Validity and reliability of a novel optoelectronic device to measure movement velocity,force and power during the back squat exercise

This study analysed the validity and reliability of a new optoelectronic device (Velowin) for the measurement of vertical displacement and velocity as well as to estimate force and mechanical power. Eleven trained males with Mean (SD) age = 27.4 (4.8) years, completed an incremental squat exercise test with 5 different loads (<30–90% of their 1?repetition maximum) while displacement and vertical velocity of the barbell were simultaneously measured using an integrated 3D system (3D motion capture system + force platform) and Velowin. Substantial to almost perfect correlation (concordance correlation coefficient = 0.75–0.96), root mean square error as coefficient of variation ±90% confidence interval ≤10% and good to excellent intraclass correlation coefficient = 0.84–0.99 were determined for all the variables. Passing and Bablock regression methods revealed no differences for average velocity. However, significant but consistent bias were determined for average or peak force and power while systematic and not proportional bias was found for displacement. In conclusion, Velowin, in holds of some potential advantages over traditionally used accelerometer or linear transducers, represents a valid and reliable alternative to monitor vertical displacement and velocity as well as to estimate average force and mechanical power during the squat exercise.     

Multiple-joint exercises using elastic resistance bands vs. conventional resistance-training equipment: A cross-over study

Previous studies indicate that elastic resistance bands (ERB) can be a viable option to conventional resistance-training equipment (CRE) during single-joint resistance exercises, but their efficacy has not been established for several commonly used multiple-joint resistance exercises. Thus, we compared muscular activation levels in four popular multiple-joint exercises performed with ERB (TheraBand^®) vs. CRE (Olympic barbell or cable pulley machines). In a cross-over design, men and women (n?=?29) performed squats, stiff-legged deadlifts, unilateral rows and lateral pulldown using both modalities. Multilevel mixed-effects linear regression analyses of main and interaction effects, and subsequent post hoc analyses were used to assess differences between the two resistance-training modalities. CRE induced higher levels of muscle activation in the prime movers during all exercises (p?<?.001 for all comparisons), compared to muscle activation levels induced by ERB. The magnitude of the differences was marginal in lateral pulldown and unilateral rows and for the erector spinae during stiff-legged deadlifts. In squats the quadriceps femoris activations were substantially lower for ERB. The differences between ERB and CRE were mostly observed during the parts of the contractions where the bands were relatively slack, whilst the differences were largely eliminated when the bands became elongated in the end ranges of the movements. We conclude that ERB can be a feasible training modality for lateral pulldowns, unilateral rows and to some extent stiff-legged deadlifts, but not for the squat exercise.     

战前西南商品市场个性分析

战前西南商品市场具有明显的半殖民地性、传统性和落后性。抗战爆发后,西南地区的市场开始由传统市场向近代市场转型。     

毛泽东抗日民族统一战线思想论析

毛泽东关于抗日民族统一战线思想坚持和发展了马克思主义关于统一战线的学说 ,它是中国人民赢得抗日战征胜利的重要思想武器。毛泽东关于抗日民族统一战线的思想对如何进一步做好新时期统一战线工作具有重要的现实意义 ,文章从四个方面对毛泽东抗日民族统一战线思想进行论析     

Race,culture and agency: Examining the ideologies and practices of U.S. teachers of Black male students

This study examines teachers of Black male students in a United States secondary school setting. Qualitative methods were used to document teachers' ideologies of and practices with their Black male students. In general, teachers drew upon competing structural and cultural explanations of Black male social and academic outcomes, while also engaging in practices that contested school barriers for Black males. Teacher beliefs about and practices with their Black male students were inconsistent in many ways, yet their agency on behalf of Black males might be understood as essential to Black male educational progress.     

运动改善胰岛素抵抗与脂联素水平变化关系的研究进展

脂联素是近年来新发现的脂肪细胞因子,与胰岛素敏感性（IS）密切相关。文章在简要概述其生物学的基础上,对近年来国内外有关运动影响脂联素水平与胰岛素抵抗（IR）改善的相关文献进行了回顾与总结,并对运动提高脂联素水平改善胰岛素抵抗的可能生物学机制从理论上进行了推测。     

基于最小阻力模型阜新市城市及农村居民点适宜性评价研究

阜新市作为资源枯竭型城市,矿产资源枯竭后有很多的“后遗症”,如沉陷、坍塌等地质灾害频现。综合考虑阜新市当前的自然地理条件、经济发展趋势、社会稳定等因素去确定城市的扩展及农村居民点的整治规划尤为重要。本文以阜新资源型城市为例,基于最小阻力模型对其城市及农村居民点适宜性评价进行研究,为其转型发展在用地选择上提供理论依据及决策支持。通过对资源型城市及农村居民点空间发展分析,从交通设施、矿产资源、地形地貌、土壤土质、灾害防治、土地利用类型及水体6个方面对阜新市城市与农村居民点发展建立阻力面,通过栅格计算得出阜新城市及农村居民点发展的综合阻力面。利用ArcGIS提取阜新市584个农村居民点的阻力值,对其发展适宜性评价,结果显示：阜新市的农村居民点中有40个需要优先整治,主要集中在阜蒙县与主城区南部及东南方向相邻地区;重点发展地区主要位于阜蒙县与主城区北部相邻的农村居民点及阜蒙县东部地区的居民点。利用ArcGIS下的空间分析工具,计算阜新市城市用地扩张累积阻力面,得出适宜城市发展的区域,并通过城市发展的辐射通道,得出城市扩展的适宜方向及战略点为阜新市的大固本镇和东梁镇与伊吗图镇交界处附近。     

运动锻炼的阻力--当代中国人"运动缺乏"现象的社会学追问

大多数国人都知道，自己需要更多的体育锻炼。但不幸的是，许多人的这一意识并未最终转化为积极的身体锻炼行为。主要就困扰现代中国人的“运动缺乏”现象和一些流行的观点展开追问。诸如，为什么人们明明知道自己缺乏运动却没有实际改变“究竟是什么妨碍了人们建立积极运动的生活方式？在发达国家（如美国）出现的“运动消极”式的生活方式在我国能否避免？如何使国人建构起积极运动的生活方式？研究认为：当前迫切需要的是对上述问题做出深层次的社会学解释。     

Line‐Fitting with Outliers

This article illustrates a method for fitting straight lines to data that is resistant to outliers and might therefore sometimes be preferred to the customary least squares procedure.