation during reverse punch. Also they cause trunk rotation and flexion.
The most important muscles of the shoulder girdle are:
Deltoideus ventral fascicule is the most important muscle of the shoulder girdle. This produces internal rotation of the arm, the dorsal fascicule produces external rotation and the middle fiber adduct the humerus. The musculus teres major is an internal rotator/adductor of the arm and synergist with latissimus dorsi amp; antagonist to the dorsal fiber of the deltoid. Musculus subscapularis is an internal rotator of the humerus. Another two muscles are important for reverse punch execution. They are latissimus dorsi and pectoralis major. Both rotate medially and adduct 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 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 muscles:
Musculus triceps brachii is one of the most important and strongest muscles which are 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
As I mentioned earlier, the force used in any punching (pushing or throwing) begins from the hip region and progresses to the shoulder, upper arm, elbow and lower arm muscles. Finally, this force is transmitted to the punching fist. The leg muscles begin contracting at the same time as those of the hip girdle. Well known, that beginners (karateka or boxer) are unable to use correctly the hip rotation in punching as the “first muscular link.”
In case of a shot putter or discus thrower the beginner has the advantage of the time to deliver the expected force by not only rotating the hip, but also rotating the body. However, advanced karateka use the hip rotation as the first link in transmitting the force to 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. The posture is very similar in both sports. 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 energetically 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 too. A boxer does not rotate the hip as hard when he executes the reverse punch for two reasons:
1. The left fist is withdrawn close to the left shoulder or the boxer’s face, where it is used to protect the face and jaw;
2. The boxer tends to lean forward and uses the right shoulder more to augment the punch’s 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 show the use of the hip by the karateka. Photo 3. Shows a real match where the left arm is open to the possibility of blocking or catching the opponent’s arm. Photo 4. Shows 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, and perhaps other styles too. Photo 5. and 6. Clearly show the use of shoulder by boxers.
Ph. 5. Reverse punch executed by a boxer Ph. 6. Reverse punch executed by a boxer
Now I’d like to go into greater detail about the effectiveness of the reverse punches used in karate and boxing. I stated earlier that boxers are more effective even though they don’t use their hip region musculature in an effective way. You might ask, “Why is it so difficult to rotate the hip as the first part of the kinematic punching chain?” The answer is simple: hip region musculature is the heaviest in the human body and a lighter body part is easier to move than a heavier part!
By the way the hip is considered the heaviest part of the human body by most instructors and kinesiologists, but in our case the shoulder region includes a tiny part of the upper region of the chest, which is the correct way establishing the shoulder region.
Additionally, the trunk can be divided theoretically into three parts. The lower part is the pelvic or hip girdle. The middle comprises the abdomen and the upper region comprises the chest and shoulders. As the hip starts to rotate, so almost instantaneously does the rest of the trunk; this continuing to the shoulder. Muscles are contracted less efficiently at hip level than at the shoulder level because the shoulder muscles (deltoideus, trapezius and pectoralis) are broad and have greater force production than the relatively smaller hip muscles which are found on the inner surface of the pelvis. These muscles laterally rotate the hip joint.
Gluteus maximus, medius and minimus are larger muscles and they are found on the outer surface of the pelvis. They abduct and medially rotate the hip joint which is exactly important in reverse punch action. Gluteus maximus is an exception which laterally rotates the hip. In the transmission of the punching force the serratus anterior has an assisting role.
- Hip and shoulder rotation involve an eccentric force which produces translation and rotation. Its effect known as “torque,” where torque ( G ) or ( T ) = Force x distance. We express it more correctly in mechanics where the torque is measured in Newton’s ( N ) x meters T = (N-m).
- The magnitude of the hip torque 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 for the shoulder. Here the available force is less because the short lever arm. Also, the longer the lever arm, the higher the speed. This is why the boxer develops higher velocity and ultimately, more momentum (see explanation later on). Because we speak about rotary motion we have to make a differentiation between the rotary and linear motion by describing inertia.
The tendency of a body to remain in its state of rest or motion until acted upon by an outside force termed inertia. This is Newton’s first law of motion and is equally applied to a body which moves in a straight line or which moves in a rotary path. The big distinction between the two motion (linear and rotational) is that to move or stop an object which moves in a linear path is easier than the body which moves in a rotational path. The tendency to resist against motion or to stop/slow down (angular resistance) under rotary condition named moment of inertia.
When the rotating mass is multiplied by the square of its distance from the axis of rotation we speak about moment of inertia (I) I = kg x m2 or transfer of momentum. The torque ( G ) also represented by moment of inertia (I) times angular acceleration (a). G = I · a. 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, as is the moment of inertia. 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.
When the rotational force (torque) from the shoulder is transformed into rectilinear (straight) force then the impact force will be equaled by the stopping force coming in the opposite direction (Newton’s III law). This force comes from the attacker’s body, which reflects back the same magnitude of force to that delivered to it. The kinetic energy of impact is absorbed into potential energy and some of this will be dissipated as heat. 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 with no rotation (e.g., a bullet is rotating around its axis). So now you are beginning to see the pros and cons emphasizing the shoulder more than the hip rotation for developing better penetrating force.
Now I would like to describe and clarify the hip and shoulder torque actions. Mass, weight, force and gravity are closely related. Mass represents the quantity of matter that comprises an object. Mass is measured in kilograms. The mass represents the measure of a body’s inertia, i.e., its resistance to acceleration. Weight is the product of the mass of an object and the acceleration due to gravity (which is approximately 9.80 m/sec2). Force defines a pulling or pushing action that causes a change in the state of motion of an object or a mass. In mechanics F = m x a, where F – represents force, m – represents mass and a – represents acceleration. Force is measured in Newton’s (N) and in this case, 1 Newton = 1kg 1m/sec2. A body of 70 kg mass has 686 N force (70 kg x 9.80), but how can we measure the force by Newton’s of the individual body segments. The answer to this is not simple.
I will use an approximate description based upon anthropometric calculations of different body segments made 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 contributed approximately 12% and the shoulders approximately 16% of the total 100% body mass. Analyzing this data indicates that the shoulder region is larger and also is heavier. 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 region.
The mass of one arm (only one arm) is approximately 4.94% of body mass so we can calculate the arm force of a 70 kg body mass as 4.94 x 9.8 = 48.41 N. The mass of the hip region for the same body mass is 11.18%, so hip force is 11.18 x 9.8 = 109.65 N. The mass of the shoulder region in a similar weight person accounts for 15.96% of the mass, so the force it generates is 15.96 x 9.8 = 165.40 N. According to these calculations it is obvious that the shoulder can deliver more force than the hip.
Additionally, the shoulder is directly connected to the arm so discharge of the shoulder force is immediately transmitted to the arm. The hip region transmitting force is somehow lost because the torso muscles which transmit the necessary force are not directly connected to the shoulder. So overall, shoulder action delivers approximately 10% more force than the hip by adding also the total arm mass.
However, a big question is remains: how can we calculate the acceleration and impact force of the arm itself? This cannot be calculated without using highly specialized apparatuses capable of measuring impact force and/or acceleration.
You need to know something about levers because this will help you understand some of the principles being talked about here. Levers in human anatomy basically comprised of bones. 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 levers in mechanics are described as long arms (or objects) connected to a rotational axis at one end and the line of action where the force is activated, at the other end. Lever arm is named also moment arm or force arm. In daily activity using a lever the work is done much easier. There are three types of levers known as class 1, class 2, and class 3.
While it is difficult to decide in some cases, we can say that the majority of human levers fall into classes 1 and 3. Look at the shoulder, for example. Here the vertebral column is the fulcrum and the head of humerus (with its connection to the scapula) makes up a class 2. The fulcrum is at one end of the lever; the load is in the middle (the shoulder muscles) and the effort is considered to be the articulation of the humerus which the athlete uses for pushing punching.
However there may be a problem here because the vertebral column has no connection with any bone to the shoulder and certainly not to the humerus. The humerus is connected to the scapula laterally in the glenoid cavity and the clavicle on the dorsal par of the body through the acromion of the scapula. In general terms the muscular connection to clavicle and scapula represent the lever arm. In our case the vertebral column could not represent the axis because the clavicle is attached to the sternum (sterno-clavicular joint). However the sternum is close to the vertebral column so the sterno-clavicular joint and vertebral column together can work as one during reverse punch. The lever arm as a rigid entity in this case can be described is the clavicle.
The above described explanation to establish the leverage in human body is fairly difficult. In mechanics the case is simple where no sophisticated connections are found such as in the human body.
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.
It may help to better understand the forces (muscles and bones) acting at the shoulder girdle in terms of the moment of inertia which has been described earlier. When speak about moment of inertia in terms of body mass, we could be referring to total mass amount or only just a particular portion
article of the mass of the body/object in question and 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 that same mass is farther form the axis. 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. E.g., the head is spherical, the upper arm is cylindrical, the forearm is conical etc. In this case we can find different publications where 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-m2). We need the following segments and their moment of inertia:
Total arm length (upper arm, forearm and hand) = 0.0294 kg-m2
Upper level of the trunk (both shoulders) = 0.441 “
Lower level of the trunk (hip girdle) = 0.399 “
This clearly shows the advantage of the shoulder over hip region. Now we need briefly to mention impulse and momentum. Impulse is described as the relation between the force and time (F x t). A better impulse will be produced by a greater magnitude of force or a longer time application of the existing force. When sufficient force is applied to a mass, an acceleration will occur, because the change in time of velocity. F = m x a, from this equation rearranging the following yields that F = m (?f - ?i) where the ?f = final velocity and the ?i = initial velocity and t = time.
A karateka or boxer needs an impulse to initiate a punch. This impulse is mostly a nervous impulse generating force from muscular contraction. Then the impulse becomes momentum and later on when there is a contact then there is an impulse again.
Momentum expresses the relationship between mass and velocity, Momentum = m x ?. Analyzing the importance of the impulse result that the impulse of a force (Ft) is equal to the change of momentum (m?f - m?i) that it produces. 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 the longest time over which to apply the force to the ball before releasing it.
Another example in baseball is the hitter which is often encouraged to follow-through when striking a ball. High speed films of the collision between bats/rackets and balls have shown that the act of following through serves to increase the time over which collision occurs. Surprisingly this prolonged time for hitting, favors not the force of impact between the ball and the bat but favors the change velocity of the ball. So this example is more important for acquiring distance than impact force.
In karate however is a different story. The karateka must favor force over the time. Where the force is larger and the time is shorter the impact will be devastating especially wen the punching arm will be withdrawn or bounced off. The withdrawn arm or in karate terms Snap-Punch is which will creates more devastating effect on the opponent. To demonstrate the time and force relations which are inversely proportional here is a table which demonstrates this.
Let’s say we need to inquire 100 N for the max. effect of a blow push.
F x t = J
Force (N) Time required Acquired impulse
|100 N 1 sec 100 units (max. impulse)50 N 2 sec 100 units (max. impulse)25 N 4 sec 100 units (max. impulse)
1 N 100 sec 100 units (max. impulse)
We don’t need to prove that a ping-pong bat doesn’t hit the tennis ball as hard or as far as does a tennis racquet, the ball will have a shorter landing distance. Knowing this, we can understand that the hip has a shorter distance by turning and delivering 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.
That summarizes, then the pros and cons of hip versus the shoulder power and I believe I have shown that the shoulder is probably more effective than the hip. Even so, I still believe that reverse punch begins with hip action acting in unison with the rest of the torso and shoulder muscles. If you want to compare the contact force output generated by a boxer and a karateka by means of force testing apparatus, then both should be barehanded or both should wear a light boxing glove. Make your data more encompassing by using different methods and different force/impact detection apparatus.
Prof. Emeric Arus is the President/Founder of the International Sendo-Ryu Karatedo Federation For contact: 27-18 Newtown Ave., Astoria, NY 11102/USA or visit www.sendo-ryu.com and firstname.lastname@example.org or email@example.com
Prof. Arus is the author of the book of “Sendo-Ryu Karatedo, The Way of Initiative” and a new DVD “Sendo-Ryu Karatedo and Sticky Hands Combat Jujutsu.