A Dynamic Optimization Solution for Vertical Jumping in Three Dimensions

An efficient simulation method for discrete-value controlled large-scale neuromyoskeletal system models

An efficient Euler-Adams hybrid integration scheme for simulating on the computer discrete-value controlled large-scale neuromyoskeletal system models is presented. If, as discussed in the model, the differential equations describing the recruitment and excitation dynamics of the muscular subsystem are independent of the corresponding contraction-dynamical state variables, they can be integrated separately over certain time intervals by a modified Euler routine that handles discontinuous right-hand sides efficiently. The resulting myostates can then be stored and used as continuous input values for the subsequent integration by an Adams predictor-corrector algorithm of the remaining contraction-dynamical and skeletomechanical state differential equations. With such an Euler-Adams hybrid integration routine one avoids the detrimental effects and efficiency losses associated with frequent stop-restart cycles of otherwise efficient Adams-type algorithms, which cycles are forced by discontinuities on the right-hand side of the myostate equations. In the example presented, a reduction in the execution time by a factor of about 5 could be achieved by implementing the proposed technique.

Dynamic simulation of human movement using large-scale models of the body

A three-dimensional model of the body was used to simulate two different motor tasks: vertical jumping and normal walking on level ground. The pattern of muscle excitations, body motions, and ground-reaction forces for each task were calculated using dynamic optimization theory. For jumping, the performance criterion was to maximize the height reached by the center of mass of the body; for walking, the measure of performance was metabolic energy consumed per meter walked. Quantitative comparisons of the simulation results with experimental data obtained from people indicate that the model reproduces the salient features of maximum-height jumping and normal walking on the level. Analyses of the model solutions will allow detailed explanations to be given about the actions of specific muscles during each of these tasks.

Developmental origins of adult phonology: the interplay between phonetic emergents and the evolutionary adaptations of sound patterns

In this paper fragments of a theory of emergent phonology are presented. Phonological patterns are seen as products of cultural evolution adapted to universal biological constraints on listening, speaking and learning. It is proposed that children develop adult phonology thanks to the interaction of the emergent patterning of phonetic content and the adaptive organization of sound structure. Emergence - here used in the technical sense of qualitatively new development - is illustrated with examples from the study of perception, motor mechanisms and memory encoding. In this framework, there is no split between 'behavioral phonetics' and 'abstract phonology'. Phonology differs qualitatively from phonetics in that it represents a new, more complex and higher level of organization of speech behavior. Accordingly, the phonology that the child ends up with as an adult is neither abstract nor independent of use. It represents an emergent patterning of phonetic content.