活性氧代谢与植物的抗逆性

简述了植物体内活性氧的产生及其主要部位,活性氧对膜脂过氧化的启动以及活性氧对细胞膜系统结构的损伤,着重讨论了活性氧的清除与植物的抗逆性之间的关系,认为在各种逆境胁迫下,植物体内酶促与非酶促系统对活性氧的清除从而增强了植物的抗逆性,同时,应用一些外源新型植物生长调节剂可有效促进酶促系统清除活性氧,更好地增强植物对逆境的忍耐力。     

线性电路输入电阻的测量

讨论线性电路输入电阻的几种测量方法以及电压表内阻对测量的影响。     

Effect of cathodic protection on the fatigue crack growth behavior of low carbon alloy steels

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How many times per week should a muscle be trained to maximize muscle hypertrophy? A systematic review and meta-analysis of studies examining the effects of resistance training frequency

Training frequency is considered an important variable in the hypertrophic response to regimented resistance exercise. The purpose of this paper was to conduct a systematic review and meta-analysis of experimental studies designed to investigate the effects of weekly training frequency on hypertrophic adaptations. Following a systematic search of PubMed/MEDLINE, Scoups, and SPORTDiscus databases, a total of 25 studies were deemed to meet inclusion criteria. Results showed no significant difference between higher and lower frequency on a volume-equated basis. Moreover, no significant differences were seen between frequencies of training across all categories when taking into account direct measures of growth, in those considered resistance-trained, and when segmenting into training for the upper body and lower body. Meta-regression analysis of non-volume-equated studies showed a significant effect favoring higher frequencies, although the overall difference in magnitude of effect between frequencies of 1 and 3+ days per week was modest. In conclusion, there is strong evidence that resistance training frequency does not significantly or meaningfully impact muscle hypertrophy when volume is equated. Thus, for a given training volume, individuals can choose a weekly frequency per muscle groups based on personal preference.     

我国现代体能训练的现状、问题与发展路径

从20世纪90年代末开始,在借鉴国外职业体育先进经验和实践方法的基础上,我国的现当代体能训练逐渐进入我国高水平运动员备战奥运会的实践训练中。经过近20年的发展,我国现代体能训练发生了巨大变化。在竞技体育领域,中国女子排球、田径、游泳、自行车等项目在世界大赛上取得了骄人成绩,这与他们重视体能训练密不可分;在大众健身领域,普通老百姓对于增肌、塑型、减重、提高各种身体素质训练越来越重视,越来越火热,我国现代体能训练呈现出蓬勃发展的趋势。结果显示：（1）我国现代体能训练的发展历程发展分为四个阶段：一是理论引进阶段：20世纪90年代末期—2004年;二是学习消化阶段：2004年后期—2008年;三是吸收应用阶段：2008年奥运会后—2012年;四是蓬勃发展与创新阶段,2012年奥运会后至今。（2）我国现代体能训练面临的主要问题：一是现代体能训练起步较晚,理论研究落后于实践;二是现代体能训练理论与实践体系呈现“碎片化”状态;三是现代体能教练培养体系尚未形成;四是竞技体育与全民健身发展结构不平衡。（3）我国现代体能训练的未来发展路径：一是系统整合,推进我国现代体能训练体系的理论与实践由“碎片化”向“系统化”转变;二是重视体能教练员在训练中的地位,逐步建立现代体能教练培养系统;三是建立适合我国国情的现代体能训练理论与实践、培训与认证体系。     

短期低氧抗阻训练对男子体操运动员有氧、无氧运动能力的影响*

目的：探讨低氧环境下进行4周循环抗阻训练（CRT）对男子体操运动员有氧、无氧运动能力的影响,为科学化训练提供理论支持。方法：16名男子体操运动员随机分为低氧训练（hypoxia training,HT）组和常氧训练（normoxia training,NT）组,每组n＝8。NT组和HT组受试者分别于常氧和低氧（模拟3000 m高度）环境下进行4周CRT。实验前后利用递增负荷力竭实验（最大摄氧量、最大有氧功率等）测定有氧运动能力,利用运动场测试（300 m全力冲刺记时跑和300 m反复间歇跑测试）与实验室测试（股四头肌最大随意收缩、半蹲跳、下蹲跳和30 s Wingate实验）测定无氧运动能力,静脉取血测定血液学参数。结果：组内与实验前比较,实验后HT组300 m反复间歇跑完成次数、峰值LA含量（LApeak）、股四头肌最大随意收缩（MVC）、半蹲跳（SJ）、下蹲跳（CMJ）、峰值功率（PP）和平均功率（MP）显著性升高（P<0.05）,NT组LApeak、MVC、SJ、CMJ、PP和MP升高（P<0.05）;组间与NT组比较,实验后HT组300 m反复间歇跑完成次数、LApeak、MVC、SJ、CMJ、PP和MP升高（P<0.05）。有氧运动能力参数和血液学参数在两组实验前后均无显著性变化（P>0.05）。CRT过程中的平均心率（HRmean）在HT组高于NT组（P<0.05）。结论：低氧环境下进行CRT能够显著改善男子体操运动员无氧运动能力,其机制可能与耐乳酸能力增强有关,但对有氧运动能力无显著影响。     

Time-restricted feeding in young men performing resistance training: A randomized controlled trial†

A randomized controlled trial was conducted to examine eight weeks of resistance training (RT) with and without time-restricted feeding (TRF) in order to assess nutrient intake and changes in body composition and muscular strength in young recreationally active males. The TRF programme consisted of consuming all calories within a four-hour period of time for four days per week, but included no limitations on quantities or types of foods consumed. The RT programme was performed three days per week and consisted of alternating upper and lower body workouts. For each exercise, four sets leading to muscular failure between 8 and 12 repetitions were employed. Research visits were conducted at baseline, four, and eight weeks after study commencement. Measurements of total body composition by dual-energy X-ray absorptiometry and muscle cross-sectional area by ultrasound were obtained. Upper and lower body strength and endurance were assessed, and four-day dietary records were collected. TRF reduced energy intake by ～650?kcal per day of TRF, but did not affect total body composition within the duration of the study. Cross-sectional area of the biceps brachii and rectus femoris increased in both groups. Effect size data indicate a gain in lean soft tissue in the group that performed RT without TRF (+2.3?kg, d?=?0.25). Upper and lower body strength and lower body muscular endurance increased in both groups, but effect sizes demonstrate greater improvements in the TRF group. Overall, TRF reduced energy intake and did not adversely affect lean mass retention or muscular improvements with short-term RT in young males.     

Metabolic time-course response after resistance exercise: A metabolomics approach

This study analysed the time course of the global metabolic acute response after resistance exercise (RE), with the use of proton nuclear magnetic resonance (¹H NMR) spectroscopy. Ten young healthy males performed 4 sets of 10 repetitions at 70% of one-repetition maximum in the leg press and knee extension exercises and had the serum metabolome assessed at 5, 15, 30 and 60 min post-RE. Measurements were also performed 1 h earlier and immediately before the exercises, as an attempt to characterise each participant’s serum metabolome at rest. One-way ANOVA was applied and the significance level was set at P ≤ 0.05. RE promoted an increase in 2-hydroxybutyrate, 2-oxoisocaproate, 3-hydroxyisobutyrate, alanine, hypoxanthine, lactate, pyruvate and succinate concentrations. However, isoleucine, leucine, lysine, ornithine and valine had their concentrations decreased post-RE compared with at rest. This is the first study to show significant changes in serum concentration of metabolites such as 2-oxoisocaproate, 2-hydroxybutyrate, 3-hydroxyisobutyrate, lysine, hypoxanthine and pyruvate post-RE, attesting metabolomics as an interesting approach to advance in the understanding of global RE-induced metabolic changes. Moreover, the present data could influence the time point of blood collection in the future studies that aims to investigate metabolism and exercise.     

论行政权力公开运行的动力、阻力和发展趋势

政府权力属于公共权力.我国政府公开虽有多种提法,但实质强调的都是政府公共权力运行的公开.行政权力公开是核心内容,有着明确的反腐倡廉的指向性.公共权力即行政权力公开运行虽然已取得了显著的成就,但要继续深入开展就必须对政府公开的动力和可能遇到的阻力进行科学的分析,并采取增动力破阻力的有效措施,建立起长效机制,这是行政权力公开运行的发展趋势,也是当前面临的紧迫任务.     

冰上课中运用抗阻训练的实验研究

抗阻训练作为全面身体锻炼的重要方法,可以显著增长肌肉力量和体积,其在改善肌肉速度、平衡性、协调性、弹跳力、柔韧性等方面的素质效果明显。采用文献资料法及实验对比法,对抗阻训练的原理、抗阻训练的超量恢复、抗阻训练的交叉迁移、抗阻训练方案设计以及教学要求方面进行分析并进行了实验研究。实验结果显示：在冰上教学中运用抗阻训练能明显增加学生的体能储备,提高学生速滑技术水平;改变差生的弱势心理倾向,增强学习信心,从而提高了冰上课教学效果。