Effect of surrogate design on the measured stiffness of snowboarding wrist protectors

In snowboarding, the wrist is the most common injury site, as snowboarders often put their arms out to cushion a fall. This can result in a compressive load through the carpals coupled with wrist hyperextension, leading to ligament sprains or carpal and forearm bone fractures. Wrist protectors are worn by snowboarders in an effort to reduce injury risk, by decreasing peak impact forces and limiting wrist extension to prevent hyperextension during falls. There is no international standard or universally accepted performance specification that snowboarding wrist protectors should conform to, resulting in an inability to judge which designs offer the best protection. This study investigated how surrogate arm design affected the stiffness of wrist protectors during quasi-static mechanical testing. Three surrogate arms with increasing design complexity were used to test three wrist protectors. The results show that surrogate design does influence the stiffness of snowboarding wrist protectors. Given that the surrogate does influence protector performance, it is recommended that a standard surrogate design is established for research and product testing.     

Effects of intensity on muscle-specific voluntary electromechanical delay and relaxation electromechanical delay

The purposes of this study were to examine: 1) the potential muscle-specific differences in voluntary electromechanical delay (EMD) and relaxation electromechanical delay (R-EMD), and 2) the effects of intensity on EMD and R-EMD during step incremental isometric muscle actions from 10 to 100% maximal voluntary isometric contraction (MVIC). EMD and R-EMD measures were calculated from the simultaneous assessments of electromyography, mechanomyography, and force production from the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) during step isometric muscle actions. There were no differences between the VL, VM, and RF for the voluntary EMD_E-M (onsets of the electromyographic to mechanomyographic signals), EMD_M-F (onsets the mechanomyographic to force production), or EMD_E-F (onsets of the electromyographic signal to force production) as well as R-EMD_E-M (cessation of electromyographic to mechanomyographic signal), R-EMD_M-F (cessation of mechanomyographic signal to force cessation), or R-EMD_E-F (cessation of electromyorgraphic signal to force cessation) at any intensity. There were decreases in all EMD and R-EMD measures with increases in intensity. The relative contributions from EMD_E-M and EMD_M-F to EMD_E-F as well as R-EMD_E-M and R-EMD_M-F to R-EMD_E-F remained similar across all intensities. The superficial muscles of the quadriceps femoris shared similar EMD and R-EMD measurements.     

A Latent Growth Curve Approach to Investigating Developmental Dynamics and Correlates of Change in Children's Perceptions of Physical Competence

Abstract

In both the physical and academic domains interest has recently grown regarding developmental change in children's perceptions of competence. Recent advances in statistical methodology, such as latent growth modeling, enable the researcher to analyze developmental trends from both an inter- and intraindividual perspective, thus serving to increase our understanding of correlates of change in perceived competence. Using latent growth modeling, the purpose of the present study was to investigate developmental change in children's perceived competence at physical skills, examining maturational factors and chronological age as possible correlates of change. Subjects were male adolescents (N = 94). Data were collected during the child's sixth, eighth, and ninth grade school years. Results revealed a good fit for the hypothesized model, which specified mean level changes in the variables over time and an interrelationship among the latent chronometric common factors. Although a significant relationship existed between maturation and perceived competence, no significant relationship was evident between chronological age and perceived competence. Findings are discussed with particular reference to the utility of latent growth curve models for assessing developmental processes at both the inter- and intraindividual level.     

Characteristics of the start in women's World Cup skeleton

This study characterizes key elements of the start in elite female World Cup skeleton athletes. The top 20 female competitors in three World Cup races were videotaped within a calibrated space to allow the following components of the start to be quantified: (1) acceleration (velocity at 15-m mark, time to 15-m mark), (2) capacity (time to load, total number of steps to load), and (3) load (velocity at 45-m mark). A correlation analysis was used to establish the relationship between the variables of interest and overall start time (15- to 65-m mark). Velocity at the 15-m mark accounted for 86% of the variance in overall start time at St. Moritz and 85% at Sigulda. A stepwise regression analysis revealed that approximately 89% of the variation in start time could be explained by velocity at the 15-m mark, time to load, and velocity at the 45-m mark. Of the variables analysed in this study, rapid acceleration to attain a high velocity at the 15-m mark was the most important component of a fast overall start time. The importance of the time to load and velocity at the 45-m mark vary according to the different track characteristics.     

Pedagogical Considerations in the Application of New Technologies to Teacher Education

This paper considers the traditional pedagogies underpinning the use of technology in order to deliver learning in educational settings and the lessons that can be drawn for the case of teacher education. It then considers the pedagogy of teacher education itself in order to propose an integrated pedagogical model for the delivery of teacher education by means of the new technologies. It concludes with the view that technology can and should be applied to teacher education but that this might best be viewed as an evolutionary process rather than a revolutionary one.     

ICT and attainment at primary level

During the last six months the British Educational Communications and Technology Agency (BECTa) has published two reports (downloadable from http://www.becta.org.uk/) on the relationship between information and communication technology (ICT) and attainment levels of primary school children in national tests. Together, they constitute a significant contribution to the debate over the place of ICT in our primary schools but they also raise a number of issues regarding the assumptions upon which they are based and the role of teaching staff in the successful exploitation of ICT in the classroom. This article provides a critical analysis of both reports and proposes ways in which the issues raised can be taken forward.     

The effects of dialect awareness instruction on nonmainstream American English speakers

The achievement gaps between poor and more affluent students are persistent and chronic, as many students living in poverty are also members of more isolated communities where dialects such as African American English and Southern Vernacular English are often spoken. Non-mainstream dialect use is associated with weaker literacy achievement. The principal aims of the two experiments described in this paper were to examine whether second through fourth graders, who use home English in contexts where more formal school English is expected, can be taught to dialect shift between home and school English depending on context; and whether this leads to stronger writing and literacy outcomes. The results of two randomized controlled trials with students within classrooms randomly assigned to DAWS (Dialect Awareness, a program to explicitly teach dialect shifting), editing instruction, or a business as usual group revealed (1) that DAWS was more effective in promoting dialect shifting than instruction that did not explicitly contrast home and school English; and (2) that students in both studies who participated in DAWS were significantly more likely to use school English in contexts where it was expected on proximal and distal outcomes including narrative writing, morphosyntactic awareness, and reading comprehension. Implications for theory and practice are discussed.     

Do actions speak louder than words? An effect of the functional use of language on dominant sex role behavior in boys and girls

Although a number of studies document the fact that adult males interrupt females more often than females interrupt males, less is known about whether this behavior is also true of younger boys and girls. This study examined some aspects of dominant-submissive sex role behavior in preschool children and their teachers during conversation at the snack table. It asked whether there was any difference in the number of times girls and boys interrupted their teacher, and whether there was any difference in the number of times the teacher interrupted boys or girls. In succeeding observations, researchers investigated whether girls or boys were assigned the privilege of passing snack more frequently.In Investigation 1 nine boys and nine girls, 4 years of age, were observed talking with a variety of student teachers in a naturalistic snack setting, and checklists were kept of the number of teacher-child, child-teacher interruptions during conversation. In Investigation 2, tallies were kept of the number of times boys and girls assumed the dominant roles of distributing snacks and snack materials.Results indicted that during conversation, boys interrupted their teachers more frequently than the girls did (p > .03). Teachers interrupted girls more frequently than they interrupted boys (p > .02). No significant differences were found in the frequency of participation by boys or girls in passing snack. Results are discussed in relation to the teacher's role in teaching dominant-submissive sex role behaviors to children.