Sex and Athletic Status as Factors in Reaction Latency and Movement Time

Abstract

This study investigated the effects of sex and athletic status on reaction latencies and movement time. One hundred subjects, categorized into five groups of 20 subjects each—male athletes (MA), female athletes (FA), male nonathletes (MNA), female nonathletes (FNA), and control group (CG)—were tested over a period of five consecutive days. Several different types of incentives were used to ensure that subjects provided the fastest times possible. Two blocks of 25 trials were administered to each subject on each day. A 2 × 2 × 2 × 5 × 2 mixed factorial analysis of variance was used to test for between-subject differences of group (experimental/control), sex, and athletic status and for within-subject differences of days and blocks. The four dependent variables were reaction time (RT) mean, RT consistency, movement time (MT) mean, and MT consistency. Results did not support the classic finding of male superiority over females in RT/MT or athletes' superiority over nonathletes. Evidence of athletic superiority emerged, but for the first day of practice only. As subjects were allowed extended practice over a 5-day test period in which knowledge of results (KR) and other incentives were provided, differences in the experimental groups disappeared. Sex was the predominant factor in consistency, with males being less variable in RT (p = .02) performance than females. There were no sex differences in MT consistency.     

Fractionated Reaction Time Responses to Auditory and Electrocutaneous Stimuli

Abstract

It is well documented that simple reaction time (RT) varies inversely with stimulus intensity, but there is disagreement as to which stimulus modality produces the fastest simple RT. An investigation was conducted to equate two stimulus modalities, auditory (A) and electrocutaneous (EC), using varying stimulus intensities in a simple RT protocol. A second investigation was then conducted to examine neuromotor characteristics of stimulus-evoked responses using previously equated A and EC stimuli of varying intensity from the first investigation. Results showed that RT, premotor time (PMT), and motor time (MT) were all inversely related to stimulus intensity, while maximum displacement (MAXD) was directly related to stimulus intensity, and movement time was not affected by stimulus intensity. We conclude that: (a) both central and peripheral components of RT are altered by varying stimulus intensities, and (b) rapid movements are enhanced by increasing stimulus intensity.     

Mechanics of Batting: Effect of Stride Technique on Ground Reaction Forces and Bat Velocities

The benefits associated with being physically active are well documented, but a significant proportion of the population is insufficiently active. Physical inactivity is a major health risk factor in our society, and physical education programs are consistently identified as a means to address this concern. The purpose of this article is to use the social-ecological model as a framework to examine ways in which physical education programs can play an important role in promoting physical activity. Policies that require time allocations and resources for physical education and physical activity in schools and community designs that provide infrastructure that makes being physically active accessible and convenient are important factors in making schools and communities healthier spaces. It is clear, however, that policies alone are not sufficient to address concerns about physical inactivity. We must consider individual factors that influence decisions to be physically active in efforts to engage children in physical education programs that promote active lifestyles. The learning climate that teachers create determines what students do and learn in physical education classes. Ensuring that students see value in the content presented and structuring classes so that students believe they can experience success when they exert effort are key elements in an effective motivational climate. Efforts to address public health concerns about physical inactivity require a comprehensive approach including quality physical education. It is critical that kinesiology professionals emerge as leaders in these efforts to place physical education programs at the center of promoting children's physical activity.     

The Kinematics and Kinetics of the Running Pattern of Two-, Four-, and Six-Year-Old Children

Abstract

Selected kinematic and kinetic variables in the running pattern of 2-, 4-, and 6-year-old children were investigated. Cinematographic records and force-plate tracings were used to study the running patterns of the 28 Caucasian subjects, 15 male and 13 female. A 2 × 3 (sex × age) factorial analysis of variance was used to determine whether effects of variation between and within age and sex factors for each of the dependent variables of selected kinematic (displacement and velocity) and kinetic (ground reaction force) variables were significant. The running speeds improved with age. Although height and weight gains influenced the improvement shown in performance, certain biomechanical variables also contributed to the development of the running pattern. In the majority of the selected kinematic and kinetic variables there were significant differences between the 2-year-old group and the other two groups. Where there were significant differences in the variables, the differences tended to be in displacement, velocity, and magnitude of force measures, rather than in time of occurrence measures. Significant differences between male and female subjects appeared in five kinematic variables related to the swing leg.     

中国羽毛球队让球事件的连锁反应——竞技体育参与者利益分化的突显

伦敦奥运会中国、韩国、印尼羽毛球运动员因消极比赛被国际羽联取消本届奥运会参赛资格,韩国对消极比赛的运动员、教练员给予重罚,而国羽＂让球主角＂被奖、庆功宴对＂让球事件＂闭口不提。同样的消极比赛不同的处理方式显示两国历史文化及国情的差异。羽毛球队让球事件的连锁反应是竞技体育参与者利益分化的凸显,因此建立竞技体育利益制衡机制,是实现竞技体育利益平衡的关键。     

Hammer acceleration due to thrower and hammer movement patterns

Ground reaction force and wire tensile force were measured during test throws by three hammer throwers: the Asian record holder, who had a personal best of 83.47 m at the time of the investigation, and two university athletes, with personal bests of 59.95 m and 46.30 m respectively. They were filmed using three high-speed video cameras (250 Hz). The displacements of the hammer head and the athletes' centres of mass were calculated using three-dimensional analysis procedures. The Asian record holder's centre of mass and the hammer head on the final two turns exhibited approximate conjunctions of the hammer high point and the thrower's low point and vice versa about the hammer's azimuth angle. It is conjectured that the reason why the thrower's movement is asynchronous with the hammer's movement by approximately half a turn is to accelerate the hammer head in a manner similar to the way that the amplitude of a pendulum increases when it is pulled upward by a string against the downward movement of the swinging weight.     

浅谈氧化还原反应方程式的配平

介绍用化合价升降法配平无机、有机氧化还原反应方程式。     

隆裕太后逝世的社会反应述略

隆裕太后于1913年2月22日突然逝世,从而引起了强烈的社会反响,舆论主要集中在其逝世的原因、清宫内廷主持的确立、丧事筹备等方面,由此折射出新旧体制鼎革时期人们对隆裕太后逝世反应的复杂社会面相。本文的目的就在于通过对这种复杂社会面相的分析和探究,来揭示在历史事件中的各种复杂的社会现象,以此给我们提供深刻的历史借鉴意义。     

EtAlCl2和Et2AlCl催化的有机加成反应的研究进展

按有机反应的官能团,对EtAlCl2和Et2AlCl催化的有机加成反应的研究进展进行了综述。EtAlCl2和Et2AlCl催化的有机加成反应包括链式加成反应和环加成反应。EtAlCl2和Et2AlCl中的Al3 具有p电子空轨道,Al3 与反应物中某些不饱和键络合,如C=O、C=C、C=N等,也能与催化体系中的某些配体络合,产生协同催化作用。EtAlCl2和Et2AlCl是促进有机加成反应的良好试剂,反应不仅具有较高的产率,而且具有很好的立体选择性。     

F^-在有机合成反应中的应用

综述了氟离子作为电子供给体和非亲核性的催化剂在烷基化反应、羟醛缩合反应、Michael加成、Knoevenagel缩合反应、Wittig反应和Wittig-Horner反应、重氮化反应等有机反应中应用，并对其催化机理进行了探讨。