Martial arts feature defensive or attacking techniques that involve movement of the body. In order to execute such techniques, the body needs to maintain its centre of gravity, centre of mass, base of support, balance and stability.
Centre of gravity
The earth pulls everything towards itself, and this pulling force may be termed as gravity of the earth. Any matter on earth experiences this force. Thus, besides flora and fauna, human beings also experience this force. All the human body parts experience this force all the time. For example, the head, chest, abdomen, arms, and legs experience the gravitational force of the earth. All these individual gravitational forces experienced by all the individual human body parts, when added up result in a resultant force-torque, which is also known simply as a resultant force. This resultant force is zero at a particular imaginary point in the body, and this point is known as the “center of gravity” of the body. Therefore, the centre of gravity of a body is a point around which the resultant torque due to gravity forces vanishes.
Line of gravity
If a line is drawn from the point of the centre of gravity towards the centre of the earth, then that line is known as the line of gravity. The line of gravity is just a vector representation of a straight line that originates from the point where the centre of gravity of the body is located, and it travels downwards towards the centre of the earth. The centre of gravity always remains inside the body, while the line of gravity starts from the inside and then goes outside the body.
TutorVista video “Centre Of Gravity – Defintion, Examples, Experiment”:
In human beings, the centre of gravity is visualized as a point that is anterior to the sacral vertebra. Depending upon various factors, generally, in a static body, the centre of gravity may be behind the level of the umbilicus or slightly below the umbilicus. Since a martial artist is constantly in motion, thus for a dynamic body, the centre of gravity goes on constantly shifting according to the moving positions of the body.
Centre of gravity used to transmit power
The centre of gravity may be used to transmit power. There are many ways of transmitting power in martial techniques. One way is to transmit the power from the feet towards the point of attack or defense, by twisting the hip. Another way is to utilize the knee in a spring action known as a “sine wave” technique. Still another way is not to twist the hip or use the sine wave, but to twist the upper body on the line of gravity with the fulcrum point being the centre of gravity. This enables the power to come from the point of the centre of gravity, and is thus a bit faster, but it produces less power as compared to the power from the twisting of the hip. However, in situations where the hip is immobilized in some grappling move, or is fractured, then this technique might be very effective. The following video shows how the centre of gravity may be utilized to transmit power.
Radek Scuri video “Tatsuya Naka 7th dan Shotokan Karate _ Center of gravity”:
Centre of mass
A collection of particles of matter may loosely be called as a mass of particles. Every part of the body has some mass, which when added up, result in a weighted relative position of the distributed mass that sums up to zero. This relative position is an imaginary point that is known as the centre of mass.
hplcchmc video “Body Center of Mass Example – Motion Analysis”:
Centre of gravity versus centre of mass
Centre of gravity and centre of mass are same
If the field of gravity is uniform, then the centre of gravity and the centre of mass will be the same. For example, on earth, the field of gravity is uniform and so for all objects on earth, the centre of gravity and the centre of mass will be the same.
Centre of gravity and centre of mass are different
If the field of gravity is NOT uniform, then the centre of gravity and the centre of mass will not be the same. For example, for objects in space, the earth may have stronger gravity (if closer to the earth), or weaker gravity (if farther from the earth). Thus, objects in space, for example satellites, may experience an offset between the centre of gravity and the centre of mass, resulting in an applied torque. Hence, in space, the differences between centre of gravity and centre of mass are apparent. Few differences may be seen in the following interesting video of the International Space Station, where the weight of the body and the earth’s gravity is felt very slightly only.
DOCUMENTARY TUBE video “HOW IT WORKS: The International Space Station”:
Since martial artists are human beings who reside on the planet Earth, hence for all practical purposes on earth, the centre of gravity and the centre of mass may be considered as one and the same. Therefore, martial arts techniques may be studied considering that the centre of gravity and the centre of mass are interchangeable, and both have the same meaning.
BertecHQ video “Movement Science Explained: Center of Mass and Center of Gravity”:
Base of support
When any matter rests on any surface, then that surface is called as its support. For example, if a person is standing on the ground, then the soles of the feet come in contact with the ground, and so the ground is called as the support for the feet. The area of the ground that is enclosed by the outside edges of the feet is known as the base of support for the feet.
If the feet are together than the base of support is less, whereas if the feet are wide, then the base of support is more. The line of gravity should always remain somewhere within the base of support to maintain balance and stability. If the line of gravity moves outside the base of support, then balance is lost. This is a very important principle. On this principle, all fundamental movements of all martial arts of the world are built upon. Innumerable martial arts techniques are also built upon this single principle. Therefore, always maintaining the line of gravity inside the base of support is of paramount importance for any sincere martial artist.
Judovision video “JUDO TECHNIQUES: Base of support / Center of gravity explained”:
Balance and stability
Balance is a state of the body that resists falling. A body which retains balance shows stability. If the line of gravity is within the base of support, then the body remains in a balanced position. Again, the closer the centre of gravity is to the base of support, the greater is the stability of the body. For example, Sumo wrestlers place their legs wide, so that a large base of support is created. They also bend down so that the centre of gravity is nearer to the ground. Again, due to the symmetry of the stances in Sumo wrestling, the line of gravity is always within the base of support. All these together lend great stability to the Sumo wrestler. The following videos show the concepts of balance and stability.
Jerome Guzzo video “Sumo Training at Hakkaku Stable”:
pdhpe.net video “Balance and Stability”:
Island Top Team video “The Science Behind Your Jiu Jitsu 1 Center of Gravity, Stability, and Balance”:
Breaking balance and stability
To defeat an opponent, a martial artist needs to break the balance and stability of the opponent. This can be done by making the line of gravity of the opponent come outside the opponent’s base of support. If the line of gravity comes anywhere outside the base of support, then the opponent will lose balance and most likely suffer an injurious fall. This means that the height, strength, or the weight of an opponent is of very little importance, if the opponent’s line of gravity is made to come out of its base of support. For example, throwing techniques of Judo skillfully utilize this principle.
Sampson Judo video “How to Break Someone’s Balance”:
Utilizing the opponent’s momentum
In Aikido, one’s own centre of gravity is used to align with the flow of the opponent’s momentum, rather than going against it by blocking it. Going with the flow helps to utilize the opponent’s momentum to one’s own advantage and this principle is used effectively in Aikido. The following video shows the legendary martial artist Morihei Ueshiba, the founder of Aikido, who expertly demonstrates such movements where his body’s centre of gravity aligns with the momentum of the opponent, in order to break the opponent’s balance and stability, with the least effort required.
Velko Spasov video “Aikido Morihei Ueshiba Old Japanese Documentary”:
Maintaining one’s own balance while breaking the balance of the opponent, is of crucial importance in any fight. Therefore, various kinds of balancing exercises are practiced by martial artists. The following videos show few exercises to improve balance and stability.
Brian Devero video “The Supernatural Balance of the Ninja”:
Ireno Fargas video “World Taekwondo Training Program DVD. No.1 Balance training / English language”:
Yoga with Kassandra video “15 min Beginner Yoga for Balance & Stability”:
Every fundamental movement in every martial art of the world, is so designed that the centre of gravity/mass can easily shift from high to low or vice-versa within the body, while the line of gravity always remains within the base of support; thereby, enabling perfect balance and stability during the execution of different martial art techniques. Therefore, mastering fundamental movements like stances, blocks, punches and kicks, should be enthusiastically practiced by any martial artist. Mastering fundamental movements also helps to a very great extent to prevent injuries to oneself. Moreover, mastering the fundamental movements is a very effective way to learn how to maintain one’s own balance, while disbalancing the opponent, in the various changing circumstances of a fight.
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