The relationship between peak height velocity and physical performance in youth soccer players

Longitudinal changes in height, weight and physical performance were studied in 33 Flemish male youth soccer players from the Ghent Youth Soccer Project. The players' ages at the start of the study ranged from 10.4 to 13.7 years, with a mean age of 12.2 +/- 0.7 years. Longitudinal changes were studied over a 5 year period. Peak height velocity and peak weight velocity were determined using non-smoothed polynomials. The estimations of peak height velocity, peak weight velocity and age at peak height velocity were 9.7 +/- 1.5 cm x year-1, 8.4 +/- 3.0 kg x year-1 and 13.8 +/- 0.8 years, respectively. Peak weight velocity occurred, on average, at the same age as peak height velocity. Balance, speed of limb movement, trunk strength, upper-body muscular endurance, explosive strength, running speed and agility, cardiorespiratory endurance and anaerobic capacity showed peak development at peak height velocity. A plateau in the velocity curves was observed after peak height velocity for upper-body muscular endurance, explosive strength and running speed. Flexibility exhibited peak development during the tear after peak height velocity. Trainers and coaches should be aware of the individual characteristics of the adolescent growth spurt and the training load should also be individualized at this time.     

Imagery use by injured athletes: a qualitative analysis

The purpose of this study was to expand our knowledge and increase our understanding of imagery use by athletes in sport-injury rehabilitation using a qualitative approach. The participants were 10 injured athletes who were receiving physiotherapy at the time they were interviewed. During the interviews, the athletes provided extensive information about their use of imagery during injury rehabilitation and it was clear that they believed imagery served cognitive, motivational and healing purposes in effectively rehabilitating an injury. Cognitive imagery was used to learn and properly perform the rehabilitation exercises. They employed motivational imagery for goal setting (e.g. imagined being fully recovered) and to enhance mental toughness, help maintain concentration and foster a positive attitude. Imagery was used to manage pain. The methods they employed for controlling pain included using imagery to practise dealing with expected pain, using imagery as a distraction, imagining the pain dispersing, and using imagery to block the pain. With respect to what they imaged (i.e. the content of their imagery), they employed both visual and kinaesthetic imagery and their images tended to be positive and accurate. It was concluded that the implementation of imagery alongside physical rehabilitation should enhance the rehabilitation experience and, therefore, facilitate the recovery rates of injured athletes. Moreover, it was recommended that those responsible for the treatment of injured athletes (e.g. medical doctors, physiotherapists) should understand the benefits of imagery in athletic injury rehabilitation, since it is these practitioners who are in the best position to encourage injured athletes to use imagery.     

The role of effort in moderating the anxiety-performance relationship: Testing the prediction of processing efficiency theory in simulated rally driving

We tested some of the key predictions of processing efficiency theory using a simulated rally driving task. Two groups of participants were classified as either dispositionally high or low anxious based on trait anxiety scores and trained on a simulated driving task. Participants then raced individually on two similar courses under counterbalanced experimental conditions designed to manipulate the level of anxiety experienced. The effort exerted on the driving tasks was assessed though self-report (RSME), psychophysiological measures (pupil dilation) and visual gaze data. Efficiency was measured in terms of efficiency of visual processing (search rate) and driving control (variability of wheel and accelerator pedal) indices. Driving performance was measured as the time taken to complete the course. As predicted, increased anxiety had a negative effect on processing efficiency as indexed by the self-report, pupillary response and variability of gaze data. Predicted differences due to dispositional levels of anxiety were also found in the driving control and effort data. Although both groups of drivers performed worse under the threatening condition, the performance of the high trait anxious individuals was affected to a greater extent by the anxiety manipulation than the performance of the low trait anxious drivers. The findings suggest that processing efficiency theory holds promise as a theoretical framework for examining the relationship between anxiety and performance in sport.     

Immediate effects of the use of modified take-off boards on the take-off motion of the long jump during training

We investigated the immediate effects of the combined use of inclined and raised flat boards on the take-off motion of the long jump. Eight male long jumpers were videotaped with two high-speed video cameras (250 Hz) set perpendicular to the runway. The athletes jumped with three modified take-off boards: upward-inclined boards of two different inclinations (2.5 and 5.0 degrees), and a raised flat board (50 mm high). The jumpers performed pre- and post-jumps using their own techniques before and after use of the boards to test their effects. The post- jump revealed significantly less reduction in the horizontal velocity during the take-off than the pre-jump, and the effectiveness of converting the velocity from horizontal to vertical increased significantly in the post-jump. The post-jump demonstrated significantly less knee flexion of the take-off leg during take-off. The reduced knee flexion and slower extension velocity of the take-off leg in the second phase of the post-jump contributed to increasing the knee extension torque in the second phase and resulted in the increases in vertical ground reaction force and vertical velocity. These results suggest that the combined use of the inclined and raised flat boards induced immediate effective changes in the kinematics and kinetics of the take-off motion and represent appropriate training tools for take-off techniques of the long jump.     

Physical and metabolic demands of training and match-play in the elite football player

In soccer, the players perform intermittent work. Despite the players performing low-intensity activities for more than 70% of the game, heart rate and body temperature measurements suggest that the average oxygen uptake for elite soccer players is around 70% of maximum (VO(2max). This may be partly explained by the 150 - 250 brief intense actions a top-class player performs during a game, which also indicates that the rates of creatine phosphate (CP) utilization and glycolysis are frequently high during a game. Muscle glycogen is probably the most important substrate for energy production, and fatigue towards the end of a game may be related to depletion of glycogen in some muscle fibres. Blood free-fatty acids (FFAs) increase progressively during a game, partly compensating for the progressive lowering of muscle glycogen. Fatigue also occurs temporarily during matches, but it is still unclear what causes the reduced ability to perform maximally. There are major individual differences in the physical demands of players during a game related to physical capacity and tactical role in the team. These differences should be taken into account when planning the training and nutritional strategies of top-class players, who require a significant energy intake during a week.     

我院大学英语教学改革的思考与建议

21世纪将是一个国际化的科技经济时代、信息时代,智力和人才竞争时代。对中国来说,是一个逐步与国际社会接轨,进一步改革开放的时代。面对这样一个时代,大学英语教学改革势在必行。文章介绍了21世纪对人才的要求,分析了体院大学英语教学存在的问题,提出了关于大学英语教学改革的几点意见。     

肅清糊塗思想

武訓這个名字,對內蒙古教育工作者來說,還是生疏的,電影“武训傳”也没有在內蒙放映,但是在內蒙展開電影“武訓傳”的討論,教育意義仍是非常之大的。武訓生在封建時代,受侮辱,受窮困,這並不可恥,最可恥的是他不但甘於忍受侮辱,毫不反抗,反而竭尽平生精力積極的來維護這个社會制度。在當時確實起了麻痺農民的反抗,維護了封建统制秩序的反动作用。     

讀了職業教育專號以後

我是喜欢研究职业教育的人,却並不是職業教育的专家,我向來對於职业教育也很懷疑,對於職業学校尤其怀疑。不過我所懷疑的,是職業教育和職業學校在中國何以不能显出效能,不是懷疑職業教育和职業學校的本身,職業教育在教育史上的年代,原來很短,就是最發達的德国,美國,提倡的時期,距今也還不遠,他們也有許多問題,不能得到圓满的解決,正怪不得我們中國還在‘議論紛紜,莫衷一是’     

论缓冲溶液的制备

凡实验室涉及到生物学和化学的水溶液体系时,pH和离子强度(I)是两个极为重要的可变量。由于酸—碱混合物的存在,这两个参量往往相互依赖。控制pH值的通常方法是使用缓冲剂。它们是由那些对于溶液离子行为影响不大、且不活泼的稳定电解质来配制的。本文提出的方法适用于计算某种酸及其盐混合物的pH值和离子强度;或与此相反,用于计算配制预知pH值和离子强度(I)所需酸及其盐的相当量。这种计算方法很实用,具有启发性和直观教学的价值,在许多普通的可编程序计算器上容易完成。