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Ya-Ting Yang, Yasuyuki Yoshida, Tibor Hortobágyi and Shuji Suzuki

We determined the angular range of motion and the relative timing of displacement in the thorax, lumbar spine, and pelvis in the transverse plane during treadmill walking at three velocities. Nine healthy young females walked on a treadmill for three minutes at 0.40, 0.93, and 1.47 m/s. The position of seven reflective markers and three rigs placed on the thorax, lumbar spine, and pelvis were recorded at 200 Hz by an eight-camera motion capture system. As gait velocity increased, stride length increased, cycle time decreased, and angular displacement in the thorax and L1 decreased but increased at the pelvis and L5 (all P < .05). The time of maximal angular rotation occurred in the following sequence: pelvis, L5, L3, L1, and thorax (P < .001). The thorax and L1 and L3 were in-phase for shorter duration as gait velocity increased, and this reduction was especially large, approx. 32% (P < .05), between thorax and pelvis. As gait velocity increased, the pelvis rotated earlier, causing the shortening of in-phase duration between thorax and pelvis. These data suggest that, as gait velocity increases, pelvis rotation dictates trunk rotation in the transverse plane during gait in healthy young females.

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Jesús Dapena

This project sought to break down high jump twist rotation into portions contributed by angular momentum and those contributed by rotational action and reaction ("catting"). Five male and 5 female high jumpers were studied with three-dimensional film/video analysis procedures. The hip twist angle at the peak was broken down into an initial twist angle at takeoff and the subsequent twist rotation accumulated between takeoff and the peak. The latter was in turn broken down into rotations contributed by the twisting component of angular momentum and rotations contributed by catting. It was found that the contribution of catting to the twist rotation was at least as large as that of the angular momentum. The important contribution of catting to the twist rotation introduces the possibility that defects in its execution might play a role in the problems that some high jumpers have with twist rotation.

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Ross H. Sanders

This study was designed to investigate the effect of ability on technique in the forward somersault with half twist (Barani) and the forward somersault with one and one half twists (Rudi) on the trampoline. Eleven trampolinists ranging in ability from elite (national representative) to early intermediate (regional representative) were analyzed using three-dimensional analysis techniques. Cumulative twist angle, rate of twist, angle of tilt of the twist axis, chest rotation, hip angle, and hip lateral flexion angle were measured. Characteristics of the arm actions were also assessed using an internal frame of reference. To generate twist in the Baranis, trampolinists tilted the axis between 5° and 14°; the amount of tilt was inversely related to ability (p < .05). In the Rudis, subjects tilted the axis between 15° and 23° using more asymmetrical arm actions and larger and more rapid hip extensions, hip lateral flexions, and chest rotations than in the Baranis. The timing and magnitude of the actions differed among the subjects and were related to ability.

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Maurice R. Yeadon, Sung-Cheol Lee and David G. Kerwin

At the 1988 Seoul Olympic Games, eight full twisting somersault dismounts from the high bar were filmed using two cameras during the compulsory exercises of the Men’s High Bar competition. Angles describing body configuration and orientation were determined and were input into a computer simulation model of aerial movement. The deviations between simulation and film were less than 2.5° for tilt angles and less than 0.07 revolutions for twist angles. The twisting techniques employed were quantified using the tilt angle as a measure of twisting potential. Contributions to the maximum tilt angle were determined using simulations based on modifications of the film data. Each of the eight competitors obtained most of the tilt using aerial rather than contact techniques. In general, the majority of the aerial contributions arose from asymmetrical arm and hip movements.

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Maurice R. Yeadon

At the 1988 Calgary Winter Olympics, six triple somersaults with three twists or four twists were filmed using two cameras. Angles describing body configuration and orientation were determined and were used as input into a computer simulation model of aerial movement. It was found that the twist angle of each simulation deviated from the corresponding angle obtained from film by less than 0.08 revolutions during the first somersault of each movement. Contributions to the tilt angle after one somersault were determined using simulations based on modifications of the film data. It was found that of the six competitors, two initiated the twist during the takeoff phase, two initiated the twist during the aerial phase, and two used a combination of both methods.

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Tanghuizi Du, Ikumi Narita and Toshimasa Yanai

Low back pain is a common problem among competitive swimmers, and repeated torso hyperextension is claimed to be an etiological factor. The purpose of this study was to describe the three-dimensional torso configurations in the front crawl stroke and to test the hypothesis that swimmers experience torso hyperextension consistently across the stroke cycles. Nineteen collegiate swimmers underwent 2 measurements: a measurement of the active range of motion in 3 dimensions and a measurement of tethered front crawl stroke at their maximal effort. Torso extension beyond the active range of torso motion was defined as torso hyperextension. The largest torso extension angle exhibited during the stroke cycles was 9 ± 11° and it was recorded at or around 0.02 ± 0.08 s, the instant at which the torso attained the largest twist angle. No participant hyperextended the torso consistently across the stroke cycles and subjects exhibited torso extension angles during tethered front crawl swimming that were much less than their active range of motion. Therefore, our hypothesis was rejected, and the data suggest that repeated torso hyperextension during front crawl strokes should not be claimed to be the major cause of the high incidence of low back pain in swimmers.