Effects of muscle-tendon length on joint moment and power during sprint starts

The aim of this study was to examine the effects of muscle-tendon length on joint moment and power during maximal sprint starts. Nine male sprinters performed maximal sprint starts from the blocks that were adjusted either to 40 degrees or 65 degrees to the horizontal. Ground reaction forces were recorded at 833 Hz using a force platform and kinematic data were recorded at 200 Hz with a film camera. Joint moments and powers were analysed using kinematic and kinetic data. Muscle - tendon lengths of the medial gastrocnemius, soleus, vastus medialis, rectus femoris and biceps femoris were calculated from the set position to the end of the first single leg contact. The results indicated that block velocity (the horizontal velocity of centre of mass at the end of the block phase) was greater (P < 0.01) in the 40 degrees than in the 65 degrees block angle condition (3.39 +/- 0.23 vs. 3.30 +/- 0.21 m . s(-1)). Similarly, the initial lengths of the gastrocnemius and soleus of the front leg in the block at the beginning of force production until half way through the block phase were longer (P < 0.001) in the 40 degrees than in the 65 degrees block angle condition. The initial length and the length in the middle of the block phase were also longer in the 40 degrees than in the 65 degrees block angle condition both for both the gastrocnemius (P < 0.01) and soleus (P < 0.01-0.05) of the rear leg. In contrast, the initial lengths of the rectus femoris and vastus medialis of the front leg were longer (P < 0.05) in the 65 degrees than in the 40 degrees block angle condition. All differences gradually disappeared during the later block phase. The peak ankle joint moment (P < 0.01) and power (P < 0.05) during the block phase were greater in the 40 degrees than in the 65 degrees block angle condition for the rear leg. The peak ankle joint moment during the block phase was greater (P < 0.05) in the 40 degrees block angle for the front leg, whereas the peak knee joint moment of the rear leg was greater (P < 0.01) in the 65 degrees block angle condition. The results suggest that the longer initial muscle-tendon lengths of the gastrocnemius and soleus in the block phase at the beginning of force production contribute to the greater peak ankle joint moment and power and consequently the greater block velocity during the sprint start.     

Job change in later life: A process of marginalization?

Adopting a longitudinal approach, this article examines downward occupational mobility (DOM) later in working life and its effects on job satisfaction and perceptions of working conditions of older workers in Europe. The main aim was to test whether the risk that workers will be negatively impacted and marginalized in the labor market due to demotion into lower quality jobs is offset by benefits. Based on an ordinal logistic regression of merged Survey of Health, Ageing and Retirement in Europe and English Longitudinal Study of Ageing datasets, the study found a positive significant impact of DOM on overall job satisfaction. Moreover, DOM was associated with a statistically significant reduction in workload pressure, although it did increase physical work demand. This article adds to the literature on marginalization of workers with indications that the lower income and status associated with DOM at older ages may have offsetting benefits.     

Using LOGO with Infant School Children

Abstract The recent introduction of micro‐computers into schools is opening up many new avenues for developmental psychologists interested in studying how children learn. Of particular interest at present are approaches in which children program computers themselves, using languages such as LOGO and PROLOG. This paper describes a study in which a simplified version of LOGO was introduced to a group of six‐year‐olds in a severely deprived area of Edinburgh. The children used a special touch‐sensitive keyboard (Concept Keyboard) to control the movements of a floor‐crawling robot called a Turtle. The sessions with the Turtle were marked by high levels of concentration, collaborative problem‐solving and the use of mathematical language. Pre‐ and post‐tests on the British Ability Scales revealed statistically significant gains on the sub‐scales concerned with number and shape: these gains, however, were found only in the boys.     

An interactive learning and course development environment: Context,theoretical and empirical considerations

In this contribution, a theoretical and empirical framework based on work carried out at the Open universiteit (Ou) for a new approach towards the design, production and delivery of flexible, interactive learning materials for distance education is presented.

In the Research and Development centre of the Ou, a project has concentrated on the innovation of current approaches. This framework can also be considered as an advance organizer to reading the remaining articles from the Open universiteit in this issue of Distance Education.

A key feature of the innovation is that during the design phase, course developers have to define ‘models’ of the materials to be developed: a content model, a support model, a student model and the learning path. From a flexibility point of view especially, the ‘student model’ is of importance since it defines the student variables that will be taken into account when developing/ presenting alternative materials (basic content and/or embedded support). A computer‐based system, the ‘Interactive Learning and Course Development Environment (ILCE)’, was developed to support the work of course development teams and tutors on the one hand, and students on the other hand. The development system supports the work of the developers; the delivery system supports the study process of students. The delivery is realised as an on‐line course, on the World Wide Web.

Students start working with the ILCE‐system by following an intake procedure. They can make choices in relation to student variables that have been defined in the student model (profession, study intentions, context, etc.). Next, they can ‘on the fly’ generate a course. Rom the large repository of learning materials only those materials are selected and compiled that are in line with the student model of this specific student Furthermore, they can choose to study the materials on screen and/or make prints of the materials. Of course, in printing the materials they lose the interactive and dynamic possibilities of the computer learning environment     

An exploration of Outward Bound New Zealand’s organisational culture

This article examines the key factors of organisational culture (artefacts, values and beliefs, and core assumptions) that have led to the development of Outward Bound New Zealand (OBNZ) over the past 50 years. Primary data for this case study were obtained through the use of semi-structured, in-depth interviews with past and present school and executive directors. A key finding is that OBNZ, founded on the beliefs of the German educator Kurt Hahn, has reviewed its values and formalised these into the ‘fundamentals’ of greatness, compassion, responsibility and integrity. Important visible symbols of the OBNZ brand are the badge, the logo with ‘to serve, to strive and not to yield’ and the cutter. The core assumption is still focused on self-discovery and the Outward Bound motto ‘there’s more to you than you think’. Internationally, Outward Bound course length has declined to just 4 days compared with OBNZ’s average of 14 days. In contrast, OBNZ has remained true to Hahn’s original belief, the ‘fundamental’ values, core assumptions and the Standard/Classic (three-week) course. These findings have implications for the development of outdoor adventure education and business organisations’ culture and leadership.     

Bullying and social support: variation by school-type and emotional or behavioural disturbances

The present study analysed whether bullying/victimisation and related social support vary by emotional and behavioural disturbances (EBD) as well as school type. We examined 540 German adolescents with and without emotional disturbances (ED)/behavioural disturbances (BD) attending regular and special schools for students with EBD. Adolescents with BD and co-morbid co-occurring emotional and behavioural disturbances (ED + BD) reported elevated levels of bullying, while students with ED and co-morbid ED + BD reported elevated levels of victimisation. Enhanced levels of overt victimisation were also found in adolescents from special schools. Students from special schools perceived less peer support but more teacher support. Furthermore, adolescents with co-morbid ED + BD were least likely to tell teachers about being victimised. It is concluded that bullying interventions for adolescents with EBD and students from special schools need to be implemented and evaluated.     

Übereinstimmung,Variabilität und Reliabilität von Schülerurteilen zur Unterrichtsqualität auf Schulebene

Using student ratings to assess instructional quality of schools should fulfill three requirements: (1) an appropriate level of inter-rater agreement within schools, (2) systematic variance of student ratings between schools, (3) an adequate reliability level of aggregated student ratings. Using international PISA-data (2000–2012; 81 countries, over 55,300 schools, over 1.3 million 15-year olds) this study investigated how these requirements were met regarding indicators of instructional quality (classroom management, cognitive activation, individual learning support). We computed the interrater agreement index r_WG(J), as well as the intraclass correlations ICC(1) and ICC(2). Our results showed that (1) student ratings demonstrated a moderate or strong level of agreement for most indicators of instructional quality and (2) instructional quality assessed by students varied systematically between schools. Yet, (3) reliability of aggregated student ratings was not sufficient in many countries. We discuss these results regarding conventions to evaluate agreement, variability, and reliability of student ratings at the school level.