mo·men·tum

noun | mō-ˈmen-təm
1. the quantity of motion of a moving body, measured as a product of its mass and velocity.

You study WingChun, not physics, so why care about momentum? One goal in WingChun is maximizing the projection of our physical power. That increases your destructive effect, which is valuable for you to rapidly end a self-defense encounter. As the study of matter, energy and their interaction, physics is relevant to this objective. Remember, physics is not abstract but emerges from the observation of reality. Momentum is the aspect of physics that describes the quantity of motion an object has.

Of course, you have to repeat WingChun movements many thousands of times towards proficiency. But knowledge of momentum will help you do so with better results sooner. It is theory that will benefit your practice by understanding what variables to adjust, whereas WingChun shows you how. You might even say WingChun is physics in action.

1. Defintion

So let’s start with a definition of momentum. Momentum is the relationship of mass to velocity. In fact, you can calculate momentum (p) by multiplying (•) mass (m) with velocity (v):

p = m • v

This is a useful idea. It tells us that mass and velocity are equal contributors to momentum. We know that momentum is zero without velocity. If you incorporate more mass, your momentum increases. In short, to maximize momentum you must maximize mass and maximize velocity.

2. Measurement

Mass is measured in kilograms (kg). Velocity is measured in meters per second (m/s). For instance, the momentum (p) of a 100 kg body that moves 2 meters per second is 200 kg • m/s:

p = 100 kg • 2 m/s = 200 kg • m/s

A body half the mass (50 kg) must move at twice the velocity (4 m/s) to equal this momentum:

p = 50 kg • 4 m/s = 200 kg • m/s

One more thing to consider is that momentum is a vector. A vector has both magnitude and direction. Thus, to fully grasp and apply the concept of momentum in WingChun we have to discuss mass, velocity and direction.

3. Mass

As stated above, you must maximize mass to maximize momentum. For WingChun, that means the mass of your whole body. Whether, your body mass is 40 kg or 90 kg, every bone, muscle, organ need to be mobilized. Using the mass of your arms or legs will not create as much momentum as integrating limbs and torso together.

Thus, we emphasize technical correctness in WingChun instruction. It is not for aesthetics but alignment to coordinate the structure and function of your body as a single unit. If your arms move earlier or later than your legs, you lose effective mass. The same is true if your spine is lax or askew. Every part of your body must be properly involved in at the moment of impact. This is internally trained during Form and externally tested with Applications. Exercises like Lat Sao (甩手 Casting Arms), Chi Sao (黐手 Adhering Arms), Guo Sao (過手 Passing Arms) and Puen Sao (盤手 Coiling Arms) bridge the two.

4. Velocity

Velocity actually has three elements: distance, time and direction. I will elaborate each of them separately in the next sections. How does distance and time relate to WingChun? Since, in the momentum equation, velocity is expressed as the fraction “meters per second (m/s)” with distance in the numerator (top of fraction) and time in the denominator (bottom of fraction), you want to make distance large and time small to maximize momentum.

4. 1. Distance

If you are punching an opponent then distance is how far your fist is from the target. You could also define distance is the length of your step required to bring your into optimal striking range. In a straightforward situation such as Tsong Kuen (衝拳 Thrusting Punch) with Dap Bo (踏步 Striding Step), this distance is fairly constant. For me, it is about 20 centimeters (cm) or 8 inches (in).

Obviously, this varies if I use other footwork like Che Gok Bo (斜角步 Slant Angling Step) or Soeng Bo (上步 Advancing Step). Those steps may cause my position to change by 2-3 feet (ft) or 60-90 cm. But the point is that distance is a fairly fixed quantity depending on which technique you choose to attack a given target. After you train a while, you can keenly feel the precise distance from a target at which any WingChun technique (or combination of techniques) is optimally launched.

4. 2. Time

Time is easy. You want to minimize it. When you are at right distance as explained above, you contract the relevant muscles as quickly as possible. Usually, that means a fast flexion followed by a fast extension of the bones in your arms (mainly humerus, ulna and radius) and legs (mainly femur, tibia and fibula) and their intervening joints (shoulders, elbows, hips and knees).

In WingChun, most techniques require flexion during their preparation phase and extension during their execution phase. For example, when teaching Tsong Kuen, I call this out as “Pre-Tsong” and “Tsong”, respectively. Hence, if you take one second for Pre-Tsong and one second for Tsong, then the total time is 2 seconds. Through training, if you are able to shorten the time to half a second per phase then you only need to 1 second to complete Tsong Kuen. In effect, this halving of time will double your momentum. Later on, you will not be able to so dramatically lower your time, but even shaving off milliseconds is good.

4. 3. Direction

Velocity is a vector quality, which is defined by magnitude and direction. Speed is a scalar quality, which is defined by magnitude only. Since, momentum is proportional to velocity, it requires a description of direction.

This is essential to WingChun efficacy as well. Actually, it is the first thing to define when applying WingChun for self-defense. Where is the opponent? 45 degrees to my left. What target do I want to strike? I choose his trachea. These two questions define direction and therefore the vector of our velocity. To go one step further, the vector of, say, our Tsong Kuen must not graze to the either side of the throat, but penetrate through it. If your striking vector is off by even 5 degrees, it will not fully stop the opponent. In other words, you must train again and again and again until, ideally, one perfectly aimed Tsong Kuen is enough.

5. Conclusion

Momentum is not mere academic fluff but physical fact. You can see it in action all day. You feel it when your car abruptly stops. You notice it when someone bumps into you. By relating your mass to your velocity, momentum is a reminder to practice WingChun consciously. Here is a three-step summary for the maximum momentum of WingChun movement:

1. Move Right: Correct positioning, distancing and targeting
2. Move Whole: Utilize your entire mass, to the last ounce.
3. Move Fast: Don’t hesitate but go all out when necessary.