Validity and reliability of a linear positional transducer across commonly practised resistance training exercises     

Harry F. Dorrell  Joseph M. Moore  Mark F. Smith  Thomas I. Gee 《Journal of sports sciences》2019,37(1):67-73

This study investigated the validity and reliability of the GymAware PowerTool (GPT). Thirteen resistance trained participants completed three visits, consisting of three repetitions of free-weight back squat, bench press, deadlift (80% one repetition maximum), and countermovement jump. Bar displacement, peak and mean velocity, peak and mean force, and jump height were calculated using the GPT, a three-dimensional motion capture system (Motion Analysis Corporation; 150 Hz), and a force plate (Kistler; 1500 Hz). Least products regression were used to compare agreeability between devices. A within-trial one-way ANOVA, typical error (TE; %), and smallest worthwhile change (SWC) were used to assess reliability. Regression analysis resulted in R² values of >0.85 for all variables excluding deadlift mean velocity (R² = 0.54–0.69). Significant differences were observed between visits 3-2 for bench press bar displacement (0.395 ± 0.055 m; 0.383 ± 0.053 m), and deadlift bar displacement (0.557 ± 0.034 m; 0.568 ± 0.034 m). No other significant differences were found. Low to moderate TE (0.6–8.8%) were found for all variables, with SWC ranging 1.7–7.4%. The data provides evidence that the GPT can be used to measure kinetic and kinematic outputs, however, care should be taken when monitoring deadlift performance.  相似文献   

Problematic Nature of School Purposes: Implications for pre‐service teacher training programmes     

Harry M. Teitelbaum 《Journal of educational administration and history》1997,29(2):142-157

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Perception of kinematic characteristics of tennis strokes for anticipating stroke type and direction     

Shim J  Les Carlton G  Kwon YH 《Research quarterly for exercise and sport》2006,77(3):326-339

The purpose of this study was to determine the sources of visual information used by highly skilled tennis players in anticipating their opponent's shots. In Experiment 1, motion analysis of the strokes showed that the relative motion between the racquet and forearm was different between the ground strokes and lobs, but there were no reliable kinematic differences when shot direction was varied. In Experiment 2, 12 skilled tennis players observed the opponent hitting strokes in a normal video or in a point-light display with different segments occluded. Players' anticipation accuracy was not degraded by the use of the point-light display. Occluding the racquet and forearm significantly reduced the participant's ability to determine the type of stroke produced.  相似文献   

On the racism industry     

Harry V. Jaffa 《Academic Questions》1996,9(4):83-85

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Effects of light refraction on the accuracy of camera calibration and reconstruction in underwater motion analysis   总被引：1，自引：0，他引：1  

Kwon YH  Casebolt JB 《Sports biomechanics / International Society of Biomechanics in Sports》2006,5(2):315-340

One of the most serious obstacles to accurate quantification of the underwater motion of a swimmer's body is image deformation caused by refraction. Refraction occurs at the water-air interface plane (glass) owing to the density difference. Camera calibration-reconstruction algorithms commonly used in aquatic research do not have the capability to correct this refraction-induced nonlinear image deformation and produce large reconstruction errors. The aim of this paper is to provide a thorough review of: the nature of the refraction-induced image deformation and its behaviour in underwater object-space plane reconstruction; the intrinsic shortcomings of the Direct Linear Transformation (DLT) method in underwater motion analysis; experimental conditions that interact with refraction; and alternative algorithms and strategies that can be used to improve the calibration-reconstruction accuracy. Although it is impossible to remove the refraction error completely in conventional camera calibration-reconstruction methods, it is possible to improve the accuracy to some extent by manipulating experimental conditions or calibration frame characteristics. Alternative algorithms, such as the localized DLT and the double-plane method are also available for error reduction. The ultimate solution for the refraction problem is to develop underwater camera calibration and reconstruction algorithms that have the capability to correct refraction.  相似文献   

Some economic aspects of science     

Harry G. Johnson 《Minerva》1972,10(1):10-18

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U Crazy     

Harry Stein 《Academic Questions》2011,24(4):489-493

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Predicaments,Problems, Puzzles,and Paradoxes in Educational Research*     

Harry S. Broudy 《Educational theory》1983,33(1):33-39

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Problems Associated with Multi-Media Data Bases     

Philip G Barker  Harry Yeates 《British journal of educational technology : journal of the Council for Educational Technology》1981,12(2):158-175

Education is intimately associated with communication, and so may utilize any technology that is able to support a process that enables information to be transferred from one location to another. This paper describes the meaning of the term multi-media data base and presents a model of its potential role in aiding message creation for the purposes of communicating educational material using many parallel channels. Some of the problems associated with the implementation of such systems are outlined.  相似文献   

Social IEP Objectives, Teacher Talk, and Peer Interaction in Inclusive and Segregated Preschool Settings     

Kyong-Ah Kwon  James Elicker  Susan Kontos 《Early Childhood Education Journal》2011,39(4):267-277

The purpose of this study was to examine: (a) the role of teacher talk in promoting peer interaction, (b) the adequacy of social IEP objectives to reflect children’s social functioning and guide provision of teacher talk, and (c) differences in children’s peer interaction and teacher talk in inclusive and segregated settings. Thirty children with disabilities and their teachers participated. Overall, we observed low rates of teacher talk thought to support peer interaction; however, when teachers verbally facilitated peer interaction, children were observed interacting more frequently with peers. Children’s social IEPs accurately reflected their current level of social functioning. However, the social IEPs appeared to fail to influence teacher intervention. Finally, children with disabilities in inclusive settings interacted with peers more than children in segregated settings, even though there was no significant difference in amount of teacher talk in the two settings.  相似文献