PubMed · 4433481
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1974. Editorial: The schematic eye.. https://doi.org/10.1136/bjo.58.8.707
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A series of overarm throws, constrained to the parasagittal plane, were simulated using a muscle model actuated two-segment model representing the forearm and hand plus projectile. The parameters defining the modeled muscles and the anthropometry of the two-segment models were specific to the two young male subjects. All simulations commenced from a position of full elbow flexion and full wrist extension. The study was designed to elucidate the optimal inter-muscular coordination strategies for throwing projectiles to achieve maximum range, as well as maximum projectile kinetic energy for a variety of projectile masses. A proximal to distal (PD) sequence of muscle activations was seen in many of the simulated throws but not all. Under certain conditions moment reversal produced a longer throw and greater projectile energy, and deactivation of the muscles resulted in increased projectile energy. Therefore, simple timing of muscle activation does not fully describe the patterns of muscle recruitment which can produce optimal throws. The models of the two subjects required different timings of muscle activations, and for some of the tasks used different coordination patterns. Optimal strategies were found to vary with the mass of the projectile, the anthropometry and the muscle characteristics of the subjects modeled. The tasks examined were relatively simple, but basic rules for coordinating these tasks were not evident.
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Growth reflects general health but also the nutritional and environmental health of a child. Disordered growth may be an early manifestation of disease or deficiency. In Sweden, the newly updated growth charts are highly valued at the child health services, yet measurements of height, weight and head circumference of four infants showed that even experienced nurses achieved noticeably large differences in their individual results. In several cases the plotted data also deviated concerning the exact age of the child or the registered value. Awareness of methodological problems should lead to more accurate advice and referral.