Jeet Kune Do. Teri Tom
reasons for why these techniques work. I've done so in the hope that you will be able to someday place yourself at the mercy of inspiration.
CHAPTER ONE
BIOMECHANICS 101
This isn't a biomechanics textbook, and it's beyond the scope of this volume to go into the finer details of that science, but an understanding of some basic principles will give you a much better understanding of Jeet Kune Do. On so many fronts, Bruce Lee was light years ahead of his time, and this arena is no exception. Breaking down professional sports to a science may be commonplace these days, but in Lee's time, that kind of analysis was only just beginning. While he may have surveyed many other arts, what he chose to incorporate into his own repertoire was very specific and considered, resulting in an art essentially limited to 4 or 5 punches, 3 or 4 kicks, and a few grappling techniques.
We'll touch on some of the strategic elements later on, but first, we must learn to perform them correctly. And what will help you refine these techniques to perfection is a basic understanding of why Bruce Lee chose to do things a certain way. A lot of people neglect this aspect of the art and move on to application. But failing to build a strong technical foundation is like trying to drive without learning how to put the key in the ignition. It makes no sense, and you'll end up going nowhere. Sloppy technique makes for sloppy application.
It may seem like splitting hairs to break these tools down to a science, but in any sport, knowing how to refine your skills will give you a competitive edge that could make all the difference. For sprinters, a millisecond means victory or defeat. The martial arts should be no different. Honing your skills will result in more speed, more power, and more successful application of those skills. While it's true the number of fast twitch muscle fibers you have is genetically predetermined, you can level the playing field somewhat and do the best with what you've got by refining your technique.
Also if you're in this for the long haul, knowing the basics of biomechanics can save your body a lot of wear and tear. Proper technique and knowledge of what makes those techniques sound can increase your longevity. I always look to Ted Wong as a great example of this. He's honed these skills for over thirty years. As of this writing, he's 70 years old and while almost all of his contemporaries have fallen by the wayside or declined markedly in their performance, he still spars with blokes less than half his age and complains of few aches and pains. He'll tell you that when he first started, before he'd refined his technique, how his body hurt so much he seriously contemplated quitting the martial arts altogether. He also hits a lot harder than he did in the 1960's. If you compare footage of him then and now, you'll see that he can attribute this longevity to analysis and improvement of his skills over the years.
So how do we go about refining technique? The first step is to know why a specific technique is performed the way it is. In this book, we are going to show you why a Bruce Lee punch or kick was so effective. True, the man was born with some serious fast-twitch muscle fibers. But he was also relentless in the refinement of his technique.
Before we can fully describe each technique, though, we need to know some basic principles of biomechanics. We'll briefly explain some of these laws and then we'll see how they apply to all JKD techniques. Later, as we discuss the specifics of each technique, you may want to refer back to this section.
BIOMECHANICS AND FORCE
The term biomechanics basically is the science of forces and how they affect humans. A force is either a push or a pull that can act externally on an object in the environment (i.e. throwing a punch on a heavy bag is a pushing force on the bag) or internally within a system or object (i.e. muscles create pulling forces around joints causing movement of your limbs).
TYPES OF MOTION
Motion or movement may be defined as a change in position. There are three kinds of motion. Linear motion is defined as having all points on a body or object move the same distance in the same direction and at the same time. Simply put for our purposes, this is movement in a straight line. For example, jumping up and down is linear. The trajectory of a straight punch is linear. On the other hand, the trajectory of a hook is circular (Figures 1.1-1.3). This is called angular motion and occurs when all points on a body or object move about the same axis.1 Finally, we have general motion, which is a combination of both linear and angular motion. Most human movement falls under this category, and in fact, all of our JKD techniques combine elements of both. All JKD kicks and punches include linear vertical, linear horizontal, and angular components.
FORCE PRODUCTION
In layman's terms, velocity and speed are interchangeable. It is important to note, however, that speed is merely distance traveled over time. Velocity is a measure of both speed and direction and is represented in physics studies as a vector quantity. Vector quantities are drawn as arrows and show you two things—how fast and in what direction. The length of the arrow represents speed—for example, 1 centimeter might represent 20 km/hr. And direction of the arrow represents direction of the object. If an object is moving in two directions, you can draw a triangle and find the sum of the two vectors by solving for what we call the resultant using the parallelogram rule.
Velocity is important because a change in direction and/or speed is called acceleration and in force production, acceleration is the name of the game. In most sports, success depends on generating the most acceleration before applying force to another object. In tennis, the object of service technique is to generate maximum acceleration of the racquet head at impact. In the baseball or golf swing, again, the object is to maximize acceleration of the bat or club when you strike the ball. The same goes for throwing punches. The object is not only to move your fist or foot at a high velocity, but to have that velocity maximally increase at the point of impact. This is known as Newton's Second Law of Motion which states that the acceleration produced by a net force on a body is directly proportional to the magnitude of the net force, is in the same direction as the net force, and is inversely proportional to the mass of the body.2 In mathematical terms, it is expressed as:
Force = mass x acceleration
From the equation, we see that force production increases with acceleration. We also see that an increase in mass of the object that is accelerating also increases force. This is central to all the techniques that comprise JKD, which I affectionately call "the art of how to best throw your weight around." For every punch and every kick, you should be asking yourself how you can get as much of your body weight into the technique without compromising balance and mobility.
In the following chapters, we'll explain what Bruce Lee believed to be the best ways to maximize acceleration and body weight into each technique. We'll explain how a 135-pound Bruce Lee could generate such incredible power. Bruce himself wrote in the Tao:
"The principle is to preserve the maximum acceleration up to the last instant of contact. Regardless of distance, the final phase of a movement should be the fastest."3
IMPULSE AND SNAPPINESS
Related to the equation for Newton's Second Law is an equation that accounts for a change in velocity—and in the case of throwing punches, a change in direction. Momentum is defined as the following equation:
Momentum = mass x velocity
To change an object's momentum, the velocity must change as well. When you throw a punch, the punch does not continue forever in the same direction unless you're Mr. Fantastic. No, you have to retract your hand at some point. This requires a change in direction. For straight punches, this means throwing the punch straight out, hitting the target, and then bringing the hand back to the on-guard position. We've already established that force is a product of mass and acceleration. But there's another