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The purpose of this study was to examine the difference of kinematic skill characteristics between the Chinese and world elite female discus athletes. We used the methods of literature, three-dimensional video analysis, and mathematical statistics to compare and analyze the differences of some kinematic parameters between the three Chinese female discus athletes and four world female discus athletes. The result shows that the speed of discus release of the Chinese elite female discus athletes is lower (p < 0.05) than that of the world elite female discus athletes. Compared to the world elite female discus athletes, the height of release is higher (p < 0.05). But there was no significant difference in the angle of release (p > 0.05), rotation rhythm (p > 0.05), and discus speed increment (p > 0.05) in different stages during the throwing procedure from double support stage to delivery stage. The results may provide reference for the special technique training of the Chinese female discus throwers, so as to improve the discus throwing level of Chinese women. [ABSTRACT FROM AUTHOR]

Context: Comprehensive injury-prevention training (plyometric, agility, balance, and core-stability exercises) has been shown to decrease sport-related injury. The relationship between trunk control and sport-related injury has been emphasized; however, the isolated effects of core-muscle training are unclear. Objective: To investigate the effect of a simple 8-week core-muscle-training program on the neuromuscular control of the lower limb and trunk during jump landing and single-legged squatting. Design: Controlled laboratory study. Setting: Laboratory. Patients or Other Participants: Seventeen female collegiate basketball players were randomly divided into training (n= 9; age = 19.7 ± 0.9 years) and control (n = 8; age = 20.3 ± 2.5 years) groups. Intervention(s): The training group completed the coremuscle-training program in addition to daily practice, and the control group performed only daily practice. Kinematic and kinetic data during a drop-jump test and single-legged squat were acquired using a 3-dimensional motion-analysis system. Main Outcome Measure(s): Three-dimensional hip, knee, and trunk kinematics; knee kinetics; and isokinetic muscle strength were measured at the pretraining and posttraining phases. Results: For the drop-jump test, the maximal trunk-flexion angle increased (P=.008), and peak knee-valgus moment (P = .008) decreased in the training group. For the single-legged squat, the peak trunk-flexion angle increased (P = .04), and the total amount of trunk lateral-inclination angle (P=.02) and peak knee-valgus moment (P=.008) decreased in the training group. We observed no changes in the control group. Conclusions: A consecutive 8-week core-muscle-training program improved lower limb and trunk biomechanics. These altered biomechanical patterns could be favorable to preventing sport-related injuries. [ABSTRACT FROM AUTHOR]

Background Infants aged 2 to 5 months show spontaneous general movements (GMs) of the whole body, which are referred to as fidgety movements (FMs). Although previous studies have shown that evaluation of GMs by the General Movement Assessment (GMA) has predictive value about later neurological impairments, it remains unknown whether raters consistently perceive and rate such complex kinematic information. Objective The purpose of this study was to construct a method to reveal which movement features are associated with each rater's evaluation of FMs based on the GMA. Design GMA scores of 163 healthy infants aged 11 to 16 weeks postterm were matched with data obtained from a 3-dimensional motion analysis system. Methods Three physical therapists performed the GMA and classified GMs into 9 types, from which we focused on 3 subtypes differing in the temporal organization of FMs (continual, intermittent, and sporadic FMs). We also calculated 6 movement indices (average velocity of limb movements, number of movement units, kurtosis of acceleration, jerk index, average curvature, and correlation between limb velocities) for arms and legs for each infant and analyzed which movement indices were associated with the ratings of the 3 FM subtypes by each rater. Results Only the average curvature differed significantly among the ratings of the 3 FM subtypes for all 3 raters. Each rater showed significant differences in the average curvature in either arms or legs. Limitations It is difficult to generalize the present results to raters with various levels of expertise and experience in using the GMA. This issue calls for further research. Conclusions The method used revealed commonality and individuality about the perceived movement features that can be associated with the rating of FMs. [ABSTRACT FROM AUTHOR]

We aimed to quantify the inertial parameters of the lower trunk segment in pregnant Japanese women and compare kinetic data during tasks calculated with parameters estimated in this study to data calculated with standard parameters. Eight pregnant women and seven nulliparous women participated. Twenty-four infrared reflective markers were attached to the lower trunk, and the standing position was captured by eight infrared cameras. The lower trunk was divided into parts, and inertial parameters were calculated. Pregnant women performed a movement task that involved standing from a chair, picking up plates, and walking forward after turning to the right. Kinetic analysis was performed using standard inertial parameters and the newly calculated parameters. There were more significant differences between methods in the kinetic data at the latter stages of pregnancy. The inertial parameters calculated in this study should be used to ensure the validity of biomechanical studies of pregnant Japanese women. [ABSTRACT FROM AUTHOR]

Background: Achievement of very deep knee flexion after total knee arthroplasty (TKA) can play a critical role in the satisfaction of patients who demand a floor-sitting lifestyle and engage in high-flexion daily activities (e.g., seiza-sitting). Seiza-sitting is characterized by the knees flexed >145º and feet turned sole upwards underneath the buttocks with the tibia internally rotated. The present study investigated factors affecting the achievement of seiza-sitting after TKA using posterior-stabilized total knee prosthesis with high-flex knee design.Methods: Subjects comprised 32 patients who underwent TKA with high-flex knee prosthesis and achieved seiza-sitting (knee flexion >145º) postoperatively. Another 32 patients served as controls who were capable of knee flexion >145º preoperatively, but failed to achieve seiza-sitting postoperatively. Accuracy of femoral and tibial component positions was assessed in terms of deviation from the ideal position using a two-dimensional to three-dimensional matching technique. Accuracies of the component position, posterior condylar offset ratio and intraoperative gap length were compared between the two groups.Results: The proportion of patients with >3º internally rotated tibial component was significantly higher in patients who failed at seiza-sitting (41 %) than among patients who achieved it (13 %, p = 0.021). Comparison of intraoperative gap length between patient groups revealed that gap length at 135º flexion was significantly larger in patients who achieved seiza-sitting (4.2 ± 0.4 mm) than in patients who failed at it (2.7 ± 0.4 mm, p = 0.007). Conversely, no significant differences in gap inclination were seen between the groups.Conclusions: From the perspective of surgical factors, accurate implant positioning, particularly rotational alignment of the tibial component, and maintenance of a sufficient joint gap at 135º flexion appear to represent critical factors for achieving >145º of deep knee flexion after TKA. [ABSTRACT FROM AUTHOR]

The purpose of this study was to clarify the differences between adolescent and collegiate baseball pitchers in the kinematic and kinetic profiles of the trunk and lower limbs during the pitching motion. The subjects were thirty-two adolescent baseball pitchers aged 12-15 years (APG) and thirty collegiate baseball pitchers aged 18-22 years (CPG). Three-dimensional motion analysis with a comprehensive lower-extremity model was used to evaluate kinematic and kinetic parameters during baseball pitching. The ground reaction forces (GRFs) of the pivot and stride legs during pitching were determined using two multicomponent force plates. The joint torques of hip, knee, and ankle were calculated by the inverse-dynamics computation of musculoskeletal human models using motion-capture data. To eliminate any effect of variation in body size, kinetic and GRFs data were normalized by dividing them by body mass. The velocity of a pitched ball was significantly higher (p < 0.01) in CPG (35.2 ± 1.9 m⋅s-1) than in the APG (30.7 ± 2.7 m⋅s-1). Most kinematic parameters for the lower limbs were similar between the CPG and the APG. Maximum Fy (toward the throwing direction) on the pivot leg and Fy and resultant forces on the stride leg at ball release were significantly greater in the CPG than in the APG (p < 0.05). Hip and knee joint torques on the lower limbs were significantly greater in the CPG than in the APG (p < 0.05). The present study indicates that the kinematics of lower limbs during baseball pitching are similar between adolescent and collegiate pitchers, but the momentum of the lower limbs during pitching is lower in adolescent pitchers than in collegiate ones, even when the difference in body mass is considered. [ABSTRACT FROM AUTHOR]

We applied tomographic inversion and receiver function analysis to seismic data from ocean-bottom seismometers and land-based stations to understand the structure and its relationship with slow slip events off Boso, Japan. First, we delineated the upper boundary of the Philippine Sea Plate based on both the velocity structure and the locations of the low-angle thrust-faulting earthquakes. The upper boundary of the Philippine Sea Plate is distorted upward by a few kilometers between 140.5 and 141.0°E. We also determined the eastern edge of the Philippine Sea Plate based on the delineated upper boundary and the results of the receiver function analysis. The eastern edge has a northwest–southeast trend between the triple junction and 141.6°E, which changes to a north–south trend north of 34.7°N. The change in the subduction direction at 1–3 Ma might have resulted in the inflection of the eastern edge of the subducted Philippine Sea Plate. Second, we compared the subduction zone structure and hypocenter locations and the area of the Boso slow slip events. Most of the low-angle thrust-faulting earthquakes identified in this study occurred outside the areas of recurrent Boso slow slip events, which indicates that the slow slip area and regular low-angle thrust earthquakes are spatially separated in the offshore area. In addition, the slow slip areas are located only at the contact zone between the crustal parts of the North American Plate and the subducting Philippine Sea Plate. The localization of the slow slip events in the crust–crust contact zone off Boso is examined for the first time in this study. Finally, we detected a relatively low-velocity region in the mantle of the Philippine Sea Plate. The low-velocity mantle can be interpreted as serpentinized peridotite, which is also found in the Philippine Sea Plate prior to subduction. The serpentinized peridotite zone remains after the subduction of the Philippine Sea Plate and is likely distributed over a wide area along the subducted slab. [ABSTRACT FROM AUTHOR]

The lithospheric response to extension and the interaction of mantle and crust dynamics has been studied extensively in rift basins in a divergent continental setting. Despite the geometric similarities in extensional structures, back-arc rift basins that are a result of local extension in an overall convergent tectonic setting are commonly overlooked. Previous work on back-arc basins shows how the interplay between the subducting slab, the over-riding plate, and magmatism affects upper-crustal deformation and related sedimentation patterns, however, the controls on these processes during rifting remain unclear. Since natural hazards like earthquakes and tsunamis have been linked to movement along rift-related structures, there is a need to better understand the evolution of these extension related structures. The Sea of Japan is a Cenozoic back-arc rift basin that initiated from ~25 Ma due to the interaction of the Pacific and Philippine Sea plates subducting under the Eurasian plate. Rapid fan-shaped opening of the southern Sea of Japan with clock-wise rotation of SW Japan occurred between ~18 – 16 Ma. Here we investigate the evolution Tsushima Strait that connects the southern Sea of Japan with the Pacific Ocean. We evaluate extensive 2D seismic reflection, high-resolution gravity, and borehole data, in addition to previously published geological data from the surrounding region to (i) identify rift-related structures and features related to subsequent tectonic events, and (ii) reconstruct the palaeo-geography of the southern Sea of Japan region. We observe horsts and (half-) grabens with oblique components and negative flower structures. More than 5400 m of synrift sediments accumulated within ~2 Myr, containing benthic foraminifera suggesting a deepening marine environment, and pollen associated with a subtropical climate. This infers that during the rapid fan-shaped opening of the back-arc rift basin, a warm Tsushima current flowed into Sea of Japan and the local climate changed from warm to subtropic. From ~15 Ma, rift structures are abruptly inverted or cross-cut by thrust faults and wedge thrusts, with microfossils and pollen suggesting a fast decrease in palaeo-waterdepth and cooling climate, respectively. We propose that a tectonic sill developed at this time which cut off the subtropical Tsushima current to the Sea of Japan. Sub-horizontal Pliocene sediments covering the compressional structures suggest a weakening of the compressive stress from ~6 Ma. The development of the Sea of Japan back-arc rift basin can be seen into the context of regional Cenozoic plate dynamics around Japan. The abrupt change to a compressive stress regime from ~15 Ma may be related to the arrival at SW Japan of the young, hot Shikoku Basin that developed as a back-arc rift on the northern edge of the Philippine Sea plate that overrides the Pacific plate. The Pliocene weakening of compressional stress may be associated with a change in dynamics of the Shikoku Basin subducting under SW Japan. Our results suggest a complex interplay between local processes, specifically deformation in the overriding plate and evolving palaeo-geography, and regional plate kinematics during both extension and compression. [ABSTRACT FROM AUTHOR]