Background: In soccer, the roles of the dominant (kicking) and nondominant (supporting) legs are different. The kinematic differences between the actions of the dominant and nondominant legs in female soccer players are not clear. Purpose: To clarify the kinematic differences between dominant and nondominant legs during a single-leg drop vertical jump (DVJ) in female soccer players. Study Design: Controlled laboratory study. Methods: A total of 64 female high school and college soccer players were included in this study. Participants performed a single-leg DVJ test utilizing video motion capture with artificial intelligence during the preseason period. This study assessed the knee flexion angles, knee valgus angles, hip flexion angles, and lower leg anterior inclination angle at 3 time points (initial contact, maximum flexion of the knee, and toe-off) and compared them between the dominant and nondominant legs. These angles were calculated from motion capture data and analyzed in 3 dimensions. A paired t test was used to analyze the differences between legs, and the significance level was set at P < .05. Results: The knee valgus angle at initial contact was greater in the nondominant leg (mean ± SD, 0.8°± 5.2°) than the dominant leg (−0.9°± 4.9°) ( P < .01). There were no differences between legs for any other angles at any of the time points. Conclusion: The kinematics of the dominant and nondominant legs of female soccer players in a single-leg DVJ differ in knee valgus angle. Clinical Relevance: Leg dominance is associated with the risk of sports injuries. Kinematic differences between the dominant and nondominant legs may be a noteworthy factor in elucidating the mechanisms and risk of sports injury associated with leg dominance.
Conventional coating tools have a high affinity for ductile materials, like aluminum alloy,
so cutting chips tend to adhere to cutting edge and work material surface. Therefore, chipping is
caused, and surface texture is degraded. In order to solve these problems, recently, DLC
(Diamond-Like-Carbon) has been applied to coating material. In this research, it is curried out
cutting of Aluminum alloy by the use of DLC coating tool, and examined influence of DLC coating
conditions on cutting characteristics. So far we have been concerned with the effect of type of
hydrocarbon gas (acethylene:C2H2, methane:CH4) on cutting. As a result, it is revealed that
cohesion of chips decreases, and surface roughness of work material improves in the case of
acethylene-DLC. On the other hand, internal stress is produced by deference in hardness between
tool surface and DLC film, and which is considered cause of film peeling [1]. Therefore, we
examined interlayer between DLC film and tool surface in order to relax of internal stress. As a
result, it was cleared that Titanium interlayer excels in adhesion.
Recently, wet blasting is generally used such as liquid honing and water jet machining in surface before plating of stainless steel. The outstanding feature of wet blasting is to prevent generation of static electric charge, to use micro abrasive grain, and to have cushioning for workpiece. On the other hand, the disadvantage of wet blasting is to generate corrosion of equipment and liquid waste under processing. Moreover, the using abrasive grain is available on a limited basis. In particular, improvement disposal of liquid waste under processing is crucial in the near future. This paper makes proposal for improvement of surface texture by utilizing dry blasting, and it conducts improvement of surface texture about martensite stainless steel (SUS420J2 In JIS), which is used in material for scale. In the previous report, it has been cleared that relationship between surface texture and wettability. In this report, adhesion of plating was measured by scratch test. As a result, it was cleared that availability of adhesion evaluation by utilizing wettability.
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