The acute effects of bodyweight suspension exercise on muscle activation and muscular fatigue

This investigation examined effects of two exercise modes (barbell, BB; bodyweight suspension, BWS) on muscle activation, resistance load, and fatigue. During session one, nine resistance-trained males completed an elbow flexion one-repetition maximum (1RM). During sessions two and three, subjects completed standing biceps curls to fatigue at 70% 1RM utilizing a randomized exercise mode. Surface electromyography (sEMG) recorded muscle activation of the biceps brachii, triceps brachii, anterior deltoid, posterior deltoid, rectus abdominis, and erector spinae. BWS resistance load was measured using a force transducer. Standing maximal voluntary isometric contractions of the elbow flexors recorded at 90° were used to determine the isometric force decrement and rate of fatigue (ROF) during exercise. sEMG and resistance load data were divided into 25% contraction duration bins throughout the concentric phase. BWS resulted in a 67.7?±?7.4% decline in resistance load throughout the concentric phase (p?≤?0.05). As a result, BB elicited higher mean resistance loads (31.4?±?4.0?kg) and biceps brachii sEMG (84.7?±?27.8% maximal voluntary isometric contractions, MVIC) compared with BWS (20.4?±?3.4?kg, 63.4?±?21.6% MVIC). No difference in rectus abdominis or erector spinae sEMG was detected between exercise modes. Isometric force decrement was greater during BWS (?21.7?±?7.0?kg) compared with BB (?14.9?±?4.7?kg); however, BB (?3.0?±?0.8?kg/set) resulted in a steeper decline in ROF compared with BWS (?1.7?±?0.6?kg/set). The variable resistance loading and greater isometric force decrement observed suggest that select BWS exercises may resemble variable resistance exercise more than previously considered.     

Effectiveness and time-course adaptation of resistance training vs. plyometric training in prepubertal soccer players

PurposeThis study aimed to assess the effectiveness and time course for improvements in explosive actions through resistance training (RT) vs. plyometric training (PT) in prepubertal soccer players.MethodsThirty-four male subjects were assigned to: a control group (n = 11); an RT group (5 regular soccer training sessions per week, n = 12); a PT group (3 soccer training sessions and 2 RT sessions per week, n = 11). The outcome measures included tests for the assessment of muscle strength (e.g., 1 repetition maximum half-squat test), jump ability (e.g., countermovement jump, squat jump, standing long jump, and multiple 5 bounds test), linear speed (e.g., 20 m sprint test), and change of direction (e.g., Illinois change of direction test).ResultsThe RTG showed an improvement in the half-squat (Δ = 13.2%; d = 1.3, p < 0.001) and countermovement jump (Δ = 9.4%; d = 2.4, p < 0.001) at Week 4, whereas improvements in the 20-m sprint (Δ = 4.2%; d = 1.1, p < 0.01); change of direction (CoD) (Δ = 3.8%; d = 2.1, p < 0.01); multiple 5 bounds (Δ = 5.1%; d = 1.5, p < 0.05); standing long jump (Δ = 7.2%; d = 1.2, p < 0.01); squat jump (Δ = 19.6%; d = 1.5, p < 0.01); were evident at Week 8. The PTG showed improvements in CoD (Δ = 2.1%; d = 1.3, p < 0.05); standing long jump (Δ = 9.3%; d = 1.1, p < 0.01); countermovement jump (Δ = 16.1%; d = 1.2, p < 0.01); and squat jump (Δ = 16.7%; d = 1.4, p < 0.01); at Week 8 whereas improvements in the 20-m sprint (Δ = 4.1%; d = 1.3, p < 0.01); and multiple 5 bounds (Δ = 7.4%; d = 2.4, p < 0.001); were evident only after Week. The RT and PT groups showed improvements in all sprint, CoD, and jump tests (p < 0.05) and in half-squat performance, for which improvement was only shown within the RTG (p < 0.001).ConclusionRT and PT conducted in combination with regular soccer training are safe and feasible interventions for prepubertal soccer players. In addition, these interventions were shown to be effective training tools to improve explosive actions with different time courses of improvements, which manifested earlier in the RTG than in the PTG. These outcomes may help coaches and fitness trainers set out clear and concise goals of training according to the specific time course of improvement difference between RT and PT on proxies of athletic performance of prepubertal soccer players.     

小学体育教学培养学生抗挫力的分析

在素质教育新形势下,教育领域教学工作者的教学手段不断更新,逐渐改变了以往传统的教学模式,越来越多的注重学生综合能力的发展。现阶段的小学生,生活在幸福和平的年代,一直没有什么挫折出现在他们成长的过程中,因而抗挫折能力比较弱。本文主要针对小学生的抗挫折能力进行了分析,提出小学体育教学中培养学生抗挫折能力的具体策略。     

Effects of interrupting prolonged sitting on postprandial glycemia and insulin responses: A network meta-analysis

PurposeThis study aimed to evaluate the effectiveness of physical activity (PA) interrupting prolonged sitting (PS) on postprandial glycemia and insulin responses among adults.MethodsPubMed, EMBASE, Cochrane Library, Web of Science, CINAHL, PsycINFO, and the China National Knowledge Infrastructure databases were searched through September 30, 2020. Randomized controlled trials (RCTs) that examined the effect of all forms of PA interrupting PS on postprandial glycemia and/or insulin responses among adults without chronic diseases were included in this study. The risk of bias of included studies was evaluated based on the Cochrane tool. A network meta-analysis was performed to estimate the summary standardized mean differences (SMDs) with 95% confidence intervals (95%CIs) with random effects.ResultsThirty crossover RCTs were included in our review. These RCTs included 9 types of interventions that interrupted PS. When compared to PS by itself, light-intensity PA intermittent interrupting (LPA-INT) PS and moderate-intensity PA intermittent interrupting (MPA-INT) PS significantly lowered postprandial glycemia (SMD = –0.46, 95%CI: –0.70 to –0.21; SMD = –0.69, 95%CI: –1.00 to –0.37, respectively) and significantly reduced postprandial insulin response (SMD = –0.46, 95%CI: –0.66 to –0.26; SMD = –0.47, 95%CI: –0.77 to –0.17, respectively). Results of the clustered ranking plot indicated that MPA-INT was the most effective intervention in lowering postprandial glycemia and insulin responses.ConclusionReplacing PS with MPA-INT or LPA-INT has a positive effect in reducing postprandial glycemia and insulin responses, with MPA-INT being the optimal intervention strategy.     

一种针对骨骼肌和能量系统的新训练理念:逐步减负训练

目的:为了获得与每种运动类型相关的特定适应性,通常需要进行持续和间歇性运动,从而提出"逐步减负训练(SLRT)"作为一种新的训练方法在单一运动项目里来获得连续和间歇性的适应性;方法:运用文献资料法、逻辑分析法梳理SLRT对骨骼肌及能量系统的影响;结果:SLRT在抗阻训练中同时增加肌肉的大小、力量和耐力,在有氧和无氧代谢系统的训练当中同时增加最大无氧功率、无氧能力和有氧能力。     

浅谈电路中的负反馈

本文阐述了反馈的概念,并通过分析放大电路中引入各种形式负反馈后,电路性能和参数所发生的变化,向读者证明,放大电路中的负反馈可以多方面改善放大电路的性能.     

短波电台天线自动调谐系统检测器工作原理分析

本文对短波电台天线自动调谐系统中检测器的作用和工作原理进行了分析,为判断短波电台天线自动调谐系统的工作状态提供了依据,为部队装备正常使用和保障提供参考.     

Communication strategies to overcome functional and psychological resistance to Internet banking

This paper aims to investigate how customers experiencing different kinds of resistance to Internet banking perceive the information and guidance offered by the service provider. A postal survey was conducted and 251 effective responses from Internet banking non-users were received. Based on the earlier literature a typology of consumer resistance to innovations is proposed and four resistance segments, namely Non-Resistors, Functional Resistors, Psychological Resistors and Dual Resistors are identified. The results show that those customers reporting both functional and psychological resistance to Internet banking are more dissatisfied with the information and guidance offered by the service provider compared to those with only psychological resistance or no resistance to the innovation. Communication strategies to reduce and overcome different kinds of resistance to Internet banking are proposed.     

The implementation of the Spa Select System: Coming to grips with the cog in the machine

This paper illustrates the tribulations of implementing a technology-based system to aid management of information at a Spa and a Salon. While the implementation may itself appear to be rather simplistic, a number of issues of concern emerge. These range from inadequate planning, inability to define organizational processes, and resistance to change due to poor management of user skills and interests. While the organization eventually achieved the investment objective it had set out for itself, the process of implementation was riddled with problems—disgruntled employees, unfair compensation plans and a general discontentment with the system. The paper contextualizes a range of issues related to information management and how a technological solution resulted in resistance to change and business process management challenges.     

太行抗日根据地的粮食统制政策研究

抗日战争时期,在太行抗日根据地中国共产党经过艰辛探索后开始推行粮食统制政策,此政策的实施,不仅化解了粮食危机、保障了军粮供应,而且极大地促进了根据地的经济发展,为抗日战争的胜利作出了重要贡献。