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Young-Hoo Kwon

The purpose of this study was twofold: (a) to investigate the effect of the method of body segment parameter (BSP) estimation on the accuracy of the experimental simulation of a complex airborne movement; and (b) to assess the applicability of selected BSP estimation methods in the experimental simulation. It was hypothesized that different BSP estimation methods would provide different simulation results. A sensitivity analysis was performed to identify the BSP items and segments responsible for the inter-method differences in the simulation accuracy. The applicability of the estimation methods was assessed based on the simulation results and the number of anthropometric parameters required. Ten BSP estimation methods classified into 3 groups (4 cadaver-based, 4 gamma mass scanning-based, and 2 geometric) were employed in a series of experimental simulations based on 9 double-somersault-with-full-twist H-bar dismounts performed by 3 male college gymnasts. The simulated body orientation angles were compared with the corresponding observed orientation angles in computing the simulation errors. The inclination and twist simulation errors revealed significant (p < .05) differences among the BSP estimation groups and methods. It was concluded that: (a) the method of BSP estimation significantly affected the simulation accuracy, and more individualized BSP estimation methods generally provided more accurate simulation results; (b) the mass items, and the lower leg and thorax/ abdomen were more responsible for the intermethod differences in the simulation accuracy than other BSP items and segments, respectively; (c) the ratio methods and the simple regression methods were preferable in simulation of the somersaulting motion due to the fewer anthropometric parameters required; (d) the geometric models and the cadaver-based stepwise regression method were superior to the other methods in the simulation of the complex airborne motion with twist.

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Young-Hoo Kwon

Ten body segment parameter (BSP) estimation methods were selected to compute the BSPs of 3 collegiate male gymnasts: cadaver-based methods (Group C, 4 methods), mass scanning-based methods (Group M, 4 methods) and geometric methods (Group G, 2 methods). Angular momenta of nine double somersault with full twist H-bar dismounts performed by the 3 gymnasts were computed. Each trial was processed 10 times using 10 sets of BSPs obtained from the estimation methods. Intergroup and intermethod comparisons of the airborne angular momenta were made. It was concluded that the method of BSP estimation affected the magnitude of airborne angular momentum but did not affect the magnitude of angular momentum fluctuation during the airborne phase.

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Young-Hoo Kwon

The purpose of this study was twofold: (a) to investigate the effects of selected experimental factors on the magnitude of the object plane deformation due to refraction, and (b) to discuss their practical implications in an effort to improve the applicability of the 2-D DLT method in the underwater motion analysis. The RMS and maximum object plane reconstruction errors of various experimental conditions were computed systematically. To isolate the error due to refraction from the experimental errors, the comparator coordinates (image plane coordinates) of the control points were computed based on a theoretical refraction model rather than actual digitizing. It was concluded from a series of object plane reconstruction that among the distance and angle factors of the experimental setting in the 2-D underwater motion analysis, the camera-to-interface distance and the interface-to-control-object distance are the two major factors affecting the magnitude of the object plane deformation. The other factors revealed only minor effects. The advantages of the 2-D DLT method over the traditional multiplier method in underwater motion analysis. such as oblique projection and multiple camera setup. were further discussed. Possible ways to reduce the maximum reconstruction error were also explored.

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Somadeepti Chengalur, Timothy Aro and Young-Hoo Kwon

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Young-Hoo Kwon, Virginia L. Fortney and In-Sik Shin

Two of the most frequently performed vaults in the 1988 Olympic Games in Seoul were selected for 3-D cine-photogrammetry analysis: the Yurchenko layout with full twist and the Yurchenko layout. The performances included 20 vaults with the highest performance scores: 10 Yurchenko layout with Ml twist (YLF) and 10 Yurchenko layout (YL) vaults, which were performed in the women’s team optional competitions. The YLF group earned higher performance scores than the YL group. Average vaulting times were similar for the groups, but the YLF group showed shorter board and horse contact times and longer postflight times. The projectile motion variables were critical for better performance in the YLF group. Higher vertical velocity at horse takeoff was achieved mainly by minimizing its (Vv) loss during horse contact. The YL group showed the importance of angular momentum for better performance, with the normalized angular momentum during postflight being the critical variable for the YL vault.

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Young-Hoo Kwon, Lonn Hutcheson, Jeffrey B. Casebolt, Joong-Hyun Ryu and Kunal Singhal

The purpose of this study was to investigate the effects of transversely sloped ballasted walking surface on gait and rearfoot motion (RFM) parameters. Motion analysis was performed with 20 healthy participants (15 male and 5 female) walking in six surface-slope conditions: two surfaces (solid and ballasted) by three slopes (0, 5, and 10 degrees). The gait parameters (walking velocity, step length, step rate, step width, stance time, and toe-out angle) showed significant surface effect (p = .004) and surface-slope interaction (p = .017). The RFM motion parameters (peak everted/inverted position, eversion/inversion velocity, and acceleration) revealed significant surface (p = .004) and slope (p = .024) effects. The ballasted conditions showed more cautious gait patterns with lower walk velocity, step length, and step rate and longer stance time. In the RFM parameters, the slope effect was more notable in the solid conditions due to the gait adaptations in the ballasted conditions. Ballast conditions showed reduced inversion and increased eversion and RFM range. The RFM data were comparable to other typical walking conditions but smaller than those from running.

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Sangwoo Lee, Ronald Davis, Lawrence W. Judge, Young-Hoo Kwon, Kihoon Han, Jemin Kim, Jaewoong Kim and Jaehwa Kim

The purpose of this study was to investigate the relationships among release factors (speed, height, and angle) and distance thrown in Paralympic seated shot put. Fortyeight trials performed by 11 men and 5 women during the 2012 US Paralympic trials in track and field were analyzed. With both genders combined, release speed (r = .95, p < .01) and angle (r = .51, p < .01) showed significant correlations to distance thrown. Release speed (r = .94, p < .01) in men and all release factors (r = .60–.98, p < .02) in women showed significant correlations to distance. Release speed and angle were identified as important predictors of the distance, explaining over 89–96% of the variance in distance thrown. Unlike athletes without disability, seated shotputters exhibited significant positive speed–angle correlations (combined: r = .37, p < .01; women: r = .57, p = .03). Application of these results should address a focus in training on generating speed through the release point with a consistent release angle.