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We examined the supposition that swimmers may exhibit an imbalance in bilateral arm power output during simulated swimming exercise. Ten competitive front crawl swimmers (5 males, 5 females; age 20.5+/-2.3 years; height 1.74+/-0.09 m; body mass 72.0+/-16.7 kg; 400 m freestyle swim time 278+/-20.5 s; mean +/- s) performed four incremental (10 W x min(-1)) swim ramp tests on a computer-interfaced biokinetic swim bench ergometer. External power output from each arm was measured continuously to exhaustion. The results showed that, throughout the course of the simulated swim, external power output clearly favoured the left arm (F1,9 = 12.5, P= 0.006). This was especially evident in the final 30 s to exhaustion, when 54.0+/-3.87% of external power output was derived from the left arm versus 46.0+/-3.87% from the right arm. The disparity in external power output was further highlighted when the participants were grouped into unilateral and bilateral breathers. Unilateral breathers (n = 5) produced 57.1+/-2.62% of external power output from the left armversus 42.9+/-2.62% from the right arm (P= 0.001). Bilateral breathers (n = 5) exhibited a more balanced external power output of 51.0+/-1.82% from the left arm and 49.0+/-1.82% from the right arm (P = 0.177). Evidence of power imbalance in the simulated swimming stroke may have important implications for optimizing swim performance. The observed power imbalance may be reduced when a bilateral breathing technique is adopted. 相似文献
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This sub‐study is part of a longitudinal naturalistic investigation monitoring the social behaviour of young children (3‐8‐year‐olds) before and after the arrival of broadcast television in St Helena, South Atlantic. Children's free‐play behaviour in first school playgrounds was videotaped in 1994 (pre‐tv), and in 1995 and 1996 (post‐tv), and then coded and analysed by trained observers. Findings showed no significant differences in children's behaviour either across the availability of broadcast television (i.e. CNN) or with the addition of further channels (CNN plus others). 相似文献
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The temporal discounting literature has demonstrated that the loss in value for delayed outcomes is most accurately modeled using a hyperbolic discounting equation. The hyperbolic-shaped function not only describes the shape of discounting for monetary outcomes, but also for other tangibles, such as alcohol, candy, CDs, erotica, cigarettes, cocaine, books, and DVDs. Furthermore, this hyperbolic shape has important theoretical implications. Despite the broad list of outcomes that are hyperbolically discounted, one class of outcomes has only recently received attention: social interactions. For the present study, we used standard binary-choice discounting procedures to explore the function that most accurately describes the change in value of delayed social interactions. The results from the present study suggest that, for 93 participants, the same equations (exponential, hyperbolic, and hyperboloid) used to describe the discounting of nonsocial commodities also describe the relation between delay and the value of social interaction. Similar to previous findings for nonsocial outcomes, the hyperbolic-shaped models provide a fit to the data superior to that of the exponential model. 相似文献
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Restructured extracurricular activities are a component in many of the proposed solutions for the educational problems of
minority students in urban schools. This study investigates the relationships between participation in traditional extracurricular
activities and the academic achievement levels of minority male and female students in poor urban schools. Using a national
data base, we found that, in almost 50 percent of the cases, male student participation in extracurricular activities was
associated with lower achievement levels. For female students, the results were mixed. In 23 of the 90 different analyses
run, females who participated in extracurricular activities were found to have higher achievement levels than nonparticipating
females. In 6 cases, female participants had lower achievement levels. In the remaining cases, no differences were found.
Reasons for and implications of the results are examined. 相似文献
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Benjamin F. Mentiplay Ksaniel Hasanki Luke G. Perraton Yong-Hao Pua Paula C. Charlton Ross A. Clark 《Journal of sports sciences》2018,36(19):2202-2209
The Microsoft Xbox One Kinect? (Kinect V2) contains a depth camera that can be used to manually identify anatomical landmark positions in three-dimensions independent of the standard skeletal tracking, and therefore has potential for low-cost, time-efficient three-dimensional movement analysis (3DMA). This study examined inter-session reliability and concurrent validity of the Kinect V2 for the assessment of coronal and sagittal plane kinematics for the trunk, hip and knee during single leg squats (SLS) and drop vertical jumps (DVJ). Thirty young, healthy participants (age = 23 ± 5yrs, male/female = 15/15) performed a SLS and DVJ protocol that was recorded concurrently by the Kinect V2 and 3DMA during two sessions, one week apart. The Kinect V2 demonstrated good to excellent reliability for all SLS and DVJ variables (ICC ≥ 0.73). Concurrent validity ranged from poor to excellent (ICC = 0.02 to 0.98) during the SLS task, although trunk, hip and knee flexion and two-dimensional measures of knee abduction and frontal plane projection angle all demonstrated good to excellent validity (ICC ≥ 0.80). Concurrent validity for the DVJ task was typically worse, with only two variables exceeding ICC = 0.75 (trunk and hip flexion). These findings indicate that the Kinect V2 may have potential for large-scale screening for ACL injury risk, however future prospective research is required. 相似文献