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The aims of this study were to compare the aerobic energy cost of four 'on-snow' skating techniques in cross-country skiing and to examine the relationships between performance and aerobic energy cost. Twelve male skiers from recreational to national standard performed four level skating trials of 6 min duration in random order, each at the same submaximal velocity but with a different skating technique: (1) 'offset' (V1), using a double asymmetrical and asynchronous pole plant as weight is transferred to one ski; (2) 'two-skate' (V2A), where the pole plant is symmetrical; (3) 'one-skate' (V2), where there is a pole plant as weight is transferred to each ski; and (4) 'conventional', without poles. Oxygen uptake (VO2), pulmonary ventilation, the respiratory exchange ratio and heart rate were measured using a K4(b2) portable gas analyser. The aerobic energy cost (VO2/mean speed) and heart rate were higher (P < 0.05) in the one-skate than in the offset condition. This may be explained by the greater and more efficient use of the upper body and the lower variation in centre of gravity velocity in the offset condition. The aerobic energy cost was 5-9% higher (P < 0.01) in the conventional than in the other techniques, probably because of the shorter duration of propulsive forces within a cycle in the conventional skating condition. Moreover, in ski skating, the mechanical efficiency (propulsive forces/total forces) was shown to be higher in the upper than in the lower limbs. The correlation coefficient between performance and aerobic energy cost was significant in the two-skate (r = 0.68, P = 0.02), one-skate (r = 0.72, P = 0.01) and conventional (r = 0.62, P = 0.04) conditions, but not in the offset condition (r = 0.50, P = 0.10). Our results stress the importance of the upper body component in cross-country skiing and that the aerobic energy cost discriminates between skiers of different standards.  相似文献   
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Alien Resurrection (1997) heightens the movements across dark humor and horror, and enables more pronounced and complex conjunctions across the three types of shadows put forward by Rushing/Frentz and Picart, particularly in the case of the monstrous female characters like Ripley and Call. These characters bisociate the realms of first shadow (female bodies), second shadow (products of technology), and third shadow (fearsome female freedom fighters). Nevertheless, both live—a rarity among Frankensteinian cinemyths. Alien Resurrection enables us to glimpse, through a glass darkly, other ways in which the gendered and raced complexities of the Frankenstein cinematic myth may be traced.  相似文献   
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This paper will explore some issues raised by an evaluation of a Scottish video making project which works with young people in trouble or 'at risk' in school. In the paper we reflect on the problems of evaluating work with troubled and troublesome pupils and on the difficulties of both collecting and presenting appropriate evidence. It offers a contribution to continuing debates over educational exclusion and inclusion and to the research literature on strategies for supporting young people in school. The paper also raises key questions about the planning and evaluating of support services for young people by schools.  相似文献   
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