Muscle coordination,activation and kinematics of world-class and elite breaststroke swimmers during submaximal and maximal efforts     

Bjørn Harald Olstad  João Rocha Vaz  Christoph Zinner  Jan M.H. Cabri  Per-Ludvik Kjendlie 《Journal of sports sciences》2017,35(11):1107-1117

The aims of this study were to describe muscular activation patterns and kinematic variables during the complete stroke cycle (SC) and the different phases of breaststroke swimming at submaximal and maximal efforts. Surface electromyography (sEMG) was collected from eight muscles in nine elite swimmers; five females (age 20.3 ± 5.4 years; Fédération Internationale de Natation [FINA] points 815 ± 160) and four males (27.7 ± 7.1 years; FINA points 879 ± 151). Underwater cameras were used for 3D kinematic analysis with automatic motion tracking. The participants swam 25 m of breaststroke at 60%, 80% and 100% effort and each SC was divided into three phases: knee extension, knee extended and knee flexion. With increasing effort, the swimmers decreased their SC distance and increased their velocity and stroke rate. A decrease during the different phases was found for duration during knee extended and knee flexion, distance during knee extended and knee angle at the beginning of knee extension with increasing effort. Velocity increased for all phases. The mean activation pattern remained similar across the different effort levels, but the muscles showed longer activation periods relative to the SC and increased integrated sEMG (except trapezius) with increasing effort. The muscle activation patterns, muscular participation and kinematics assessed in this study with elite breaststroke swimmers contribute to a better understanding of the stroke and what occurs at different effort levels. This could be used as a reference for optimising breaststroke training to improve performance.  相似文献   

Community cartography in health communication: An asset-based mapping approach in four communities in rural Ecuador     

Benjamin R. Bates  Diana L. Marvel  Claudia Nieto-Sanchez  Mario J. Grijalva 《Journal of International and Intercultural Communication》2019,12(3):228-247

Scholars and practitioners are increasingly turning to maps as tools for promoting health and development communication. These maps are often criticized for privileging the interests of the global North and for authorizing (neo)colonial approaches. The authors offer a case of community mapping incorporating asset-based community development that offers an alternative cartography. Drawing on the maps produced by members of four communities in rural Ecuador, the authors articulate how their maps productively use and challenge assumptions about maps. Following this analysis, the authors offer some implications that community-scale maps have for articulating rhetorical alternatives in health and development communication.  相似文献   

Acute and chronic effect of sodium bicarbonate ingestion on Wingate test performance: a systematic review and meta-analysis     

João Paulo Lopes-Silva  Reid Reale  Emerson Franchini 《Journal of sports sciences》2019,37(7):762-771

The aim of this study was to perform a systematic review and meta-analysis on the acute and chronic effects of sodium bicarbonate (NaHCO₃) ingestion on Wingate performance. Following a search through PubMed, Scopus and Web of Science, 9 studies were found meeting inclusion criteria (6 acute and 3 chronic). Random-effects meta-analysis of standardized mean difference (SMD) for peak and mean power was performed. Study quality was assessed using the QualSyst. Results of the meta-analysis showed that acute ingestion of NaHCO₃ did not improve Wingate test peak (weighted average effect size Hedges’s g = 0.02, 95%CI: – 0.19 to 0.23, P = 0.87) or mean power (weighted average effect size Hedges’s g = 0.15, 95%CI: ?0.06 to 0.36, P = 0.92). However, chronic ingestion of NaHCO₃ improved Wingate test peak (weighted average effect size Hedges’s g = 1.21, 95%CI: 0.83 to 1.42, P = 0.001) and mean power (weighted average effect size Hedges’s g = 1.26, 95%CI: 0.96 to 1.56, P = 0.001). Quality assessment of selected articles was classified as strong. This meta-analysis provides evidence that chronic, but not acute, ingestion of NaHCO₃ increases both Wingate test peak and mean power.  相似文献   

Predicting centre of mass horizontal speed in low to severe swimming intensities with linear and non-linear models     

Kelly de Jesus  Helon Vicente Hultmann Ayala  Leandro dos Santos Coelho  João Paulo Vilas-Boas  Ricardo Jorge Pinto Fernandes 《Journal of sports sciences》2019,37(13):1512-1520

We aimed to compare multilayer perceptron (MLP) neural networks, radial basis function neural networks (RBF) and linear models (LM) accuracy to predict the centre of mass (CM) horizontal speed at low-moderate, heavy and severe swimming intensities using physiological and biomechanical dataset. Ten trained male swimmers completed a 7 × 200 m front crawl protocol (0.05 m.s^?1 increments and 30 s intervals) to assess expiratory gases and blood lactate concentrations. Two surface and four underwater cameras recorded independent images subsequently processed focusing a three-dimensional reconstruction of two upper limb cycles at 25 and 175 m laps. Eight physiological and 13 biomechanical variables were inputted to predict CM horizontal speed. MLP, RBF and LM were implemented with the Levenberg-Marquardt algorithm (feed forward with a six-neuron hidden layer), orthogonal least squares algorithm and decomposition of matrices. MLP revealed higher prediction error than LM at low-moderate intensity (2.43 ± 1.44 and 1.67 ± 0.60%), MLP and RBF depicted lower mean absolute percentage errors than LM at heavy intensity (2.45 ± 1.61, 1.82 ± 0.92 and 3.72 ± 1.67%) and RBF neural networks registered lower errors than MLP and LM at severe intensity (2.78 ± 0.96, 3.89 ± 1.78 and 4.47 ± 2.36%). Artificial neural networks are suitable for speed model-fit at heavy and severe swimming intensities when considering physiological and biomechanical background.  相似文献   

Concurrent Validity and Reliability of Alternative Computer Game for the Coincidence-Anticipation Timing Task     

Tânia Brusque Crocetta  Regiani Guarnieri  Thaís Massetti  Talita Dias da Silva  Renata Thaís de Almeida Barbosa  Jennifer Yohanna Ferreira de Lima Antão 《Measurement in physical education and exercise science》2019,23(2):169-185

The coincidence-anticipation timing (CAT) task assesses one facet of cognitive and motor performance and is used to understand the human visuo-motor system involved in intercepting the moving object. To assess the test–retest reliability and the concurrent validity in the Bridge Games package (Bridge) developed to assess the CAT task, the scores of 224 healthy subjects (M = 52.2, SD = 19.5 years old) were measured using the Bridge and the ‘gold standard’ Bassin Anticipation Timer (Bassin). A mean block of absolute, constant, and variable errors was calculated. Reliability and validity were expressed using intraclass correlation coefficients (ICC_2,k), standard error of measurement, minimal detectable change, and Pearson’s correlation. Reliability was good to excellent for all blocks (.73 ≤ ICC ≤ .88), and the validity was good to excellent when compared using Pearson’s correlation coefficient, suggesting that the two tests may have similar properties. Bridge is an alternative to existing clinical tests for the CAT task.  相似文献   

Insights into Masolino's wall paintings in Castiglione Olona: Advanced reflectance and fluorescence imaging analysis     

Daniela Comelli  Austin Nevin  Gianluca Valentini  Iacopo Osticioli  Emilio Mario Castellucci  Lucia Toniolo  Davide Gulotta  Rinaldo Cubeddu   《Journal of Cultural Heritage》2011,12(1):11-18

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Determination of the prevalence of anabolic steroids, stimulants, and selected drugs subject to doping controls among elite sport students using analytical chemistry     

Thevis M  Sauer M  Geyer H  Sigmund G  Mareck U  Schänzer W 《Journal of sports sciences》2008,26(10):1059-1065

Drug abuse by adolescents has been investigated in various surveys that reported correlations between age, gender, and activity. However, none of these studies included chemical analyses to help substantiate the statements of participants. In the present study, the urine specimens of 964 students (439 females, 525 males; mean age 22.1 years, s = 1.7), who applied to study sports sciences at university, were assessed for anabolic steroids, stimulants, and selected drugs prohibited in sports. In total, 11.2% of the urine specimens provided contained drugs covered by doping controls. The most frequently detected compound was the major metabolite of tetrahydrocannabinol (9.8%) followed by various stimulants related to amphetamine and cocaine (1.0%). Indications of anabolic steroid use were found in 0.4% of urine samples but originated from contraceptives containing norethisterone. The present study provided unambiguous data on the status quo of drug (ab)use by adolescents hoping for a career related to elite sport or sports sciences. No use of anabolic steroids was detected. However, evidence for stimulants and tetrahydrocannabinol administration was obtained, although not reported by any participant, which highlights the issue of under-reporting in surveys based solely on questionnaires.  相似文献   

Extraction of Lipophilic Antioxidants from Native Tomato Using Green Technologies     

Darío R. Gmez-Linton  Arturo Navarro-Ocaa  Silvestre Alavez  Ricardo Lobato-Ortiz  Anglica Romn-Guerrero  Jos Alberto Mendoza-Espinoza  Juan Manuel Villa-Hernndez  Laura J. Prez-Flores 《Food Technology and Biotechnology》2022,60(1):121

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Learning through chemistry simulations: an analysis of cognitive skill levels     

da Silva  Renan Amorim  de Vasconcelos  Flávia Cristina Gomes Catunda 《Education and Information Technologies》2022,27(5):6967-6987

Education and Information Technologies - This paper presents an analysis of cognitive skill levels expressed in high school students’ performance using laboratory simulations. We address...  相似文献   

Exploring the emotional aspect in Learner’s personal annotation colors     

Boutefara  Tarek  Mahdaoui  Latifa  Ghomari  Abdessamed Réda 《Education and Information Technologies》2022,27(5):6173-6195

Education and Information Technologies - A personal annotation is a rich object with an important cognitive facet. In the e-Learning context, learners’ annotation can contain important...  相似文献