Kinematics and kinetics of youth baseball pitching with standard and lightweight balls

Because youth athletes are smaller and weaker than their adult counterparts, smaller equipment and fields are often used in youth sports. Previous research has shown that youth baseball pitchers use similar motions to older pitchers, but generate lower kinetics and angular velocities at the shoulder and elbow. The purpose of this study was to determine potential biomechanical benefits for youth pitchers to use lighter baseballs. Thirty-four youth (11.1 ± 0.7 years) pitchers pitched both standard [5 ounce (142 g)] and lightweight [4 ounce(113 g)] baseballs in a laboratory setting. Kinematic and kinetic parameters were measured with a six-camera high-speed motion analysis system. Three repeated measures MANOVAs were used to compare (p > 0.05) position, velocity, and kinetic parameters between the standard and lightweight baseballs. Subjective data were also collected. Pitching the lightweight ball produced no difference in arm position, but greater shoulder, elbow, and ball velocities. With the lightweight ball, pitchers produced decreased kinetics.Post-hoc analysis of the kinetic data revealed significant decreases in elbow varus torque and shoulder internal rotation torque. The data suggest that playing with lightweight baseballs may reduce the risk of overuse injury in the youth pitcher and also help develop arm speed. However, before introducing lightweight baseballs into the youth game, the effect of lighter, faster pitched balls for the batters and fielders should also be considered.     

再问“钱学森之问”——浅思中国教育改革之路

我国著名科学家钱学森在国家总理温家宝看望之际,提出了著名的"钱学森之问",这再次将我国教育改革和发展问题推向了风口浪尖。据笔者掌握的资料来看,绝大部分舆论和学者一边倒地支持钱老的质问,而向中国现行教育制度发难。为什么会出现这样状况?主要是因为大多数民众忽视了我国教育改革和发展所取得的成绩,对我国教育改革和发展期待过于迫切,对大师的崇拜、从众和极化等,这又可能导致领导决策者的误判和错误决策,而将中国教育引向错误道路。从"钱学森之问"出发,我们有必要进一步追问:什么是大师?大师就等于现代教育的成功?我国教育的主要问题在哪里?我国教育的改革出路又在哪里?     

Woollard,John (2011) Psychology for the classroom: E‐learning Routledge (New York & London) isbn 978‐0‐415‐59093‐8 135 pp £19.99http://www.routledge.com/books/details/9780415590938/

With its thorough review of the uses of relevant techniques in education, this provides useful information for educators. It covers research, theory, pedagogy, and strategies for using e‐learning. If the content of this book is likely to be relevant to you, we recommend you borrow a copy for a while. Melissa Hoffmann & William Brescia     

Attentional Bias for Exercise-Related Images

Abstract

This research examined attentional bias toward exercise-related images using a visual probe task. It was hypothesized that more-active participants would display attentional bias toward the exercise-related images. The results showed that men displayed attentional bias for the exercise images. There was a significant interaction of activity level by gender, and simple slopes analysis showed that active women displayed attentional bias toward the exercise-related images and inactive women displayed attentional bias toward the control images. A similar analysis with explicit attention to the pictures as the outcome variable was not significant. These findings confirm that attention for exercise-related images can be captured automatically regardless of whether people report they are attending to them.     

Children's Activity Levels and Lesson Context during Third-Grade Physical Education

Abstract

Little is known about children's activity levels during physical education classes and how they relate to the national health objectives for the year 2000 (U.S. Public Health Service, 1991). We systematically observed students' physical activity and associated variables in 293 third-grade physical education lessons in 95 schools in 4 Child and Adolescent Trial for Cardio-vascular Health (CATCH) centers in California, Louisiana, Minnesota, and Texas. The influence of independent variables was assessed simultaneously by analysis of variance. Significant differences among study centers were evidenced for both physical activity and lesson context variables. Additionally, there were differences among variables for lesson location and teacher specialty, but not for teacher gender. Boys were more active than girls, but only during free play opportunities. The findings have widespread implications for educators responsible for developing and implementing health-related physical education programs, as well as for designing and conducting staff development.     

Expert-Novice Differences in Cognitive and Skill Execution Components of Youth Baseball Performance

Abstract

Previous research has shown that experts exhibit superior response selection and skill execution during performance in youth sport. The purpose of this study was to examine differences in cognitive and skill execution components of game performance in young baseball players (N = 159) with, varying levels of expertise. Three levels of expertise (low-, average-, and high-skilled players) were identified at each age level (7, 8, 9, and 10 years of age). Game performance was videotaped, and measures of skill execution (throwing accuracy, throwing force, fielding, catching, batting average, and batting contact) and cognitive components (positioning, decisions) were developed from observational analysis. The results indicated that baseball skill execution during game play maximally discriminated expertise levels.