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Simple tasks, such as reaching for a cup of coffee, are actually surprisingly complex, requiring the successful coordination of sensory input (seeing the cup of coffee, sensing one's own movement towards it, feeling one's fingers touch it, sensing its weight when moving it. etc.) and motor output (moving the eyes, extending one's arm, grasping the cup and lifting it, adjusting one's muscle tone to compensate for the added weight, etc.). Motor control are information processing related activities carried out by the central nervous system that organize the musculoskeletal system to create coordinated movements and skilled actions. Thus the study of motor control involves studying perception and cognition, feedback processes, and biomechanics, to name a few.

Motor control is also the name of a thriving field within Neuroscience that analyzes how people, animals and their nervous system controls movement.

Aspects of motor control
Motor control can be thought to concern two types of movements: volitional and reflexive.

Beyond anatomical divisions, motor coordination studies often seek to explore one of the following questions:


 * What physics and mathematical modeling of the limb movement may be involved?
 * How complicated and coordinated is the limb movement? How are movements of several joints coordinated?

Fortunately for researchers, multi-limb movements can often be modeled by simple mathematical models. A single limb can be broken down into components such as muscles, tendons, bones, and nerves. The physics are then derived with the aid of modern computers. The study of multi-limb movement is then only slightly more complicated. The development of elementary models of intelligence, along with a gambit of built-in reflexive reactions, is suited to the modeling of this system.

Theoretical frameworks of motor control

 * Coordination Dynamics framework emphasizes the dynamical and time-continuous interplay between brain, body, and environment as a holistic system.
 * Equilibrium point approaches emphasize that biomechanics and in particular the elastic properties of muscles and reflexes in the spinal cord can render many movement problems easy.
 * Reinforcement learning based approaches emphasize the learning of movement from motor errors.
 * Optimal control and estimation frameworks (see Bayesian brain) start from the computational problems that need to be solved and ask which solutions would be optimal. Many internal model studies fall into this framework.

Motor Units
Daily tasks, for instance walking to the bathroom, talking one of your friends or eating the dinner all require multiple muscles that innervate body parts to move properly in order to complete specific tasks. Motor units that consist tens, hundreds or even thousands of motor nerves branches are connected to the muscles. In our body, Rectus femoris contains approximately 1 million muscles fibers which are controlled by around 1000 of motor nerves. Within one motor units which can categorized to type I (slow twitch) or Type II fibers (fast twitch), the composition type of the muscle fiber will be consistent (homogeneous); whereas within one muscle, there will be several different combination of two types of motor units (heterogeneous).

There are three primary types of muscle fibers: Type I, Type IIa and Type IIb. As described above, Type I muscle fibers are known as slow twitch oxidative, Type IIa are fast twitch oxidative and Type IIb are  fast twitch glycolytic. These three different types of fibers are specialized to have unique funtionalities. Type I fibers are described as high endurance but low Force/Power/Speed production, Type IIb as low endurance but high Force/Power/Speed production and Type IIa fibers are characterized in between the two.

Motor units are multiple muscle fibers that are bundle together and when an athlete want to move their body to achieve a certain task, the brain then send out a instantaneously impulse signal that reach the specific motor unit through the [spinal cord]. After receiving the signal from the brain, the motor unit contract muscle fibers within the group for movement of the body. There are no partially firing in the motor unit which means that once the signal is detected, the muscles contract 100%. However, there are different intensity of activities involve in either daily tasks or athletes competitions that require just the right Force/Power/Speed provide from the muscle. Since the motor unit contracts its fiber 100% once stimulated, types of motor unit that generate variety of Force/Power/Speed are significant.

Fiber Type --   Contraction Speed  --  Time to Peak Power  --  Fatigue

I (slow twitch)---slow--100 millisecondsslowly

IIA (fast twitch)-fast-50 millisecondsfast

IIB (fast twitch)-very fast---25 millisecondsfast

Mechanism and Structure of motor unit
Low intensity task such as picking up a trash, the brain recruits motor units that group less number of muscle fibers which the muscle fibers are constructed by Type I(Slow twitch) meaning that even contracting at 100%, muscles will no create high Forces/Powers/Speeds performance. If Type II fibers are stimulated instead for low intensity task, a simple moment of picking up a trash will result in fast and powerful movement, knocking one's own face.


 *  low threshold motor units vs High threshold motor units
 *  The order of recruitment of motor unit
 *  Fiber versus nerves
 *  Muscle recruitment

Neural and Cognitive Processes

 * Forward Models
 * Skill development and motor learning
 * Sports-Specific decision making

Research in Athletes

 * Example from the Paper
 * Statistical results of significant difference
 * Different sports
 * Bar Graph and other figure of results

Suggested Reading
Shadmehr, R. (2004). The Computational Neurobiology of Reaching and Pointing: A Foundation for Motor Learning. MIT Press.