How can we move easily, comfortably, and without pain as we age? Of course, common sense tells us that we need to exercise regularly to make sure all the working parts keep working. But what is going on in our bodies at the cellular level? Aging gracefully may, in part, come down to our motor units. The information herein is based on an article written by Holly Sweeney, Director of the Montclair, New Jersey, Yang Cheng Fu Center, entitled “Looking Through the Lens of Science at the Ten Essentials of Tai Chi Chuan.” Her article was published in the Spring 2005 issue of the International Yang Family Tai Chi Chuan Association newsletter.
I hope to adequately summarize her very in-depth article of how these motor units work, and how we can use them wisely. A motor unit is one nerve cell (neuron) and all the muscle fibers which it activates. A group of motor units represent a muscle. When we move, or tell our bodies to move, we in effect are calling our motor units to action. By calling on our motor units, the nerves become excited and the connected muscle fibers are activated.
Okay, so what does this mean? When the motor units are not called into action, they don’t do much. But when they are, they sort of have this “all out war” attitude. They are basically either turned completely on, or turned completely off. In some situations, you may want this pedal-to-the-metal force. It’s great when short bursts of energy and power are needed, like sprinting. But what about endurance? What about long distance running?
How does our body sustain a movement? There are a couple ways to do this. You can send a continuous barrage of nerve impulses to the motor units to keep all the muscle fibers strong and activated, thus preventing them from weakening in between impulses. This is great for activities like sprinting or playing tennis. The only downside is that the muscle fibers eventually will get tired and you will have to rest before you can attempt the activity again.
Another way to sustain a movement is to change motor units that are activated at any given time. You make some motor units work while letting others take a break. We can accomplish this method with smooth, continuous movements. And the benefit of this method? Over time, our bodies end up activating and maintaining way more motor units then the other way of slam-dunking all the nerve impulses at once.
More motor units equal more strength and balance. And aside from being great for conditioning the body, ample amounts of motor units help us to age gracefully, too. With the normal aging process, cells die. And when motor unit nerve cells die, all the muscle fibers connected to them become useless. If those fibers do not reconnect with a new motor unit, they will atrophy. So what makes them want to reconnect? It all boils down to that old adage, “Use it or lose it.” New motor units will be created only if your body plans to use them.
So get off the couch and go build some motor units, for goodness sake!