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31.
AbstractThe mechanics of cutting movements have been investigated extensively, but few studies have considered the rapid deceleration phase prior to turning which has been linked to muscle damage. This study used accelerometry to examine the influence of turning intensity on the last three steps of a severe turn.Ten soccer players performed 135° “V” cuts at five different intensities. Resultant decelerations were recorded from a trunk-mounted tri-axial accelerometer. Lower limb kinematics and ground reaction forces (GRF) from the pivot foot-ground contact (FGC) were also monitored.Average peak trunk decelerations were larger at the two preceding steps (4.37 ± 0.12 g and 4.58 ± 0.11 g) compared to the PIVOT step (4.10 ± 0.09 g). Larger peak joint flexion angular velocities were observed at PRE step (ankle: 367 ± 192 deg.s?1; knee 493 ± 252 deg.s?1) compared to PIVOT step (ankle 255 ± 183 deg.s?1; knee 377 ± 229 deg.s?1). Turn intensity did not influence peak GRF at PIVOT step.This study highlights the importance of steps prior to turning and their high-frequency loading characteristics. It is suggested that investigations of lower limb loading during turning should include this deceleration phase and not focus solely on pivot FGC. 相似文献
32.
Pedro B. Júdice João P. Magalhães Catarina N. Matias Luís B. Sardinha 《Journal of sports sciences》2013,31(19):1760-1767
AbstractOverweight and obesity are defined as abnormal or excessive fat accumulation that presents a health risk. Even in athletes an increased adiposity affects health and performance. Sedentary behaviour has been associated with higher levels of adiposity, independent of moderate-to-vigorous physical activity. However, it is unclear whether this independent relationship still exists in highly trained athletes. The aim of this study was to examine the association of sedentary behaviour with body fatness in elite athletes. Cross-sectional data from 82 male athletes (mean age 22 years) were used. Total and regional body composition was measured by dual energy X-ray absorptiometry. Self-reported time spent in sedentary behaviour and weekly training time was assessed in all participants at one time point and multiple regression analyses were used. Sedentary behaviour predicted total fat mass (β = 0.77; 95% CI: 0.36–1.19, P < 0.001) and trunk fat mass (β = 0.25; 95% CI: 0.07–0.43, P = 0.007), independent of age, weekly training time, and residual mass (calculated as weight-dependent variable) but not abdominal fat. Also, no associations of sedentary behaviour with fat-free mass, appendicular lean soft tissue, and body mass index were found. These findings indicate that athletes with higher amounts of sedentary behaviour presented higher levels of total and trunk fatness, regardless of age, weekly training time, and residual mass. Therefore, even high moderate-to-vigorous physical activity levels do not mitigate the associations between sedentary behaviour and body fatness in highly trained athletes. 相似文献
33.
为了探究躯干转动在背越式跳高起跳、腾空阶段的生物力学规律,采用文献资料法、影像分析法、数理统计法等研究方法,对国内9名优秀男子跳高运动员进行运动学分析。研究结果显示：运动员起跳过程中3个时间点躯干纵轴与Y轴的夹角均值分别为(74.8±1.9）°、(81.3±1.9)°、(92.5±2.0)°;躯干三环节与XOY面夹角减小和增加的顺序（由快到慢）是：胸部段>腹部段>髋部段。研究认为：起跳离地瞬间适宜的躯干纵轴外倾角度（92°左右）除了可以避免身体碰触横杆和提高身体垂直速度外,还可以使身体获得足够的翻转角动量;在起跳和腾空过杆过程中,肩部发挥了引领作用。 相似文献
34.
本文中采用2,4-二硝基苯肼(DNPH)与醛酮类化合物生成衍生物,利用高效液相色谱仪进行分析,掌握了交通干线周边空气中醛酮类化合物浓度变化特征,为今后非常规有机污染物排放标准的制定提供依据和参考。 相似文献
35.
Natsuki Sado Shinsuke Yoshioka Senshi Fukashiro 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(2):258-271
The purpose of this study was to investigate the effect of lumbosacral kinetics on sprinting. Twelve male sprinters performed 50 m sprints at maximal effort. Kinematic and ground reaction force data were recorded at approximately 40 m from sprint commencement. A whole-body inverse dynamics approach was applied to calculate joint forces and torques at the hip and lumbosacral joints. The contribution of the hips and lumbosacral joint torques to pelvic rotation was subsequently calculated, with joint force powers indicating the rate of mechanical energy transfer between segments across joint centres calculated for both hip joints. The kinetic analysis indicated that the lumbosacral torsional torque contributed significantly to pelvic rotation. Additionally, the pelvic rotation exerted anterior–posterior joint forces on the hips, contributing to the large positive joint force power at the hip of the stance leg. These hip joint force powers assisted in motion recovery during sprinting. In conclusion, the lumbosacral torsional torque might contribute to the recovery motion in sprinting through application of the anterior–posterior joint forces at the hip joints via pelvic rotation. 相似文献
36.
电路模拟数字综合实验箱的研制 总被引：5，自引：0，他引：5
介绍电路模拟数字（DMS）综合实验箱的研制目的,简叙了该综合实验箱的设计思想和总体方案设计,以及所能开设的实验。 相似文献
37.
男子标枪运动员张连标投掷技术分析 总被引：3，自引：0，他引：3
康利则 《西安体育学院学报》1999,16(3):5100
通过对张连标掷标枪技术的分析,从助跑距离、助跑速度的变化以及最后用力过程中身体重心速度、标枪速度和运动员身体姿势角等变量,揭示我国优秀男子标枪运动员的投掷技术水平。 相似文献
38.
目的:描述艺术体操运动员完成专项动作过程中的脊柱形态,结合躯干侧屈肌力的对称性特征,讨论专项动作和躯干肌力对脊柱产生的不对称负荷特征及其对脊柱曲度异常的影响。方法:红外动作捕捉系统获取脊柱椎体三维坐标,曲线拟合脊柱弯曲状态;等长肌力测试系统获得躯干两侧侧屈肌肉峰值力矩;配对t检验比较左右对称性,计算对称系数分析脊柱弯曲形态与肌肉力量的关联。结果:后扳腿动作脊柱矢状面上曲率最大椎体位置在左、右后扳腿两种情况之间存在显著相关(p=0.003),后扳、侧扳腿动作脊柱额状面上曲率最大值和对应椎体位置左右侧间均未发现显著相关、亦无显著差异。躯干处于同15°位、反15°位和反30°位进行侧屈时,右屈的肌肉峰值力矩显著大于左屈。脊柱弯曲曲率最大值和椎体位置的两侧对称系数与侧屈肌力对称系数之间均未发现显著相关。结论:艺术体操专项动作对脊柱矢状面的影响更显著,与脊柱额状面的曲度异常无直接关联。对于已经存在脊柱曲度异常的艺术体操运动员来说,不能通过对躯干侧屈肌肉力量进行对称性训练的方式,直接调整专项动作已对脊柱产生的不对称影响。 相似文献
39.
Jason Wicke David W. Keeley Gretchen D. Oliver 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(4):315-323
Coaches teach proper mechanics at a young age in an effort to increase pitching efficiency (i.e., proper pitching mechanics). Unfortunately, the mechanics taught to beginning pitchers are based on the findings from adult pitchers and may result in techniques that are detrimental to younger pitchers. The purpose of this study was to compare kinematics published for pitchers across various ages in an effort to determine whether the pitching techniques vary across developmental periods. A meta-analysis of papers published describing pitching kinematics for youth and adult pitchers was conducted. Maximal rotational velocity of the trunk and maximum external rotation of the shoulder were observed during the arm cocking phase. Peak magnitudes for abduction, horizontal adduction, and shoulder internal rotation were observed during the deceleration phase of the movement. In addition, by comparing previously published data across youth and adult pitchers, valuable insight into the differences in mechanics was gained. The results demonstrated that there are some distinct differences between youth and adult pitching mechanics. This finding may allow increased focus to be applied to those parameters observed to differ across age, increasing the knowledge base available for coaches to properly instruct youth pitchers. 相似文献
40.
Yasuharu Nagano Hirofumi Ida Masami Akai Toru Fukubayashi 《Journal of sports sciences》2013,31(14):1525-1534
Abstract Female athletes are considered to exhibit knee and trunk motion that is characteristic of anterior cruciate ligament (ACL) injury. The aim of this study was to examine the in vivo motion of the trunk and knee during a cutting manoeuvre and determine the relationship between them. All participants (10 male and 10 female college athletes) performed a shuttle run cutting task with the left limb. Trunk inclination (forward and lateral) and knee joint angles (flexion/extension, abduction/adduction, and internal/external tibial rotation) were calculated. Differences between the sexes and associations between knee motion and trunk inclination were examined. An increase in trunk forward inclination was strongly correlated with an increase in knee flexion angle and moderately correlated with a decrease in the excursion of internal tibial rotation. An increase in right trunk lateral inclination was moderately correlated with an increase in excursion of internal tibial rotation. The results also showed differences between the sexes in trunk forward inclination, lateral inclination, and knee flexion angle, but no such differences in knee abduction or internal tibial rotation. Trunk inclination is related to knee flexion and excursion of internal tibial rotation. Female athletes demonstrate a low trunk forward inclination and knee flexion angle, a posture that resembles that of ACL injury. 相似文献