BALANCE: STABILITY Vs. MOBILITY
"The whole of science is nothing more than a refinement of everyday thinking", Albert Einstein (crazy looking smart dude)
Introduction
In training we hear about balance all the time. But what does it actually mean? A standard definition is "the ability to move or to remain in a position without losing control or falling". Balance, like coordination, is understood by virtually everyone to be the basis of any skillful movement; yet do you know how to define balance or coordination such that we can train it specifically for our goals. How do you measure balance statically or whilst in motion, and what impact will this have on our ability to fight or defend? In this section we will define balance, in terms of the stability / mobility paradigm. Stability and mobility are the basis for every technique you have or will ever learn. They define your ability to block, strike, evade, kick, throw etc. An understanding of this most basic of skills can enable you to increase the speed, power and coordination of all your abilities statically or dynamically and alternatively it will enable you to attack your opponents balance robbing him (or her) of their most basic ability to attack, defend or even respond.
Objectives:
In training we hear about balance all the time. But what does it actually mean? A standard definition is "the ability to move or to remain in a position without losing control or falling". Balance, like coordination, is understood by virtually everyone to be the basis of any skillful movement; yet do you know how to define balance or coordination such that we can train it specifically for our goals. How do you measure balance statically or whilst in motion, and what impact will this have on our ability to fight or defend? In this section we will define balance, in terms of the stability / mobility paradigm. Stability and mobility are the basis for every technique you have or will ever learn. They define your ability to block, strike, evade, kick, throw etc. An understanding of this most basic of skills can enable you to increase the speed, power and coordination of all your abilities statically or dynamically and alternatively it will enable you to attack your opponents balance robbing him (or her) of their most basic ability to attack, defend or even respond.
Objectives:
- Understand the meaning of Stability & Mobility and how they relate to any technique.
- Ability to asses your stability and mobility at any point in time and understand how to use this to improve any technique or combinations of techniques.
- Ability to use the above knowledge to improve existing training programs and modify them for specific goals
- Ability to use the knowledge of stability and mobility to disrupt your opponents decision and response capabilities during a combat situation
- Basic understanding of OODA loop concept (See Response & Training)
- Sense of Humor
- Ability to learn then ignore big words
Center of Gravity (CoG)
The CoG is an imaginary point near or within a body, through which its weight can be assumed to act. The CoG is useful in predicting the behavior of a body (moving or stationary) when it is acted on by gravity and or external forces. In martial arts it is often referred to as the point of balance. The location of the CoG is dependent on the shape and position of our body. We need to think of our body as comprising of segments; its easiest to think of the body and limbs between the joints like lower leg, thighs, torso, upper and lower arms and the head. Anytime one of these changes orientation or position the CoG will also change. It is important to note that the CoG may even be located outside your body. It is critical to understand where your CoG is as its position determines your stability and mobility. The actual formula for CoG based on a number of segments (n) is given by:
The CoG is an imaginary point near or within a body, through which its weight can be assumed to act. The CoG is useful in predicting the behavior of a body (moving or stationary) when it is acted on by gravity and or external forces. In martial arts it is often referred to as the point of balance. The location of the CoG is dependent on the shape and position of our body. We need to think of our body as comprising of segments; its easiest to think of the body and limbs between the joints like lower leg, thighs, torso, upper and lower arms and the head. Anytime one of these changes orientation or position the CoG will also change. It is important to note that the CoG may even be located outside your body. It is critical to understand where your CoG is as its position determines your stability and mobility. The actual formula for CoG based on a number of segments (n) is given by:
Where the X, Y and Z are the CoG position in three dimensions as a function of the mass of each segment (mi) and the xi, yi, and zi coordinates of each segments individual centers of mass.
You don't need to remember this formula, but you need remember that the each individual body segments influence over the position of the CoG is proportionate to its weight and distance from the center. So even an outstretched arm or leg can shift your CoG further than expected. This must definitely be considered when performing actions or using weapons at full extension. Other factors to consider are body build, age and gender and the following key points are also worth remembering:
Stability
Stability is defined as the ability to resist the influence of external forces; a push or a pull or impact without losing balance. To understand this we need to introduce the concept of a line of gravity (LoG) and the Base of Support (BoS):
Line of Gravity (LoG): this is an imaginary line from the center of gravity vertically to the surface on which you are supported.
Base of Support (BoS): this refers to the area beneath an object or person that includes every point of contact that the object or person makes with the supporting surface. These points of contact may be body parts e.g. feet or hands, or they may include things like crutches or the chair a person is sitting in.
In the simplest terms you are stable and able to maintain balance if the line of gravity (LoG) through your CoG is within your base of support. The following image shows the CoG, LoG and base of support (BoS) for various poses.
You don't need to remember this formula, but you need remember that the each individual body segments influence over the position of the CoG is proportionate to its weight and distance from the center. So even an outstretched arm or leg can shift your CoG further than expected. This must definitely be considered when performing actions or using weapons at full extension. Other factors to consider are body build, age and gender and the following key points are also worth remembering:
- An average males CoG is located at approximately 57% of standing height,
- A females CoG is at approximately 55% of height (I tell my wife its the hips and thighs :) ).
- In a standing position you can approximate the height of your CoG as in the vicinity of your navel
- The height of the CoG directly affects stability, the lower your CoG the greater your stability.
Stability
Stability is defined as the ability to resist the influence of external forces; a push or a pull or impact without losing balance. To understand this we need to introduce the concept of a line of gravity (LoG) and the Base of Support (BoS):
Line of Gravity (LoG): this is an imaginary line from the center of gravity vertically to the surface on which you are supported.
Base of Support (BoS): this refers to the area beneath an object or person that includes every point of contact that the object or person makes with the supporting surface. These points of contact may be body parts e.g. feet or hands, or they may include things like crutches or the chair a person is sitting in.
In the simplest terms you are stable and able to maintain balance if the line of gravity (LoG) through your CoG is within your base of support. The following image shows the CoG, LoG and base of support (BoS) for various poses.
The image above shows various poses for a human being. The top image shows the CoG relative to the body in front and side view, and the bottom image is the corresponding BoS and the position for the line of gravity projected on to the BoS. Notice the influence of body shape and stance on stability. In the first image our model is standing upright his CoG is approximately 57% of his height and the projection of his LoG falls directly into the center of his base of stability; he can move his upper body (punching, blocking, pushing or pulling) in all directions without losing balance. In the second image our model has bent forward to such an extent that the CoG is outside of his body and outside of his BoS, he will have to fall forward onto his hands to regain stability or continue into a roll. In the third image our model has moved his upper body backwards shifting his LoG to the very edge of his base of stability, he can only move his upper body forward otherwise he will lose balance to the rear; this is a precarious situation particularly if he has just evaded a punch from the front. In our last image the model has shifted his upper body significantly to his right, yet his LoG is still well within his base of stability and he still has some room to move before his stability is compromised.
These concepts are critical to your ability to judge how good a stance is given the situation. The shape of your body and the positioning of your feet determine not only your level of stability but how much of a margin you have and in what directions. Correct application of this knowledge can ensure you remain balanced even when pushed, pulled or impacted and correct application can also ensure you can respond in all required directions without compromising your stability and balance.
These concepts are critical to your ability to judge how good a stance is given the situation. The shape of your body and the positioning of your feet determine not only your level of stability but how much of a margin you have and in what directions. Correct application of this knowledge can ensure you remain balanced even when pushed, pulled or impacted and correct application can also ensure you can respond in all required directions without compromising your stability and balance.
Tipping Moment & Tipping Angle
The image above shows two stances, a fighting stance and a horse riding stance. To compare the stability we can compare moments of force that would be required to tip them from that position. You can think of moments of force like a spanner and a bolt (and our CoG is the bolt), you need to apply a force at some distance (leverage) to provide a rotating force. A moment of force is defined as Force x perpendicular distance to the center. The force acting on the body is that of gravity and it equals the mass of our person (100kg) x acceleration due to gravity (9.8 meters per second every second) and it acts through our CoG. In both cases the force is the same F = 100 x 9.8 = 980 Newton's (the SI unit of force is newton's). So when we try to unbalance our fighter we have to provide enough rotational force or leverage to tip him. In both examples above we think of his left foot coming off the ground and then being pivoted through an arc about his remaining foot, until his CoG is tipped out of his BoS. The point at which he begins to rotate is when we provide a turning moment of F x distance of stance for each case (see image above). In the horse riding stance it required 735 newton meters of torque, and in the fighting stance it required only 196 newton meters (see the image above). Thus the Horse riding stance is 3.75 times more stable than fighting stance; note this is only in the left to right plane, notice if we look at the side view for both stances the distances to the center are different in the forwards and backwards directions, and in fact in the fight stance our fighter has more stability front and rear. From this basic example we can see that the stability is directly proportional to the tipping moment which we control with the length and direction of the stance. There is another factor which also affects the tipping moment and that is the mass of the fighter, the required tipping moment of force was equal to mass (weight in kilograms) multiplied by acceleration due to gravity multiplied by the length of stance, hence for the same stance a heavier opponent will have greater stability.
The other critical factor in the stability example is the height of the CoG relative to the width of the stance. If you look at the CoG in both stances there is a blue arrow which shows the circular arc the CoG would have to be rotated through before the fighter completely lost his balance (his CoG leaves his BoS). The angle of this arc is known as the tipping angle. The greater the tipping angle the greater the stability. Another aspect which can be seen from the diagram is the direction of the tipping arc, in the horse riding stance example the arc goes higher, meaning we actually have to lift his CoG and thus his bodyweight through a greater height, this requires much more energy as we are fighting gravity also. In the fighting stance arc the tipping angle is much smaller and the amount the CoG rises against gravity before he loses balance is also much smaller. There are two extreme cases; one where the fighter is standing tall with feet together, his tipping arc and tipping moment are the smallest they will ever be (on two feet that is), and there is almost no vertical component to his tipping arc, he will fall over with a very small push or negligible throw. The other extreme case is that of a person with the widest base possible and the lowest CoG possible, he is lying spread eagle on the ground; in this case his arc is as big as it can ever be and his CoG is as low as it will ever get (unless he is 6 foot under :) ), he is as stable as he can ever get. This is why people get low or go to ground when wrestling, this is also why ground fighting takes so much energy.
From the above analysis we can summarize the key points to consider regarding stability:
Mobility
When we move by stepping we are really continuously tipping ourselves out of our BoS, over and over again. So now instead of an opponent providing the tipping moment and energy, we have to provide it ourselves. In this type of movement mobility is actually the exact opposite of stability; the wider and lower our stance the worse our mobility. Think of walking or jogging, the longer the stride the harder the work; this is because we have to lift our bodyweight higher and further for each step, this also increases the impact force per step as our body weight also drops further into each step. So for stepping motion we purposely move our LoG to the edge of our BoS in the direction we wish to step and then we fall into our next stance, we recover stability and control again once our LoG is back in the new BoS. If we are walking or running we just repeat this cycle over and over. We perform similar actions whenever we perform moving directional changes and or jumping and stepping techniques. I like to think of this type of motion as CONTROLLED UNSTABLE MOTION.
With controlled unstable motion our mobility is a function of the size of our BoS and how close our CoG and LoG are to its edge. So looking at the two extreme cases from stability above; the man standing upright and with feet close together has high mobility in all directions whereas the guy spread eagle on the ground has almost zero mobility. So every stance is a tradeoff between mobility and stability. If you understand this principle you can use it against your opponent in many ways:
We will use this knowledge in all tutorials and theory moving forward, understanding CoG, BoS, LoG and the stability / mobility tradeoffs make sure you can always strike or defend and move in a superior manner to your opponent. You will see in the next section on Force and Motion that stability and mobility also directly influence impact force when either dishing it out or receiving it.
Advanced Motion
There are two other types of motion we can consider aside from the previously defined CONTROLLED UNSTABLE MOTION, these are dynamic stability and unbalanced motion.
Dynamic Stability: Is the ability to move the body such that we keep the LoG within the BoS during all movements. This includes the movement of the BoS with our CoG and includes accelerating and decelerating motions. These movements can be simple or complex and even continuous in motion. Examples of dynamic stability should be all punches, blocks and non jumping / flying kicks. An excellent example of stability within a moving BoS is a Tai Chi Form or slow Katas. This is an advanced form of motion because you utilize mobility within your BoS or you move such that your CoG and BoS remain aligned. This is more about controlled transfer of weight and I will cover this in great detail during the Force and motion theory and the practical video tutorials. The last form of motion which we should personally avoid or encourage in our opponents is:
Unbalanced Motion: This is the state of unplanned and uncontrolled motion where your CoG is moving without any real terminal control and it is accelerating beyond any point of planned recovery. The most common example of this in a martial arts scenario is a person who has lost all balance; he has either been thrown or overreaches on a punch or kick; his momentum carries his CoG outside of the BoS and he does not have the mobility or balance to recover a stable BoS before it is to late. The best case is he feels a bit silly and has to review the material about stability and understand how he got himself into this predicament, the worst case is he has either smashed into some object or the ground with enough force to incapacitate himself or his opponent uses this opportunity to incapacitate him. Either way in most cases this can be avoided through effective understanding and use of the stability / mobility paradigm.
Attacking Your Opponents Mental & Physical Balance
An understanding of the CoG, and BoS enable us to attack an opponents balance and thereby attack his (or her) cognitive process or mental balance. We can attack the physical and mental balance directly or indirectly. When we do not have the strength or power to directly attack our opponents balance we can exploit his involuntary responses and get him to unknowingly shift his own CoG in an unexpected manner. We saw in the theory on Training and response that our brain has non-cognitive responses which are automatic and involuntary; a great example is when we touch something hot, without cognitive thought we pull our hand away very quickly only realizing it after the fact. We can use this type of response to great effect as our brain responds similarly to any such stimulus which is both intense and unexpected or something unexpected which threatens some critical function of our body. Pressure point attacks best fall into this category, some pressure points are very painful and yet we have all experienced the students who can resist the pressure point when they know its coming. If on the other hand they don't know the pressure point attack is coming it will most likely trigger the automatic response; to me the important aspect is not of the "touch of death" idea from movies but the ability to exploit the fact that our opponents respond without thought and as a result they unknowingly shift their CoG. This leads to two scenarios; in the first they wind up in an unbalanced state having shifted their CoG beyond their BoS or in the second case they have shifted their CoG within the BoS such that their initial strategy is no longer functional. In either case after the initial shock, the unexpected shift of their CoG triggers the cognitive OODA loop; they must now go through the Observe, Orient, Decide and Act cognitive loop stages before they can recover effectively. This creates a response lag on their part and gives us significant timing advantage. We can either continue to attack the OODA loop rendering them into a state of decision lock, or use the timing advantage to shape the situation and in the words of Jonh Boyd (father of OODA loop) "unleash a barrage of heinous acts upon our adversary" . In the direct attack we physically attack their balance and stability. With an understanding of the BoS and an ability to see or feel it we can attack it. Balance attacks can be subtle or quite direct, throws and sweeps are about as direct as you can get and more subtle approaches are any of the softer redirection techniques. In any case the person is unbalanced and either physically incapacitated through impact or joint destruction or the unbalance triggers the same OODA loop response giving us the cognitive and timing advantage. I will expand on this concept in almost every practical tutorial moving forward as it is my favorite concept; this is at the heart of every martial art which is size or strength independent.
The other critical factor in the stability example is the height of the CoG relative to the width of the stance. If you look at the CoG in both stances there is a blue arrow which shows the circular arc the CoG would have to be rotated through before the fighter completely lost his balance (his CoG leaves his BoS). The angle of this arc is known as the tipping angle. The greater the tipping angle the greater the stability. Another aspect which can be seen from the diagram is the direction of the tipping arc, in the horse riding stance example the arc goes higher, meaning we actually have to lift his CoG and thus his bodyweight through a greater height, this requires much more energy as we are fighting gravity also. In the fighting stance arc the tipping angle is much smaller and the amount the CoG rises against gravity before he loses balance is also much smaller. There are two extreme cases; one where the fighter is standing tall with feet together, his tipping arc and tipping moment are the smallest they will ever be (on two feet that is), and there is almost no vertical component to his tipping arc, he will fall over with a very small push or negligible throw. The other extreme case is that of a person with the widest base possible and the lowest CoG possible, he is lying spread eagle on the ground; in this case his arc is as big as it can ever be and his CoG is as low as it will ever get (unless he is 6 foot under :) ), he is as stable as he can ever get. This is why people get low or go to ground when wrestling, this is also why ground fighting takes so much energy.
From the above analysis we can summarize the key points to consider regarding stability:
- The wider the base of support, the easier it is to maintain balance in that direction.
- Lowering the CoG increases your stability as it allows for greater angular displacement of the CoG within the bounds of of the base of support.
- To maximize the margin of stability, the line of gravity should intersect the base of support in such a way that it provides for the greatest range of movement within the base. If you expect an attack from a certain direction you should use a stance which gives you the greatest BoS in that direction. If you are not certain from which direction an external force is going to act on your body, it is best to make yourself stable by having the line of gravity fallover the center of the base of support and have stability in all directions.
- The greater the mass, the greater the stability. Stability of an object is increased if you increase the mass of the object. It will take a greater external force to set the object off balance.
- The greater the friction between the supporting surface and the parts of the body in contact with it, the more stable the body will be. Improper friction makes it difficult to maintain one's BoS under the influence of external forces.
Mobility
When we move by stepping we are really continuously tipping ourselves out of our BoS, over and over again. So now instead of an opponent providing the tipping moment and energy, we have to provide it ourselves. In this type of movement mobility is actually the exact opposite of stability; the wider and lower our stance the worse our mobility. Think of walking or jogging, the longer the stride the harder the work; this is because we have to lift our bodyweight higher and further for each step, this also increases the impact force per step as our body weight also drops further into each step. So for stepping motion we purposely move our LoG to the edge of our BoS in the direction we wish to step and then we fall into our next stance, we recover stability and control again once our LoG is back in the new BoS. If we are walking or running we just repeat this cycle over and over. We perform similar actions whenever we perform moving directional changes and or jumping and stepping techniques. I like to think of this type of motion as CONTROLLED UNSTABLE MOTION.
With controlled unstable motion our mobility is a function of the size of our BoS and how close our CoG and LoG are to its edge. So looking at the two extreme cases from stability above; the man standing upright and with feet close together has high mobility in all directions whereas the guy spread eagle on the ground has almost zero mobility. So every stance is a tradeoff between mobility and stability. If you understand this principle you can use it against your opponent in many ways:
- If your opponent is lower and wider he can't move as fast as you and it takes more effort for him to move and strike. Take a shorter more mobile stance, make him move he will tire quickly.
- If your opponent takes an asymmetric stance (longer in one direction than the other), he is less mobile in the longest direction and less stable in the shortest portion. Use angle stepping and motion to make him either less directionally stable or less directionally mobile depending on how you wish to attack (or defend). If he is not well trained he will move and momentarily have zero stability, this might be the best strategy for attack.
- If he is a heavy hitter attack in the direction of least stability as he will not be able to transmit a great deal of force in that direction when striking (see force and momentum section).
- If you like to take people to ground, use directional movement to align his BoS and your line of attack to rob him of stability.
- If you are fighting a wrestler or grappler either increase your stability to counter a takedown, or use distance and angles to destroy his mobility before he can shoot in.
We will use this knowledge in all tutorials and theory moving forward, understanding CoG, BoS, LoG and the stability / mobility tradeoffs make sure you can always strike or defend and move in a superior manner to your opponent. You will see in the next section on Force and Motion that stability and mobility also directly influence impact force when either dishing it out or receiving it.
Advanced Motion
There are two other types of motion we can consider aside from the previously defined CONTROLLED UNSTABLE MOTION, these are dynamic stability and unbalanced motion.
Dynamic Stability: Is the ability to move the body such that we keep the LoG within the BoS during all movements. This includes the movement of the BoS with our CoG and includes accelerating and decelerating motions. These movements can be simple or complex and even continuous in motion. Examples of dynamic stability should be all punches, blocks and non jumping / flying kicks. An excellent example of stability within a moving BoS is a Tai Chi Form or slow Katas. This is an advanced form of motion because you utilize mobility within your BoS or you move such that your CoG and BoS remain aligned. This is more about controlled transfer of weight and I will cover this in great detail during the Force and motion theory and the practical video tutorials. The last form of motion which we should personally avoid or encourage in our opponents is:
Unbalanced Motion: This is the state of unplanned and uncontrolled motion where your CoG is moving without any real terminal control and it is accelerating beyond any point of planned recovery. The most common example of this in a martial arts scenario is a person who has lost all balance; he has either been thrown or overreaches on a punch or kick; his momentum carries his CoG outside of the BoS and he does not have the mobility or balance to recover a stable BoS before it is to late. The best case is he feels a bit silly and has to review the material about stability and understand how he got himself into this predicament, the worst case is he has either smashed into some object or the ground with enough force to incapacitate himself or his opponent uses this opportunity to incapacitate him. Either way in most cases this can be avoided through effective understanding and use of the stability / mobility paradigm.
Attacking Your Opponents Mental & Physical Balance
An understanding of the CoG, and BoS enable us to attack an opponents balance and thereby attack his (or her) cognitive process or mental balance. We can attack the physical and mental balance directly or indirectly. When we do not have the strength or power to directly attack our opponents balance we can exploit his involuntary responses and get him to unknowingly shift his own CoG in an unexpected manner. We saw in the theory on Training and response that our brain has non-cognitive responses which are automatic and involuntary; a great example is when we touch something hot, without cognitive thought we pull our hand away very quickly only realizing it after the fact. We can use this type of response to great effect as our brain responds similarly to any such stimulus which is both intense and unexpected or something unexpected which threatens some critical function of our body. Pressure point attacks best fall into this category, some pressure points are very painful and yet we have all experienced the students who can resist the pressure point when they know its coming. If on the other hand they don't know the pressure point attack is coming it will most likely trigger the automatic response; to me the important aspect is not of the "touch of death" idea from movies but the ability to exploit the fact that our opponents respond without thought and as a result they unknowingly shift their CoG. This leads to two scenarios; in the first they wind up in an unbalanced state having shifted their CoG beyond their BoS or in the second case they have shifted their CoG within the BoS such that their initial strategy is no longer functional. In either case after the initial shock, the unexpected shift of their CoG triggers the cognitive OODA loop; they must now go through the Observe, Orient, Decide and Act cognitive loop stages before they can recover effectively. This creates a response lag on their part and gives us significant timing advantage. We can either continue to attack the OODA loop rendering them into a state of decision lock, or use the timing advantage to shape the situation and in the words of Jonh Boyd (father of OODA loop) "unleash a barrage of heinous acts upon our adversary" . In the direct attack we physically attack their balance and stability. With an understanding of the BoS and an ability to see or feel it we can attack it. Balance attacks can be subtle or quite direct, throws and sweeps are about as direct as you can get and more subtle approaches are any of the softer redirection techniques. In any case the person is unbalanced and either physically incapacitated through impact or joint destruction or the unbalance triggers the same OODA loop response giving us the cognitive and timing advantage. I will expand on this concept in almost every practical tutorial moving forward as it is my favorite concept; this is at the heart of every martial art which is size or strength independent.
