The Nervous System and How It Applies To Training
As you all may know, or at least I hope you know, the body contains different systems that operate in conjunction with other systems and also act independently from other systems. These systems include the circulatory system, the nervous system, the skeletal system, the muscular system, the respiratory system and so on. The thing you may not know is that the muscular system is not the only thing responsible for those awesome muscles that you are trying to grow and develop. Muscles are actually directly affected and innervated by the nervous system, the peripheral nervous system to be exact. To discuss how muscular gains are dependent on the nervous system, it will first be beneficial to discuss the basic components of the nervous system that are directly related to the muscle itself.
The nervous system itself is comprised of two parts, the peripheral and central systems with the central part being the brain and spinal cord and peripheral being all nerves outside of that. The peripheral nervous system is the part that is directly active at the site of the muscles, this is known as the somatic motor function within the peripheral nervous system. As you can already see the terminology can get very specific and also the processes are very intricate. For that reason, I will dumb things down a bit and pull out the necessities instead of boring you with physiology jargon. Nerves basically consist of neurons (cells of the nervous system) that come together to form tracks of communication from brain to body and body to brain. Motor neurons are the cells that cause movement. A motor neuron and all of the muscle fibers that it innervates is called a motor unit. The neuromuscular junction is essentially where the nerve cell meets the muscle cell and chemicals signals between the two are transmitted. With increased amounts of motor units responsible for a movement this indicates a tedious and fine tuned muscle movement as opposed to less motor units being a simpler movement. The eyes and hands are innervated by large amounts of motor units where as the biceps not so much. However, it is important to note that just because there are less motor units this does not mean that the movement is not as powerful.
The nervous system is actually responsible for those wild increases in strength gains at the onset of exercise and by this onset I mean for those who have just begun to weight lift. This is due to the nervous system's and musculoskeletal system's efficiency to convey signals to and from each other. Upon writing this article I began to realize there are many more ways than just one that you muscle gains are benefited by actions of the nervous system as a whole. So in this article I will only discuss a few of, what I consider to be the coolest and most important aspects of the nervous system that contribute to muscular gains.
Besides the physiological interaction of the muscle fiber and the neuron at the neuromuscular junction the biggest benefit, I would say, that comes from the nervous system is the concept of stretch. Stretch is part of the nervous system, what? Yes! There are these little stinkers called golgi tendon organs and muscle spindles within the muscle fiber itself that detect muscular tension and rate of muscular stretch, respectively. Even though they are located inside the muscle they are directly a part of the nervous system and relay information to the brain. The muscle spindle can be seen in action in the weight room by the following example. I don't recommend you do this but just be imaginative with the example. If you are holding a 10 lb plate in your hands with the arms at a 90 degree angle and then your workout partner puts an additional 25lb plate in you hands (for the scenario's purposes you will not drop the weight) your muscles adapt and you can still hold both plates. Your muscle spindles detect the additional stretch that the muscle is experiencing at such a rate and calls on additional motor units to be activated.
The propriocepters (muscle spindles and golgi tendon organs) are in place as a sort of protective mechanism for the body. By sensing stretch and rapid stretch the proprioceptors can induce a reflex that causes the muscle antagonistic muscle that is being worked to contract, thus pulling your hand away from the hot stove-top so to speak. Golgi tendon organs in this way are possibly more responsible than muscle spindles for your increases in muscular strength. Golgi tendon organs produce inhibitory responses in response to tension produced. That is when they feel they are experiencing too much tension produced by muscular contraction (weightlifting) they produce inhibitory responses to the contraction. However, you can "manual override" these inhibitory responses with your own brain! The best example I can give is that of when performing a stiff-legged deadlift or a Romanian deadlift. When at the bottom of the movement the hamstrings are experiencing extreme stretching. For a newbie, this exercise poses a problem because the reflex produced by their golgi tendon organs is going to cause them to fall either over, instinctively drop the weight or step forward with one foot. However, for the more experienced weight lifter you are manually overriding the reflex signal that the golgi tendon organ is sending to your brain and you continue to contract the muscle. By actively stretching within each exercise you perform, which is done by the optimal range of motion of the exercise, you can reduce these inhibitory responses thus allowing you to potentially life more weight! Awesome!
So, make sure you are stretching and my stretching I mean properly performing the exercise in the range of motion that is intended for the exercise. Short range of motion not only robs you of the long eccentric contraction within the movement but also robs the muscle of the stretch that it needs to overcome the inhibitory reactions produced by the propriocepters.
Picture from:
http://www.70sbig.com/blog/2011/06/the-rdl/
The Oxford Dictionary of Sports Science & Medicine, by Michael Kent, Oxford University Press
http://www.drrichardstein.com/t2/document/1zone_healing
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