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Yuta Suzuki Michiyoshi Ae Shunsuke Takenaka Norihisa Fujii 《Sports biomechanics / International Society of Biomechanics in Sports》2014,13(2):144-153
The purpose of this study was to investigate differences in the support leg joint moment and moment power between side-step (SS) and cross-step (CS) cutting techniques with a prescribed 90° cutting angle. Ground reaction forces (1,000 Hz) and three-dimensional kinematics (250 Hz) of SS and CS cutting techniques were collected from 20 male college athletes. Normalised peak knee extension moment was larger in the SS technique than in the CS technique (0.40 ± 0.10 in SS; 0.26 ± 0.08 in CS). In the SS technique, the knee extensors ( ? 0.10 ± 0.06 in SS; ? 0.02 ± 0.04 in CS) and ankle plantarflexors ( ? 0.12 ± 0.05 in SS; ? 0.07 ± 0.03 in CS) did significantly more negative work (normalised). The direction change angle (40.5 ± 8.7° in SS; 33.0 ± 6.8° in CS) and the decrease in horizontal velocity of the centre of mass ( ? 0.63 ± 0.23 m/s in SS; ? 0.31 ± 0.23 m/s in CS) were significantly larger in the SS technique. These results suggest that the SS technique is an effective means of changing running direction at the expense of velocity of the centre of mass and that the CS technique is better for minimising the reduction in horizontal velocity of the centre of mass. 相似文献
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We examined the hypothesis that congruence between motivational dominance and state results in optimal psychological responses and performance during exercise. Twenty participants (10 telic dominant and 10 paratelic dominant) rated their stress at 5 min intervals as they cycled on an ergometer at gas exchange threshold for 30 min in both telic and paratelic state manipulated conditions. Participants then performed a test to exhaustion at a resistance equivalent to 110% of VO(2max). The hypothesized interaction between condition and dominance was significant for internal tension stress, as paratelic dominants were more stressed than telic dominants when exercising in the telic state and telic dominants were more stressed than paratelic dominants when exercising in the paratelic state. Similarly, the condition × dominance interaction for internal stress discrepancy was significant, as paratelic dominants reported greater internal stress discrepancy exercising in the telic compared with the paratelic state. Findings are discussed in relation to the application of reversal theory for understanding stress responses during aerobic exercise. 相似文献
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Seitaro Kumamoto Kenshiro Nakatake Souichiro Fukuyama Keiichiro Yasuda Yusuke Kitamura Masaaki Iwatsuki Hideo Baba Toshihiro Ihara Yoshitaka Nakanishi Yuta Nakashima 《Biomicrofluidics》2020,14(6)
To study an environmental or biological solution, it is essential to separate its constituents. In this study, a 3D-deformable dynamic microfilter was developed to selectively separate the target substance from a solution. This microfilter is a fine metallic nickel structure fabricated using photolithography and electroplating techniques. It is gold-coated across its entire surface with multiple slits of 10–20 μm in width. Its two-dimensional shape is deformed into a three-dimensional shape when used for fluid separation due to hydrodynamic forces. By adjusting the pressure applied to the microfilter, the size of the gap created by deformation can be changed. To effectively isolate the target substance, the relationship between the solution flow rate and the extent of microfilter deformation was investigated. The filtration experiments demonstrated the microfilter’s ability to isolate the target substance with elastic deformation without undergoing plastic deformation. Additionally, modification of the microfilter surface with nucleic acid aptamers resulted in the selective isolation of the target cell, which further demonstrates the potential application of microfilters in the isolation of specific components of heterogeneous solutions. 相似文献
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Takanori Ishii Michiyoshi Ae Yuta Suzuki Yasuto Kobayashi 《Sports biomechanics / International Society of Biomechanics in Sports》2018,17(2):238-250
This study sought to identify biomechanical factors that determine fast and skilful execution of the seoi-nage (shoulder throw) technique by comparing kinematics between elite and college judo athletes. Three-dimensional motion data were captured using a VICON-MX system with 18 cameras operating at 250 Hz as three male elite and seven male college judo athletes performed seoi-nage. No significant difference was found in motion phase time of the turning phase between the two groups, indicating that motion phase time is not necessarily a factor contributing quickness in seoi-nage. The maximum relative velocity of the whole body centre of mass along the anterior–posterior direction was significantly greater in the elite athletes (2.74 ± 0.33 m/s) than in the college athletes (1.62 ± 0.47 m/s) during the turning phase (p = 0.023). The overall angular velocity of the body part lines, particularly the arm line, tended to be greater in the elite athletes (p = 0.068). The results imply that the velocity of the thrower relative to the opponent in the forward drive and turning motion reflects high skill seoi-nage. Coaches should recognise the relative forward velocity as a factor that may contribute to a successful seoi-nage when teaching the judo throw technique. 相似文献
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Although electromyographic (EMG) gradients have been observed in passive musculature during perceptual motor tasks, it is unclear whether this is related to metamotivational state or dominance. In addition, a misfit effect has been suggested whereby individuals report negative psychological responses when metamotivational state and dominance do not match. Research examining these phenomena within an exercise context is limited; therefore, this study used a reversal theory (Apter, 2001) framework to examine two hypotheses. The first hypothesis was that an EMG gradient would be observed when individuals performed isokinetic leg extensions in a telic metamotivational state, regardless of telic or paratelic metamotivational dominance. Second, it was hypothesizsed that telic-dominant individuals and paratelic-dominant individuals would perform better on this task when in the telic and paratelic state, respectively. Altogether, 14 telic-dominant and 12 paratelic-dominant individuals performed 100 self-paced isokinetic leg extensions at a rate of 90°?·?s(-1) in both telic and paratelic state manipulated conditions. Regardless of state, an EMG gradient was observed in telic-dominant individuals but not in paratelic-dominant individuals. Paratelic-dominant individuals performed better in the paratelic than the telic state condition, whereas in the telic state condition, telic-dominant individuals performed better than paratelic-dominant individuals. Findings add to the debate concerning the role of telic metamotivational state and dominance in the production of EMG gradients. Performance data support the misfit effect that outcomes are more positive when metamotivational state and dominance are congruent. Suggestions for research developments in this area are offered, as are tentative implications for applied practice. 相似文献
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The occurrence frequencies of the dinucleotides of genes of three thermophilic and three mesophilic species from both archaea
and eubacteria were investigated in this study. The genes encoding water soluble proteins were rich in the dinucleotides of
purine dimers, whereas the genes encoding membrane proteins were rich in pyrimidine dimers. The dinucleotides of purine dimers
are the counterparts of pyrimidine dimers in a double-stranded DNA. The purine/pyrimidine dimers were favored in the thermophiles
but not in the mesophiles, based on comparisons of observed and expected frequencies. This finding is in agreement with our
previous study which showed that purine/pyrimidine dimers are positive factors that increase the thermal stability of DNA.
The dinucleotides AA, AG, and GA are components of the codons of charged residues of Glu, Asp, Lys, and Arg, and the dinucleotides
TT, CT, and TC are components of the codons of hydrophobic residues of Leu, Ile, and Phe. This is consistent with the suitabilities
of the different amino acid residues for water soluble and membrane proteins. Our analysis provides a picture of how thermophilic
species produce water soluble and membrane proteins with distinctive characters: the genes encoding water soluble proteins
use DNA sequences rich in purine dimers, and the genes encoding membrane proteins use DNA sequences rich in pyrimidine dimers
on the opposite strand. 相似文献
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Aerodynamic properties of an archery arrow 总被引：1，自引：0，他引：1
Takeshi Miyazaki Keita Mukaiyama Yuta Komori Kyouhei Okawa Satoshi Taguchi Hiroki Sugiura 《Sports Engineering》2013,16(1):43-54
Two support-interference-free measurements of aerodynamic forces exerted on an archery arrow (A/C/E; Easton Technical Products) are described. The first measurement is conducted in a wind tunnel with JAXA’s 60 cm Magnetic Suspension and Balance System, in which an arrow is suspended and balanced by magnetic force against gravity. The maximum wind velocity is 45 m/s, which is less than a typical velocity of an arrow (about 60 m/s) shot by an archer. The boundary layer of the arrow remains laminar in the measured Re number range (4.0 × 103 < Re < 1.5 × 104), and the drag coefficient is about 1.5 for Re > 1.0 × 104. The second measurement is performed by a free flight experiment. Using two high-speed video cameras, we record the trajectory of an archery arrow and analyze its velocity decay rate, from which the drag coefficient is determined. In order to investigate Re number dependence of the drag coefficient in a wider range (9.0 × 103 < Re < 2.4 × 104), we have developed an arrow-shooting system using compressed air as a power source, which launches the A/C/E arrow at an arbitrary velocity up to 75 m/s. We attach two points (piles) of different type (streamlined and bullet) to the arrow-nose. The boundary layer is laminar for both points for Re less than about 1.2 × 104. It becomes turbulent for Re larger than 1.2 × 104 and the drag coefficient increases to about 2.6, when the bullet point is attached. In the same Re range, two values of drag coefficient are found for the streamlined point, of which the lower value is about 1.6 (laminar boundary layer) and the larger value is about 2.6 (turbulent boundary layer), confirming that the point-shape has a crucial influence on the laminar to turbulent transition of the boundary layer. 相似文献
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This study evaluates whether high levels of executive function predict competition results 18 months later in junior tennis players. Forty junior tennis players (20 girls, 20 boys; 9–15 years old) who regularly participate in prefecture tennis tournaments were recruited. All participants underwent executive function evaluations (the Design Fluency Task) in July 2015 and their prefecture junior rankings in August 2015 and February 2017 were recorded. As a result, after controlling for age and gender, the future ranking (February 2017) was significantly predicted by performance in the Design Fluency Task (β = -.30, p = .02; ΔR2 = .08), whereas the prediction for August 2015 rank as the baseline was not significant (β = -.19, p = .17; ΔR2 = .03). After controlling for age, gender, and ranking in the baseline, the change in ranking was significantly predicted by performance in the Design Fluency Task (β = -.14, p = .02; ΔR2 = .02). This suggests that childhood executive function may play a significant role in success later in life. This study highlights how executive function predicts future success in a specific sport; as such, supporting the development of executive function may contribute to higher competition results. 相似文献
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