Relationship between the peak time of hamstring stretch and activation during sprinting     

Ayako Higashihara  Yasuharu Nagano  Takashi Ono  Toru Fukubayashi 《European Journal of Sport Science》2016,16(1):36-41

The purpose of this study was to investigate the time series relationships between the peak musculotendon length and electromyography (EMG) activation during overground sprinting to clarify the risk of muscle strain injury incidence in each hamstring muscle. Full-body kinematics and EMG of the right biceps femoris long head (BFlh) and semitendinosus (ST) muscles were recorded in 13 male sprinters during overground sprinting at maximum effort. The hamstring musculotendon lengths during sprinting were computed using a three-dimensional musculoskeletal model. The time of the peak musculotendon length, in terms of the percentage of the running gait cycle, was measured and compared with that of the peak EMG activity. The maximum length of the hamstring muscles was noted during the late swing phase of sprinting. The peak musculotendon length was synchronous with the peak EMG activation in the BFlh muscle, while the time of peak musculotendon length in the ST muscle occurred significantly later than the peak level of EMG activation (p < 0.05). These results suggest that the BFlh muscle is exposed to an instantaneous high tensile force during the late swing phase of sprinting, indicating a higher risk for muscle strain injury.  相似文献   

Conversion of CO<Subscript>2</Subscript> to useful substances with composite iron,nickel, and copper catalysts     

Takashi Sagawa 《浙江大学学报(A卷英文版)》2018,19(1):80-85

Composite materials of Fe/Al₂O₃, which consist of small particles of iron supported by thermally stable alumina even at 500–700 °C, have been widely used in the water-gas shift reaction for natural gas reforming. Therefore, Fe/Al₂O₃ is one of the promising candidates for re-transformation of exhausted CO₂ into fuels such as alcohols and hydrocarbons. The development of a CO₂ reforming system using the composite materials of Fe/Al₂O₃ through CO₂ reduction to CO, dissociation of water into hydrogen, and methanol synthesis has been investigated. It was found that dry and steam (i.e. wet) reforming of CO₂ produced almost the same amount of CO. At a temperature above 500 °C, maximal and saturated yields of CO and H₂ from CO₂ and water were obtained. However, this CO₂ reforming system requires higher-pressure conditions from several tens to hundreds standard atmospheric pressure in order to achieve high yield and selectivity for methanol production. In this study we developed the modified CO₂ reforming system by the utilization of Ni and/or Cu instead of Fe in order to obtain other types of useful products such as CO, CH₄, and carbon, more efficiently and selectively under atmospheric pressure. When Ni or Cu was used, conversion of CO₂ was reduced to 76%, while 9% of methane was detected in the case of Ni. On the other hand, though the CO₂ conversion reduced half of the Fe, the selectivity of CO from CO₂ increased to 95% in the case of Cu.  相似文献   

A Vote for Consensus: Democracy and difference in Japan     

Hiromi Yamashita  Christopher Williams 《比较教育学》2002,38(3):277-289

How evident is democracy within education in Japan, and is current practice different from elsewhere? This paper assesses the perception that Japanese political and educational practices are not fully 'democratic'. The first part examines the Japanese perspective on democracy, and then considers democracy and education in Japan. From a school-based study, the second part discusses examples of class practice concerning decision-making. The paper concludes that democracy is deeply rooted in Japanese history, but not in a form that is readily recognisable to Western observers. Consensus has been more significant than voting. The view that the US administration had a strong influence probably reflects policy rhetoric, not the reality in schools. But this rhetoric may have led to a belief that 'democracy' is not an appropriate term within contemporary Japanese education. However, what happens in Japanese classrooms equates with 'democratic' practice elsewhere.  相似文献   

Adverse effects of energy restriction on myogenic enzymes in judoists   总被引：1，自引：1，他引：0  

Umeda T  Nakaji S  Shimoyama T  Yamamoto Y  Totsuka M  Sugawara K 《Journal of sports sciences》2004,22(4):329-338

In this study, we examined the effects of weight reduction by restricting energy intake on muscle function and serum concentrations of myogenic enzymes in judoists. Twenty-seven male judoists aged 19.3 +/- 0.6 years (mean +/- s) were divided into three groups based on the extent of body weight reduction: high weight reduction (height 1.70 +/- 0.05 m, body mass 78.5 +/- 13.6 kg), low weight reduction (height 1.70 +/- 0.05 m, body mass 80.7 +/- 13.1 kg) and a group that maintained body weight while continuing to perform exercise training (height 1.78 +/- 0.07 m, body mass 78.7 +/- 8.8 kg). Body composition, blood biochemistry, energy intake and anaerobic power were assessed on four occasions: 20 days (baseline data), 4 days and 1 day before and 7 days after competition. Compared with baseline, body mass and fat-free mass were significantly lower 1 day before competition in the high and low weight reduction groups (both P < 0.01); these changes persisted for 7 days after competition in the high weight reduction group. Serum creatine kinase was significantly elevated 1 day before competition in all groups (all P < 0.05), and remained higher 7 days after competition in both the high and low weight reduction groups. Compared with baseline, maximal anaerobic power was significantly lower 1 day before competition only in the high weight reduction group (P < 0.01). Our results suggest that energy restriction in addition to intense exercise training before major competition has an adverse effect on anaerobic power and elevates serum creatine kinase concentration, leading to an impairment of muscular function and an increased susceptibility of muscle tissue to injury.  相似文献   

Postcontraction influences on reaction time     

Etnyre B  Kinugasa T 《Research quarterly for exercise and sport》2002,73(3):271-281

The purpose of this study was to compare reaction time (RT) and fractionated RT components (premotor and motor times) between normal and postcontraction conditions. Twelve participants performed 20 trials each of control and postcontraction RT conditions. For the control condition, participants executed a learned, rapid, knee-extension contraction response to an auditory stimulus. The postcontraction condition was identical to the control condition except that the participants performed a 3-s isometric contraction of the knee extensor muscles prior to an auditory stimulus. Muscle activity was recorded from the quadriceps muscle group. Results indicated that the postcontraction condition was significantly faster than the control condition for the average RT, premotor time, and motor time. It was concluded that reaction time, processing time, and muscle contraction time for a learned task could be significantly reduced following an isometric contraction.  相似文献   

Age-Related Changes in Soluble Vascular Endothelial Growth Factor Receptor 1 (sVEGFR1) and Receptor 2 (sVEGFR2) in Healthy Japanese Subjects     

Yoshihiro Okamoto  Tomoyo Mita  Testuri Kodama  Yoshimitsu Gotoh  Naoya Fujita  Takashi Fukui  Toshiyuki Masuzawa 《Indian journal of clinical biochemistry : IJCB》2015,30(3):351-356

We measured serum soluble vascular endothelial growth factor receptor 1 (sVEGFR1) and receptor 2 (sVEGFR2) levels in healthy Japanese individuals in order to establish a reference value using a specific ELISA. Significant differences were observed in serum sVEGFR1 and sVEGFR2 levels between children and adults. To demonstrate the usefulness of the reference value for children, we measured serum sVEGFR1 and sVEGFR2 levels in children with diarrhea positive (D+) hemolytic uremic syndrome (HUS) as a preliminary study. Serum sVEGFR2 levels in children with HUS were markedly higher than those in healthy children from the onset of D + HUS. The reference value for healthy children in the present study will allow normal and pathological conditions to be discriminated from each other in future study  相似文献   

Predictors of Adult Education Program Satisfaction in Urban Community-Dwelling Older Adults     

Takashi Yamashita  Erick B. López  Jennifer R. Keene  Jennifer M. Kinney 《Educational gerontology》2015,41(11):825-838

Lifelong learning is receiving greater attention due to population aging in modern societies. Lifelong learning benefits individuals by supporting their physical, psychological, social, and economic well-being. However, older adults generally have lower motivation for learning than younger adults, and facilitating long-term participation in learning activities is still challenging. Previous studies mainly identified negative factors such as barriers and obstacles to individuals’ initial participation in lifelong learning programs. As such, less is known about positive factors that promote long-term participation. To address this gap, data were collected from 330 older adults who participated in the Osher Lifelong Learning Institute program in an urban community in the United States. Results from proportional odds ordinal logistic regression analysis demonstrated that gender, number of household members, income, religious affiliation, self-rated health, and number of courses taken were associated with satisfaction with the program. In hopes to promote true lifelong learning, possible explanations about the findings are explored and several recommendations for existing lifelong learning programs are derived in this study.  相似文献   

The problems with a ‘fact’-focused approach in environmental communication: the case of environmental risk information about tidal flat developments in Japan     

Hiromi Yamashita 《Environmental Education Research》2015,21(4):586-611

One of the main approaches used in communicating environmental issues to citizens is conveying ‘factual’ information about a particular environment. However, despite previous research and recommendations made by critical environmental educators, there still seems to be a belief that the more ‘factual’ information one can convey, the more citizens will become aware of the issue, and this will prompt them to change their behaviours. In this article, I will argue that continuing with a ‘fact’-focused practice in Japan and elsewhere could be problematic for three key reasons: (1) it ignores diversity in the ‘facts’ provided to people; (2) it reinforces the ‘hierarchy of knowledge’; and (3) it ignores the ‘myth of nature’ among information receivers and senders. Key recommendations for incorporating a critical environmental education approach include utilising locally available environmental information on contentious environmental issues; investigating particular terminology used and missing information (including tacit knowledge); and encouraging critical learning about statistics and pictorial representations.  相似文献   

A robot is watching me!: Five-year-old children care about their reputation after interaction with a social robot     

Yuko Okumura  Takashi Hattori  Sanae Fujita  Tessei Kobayashi 《Child development》2023,94(4):865-873

Since robots are becoming involved in children's lives, it is urgent to determine how children perceive robots. The present study assessed whether Japanese 5-year-olds care about their reputation when interacting with a social robot. Children were given stickers and asked to divide them between themselves and an absent recipient. Results revealed that children (N = 112, 55 boys, 57 girls) strategically shared more stickers when being watched by a social interactive robot than by an attentional but non-interactive robot or a still robot. Additionally, children (N = 36, 18 boys, 18 girls) attributed higher psychological properties to social robots. This study is the first to show that 5-year-olds care about their reputations from social robots.  相似文献   

How pre-service teachers navigate trade-offs of food systems across time scales: a lens for exploring understandings of sustainability     

Lina Yamashita  Kathryn Hayes  Cary J. Trexler 《Environmental Education Research》2017,23(3):365-397

In response to the increasing recognition of the need for sustainable food systems, research on students’ and educators’ knowledge of food systems and sustainability more broadly has grown but has generally focused on what people ‘fail’ to understand. Moving away from this deficit approach, the present study used semi-structured interviews to explore how 12 pre-service teachers (PSTs) in the US consider sustainability in terms of the trade-offs – or concurrent costs and benefits – associated with using different agricultural resources over short, medium, and long terms. Drawing upon the constructs of framing, metacognition, and complex causality, the study found that the majority of PSTs referred to indirect experiences of seeing or hearing about agricultural resources to demonstrate stable knowledge of short-term trade-offs and construct tentative knowledge about medium-term trade-offs. Few described long-term trade-offs. Most participants also acknowledged some gaps in their knowledge in discussing trade-offs across the different time scales. Findings suggest the importance of leveraging and building upon educators’ (and ultimately students’) prior experiences to build their understanding of complex trade-offs that underlie food systems. The study also illustrates the value of using the concept of trade-offs across time scales to explore people’s conceptions and understandings of sustainability.  相似文献