The energetics and benefit of an arm swing in submaximal and maximal vertical jump performance

The aims of this study were to investigate the energy build-up and dissipation mechanisms associated with using an arm swing in submaximal and maximal vertical jumping and to establish the energy benefit of this arm swing. Twenty adult males were asked to perform a series of submaximal and maximal vertical jumps while using an arm swing. Force, motion and electromyographic data were recorded during each performance and used to compute a range of kinematic and kinetic variables, including ankle, knee, hip, shoulder and elbow joint powers and work done. It was found that the energy benefit of using an arm swing appears to be closely related to the maximum kinetic energy of the arms during their downswing, and increases as jump height increases. As jump height increases, energy in the arms is built up by a greater range of motion at the shoulder and greater effort of the shoulder and elbow muscles but, as jump height approaches maximum, these sources are supplemented by energy supplied by the trunk due to its earlier extension in the movement. The kinetic energy developed by the arms is used to increase their potential energy at take-off but also to store and return energy from the lower limbs and to "pull" on the rest of the body. These latter two mechanisms become more important as jump height increases with the pull being the more important of the two. We conclude that an arm swing contributes to jump performance in submaximal as well as maximal jumping but the energy generation and dissipation sources change as performance approaches maximum.     

Effects of AM3 (Inmunoferon) on increased serum concentrations of interleukin-6 and tumour necrosis factor receptors I and II in cyclists

The aims of this study were to examine the changes in plasma concentrations of inflammatory cytokines induced by training and competition in professional cyclists. We report the serum concentrations of interleukin-6 (IL-6), tumour necrosis factor alpha (TNF-a), tumour necrosis factor receptors I and II (TNFR-I and -II) in a prospective, randomized, double-blind trial involving the administration of AM3 (Inmunoferon), an oral booster immunomodulator, or placebo to 16 professional cyclists (n = 8 in each group) for 65 consecutive days. Serum was collected just before treatment began (baseline), at the end of pre-competition training, before the mountain stage of the competition (60 days), 4 h after finishing this stage (62 days), and 18 h after the fifth and last day of competition (65 days). To determine the normal levels of cytokines and soluble TNF receptors, individual samples from 14 moderately trained healthy controls were studied. After 60 days of training, the serum concentrations of IL-6 did not differ significantly from those at the beginning of the study for either group of cyclists (placebo and AM3). A significant rise was seen in IL-6 concentrations in both the AM3 and placebo groups at 62 days, 4 h after finishing the mountain stage. The increase was significantly greater in the placebo group than in the AM3 group. At 65 days of treatment, 18 h after the fifth and last day of competition, IL-6 concentrations were similar to those recorded at the end of the training, but were significantly higher in the placebo group than in the AM3 group. At the end of training, serum TNFR-I concentrations in both groups of cyclists were significantly lower than at baseline. The concentrations of serum TNFR-I and -II both 4 h after finishing the mountain stage and 18 h after the fifth and last day of competition were significantly higher than those recorded after training in both groups. Professional cycling competition is associated with increases in serum IL-6 and TNFR-I and -II concentrations. Inmunoferon treatment reduced significantly the concentrations of IL-6 but not those of TNFR-I and -II.     

Success in elite cycling: A prospective and retrospective analysis of race results

The development of peak performances is a main research focus in sports science. It is unclear how many former top junior athletes achieve success in the elite class later. The aim of the present study was to examine the careers of athletes who participated in major junior or adult/elite cycling events using prospective and retrospective analysis of competition results. The official results of major junior (age < or = 18 years) and elite (age > 18 years) cycling races from 1980 to 2004 were analysed. Age-related aspects, career lengths, and success were compared between riders who presented results in both junior and elite races (JUNIOR ELITE) and riders who had no junior race results (ELITE ONLY). Altogether, 27,454 results of 8004 athletes from 108 countries were collected. We found that 29.4% of the elite athletes had participated in junior World Championships, and that 34% of the participants in junior World Championships later participated in major elite competitions. JUNIOR ELITE athletes are significantly more successful in several cycling disciplines and have their first and last elite result at a younger age than ELITE ONLY athletes. No difference was found in career lengths. The data presented here emphasize the importance of long-term training programmes in the development of peak performance in cycling.     

Food attitudes in female athletes: association with menstrual cycle length

The aim of this study was to examine the relationship between indicators of risk of disordered eating, body image and varied menstrual cycle lengths. Altogether, 151 female athletes were invited from 16 sports and 70 female non-athletic controls were recruited from a university lecture class. The participants completed several surveys, including demographics, menstrual cycle history, physical activity, Eating Disorder Inventory (EDI) and the Three Factor Eating Questionnaire (TFEQ). Selected EDI subscales were summed to reflect eating disorder risk and body image. Menstrual cyclicity was based on self-reported cycle length for the last 6 months (normal cycles = 26-32 days, irregular cycles < or =26 or >32 days). Athletes overall had more irregular cycles (29.1%) than the non-athletes (15.7%) (P < 0.05). There were significant differences in scores for eating disorder risk, body dissatisfaction, drive for thinness, cognitive restraint (TFEQ) and disinhibition (TFEQ), only when athletes were divided based on menstrual cyclicity (i.e. irregularly cycling athletes had higher scores than athletes with normal menstrual cycle lengths). No differences in these scores were found between non-athletes with normal or irregular menstrual cycle lengths. In conclusion, irregularly short or long menstrual cycle length is associated with subtle indications of higher risk of disordered eating in female athletes.     

Perception of kinematic characteristics of tennis strokes for anticipating stroke type and direction

The purpose of this study was to determine the sources of visual information used by highly skilled tennis players in anticipating their opponent's shots. In Experiment 1, motion analysis of the strokes showed that the relative motion between the racquet and forearm was different between the ground strokes and lobs, but there were no reliable kinematic differences when shot direction was varied. In Experiment 2, 12 skilled tennis players observed the opponent hitting strokes in a normal video or in a point-light display with different segments occluded. Players' anticipation accuracy was not degraded by the use of the point-light display. Occluding the racquet and forearm significantly reduced the participant's ability to determine the type of stroke produced.     

The angiogenetic effect of intramuscular administration of b-FGF and a-FGF on cardiac muscle: the influence of exercise on muscle angiogenesis

Although angiogenetic therapy using recombinant growth factors holds much hope for the treatment of ischaemic diseases, there are still many unanswered questions, including the method of administration, the correct dose of these factors, and the duration of the therapeutic approach. Exercise has also been suggested to induce neovascularizaiton in muscles. We evaluated the angiogenetic effects of the intramuscular administration of basic-fibroblast growth factor (b-FGF) and acidic-fibroblast growth factor (a-FGF) in rat heart, compared with rats who exercised daily. In conclusion, both the intramuscular administration of b-FGF and exercise increased significantly angiogenesis in the heart in contrast to the intramuscular administration of a-FGF, which was ineffective.     

论教师与学生的关系

教师与学生关系的性质对学生自觉性和自尊心的形成有极重要的意义.教育工作的实际经验指出,假定教师能对个别学生表扬他的任何积极方面,那末,学生就能开始注意并培养自已的这些优点. 在很多情况中,学生对自己力量没有自信心的原因,就是在教师方面对他们的能力估计不足。这个事实指出了教师与学生建立的关系上所产生的感化作用是多麽巨大,它不仅能够破坏个别学生,而且还能破坏全级学生对自己力量的信任.女教师纳·克,为了对自己的工作做得不好作辩护,经常向学生们说,他们没有能力,总是不肯好好学习等话。结果,学生们本来能够学习得很好的,丧失了自信心,这样,他们就学习得更坏,成为学校里成绩最坏的一班。这就是说:女教师纳·克只看见了学生的弱点。但是在某一时期内,这个女教师的位置上派来了另一位新教师,她很有经验而且也富有钻研心.最初几天,她注意了学生思想上已有的习惯,和他们一班所以在“学校中最坏”的原因。她就在班上开始培养学生对自己力量的自信心.她从思想上去影响学生,告诉他们,如果能够坚持和系统地工作,便会学习得很好.女教师与学生们的新的关系和正确地组织教学工作,获得了非常良好的成绩.学生们对待自己也不同了,他们信任了自己的力量,对未来的发展前途表现了无限向往.这一班“眼看着”有了转变。过了几个月,学生们自己     

语文课中自然知识的综合复习

在教学过程中进行经常而有系统的复习是学生进步条件之一。在语文课中的自然知识也应当进行综合复习的。在这种课上,只是复习已教过的最基本的和最重要的材料:明确学生的概念,扩大学生的理解力,补足学生的知能。一至三年级的综合复习课大概每一堂课可以复习一课。进行综合复习课时,必须尽量利用过去所应用过的一切教材(例如:实物教材:“活的和干燥的植物和动物标本”、图片、表格、模型、自然历、地图等等)。     

ЛК—3号飞向月球——一个假想的科学故事

一九……年五月十一日二十点十二分莫斯科时间。舱中映射着喷气式发动机和喷出的红色火焰的反照。仅历数分之一秒我们的“ЛК—3”号便稳静地与地球的新卫星——小月球分离开了。小月球是苏维埃人用自己的智慧和双手创造出来的。它是一切星球间航行艇的起点。