Reliability of power output measurements during repeated treadmill sprinting in rugby players

The non-motorized treadmill system initially reported by Lakomy in 1984 has been used extensively to assess sprinting performance. However, there has been limited research into the reliability of power output measurement using such systems. The aim of this study was to design a system and protocol capable of measuring treadmill sprinting performance in rugby players and to assess the reliability of this system for measuring power output. Twenty-seven rugby players, all of whom were familiar with treadmill sprinting, performed three maximal 6 s sprints with 2 min recovery between sprints, on two occasions 1 week apart. Both tests were performed on a non-motorized Woodway tramp treadmill, interfaced to a data acquisition system. There were no significant differences ( P > 0.05) between power output for repeated trials on the same day (between trials) or for repeated trials on different days (between days). Limits of agreement for maximum average power (the average of 100 readings per second) were 4 - 98 and 30 - 157 W for between trials and between days, respectively. When reported as ratio limits of agreement, these were 1.07 (*/ 1 1.12) and 1.03 (*/ 1 1.16), respectively. The limits of agreement for maximum instantaneous power (the highest of 100 readings per second) were 51 - 464 and 105 - 588 W for between trials and between days, respectively. When reported as ratio limits of agreement, these were 1.02 (*/ 1 1.20) and 1.04 (*/ 1 1.21) for between trials and between days, respectively. The coefficients of variation for all measures of power output were less than 9.3%. Hence, the treadmill system and protocol developed in this study provide a reliable measure of power output for rugby players.     

The Variability of Practice Hypothesis: Further Tests and Methodological Discussion

Abstract

In the present study experimental subjects practiced variations in movement distance and/or movement time during training trials on a closed timing task. Control subjects trained with single distance-time combinations. During transfer trials all subjects attempted (without knowledge of results) a distance-time combination that was different (except in the case of one control condition) from any performed during training. The results revealed that the timing accuracy of the two experimental conditions that practiced a variety of times was significantly poorer than that of most of the other conditions during the training phase. However, transfer analyses revealed several significant differences between the performance of variable-trained and constant-trained conditions, in all cases favoring the former. It was concluded that the transfer benefits of variable practice are (a) not due to the particular movement component selected for variation during training, and (b) to some extent always determined by the similarity of training and transfer conditions experienced by constant-practice subjects.     

Childhood maltreatment and conduct disorder: Independent predictors of criminal outcomes in ADHD youth

ObjectiveChildren with attention-deficit/hyperactivity disorder (ADHD) are at heightened risk for maltreatment in childhood and criminality as they enter into adolescence and early adulthood. Here, we investigated the effect of moderate to severe childhood maltreatment on later criminality among adolescents/young adults diagnosed with ADHD in childhood while accounting for the contributions of other known risk factors such as early conduct disorder (CD).MethodsEighty-eight participants from a longitudinal study of children diagnosed with ADHD and screened for comorbid disorders at age 7–11 years were assessed for maltreatment histories at the time of the 10-year adolescent follow-up. Detailed juvenile and adult criminal records were obtained from the New York State Division of Criminal Justice Services approximately 3-years after commencement of the follow-up study. We used regression analyses to determine predictors of adolescent/young adult criminal behavior.ResultsModerate to severe childhood maltreatment increased the risk of adolescent/young adult arrest over and above the risk associated with childhood CD, while both childhood maltreatment and childhood CD significantly increased the risk of recidivism. ADHD youth classified as maltreated were three and a half times more likely to be arrested when compared to ADHD youth without a maltreatment classification.ConclusionWe established maltreatment as a risk factor for criminality in ADHD youth and demonstrated that this relationship was independent of the contributions of CD, and established risk factor for antisocial behavior in this population. The findings highlight the need for maltreatment screening in children with ADHD in order to identify those at heightened risk for criminal activity, and target treatment to improve outcome in this high-risk group of children.     

Variation in children's classroom engagement throughout a day in preschool: Relations to classroom and child factors

This study examined sources of variability in preschool children's positive and negative engagement with teachers, peers, and tasks, and how that variability was related to both classroom activity settings (e.g., teacher-structured time, outdoor time, transitions) and child factors (age, gender). Participants were 283 socioeconomically and linguistically diverse children drawn from 84 classrooms, 34–63 months old (M = 50.8, SD = 6.5). Each child's engagement was observed and rated multiple times within a single day. Results suggested that children's engagement varied significantly across the preschool day. Activity settings that provided children with a greater degree of choice (free choice and outdoor time) were associated with more positive engagement with peers and tasks, while teacher-structured activities were associated with more positive engagement with teachers. Transitions emerged as a difficult part of the day, associated with less positive engagement with teachers and tasks. Older children were rated higher on peer and task engagement. These findings, together with previous research, suggest that both characteristics of the classroom setting and child factors are associated with children's classroom engagement throughout a day in preschool.     

Individual differences in lexical processing at 18 months predict vocabulary growth in typically developing and late-talking toddlers

Using online measures of familiar word recognition in the looking-while-listening procedure, this prospective longitudinal study revealed robust links between processing efficiency and vocabulary growth from 18 to 30 months in children classified as typically developing (n = 46) and as "late talkers" (n = 36) at 18 months. Those late talkers who were more efficient in word recognition at 18 months were also more likely to "bloom," showing more accelerated vocabulary growth over the following year, compared with late talkers less efficient in early speech processing. Such findings support the emerging view that early differences in processing efficiency evident in infancy have cascading consequences for later learning and may be continuous with individual differences in language proficiency observed in older children and adults.     

Getting Everyone to the Fair: Supporting Teachers in Broadening Participation in Science and Engineering Fairs

Journal of Science Education and Technology - Science and Engineering (S&E) fairs are a valuable educational activity and are believed to increase students’ engagement and learning in...     

英国剑桥大学的管理及运行机制

剑桥大学作为世界著名大学,其管理和运行机制有独到之处。对其办学体制、招生情况、财政状况、管理体制等方面进行系统的分析,总结其成功经验,对中国高校的经营和管理有一定借鉴意义。     

Young Children's Understanding of Changes in Their Mental States

3-year-old children have difficulty reporting their past false beliefs. We investigated their ability to remember and report other types of past mental state, in particular, pretenses, images, perceptions, desires, and intentions. In a series of tasks, children were placed in one mental state, that state was changed, and they were asked to report the initial state. 4-year-olds were generally able to report all their past mental states, including beliefs. 3-year-olds were able to report past pretenses, images, and perceptions extremely well. They had great difficulty reporting past beliefs. Reporting past desires and intentions was more difficult than reporting pretenses, images, and perceptions, but slightly less difficult than reporting beliefs. The evidence suggests that 3-year-olds have difficulty understanding the nature of representation.     

Cross-modality contrast: Exteroceptive context habituation enhances taste neophobia and conditioned taste aversions

The relationship between absolute and relative stimulus novelty was examined within the context of the conditioned taste aversion paradigm in which the relative novelty of the conditioned interoceptive stimulus was manipulated by differential exteroceptive context habituation. Rats received similar isolation histories but either 5 or 30 days of habituation to the test environment prior to treatment. One group was administered lithium chloride following saccharin consumption, a second group was administered isotonic saline following saccharin consumption, and a third group was administered saline after water consumption. The animals habituated for 30 days exhibited greater conditioned avoidance and greater neophobic avoidance of saccharin than did animals habituated for only 5 days. The results are interpreted in terms of a cross-modality stimulus contrast effect which implicates context habituation as an important parameter of both taste neophobia and taste aversion learning.     

Orthographic processing and visual sequential memory in unexpectedly poor spellers

Does unexpectedly poor spelling in adults result from inferior visual sequential memory? In one experiment, unexpectedly poor spellers performed significantly worse than better spellers in the immediate reproduction of sequences of visual symbols, but in a second experiment, the effect was not replicated. Poor spellers were also no worse at the immediate recognition of symbol sequences. Overall, the results indicate that inferior visual memory is not characteristic of unexpectedly poor spellers. However, they do have less efficient orthographic processing skill: they were significantly slower and more error prone than better spellers at classifying both regularly and strangely spelt words, as well as at detecting letter transpositions in long words. They can thus be considered as subtly worse word readers than better spellers. While the findings question the notion of unexpectedly poor spelling in relation to normal adults, they provide confirmation of the intimate relationship between reading and spelling processes.