The objective of this project is to create a robust anatomical/biomechanical model of a particular multi-joint system (the human elbow and wrist) based on the attachment sites of all of the relevant muscles and ligaments that will determine the individual contribution of each muscle to total joint torques. This model will then be used to examine possible strategies for muscle activation that would allow the limb system to maintain a static posture under various load conditions and joint angles. The acceptable strategies will form a solution space, and examination of this space will reveal possible neural control algorithms. The model will then be compared with actual EMG data collected during static postures as described by loads measured in three degrees-of-freedom. From these data, the solution chosen by the nervous system will be compared with the solution space described by the model. How this particular solution set changes under different load conditions and joint angles should expose the nature of the neural control strategy used to maintain these postures. In particular, this information will be important to describe the way single-joint muscles at one joint, which have no mechanical action at another joint, are nevertheless modulated during tasks at a distant joint. Such modulations imply a complex control strategy for determining muscle action. The model will also be useful for examining control theories proposed by other investigators, such as optimization techniques, brain tensor network theory, and neural network solutions. None of these have been tested with the dual criteria of a robust anatomical model and well-controlled EMG evidence, and this procedure should be useful for examining the validity of these theories. Finally, the plasticity of the solution sets will be examined by a series of experiments including fatigue, biofeedback, electrical stimulation, and/or anesthetization. Besides serving as a test of the validity of neural control theories, careful examination of the plasticity of the system will be a means of examining the underlying neurophysiology. For example, if reflex coupling (afferent feedback) is used, then synergies should be altered by changes in sensory feedback which could be examined through anesthetization. With adaptive modification (cerebellar or otherwise), the plasticity experiment should reveal that subjects go through a learning period with the muscle force/EMG alterations, as opposed to an instantaneous correction that would be expected with afferent feedback. Exploration of the strategies used by the nervous system to control limb postures lies at the foundation of motor control physiology. This work is potentially beneficial to the understanding of motor control disorders such as spasticity resulting from cerebral palsy, Parkinson's disease, or stroke. The result of these disorders can be explained in terms of inappropriate control strategies. Once a method is developed for characterizing motor control strategies, it could be applied to both the study and quantification of a host of disorders.
| Delp, S L; Grierson, A E; Buchanan, T S (1996) Maximum isometric moments generated by the wrist muscles in flexion-extension and radial-ulnar deviation. J Biomech 29:1371-5 |
| Buchanan, T S; Lloyd, D G (1995) Muscle activity is different for humans performing static tasks which require force control and position control. Neurosci Lett 194:61-4 |
| Beckman, S M; Buchanan, T S (1995) Ankle inversion injury and hypermobility: effect on hip and ankle muscle electromyography onset latency. Arch Phys Med Rehabil 76:1138-43 |
| Buchanan, T S (1995) Evidence that maximum muscle stress is not a constant: differences in specific tension in elbow flexors and extensors. Med Eng Phys 17:529-36 |
| Murray, W M; Delp, S L; Buchanan, T S (1995) Variation of muscle moment arms with elbow and forearm position. J Biomech 28:513-25 |
