Creatine kinase,myosin heavy chains and magnetic resonance imaging after eccentric exercise

The aim of this study was to examine the relationship between myosin heavy chain (MHC) release as a specific marker of slow-twitch muscle fibre breakdown and magnetic resonance imaging (MRI) of skeletal muscle injury after eccentric exercise. The effects of a single series of 70 high-intensity eccentric contractions of the quadriceps femoris muscle group (single leg) on plasma concentrations of creatine kinase and MHC fragments were assessed in 10 young male sport education trainees before and 1 and 4 days after exercise. To visualize muscle injury, MRI of the loaded thigh was performed before and 4 days after the eccentric exercise. All participants recorded an increase ( P ? 0.05) in creatine kinase after exercise. In five participants, T2 signal intensity was unchanged post-exercise compared with pre-exercise and MHC plasma concentration was normal; however, they showed an increase ( P ? 0.05) in creatine kinase after exercise. For the remaining five participants, there was an increase in T2 signal intensity of the loaded vastus intermedius and vastus lateralis. These changes in MRI were accompanied by an increase in MHC plasma concentration ( P ? 0.01) as well as an increase in creatine kinase ( P ? 0.01). We suggest that changes in MRI T2 signal intensity after muscle damage induced by eccentric exercise are closely related to damage to structurally bound contractile filaments of some muscle fibres. Additionally, MHC plasma release indicates that this damage affects not only fast-twitch fibres but also some slow-twitch fibres.     

Teaching units as the integrating core of mathematics education

How to integrate mathematics, psychology, pedagogy and practical teaching within the didactics of mathematics in order to get unified specific theories and conceptions of mathematics teaching? This problem—relevant for theoretical and empirical studies in mathematics education as well as for teacher training—is considered in the present paper. The author suggests an approach which is based on teaching units (Unterrichtsbeispiele). Suitable teaching units incorporate mathematical, pedagogical, psychological and practical aspects in a natural way and therefore they are a unique tool for integration.     

Analyzing Whispers: college students’ representation and reproduction of sociocultural discourses about bodies,relationships, and (hetero)sexuality using a mobile application

Previous research about college students’ social media usage emphasizes social media practices, often ignoring the content that students’ post. Increasing knowledge about the language that college students use to describe their intimate relationships can inform student affairs practice. Using a digital ethnographic data collection approach and queer theoretical framework, this paper explores the dominant discourses about race, sexuality, and relationships circulated in a mobile social networking application. This paper used content analysis to describe the meaning of text and images produced by college-aged youth in the US. Through this analysis of social media content, I contend that college students engage in the complex representations and reproductions of sociocultural norms about bodies, sexuality, and relationships and that these representations and reproductions influence campus climate. I develop implications for student affairs administrators.     

The Relationships Between Paranormal Belief, Creationism, Intelligent Design and Evolution at Secondary Schools in Vienna (Austria)

The present study is the first to investigate the relationships between a multiple set of paranormal beliefs and the acceptance of evolution, creationism, and intelligent design, respectively, in Europe. Using a questionnaire, 2,129 students at secondary schools in Vienna (Austria) answered the 26 statements of the Revised Paranormal Belief Scale (R-PBS) and three statements about naturalistic evolution, creationism and intelligent design (ID). The investigated Austrian students showed an average R-PBS score of 82.08, more than 50% of them agreed with naturalistic evolution, 28% with creationism, and more than a third agreed with ID, the latter two closely correlated with each other. Females generally showed higher belief scores in the paranormal, creationism and ID. The agreement with naturalistic evolution correlated negatively with religious belief, but not with other paranormal beliefs, whereas the two non-scientific alternatives to evolution significantly correlated with both traditional and paranormal beliefs. Religious belief showed a significant positive correlation with other paranormal beliefs. All subscales of paranormal belief decreased during the eight grades of secondary school, as did acceptance of creationism and ID. However, the acceptance of naturalistic evolution did not correlate with age or grade. Possible reasons and implications for science education and the biology curriculum at Austrian secondary schools are discussed.     

从守护者到领路人:全球图书馆界的新角色

随着信息在人们生活和社会发展中的作用发生变化,图书馆和图书馆员的角色也经历从守护者向门户再向领路人的转变。历史上,图书馆和图书馆员作为守护者为保护和传承人类文化做出了贡献,但在社会服务方面主要是为少数精英阶层提供服务;信息、知识、学习被认为是精英阶层的特权,社会大众被认为没有必要获取信息。第二次工业革命时期,人们普遍认识到基本文化素养的必要性,西方社会也逐渐形成共识,即确保每个社会成员至少接受过初等教育;此后,随着技术进步,印刷成本降低,信息能被更多人获取和利用;公共图书馆开始普及并向社会公众开放,图书馆和图书馆员发挥门户的作用,帮助人们克服获取信息的障碍;进入数字时代,图书馆仍然发挥门户的作用,确保任何人无论其身份、财富、背景如何,都不应被排除在信息获取之外。人类社会进入信息时代,信息极大丰富与信息稀缺一样,给信息获取带来了种种问题,人们需要使用批判性思维来面对海量的信息资源;图书馆需充分发挥领路人的作用,帮助社会公众提升信息素养,实现对丰富信息的有效利用,助力创建更强大、更公平、更具创新性的社会。     

Biomechanical comparison of the double-push technique and the conventional skate skiing technique in cross-country sprint skiing

Abstract

The aims of the study were to: (1) adapt the “double-push” technique from inline skating to cross-country skiing; (2) compare this new skiing technique with the conventional skate skiing cross-country technique; and (3) test the hypothesis that the double-push technique improves skiing speed in a short sprint. 13 elite skiers performed maximum-speed sprints over 100 m using the double-push skate skiing technique and using the conventional “V2” skate skiing technique. Pole and plantar forces, knee angle, cycle characteristics, and electromyography of nine lower body muscles were analysed. We found that the double-push technique could be successfully transferred to cross-country skiing, and that this new technique is faster than the conventional skate skiing technique. The double-push technique was 2.9 ± 2.2% faster (P < 0.001), which corresponds to a time advantage of 0.41 ± 0.31 s over 100 m. The double-push technique had a longer cycle length and a lower cycle rate, and it was characterized by higher muscle activity, higher knee extension amplitudes and velocities, and higher peak foot forces, especially in the first phase of the push-off. Also, the foot was more loaded laterally in the double-push technique than in the conventional skate skiing technique.     

Determination of the centre of mass kinematics in alpine skiing using differential global navigation satellite systems

In the sport of alpine skiing, knowledge about the centre of mass (CoM) kinematics (i.e. position, velocity and acceleration) is essential to better understand both performance and injury. This study proposes a global navigation satellite system (GNSS)-based method to measure CoM kinematics without restriction of capture volume and with reasonable set-up and processing requirements. It combines the GNSS antenna position, terrain data and the accelerations acting on the skier in order to approximate the CoM location, velocity and acceleration. The validity of the method was assessed against a reference system (video-based 3D kinematics) over 12 turn cycles on a giant slalom skiing course. The mean (± s) position, velocity and acceleration differences between the CoM obtained from the GNSS and the reference system were 9 ± 12 cm, 0.08 ± 0.19 m · s^-1 and 0.22 ± 1.28 m · s^-2, respectively. The velocity and acceleration differences obtained were smaller than typical differences between the measures of several skiers on the same course observed in the literature, while the position differences were slightly larger than its discriminative meaningful change. The proposed method can therefore be interpreted to be technically valid and adequate for a variety of biomechanical research questions in the field of alpine skiing with certain limitations regarding position.     

Themenheft: Digitale Bibliotheken

Ohne Zusammenfassung     

Biomechanical validation of a specific upper body training and testing drill in cross-country skiing

The aim of this study was to perform a biomechanical validation of a double poling imitation drill on a rollerboard. Six elite cross-country skiers performed three imitation drill trials at maximal speed at 13 degrees inclination and in double poling on roller skis on a paved road of 3 degrees. Pole and strap forces, elbow and hip angles and EMG activity of eight upper body muscles were measured. Force curves showed similar characteristics, except for impact force occurring only at pole plant in double poling on roller skis. Double poling on a rollerboard includes an eccentric roll-down phase not appearing in double polling on roller skis. Forces on the rollerboard were similar to those on roller skis. Courses of the elbow angles indicated similar shapes, except for the angle at the start of the propulsion phase and, consequently, during flexion (p < 0.01). Propulsion time and cycle duration were longer and frequency lower on the rollerboard (all p < 0.001). Muscle activities were not significantly different, except for stronger biceps brachii (p < 0.01) and weaker erector spinae activation (p < 0.05) on the rollerboard. Muscle coordination patterns showed similar onset and offset points of each muscle and comparable activations in both activities, except for biceps brachii. Two movement strategies on the rollerboard were found, which led to small differences in measured variables. The biomechanical validity of double poling on a rollerboard can be judged as moderately high, being aware of the differences in some variables that might be considered in training sessions on the rollerboard, particularly when using intervals with high number of repetitions.     

The effects of differential and variable training on the quality parameters of a handball throw

The aim of this study was to undertake a comprehensive temporal, effective, and practical training study (variable and differential learning) that would offer athletes the opportunity to increase their performance, and to analyse the effects by measuring kinematics and quality parameters. Two participants of differing standards--a player of the first Austrian League and an Olympic and World Champion--but of similar anthropometric characteristics were recruited. One of the participants (Austrian League) was tested on five different occasions (pre-test and four retests) to measure the effects of four different training phases using kinematic analysis. The results of the study indicate an increase in ball velocity within the differential training phases (first, second, and fourth phases), different proximal-to-distal sequences of the participants, and a change of movement pattern during training measured by the segment velocities and the angle-time courses.