Purpose: The purpose of this study is to capture students’ essential knowledge and behaviors concerning active living. Methods: Students (N = 1,079) from elementary, middle, and high schools in the United States reported their knowledge of physical activity and fitness (PAF knowledge), and physical activity and sedentary behavior using grade-specific PE Metrics tests and Youth Activity Profile, respectively. Descriptive and inferential statistical analyses were used to address the research purposes. Results: The total PAF knowledge scores and scores in subareas varied by gender and school level. A declining trend for physical activity and an increasing trend for sedentary behavior were observed. PAF knowledge positively predicted physical activity in elementary school boys and middle school girls and negatively predicted sedentary behavior in middle school students and high school boys. Certain PAF knowledge subareas (e.g., elementary school PD#3: knowledge about the characteristics of health-enhancing physical activity; middle school PD#1: knowledge of physical activity participation as part of a healthful lifestyle; high school PD#4: monitoring and adjusting physical activity to meet fitness needs) also significantly predicted behaviors. Conclusion: The findings may guide teachers’ curricular and instructional actions to enhance students’ PAF knowledge through physical education.
Yang Liu and Senlin Chen
Yung-Hui Lee, Chin-Yang Huwang and Yang-Hwei Tsuang
The biomechanical characteristics of 13 snatch lifts performed by 4 elite athletes were analyzed. Electromyographic data, ground reaction force index (GRFI), knee angular velocities, barbell velocities, and lifting time were obtained 0.2 s before the lift, for the first pulling phase (FP), and for the second pulling phase (SP). The preactivation, normalized electromyographic values correlated negatively with GRFI (p < .01). In the FP and SP, all of the parameters correlated positively with each other except lifting time. GRFI in the FP also correlated positively with GRFI, maximum knee angular velocities, and maximum barbell velocities of the SP (p < .01). In the SP, the ground reaction force reached its maximum first, followed by knee angular velocity and then barbell velocity. Barbell velocity reached its maximum before the knee and the hip joint were fully extended. When the correlation of parameters between the consecutive phases of snatch weight lifting was analyzed, it was demonstrated that the preactivation of trunk and leg muscles is important in the activation of the reflectory system in order to fully utilize the forces for generating lifting speed in the pulling phase.
Geoffrey Goldspink and Shi Yu Yang
For some time, it has been appreciated that muscle mass is regulated locally as well as systemically. We have cloned the cDNA of two isoforms of IGF-1, which are derived from the IGF-1 gene by alternate splicing. The expression of one of these was only detectable after mechanical stimulation. For this reason, this has been called mechano growth factor (MGF). The MGF is not glycosylated, is smaller, and has a shorter half-life in the unbound state than the systemic liver type IGF-1. As the result of a reading frame shift the MGF peptide also has a different C terminal sequence and thus has different binding protein/receptor affinities. Another splice variant (muscle L.IGF-I) is expressed in muscle during rest but is also upregulated by exercise. The latter is similar to the systemic liver type IGF-1. The evidence suggests that MGF has a high potency for inducing local protein synthesis and preventing apoptosis and therefore has an important role in local tissue repair and remodeling. Our physiological experiments show that stretch and particularly stretch combined with electrical stimulation, rather than stimulation alone are important in inducing MGF expression. The mechanotransduction mechanism is believed to involve the muscle cytoskeleton. During aging, the production of growth hormone and IGF-1 by the liver declines markedly. The discovery of MGF and muscle IGF-1 provides a link between physical activity and gene expression. This underlines the need for the elderly to remain active as the locally produced growth factors supplement the circulating IGF-1 levels.
Jong Hyun Yang and Young Suk Lee
The purpose of this study was to find the defensive stance and calculate an optimal defense position for goalkeepers while blocking forward jump shots made from a distance of 9 m. Nine men’s handball matches were recorded and 78 video clips were selected for analysis. These are the top class goalkeepers, which included players from the national team and reserve team of Korea. The goalkeeper’s actual defensive position was significantly different from instructional suggestions; the width of both feet of the goalkeeper was approximately 2.5 times the width of the shoulders, and the hands were at waist height. The goalkeeper’s actual defense position was about 1.10 (± 0.3) m from the goal line and also significantly different than instructional material (0.75 m). The optimal defense position, which was calculated from the goalkeeper’s actual movement, was 1.44 m from the goal line, because the ratio of goalkeeper’s defensive area in relation to the total area to be defended is highest at this point. In summary, we recommended that handball goalkeepers move forward, about a half step (0.34 m), when defending a forward jump shot made from 9 m, and instructional material should be modified according to the findings from this study.
Sijie Tan, Chunhua Yang and Jianxiong Wang
The purpose of this study was to apply the lactate threshold concept to develop a more evidence-informed exercise program for obese children. 60 obese children (26 girls and 34 boys, age: 9–10 years, BMI: 25.4 ± 2.2kg/m2) were recruited and half of them were randomly selected to be trained for eight weeks with a controlled exercise intensity at lactate threshold. The trained children achieved significant improvements on their body composition and functional capacity compared with the control group. The findings suggested that the training program with intensity at lactate threshold is effective and safe for 9–10 year old children with obesity.
Senlin Chen, Yang Liu and Jodee Schaben
The purpose of this study was to examine physical activity (PA)/fitness knowledge and its association with PA and sedentary behavior in youth.
Eighth grade students from five schools (N = 660) in a midwestern state completed a PE Metrics written test and the Youth Activity Profile to assess PA/fitness knowledge, PA (at school and after school) and sedentary behavior, respectively.
Participants were clustered into high, medium, and low knowledge groups. Students in the high knowledge group reported higher level of PA after school (p < .05, d = .28) but lower level of sedentary behavior than the low knowledge group (p = .001, d = -.45). The low knowledge group also reported higher PA at school (p < .05, d = .25). PA/Fitness knowledge significantly predicted sedentary behavior, particularly in the low knowledge group (β = -.32, t = -2.46, p < .05, R 2 = .105), after controlling for gender and race/ethnicity.
Physical education focused on conveying PA/fitness knowledge is warranted to educate youth to move more and sit less.
Donald C. Leigh and Wei-Yang Lu
The dynamical interactions in tennis between ball, strings, and racket, during ball impact and immediately after, are modeled by a system of nonlinear ordinary differential equations that include both damping and elastic properties. During impact, the time history of the deflections, velocities, and forces in all parts of the system were calculated. Some simple experiments were done to determine the elastic and damping properties of the ball and strings, and to verify the theory in the case of a ball rebounding from the strings of a clamped racket head. Among the findings is that there is a trampoline effect even for a clamped racket head. Most interesting is that the rebound velocity of the ball can be increased, the mechanical energy transmitted to the racket can be reduced, and the maximum force transmitted to the holder of the racket can be reduced, all by increasing the damping in the racket.
Yang Liu, Senlin Chen and Xiangli Gu
Purpose: The study purpose was to examine performance differences in physical education among learners from two middle schools from two different states. Methods: Performance in physical education was represented by attitude toward physical education, knowledge of physical activity and fitness, and active living behaviors (i.e., physical activity and sedentary behavior). The sixth, seventh, and eighth graders of a midwestern state school (n = 397) and a deep southern state school (n = 350) completed the surveys (N = 747). Results: The authors observed statistically significant school differences in physical activity and fitness knowledge and physical activity behavior (favoring the deep southern state school), and in attitude and sedentary behavior (favoring the midwestern state school). The authors also found stronger associations between attitude and physical activity (but weaker associations between attitude and sedentary behavior) among the deep southern state school students than the midwestern state school students. Conclusion: These observed performance differences and their pedagogical ramifications are discussed in relation to sociodemographic and environmental factors.
Chih-Hsiang Yang and David E. Conroy
Mindful walking has emerged as a potential intervention strategy to improve mental health and promote well-being in adult and clinical populations. This strategy has not been implemented specifically with older adults to date. This study evaluated the feasibility, acceptability, sustainability, and preliminary efficacy of a mindful walking program for reducing negative affect in older adults. Community-dwelling older adults (n = 29) completed a 1-month, outdoor mindful walking program distributed across eight 30-min sessions. Responses from postprogram and follow-up questionnaires revealed that mindful walking was well-accepted, highly valued, and maintained after the program ended. Analysis from the pre- and postwalk surveys also suggested the preliminary efficacy of a mindful walking program for reducing negative affect. Positive results identified in the current feasibility study indicate readiness for randomized controlled trials to further examine the efficacy and effectiveness of a mindful walking intervention for promoting health and well-being in older populations.
Jin-Jin Yang and David L. Porretta
Based on Singer’s (1986) method, we investigated the effects of a four-step strategy (ready, look, do, score) on training, maintenance, and generalization of three closed skills (basketball free throw, overhand softball throw, and dart throw) by adolescents (M age = 17.2) with mild mental retardation (MR). A multiple baseline across skills design was used. Performances of 3 males and 3 females across these three skills were examined. Participants averaged a total of 46 sessions for the duration of the study. Results indicated that participants increased performance 18–56% across all three closed skills during the training phase. A total of 4 participants maintained performance on all three skills when reminders were present, and 2 decreased performance when the reminders were removed. All participants exhibited improved performance when a reinforcer was introduced. Moreover, 5 participants were able to generalize the four-step strategy to a different setting.