Tensiomyographical responses to accelerometer loads in female collegiate basketball players

The purpose of the present study was to characterise the relationship between relative versus absolute internal and external loads in collegiate basketball players throughout the course of a season. Five Division I basketball players wore triaxial accelerometers throughout the 2015–2016 season and were tensiomyographically assessed weekly. One-way repeated-measure analysis of variance (RM ANOVA) with least-significant-difference (LSD) pairwise comparisons was used to determine which absolute weekly loads were different across the season. Cohen’s d was used to supplement the determination of meaningful relative load changes. Overall RM ANOVA models suggest absolute external load differences occurred (PlayerLoad? F = 17.63; IMA? F = 31.63). Two-way RM ANOVA models revealed main effect differences were revealed between muscle groups for Tc (F = 9.11) and Dm (F = 3.25). Meaningful relative load changes between weeks were observed for both external and internal. The present study observed that tensiomyography utilised as a tool to monitor internal load may be more suitable for detecting fatigue from relative external load changes versus absolute load attained. Limiting weekly training volume changes to ≤10% may maintain appropriate adaptation. Mediolateral plane IMA? and adductor longus muscle group may be pertinent metrics when monitoring female collegiate basketball athletes.     

Kinematic and kinetic analysis of overhand,sidearm and underhand lacrosse shot techniques

Lacrosse requires the coordinated performance of many complex skills. One of these skills is shooting on the opponents’ net using one of three techniques: overhand, sidearm or underhand. The purpose of this study was to (i) determine which technique generated the highest ball velocity and greatest shot accuracy and (ii) identify kinematic and kinetic variables that contribute to a high velocity and high accuracy shot. Twelve elite male lacrosse players participated in this study. Kinematic data were sampled at 250 Hz, while two-dimensional force plates collected ground reaction force data (1000 Hz). Statistical analysis showed significantly greater ball velocity for the sidearm technique than overhand (P < 0.001) and underhand (P < 0.001) techniques. No statistical difference was found for shot accuracy (P > 0.05). Kinematic and kinetic variables were not significantly correlated to shot accuracy or velocity across all shot types; however, when analysed independently, the lead foot horizontal impulse showed a negative correlation with underhand ball velocity (P = 0.042). This study identifies the technique with the highest ball velocity, defines kinematic and kinetic predictors related to ball velocity and provides information to coaches and athletes concerned with improving lacrosse shot performance.     

Skating start propulsion: three-dimensional kinematic analysis of elite male and female ice hockey players

The forward skating start is a fundamental skill for male and female ice hockey players. However, performance differences by athlete’s sex cannot be fully explained by physiological variables; hence, other factors such as skating technique warrant examination. Therefore, the purpose of this study was to evaluate the body movement kinematics of ice hockey skating starts between elite male and female ice hockey participants. Male (n = 9) and female (n = 10) elite ice hockey players performed five forward skating start accelerations. An 18-camera motion capture system placed on the arena ice surface captured full-body kinematics during the first seven skating start steps within 15 meters. Males’ maximum skating speeds were greater than females. Skating technique sex differences were noted: in particular, females presented ~10° lower hip abduction throughout skating stance as well as ~10° greater knee extension at initial ice stance contact, conspicuously followed by a brief cessation in knee extension at the moment of ice contact, not evident in male skaters. Further study is warranted to explain why these skating technique differences exist in relation to factors such as differences in training, equipment, performance level, and anthropometrics.     

划船式短跑途中跑技术上肢动作描述及其数据证明

本文引用相关数据证明以下“划船式短跑途中跑技术[1]”是世界级水平部分运动员使用的技术;而低于世界级水平部分优秀运动员使用的是经典短跑途中跑技术。     

The differential effects of PNF versus passive stretch conditioning on neuromuscular performance

Abstract

The effects of flexibility conditioning on neuromuscular and sensorimotor performance were assessed near to full knee extension (25°). Eighteen males who were randomly assigned into two groups underwent eight weeks (three-times per week) of flexibility conditioning (hip region/knee flexor musculature; dominant limb) involving either proprioceptive neuromuscular facilitation (PNF) (n=9) or passive stretching (PASS) (n=9). Both modes of flexibility conditioning are popular within contemporary exercise and clinical settings and have demonstrated efficacy in improving range of motion. The contralateral limb and a prior ‘no exercise’ condition were used as controls. The PNF and PASS modes of conditioning improved passive hip flexibility to a similar extent (mean 19.3% vs. baseline, intervention limb, p<0.01) but did not alter knee flexor strength (overall mean 309.6±81 N) or sensorimotor performance (force and positional errors: 2.3±8.2% and 0.48±7.1%). Voluntary and magnetically evoked electromechanical delays (EMD_V and EMD_E, respectively) were increased but to a greater extent following PASS compared to PNF (PASS: 10.8% and 16.9% lengthening of EMD_V and EMD_E, respectively vs. PNF: 3.2% and 6.2%, p<0.01).The attenuated change to electromechanical delay (EMD) performance during PNF conditioning suggests a preserved capability for rapid muscle activation, which is important in the maintenance of dynamic joint stability. That PNF was also equally efficacious in flexibility conditioning would suggest that this mode of flexibility training should be used over passive to help preserve dynamic joint stability capabilities at this extended and vulnerable joint position.     

Kinematic analysis of the backstroke start: differences between backstroke specialists and non-specialists

Abstract

The purpose of this study was to clarify factors to perform the hole-entry technique in the backstroke start. A total of 16 well-trained Japanese competitive swimmers were divided into two groups (backstroke specialists and non-specialists) to compare their backstroke start motions. Their backstroke motions were videotaped, and two-dimensional co-ordinates for the swimmers were obtained from the video images using direct linear transformation methods. A non-paired t-test and Mann–Whitney U-test were used to analyse the statistical difference of the kinematic variables between the groups. Backstroke specialists showed a significantly shorter 5 m time (P = 0.009, effect size = –1.54), a significantly higher position of the toe (P = 0.010, effect size = 1.47) at signal and of the hip at toe-off (P = 0.002, effect size = 1.94), a significantly larger hip joint angle at toe-off (P = 0.007, effect size = 1.60) and a significantly higher angular velocities of the hip joints (45–85%; P < 0.05) for the normalised time as compared to that of non-specialists. An earlier initiation of the extension and the maintenance of a higher extension speed at the hip joints were important factors in achieving an arched-back posture, which facilitated and water entrance with a small entry range.     

一种改进的Richardson-Lucy正则化图像复原算法

运动模糊图像复原是模糊图像复原领域中的重要课题。首先,利用一种新的正则化方法有效估计了非参数运动模糊核。然后,在贝叶斯框架下,基于图像像素空间和梯度空间的统计特性,结合自然图像的梯度约束,提出了图像复原的改进RL正则化算法,有效抑制了复原图像中存在的振铃效应。实验结果表明,RL正则化算法在模糊核的估计存在误差时,依然能够得到较好的图像复原效果。     

意境说的道禅哲学渊源

中国古典美学中的意境说由情景交隔、虚实相生、动静相成、意在言外等四种美学范畴构成。其文化内涵源自道禅哲学中的“道德玄同，天人合一”，“有无相生”、“完全无妙有”、“无动而无不动”、“无言而无不言”、“不落言筌，不涉理路”等哲学理念。     

运用情感管理加强高校师资队伍建设

随着理性管理与人性管理的有机结合,情感管理成为管理理论时代发展的趋势。在时代高速发展变化的今天,高校管理者应该注重教师的发展变化,强调注重情感管理的方式来促进教师潜能的发挥,从而有效地提升高校管理的质量水平。     

悬垂式电缆硫化管道的数学模型及其设计应用

在管道较长生产的电缆较重时，为了避免绝缘表面易被擦伤，使用悬垂式硫化管道是最好的方法。从电缆连续运动受力的力学分析入手，推导悬垂式硫化管道的数学模型，并给出设计实例。