Jeet Kune Do. Teri Tom

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      The next term we need to define is the base of support. In sports biomechanics, this is the area on the ground defined by the athlete's point of contact. In our case, this would be the area determined by our foot position.¹⁹ If you were to draw a line from an object's center of gravity straight down to the ground, that line should fall within the base of support. We say the object is balanced. This is what we call the line of gravity. If, however, the line falls outside the base of support, we say the object is unbalanced.

      This is a fundamental element of all JKD techniques. One of the most common mistakes among students just learning to throw the straight lead is that they allow their center of gravity to overtake their base of support. They think that because it is a linear punch, they must throw their weight forward. This is partially true, but as we'll see in a subsequent chapter, this has more to do with hurtling your entire body weight forward via projectile motion. To maintain balance, though, you can never let your trunk overtake your feet. A good way to test this is to stop yourself after throwing a punch—it works for the cross, too—and look down at the floor. If you see that you're overlooking your knee, you're okay. But if you find yourself looking at a point on the floor that is in front of your knee, you're in trouble.

      The same is also true for defensive moves like the bob and weave. A lot of beginners start out by weaving too far to either side. Their trunks sway outside the base of support making the move awkward and unbalanced. You can use the same test for this. Weave to the left and stop. Look down. Are you looking straight down at your knee? If so, you're okay. If you're looking at a point to the left of your left knee, then you're unbalanced. Take it down a notch and minimize your movement.

      All JKD techniques require some transfer of weight from one point within the base of support to another. In throwing a hook punch, for example, we often start with more of our weight in the front foot, at the front of our support base, and then shift that weight to the back foot, at the back of the support base, creating a pulling action. You can generate a lot of force while keeping the line of gravity within the base of support.

      The real challenge of balance in JKD, though, is maintaining balance and stability over a constantly shifting base of support. From Commentaries on the Martial Way.

      "Movingproperly means carrying out the necessary movement without loss of balance. Until balance is regained, the boxer is ineffective in both attack and defense. Therefore in all movement, balance must be retained."²⁰

      Related to the idea of balance is the property of stability. As we mentioned earlier, this is the degree of resistance required to disturb one's balance. There are three variables that affect stability: the height of the object's center of gravity, the size of the base of support, and the object's weight. And, yes, there is an equation to represent this:

      Toppling force x moment arm of toppling force = object's weight x moment arm of object

      Technically, it's not the width of the base of support that determines stability. More accurately, it's the horizontal distance between the line of gravity and the edge of the base of support in the direction of the toppling force that determines stability.²¹ This is the moment arm of the object. The "toppling force" is the force required to unbalance the object. The moment arm of the toppling force is dependent on the object's center of gravity. The higher the object's center of gravity, the longer the moment arm is for toppling the object. Remember, a longer moment arm requires less force to produce torque. Therefore, the lower the object's center of gravity, the shorter the moment arm of the toppling force, and a greater force is required to unbalance the object.

      This is a pretty technical explanation of stability. What's important to know is that lowering your center of gravity and widening the base of support usually result in greater stability.

      So we've already established that widening the base of support, or in our case, widening the JKD stance, increases stability. But remember Bruce's quote about "movement without loss of balance." Movement. In JKD, your base of support is constantly shifting. As we'll see in the next chapter, the JKD stance is designed to strike a balance between stability and mobility. The wider your stance the more stable and less mobile you'll be. A narrower stance means less stability but more mobility. There is always a trade-off between the two.

      In certain situations, you'll want to lower your center of gravity and widen your base of support. In close quarters, for example, when you duck, you widen your stance and lower yourself to the ground. Not only does this get you out of harm's way, but you've also hunkered down so that follow up blows are less likely to knock you over. Similarly, if a grappler shoots in to throw you, you'll go into a wrestler's crouch. Again, this widens your stance and lowers your center of gravity. In this position it will take a lot more force to topple you.

      Widening the base of support, though, is not just for defensive maneuvers. As we'll see in the next section, whenever you apply a force, an equal and opposite force comes back at you. The more stable your stance, the less likely you'll be thrown off balance by the opposing reaction force.²² Examples of widening the base of support to apply force can be found in almost all sports. When a pitcher throws a ball, he takes that giant step after the wind up just before releasing the ball. If he didn't, he wouldn't be able to apply as much force to the ball without being thrown off balance. Try hitting a heavy bag while standing on one foot. That's a pretty narrow base of support. You're likely to be knocked off balance. Now stand in a regular stance and hit the bag. You've widened the base of support and can absorb the opposing force of the bag while maintaining stability.

      NEWTON'S THIRD LAW OF MOTION: MINIMIZING WEAR AND TEAR

      In our analysis of stability, we've just introduced the concept of action and reaction. This is more formally known as Newton's Third Law of Motion, which states:

      "To every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal and directed to contrary parts."²³

      Going back to our heavy bag example, remember how a СКАЧАТЬ