Acute responses of biomechanical parameters to different sizes of hand paddles in front-crawl stroke     

Augusto Carvalho Barbosa  Flávio De Souza Castro  Milivoj Dopsaj  Sérgio Augusto Cunha  Orival Andries Júnior 《Journal of sports sciences》2013,31(9):1015-1023

Abstract

This study investigated the acute effects of different sizes of paddles on the force-time curve during tethered swimming and swimming velocity in front-crawl stroke. Fourteen male swimmers (20.0 ± 3.7 years; 100-m best time: 53.70 ± 0.87 s) performed two 10-s maximal efforts in tethered swimming to obtain peak force, average force, impulse, rate of force development, stroke duration and time to peak force. Swimming velocity, stroke rate and stroke length were obtained from two 25-m maximal swims. Both tests were repeated in five conditions: free swimming, wearing small (280 cm ² ), medium (352 cm ² ), large (462 cm ² ) and extra-large (552 cm ² ) hand paddles. Compared to free swimming, paddles provided significant increases of peak force (medium: 11.5%, large: 16.7%, extra-large: 21.7%), impulse (medium: 15.2%, large: 22.4%, extra-large: 30.9%), average force (medium: 5.1%, large: 7.5%), rate of force development (extra-large: 11.3%), stroke duration (medium: 9.3%, large: 11.8%, extra-large: 18.5%), time to peak force (medium: 11.1%, large: 15.9%, extra-large: 22.1%), swimming velocity (medium: 2.2%, large: 3.2%, extra-large: 3.7%) and stroke length (medium: 9.0%, large: 9.0%, extra-large: 14.8%), while stroke rate decreased (medium: –6.2%, large: –5.5%, extra-large: –9.5%). It is concluded that medium, large and extra-large paddles influence the force-time curve and change swimming velocity, suggesting these sizes may be useful for force development in water.  相似文献   

Clinical Trial Registration in Physiotherapy Journals: Recommendations from the International Society of Physiotherapy Journal Editors     

O P Costa Leonardo  Christine Chung-Wei Lin  Debora Grossi Bevilaqua  Marisa Cota Mancini  Anne K Swisher  Chad Cook  Dan Vaughn  Mark R Elkins  Umer Sheikh  Ann Moore  Gwendolen Jull  Rebecca L Craik  Christopher G Maher  Rinaldo Roberto de Jesus Guirro  Amélia Pasqual Marques  Michele Harms  Dina Brooks  Guy G Simoneau  John Henry Strupstad 《Cardiopulmonary Physical Therapy Journal》2013,24(1):4-6

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Cardiac indexes, cardiac damage biomarkers and energy expenditure in professional cyclists during the Giro d'Italia 3-weeks stage race     

Corsetti R  Lombardi G  Barassi A  Lanteri P  Colombini A  D'Eril GM  Banfi G 《Biochemia medica : ?asopis Hrvatskoga dru?tva medicinskih biokemi?ara / HDMB》2012,22(2):237-246

Introduction

The study of cardiac response to strenuous and continuous exercise is crucial to understanding the physiology of endurance. N-terminal proB-type natriuretic peptide (NT-proBNP) is a potential marker for monitoring myocardial wall stress, and troponins (TnT and TnI) are widely used in the diagnosis of cardiac ischemia and infarction. Strenuous exercise may generate transitory ischemia, myocardial stress, and diastolic left ventricular dysfunction, inducing the increased production of both these biomarkers. We measured changes in NT-proBNP and TnT in elite cyclists during a 3-week stage race, a model of strenuous exercise.

Materials and methods:

The study population was 9 professional cyclists participating in the 2011 Giro d’Italia. Pre-analytical and analytical phases scrupulously followed official recommendations. Anthropometric data, net energy expenditure and cardiac indexes (rate, diastolic and systolic blood pressure) were recorded. Blood samples were drawn pre-race (day −1) and at days 12 and 22; NT-proBNP and highly sensitive-troponin (Hs-TnT) concentrations were assayed and corrected for plasma volume changes.

Results:

Body-mass index decreased and energy expenditure increased by 52% during the race. NT-proBNP concentrations increased [day −1: 23.52 ng/L (9.67–34.33); day 12: 63.46 ng/L (22.15–93.31); P = 0.039; day 22: 89.26 ng/L (34.66–129.78) vs. day −1; P < 0.001] and correlated with heart rate (r = −0.51; P = 0.006), systolic pressure (r = 0.39; P = 0.046) and energy expenditure (r = 0.70; P < 0.001). TnT concentrations did not vary, but a widened TnT amplitude distribution was observed.

Conclusions:

Increases in NT-proBNP correlated with higher energy expenditure over a 3-week cycling stage race, possibly indicating myocardial stress.  相似文献   

Isokinetic hamstrings-to-quadriceps peak torque ratio: the influence of sport modality, gender, and angular velocity     

Andrade Mdos S  De Lira CA  Koffes Fde C  Mascarin NC  Benedito-Silva AA  Da Silva AC 《Journal of sports sciences》2012,30(6):547-553

The purpose of this study was to determine differences in hamstrings-to-quadriceps (H/Q) peak torque ratios evaluated at different angular velocities between men and women who participate in judo, handball or soccer. A total of 166 athletes, including 58 judokas (26 females and 32 males), 39 handball players (22 females and 17 males), and 69 soccer players (17 females and 52 males), were evaluated using an isokinetic dynamometer. The H/Q isokinetic peak torque ratios were calculated at angular velocities of 1.05 rad · s?1 and 5.23 rad · s?1. In the analysis by gender, female soccer players produced lower H/Q peak torque ratios at 1.05 rad · s?1 than males involved in the same sport. However, when H/Q peak torque ratio was assessed at 5.23 rad · s?1, there were no significant differences between the sexes. In the analysis by sport, there were no differences among females at 1.05 rad · s?1. In contrast, male soccer players had significantly higher H/Q peak torque ratios than judokas (66 ± 12% vs. 57 ± 14%, respectively). Female handball players produced significantly lower peak torque ratios at 5.23 rad · s?1 than judokas or soccer players, whereas males presented no ratio differences among sports At 5.23 rad · s?1. In the analysis by velocity, women's muscular ratios assessed at 1.05 rad · s?1 were significantly lower than at 5.23 rad · s?1 for all sports; among men, only judokas presented lower ratios at 1.05 rad · s?1 than at 5.23 rad · s?1. The present results suggest that sport modality and angular velocity influence the isokinetic strength profiles of men and women.  相似文献   

Effects of replica running shoes upon external forces and muscle activity during running     

Azevedo AP  Brandina K  Bianco R  Oliveira VH  Souza JR  Mezencio B  Amadio AC  Serrão JC 《Journal of sports sciences》2012,30(9):929-935

Twelve participants ran (9 km · h(-1)) to test two types of running shoes: replica and original shoes. Ground reaction force, plantar pressure and electromyographic activity were recorded. The shoes were tested randomly and on different days. Comparisons between the two experimental conditions were made by analysis of variance (ANOVA) test (P ≤ 0.05). The time to first peak, loading rate of the first peak and impulse of the first 75 ms of stance were significantly different between the shoes (P ≤ 0.05), revealing an increase of impact forces for the replica shoes. The peak plantar pressure values were significantly higher (P ≤ 0.05) when wearing replica shoes. During running, the contact area was significantly smaller (P ≤ 0.05) for the replica shoe. The electromyographic activity of the analysed muscles did not show changes between the two shoes in running. These findings suggest that the use of replica running shoes can increase the external load applied to the human body, but may not change the muscle activity pattern during locomotion. This new mechanical situation may increase the risk of injuries in these movements.  相似文献   

Books received     

Sidney Rosen 《科学教学研究杂志》1966,4(4):293-293

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Knowledge-Enhanced Latent Semantic Indexing     

David Guo  Michael W. Berry  Bryan B. Thompson  Sidney Bailin 《Information Retrieval》2003,6(2):225-250

Latent Semantic Indexing (LSI) is a popular information retrieval model for concept-based searching. As with many vector space IR models, LSI requires an existing term-document association structure such as a term-by-document matrix. The term-by-document matrix, constructed during document parsing, can only capture weighted vocabulary occurrence patterns in the documents. However, for many knowledge domains there are pre-existing semantic structures that could be used to organize and categorize information. The goals of this study are (i) to demonstrate how such semantic structures can be automatically incorporated into the LSI vector space model, and (ii) to measure the effect of these structures on query matching performance. The new approach, referred to as Knowledge-Enhanced LSI, is applied to documents in the OHSUMED medical abstracts collection using the semantic structures provided by the UMLS Semantic Network and MeSH. Results based on precision-recall data (11-point average precision values) indicate that a MeSH-enhanced search index is capable of delivering noticeable incremental performance gain (as much as 35%) over the original LSI for modest constraints on precision. This performance gain is achieved by replacing the original query with the MeSH heading extracted from the query text via regular expression matches.  相似文献   

Three sources of differences between educational and developmental psychology: resolution through educational-developmental psychology     

Sidney Strauss 《Instructional Science》1986,15(1):275-286

Although educational and developmental psychology should inform each other, it is unusual when they do so. Three reasons are offered for the differences between the two psychologies. First, the content of research and purposes for choosing that content are different. Second, the significance of developmental sequences is different for the two psychologies, and the role of values in developmental sequences also differs. And third, there are differences in the search for biologically constrained laws of human cognitive development versus schooling effects. It is suggested that the two psychologies can inform each other. The zone where the two psychologies meet, the zone of educational-developmental psychology, is an emergent area which is neither developmental nor educational psychology as traditionally practiced, but it takes elements from both.This is Working Paper Number 47 of the Tel-Aviv University Unit of Human Development and Education. I would like to thank Pnina Frenkel, Tamar Globerson, Annette Karmiloff-Smith, Iris Levin, Ken Russell, Gavriel Salomon, and Liliana Tolchinsky for extremely valuable comments on an earlier draft of this article.  相似文献   

Letters to the editor     

Sidney L. Pressey  Wm. Clark Trow  Raymond G. Kuhlen  Robert E. Silverman  Donald Snygg 《教育心理学家》2013,48(2):4-5

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Erratum to: Videoconferencing in Math and Science Preservice Elementary Teachers’ Field Placements     

Irene Plonczak  Roberto Joseph  Blidi S. Stemn 《Journal of Science Teacher Education》2010,21(2):275

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