Angle-specific impairment of elbow flexors strength after isometric exercise at long muscle length

In this study, we examined the long-term reductions in maximal isometric force (MIF) caused by a protocol of repeated maximal isometric contractions at long muscle length. Furthermore, we wished to ascertain whether the reductions in MIF are dependent on muscle length--that is, are the reductions in MIF more pronounced when the muscle contracts at a short length. The MIF of the elbow flexors of seven young male volunteers was measured at five different elbow angles between 50 degrees and 160 degrees. On a separate day, the participants performed 50 maximal voluntary isometric muscle contractions with the elbow flexors at a lengthened position; that is, with the shoulder hyperextended at 45 degrees and the elbow joint fixed at 140 degrees. Following this exercise, the MIF at the five elbow angles, range of motion, muscle soreness and plasma creatine kinase activity were measured at 24 h intervals for 4 days. On day 1, the decline in MIF was higher at the more acute elbow angles of 50 degrees (42 +/- 8%) and 70 degrees (39 +/- 8%; both P<0.01) than at 90 degrees (26 +/- 4%) and 140 degrees (16 +/- 3%; both P<0.01). No significant reduction in MIF was evident at an elbow angle of 160 degrees. Maximal isometric force at an elbow angle of 140 degrees was fully restored on day 3, whereas at an angle of 50 degrees it remained depressed for the 4 day observation period. Restoration of MIF was a function of the elbow angle, with force recovery being less at the smaller angles. The range of motion was decreased by 14 +/- 2 degrees on day 1 (P<0.01) and did not return to baseline values by day 4. Muscle soreness ratings remained significantly elevated for the 4 day period. Serum creatine kinase peaked on day 1 (522 +/- 129 IU, P<0.01) and decreased thereafter. We conclude that the disproportionate decrease in MIF at the small elbow angles and the length-specific recovery in MIF after repeated maximal isometric contractions at long muscle length may be explained by the presence of overstretched sarcomeres that increased in series compliance of the muscle, therefore causing a rightward shift of the force-length relationship.     

Science and the major racket sports: a review

The major racket sports include badminton, squash, table tennis and tennis. The growth of sports science and the commercialization of racket sports in recent years have focused attention on improved performance and this has led to a more detailed study and understanding of all aspects of racket sports. The aim here, therefore, is to review recent developments of the application of science to racket sports. The scientific disciplines of sports physiology and nutrition, notational analysis, sports biomechanics, sports medicine, sports engineering, sports psychology and motor skills are briefly considered in turn. It is evident from these reviews that a great deal of scientific endeavour has been applied to racket sports, but this is variable across both the racket sports and the scientific disciplines. A scientific approach has helped to: implement training programmes to improve players' fitness; guide players in nutritional and psychological preparation for play; inform players of the strategy and tactics used by themselves and their opponents; provide insight into the technical performance of skills; understand the effect of equipment on play; and accelerate the recovery from racket-arm injuries. Racket sports have also posed a unique challenge to scientists and have provided vehicles for developing scientific methodology. Racket sports provide a good model for investigating the interplay between aerobic and anaerobic metabolism and the effect of nutrition, heat and fatigue on performance. They have driven the development of mathematical solutions for multi-segment interactions within the racket arm during the performance of shots, which have contributed to our understanding of the mechanisms of both performance and injury. They have provided a unique challenge to sports engineers in relation to equipment performance and interaction with the player. Racket sports have encouraged developments in notational analysis both in terms of analytical procedures and the conceptualization of strategy and tactics. Racket sports have provided a vehicle for investigating fast interceptive actions, hand-eye coordination and perception-action coupling in the field of motor control. In conclusion, science has contributed considerably to our knowledge and understanding of racket sports, and racket sports have contributed to science by providing unique challenges to researchers.     

Acute impact of submaximal resistance exercise on immunological and hormonal parameters in young men

In this study, we examined the acute effects of submaximal resistance exercise on immunological and hormonal parameters in 7 resistance-trained and 10 non-resistance-trained males. The participants, who were aged 29.5 +/- 7.1 years (mean +/- s), performed submaximal resistance exercise at 75% of their one-repetition maximum. Blood samples were taken before, during, immediately after, and 30, 60 and 120 min after exercise and analysed for leukocyte subpopulations and stress hormones. Total leukocytes, neutrophils and monocytes increased during exercise, reaching their maximum 2 h after exercise. Lymphocytes increased during exercise, T-helper cells returned to resting values after exercise, and natural killer cells and T-suppressor cells decreased below resting values. The CD4/CD8 ratio decreased during exercise but increased during recovery. The resistance-trained participants tended to have lower T-helper cell counts before, during and immediately after exercise and a lower CD4/CD8 ratio during recovery than the non-resistance-trained participants. Plasma cortisol correlated positively with leukocytes during exercise (r = 0.572, P < 0.05), but negatively with T-helper cells 30 and 60 min after exercise (r = -0.573, P < 0.05; r = -0.642, P < 0.01, respectively). Our results indicate that resistance exercise leads to acute changes in leukocyte counts, despite moderate hormonal changes, independent of training status. Regular resistance exercise might lead to decreased T-helper cell counts and a lower CD4/CD8 ratio, which could increase susceptibility to infections.     

Effectiveness of training health professionals in literature search skills using electronic health databases--a critical appraisal

The objective was to assess the effect on health professionals' skills of one to eight hours literature search and retrieval training from electronic health databases. We searched: Cochrane library (2002; Issue 3), MEDLINE (1977-2002/5), EMBASE (1980-2002/7); CINAHL (1982-2002/5); ASSIA (1982-2002/7), BNI (1994-2002/5), ERIC (1985-2002/6); LISA (1969--current), NRR (2002, Issue 2), the world-wide-web and references. The selection criteria consisted of randomised controlled trials, controlled before and after, and controlled cohort studies in comparison with no training. The intervention had to be one to eight hours training in literature search and retrieval skills for health professionals. The outcome was the effect on health professionals' literature search and retrieval skill levels measured through reliable instruments. For data collection and ana-lysis, one reviewer extracted data and assessed the quality of the studies and the second reviewer checked it. The results indicate that there is some evidence of positive impact on health professionals' skill levels in literature searching and they find the training useful. In conclusion, the size of the positive effect is debatable as only three small and methodologically weak studies met the inclusion criteria and out of those only two showed the positive effect.     

魔法解读

一次朋友聚会时,我手边恰好有一本关于感情和命运的格言书。一个有趣的朋友提议玩一个游戏:他像个预言家一样,拿起一本书,让我们随口说出一个页码,再选出第几行,要选定的,就是对于你人生的预言和警示。被他的神秘和笃定所蛊惑,我们都选了,心里惴惴不安。     

机构知识库在美国的发展

1背景 2005年初，网络信息联盟（http：／／www．cni．org）对它在美国的学术成员机构进行了有关机构知识库发展现状的问卷调查。在同一时间，联盟为参加名为“为机构知识库构造一个战略性案例”的国际性会议而进行准备，开展了美国国家报告的信息编撰工作，因此，调查工作和信息编撰工作是一起进行的。“为机构知识库构造一个战略性案例”国际会议于2005年5月10-11日在阿姆斯特朗举办，网络信息联盟、英国联合信息系统委员会和荷兰SURF基金会联合主办此次国际会议。共有13个国家参会，他们分别提供了本国机构知识库的部署情况。     

为生存而斗争的中国人

中国的烹饪技术虽然是世界上的奇迹之一，然而对于平民百姓来说，是肚子而不是口味决定他们吃些什么。蚕在吐完蚕丝后它们的蛹就被作为食物；马、骡、驴、骆驼一旦不干活了，就成为屠夫的刀下之鬼；自然死亡的牛、猪是不会被扔掉的。……在广东，老鼠和猫都在市场上出售；船夫将外国人的厨师抛弃的家禽的头、爪和内脏收拾干净后吃掉。     

不一样的童年

有天在公交车上，人很多，我只有牢牢抓住一个座椅的靠背。后面坐着一对父子，一个七八岁的小胖子坐在爸爸腿上，兴奋地四下看。慢慢地我发现，总有一只手，有意无意触摸我的手，无论我上挪还是下移。