Influence of upright versus time trial cycling position on determination of critical power and W′ in trained cyclists     

Mehdi Kordi  Chris Fullerton  Louis Passfield  Len Parker Simpson 《European Journal of Sport Science》2019,19(2):192-198

Body position is known to alter power production and affect cycling performance. The aim of this study was to compare mechanical power output in two riding positions, and to calculate the effects on critical power (CP) and W′ estimates. Seven trained cyclists completed three peak power output efforts and three fixed-duration trial (3-, 5- and 12-min) riding with their hands on the brake lever hoods (BLH), or in a time trial position (TTP). A repeated-measures analysis of variance showed that mean power output during the 5-min trial was significantly different between BLH and TTP positions, resulting in a significantly lower estimate of CP, but not W′, for the TTP trial. In addition, TTP decreased the performance during each trial and increased the percentage difference between BLH and TTP with greater trial duration. There were no differences in pedal cadence or heart rate during the 3-min trial; however, TTP results for the 12-min trial showed a significant fall in pedal cadence and a significant rise in heart rate. The findings suggest that cycling position affects power output and influences consequent CP values. Therefore, cyclists and coaches should consider the cycling position used when calculating CP.  相似文献   

Resting MAPK expression in chronically trained endurance runners     

Justin X. Nicoll  Andrew J. Galpin  Donald B. Thomason  Christopher A. Moore 《European Journal of Sport Science》2017,17(9):1194-1202

Purpose: There is a paucity of research investigating the expression of mitogen-activated protein kinases (MAPK) in chronically trained (CT) athletes. Thus, it is unclear how MAPK may contribute to performance and muscle adaptation in CT subjects. The purpose of this study was to determine MAPK total protein, and phosphorylated expression of extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38-MAPK (p38) between untrained, and chronically trained runners. Methods: Tissue samples were analysed from sedentary (SED; n?=?5) controls and chronically trained runners (CT; n?=?5). Resting muscle biopsy samples were analysed for total-MAPK – and ratio of phosphorylated/total (p-MAPK) – ERK1/2, JNK, and p38-MAPK via western blotting. Mann–Whitney U tests and effect sizes were utilized to determine differences in total MAPK protein content and phosphorylation status between SED and CT subjects. Results: There was no difference in total-MAPK expression between SED and CT (p?>?.05). p-p38-MAPK tended to be greater for CT compared to SED (p?=?.07). There were moderate effect sizes of decreased pERK/total-ERK (d?=??0.69) and increased pJNK/total-JNK (d?=?0.54) in CT compared to SED. There was a positive correlation between p-p38-MAPK/total-MAPK and the percentage of type I fibres (r?=?0.73, p?=?.016). Conclusion: Contrary to previous studies, chronic endurance training does not greatly influence total MAPK protein expression in chronically trained runners. However, resting phosphorylation of p38-MAPK may contribute to enhanced oxidative metabolism at chronically trained levels. These alterations are likely involved in the different physiological adaptations that occur following long-term training or at highly competitive levels.  相似文献   

Regular class teachers' perceptions of transition programs for EMR students and their impact on the students     

Donald L. MacMillan  C. Edward Meyers  Roland K. Yoshida 《Psychology in the schools》1978,15(1):99-103

This study was designed to obtain the perceptions of regular class teachers who taught children who had been in EMR programs, but had been decertified (D) and returned to regular classes in response to court cases and recent legislation. A cohort of regular class (RC) students were selected for comparative purposes. It was found that D students were placed into low ability classes; yet, teachers perceived D subjects to be significantly lower than RC students in both academic achievement and social acceptance. Only a small proportion of teachers indicated that the enrollment of D students had much impact on the regular class instructional program. However, the teachers were rather critical of the services received under the auspices of a transitional program, indicating in large part that the services were either not apparent or ineffective.  相似文献   

Predicting student self-concept,anxiety, and responsibility from self-evaluation and self-praise     

Peter J. Brady  Cyril I. Figuerres  Donald W. Felker  Wayne M. Garrison 《Psychology in the schools》1978,15(3):434-438

Nineteen elementary teachers were observed for the frequency with which they modeled self-praise for their students and taught their students to praise and evaluate themselves. Measures of student self-concept, anxiety, and achievement responsibility were taken at the end of the year. It was found that teacher modeling of self-praise correlated negatively with boys' selfconcept and positively with girls'. Teacher encouragement of students to praise other students correlated positively with boys' anxiety and negatively with girls'. Teacher modeling of self-praise and teacher encouragement of students to praise other students were the best predictors of self-concept.  相似文献   

Comparison between artificial and natural solarization and stabilization of special ultraviolet transmitting glasses commercially on the market     

Donald C. Stockbarger  Lyman B. Johnson 《Journal of The Franklin Institute》1930,210(4):455-459

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Coordination variability and skill development in expert triple jumpers   总被引：1，自引：0，他引：1  

Wilson C  Simpson SE  van Emmerik RE  Hamill J 《Sports biomechanics / International Society of Biomechanics in Sports》2008,7(1):2-9

The aim of this study was to examine the influence of skill of expert triple jumpers on the coordination variability of lower extremity intra-limb couplings. In contrast to the traditional motor learning perspective, we hypothesized that as skill and thus performance increases, movement coordination variability will also increase. Three-dimensional kinematic and ground reaction force data were collected during the hop-step transition phase of the triple jump. Relative motion plots and a modified vector coding technique were used to quantify the coordination variability across the trials. The results were consistent with a U-shaped curve, representing coordination variability, as skill increases. The high coordination variability in less skilled athletes is present while the appropriate characteristics defining the movement coordination patterns are acquired. This coordination variability may not be beneficial to performance. As the refinement of these characteristics is achieved, coordination variability decreases, resulting in a more consistent or regulated performance. In the final stages of developing a skilled performance, a functional variability is accessed that brings flexibility to the system allowing it to cope with perturbations. This study highlights the need to address the learning effect when analysing coordination variability from a dynamical systems perspective.  相似文献   

The effects of synchronous music on 400-m sprint performance     

Simpson SD  Karageorghis CI 《Journal of sports sciences》2006,24(10):1095-1102

The aim of the present study was to assess the effects of motivating and oudeterous (neither motivating nor demotivating) synchronous music on 400-m sprint performance while controlling for the potential confound of pre-performance mood. A panel of volunteer Caucasian males (n = 20; mean age = 20.5 years, s = 1.2) rated the motivational qualities of 32 musical selections using the Brunel Music Rating Inventory-2. An experimental group of volunteer Caucasian males (n = 36; mean age = 20.4 years, s = 1.4) completed three 400-m time trials under conditions of motivational music, oudeterous music, and a no-music control. Pre-performance mood was assessed using the Brunel University Mood Scale (BRUMS). A series of repeated-measures analyses of variance with Bonferroni adjustment revealed no differences in the BRUMS subscales. A repeated-measures analysis of variance on the 400-m times showed a significant effect (F1.24, 42.19 = 10.54, P < 0.001, eta 2 = 0.24) and follow-up pair wise comparisons revealed differences between the synchronous music conditions and the control condition. This finding supported the first research hypothesis, that synchronous music would result in better performance than a no-music control, but not the second hypothesis, that performance in the motivational synchronous music condition would be better than that in the oudeterous condition. It appears that synchronous music can be applied to anaerobic endurance performance among non-elite sports persons with a considerable positive effect.  相似文献   

Mathematics,queen and servant of science: by E. T. Bell. 437 pages,illustrations, 14 × 21 cm. New York,McGraw-Hill Book Co., 1951. Price, $5.00     

Donald B. Houghton 《Journal of The Franklin Institute》1951,251(5):555

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Book reviews     

J. Bruce Francis  Michalina Vaughan  Colin Flood Page  Sally Tomlinson  R. A. Becher  Margaret C. Ives  John Urry  K. G. Collier  Meir Zadok  Charles Carter  Jürgen Schramm  Jean Barry  Graeme C. Moodie  Donald Bligh  R. A. King  D. G. Mulcahy  Peter Scott  F. R. Charmer  T. R. Bone  John A. Hughes  Roger Greenhough  Alec M. Ross  John Wakeford  Joyce Skinner  Duncan B. Nimmo  Cedric Cullingford  L. R. B. Elton 《Higher Education》1979,8(6):709-744

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Book reviews     

A. G. M. Ishumi  Birgit Brock Utne  Donald P. Ely  Arthur Gillette 《Prospects》1979,9(1):115-121

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