The aim of this study was to analyse the principal mechanics of circles. Seventeen university male gymnasts performed circles on an instrumented pommel horse model that enabled the pommel reaction forces to be recorded at 1000 Hz with two force plates. The circles were also videotaped using two digital video cameras operating at 60 frames per second. During circles, the vertical component of the reaction forces peaked in the double-hand support phases. Changes in the velocity of the centre of mass corresponded to the change in the tangential components of horizontal reaction forces. The velocity of the centre of mass had its peaks in the single-hand support phases and its local minimums in the double-hand support phases. The velocity of the ankles and that of the centre of mass of the head and trunk were minimal in the single-hand support phases and were maximal in the double-hand support phases. These results suggest that the circles were composed of vertical movements and two kinds of rotations: rotation of the centre of mass and rotation of the body itself about the centre of mass. These two kinds of rotations, which influence the legs' rotational velocity, are phase dependent. To further our understanding of circles, research on circles in different orientations on the pommel horse will be beneficial.

In the third study of this series, we examined how circles with a suspended aid would vary depending of the gymnast's level of expertise. We analysed circles with the aid performed by three groups of eight gymnasts: expert, intermediate, and developing groups. The gymnasts for the expert and intermediate groups were selected from the previous studies based on judges' evaluation of their non-aid circles. The developing group of eight gymnasts, who were unable to perform circles on pommel horse without an aid, were added to this study and performed three sets of 10 circles on the pommel horse with the aid. Discriminative biomechanical variables identified in the previous two studies were used to compare circles with the aid among the three groups. As a result, the expert group demonstrated a larger pommel reaction force and a smaller aid reaction force than the other two groups, implying that they were less dependent on the aid. The smaller aid reaction force resulted in a smaller net hip joint moment. Furthermore, the expert group showed a shorter total duration and a greater shoulder excursion. In summary, the suspended aid can be used in a progressive manner depending on the gymnast's level of expertise.

One of the most fundamental skills on the pommel horse is double leg circles (circles). Circles can be performed on all parts of the pommel horse. It was hypothesized that the different sets of physical constraints of the apparatus require a gymnast to adapt circles technique. The purpose of this study was to quantify how gymnasts modify their technique during circles to accommodate different physical obstacles due to different support surfaces and body orientations. To investigate these adaptations, a comparison of the two most common circles on pommel horse Á namely, circles in cross support (crosscircles) and circles in side support (side-circles) Á was carried out. Seven elite male gymnasts performed three sets of 10 cross-circles and side-circles on a pommel horse. Three-dimensional coordinates were acquired using 12 Qualisys ProReflex motion tracking cameras operating at 120 Hz. Temporal characteristics, the motion of the centre of mass, and the body angles Á flexion and lateral flexion Á were analysed. We found that cross-circles took less time to complete a single circle (0.9290.02 vs. 0.9590.02 s), had a smaller ratio for the rear support phase (0.1590.02 vs. 0.1890.03), a narrower supporting-hand distance (0.3390.03 vs. 0.5290.00 m), greater flexion of the body over the rear support phase (449128 vs. 27988), and less lateral flexion of the body over the single-hand support phase (entry: 20958 vs. 35938; exit: 26948 vs. 33948) than side-circles. Our results suggest that gymnasts adapt their technique to the physical constraints imposed by the shape of the pommel horse and the location and orientation of the circles. Cross-circles were characterized by a high rear support position with a narrower hand-spacing, which would require excellent shoulder flexibility and strength. Consequently, lack of these traits may explain the need for greater body flexion in cross-circles than in side-circles during rear support. Understanding the technical differences will facilitate an effective transfer of the technical similarities among different types of circles.

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1) 大阪体育大学体育学部 〒590 0496 大阪府泉南郡熊取町朝代台 1 1 2) トップスポーツクラブ 〒590 0496 大阪府泉南郡熊取町朝代台 1 1 連絡先 藤原敏行 1. School of Health and Sport Sciences, Osaka University of Health and Sport Sciences 1 1, Asashiro-dai, Kumatori-cho, Sennan-gun, Osaka 590 0496 2. Top Sports Club 1 1, Asashiro-dai, Kumatori-cho, Sennan-gun, Osaka 590 0496 Corresponding author fujihara＠ouhs.ac.jp 435 体育学研究 62435 453，2017 総 説 体操競技の跳馬における助走速度とその測定方法 藤原 敏行 1) 山本 詠人 2) 淵本 隆文 1) Toshiyuki Fujihara 1 , Eito Yamamoto 2 and Takafumi Fuchimoto 1 : Run-up velocity in the gymnastics vault and its measurement. Japan J. Phys. Educ. Hlth. Sport Sci. 62: 435 453, December, 2017 AbstractIn gymnastics, the vault run-up velocity is important from a competitive aspect. Relevant data in the literature have been relatively abundant but not well organized. The present review covers previous research on run-up velocity data and discusses its measurement for future research, as well as data utilization in practice. Based on the results of several representative studies, we can conˆdently state that a highly skilled male gymnast reaches a run-up velocity of over 8.5 m/s. At world-level competitions, the average run-up velocity is approximately 8.2 m/s for male gymnasts.Top-level female gymnasts also reach similar speeds. However, considering the issues related to the measurements used and the validity of the reported data, careful investigation is required, particularly with regard to the last step onto the springboard. We also discuss some di‹culties with the use of current systems of velocity measurement, such as motion analysis, laser systems, and photocells, in daily training. In order for run-up velocity data to be measured and utilized in practice, (1) measurements should be performed easily, (2) the data should be more reliable and valid than a subjective evaluation by a coach or a gymnast, (3) feedback should be provided automatically and immediately, and (4) the measurement system should be reasonably aŠordable.