Hard to see, the dark side is.

Week 9: Movement

Observing Motion

When people move, we "know" when someone looks awkward, but do we know what factors contribute to our perceptions? To understand human motion, let's look at our mechanical system. Learning a movement or task involves forming some concept of how it should look and feel (cognitive part), practicing it and integrating past experiences into the new task.

Our bodies with respect to movement are a series of levers which are supported by their articular structures, musculature and connective tissue. The larger muscle usually act as prime moveers, whereas the smaller muscles often are responsible for finer control. All of this is controlled by the nervous system, which relies on sensory feedback as well as memory and cognition to control motor responses.

Even tasks that seemingly involve just the upper body utilize the larger muscles in the legs for impetus or support. When you want to throw a ball really far, you would take a wide stance, with your weight back on your throwing-arm side. The throw would actually be initated by your back leg, and the motion would be continued through to your upper body segments. The distance the ball travels would depend on its velocity when released from your hand. This velocity would be determined by the the amount of momentum you would be able to transfer to the ball, a figure represented by the following equation:

Force Applied x Time Applied = Object Mass x Object Velocity

The second half of the equation represents the object's momentum. If you look at the larger picture, which includes the momentum of the whole system, (your body PLUS the ball), you could also look at efficiency in terms of how well the system's momentum is maintained. If the ball's momentum at release is fairly close to the system's momentum just prior to release, the momentum transfer is said to be efficient.