Relative shank to thigh length is associated with different mechanisms of power production during elite male ergometer rowing

The effect of anthropometric differences in shank to thigh length ratio upon timing and magnitude of joint power production during the drive phase of the rowing stroke was investigated in 14 elite male rowers. Rowers were tested on the RowPerfect ergometer which was instrumented at the handle and foot stretcher to measure force generation, and a nine segment inverse dynamics model used to calculate the rower's joint and overall power production. Rowers were divided into two groups according to relative shank thigh ratio. Time to half lumbar power generation was significantly earlier in shorter shank rowers (p = 0.028) compared to longer shank rowers, who showed no lumbar power generation during the same period of the drive phase. Rowers with a relatively shorter shank demonstrated earlier lumbar power generation during the drive phase resulting from restricted rotation of the pelvic segment requiring increased lumbar extension in these rowers. Earlier lumbar power generation and extension did not appear to directly affect performance measures of the short shank group, and so can be attributed to a technical adaptation developed to maximise rowing performance.     

Tackle and ruck technique proficiency within academy and senior club rugby union

ABSTRACT

This study examined the validity of a tool that assesses tackle and ruck technique in training and established reference data for tackle, ball-carry and ruck technique at different levels of play in rugby union. One hundred and thirty-one amateur rugby union players; 37 senior, 51 first-grade academy and 43 second-grade academy players, participated in a two-on-two contact drill. The drill was filmed and the players’ tackle, ball-carry and ruck technique were assessed using standardized technical criteria. Senior level players scored significantly higher in all three assessments; tackle technique senior vs academy 1^st (p < 0.01, effect size (ES) = 0.7, moderate), senior vs academy 2^nd (p < 0.01, ES = 0.7, moderate); ball-carry technique senior vs academy 1^st (p < 0.01, ES = 0.6, moderate), senior vs academy 2^nd (p < 0.01, ES = 0.8, moderate); ruck technique senior vs academy 1^st (p < 0.01, ES = 0.7, moderate), senior vs academy 2^nd (p < 0.01, ES = 0.4, small). These findings emphasize the importance of developing contact technique to allow players to progress to higher levels, and provide validity to an assessment tool which can facilitate this process.     

From activity to gestures and scientific language

Abstract: Gestures may provide the long sought‐for bridge between science laboratory experiences and scientific discourse about abstract entities. In this article, we present our results of analyzing students' gestures and scientific discourse by supporting three assertions about the relationship between laboratory experiences, gestures, and scientific discourse: (1) gestures arise from the experiences in the phenomenal world, most frequently express scientific content before students master discourse, and allow students to construct complex explanations by lowering the cognitive load; (2) gestures provide a medium on which the development of scientific discourse can piggyback; and (3) gestures provide the material that “glues” layers of perceptually accessible entities and abstract concepts. Our work has important implications for laboratory experiments which students should attempt to explain while still in the lab rather than afterwards and away from the materials. © 2000 John Wiley & Sons, Inc. J Res Sci Teach 38: 103–136, 2001     

The Developmental Sequence and Relations Between Gesture and Spoken Language in Toddlers With Autism Spectrum Disorder

In typical development, gestures precede and predict language development. This study examines the developmental sequence of expressive communication and relations between specific gestural and language milestones in toddlers with autism spectrum disorder (ASD), who demonstrate marked difficulty with gesture production and language. Communication skills across five stages (gestures, word approximations, first words, gesture-word combinations, and two-word combinations) were assessed monthly by blind raters for toddlers with ASD participating in an randomized control trial of parent-mediated treatment (N = 42, 12–30 months). Findings revealed that toddlers acquired skills following a reliable (vs. idiosyncratic) sequence and the majority of toddlers combined gestures with words before combining words in speech, but in contrast to the pattern observed in typical development, a significant subset acquired pointing after first words.     

Prenatal Risk Predicts Preschooler Executive Function: A Cascade Model

Little research has considered whether prenatal experience contributes to executive function (EF) development above and beyond postnatal experience. This study tests direct, mediated, and moderated associations between prenatal risk factors and preschool EF and IQ in a longitudinal sample of 1,292 children from the Family Life Project. A composite of prenatal risk factors (i.e., low birth weight, prematurity, maternal emotional problems, maternal prepregnancy obesity, and obstetric complications) significantly predicted EF and IQ at age 3, above quality of the postnatal environment. This relationship was indirect, mediated through infant general cognitive abilities. Quality of the postnatal home and child-care environments did not moderate the cascade model. These findings highlight the role of prenatal experience as a contributor to individual differences in cognitive development.     

Academic socialization,parental educational expectations,and academic self‐efficacy among Latino adolescents

This study examined the direct association between parental educational expectations and adolescents’ academic self‐efficacy, as well as the moderating influence of parental academic socialization messages. Participants were 148 Latino parent–adolescent dyads with the majority of Mexican origin (80.4%). Most of the parent participants were mothers (85.8%). Adolescents were 13 (46%) or 14 (54%) years of age, and 53% identified as female. Adolescents reported their academic self‐efficacy and perceptions of their parents’ educational expectations; parents reported on their academic socialization messages of shame/pressure and effort regarding academics. The results suggest that, after accounting for parents’ level of education and immigrant status, parental educational expectations were positively associated with adolescent academic self‐efficacy. This association was stronger among adolescents whose parents reported transmitting fewer messages of shame/pressure and academic effort. These results point to the importance of nuances in the content and type of academic socialization messages within Latino families.     

Correction to: Computational Thinking,Between Papert and Wing

Science & Education -     

Writing Characteristics of Students with Attention Deficit Hyperactive Disorder: A Meta‐Analysis

Students with Attention Deficit Hyperactivity Disorders (ADHD) frequently experience significant difficulty mastering basic academic skills. This meta‐analysis focuses on one specific potential area of learning difficulties for these students: namely, writing. To identify the extent and depth of the potential writing challenges faced by students with ADHD, we conducted a meta‐analysis comparing the writing performance of grade 1 to 12 students with ADHD to their normally achieving peers. We located 44 papers, yielding 45 studies with 87 effect sizes. The average weighted effect sizes showed that students with ADHD obtained lower scores than their normally achieving peers for writing quality (–0.78), output (–0.64), number of genre elements (–0.69), vocabulary (–0.76), spelling (–0.80), and handwriting (–0.62). Contrary to expectations, moderator analyses found that neither study quality nor the source from which ADHD students were drawn (i.e., school/community vs. clinic/hospital) accounted for variability above sampling error alone.     

Population density and nonaggressive competition

The Calhoun (1962) paper has become a keystone article for the population density literature. Although a few research reports have followed, several aspects of population density and the behavioral phenomena identified by Calhoun have been ignored. For example, the consummatory behavior in-aggregate property of the behavioral sink is an unstudied phenomenon. Furthermore, although the literature on potential population reduction mechanisms has grown rapidly, the mechanisms of pup mortality (cannibalization by adults) as identified by Calhoun has not been pursued systematically. Finally, the question of whether social or spatial density or other factors constitute the potent variables in the development of social pathology has not been tested directly. The purpose of these five related experiments was to investigate aspects of these behaviors.