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101.
CR Duffy D Stewart F Pecoraro PE Riches D Farina A Macaluso 《Journal of sports sciences》2012,30(12):1311-1321
Abstract To investigate the effects of ageing on the neural control strategies governing sprint cycling on a friction-loaded cycle-ergometer, 10 older (aged 70-83yr) and 8 young (aged 19-35yr) healthy women completed seven 6-s all-out cycling trials against varying loads. Root mean square (RMS), median frequency and muscle fibre conduction velocity were determined from the vastus lateralis of the dominant limb during each pedal stroke. Peak power was 43% lower in the older group compared to the younger (p?0.001) and was accompanied by a significantly lower RMS (p?0.05). No differences were observed in the other electromyography (EMG) parameters between the groups (p?>?0.05). ΔRMS from the first to the sixth second during each trial was found to increase significantly with the development of power output in both groups (p?0.05). For the first time during an all-out 6-s cycle trial, it has been demonstrated that older women's lower mechanical power output was accompanied by a significantly lower RMS, which indicates a decline in either the number of active of motor units or a reduced discharge rate. Hence, changes in motor units can be regarded as a contributory factor to the decline of muscle power with advancing age. Overall, though, similar neural strategies are adopted in both younger and older populations. 相似文献
102.
INTRODUCTION Carotenoids are a class of natural fat-solublepigments generally found in plants, algae, and pho-tosynthetic bacteria, where they play a critical role inthe photosynthetic process. Carotenoids also exist insome non-photo-synthetic bacteria, yeasts, and moldswhere they may carry out a protective functionagainst damages by light and oxygen. Although ani-mals can not synthesize carotenoids within theirbodies, they can intake carotenoids from their dietsleading to bright meat col… 相似文献
103.
<正>最佳功率负荷(Optimum power load,OPL)是指在运动中产生最大输出功率时所对应的外部负荷。该概念源于力-速曲线关系,在递增负重测试中,通过专门的仪器(如线性传感器等)测量杠铃的轨迹速度,再结合负荷推导出OPL。已有多项研究证明OPL与运动表现、专项特征之间的关联性,以及其对竞技水平产生营养的影响,并讨论其在测试和训练方面潜在的应用价值。 相似文献
104.
在学校里,那些讨老师喜欢的学生总是能得到更多的帮助。无论是在学习上还是找工作的过程中。老师愿意花时间亲培养他们喜爱的学生。也乐意为其写一份好的就业推荐书。那么,怎样才能成为讨老师喜欢的学生呢?请看本期直面留学。 相似文献
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Silva DA Benedetti TR Ferrari EP Meurer ST Antes DL Silva AM Santos DA Matias CN Sardinha LB Vieira F Petroski EL 《Journal of sports sciences》2012,30(5):479-484
The objective of this study was to describe the anthropometric profiles of elite older triathletes participating in the 2009 Ironman Brazil and to compare their somatotype, anthropometric and body composition characteristics with those of elite young triathletes and older non-athletes. The sample consisted of 64 males, divided into three groups: (1) older triathletes (n = 17), (2) young triathletes (n = 24), and (3) older non-athletes (n = 23). Somatotype was analysed according to the Carter and Heath ( 1990 ) method. Body mass index, sum of four skinfolds, percentage body fat, body fat mass, and fat-free mass were also estimated. Older non-athletes had higher endomorphy, sum of four skinfolds, fat percentage, and body fat mass than the athletes. Older athletes who participated in the Ironman and elite young triathletes had higher fat-free mass than older non-athletes. Older triathletes and older non-athletes were considered mainly endomorphic mesomorphs and young triathletes mainly ectomorphic mesomorphs. The findings that characterize the anthropometric profile of athletes in this sports modality could be used as a reference. 相似文献
107.
Liu F Zhong H Liang JY Fu P Luo ZJ Zhou L Gou R Huang J 《Journal of Zhejiang University. Science. B》2010,11(12):905-911
In this paper,we investigate the effect and the possible mechanism of high glucose levels on the calcification of human aortic smooth muscle cells (HASMCs).HASMCs were divided into four groups: normal glucose group (NG),osmolality control group (OC),high glucose group (HG,HASMCs culture medium containing 30 mmol/L glucose),and high glucose plus recombinant human Noggin protein (bone morphogenetic protein-2 (BMP-2) antagonist) group (HN).The mRNA levels and the protein expressions of BMP-2 and core binding factor alpha-1 (Cbfα-1) were measured by real-time quantitative polymerase chain reaction (PCR) and Western blot.After induced by 10 mmol/L β-glycerol phosphoric acid,cells were harvested for assessments of alkaline phosphatase (ALP) activities at Days 1,2,and 3,and intracellular calcium contents at Days 7 and 14,respectively.High glucose levels increased the mRNA levels and the protein expressions of BMP-2 and Cbfα-1 (P0.05).The expression of Cbfα-1 was partially blocked by Noggin protein (P0.05),while BMP-2 was not (P0.05).After being induced by β-glycerol phosphoric acid,high glucose levels increased the ALP activity [(48.63±1.03) vs.(41.42±2.28) U/mg protein,Day 3;P0.05] and the intracellular calcium content [(2.76±0.09) vs.(1.75±0.07) μmol/mg protein,Day 14;P0.05] in a time-dependent manner when compared with the NG group,while the ALP activity could not be blocked by Noggin protein [(48.63±1.03) vs.(47.37±0.97) U/mg protein,Day 3;P0.05].These results show that high glucose levels can evoke the calcification of HASMCs by inducing osteoblastic trans-differentiation and intracellular calcium deposition via the BMP-2/Cbfα-1 pathway,which can be partially blocked by Noggin protein. 相似文献
108.
Atkinson L Chisholm VC Scott B Goldberg S Vaughn BE Blackwell J Dickens S Tam F 《Monographs of the Society for Research in Child Development》1999,64(3):45-66; discussion 213-20
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