Optimal sampling frequency in recording of resistance training exercises     

Paolo Bardella  Irene Carrasquilla García  Marco Pozzo  Julio Tous-Fajardo  Eduardo Saez de Villareal 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(1):102-114

The purpose of this study was to analyse the raw lifting speed collected during four different resistance training exercises to assess the optimal sampling frequency. Eight physically active participants performed sets of Squat Jumps, Countermovement Jumps, Squats and Bench Presses at a maximal lifting speed. A linear encoder was used to measure the instantaneous speed at a 200 Hz sampling rate. Subsequently, the power spectrum of the signal was computed by evaluating its Discrete Fourier Transform. The sampling frequency needed to reconstruct the signals with an error of less than 0.1% was f_99.9 = 11.615 ± 2.680 Hz for the exercise exhibiting the largest bandwidth, with the absolute highest individual value being 17.467 Hz. There was no difference between sets in any of the exercises. Using the closest integer sampling frequency value (25 Hz) yielded a reconstruction of the signal up to 99.975 ± 0.025% of its total in the worst case. In conclusion, a sampling rate of 25 Hz or above is more than adequate to record raw speed data and compute power during resistance training exercises, even under the most extreme circumstances during explosive exercises. Higher sampling frequencies provide no increase in the recording precision and may instead have adverse effects on the overall data quality.  相似文献   

一种基于混合模型的合成孔径雷达自聚焦算法     

杨洋  王岩飞 《中国科学院大学学报》2016,33(5):656-663

提出一种基于混合模型的合成孔径雷达自聚焦算法.本方法用有限阶泰勒多项式估计低频相位误差，用自适应正弦多项式估计高频相位误差，解决了单一模型自聚焦算法对高频相位误差估计精度低的问题，提高了图像锐度和峰值旁瓣比，减小了主瓣宽度.在研究利用相位误差参数模型进行聚焦处理的基础上，分析基于混合模型实现最优锐度自聚焦算法的可行性，并通过仿真和实测数据处理验证了本方法的有效性.  相似文献   

Transmission of vibration from a vibrating plate to the head of standing people     

Naser Nawayseh 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(5):482-500

Little is known about the transmission of vibration to the head when using whole-body vibration (WBV) training machines. This paper investigates the effect of frequency and posture on the transmission of vibration from a vibrating plate to the head of standing people. Nine male participants were exposed to vertical vibration at nine frequencies in the range of 17–46 Hz and vibration acceleration in the range of 7.85–18.64 m/s² (peak). The participants adopted four standing postures described as standing with locked knee (LK), bent knee (BK), one leg (OL), and one foot to the front and the other to the back (FB). The transmissibility to the head differed among postures (t-test, p < 0.05) and was greatest with the FB posture and smallest with the BK posture. The transmissibility to the head decreased with increasing the frequency (t-test, p < 0.05) but the extent of the decrease depended on the adopted posture. This frequency-posture interaction effect on the transmissibility should be considered when designing a training program. The data will be useful for developing standards/protocols that govern the use of WBV machines as well as for building human body models that can predict potential risks arising from using WBV machines.  相似文献   

不凝结气体对蒸汽浸没射流压力振荡的影响     

从跃磊  王迎春  陈伟雄  种道彤  严俊杰 《中国科学院大学学报》2017,34(2):135-140

通过实验研究不凝结气体（空气）对蒸汽浸没射流压力振荡特性的影响。结果表明：不凝结气体存在时压力振荡强度比纯蒸汽浸没射流时明显减小。随空气质量分数的增加，压力振荡峰值的位置沿轴向后移。过冷水温低于45℃时，峰值随空气质量分数的增加而增大；高于50℃时，随空气质量分数的增加而减小；水温在45~50℃之间时，峰值大致相同。压力振荡主频随空气质量分数、蒸汽质量流率和过冷水温度的增加而减小。  相似文献   

Are gait characteristics and ground reaction forces related to energy cost of running in elite Kenyan runners?     

J. Santos-Concejero  N. Tam  D. R. Coetzee  J. Oliván  T. D. Noakes  R. Tucker 《Journal of sports sciences》2017,35(6):531-538

The aim of this study was to determine whether gait cycle characteristics are associated with running economy in elite Kenyan runners. Fifteen elite Kenyan male runners completed two constant-speed running sets on a treadmill (12 km ·h^?1 and 20 km ·h^?1). VO₂ and respiratory exchange ratio values were measured to calculate steady-state oxygen and energy cost of running. Gait cycle characteristics and ground contact forces were measured at each speed. Oxygen cost of running at different velocities was 192.2 ± 14.7 ml· kg^?1· km^?1 at 12 km· h^?1 and 184.8 ± 9.9 ml· kg^?1· km^?1 at 20 km· h^?1, which corresponded to a caloric cost of running of 0.94 ± 0.07 kcal ·kg^?1·km^?1 and 0.93 ± 0.07 kcal· kg^?1· km^?1. We found no significant correlations between oxygen and energy cost of running and biomechanical variables and ground reaction forces at either 12 or 20 km· h^?1. However, ground contact times were ~10.0% shorter (very large effect) than in previously published literature in elite runners at similar speeds, alongside an 8.9% lower oxygen cost (very large effect). These results provide evidence to hypothesise that the short ground contact times may contribute to the exceptional running economy of Kenyan runners.  相似文献   

新媒体语境特征与用户态度关系构建的实证研究     

薛可  阳长征  余明阳 《湖南师范大学社会科学学报》2015,(3):153-160

通过对上海市民进行抽样调查,并使用结构方法模型对新媒体语境下的受众社会态度倾向进行实证研究,得出如下结论：新媒体语境通过社会懈怠对用户风险偏好和群体极化倾向产生正向影响,对责任与公平意识、道德发展以及亲社会倾向产生负向影响;媒体接触频率在新媒体与社会懈怠关系中具有显著正向调节作用,而媒体接触的多样性在其中的调节作用并不明显;在主效应和调节作用中,均表现出对男性的影响大于对女性的影响,其影响大小随着年龄的增加而呈减弱趋势。  相似文献   

2005-2014年图书情报学4刊发文著者的统计分析     

黄勤 《金陵科技学院学报(社会科学版)》2015,(2)

通过对2005—2014年图书情报学4刊论文著者的统计,对合著率、著者发文规律、高产著者年龄、地区及单位分布进行分析,并归纳国内图书情报学的发展规律。  相似文献   

《高频电子线路》课程“振幅解调”教学策略     

李娜  唐永刚  宗素兰  常红霞 《巢湖学院学报》2015,(3):160-164

介绍两种常用的调幅信号解调方法,即同步检波法、包络检波法。采用对比教学法帮学生建立振幅解调的完整知识体系。引导学生设计简易二极管包络检波电路并观察解调失真。初步探索在高频电子线路课程中理论、实践相结合的新思路、新途径。  相似文献   

How much exercise are older adults living in nursing homes doing in daily life? A cross-sectional study     

Philipe De Souto Barreto  Laurent Demougeot  Bruno Vellas  Yves Rolland 《Journal of sports sciences》2015,33(2):116-124

Information on the amount of exercise practised by nursing home (NH) residents is scarce. This study aimed at describing NH residents’ participation in exercise classes, as well as to examine whether the presence of a professional exercise instructor in the facilities is associated with residents’ exercise habits. The cross-sectional data of 5402 residents (median age = 88 years; mostly women (75.2%)) from 163 NHs in France were analysed. Adjusted logistic and linear regressions were performed to examine whether the presence of a professional exercise instructor in the NH was associated with exercise habits: exercise participation, frequency, duration, and levels. From the 5402 participants, 1914 were participating in exercise classes provided in the NH. Most of them had an exercise frequency of 1x/week or less. Median duration of exercise sessions was 45 min. Exercise levels were rated as: highly active (n = 487), intermediately active (n = 1096), and poorly active (n = 331). The presence of a professional exercise instructor working in the facility was significantly associated with exercise participation and with higher exercise frequencies and levels, and session duration. In conclusion, the presence of professional exercise instructors is associated with better exercise habits in NH residents. Improved exercise habits may potentially be translated into better health in this population.  相似文献   

我国英语专业学生话语标记使用策略调查分析     

陈建春 《滨州学院学报》2011,27(1):121-124

话语标记语对话语的整体连贯和构建起着重要作用。运用大量的真实语料调查了我国学生口语话语标记的使用情况,并从定量、定性的角度分析比较高分组和低分组学生使用话语标记时存在的差异及导致这种结果的可能原因,将对二语学习者提高口语会话策略、口语教学和口语能力测评等提供一定的借鉴意义。  相似文献