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James G. Hay and Timothy J. Koh

The purpose of this study was to develop measures of a long or triple jumper’s ability to use programming and visual control strategies during the approach to the takeoff. Five such measures were developed. The performances of the competitors in the men’s and women’s horizontal jumps at the 1987 Big Ten Conference Championships were filmed to obtain the required data. Percentiles were computed for each of the five measures and these were used, in conjunction with a performance profile, to evaluate the ability of an athlete to use the two strategies.

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Timothy J. Koh and James G. Hay

The motions of the landing leg in the final three strides of the approach in the long jump are described, as are the relationships of these landing leg motions with performance. Film analysis of 19 elite male long jumpers competing in the 1986 and 1987 TAG (U.S. national) Championships showed that backward sweeping, or “active,” landings were used in each stride considered. However, the landing in the last stride was less active than those in the two preceding strides. A mathematical model showed that muscle action reduced the forward horizontal velocity of the landing foot in each landing. There were no statistically significant correlations of measures of landing leg motion with measures of performance. However, there was some indication that landing leg motion plays a role in lowering the center of gravity in the second-last stride and that this lowering increases the distance of the jump. There was also some indication that placing the landing foot well forward of the body at the end of the last stride benefits the distance of the jump, perhaps by promoting the development of vertical velocity during the support phase of the jump. This appears to be more important than minimizing the loss in horizontal velocity during the support phase of the jump.

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Timothy J. Koh and James G. Hay

The motions of the landing leg preceding the support phases of the hop, step, and jump, thought to be important in the triple jump, are described. Film analysis of 16 elite male triple jumpers competing in the 1986 and 1987 TAC (U.S. national) Championships showed that backward sweeping, or “active,” landings were used prior to each support phase. A mathematical model showed that muscle action reduced the forward horizontal velocity of the landing foot during each landing. There were no statistically significant correlations of measures of landing leg motion with measures of performance. The landing prior to the jump phase was less active than the two preceding landings. However, the elite athletes in the present study were much more active in this landing than athletes of lesser ability. There was also some indication among the subjects of this study that activeness in this landing was associated with long triple jumps. Thus, activeness in this landing appears to be desirable but very difficult to achieve and/or use effectively.

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Walter Herzog, Timothy Koh, Evelyne Hasler and Tim Leonard

We hypothesize that the neuromuscular system is designed to function effectively in accomplishing everyday movement tasks. Since everyday movement tasks may vary substantially in terms of speed and resistance, we speculate that agonistic muscles contribute differently to varying movement tasks such that the mechanical, structural, and physiological properties of the system are optimized at all times. We further hypothesize that a mechanical perturbation to the musculoskeletal system, such as the loss of an important joint ligament or the change of a muscle’s line of action, causes an adaptation of the system aimed at reestablishing effective function. Here. we demonstrate how the specificity of the cat ankle extensors is used to accommodate different locomotor tasks. We then illustrate how the loss of an important ligament in the cat knee leads to neuromuscular adaptation. Finally, we discuss the adaptability of skeletal muscle following an intervention that changes a muscle’s line of action, moment arm, and excursion.

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Timothy J. Koh, Mark D. Grabiner and John J. Brems

Shoulder kinematics, including scapular rotation relative to the trunk and humeral rotation relative to the scapula, were examined during humeral elevation in three vertical planes via video analysis of intracortical pins. Helical axis parameters provided an easily interpretable description of shoulder motion not subject to the limitations associated with Cardan/Euler angles. Between 30 and 150° of elevation in each plane, the scapula rotated almost solely about an axis perpendicular to the scapula. Additional scapular rotation appeared to support the notion that the scapula moves “toward” the plane of elevation. Humeral rotation took place mainly in the plane of the scapula independent of the plane of elevation. Many parameters of shoulder complex kinematics were quite similar across all planes of elevation, suggesting a consistent movement pattern with subtle differences associated with the plane of elevation.