Joint work is not shifted proximally after a long run in rearfoot strike runners     

Jake A. Melaro  Allison H. Gruber 《Journal of sports sciences》2021,39(1):78-83

ABSTRACT

Distal-to-proximal redistribution of joint work occurs following exhaustive running in recreational but not competitive runners but the influence of a submaximal run on joint work is unknown. The purpose of this study was to assess if a long submaximal run produces a distal-to-proximal redistribution of positive joint work in well-trained runners. Thirteen rearfoot striking male runners (weekly distance: 72.6 ± 21.2 km) completed five running trials while three-dimensional kinematic and ground reaction force data were collected before and after a long submaximal treadmill run (19 ± 6 km). Joint kinetics were calculated from these data and percent contributions of joint work relative to total lower limb joint work were computed. Moderate reductions in absolute negative ankle work (p = 0.045, Cohen’s d = 0.31), peak plantarflexor torque (p = 0.004, d = 0.34) and, peak negative ankle power (p = 0.005, d = 0.32) were observed following the long run. Positive ankle, knee and hip joint work were unchanged (p < 0.05) following the long run. These findings suggest no proximal shift in positive joint work in well-trained runners after a prolonged run. Runner population, running pace, distance, and relative intensity should be considered when examining changes in joint work following prolonged running.  相似文献   

Could knee joint mechanics during the golf swing be contributing to chronic knee injuries in professional golfers?     

Howie Carson  Jim Richards  Simon G. S. Coleman 《Journal of sports sciences》2020,38(13):1575-1584

ABSTRACT

Full three-dimensional movements and external moments in golfers’ knees and the possible involvement in injuries have not been evaluated using motion capture at high sample frequencies. This study measured joint angles and external moments around the three anatomical axes in both knees of 10 professional golfers performing golf drives whilst standing on two force plates in a motion capture laboratory. Significant differences were found in the knee joint moments between the lead and trail limbs for the peak values and throughout all stages during the swing phase. A significantly higher net abduction moment impulse was seen in the trail limb compared with the lead limb (?0.518 vs. ?0.135 Nms.kg^?1), indicating greater loading over the whole swing, which could contribute to knee lateral compartment or anterior cruciate ligament injuries. A significant correlation (r = ?0.85) between clubhead speed at ball contact and maximum joint moment was found, with the largest correlations being found for joint moments at the top of the backswing event and at the end of the follow-through. Therefore, although knee moments can contribute to high clubhead speeds, the large moments and impulses suggest that they may also contribute to chronic knee injuries or exacerbate existing conditions.  相似文献   

Reviewing the Variability-Overuse Injury Hypothesis: Does Movement Variability Relate to Landing Injuries?     

Andrew D. Nordin  Janet S. Dufek 《Research quarterly for exercise and sport》2019,90(2):190-205

Purpose: Overuse injuries are common in sport, but complete understanding of injury risk factors remains incomplete. Although biomechanical studies frequently examine musculoskeletal injury mechanisms, human movement variability studies aim to better understand neuromotor functioning, with proposed connections between overuse injury mechanisms and changes in motor variability. Method: In a narrative review, we discuss the variability-overuse injury hypothesis, which suggests repeated load application leads to mechanical tissue breakdown and subsequent injury when exceeding the rate of physiological adaptation. Due to the multidisciplinary nature of this hypothesis, we incorporate concepts from motor control, neurophysiology, biomechanics, as well as research design and data analysis. We therefore summarize multiple perspectives while proposing theoretical relationships between movement variability and lower extremity overuse injuries. Results: Experimental data are presented and summarized from published experiments examining interactions between experimental task demands and movement variability in the context of drop landing movements, along with comparisons to previous movement variability studies. Conclusion: We provide a conceptual framework for sports medicine researchers interested in predicting and preventing sports injuries. Under performance conditions with greater task demands, we predict reduced trial-to-trial movement variability that could increase the likelihood of overuse injuries.  相似文献   

铝含量对Fe—30Mn—（1—9）Al合金阳极钝化性能影响的研究   总被引：2，自引：0，他引：2  

朱雪梅  张彦生 《科技通报》1992,8(4):197-200

采用阳极极化测量、俄歇能谱仪与X射线光电子谱仪研究了Fe-30Mn-(1～9)Al系奥氏体合金在1mol/L Na_2SO_4介质中的电化学腐蚀行为与钝化膜.在弱酸性介质(pH=5.55),中,随Al含量增加,自腐蚀电位E(corr)升高,自腐蚀电流密度I_(corr)减小,Al量增至5％,合金呈现钝化.Al是钝性元素,形成以Al_2O_3为主要组分的钝化膜.因此,增加Al含量,可以显著提高Fe-Mn-Al合金的耐腐蚀性能.  相似文献   

BMD and Serum Intact Osteocalcin in Postmenopausal Osteoporosis Women     

Jagtap VR  Ganu JV  Nagane NS 《Indian journal of clinical biochemistry : IJCB》2011,26(1):70-73

India seems to have the highest prevalence of osteoporosis. With growing awareness of osteoporosis and its impact on life span especially in India, special attention is being paid to early detection, management and treatment of postmenopausal osteoporosis in women. Measurement of BMD and osteocalcin are of value in estimating bone turnover rates. The aim of this study is (1) to measure the specific, sensitive bone formation marker such as osteocalcin and BMD in postmenopausal osteoporosis women and postmenopausal non-osteoporosis women; (2) the follow up study to evaluate the impact of specific antiresorptive therapy (alendronate + calcium + vitamin D) regimen in postmenopausal osteoporosis by assaying osteocalcin and BMD. Sixty clinically diagnosed postmenopausal osteoporosis patients and 60 normal subjects (postmenopausal non-osteoporosis women) were recruited as control. Mean bone mineral density T score and Z score was significantly decreased (P < 0.001) in postmenopausal osteoporosis patients as compared to controls. Highly significant increase in the mean score of BMD—T score and Z score from baseline to post therapy of 3 months was observed in postmenopausal osteoporosis women. Serum osteocalcin levels were significantly increased (P < 0.001) as compared to control group. Serum osteocalcin levels were decreased significantly (P < 0.001) from baseline to post therapy of 3 months in postmenopausal osteoporosis women. BMD is the best quantifiable predictor of osteoporotic fracture and osteocalcin is specific, sensitive, promising, currently used marker for better prognosis of osteoporosis and for monitoring responses to antiresorptive therapy.  相似文献   

空间密度聚类在数字图书馆图像检索中的应用     

王华秋  王重阳  聂珍 《现代情报》2016,36(2):129-134

图像聚类为数字图书馆图像管理提供了新的技术支持,能够在大量图像数据中发掘使用户感兴趣的信息。传统应用于图像聚类的特征提取算法往往忽略图像颜色的空间分布信息,且适应性较差。通过等面积矩形环对图像进行划分并计算各空间区域的相关性,并根据空间区域相关性计算各区域的重要性,将空间信息与颜色信息进行融合。同时对快速搜索密度峰值聚类算法的截断距离进行了合理改进,在保证聚类精度的同时提高收敛速度。最后将该密度聚类算法应用于数字图书馆图像检索之中。通过实验验证,本文提出的方法是可行的、有效的。  相似文献   

等离子体天线轴向密度数值模拟和辐射图计算     

赵国伟  王之江  徐跃民  梁志伟  徐杰 《中国科学院研究生院学报》2007,24(4):419-424

由于电子密度分布、激励功率、气压等因素的影响，等离子体天线参数（增益、方向图等）通常难以求解。本文利用时域差分建立电磁波沿等离子体天线激励和传播的模型，得到不同参数（如激励功率、碰撞频率、等离子体迟豫时间、每个电子对所需能量）对等离子体轴向电子密度分布的影响，解释了不同激励情况下电子密度的线性和非线性分布，并解决了信号沿等离子体天线传播的波矢分布、辐射方向图的求解问题。  相似文献   

藏成药七十味珍珠丸中矿物质元素在体内蓄积性水平研究   总被引：1，自引：0，他引：1  

李天才  索有瑞 《中国科学院研究生院学报》2003,20(3):348-352

名贵藏成药七十味珍珠丸是传统藏药的典型代表,疗效显著.其中矿物类药的大量运用为现代医学科学不可理喻,给传统藏医药学的健康发展带来了困惑。以金诃七十味珍珠丸为研究材料,以Wistar大白鼠为试验对象,用等离子体发射光谱(ICP AES)和氢化物原子吸收光谱(HAAS)等分析仪器,测定了对照组和给药组实验动物在连续 1 8周试验期间心、肝、肾等组织器官中的矿物质元素含量水平,阐述金诃七十味珍珠丸中矿物质元素在动物主要组织器官中的长期蓄积性及其对生物机体的毒性效应  相似文献   

硅土充填高聚物的性能研究   总被引：1，自引：0，他引：1  

潘建强  李长江 《科技通报》1996,12(3):139-142

探讨了硅土的矿物学特性及其对充填高聚合物的影响，研究表明，天然超细粒度（０．０１－０．００１ｍｍ）复合矿物的及独特的粒－片叠置结构是导致硅土在高聚合物中具有良好增强性能的主要原因。  相似文献   

单烯烃的密度与其分子结构之间关系的探讨     

王克强 《科技通报》1993,9(2):96-99

根据分子结构的特点,用结构信息法探讨了单烯烃的密度与其分子结构之间的关系,提出了一个结构基础明确的定量关系.对149种单烯烃的计算表明,计算值与实验值之间的一致性令人满意,平均误差0.518％。应用本文定量关系,不仅能够预测烯烃的密度,而且有助于揭示物质结构性能关系之间的奥秘。  相似文献