Energy cost of different skating techniques in cross-country skiing     

Millet GP  Boissiere D  Candau R 《Journal of sports sciences》2003,21(1):3-11

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   

Imagery use in elite youth sport participants: reinforcing the applied significance of achievement goal theory     

Harwood C  Cumming J  Hall C 《Research quarterly for exercise and sport》2003,74(3):292-300

This study examined the motivational profiles of elite youth athletes to determine whether individual differences in goal orientation corresponded with differential levels of imagery use. Two hundred ninety male (n = 88) and female (n = 202) young athletes (M = 16.6 years, SD = 1.48) completed the Perceptions of Success Questionnaire (POSQ, Roberts, Treasure, & Balague, 1998) to assess dispositional goal orientations and the Sport Imagery Questionnaire (Hall, Mack, Paivio, & Hausenblas, 1998) to assess frequency and function of imagery use. A two-stage cluster analysis on the POSQ scores revealed a three-cluster solution with a multivariate analysis of variance indicating significant differences among cluster groups in imagery use. Athletes in Cluster 3 (higher task/higher ego) used significantly more imagery, regardless of the function than athletes in Cluster 1 (lower task/moderate ego) or Cluster 2 (moderate task/lower ego). These findings are discussed with reference to the role of achievement motivation in influencing young athletes' behavioral investments in mental strategies.  相似文献   

"Ask A Librarian": the experiences of four hospital libraries     

Stone ME  Foxman C  Sostack M  Francar L  Hall P  Markwell LG 《Medical reference services quarterly》2003,22(2):93-105

The librarians at four hospital libraries describe the electronic reference service, "Ask A Librarian," offered at their institutions. The hospitals are vastly different in size and in number of library staff, and offer the "Ask A Librarian" service to different clientele. The article illustrates that both large hospitals with a large library staff and small hospitals with a solo librarian and some volunteers can offer this type of service.  相似文献   

Public Choices and Social Learning: The New Multimedia Technologies in Europe     

Robin Williams 《The Information Society》2000,16(4):251-262

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Talk in Eleven Year Old Children's Response Groups     

Robin J. Dixon 《English in Education》1985,19(2):36-44

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Basecamp     

Robin Featherstone 《Journal of the Medical Library Association》2009,97(1):67

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Checking and adjusting the lens: case study clearance     

Robin Yeomans 《Cambridge Journal of Education》1987,17(2):89-90

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Photo-voltaic cells with silver-silver bromide electrodes. II     

S.E. Sheppard  W. Vanselow  V.C. Hall 《Journal of The Franklin Institute》1929,208(5):681-682

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The formation of systems of units     

William M. Hall 《Journal of The Franklin Institute》1938,225(2):197-218

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#MeToo,sexual harassment: an article,a forum,and a dream for the future     

Robin Patric Clair  Nadia E. Brown  Debbie S. Dougherty  Hannah K. Delemeester  Patricia Geist-Martin  William I. Gorden 《Journal of Applied Communication Research》2019,47(2):111-129

#MeToo has breathed new life into the women’s movement and especially into understanding and rectifying sexual harassment, abuse and assault. It has galvanized activists around the globe. And it has placed thousands of stories of the harassed in full view of the public. Sexual harassment, abuse and assault may occur within the organizational context or beyond; but sexual harassment, in particular has been legally labeled an organizational phenomenon. With this in mind, Robin Clair frames the early part of this article around the most recent organizational communication theories (see the appendix for an overview of these theories). Following the essay is a forum, in which invited scholars address questions related to the #MeToo movement.  相似文献