Does maximising ball speed in cricket fast bowling necessitate higher ground reaction forces?

This study aimed to investigate whether high peak ground reaction forces and high average loading rates are necessary to bowl fast. Kinematic and kinetic bowling data were collected for 20 elite male fast bowlers. A moderate non-significant correlation was found between ball speed and peak vertical ground reaction force with faster bowlers tending to have lower peak vertical ground reaction force (r = ?0.364, P = 0.114). Faster ball speeds were correlated with both lower average vertical and lower average horizontal loading rates (r = ?0.452, P = 0.046 and r = ?0.484, P = 0.031, respectively). A larger horizontal (braking) impulse was associated with a faster ball speed (r = 0.574, P = 0.008) and a larger plant angle of the front leg (measured from the vertical) at front foot contact was associated with a larger horizontal impulse (r = 0.706, P = 0.001). These findings suggest that there does not necessarily need to be a trade-off between maximum ball release speed and the forces exerted on fast bowlers (peak ground reaction forces and average loading rates). Furthermore, it appears that one of the key determinants of ball speed is the horizontal impulse generated at the ground over the period from front foot contact until ball release.     

Reliability of accelerometry to assess impact loads of jumping and landing tasks

Overuse injuries, resulting from repetitive subacute impact loading, are a problem in high-performance sports. Monitoring of impact loading may aid in the prevention of these injuries. The current study aimed to establish the intra-day and inter-day reliability of a tri-axial accelerometer to assess impact loading during jumping and landing tasks. Twelve participants wore an accelerometer on their upper and lower back. They performed a continuous hopping task as well as drop landings and rebound jumps from three drop heights (37.5, 57.5 and 77.5 cm), peak resultant acceleration (PRA) was calculated for all tasks. The tasks were performed twice, one week apart at the same time of day. The difference in the mean, intra-class correlation coefficient, coefficient of variation and Cohen’s effect size were calculated as measures of reliability. PRA showed good intra-day reliability for the hopping task. Inter-day reliability of the PRA was moderate to good across all tasks. Reliability of PRA was slightly higher when accelerations were recorded on the lower back compared to the upper back. To assess impact loading, during continuous hopping, drop landings and rebound jumps, PRA recorded at both the upper and lower back appears to be a reliable measure.     

Do accelerometers mounted on the back provide a good estimate of impact loads in jumping and landing tasks?

Artistic gymnasts are frequently exposed to both low- and high-magnitude loads through impacts with the apparatus. These impact loads are thought to be associated with the high injury rates observed in gymnastics. Due to the variable apparatus and surfaces in gymnastics, impact loads during training are difficult to quantify. This study aimed to use triaxial accelerometers mounted on the back to assess impact loading during jumping and landing tasks. Twelve participants were fitted with an accelerometer on their upper and lower back, before performing a continuous hopping task, as well as drop landings and rebound jumps from various heights (37.5, 57.5, and 77.5 cm) onto a force platform. Peak resultant acceleration (PRA) was low-pass filtered with four cut-off frequencies (8, 15, 20, and 50 Hz). Filtering of PRA with the 20 Hz cut-off frequency showed the highest correlations between ground reaction force (GRF) and PRA. PRA recorded at the upper back, filtered with a 20 Hz cut-off frequency, appears to provide a good estimate of impact loading for continuous hopping and rebound jumps, but less so for drop landings since correlations between GRF and PRA were only significant when landing from 57.5 cm.     

用C语言递归建立二叉排序树的研究

建立与遍历一棵二叉树历来为数据结构中不可缺少的内容。由于C语言仅有单向的"值传递",所以多年来数据结构教课书中,皆使用指针函数来编程,进而增加了教师在讲述中的复杂性。构造一个用递归函数建立二叉树的C语言程序,可以解决多年来C语言教课书中没有解决的问题。     

汉语词义理据隐化的修辞阐释

汉语词义除了一大部分具有显性理据外,还有相当一部分的理据处于隐性状态或隐化过程中,形成原因多半与修辞有关。     

可编程序控制器和可编程序终端在地温中央空调中的应用

详细阐述了用欧姆龙公司的可编程序控制器、可编程序终端及温度传感器单元组成的地温中央空调控制系统的控制原理、控制方法。     

ASON技术及其发展

ASON是下一代智能光网络,代表了未来智能光网络发展的主流方向。分析了ASON的主要特点,介绍了ASON的体系结构、组网方案以及网络结构模型,总结了ASON的未来市场发展方向。     

复合土钉墙在江阴地区基坑围护中的应用

复合土钉墙在江阴软土地区某基坑支护中的应用取得了良好的效果，结合某住宅工程地下室的工程实例，论述了这项技术的施工要点，总结了应用过程中的经验教训。     

煤巷锚杆受相邻采面矿压影响分析

本文通过全过程、全方位的跟踪矿压观测，采取数据统计分析方法，对动压煤巷锚杆支护在成巷期间受相邻采面影响时的矿压关系进行分析，提出了类似条件下锚杆科学支护的依据。     

城市高架路-匝道-地面交通的交互作用及交通流特性研究

Therapiddevelopmentoftheautomobileindustry andtherelativelagoftheroadconstructionhavecon stitutedaprominentcontradictionallovertheworld, particularly,inmostoflargecities.Tocopewithit, elevatedroadshavebeenbuiltinmanycitiesbothat homeandabroad.However,tra…