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Takahito Iga Hiroyuki Nunome Shinya Sano Nahoko Sato Yasuo Ikegami 《Sports biomechanics / International Society of Biomechanics in Sports》2018,17(4):477-493
To assess ball impact force during soccer kicking is important to quantify from both performance and chronic injury prevention perspectives. We aimed to verify the appropriateness of previous models used to estimate ball impact force and to propose an improved model to better capture the time history of ball impact force. A soccer ball was fired directly onto a force platform (10 kHz) at five realistic kicking ball velocities and ball behaviour was captured by a high-speed camera (5,000 Hz). The time history of ball impact force was estimated using three existing models and two new models. A new mathematical model that took into account a rapid change in ball surface area and heterogeneous ball deformation showed a distinctive advantage to estimate the peak forces and its occurrence times and to reproduce time history of ball impact forces more precisely, thereby reinforcing the possible mechanics of ‘footballer’s ankle’. Ball impact time was also systematically shortened when ball velocity increases in contrast to practical understanding for producing faster ball velocity, however, the aspect of ball contact time must be considered carefully from practical point of view. 相似文献
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ABSTRACTThis study aimed to investigate the influence of foot strike patterns on the behaviour of the triceps surae muscle-tendon unit, including the Achilles tendon whose length nearly corresponds to force of the triceps surae, and the medial gastrocnemius muscle (MG) during running. Seven male volunteers ran with forefoot and rearfoot strikes at 10, 14 and 18 km h?1 on a treadmill. The MG fascicle length was measured using ultrasonography. The in vivo length of the curved Achilles tendon was quantified by combining ultrasonography with optical motion capture of reflective markers on the right lower limb and an ultrasound probe. The forefoot strike resulted in a significantly shorter MG fascicle length at the initial contact, at Achilles tendon peak elongation, and at toe-off, than the rearfoot strike. The Achilles tendon length at initial contact was greater during the forefoot strike than during the rearfoot strike at 18 km h?1, while its peak elongation was not significantly different during forefoot and rearfoot running. These results indicate that the MG, with a shorter length during forefoot running, manages to address demands for a similar peak force of the triceps surae than during rearfoot running. 相似文献
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Kohei Watanabe Hiroyuki Nunome Koichiro Inoue Takahiro Iga Hiroshi Akima 《Sports biomechanics / International Society of Biomechanics in Sports》2020,19(3):295-306
ABSTRACTA possible link between soccer-specific injuries, such as groin pain and the action of hip adductor muscles has been suggested. This study aimed to investigate neuromuscular activation of the adductor magnus (AM) and longus (AL) muscles during instep and side-foot soccer kicks. Eight university soccer players performed the two types of kick at 50%, 75% and 100% of the maximal ball speed. Surface electromyography (EMG) was recorded from the AM, AL, vastus lateralis (VL) and biceps femoris (BF) muscles of both kicking and supporting legs and the kicking motions were three-dimensionally captured. In the kicking leg, an increase in surface EMG with an increase in ball speed during instep kicking was noted in the AM muscle (p < 0.016), but not in AL, VL or BF muscles (p > 0.016). In the supporting leg, surface EMG of both AM and AL muscles was significantly increased with an increase in the ball speed before ball impact during both instep and side-foot kicks (p < 0.016). These results suggest that hip adductor muscles markedly contribute to either the kicking or supporting leg to emphasise the action of soccer kicks. 相似文献
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The aim of this study was to evaluate physiological and technical attributes of prepubertal soccer players during multiple small-sided games (SSGs), and determine if SSGs can act as a talent identification tool. Sixteen highly trained U10 soccer players participated and separated into two groups of eight. Each group played six small-sided (4 vs. 4) matches of 5-min duration. Each player was awarded total points for the match result and goals scored. A game technical scoring chart was used to rate each player’s performance during each game. Time-motion characteristics were measured using micromechanical devices. Total points had a very large significant relationship with game technical scoring chart (r = 0.758, P < 0.001). High-speed running distance had a significantly large correlation with game technical scoring chart (r = 0.547, P < 0.05). Total distance covered had a significant and moderate correlation with game technical scoring chart (r = 0.545, P < 0.05) and total points (r = 0.438, P < 0.05). The results demonstrated a large agreement between the highest-rated players and success in multiple SSGs, possibly due to higher-rated players covering larger distances in total and at high speed. Consequently, multiple SSG could be used to identify the more talented prepubertal soccer players. 相似文献
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In this paper we consider the negotiating positions adopted by the US and Japan for the liberalisation of trade in educational services under the General Agreement on Trade in Services (GATS). We argue that the US adopts a position of hegemon and freerider in the development of a liberalisation regime in education. The aggressive character of the US position is profoundly influenced by: (1) a strong federal government level faith in service liberalisation; (2) high levels of domestic privatisation in the fields of higher education, training, testing and evaluation; (3) active lobbying by educational services providers. Nonetheless, the US is cautious about allowing foreign competition into domestic education markets. This stems in part from active resistance of the public education sector; and in part because of the delicate jurisdictional questions it would raise given the constitutional right of states to control educational policy. Ironically, US reticence also seems to be related to the relatively high levels of private educational expenditures in the US. In contrast, the Japanese government's approach is motivated primarily by bet‐hedging and legitimation concerns. Japan is not a net‐exporter of educational services and cannot be said to have comparative advantage in this field. However, three things seem to be influencing what might be seen as Japan's surprising decision to join the group of only four (World Trade Organization)WTO member nations who have submitted negotiating proposals for trade in educational services. First, the Japanese are strongly interested in the expansion of trade in other service areas, and may be willing to negotiate in education in order to further negotiations in these other areas. Secondly, Japan's decade‐long economic crisis has contributed to an important policy shift in the government's plans for higher education. Questions about the relevance and competitiveness of Japanese higher education have recently led the Japanese government to commit itself to this sector's ‘internationalisation’. To this end the government is also considering legislation that allows for the accreditation of 282 K. Mundy & M. Iga foreign higher education within Japan. Nonetheless, the Japanese government's negotiating proposal on trade in educational services is much more tentative than that presented by the European Union (EU) and New Zealand, for example. Japan places unique emphasis on the importance of regulatory control mechanisms for foreign service providers. As in the US, at least some part of the Japanese reticence seems to be driven by relatively high levels of private educational expenditure in the country. This paper is organised as follows. In Sections I‐V we briefly trace the history of the WTO, the GATS, and the inclusion of educational services in the GATS. Here we emphasise the strong role played by the US in the inclusion of services in international trade negotiations, and its part in the collapse of ‘embedded liberalism’ as a foundation for a multilateral trade regime. We also look briefly at the contentious aspects of the current round of negotiations in the education sector and describe their current state of play. In Sections VI and VII, we look more closely at the political economy of the negotiating positions adopted by the US and by Japan. We situate the negotiating approaches of these two countries within a comparative analysis of their relative share of current trade in educational services. In our concluding section, we begin to answer two questions. First, what theoretical framework best explains the content and direction of the American and Japanese negotiating frameworks? Second, what can the negotiating positions of these two important WTO members tell us about the overall direction and likely outcomes of the Doho round of negotiations on educational services? 相似文献
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Samuel R. Hodge Takahiro Sato Takahito Mukoyama Francis M. Kozub 《International Journal of Disability, Development & Education》2013,60(4):332-346
The purpose of this study was to assess the validity and reliability of the Physical Educators’ Judgments about Inclusion (PEJI) survey for analysing the judgments of Japanese (361 male, 170 female) physical education teacher education majors. A secondary purpose was to examine group differences in judgments as a function of gender and past experiences. Data were collected and psychometrical properties of the PEJI were assessed using a maximum-likelihood extraction method. Confirmatory factor analysis resulted in salient loadings for all items on three hypothesised dimensions, resulting in 47% explained variance for measuring judgments about: Inclusion versus Exclusion, Acceptance of Students with Disabilities, and Perceived Training Needs. Supported by the three interpretable factors that emerged, construct validity evidence is presented. Although most of the physical education teacher education majors sampled had yet to teach students with disabilities, they had formed preliminary judgments about doing so. 相似文献
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Hiroyuki Nunome Koichiro Inoue Kohei Watanabe Takahito Iga Hiroshi Akima 《Journal of sports sciences》2018,36(22):2588-2595
During a soccer match, players are often required to control the ball velocity of a kick. However, little information is available for the fundamental qualities associated with kicking at various effort levels. We aimed to illustrate segmental dynamics of the kicking leg during soccer instep kicking at submaximal efforts. The instep kicking motion of eight experienced university soccer players (height: 172.4 ± 4.6 cm, mass: 63.3 ± 5.2 kg) at 50, 75 and 100% effort levels were recorded by a motion capture system (500 Hz), while resultant ball velocities were monitored using a pair of photocells. Between the three effort levels, kinetic adjustments were clearly identified in both proximal and distal segments with significantly different (large effect sizes) angular impulses due to resultant joint and interaction moments. Also, players tended to hit an off-centre point on the ball using a more medial contact point on the foot and with the foot in a less upright position in lower effort levels. These results suggested that players control their leg swing in a context of a proximal to distal segmental sequential system and add some fine-tuning of the resultant ball velocity by changing the manner of ball impact. 相似文献
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