Central Pattern Generators and Athlete Training
How does a gymnast train his or herself to perform the impossible feats that most of us can’t even imagine doing? Shawn Johnson is a 17-year-old female and not much different than myself in terms of body shape and age. However, there is no way I can even begin to complete the skills within Shawn’s ability:
What makes me different from this young gymnast? The difference is in our training and in the way our brains our wired. Sports involve the correct coordination of body parts and the incredible ability to develop multiple central pattern generators and exploiting the body’s natural structures for specific skills that would otherwise be considered outside the ability of the human body. Athletes such as Shawn have to be able to be in complete control of their bodies and minds in relation to their sport at all times. Central pattern generators are produced by a group of motor neurons working together to create a specific coordinated movement such as walking, running, playing soccer, and swimming. In order to execute their particular sport, athletes have to be able to not only create these pattern generators for their skills, but also easily access them. Sensory input is required to get these generators started.
During athletic events, the body has to manipulate the body’s normal functions in order to get their desired result. This involves changes in body posture and shape while also working to cause changes in the body’s normal physics such as elasticity, gravity, and friction (2). Neuromodulators are chemical agents that modulate a neuron’s response to neurotransmitters in the central nervous system. They are constantly overlooking pattern generators and controlling their frequencies (2).
Most pattern generators have a preferred frequency that can only be controlled by training the pattern generator to speed up. For example, running is controlled by a central pattern generator; therefore a person should technically be only able to run at one particular speed. This however, as many Olympic sprinters will tell you, is not the case. There must be some way for CPGs to speed up their preferred frequency. Research has shown that VI neurons have the ability to shape the motor outputs that occur during movement. These neurons have been shown to be required for generating ‘fast’ motor bursting (6).
Can the manipulation of CPG frequencies occur by the firing of specific neurons? Some studies have shown that locomotive CPGs can be modulated by the neurotransmitter serotonin (5), levels which can be raised with increased exercise (4) It is possible that high levels of exercise and running practice allow the athlete to continuously manipulate their CPGs and cause their frequencies to increase, permitting the athlete to run faster.
Athletes have very fine-tuned gross and fine motor controls, allowing them to execute specific muscle and body movements. The voluntary motor system allows for motor control and is a part of the somatic nervous system (1). Certain activities can help to increase motor control, such as the repetition of a certain activity. Continuous yoga, for example has been shown to increase coordination and improve concentration (3). This repetition and increase in motor control must somehow be connected to central pattern generators and the manipulation of them. A gymnast (or any other athlete really) creates central pattern generators for the skills required for their routine, and these are reinforced by repetition and muscle memory gain.
One paper showed that rhythmic motions of a person’s index fingers could generate a similar pattern with leg movement, also called associated reactions (8). They showed that it was possible for a voluntary action to cause reactions in other parts of the body. In this way, voluntary movements of one extremity could cause the coordination of limbs. This process may facilitate the actions of athletes. In gymnastics, both the arms and legs must work together in a rhythmic motion. It seems as though the coupled movement of both arms and legs works together to create a central pattern generator. This could explain how gymnasts create the pattern generators for their skills. Although these synergies are usually seen to disrupt the manipulations that are necessary for athletic performance, they may work together with exploitations in sports (such as gymnastics) and allow all of the body to be active in this one generated central pattern generator.
From looking into the body and specific movements, it seems as though it is not possible for one motor specific unit to control athletic skills. Rather it is the coordination of central pattern generators, motor neurons, muscle memory, practice, and genetics that make a gymnast able to control their body movements. However, further research into this subject may show more connection between these units of the body than has previously been proposed. So, to answer my original question, I am very different from Shawn because I have put in the hours necessary to create the connections needed for her skills. Gymnasts and other athletes spend hours developing motor patterns, neural connections, muscle memory, motor patterns, and pattern generators. Without this dedication and intense neurobiology, these incredible athletic feats would be impossible.
(1)"Motor Control - Injuries, Training, Anatomy, Muscle - World of Sports Science." Internet FAQ Archives - Online Education. Web. Mar. 2010. <http://www.faqs.org/sports-science/Mo-Pl/Motor-Control.html>.
(2) Pitti, Alexandre, Ryuma Niiyama, and Yasuo Kuniyoshi. "Creating and Modulating Rhythms by Controlling the Physics of the Body." Springer Science and Business Media 28 (2010): 317-29. Web of Science. Web.
(3) S, Telles. "Plasticity of Motor Control Systems Demonstrated by Yoga Training." Indian Journal of Physiology and Pharmacology 38.2 (1994): 143-44. PubMed. Web.
(4) "Serotonin and Its Uses." Serendip's Exchange. 1999. Web. Mar. 2010. <http://serendip.brynmawr.edu/bb/neuro/neuro99/web1/Byrd.html>.
(5) "Serotonin Modulates the Central Pattern Generator for Locomotion in the Isolated Lamprey Spinal Cord -- Harris-Warrick and Cohen 116 (1): 27 -- Journal of Experimental Biology." The Company of Biologists Ltd: The Journal of Experimental Biology. Web. Apr. 2010. <http://jeb.biologists.org/cgi/reprint/116/1/27>.
(6) "V1 Spinal Neurons Regulate the Speed of Vertebrate Locomotor Outputs : Abstract : Nature." Nature Publishing Group : Science Journals, Jobs, and Information. Web. Mar. 2010. <http://www.nature.com/nature/journal/v440/n7081/abs/nature04545.html>.
(7) "Webvision: Visual Cortex." Webvision Home Page. Web. Mar. 2010. <http://webvision.med.utah.edu/VisualCortex.html>.
(8) Yom-Tov, E., S. Yom-Tov, and H. Ur. "A Model of Induced Coupled Movements in the Human Body: A Case Study." Biological Cybernetics 80 (1999): 411-16. Web of Science. Web.