We should always move the body as a unit, right? Just search google for the term and you will find countless articles discussing the increased power gained from "moving as a unit". Let's be clear though....
The words we choose as teachers must be specific. The phrase doesn't communicate the full principle to the student. In fact, it communicates just the opposite.
The body is not one unit. Rather, the body is a series of segments / bones, looseley connected by tendons and muscle tissue. If we moved as a unit we wouldn't move at all. Take walking for example. We swing our leg forward from the hip, then the thigh, and finally the foot. Three distinct segements of movement requiring us to fire different muscles at different times.
Power does not come from moving as a unit. Contrary to most of the articles written on the topic, power comes from doing exactly the opposite. It comes from moving in segments. Power generation requires you to fire various muscles, in a specific order, to propel different segments of your body at different speeds that add up to one final strike. Put another way... each segment contributes speed (part of power) to the final strike. In Sport Science it's called Kinetic Chaining. The concept is not a new one. The term was created in 1875 by a Franz Reuleaux, a mechanical engineer, and later adapted for human movement by Dr. Arthur Steindler in 1955.
So why don't we see it more often? Primarily because it's very difficult to measure power contribution for each link in the chain for materials that behave unpredictably. How much does the leg contribute? The mind? Nutrition? Relaxation? The problem gets complicated quickly.
Power generation requires you to fire various muscles, in a specific order, to propell different segements of your body at different speeds that add up to one final strike.
Nonetheless studies, such as this one on high speed throwing are being done to quantify what can be. In a nutshell they were able to isolate and measure the contribution of power for each link in the chain. From torso / core, to shoulder, to elbow, to wrist, which one contributes the most power? It turns out that torso and shoulder are the largest contributors. They help to store elastic energy in the elbow and wrist. That stored energy is part of a proper kinetic chain movement that leads to a faster throwing speed (or in our case, a strike). This matters to those of us in the martial arts because....
You can't store elastic energy if you move as a unit.
For example, a straight rod is a unit, where a chain would be a series of segments. When you pick up a rod and swing it the entire rod moves at once, right? You're not building elastic energy in this case. However, if you pick up a chain the opposite end doesn't move until all the prior segments move. If you whip the chain, each segement will yank the others, which will follow and increase elastic energy as more and more segments are added.
Your body in motion is the chain.
If you haven't read my article that touches on the components of power generation, please take a look. In brief, power comes from the MATS (Movement, Alignment, Torque, and Speed). Kinetic chaining contributes to the Speed element of power generation and uses Torque to assist. You want to move the pieces of the body closest to the core first then work your way outward with each segment picking up speed as you go.
Note that I wrote "in motion". While moving you should be the chain, but...
What about on impact?
The human body is an amazingly adaptive machine. It can go from being loose to stiff in fractions of a second. In essence it can act as a chain and a rod. The beauty of this is that you can move as a chain and upon impact fire your muscles to strike as a rod. You get all the speed of the chain and the stiffness of the rod.
Ok, so we get why moving as a chain is good for increasing Speed, one of the components of power. But what are the benefits of stiffening up on impact?
If I threw a ball at your chest it would hurt more or less depending on the balls Speed. But if that ball were stiffly attached to a solid object it would hurt a lot more, right? Remember the acronym for power generation MATS? The "A" stands for Alignment. At the moment of impact you want to have as much Speed as possible and be as Aligned as possible. The good news is that you have the choice to fire your muscles, stiffen your skeleton, and Align your body at that moment. You can choose when and how much alignement you want to contribute to the final strike. That's what makes power generation so complex. It requires you to move from relaxation to stiffness with precision timing.
At the moment of impact you want to have as much Speed as possible and be as Aligned as possible
Perhaps the intent of the phrase "move as a unit" was to convey this principle, but the words just don't match. A better phrase would be...
I cannot emphasize enough how important it is to convey this principle to your students. Using the terminology that aligns with actions or concrete concepts will always speed up the learning process. As teachers we should all do our best to find the right phrases to communicate.
How do I put this principle to use?
The scope of this article is to present the principle. Later articles and videos will cover specific drills and exercises to increase torque, speed, and your ability to remain loose. In the meantime I suggest beginning with increasing thoracic, shoulder, and hip mobility. Improving just one of these will increase your relaxation during training and, as another benfit, your overall health.