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1.
Elmar Weltin Albert Gollhofer Guillaume Mornieux 《European Journal of Sport Science》2016,16(2):182-189
In lateral reactive movements, core stability may influence knee and hip joint kinematics and kinetics. Insufficient core stabilisation is discussed as a major risk factor for anterior cruciate ligament (ACL) injuries. Due to the higher probability of ACL injuries in women, this study concentrates on how gender influences trunk, pelvis and leg kinematics during lateral reactive jumps (LRJs). Perturbations were investigated in 12 men and 12 women performing LRJs under three different landing conditions: a movable landing platform was programmed to slide, resist or counteract upon landing. Potential group effects on three-dimensional trunk, pelvic, hip and knee kinematics were analysed for initial contact (IC) and the time of peak pelvic medial tilt (PPT). Regardless of landing conditions, the joint excursions in the entire lower limb joints were gender-specific. Women exhibited higher trunk left axial rotation at PPT (women: 4.0 ± 7.5°, men: ?3.1 ± 8.2°; p = 0.011) and higher hip external rotation at both IC and PPT (p < 0.01). But women demonstrated higher knee abduction compared to men. Men demonstrated more medial pelvic tilt at IC and especially PPT (men: –5.8 ± 4.9°, women: 0.3 ± 6.3°; p = 0.015). Strategies for maintaining trunk, pelvis and lower limb alignment during lateral reactive movements were gender-specific; the trunk and hip rotations displayed by the women were associated with the higher knee abduction amplitudes and therefore might reflect a movement strategy which is associated with higher injury risk. However, training interventions are needed to fully understand how gender-specific core stability strategies are related to performance and knee injury. 相似文献
2.
整合ACL和NAT的网络安全实验设计 总被引：1，自引：0，他引：1
针对在计算机网络安全实验课程中访问控制列表(ACL)实验和网络地址转换(NAT)实验分散独立的现状,利用华为3Com公司的网络实验设备来实现整合ACL和NAT的网络安全实验,采用2种由易到难的网络拓扑结构,创造性地设计和实现了该实验方案。并且,结合了WWW、Telne、tFTP 3个服务器的安装和配置,以及R IP动态路由配置,既充分地验证实验结果的正确,又让学生深刻地认识了ACL和NAT的原理和作用。 相似文献
3.
目的:前交叉韧带断裂是体育运动中最常见的、严重的、治疗康复费高的膝关节运动损伤之一。研究目的是确定侧切和急停起跳动作对前交叉韧带运动生物力学特征的影响。方法:对男女各25名年龄在18~22岁的篮球运动员完成侧切和急停起跳动作时的下肢三维运动学、动力学和表面肌电特征进行采集和处理。运用2×2混合设计的双因素方差分析(ANOVA)对特征参数进行数理统计。结果:动作和性别对下肢水平向后地面反作用力、膝关节外翻力矩、膝关节内旋力矩、腘绳肌群肌电和压力中心到踝关节中心的水平距离具有显著性交互作用。结论与建议:所有篮球运动员完成侧切比急停起跳时膝关节伸膝力矩增加,这些差异使侧切动作发生ACL损伤的可能性更大。另外,仅男性篮球运动员进行侧切动作时更倾向于采用足跟着地方式、外翻力矩以及腘绳肌肌电更大。与男性相比,女性篮球运动员可能更容易导致ACL负荷增大。此外,在完成急停起跳动作中,男性篮球运动员比女性倾向于足尖着地且水平向后地面反作用力小。研究结果提示了在制定预防ACL损伤训练方案时,应根据不同动作和性别针对性地设计训练方式。 相似文献
4.
庄新妍 《内蒙古科技与经济》2007,(6)
21世纪以来,黑客们采用了一种新的十分难以防范的分布式拒绝服务攻击(DDoS),给很多知名网站和internet带来巨大的损失.本文从概念、攻击原理、攻击现象、攻击方式介绍了这种攻击方法,以及防御DDoS的措施. 相似文献
5.
Meghan L. Critchley Daniel J. Davis Michaela M. Keener Jacob S. Layer Margaret A. Wilson Qin Zhu 《Sports biomechanics / International Society of Biomechanics in Sports》2020,19(4):421-437
ABSTRACT The purpose was to quantify the effects of mid-flight whole-body and trunk rotation on knee mechanics in a double-leg landing. Eighteen male and 20 female participants completed a jump-landing-jump task in five conditions: no rotation, testing leg ipsilateral or contralateral (WBRC) to the whole-body rotation direction, and testing leg ipsilateral (TRI) or contralateral to the trunk rotation direction. The WBRC and TRI conditions demonstrated decreased knee flexion and increased knee abduction angles at initial contact (2.6 > Cohen’s dz > 0.3) and increased peak vertical ground reaction forces and knee adduction moments during the 100 ms after landing (1.7 > Cohen’s dz > 0.3). The TRI condition also showed the greatest knee internal rotation angles at initial contact and peak knee abduction and internal rotation angles and peak knee extension moments during the 100 ms after landing (2.0 > Cohen’s dz > 0.5). Whole-body rotation increased contralateral knee loading because of its primary role in decelerating medial-lateral velocities. Trunk rotation resulted in the greatest knee loading for the ipsilateral knee due to weight shifting and mechanical coupling between the trunk and lower extremities. These findings may help understand altered trunk motion in anterior cruciate ligament injuries. 相似文献
6.
Mitchell L. Stephenson Taylour J. Hinshaw Haley A. Wadley Qin Zhu Margaret A. Wilson Mark Byra 《Sports biomechanics / International Society of Biomechanics in Sports》2018,17(1):67-82
A variety of the available time to react (ATR) has been utilised to study knee biomechanics during reactive jump-landing tasks. The purpose was to quantify knee kinematics and kinetics during a jump-land-jump task of three possible directions as the ATR was reduced. Thirty-four recreational athletes performed 45 trials of a jump-land-jump task, during which the direction of the second jump (lateral, medial or vertical) was indicated before they initiated the first jump, the instant they initiated the first jump, 300 ms before landing, 150 ms before landing or at the instant of landing. Knee joint angles and moments close to the instant of landing were significantly different when the ATR was equal to or more than 300 ms before landing, but became similar when the ATR was 150 ms or 0 ms before landing. As the ATR was decreased, knee moments decreased for the medial jump direction, but increased for the lateral jump direction. When the ATR is shorter than an individual’s reaction time, the movement pattern cannot be pre-planned before landing. Knee biomechanics are dependent on the timing of the signal and the subsequent jump direction. Precise control of timing and screening athletes with low ATR are suggested. 相似文献
7.
Jeffrey B. Taylor Kevin R. Ford Randy J. Schmitz Scott E. Ross Terry A. Ackerman Sandra J. Shultz 《Journal of sports sciences》2018,36(21):2492-2501
Anterior cruciate ligament (ACL) injury prevention programmes have not been as successful at reducing injury rates in women’s basketball as in soccer. This randomised controlled trial (ClinicalTrials.gov #NCT02530333) compared biomechanical adaptations in basketball and soccer players during jump-landing activities after an ACL injury prevention programme. Eighty-seven athletes were cluster randomised into intervention (6-week programme) and control groups. Three-dimensional biomechanical analyses of drop vertical jump (DVJ), double- (SAG-DL) and single-leg (SAG-SL) sagittal, and double- (FRONT-DL) and single-leg (FRONT-SL) frontal plane jump landing tasks were tested before and after the intervention. Peak angles, excursions, and joint moments were analysed using two-way MANCOVAs of post-test scores while controlling for pre-test scores. During SAG-SL the basketball intervention group exhibited increased peak knee abduction angles (p = .004) and excursions (p = .003) compared to the basketball control group (p = .01) and soccer intervention group (p = .01). During FRONT-SL, the basketball intervention group exhibited greater knee flexion excursion after training than the control group (p = .01), but not the soccer intervention group (p = .11). Although women’s soccer players exhibit greater improvements in knee abduction kinematics than basketball players, these athletes largely exhibit similar biomechanical adaptations to ACL injury prevention programmes. 相似文献
8.
David Zahradnik Daniel Jandacka Michal Holcapek Roman Farana Jaroslav Uchytil Joseph Hamill 《Journal of sports sciences》2018,36(8):955-961
The number and type of landings performed after blocking during volleyball matches has been related to the potential risk of ACL injury. The aim of the present study was to determine whether gender affects the frequency of specific blocking landing techniques with potential risk of ACL injury from the perspective of foot contact and subsequent movement after the block used by volleyball players during competitive matches. Three matches involving four female volleyball teams (fourteen sets) and three matches involving four male volleyball teams (thirteen sets) in the Czech Republic were analyzed for this study. A Pearson chi-square test of independence was used to detect the relationship between gender and different blocking techniques. The results of the present study showed that gender affected single-leg landings with subsequent movement in lateral direction and double-leg landings. Although the total number of landings was lower for male athletes than for female athletes, a larger portion of male athletes demonstrated single leg landings with a subsequent movement than female athletes. Single leg landings with a subsequent movement have a higher potential risk of ACL injury. 相似文献
9.
Marco Freddolini Aluena Battaglioli Filippo Chiechi Giacomo Placella Anastasios Georgoulis Giuliano Cerulli 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(4):384-393
The purpose of the study was to evaluate whether using only the semitendinosus as a tripled short graft would affect the electromechanical delay (EMD) of the knee flexors. EMD was evaluated in volunteers (N = 15) after they had undergone surgery for anterior cruciate ligament (ACL) reconstruction where the semitendinosus tendon alone was used as a graft. The results were compared with the intact leg and healthy controls (N = 15). After warming up, each subject performed four maximally explosive isometric contractions on an isokinetic dynamometer. Torques were measured by the dynamometer, while the electrical activity of the semitendinosus and biceps femoris muscles was detected using surface electromyography. EMD was found to be significantly increased (p = 0.001) in patients who had undergone ACL reconstruction compared to the controls. On the contrary, no significant differences (p = 0.235) were found for the biceps femoris muscle between the two groups. Similar results were found when the study group was compared with the intact leg group (p = 0.027 for semitendinosus and p = 0.859 for biceps femoris). Harvesting the semitendinosus tendon increases the EMD for the semitendinosus muscle but does not influence the EMD outcomes for the biceps femoris muscle. 相似文献
10.
谢春明 《乐山师范学院学报》2003,18(4):106-110
WebSphere应用服务器使用户能够为Servlet的开发实现“一次写成，各处使用”的目的，Web服务器的配置被设置成将对JSP件的HTTP请求传递至WebSphere应用服务器，并有一套完整的安全设置的认证协议和方案，支持使用XML件来配置Servlet。 相似文献