Relationship between the peak time of hamstring stretch and activation during sprinting

The purpose of this study was to investigate the time series relationships between the peak musculotendon length and electromyography (EMG) activation during overground sprinting to clarify the risk of muscle strain injury incidence in each hamstring muscle. Full-body kinematics and EMG of the right biceps femoris long head (BFlh) and semitendinosus (ST) muscles were recorded in 13 male sprinters during overground sprinting at maximum effort. The hamstring musculotendon lengths during sprinting were computed using a three-dimensional musculoskeletal model. The time of the peak musculotendon length, in terms of the percentage of the running gait cycle, was measured and compared with that of the peak EMG activity. The maximum length of the hamstring muscles was noted during the late swing phase of sprinting. The peak musculotendon length was synchronous with the peak EMG activation in the BFlh muscle, while the time of peak musculotendon length in the ST muscle occurred significantly later than the peak level of EMG activation (p < 0.05). These results suggest that the BFlh muscle is exposed to an instantaneous high tensile force during the late swing phase of sprinting, indicating a higher risk for muscle strain injury.     

What Is Right About Special Education

Abstract

Promoting self-determination has become an important aspect of the educational programs of students with disabilities. There is now a sufficient literature base to support some syntheses that enable researchers to judge their progress in this area to date and to provide direction for future research and practice. For this study, we conducted a literature review of studies that measured or examined global self-determination.     

Measurement of total energy expenditure by the doubly labelled water method in professional soccer players

To determine the daily energy requirements of professional soccer players during a competitive season, we measured total energy expenditure in seven players (age 22.1+/-1.9 years, height 1.75+/-0.05 m, mass 69.8+/-4.7 kg; mean +/- s) using the doubly labelled water method. Energy intake was simultaneously estimated from 7 day self-report dietary records. Mean total energy expenditure and energy intake were 14.8+/-1.7 MJ x day(-1) (3532+/-408 kcal x day(-1)) and 13.0+/-2.4 MJ x day(-1) (3113+/-581 kcal x day(-1)), respectively. Although there was a significant difference between total energy expenditure and energy intake (P < 0.01), there was a strong relationship between the two (r= 0.893, P< 0.01). Basal metabolic rate and recommended energy allowance calculated from the Recommended Dietary Allowances for the Japanese were 7.0+/-0.3 MJ x day(-1) (1683+/-81 kcal x day(-1)) and 15.6+/-0.8 MJ x day(-1) (3739+/-180 kcal x day(-1)), respectively. A physical activity level (total energy expenditure/ basal metabolic rate) of 2.11+/-0.30 indicated that, during the competitive season, professional soccer players undertake much routine physical activity, similar to that of competitive athletes during moderate training. Energy intake estimated using dietary records was under-reported, suggesting that its calculation from these data does not predict energy expenditure in soccer players.     

War3录像点评

防御不如进攻!这是我们SupT和V.var战队打的友谊赛,比较正规一点的比赛,打的时间比较长,算是一场我的翻盘吧,这盘录像大概是我两年前打的,为数不多的比较精彩的一盘,希望玉米哥能抽空点评一下。APM:=SupT=mSc_Zack:126.03V.vAr]DaRE:115.71     

A multivariate examination of parent involvement and the social and academic competencies of urban kindergarten children

The primary objective of this study was to obtain a multidimensional picture of parent involvement in kindergarten. Participants in this study were 307 low‐income, ethnic minority children and their primary caregivers in a large, urban school district in the Northeast. Results revealed that kindergarten parent involvement dimensions (i.e., from the Parent Involvement in Children's Education Scale; Fantuzzo, Tighe, McWayne, Davis, & Childs, 2002) were congruent with those established with preschool (Head Start) parents. Multivariate relationships were found between kindergarten parent involvement dimensions and children's social and academic competencies. Parents who actively promote learning in the home, have direct and regular contact with school, and experience fewer barriers to involvement have children who demonstrate positive engagement with their peers, adults, and learning. © 2004 Wiley Periodicals, Inc. Psychol Schs 41: 363–377, 2004.     

Differences in hamstring activation characteristics between the acceleration and maximum-speed phases of sprinting

This study aimed to investigate activation characteristics of the biceps femoris long head (BFlh) and semitendinosus (ST) muscles during the acceleration and maximum-speed phases of sprinting. Lower-extremity kinematics and electromyographic (EMG) activities of the BFlh and ST muscles were examined during the acceleration sprint and maximum-speed sprint in 13 male sprinters during an overground sprinting. Differences in hamstring activation during each divided phases and in the hip and knee joint angles and torques at each time point of the sprinting gait cycle were determined between two sprints. During the early stance of the acceleration sprint, the hip extension torque was significantly greater than during the maximum-speed sprint, and the relative EMG activation of the BFlh muscle was significantly higher than that of the ST muscle. During the late stance and terminal mid-swing of maximum-speed sprint, the knee was more extended and a higher knee flexion moment was observed compared to the acceleration sprint, and the ST muscle showed higher activation than that of the BFlh. These results indicate that the functional demands of the medial and lateral hamstring muscles differ between two different sprint performances.     

The Diffusion of Mobile Internet in Japan

In Japan, the mobile phone has become an increasingly popular medium of accessing the Internet and e-mail, especially among those who may not have affordable access to a computer. The lower startup costs and the easier overall accessibility of mobile phones relative to personal computers suggest that the mobile phone may be a possible alternative for overcoming unequal access to information communication technology in Japan and elsewhere. Using microdata from 2001, we compare and contrast the determinants of mobile versus computer-based Internet in Japan. Our findings show that mobile Internet access, as compared to computer access, is determined less by demographics, socioeconomic status, and technological readiness, suggesting that barriers to Internet access are lower for mobile phones than is the case for computers.     

Recognition of Moving and Static Faces by Young Infants

This study compared 3- to 4-month-olds' recognition of previously unfamiliar faces learned in a moving or a static condition. Infants in the moving condition showed successful recognition with only 30 s familiarization, even when different images of a face were used in the familiarization and test phase (Experiment 1). In contrast, infants in the static condition showed successful recognition only when the familiarization duration was lengthened to 90 s and when the same image was used between the familiarization and test phase (Experiments 2 and 3). Furthermore, presentation of multiple static images of a face did not yield the same level of performance as the moving condition (Experiment 4). These results suggest that facial motion promotes young infants' recognition of unfamiliar faces.