Biomechanics of BJJ 4: Levers and Moment Arms

An understanding of leverage and moment arms will be crucial for students to understand how and why certain techniques work. The human body is composed of a system of levers: bones act as rigid bars, joints act as fulcrums, and muscles provide the effort. By manipulating the shape of your body you can influence how much force you can produce and how much load you can withstand. Leverage is what allows a smaller person to control a larger person. While an in-depth discussion of levers are beyond the scope of this manual, the most important aspect of a lever is that the further away force is applied on the lever the stronger the force will be on the other side of the lever. Thus, by attacking at the end of the lever students will be able to control their opponent much more efficiently. Simply, levers multiply force.

Another useful aspect of attacking the end of the lever is the use of torque. While some techniques will require pushing or pulling linearly against the opponent, many times a practitioner will be required to move the opponent’s limbs out of the way. This is accomplished through the use of torque in order to turn the opponent’s body and limbs. Again, the most important aspect that can be relayed to students is that by pushing or pulling further away from the joint the more torque is produced. The length between the fulcrum and where force is applied is called the moment arm, the longer the moment arm the more force will be applied at the joint. This can be demonstrated easily with a door – by pushing on the door on the opposite side of the hinges we can easily open the door, however if we push on the side closest to the hinges it will take significantly more force to open the door.

The further away from the fulcrum you apply force, the less force is needed.

This understanding can also be applied throughout all positions during training. A cardinal rule of BJJ is to keep the arms close to the body, students are often told to keep their elbows glued to their ribs or to make T-Rex arms. This is to prevent both the arm from extending out and also to prevent the arms from crossing the midline of the body. These positions are considered weak due to the mechanics of the arm. When the objective is to move an opponent’s arm one can muscle through the movement in order to achieve the objective, expending more energy than required and producing more strain on the body. However, if one understands how leverage works they will be able to move the arm by pressing on the end of the arm – thus saving energy and creating a mechanical advantage.

When the arm is extended straight in front of the body its center of mass is far from the origin of the arm, thus possessing a larger moment arm that can be used to generate torque. This extended position can easily be disrupted by applying torque at the end of the arm, knocking it out of position.

A powerful example of leverage is the use of underhooks. Since underhooks are established under the armpits they allow for torque to be created about the opponent’s center of gravity. Underhooks allow for manipulation of the opponent’s body through the use of leverage.

Read more about Biomechanics in Chapter 5: Gravity & Center of Gravity

Biomechanics of BJJ 3: Laws of Motion and Force

Basic Mechanical Principles


The three laws of motion, as taught by Newton, are as follows:

The Law of Inertia: The property of matter that makes an object continue its current state of motion until acted upon by an outside force.

The Law of Acceleration: The amount of force needed to accelerate an object is directly proportional to how much mass that object has, and the faster you want to accelerate an object the more force you have to utilize.

The Law of Reaction: For every action, there is an equal and opposite reaction.

These laws can be taken advantage of in BJJ by understanding a few key principles.

  • The amount of force needed to change a body’s motion depends on both the mass and speed of the body. A heavier person will be harder to move than a lighter person, and a faster person will be harder to stop than a slower person. Inertia is the reason weight classes are required in competition, a heavier person will always have a mechanical advantage over a lighter person.
  • A person who is moving will require a lot of force to stop their movement, however, it takes far less force in order to continue their movement. Some techniques in BJJ require using an opponent’s momentum to your advantage. Students should be taught to take advantage of their opponent’s momentum by pushing their partner along a path that they have already started on. This will overextend their opponent and allow for the student to take advantage of the overextension. Students should also be taught not to overextend themselves by forcefully moving with speed or they can be taken advantaged of. This can easily be seen in the elbow push side-mount escape, or the sacrifice throw in Judo.
  • It takes a lot of force to start a person’s movement. Many sweeps take advantage of an opponent’s momentum. If an opponent is knowledgeable in BJJ techniques, they will be difficult or impossible to sweep or submit from a static position. Attacks must be set up by destabilizing an opponent in the direction opposite of the sweep. The forceful movement the opponent uses to return to their original position can be taken advantage of by providing the momentum needed to complete the sweep.


            In the most basic sense, forces are simply the push or pull exerted onto an object or person – forces are any action or influence that moves an object. This could be the pull on a sleeve or lapel, or pushing on an opponent. This could also be the push or pull exerted on the ground. Forces can be split into two categories: internal and external forces. Internal forces are forces that are generated within one’s own body, and consists of muscular contractions, ligament restraint, and skeletal structure. External forces are the forces that act upon the body from outside of the body – these include gravity, friction, and an opponent’s body (Winter, 2009).

By teaching students to take advantage of all the forces available to them, both internal and external, they will be able to successfully and efficiently control both their own body and their opponent’s bodies. There are three ways to recruit force:

  1. By using muscular force to push or pull directly on the opponent
  2. By pushing off the floor, one can drive into their opponent
  3. By using the force of gravity to apply weight on the opponent

The first two methods are available to both the top and bottom position, but since the force of gravity is always pulling downwards – only the person on top can take advantage of gravity. Students should be taught to drive off the ground to keep their base and to drive into an opponent. Keeping a strong posture while driving off the ground will allow for a stronger and more efficient transfer of force. The easiest production of force to teach students to utilize is the use of their own muscular force since most people already have an understanding of pushing and pulling on their opponent.

When instructing students to use force during a technique, they should be taught to take into consideration the following aspects:

1) Magnitude of force

Students should be taught how much force will be needed for a particular technique. Students should not use any more force than necessary in order to reduce energy expenditure and strain placed on the body. One consideration before attempting to use force is the understanding that to move a large amount of mass, a large amount of force will be needed. A larger opponent will always require more force to move than a smaller opponent.

2) Direction of application

Regardless of how much force a student can recruit, they will be unable to accomplish their movement goal if the direction of the force is incorrect. For example, many beginning students will bridge strongly with much effort in order to escape mount. However, if the direction of force is applied incorrectly, such as straight up towards the ceiling instead of over the practitioners shoulder, the bridge will serve no purpose except for expending energy.

3) Point of application

The point of contact when force is used will determine which movement will follow. If force is applied at an opponent’s center of mass then the movement created will be linear. However, the further away from the opponent’s center of mass the more torque will be created. If a technique’s purpose is to move the opponent directly forward or backward then the point of application should be at the opponent’s center of mass. If the technique’s purpose is to turn the opponent, the force should be applied further from the center of mass.

4) Distance and time of application

More force can be applied over a longer period of time and distance. This concept is important during top positions such as mount. The longer amount of time a student is mounted on their opponent, the more force they can exert on their opponent in order to sap their opponent’s stamina. The distance of application can be seen during the bridge defense against mount – the longer the distance of the bridge (the height of the bridge) the more force will be generated. Sometimes a large powerful movement through a short amount of time will be desired, but in some cases force over a long period of time will be more useful.

Read more about Biomechanics in the next chapter – Levers and moment arms

Biomechanics of BJJ 2: Anthropometry and Form

How Anthropometry dictates specialization

Although most humans have the same basic shape, the variations of measurements such as mass, length, and girth for each body segment of both competitors will dictate the most effective techniques that can be used. For example, long and lanky individuals will be more likely to achieve submissions such as triangles and play open guards such as dela riva or spider guard (Ryan Hall, Keenan Cornelius). Short stocky individuals will find more success in closer positions such as butterfly and will be able to succeed with submissions such as armbars due to the ability to get closer to their opponents (Marcelo Garcia, Gary Tonin). More flexible individuals may find success in Eddie Bravo’s 10th planet system which requires pretzel levels of flexibility. It is up to both the instructor and students to figure out which game works best for the individual.

What is form and why should you care?

There is no platonic ideal for good form. Good form is simply the performance of a movement in which the action goal is accomplished with minimal energy expenditure and strain placed on the body. That is not to say that energy expenditure and strain should be avoided, but that there will always be an optimal amount to be endured. Performing a hip-bump to escape a heavier opponent’s mount will involve great effort, energy expenditure, and will stress and strain the body, however by using the optimal amount of effort, one can accomplish the task while minimizing energy expenditure and strain placed on the body.

It is imperative for a long-lasting BJJ career that proper form is maintained during rolls. While maintaining good form may be difficult and prevent a student from being dominant at first, it will pay off as training time increases. It is important to note that many practitioners will utilize bad form but still have success in spite of bad mechanics due to compensation by using more energy and more muscular effort. This compensation combined with bad form will lead to injuries over time. It is also important to note that there is not a singular correct way to accomplish a task, but many correct ways. One of the primary jobs for a coach is to help students figure out the optimal way to adapt a movement that is suitable for their anthropometry while reducing risks of injury. It must be acknowledged that there is no one correct way to perform a movement.

It is also true that certain high-level competitors will purposely choose to use dangerous biomechanical positions in order to achieve certain maneuvers. However, this should not encourage you to teach the same positions as this would be dangerous for your student’s longevity. Many high-level competitors end up with chronic pain due to abusing their bodies throughout their competitive careers. Rickson Gracie, known to many as one of the greatest BJJ athletes has eight herniated discs. Ricardo Liborio, the founder of American Top Team, has seven herniated discs. Rodolfo Vieira, one of the top competitors of the current era, had to take a sabbatical from competition and training due to a herniated disc. Bodily sacrifices must be made at the highest levels of competition, however, during training form should be focused on and pain should not be endured in order to “win”. Most students are training in order to improve their quality of life, and should train in a way to decrease their risk of injury.

What is good form?

In general, good form requires a strong posture, keeping a strong rigid core and a braced spine. Muscles of the core from the glutes, hips, abdominals, and back extensors must be continually active to prevent the collapse of the postural structure. You must keep an erect spine in order to prevent stooping or hunched posture. Stooped and hunched posture require greater muscular effort to sustain and place more load on the spinal discs (Nordin and Frankel, 2001). Strong posture must be maintained during all positions. While attempting standing guard passes the practitioner should keep their spine braced, otherwise their position will be broken down by the bottom player. While in an offensive side-mount, a strong posture will allow the practitioner to efficiently transfer the force from driving off the ground.

It should be noted that posture can fatigue. During drilling of certain positions such as spider guard, the rounds should be kept short in order to prevent the collapse of posture during training in order to reduce injury risks. Exercises should also be introduced to training in order to develop postural endurance – such exercises will be introduced in the strength and conditioning chapter.

Continue reading about Biomechanics in BJJ Biomechanics Part 3

Biomechanics of BJJ 1: Intro to Biomechanics

Biomechanics is the study of the mechanical structure and function of a human body which give rise to movement – how and why the body moves. The human body is confined to the rules of physics. By examining the body through the lens of physics we can understand how the body operates and what constraints it must operate in. The benefits of such knowledge should be readily apparent. Proper understanding of how the body works will allow a coach to communicate knowledge in a clear way and will be instrumental in the success of their students. In turn, proper understanding of the conceptual basis for movement will allow students to understand techniques instead of simply parroting the techniques.

All humans navigate the world using the musculoskeletal system – an organ system that allows for shape, protection, posture, and movement. This system that allows for movement is made of a skeleton that acts as a rigid structure, muscles that act as motors to provide internal force, and joints that act as levers. If the muscle provides enough internal force to overcome the
external forces, the body can move.

For the most part, everybody has the same basic body structure – a head connected to a torso, and four limbs extending from the torso. Each of these body parts will allow for movement in the same general way; knees and elbows flex and extend in one plane of motion, hips and shoulder move relatively freely, and spines can bend in many directions. Each of these joints move independently, allowing for almost infinite configurations, shapes, and postures the body is capable of. It is imperative for students to understand how to properly use their body and its parts in order to be strong and efficient.

BJJ can be seen as a complex game in which two bodies attempt to move the other into a position that yields a submission. In order to be successful in BJJ a student must:

  1. Use their body to maintain stability
  2. Use their body to cause instability in their opponent
  3. Take advantage of the opponent’s instability
  4. Produce and control force in order to maximize the results as efficiently as possible

Continue reading about BJJ Biomechanics 2