Rearward-Facing Infant Child Restraint Systems with Support Legs in Frontal and Frontal-Oblique Impacts

Previous studies of support legs in rearward-facing infant CRS models have focused on frontal impacts and have found that the presence of a support leg is associated with a reduction in head injury metrics. However, real-world crashes often involve an oblique principal direction of force. The current study used sled tests to evaluate the effectiveness of support legs in rearward-facing infant CRS models for frontal and frontal-oblique impacts with and without a simulated front row seatback. Frontal and frontal-oblique impact sled tests were conducted using the simulated Consumer Reports test method with and without the blocker plate, which was developed to represent a front row seatback. The Q1.5 anthropomorphic test device (ATD) was seated in rearward-facing infant CRS models, which were tested with and without support legs. The presence of a support leg was associated with significant reductions of head injury metrics below injury tolerance limits for all tests, which supports the findings of previous studies. The presence of a support leg was also associated with significant reductions of peak neck tensile force. The presence of the blocker plate resulted in greater head injury metrics compared to tests without the blocker plate, but the result was non-significant. However, the fidelity of the interaction between the CRS and blocker plate as an adequate representation of the interaction that would occur in a real vehicle is not well understood. The findings from the current study continue to support the benefit of support legs in managing the energy of impact for a child in a rearward-facing CRS.

Both Upper and Lower Limb Movements Contribute to Aesthetics of the Piqué Arabesque in Ballet

This study aimed to identify the factor structures—which are the predominant frameworks for describing the basic dimensions of a concept—that contribute to the aesthetics of body position in ballet. This study was composed of three-dimensional movement analysis and subjective evaluation. Fourteen ballet dancers participated in the three-dimensional movement analysis. Thirty-six reflective markers were attached to the dancers’ bodies, after which the dancers performed a piqué arabesque, a position in which the weight transfers from one leg to the other. This movement was captured using eight optical cameras and one video camera. Biomechanical parameters, such as the joint angle and velocity of each body part, were calculated from the coordinates of the markers. Twenty-eight videos recorded in the three-dimensional movement analysis were viewed by 51 observers with ballet experience. The observers subjectively evaluated the videos through four category pairs—“beautiful-ugly,” “like-dislike,” “interesting-not interesting,” and “good-bad”—on a five-point semantic differential scale. Two groups, the top and bottom 30%, were extracted based on the “beautiful-ugly” rating and compared using an independent t-test. In addition, exploratory factor analysis was performed on the biomechanical parameters that showed significant differences. Five factors were identified: “stability of the right distal upper limb and upper body,” “torso displacement speed,” “stability of the left distal upper limb and line of the support leg,” “height of the gesture leg,” and “stability of the support leg around the hip joint and line of the limbs on the gesture leg side.” These results indicate that the movements of both upper and lower limbs contributed to the aesthetics of the ballet position of piqué arabesque. These findings will be useful for ballet teachers and dancers to understand the intrinsic aesthetics of movements.

KINEMATICAL CHARACTERISTICS OF ACCURATE PENALTY-KICKING FOR TURKISH FOOTBALL PLAYERS IN GOALKEEPER CONFRONTATION

This study aimed to analyze the kinematical characteristics values of accurate penalty-kicking for Turkish football players in goalkeeper confrontation. Fifteen male Turkish Regional Amateur League players (Age: 21.08± 1.56 years old) was scanned, by two video cameras synchronous in two-dimensional (2D), placed at optical axes X&Y. the best three tries of penalty kicking performance were analyzed by video analysis Dartfish 9.0 software. Standard statistical methods were used for the calculation of mean±sd, Pearson test for the correlations between all variables. A value of p-value ≤ 0.05 was considered a threshold of statistical significance. The results were shown in the ball contact phase that the distance pivot foot & ball factor has a statistically significant effect in producing accuracy (p-value=.001), and the interaction between two main factors namely the trunk and inclination body angles has a statistically significant effect with a p-value≤.05 in producing accuracy too. In addition, in the followthrough phase, we can see too the statistically significant effect in p-value≤.005 of the trunk angle, and in pvalue≤.05 of the thighs angle in producing accuracy. As a conclusion, it can be conveyed that the distance between the support leg and the ball is very decisive for the kinematic profile formed such as contraction of the abdominal muscles (trunk angle), the amortization process (the pivot leg angle), shot power (angle and length of the shot leg swing trajectory), where these aspects are significantly affected to the shot power, ball velocity and the level of accuracy.

Biomechanics of accurate and inaccurate goal-kicking in Australian football: Group-based analysis

Goal-kicking is an important skill in Australian Football (AF). This study examined whether kinematic differences exist between accurate and inaccurate goal-kicks and determined the relationships between technical factors and accuracy. Eighteen elite to sub-elite AF players performed 15 x 30 m goal-kicks on an AF training ground, with three-dimensional kinematics collected using the Xsens inertial measurement system (Xsens Technologies B.V., Enschede, the Netherlands). A general linear mixed modelling approach and regression-based statistics were employed to quantify differences between accurate and inaccurate goal kicks and the relationships between technical factors and accuracy. Accurate goal-kicks were characterised by a straighter approach line, with less kick-leg joint range of motion (knee and hip), lower linear velocity (centre of mass, foot speed), angular velocity (knee and shank), and less support-leg knee flexion during the kicking phase compared to inaccurate goal-kicks. At the end of the follow through, players produced greater ankle plantarflexion and a straighter-leg line in accurate goal-kicks. Findings in this research indicated that many factors interact with goal-kicking accuracy in AF, ranging from the players’ approach line path, their support-leg mechanics, the kick-leg swing motion, to the final position of the kicker during their follow through.

Attitude Trajectory Optimization to Ensure Balance Hexapod Locomotion

This paper proposes a simple attitude trajectory optimization method to enhance the walking balance of a large-size hexapod robot. To achieve balance motion control of a large-size hexapod robot on different outdoor terrains, we planned the balance attitude trajectories of the robot during walking and introduced how leg trajectories are generated based on the planned attitude trajectories. While planning the attitude trajectories, high order polynomial interpolation was employed with attitude fluctuation counteraction considered. Constraints that the planned attitude trajectories must satisfy during walking were well-considered. The trajectory of the swing leg was well designed with the terrain attitude considered to improve the environmental adaptability of the robot during the attitude adjustment process, and the trajectory of the support leg was automatically generated to satisfy the demand of the balance attitude trajectories planned. Comparative experiments of the real large-size hexapod robot walking on different terrains were carried out to validate the effectiveness and applicability of the attitude trajectory optimization method proposed, which demonstrated that, compared with the currently developed balance motion controllers, the attitude trajectory optimization method proposed can simplify the control system design and improve the walking balance of a hexapod robot.

Features of the spatial organization of the body in athletes of various qualifications when hitting the ball in football

The article analyzes the angular characteristics of football players of different qualifications in the extreme phases of the impact of the middle part of the foot on a stationary ball. The angles of the knee, hip, shoulder, elbow joints involved in the impact are considered. Their quantitative values, changes and differences between them are determined. Analyzing the quantitative characteristics of the angles at different moments of the phases when performing a shot on the ball is established. Highly qualified football players have a pronounced coordination of movements in the corners of the lower extremities. In the first phase, the blow is performed due to movement in the hip joint, ending in the knee. In this case, athletes effectively use the movement in the shoulder joint in the initial phase of the impact to increase its strength. Movement in the elbow joint in the final phase to maintain balance. In low-skilled players, the coordination of movements is disturbed, both joints of the legs are equally involved in the first phase of the blow. The movement of the hands does not occur, the shoulder and elbow joints are connected only in the final phase of the movement. It is established that the angular characteristics of the knee, hip and elbow joints in the micro-phase of the support leg of the preparation phase have statistically significant differences. Also in the micro-phase shock motion of the working phase there are statistically significant differences in all four angles analyzed by us.

Feasibility of evaluating effects of muscle fatigue on postural stability and muscular activation of the supporting leg in the soccer power kicking

Muscle fatigue accumulated during a soccer game can be a critical element to athletic performance. The aim of this study was to analyze the feasibility of evaluating the effect of muscle fatigue of the support leg in soccer players postural stability and muscular activation of the stabilizing muscles of the ankle in the performance of a power kick. Six university soccer players were evaluated. Muscular fatigue was induced by means of repeated oscillations of the swing leg. Results indicated that fatigue did not significantly affect velocity of the kicking leg and postural stability while kicking. Electromyographic analysis revealed that fatigue induced decreased activation of the medial gastrocnemius and increased activation of the soleus muscles in the period following foot-ball contact. These results show the feasibility of analyzing the effect of fatigue on dynamic balance and muscular activation in the performance of a power kicking task.