Assessment of leg muscles mechanical capacities: Which jump,loading, and variable type provide the most reliable outcomes?

This study aimed to explore the strength of the force–velocity (F–V) relationship of lower limb muscles and the reliability of its parameters (maximum force [F₀], slope [a], maximum velocity [V₀], and maximum power [P₀]). Twenty-three men were tested in two different jump types (squat and countermovement jump: SJ and CMJ), performed under two different loading conditions (free weight and Smith machine: Free and Smith) with 0, 17, 30, 45, 60, and 75?kg loads. The maximum and averaged values of F and V were obtained for the F–V relationship modelling. All F–V relationships were strong and linear independently whether observed from the averaged across the participants (r?≥?0.98) or individual data (r?=?0.94–0.98), while their parameters were generally highly reliable (F₀ [CV: 4.85%, ICC: 0.87], V₀ [CV: 6.10%, ICC: 0.82], a [CV: 10.5%, ICC: 0.81], and P₀ [CV: 3.5%, ICC: 0.93]). Both the strength of the F–V relationships and the reliability of their parameters were significantly higher for (1) the CMJ over the SJ, (2) the Free over the Smith loading type, and (3) the maximum over the averaged F and V variables. In conclusion, although the F–V relationships obtained from all the jumps tested were linear and generally highly reliable, the less appropriate choice for testing the F–V relationship could be through the averaged F and V data obtained from the SJ performed either in a Free weight or in a Smith machine. Insubstantial differences exist among the other combinations tested.     

振动力量训练对跳远运动员膝关节肌力变化影响的实验

为了拓宽专项力量训练途径,丰富和创新力量训练方法,通过振动力量训练组(II组)和传统力量训练组(I)对比实验研究来探索振动力量训练对跳远运动员下肢肌肉力量训练效果的影响规律,为进一步振动力量训练发展和应用提供实验依据。实验结果表明:振动力量训练法能在同等的负荷条件下,能更有效地发展运动员膝关节屈肌群的最大力量、快速力量、爆发力,其中伸肌表现不明显;振动力量训练也提高了运动员的膝关节肌群力量耐力水平,同时使膝关节屈伸肌群得到协调发展。     

钱塘江排桩式丁坝在涌潮作用下的受力分析

排桩式丁坝是一种新型的水工结构,利用弹性地基梁法和自编的有限元程序计算分析了涌潮作用下的钱塘江排桩式丁坝的内力,研究分析了排桩式丁坝在涌潮作用下的受力机理。前排桩和后排桩的受荷模型不同、刚度不同,导致其桩身内力不同。理论计算和现场测试结果的对比表明,可参考基坑围护工程中的排桩设计理论指导钱塘江排桩式丁坝的设计,并建议采用假定条件较少的有限元法计算分析,使结果更加科学合理,符合实际情况。     

高新技术创业动力的经济学分析

高新技术创业是创业者为了实现其特定的创业目标依托高新技术而开展的一个搜寻和捕获机会并由此创造新颖产品或服务的过程。对创业利益的追求是高新技术创业活动得以进行的基本动力,创业利益的预期值和创业成功的概率决定着创业过程的基本形态和特殊形态,同时获得创业利益的多少也是判断高新技术创业成功与否的重要标准之一。     

体校学生田径训练中单足跳发展下肢爆发力的研究

文章对体校学生爆发力训练进行了理论研究,提出了爆发训练的专项性原则及应注意的问题,并确定了体校学生单腿训练的依据及方法,希望借此对体校的教学与训练提供一定参考。     

中国女子排球运动员后备力量相关指标剖析

调研以提高中国女子排球运动竞技水平为目的,以选拔、培养国家女排后备力量为组织核心的数届全国青年女排集训比赛的运动员为主要研究对象,采用文献资料、数理统计等方法,对其身体形态和专项身体素质数据进行分析。研究认为：近三年来全国青年女子排球运动员的年龄征象、身高水平相对稳定;主攻、副攻、二传、接应的体重、指高差异不显著、专位特色不鲜明;助跑摸高、6m×16次移动水平停滞不前;下肢垂直与水平爆发力等专项素质亟待提高;相关指标数据与国家女排运动员、甲A女排运动员有较大差距;身材高大的运动员仍较缺乏。     

简论推动现代排球运动发展的主要动力

本文对排球运动发展的历史过程进行分析、探讨,并从哲学角度运用自然辩证法进行论证,发现以寻求攻防平衡为目的的规则改变不断地改进和完善排球运动,使排球运动更加激烈、精彩;另外不同时期人们对排球各种功能的需求也有效地推动了排球运动的发展。它们是推动排球运动发展的主要因素。更好地把握和利用排球运动发展的动因能更好地促进排球运动的发展。     

Predicting ground reaction forces in running using micro-sensors and neural networks

Measurement of ground reaction force (GRF) in running provides a direct indication of the loads to which the body is subjected at each foot-ground contact, and can provide an objective explanation for performance outcomes. Traditionally, the collection of three orthogonal component GRF data in running requires an athlete to complete a series of return loops along a laboratory based runway, within which a force platform is embedded, in order to collect data from a discrete footfall. The major disadvantages associated with this GRF data collection methodology include the inability to assess multiple consecutive foot contacts and the fact that measurements are typically confined to the laboratory. The objective of this research was to investigate the potential for wearable instrumentation to be employed, in conjunction with artificial neural network (ANN) and multiple linear regression (MLR) models, for the estimation of GRF in middle distance running. A modular wearable data acquisition system was developed to acquire in-shoe force (ISF) data. Matched data sets from wearable instrumentation (source data) and force plate (target data) records were collected from elite middle-distance runners under controlled laboratory conditions for the purposes of ANN and MLR model development (MD) and model validation (MV). In terms of statistical measures of prediction accuracy the MLR model was found to provide a superior level of accuracy for the prediction of the vertical and medio-lateral components of GRF and alternatively, the ANN model provided the most accurate predictions of the anterior-posterior component of GRF. The prediction accuracy of each component of GRF was found to be governed by the inherent signal variability, in which case the vertical and anterior-posterior components were more reliable and subsequently predicted significantly more accurately than the medio-lateral component. The emerging capability for obtaining continuous GRF records from wearable instrumentation has the potential to permit unprecedented quantification of training stress and competition demands in running.     

Device for on-the-water measurement of rowing output

All those who compete in the sport of rowing have used the land rowing machine, Ergometer (commonly called the ‘erg’), manufactured by Concept II (Morrisville, Vermont, USA). Ergon is the Greek word for work, hence the Ergometer measures work. Rowers are commonly ranked according to their ‘erg score.’ The fault in this ranking is that the land Ergometer cannot account for many of the important technical aspects associated with rowing on the water. The goals of this project were to (1) develop a system for on-the-water measurement of work during rowing and then (2) demonstrate the potential of such a system to quantify performance and improve rowing technique. To achieve these goals, force was measured using strain gauges glued to the shaft of the rowing oar and angular displacement was measured using a potentiometer. The force and displacement measurements were sent to a microcontroller, which calculated the total work done in a particular stroke, as well as other parameters, and displayed the values to the rower. The parameters were used to evaluate the performance of three collegiate rowers on the water. The data were also used to plot force profiles, which were reviewed with each rower and the coach to illustrate the rowers’ habits and facilitate improving technique. One rower was ‘tutored’ with the device through five on-the-water practices, after which his force profiles and parameter values demonstrated significant improvement. The device not only provided a standard to which all rowers were compared on the water, but also supplied the rowers with important information on technical aspects of their strokes and pacing themselves.     

中国群众体育参与的影响因素及驱动力研究简

采用主成分分析与因子分析法,对影响群众体育参与的10个因素进行数据矩阵分析。旨在准确把握中国群众体育参与影响因素和特征。分析确定主成分：驱动因子2个。包括：政府支持和体育发展因子、生活水平与文化素质因子。结果表明,政府支持和体育发展是群众体育参与的基础和保障,生活水平与文化素质影响群众对体育参与的规模与主动性。