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.     

Effect of Strenuous Physical Activity upon Reaction Time

Abstract

This study was concerned with the effect of bench-stepping in the Harvard Step Test upon finger and foot reaction time and, secondarily, with ascertaining the relationship, if any, between these reaction times and scores on the Harvard Step Test. The subjects were university freshman males. Reaction times were taken before, immediately after, and four minutes after the stepping exercise for 80 subjects. Thirty-six subjects served as controls, involving the reaction times and pulse counts at the prescribed intervals but without exercise. The findings failed to divulge any discernible effect of stepping exercise upon reaction time, or any apparent relationship between reaction time and the sum of the recovery pulse counts following the exercise. In view of these findings it is suggested that study be directed to two related aspects — the effect of exercise to exhaustion on reaction time, and the effect of strenuous and exhaustive exercise upon speed of movement.     

Comparison between the force application point determined by portable force plate system and the center of pressure determined by pressure insole system during alpine skiing

The purposes of this study were (1) to compare the force application point (FAP) calculated by a portable force plate system and the center of pressure (COP) calculated by a pressure insole system during alpine skiing, and (2) to assess whether any statistical differences between FAP/COP characteristics were influenced by the skiing modes, skiers’ skill levels, or pitch of the slope. Seven expert and eight intermediate skiers performed 20 double turns with two different skiing techniques. Similarities between the time characteristics of both systems and repeated measures ANOVA were used for the statistical analysis. Time characteristics of both systems in the y direction (anterior–posterior) were highly comparable. The mean FAP and COP in the x direction (medial–lateral) were different in all skiing modes for the outer ski and for the inner ski for the expert skiers. The ranges of the FAP in both directions were greater than the COP in almost all conditions.     

Kinematic differences of elite and high-performance tennis players in the cross court and down the line forehand

This study identified and compared the full body kinematics of different skill levels in the forehand groundstroke when balls were hit cross court and down the line. Forty-three three-dimensional retro-reflective marker trajectories of six elite and seven high-performance players were recorded using an eight-camera 400 Hz, Vicon motion analysis system. The six highest horizontal velocity forehands with reliable kinematics of all participants were analysed for each specific situation (a total of 156 analysed shots). Significant differences (p < 0.01) and large effect sizes were observed between elite and high-performance players in linear velocity of the shoulder (2.0 vs. 1.2 m/s), angular velocity of the pelvis (295 vs. 168 °/s), and angular velocity of the upper trunk (453 vs. 292 °/s) at impact. The elite group showed a tendency towards higher racquet velocities at impact (p < 0.05). No significant differences were found in angular displacement of the racquet, hip alignment, or shoulder alignment at the completion of the backswing; nor did angular displacement vary significantly at impact. Irrespective of the group, different shoulder, hip, and racquet angles were found at impact, depending on the situation. The results should assist coaches when striving to improve their players' forehand.     

Lernen in informellen Kontexten

Zusammenfassung In der aktuellen Diskussion um Bildung und Lernen wird jetzt auch in Deutschland dem „Informellen Lernen“ verst?rkte Aufmerksamkeit gewidmet. Die Autoren halten diesen Begriff allerdings für unscharf und sprechen daher von „Lernen in informellen Kontexten“. Der Beitrag bezieht sich auf erste Ergebnisse eines empirischen Forschungsprojekts der Universit?t Dortmund und des Deutschen Jugendinstituts zu informellen Lernprozessen Jugendlicher in Settings des freiwilligen Engagements. Nach einer kurzen Darstellung des Forschungsdesigns werden, basierend auf einer ersten Analyse der in der Explorationsphase des Projektes geführten Interviews, die besonderen Strukturbedingungen der untersuchten Settings (Jugendverb?nde, Initiativen und Organisationen der politischen Interessenvertretung) sowie die Lernchancen in diesen Kontexten beschrieben. Im abschlie?enden Teil des Beitrags werden erste Ergebnisse zu den Wirkungen und Ergebnissen des Lernens durch Verantwortungsübernahme im freiwilligen Engagement vorgestellt. Bereits in der Explorationsphase konnten eine Reihe unterschiedlichster, im Engagement entwickelter Kompetenzen identifiziert werden. Neben der M?glichkeit personale, soziale, fachliche und organisatorische Kompetenzen zu erwerben oder zu erweitern, scheint eine freiwillige Verantwortungsübernahme vielf?ltige Chancen der Pers?nlichkeitsentwicklung, der biografischen Orientierung, der Sinnstiftung sowie der Teilhabe an der Erwachsenenwelt zu er?ffnen.      

Epistemology,situated cognition,and mental models: 'Like a bridge over troubled water'

Over the past two decades important educational implications have beendrawn mainly from two movements of epistemology: Constructivismand situated cognition. Aside from a meta-theoretical use ofconstructivism, the concept 'situated cognition' refers to a conceptionof situational context bound to a historically and socially determinedsituational logic. Focusing on educational processes, situated cognitionis considered to be a central construct for instruction, as is theclosely related concept of the construction of mental models.There are various kinds of the construction and change of mental modelsin a situational context: self-guided inductive construction is oneexample; another is the processing of a conceptual model providedto the learner. An emerging question is how the preconception changesand if the effects of such a model transition are stable. An exploratorystudy will be sketched which investigates the significance of aconceptual model provided at the beginning of the learning process;it has been hypothesized, that such a conceptual model significantlyimpacts the stability (i.e. the successful reconstruction) of mentalmodels built in the course of learning. Also considerableintraindividual differences and changes between two points of assessingthe learners' causal explanations were found. Similarities of theindividuals' reconstructions could be explained with regard tosimilarities of the structures of the learning situations and therelated instructional intervention. In general, the results of thisexploratory study support the assumption that mental models areconstructed in dependence on the demands of learning situations.     

Adolescent smoking from a functional perspective: The Berlin-Bremen Study

Longitudinal data from the «Berlin-Bremen Study on Health Behavior» are used to investigate smoking transitions between different stages of smoking. 1357 seventh and eighth graders were asked about their smoking behavior, their expectations with regard to smoking, smoking in their environment, and their self-image in Fall, 1983. 86% and 81% participated again one and two years later, respectively. Analyses of carbon monoxide and serum thiocyanate levels revealed adequate validity for self-reported smoking behavior. Rates of smoking were dramatically different for different educational strata. Direct and indirect functions of smoking are distinguished. The «indirect» function refers to smoking as a means of obtaining access to peer groups, thus increasing one’s psychological well-being. Direct functions refer to social and affective effects of smoking such as looking older or calming down. In line with expectations, indirect functions were found to be more important for younger adolescents and for smoking onset. In contrast, direct functions were better predictors of the smoking behavior of older adolescents and of the transition to regular smoking.     

Peritonealdialyse (PD)

Ohne Zusammenfassung