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Ruth Osgood Denning 《Clearing house (Menasha, Wis.)》2013,86(2):100-103
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Seeley MK Funk MD Denning WM Hager RL Hopkins JT 《Sports biomechanics / International Society of Biomechanics in Sports》2011,10(4):415-426
Peak joint angles and joint angular velocities were evaluated for varying speed forehands in an attempt to better understand what kinematic variables are most closely related to increases in post-impact ball velocity above 50% of maximal effort. High-speed video was used to measure three-dimensional motion for 12 highly skilled tennis players who performed forehands at three different post-impact ball speeds: fast (42.7 +/- 3.8 m/s), medium (32.1 +/- 2.9 m/s), and slow (21.4 +/- 2.0 m/s). Several dominant-side peak joint angles (prior to ball impact) increased as post-impact ball speed increased from slow to fast: wrist extension (16%), trunk rotation (28%), hip flexion (38%), knee flexion (27%), and dorsiflexion (5%). Between the aforementioned peak joint angles and ball impact, dominant-side peak angular velocities increased as ball speed increased from slow to fast: peak wrist flexion (118%), elbow flexion (176%), trunk rotation (99%), hip extension (143%), knee extension (56%), and plantarflexion (87%). Most kinematic variables changed as forehand ball speed changed; however, some variables changed more than others, indicating that range of motion and angular velocity for some joints may be more closely related to post-impact ball speed than for other joints. 相似文献
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This article describes a project to apply and validate a conceptual framework of clusters of purposeful learning activity involving ICT tools. The framework, which is based in a socio-cultural perspective, is described as ‘DECK’, and comprises the following major categories of the use of digital technologies to support learning: distributed thinking and knowing; engagement; community and communication; and knowledge building. Small-scale research to test the framework was carried out with 12 teachers in English primary and secondary schools. The methods involved mind mapping, ‘think aloud’ procedures and interviews. The framework was modified in the light of teachers' responses and offers a way of describing and thinking about the diverse uses of digital technologies to support learning in various contexts. 相似文献