FUNDAMENTAL MOTOR CONTROL CONCEPTS
The way physical therapists appreciate human movement is increasingly influenced by concepts that come from motor control research.
An information processing approach to motor control, which views the human as a learning machine, gave rise to the idea that rules for movement execution are collected in motor programs
| Nicholai Bernstein, a Russian physiologist who whose work spans much of the early 20th century, but was translated into English only in 1967, proposed that the problem of controlling movement is too complex to be explicable in terms of motor programs. Where, Bernstein asks, could one store the amount of information needed to produce the variety of movement we see in everyday activities?
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His intellectual followers believe that humans solve "Bernstein's problem" by learning how the body's dynamics interrelate with the demands of movement tasks. Therapists must learn how the motor apparatus behaves in a gravitational environment, how, in Horak's (1991,p.13) terms, we adapt to and predict how physical laws govern the musculoskeletal system's interaction with the environment. Like puppet-masters, we exploit the movement-associated torques or interaction torques that bodies produce when they move. Therefore, we must understand the nervous system and the mechanics of the organs that are the nervous system's effectors.
Some try to understand motor programs and the variables they must control in Bernstein's terms. A family of equilibrium-point models takes this approach.
Others, like J.A.S. Kelso and Esther Thelen propose that humans move not by accessing programs, but by learning how to construct movement from the dynamic interaction between their bodies, the task, and the environment in which they move. They contend that movements "emerge" and "self-assemble" in the context of a task and environment, and they believe that we can best understand motor control from a dynamical systems perspective. While the theory can seem abstract, its principles permit us to develop a strategy for action. The theory's influence in physical therapy is growing, as evidenced in the professional literature that touches on it.
A dynamical system that is simple and undertandable yet capable of extremely complex behavior is a mathematical one, the logistic difference equation.
Although the dynamical systems approach is relatively new in physical therapy, other fields have found it useful for some time. Here at the University of Oklahoma,
Danko Nicolic, a graduate student in Department of Psychology, proposes that cognitive processes simultaneously employ dynamical and neural network features.
An independent line of thought that is becoming influential is that of "ecological psychology." Writers, beginning with James J. Gibson, have contributed to the solution of Bernstein's problem by arguing that the task and the environment provide a storehouse of information that structures human movement. The human brain need not store movement plans internally because much necessary information is available externally among environmental affordances.
References:
Horak, F.B. (1991). Assumptions underlying motor control for neurological rehabilitation. in Contemporary Management of Motor Control Problems, Proceedings of the II-STEP Conference. Alexandria, VA: Foundation for Physical Therapy.
Winstein, C., & Sullivan, K. (1996). Some comments on the motor learning / motor control distinction. commentary invited by the American Physical Therapy Association's Neurology Section. [On-line]. Available:
http://www.neuromus.org/xbaug96.html.