Walking is a good example of movement which is primarily pendulum like. If we attempt to describe the motion of a walker you might note that his arms and legs are primarily swinging back and forth. A characteristic of pendulous motion is that a mass is suspended at the end of a support which may swing freely. Whether this supporting member is free to bend, such as a string or rope, or not, such as a rod, does not really matter. The centrifugal force of the motion tends to keep the supporting member straight.
[This section needs reworking, it is wrong, especially when there is mass to the supporting members. This acts more like multiple pendulums] Since walking does create some bend in our elbows and knees, it is not a pure pendulous motion (for good reason, our pendulums need to "mesh" with the ground as we move forward.) But if one is going to attempt to maximize one's pendulous motion, a defining characteristic would be that while the joints in the supporting elements should be free to flex, they wouldn't. This means that if we were to observe a motion to determine if it were mostly pendulous, the supporting joints would not be flexing, but the actor would also NOT be using any tension to prevent these joints from flexing!
It should be noted that timing is an essential piece to using pendulous motion with a purpose. Timing is important for directional changes, it is efficient to let a pendulum come to its apex before trying to reverse its trajectory. It is also notable that a pendulum is moving fastest at the bottom when it is travelling parallel to the earth!
Obviously our use of pendulous motion is not limited to walking. Individual piece of our bodies which can hang from a rotating joint are each capable of acting like a pendulum! And any combination of these pieces is also capable of this type of motion. Being able to recognize this type of motion and when it would be beneficial to the task your are trying to achieve can be a strong advantage.
Benefits of Pendulous Motion
One of the benefits of pendulous motion is its ability to store energy. When a pendulum reaches its apex it has amassed potential energy! A pendulum can thus be held at its apex and released at any point without losing any energy. It can store potential energy indefinitely and easily convert that energy to kinetic energy later.
This type of pendulum potential energy storage is often used by anyone wielding long objects. Many weapons techniques start and end with the weapon held high. Baseball players do not wind up their bats in a horizontal circle around their shoulders, but rather they circle back and upwards! Starting with a bat high up allows the potential energy of the bat to readily be converted into kinetic energy and a forward swing, giving the batter a stronger strike than if he were to simply swing in the horizontal plane! Golfers use an even closer approximation to a pendulum since they tend to keep their club swinging in a single vertical plane. You will note that keeping your elbow unbent is a common guideline for a good golf swing, could this be an aknowledgement of the use of pendulous motion?
If we reverse this principle we quickly uncover another benefit of the pendulum. The pendulum can convert kinetic energy into potential energy! It is often desirable to move then stop and then begin moving again, a pendulum can help make this double transition efficient. Once we are moving we can convert our kinetic energy to potential energy using pendulous motion. This allows us to later reconvert that energy to kinetic energy without having to reinput this energy into the system. See if maybe you can even convert someone else's kinetic energy into your potential energy!
More Walking Analysis
Swinging our arms while walking serves the very important role of counter balancing our legs. This allows for good Relative Body Balance. But this arm swinging serves another very important purpose: the conservation of energy! Every step requires the reversal in direction of our limbs, instead of wasting all the kinetic energy in our limbs every time they come to a stop, through the pendulums of ur arms, it is converted into potential energy and then reconverted into kinetic energy swinging our arms in the opposite direction! What an incredible energy saving mechanism, without it we would get very tired and would not be able to walk nearly as far nor quite simply as fast.
Technical Note: While hardly martialy relevant this has implications for space walking. In zero gravity environments, a pendulum cannot operate. If we use some form of shoe which kept us stuck to the floor so that we could walk, we would probably still swing our arms to counter balance our legs, but we would not be able to reverse our arms' directions easily, gravity would not slow them down as they appoached level with our shoulders!
Training Pendulous Motion:
To better understand pendulous motion and our bodies it might be good to train with a small mass at the end of our arms. Also, would it help to suspend something beyond our hands, a bucket maybe? Swinging a pair of nunchaku or something simpler like a rope should effectively illustrate how to efficiently change a pendulum's direction.