Effects of forward trunk lean on hamstring muscle kinematics during sprinting     

Ayako Higashihara  Yasuharu Nagano  Kazumasa Takahashi  Toru Fukubayashi 《Journal of sports sciences》2015,33(13):1366-1375

This study aimed to investigate the effects of forward trunk lean on hamstring muscle kinematics during sprinting. Eight male sprinters performed maximal-effort sprints in two trunk positions: forward lean and upright. A three-dimensional musculoskeletal model was used to compute the musculotendon lengths and velocity of the biceps femoris long head, semitendinosus, and semimembranosus muscles during the sprinting gait cycle. The musculotendon lengths of all the three hamstring muscles at foot strike and toe-off were significantly greater during the forward trunk lean sprint than during the upright trunk sprint. In addition, a positive peak musculotendon lengthening velocity was observed in the biceps femoris long head and semimembranosus muscles during the late stance phase, and musculotendon lengths at that instant were significantly greater during the forward trunk lean sprint than during the upright trunk sprint. The present study provides significant evidence that a potential for hamstring muscle strain injury involving forward trunk lean sprinting would exist during the stance phase. The results also indicate that the biceps femoris long head and semimembranosus muscles are stretched during forward trunk lean sprinting while contracting eccentrically in the late stance phase; thus, the elongation load on these muscles could be increased.  相似文献   

Increasing plantarflexion angle during landing reduces vertical ground reaction forces,loading rates and the hip’s contribution to support moment within participants     

K. Michael Rowley  James G. Richards 《Journal of sports sciences》2015,33(18):1922-1931

The ankle joint’s role in shock absorption during landing has been researched in many studies, which have found that landing with higher amounts of plantarflexion (PF) results in lower peak vertical ground reaction forces and loading rates. However, there has not yet been a study that compares drop landings within participants along a quantitative continuum of PF angles. Using a custom-written real-time feedback program, participants adjusted their ankles to an instructed PF angle and dropped onto two force platforms. For increasing PF, peak ground reaction force and peak loading rate during weight acceptance decreased significantly. The hip’s contribution to peak support moment decreased as PF at initial contact increased up to 30°. The ankle and knee contributions increased over this same continuum of PF angles. There appears to be no optimal PF angle based on peak ground reaction force and loading rate measurements, but there may be an optimum where joint contributions to peak support moment converge and the hip moment’s contribution is minimised.  相似文献   

Finale furioso: referee-biased injury times and their effects on home advantage in football     

Dennis Riedl  Bernd Strauss  Andreas Heuer  Oliver Rubner 《Journal of sports sciences》2015,33(4):327-336

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Effects of changing speed on knee and ankle joint load during walking and running     

Ana Cristina de David  Felipe Pivetta Carpes  Darren Stefanyshyn 《Journal of sports sciences》2015,33(4):391-397

Joint moments can be used as an indicator of joint loading and have potential application for sports performance and injury prevention. The effects of changing walking and running speeds on joint moments for the different planes of motion still are debatable. Here, we compared knee and ankle moments during walking and running at different speeds. Data were collected from 11 recreational male runners to determine knee and ankle joint moments during different conditions. Conditions include walking at a comfortable speed (self-selected pacing), fast walking (fastest speed possible), slow running (speed corresponding to 30% slower than running) and running (at 4 m · s^?1 ± 10%). A different joint moment pattern was observed between walking and running. We observed a general increase in joint load for sagittal and frontal planes as speed increased, while the effects of speed were not clear in the transverse plane moments. Although differences tend to be more pronounced when gait changed from walking to running, the peak moments, in general, increased when speed increased from comfortable walking to fast walking and from slow running to running mainly in the sagittal and frontal planes. Knee flexion moment was higher in walking than in running due to larger knee extension. Results suggest caution when recommending walking over running in an attempt to reduce knee joint loading. The different effects of speed increments during walking and running should be considered with regard to the prevention of injuries and for rehabilitation purposes.  相似文献   

Chlorogenic acid prevents acetaminophen-induced liver injury: the involvement of CYP450 metabolic enzymes and some antioxidant signals     

Chun Pang  Yu-chen Sheng  Ping Jiang  Hai Wei  Li-li Ji 《Journal of Zhejiang University. Science. B》2015,16(7):602-610

Chlorogenic acid (CGA), a polyphenolic compound, is abundant in fruits, dietary vegetables, and some medicinal herbs. This study investigated the prevention of CGA against acetaminophen (AP)-induced hepatotoxicity and its engaged mechanisms. CGA reversed the decreased cell viability induced by AP in L-02 cells in vitro. In addition, CGA reduced the AP-induced increased serum levels of alanine/aspartate aminotransferase (ALT/AST) in vivo. The effect of CGA on cytochrome P450 (CYP) enzymatic (CYP2E1, CYP1A2, and CYP3A4) activities showed that CGA caused very little inhibition on CYP2E1 and CYP1A2 enzymatic activities, but not CYP3A4. The measurement of liver malondialdehyde (MDA), reactive oxygen species (ROS), and glutathione (GSH) levels showed that CGA prevented AP-induced liver oxidative stress injury. Further, CGA increased the AP-induced decreased mRNA expression of peroxiredoxin (Prx) 1, 2, 3, 5, 6, epoxide hydrolase (Ephx) 2, and polymerase (RNA) II (DNA directed) polypeptide K (Polr2k), and nuclear factor erythroid-2-related factor 2 (Nrf2). In summary, CGA ameliorates the AP-induced liver injury probably by slightly inhibiting CYP2E1 and CYP1A2 enzymatic properties. In addition, cellular important antioxidant signals such as Prx1, 2, 3, 5, 6, Ephx2, Polr2k, and Nrf2 also contributed to the protection of CGA against AP-induced oxidative stress injury.  相似文献   

Legitimizing the Wound: Mapping the Military's Diagnostic Discourse of Traumatic Brain Injury     

Tom Lindsley 《Technical Communication Quarterly》2015,24(3):235-257

Following reports spanning from the beginning of the OEF (Operation Enduring Freedom) and OIF (Operation Iraqi Freedom) conflicts to the early 2010s, this rhetorical investigation analyzes the U.S. military's diagnostic practices used to identify mild traumatic brain injury (mTBI) in blast-affected troops. Considering the notion of “wound/injury” as a possible boundary object, this paper discusses how the conceptual framing of “invisible” injuries may produce interruptions of distrust that inhibit effective diagnosis.  相似文献   

功能性训练及其在运动损伤预防中的作用研究——以青少年篮球运动员为例     

陈杰  陈月亮  王沂  吴佳伟 《黄石理工学院学报(人文社科版)》2015,(2):83-86

文章运用文献资料等研究方法,就功能性训练的特点及其在青少年篮球运动员运动损伤预防中的作用进行了分析。功能性训练强调完整功能链、强调动作模式训练等理念,具有"与传统力量训练良性互补"、"注重训练过程诊断"和"强调动作模式设计"等特点,对预防青少年篮球运动员的弱链损伤、机体力量发展不平衡和技术动作不正确等问题具有积极作用,应引起运动员和教练员的高度关注。  相似文献   

新兵体能训练的伤病防护     

王向前  黄为根 《军事体育进修学院学报》2014,33(3):39-41

新兵体能训练中训练伤病发生率高于老兵,严重影响了训练效果。为了预防训练伤病,应从准备活动、放松恢复、补充营养、科学施训等方面做好伤病防护,切实提高体能训练效果,保护新兵身体健康。  相似文献   

改变多年冻土环境导致冻害发生的机理及防治研究     

王益良  王彪  郭景富 《黑龙江科技信息》2014,(18):192-193

我国漠河——大庆原油管道段工程沿线经过多年冻土地段,多年冻土环境的改变导致冻害发生的原因和机理,采取行之有效的防治措施,保护多年冻土环境的稳定,是解决和减少多年冻土地区建造原油管道不发生冻害的关键。  相似文献   

女子足球运动员踝关节损伤的调查与分析     

刘飞 《体育科技》2014,(6):92-93

通过文献资料方法、调查问卷法等相关方法,对女子足球运动员的运动损伤的进行调查分析,结果显示女子足球运动员的踝关节损伤者较为普遍。对运动损伤的原因进行分析,并提出了相应的预防措施,加强健康保健意识等预防治疗措施,旨在一定程度上减少女子足球运动员的损伤发生。以最大限度减少足球运动中的踝关节损伤。  相似文献