Análise de dados gemelares: uma aventura guiada para investigadores das ciências do desporto

Este tutorial pretende apresentar, de forma sumária: 1) a importância dos estudos gemelares em Educação Física e Ciências do Desporto; 2) a estrutura básica deste tipo de delineamento; 3) as etapas da análise descritiva inicial; 4) os procedimentos de análise em grau crescente de complexidade - da análise de variância, à modelação de estruturas de covariância; 5) bem como a relevância da exploração da disocordância intrapar de gêmeos monozigóticos. Esta processologia, baseada num tutorial, recorrerá aos valores do fenótipo índice de atividade física nos tempos de lazer, com base numa amostra de 207 pares de gêmeos mono e dizigóticos. Todas as etapas da análise são comentadas e será interpretado o signifi cado dos resultados, salientando o fato do fenótipo em causa ser explicado pelos fatores genéticos em cerca de 63%.

Validez de contenido de un cuestionario para evaluar las etapas del cambio de comportamiento en estilos de vida en escolares, Colombia: Estudio FUPRECOL

Estudio de validación en escolares pertenecientes a instituciones educativas oficiales de la ciudad de Bogotá, Colombia. Se diseñó y aplicó el CCC-FUPRECOL que indagó por las etapas de cambio para la actividad física/ejercicio, consumo de frutas, verduras, drogas, tabaco e ingesta de bebidas alcohólicas, de manera auto-diligenciada por formulario estructurado.

Imaginarios sociales de adolescentes y docentes en torno al cuerpo, la corporalidad y la actividad física. Estudio cualitativo en un colegio de Bogotá, 2014-2015.

Problema. Esta investigación se aproxima al entorno escolar con el propósito de avanzar en la comprensión de los imaginarios de los adolescentes y docentes en torno al cuerpo, la corporalidad y la AF, como un elemento relevante en el diseño de programas y planes efectivos para fomento de la práctica de AF. Objetivo. Analizar los imaginarios sociales de docentes y adolescentes en torno a los conceptos de cuerpo, corporalidad y AF. Métodos. Investigación de corte cualitativo, descriptivo e interpretativo. Se realizaron entrevistas semi-estructuradas a docentes y a estudiantes entre los 12 y 18 años de un colegio público de Bogotá. Se realizó análisis de contenido. Se compararon los resultados de estudiantes por grupos de edades y género. Resultados. Docentes y estudiantes definen el cuerpo a partir de las características biológicas, las diferencias sexuales y las funciones vitales. La definición de corporalidad en los estudiantes se encuentra ligada con la imagen y la apariencia física; los docentes la entienden como la posibilidad de interactuar con el entorno y como la materialización de la existencia. La AF en los estudiantes se asocia con la práctica de ejercicio y deporte, en los docentes se comprende como una práctica de autocuidado que permite el mantenimiento de la salud. Conclusiones. Para promover la AF tempranamente como una experiencia vital es necesario intervenir los espacios escolares. Hay que vincular al cuerpo a los procesos formativos con el propósito de desarrollar la autonomía corporal, este aspecto implica cambios en los currículos.

Relación entre estrés y desórdenes músculo esqueléticos en trabajadores de una empresa de transporte terrestre de pasajeros, Bogotá, 2015.

Introducción. Los conductores de transporte terrestre de pasajeros están expuestos a factores de riesgo inherentes a su labor, por lo que la intervención sobre estos factores es un aspecto relevante en las empresas de transporte público dado que dicha actividad afecta la calidad de vida de los mismos. Objetivo: Determinar la prevalencia de estrés en el lugar de trabajo y los factores de riesgo biomecánicos asociados en trabajadores de una empresa de transporte terrestre de pasajeros. Materiales y métodos: Estudio de corte transversal con datos secundarios procedentes de una población de 219 empleados, de los cuales 13 eran administrativos y 206 laboraban en la operación de una empresa de transporte terrestre de pasajeros. Las variables incluidas fueron socio demográficas, laborales, variables relacionadas con la medición de estrés y síntomas osteomusculares. El análisis estadístico incluyó medidas de tendencia central y dispersión y para identificar los factores asociados con el estrés se utilizaron pruebas de asociación Chi2 y prueba exacta de Fisher. Resultados: La edad promedio de los participantes fue de 43 años (DS 10 años), siendo en su mayoría trabajadores de sexo masculino (96,3%). Se presentaron síntomas y factores de riesgo biomecánicos en cuello y espalda en un 55.5%. Se encontró asociación significativa entre estrés con los síntomas en pies (p=0,009), con los factores de riesgo biomecánicos, se encontró relación significativa con el tiempo que permanece adoptando las posturas de inclinación hacia delante (p=0,000) y hacia atrás (p=0,001) de espalda/tronco y las posturas en muñecas, (p=0,000), y a la exposición de los conductores a superficies vibrantes (asientos de vehículo) (p=0,021). No se encontró asociación significativa entre estrés y la postura de sedente. Conclusiones: Con este estudio se encontró una prevalencia de estrés de 78% en el lugar de trabajo y de los factores de riesgo biomecánicos asociados a antigüedad, postura y repetitividad de movimientos, con repercusiones en cuello y espalda lumbar, por lo tanto, se requiere de un seguimiento a las condiciones de salud y trabajo para los empleados del sector transporte.

Corrupción, incentivos y contrabando técnico en Colombia : 1998 – 2013

El contrabando técnico representa un problema para los hacedores de política económica pues tiene efectos perversos en temas fundamentales como la hacienda pública, la competencia de mercado y la informalidad. Sin embargo, a pesar de ser un problema tan importante son pocos los esfuerzos empíricos que se han hecho para estudiar los incentivos que están detrás de esta práctica ilegal, tanto a nivel global como para el caso colombiano. En este trabajo se desarrolla un modelo teórico a partir del cual se estudian los incentivos para la existencia del contrabando, y sus conclusiones se contrastan con una aplicación empírica en la que se utilizan datos de importaciones (reporte de origen y destino) de 24 sectores económicos (583 productos) provenientes de 84 países entre 1998 y 2013. Con estos datos se estima un modelo de panel de datos en el que se encuentra que hay una relación positiva entre la corrupción y el contrabando y también entre los aranceles y el contrabando técnico, indicando que se presenta una mayor subfacturación en productos que tienen aranceles altos y provienen de países más corruptos.

Actitudes de un grupo de directivos de empresa hacia la integración laboral de personas en proceso de reintegración en Colombia

Colombia atraviesa un proceso de desmovilización y una de las metas es la reintegración laboral, entendida como el proceso a través del cual las personas que han hecho parte de un grupo armado ilegal obtienen un empleo y se insertan definitivamente a la sociedad. El presente estudio tiene como objetivo fundamental comprender las actitudes de un grupo de tres directivos hacia la vinculación laboral de las personas en proceso de reintegración laboral (PPR), mediante un diseño cualitativo. Para ello, se llevó a cabo una serie de entrevistas semiestructuradas a una muestra de tres directivos del sector público y privado. La información obtenida se analizó mediante un proceso de codificación axial. Los resultados obtenidos evidencian que las actitudes de los tres empresarios frente a la contratación de personas en proceso de reintegración laboral, pueden ser positivas o negativas. Así mismo, una de las actitudes predominantes, son la evaluación de creencias y prejuicios de los empresarios frente al proceso de integración laboral, estos son: la incertidumbre frente al desempeño laboral del PPR, la falta de dedicación por parte del PPR, los posibles conflictos laborales y la dificultad de relacionamiento del PPR. En conclusión, el modelo del comportamiento organizacional juega un papel muy importante, dado que abarca los elementos que influyen y determinan la construcción de las actitudes. Estas guían la evaluación de conductas que pueden ser a favor o en contra, de diversos ámbitos del proceso de contratación de personas desmovilizadas.

Customer Loyalty toward grocery retailing service: a multidimensional approach to costumer perceived value

Structured abstract Purpose: To deepen, in grocery retail context, the roles of consumer perceived value and consumer satisfaction, as antecedents’ dimensions of customer loyalty intentions. Design/Methodology/approach: Also employing a short version (12-items) of the original 19-item PERVAL scale of Sweeney & Soutar (2001), a structural equation modeling approach was applied to investigate statistical properties of the indirect influence on loyalty of a reflective second order customer perceived value model. The performance of three alternative estimation methods was compared through bootstrapping techniques. Findings: Results provided i) support for the use of the short form of the PERVAL scale in measuring consumer perceived value; ii) the influence of the four highly correlated independent latent predictors on satisfaction was well summarized by a higher-order reflective specification of consumer perceived value; iii) emotional and functional dimensions were determinants for the relationship with the retailer; iv) parameter’s bias with the three methods of estimation was only significant for bootstrap small sample sizes. Research limitations:/implications: Future research is needed to explore the use of the short form of the PERVAL scale in more homogeneous groups of consumers. Originality/value: Firstly, to indirectly explain customer loyalty mediated by customer satisfaction it was adopted a recent short form of PERVAL scale and a second order reflective conceptualization of value. Secondly, three alternative estimation methods were used and compared through bootstrapping and simulation procedures.

Antecedentes do relacionamento e da performance em empresas da cadeia de suprimentos: estruturação e aplicação de modelos de equações estruturais

The relationship between companies is an important issue in the management of supply chains. Several aspects relating to the flow and exchange of information along the chain are considered as having a decisive influence on the success of this relationship. The main objective of this work was to structured and test models that link aspects of this nature with performance and the purchaser-supplier relationship in the supply chain. Aspects relevant to communication and the use do IT in relationships between companies were investigated. The importance of performance in this relationship was also investigated. The research were based on empirical data obtained by means of structural equation modeling. The results show that some aspects contribute in a significant way to the success of this relationship while others that, a priori, are considered important make no contribution.

Metodologia para análise da confiabilidade estrutural de escavações em rocha.

A methodology for rock-excavation structural-reliability analysis that uses Distinct Element Method numerical models is presented. The methodology solves the problem of the conventional numerical models that supply only punctual results and use fixed input parameters, without considering its statistical errors. The analysis of rock-excavation stability must consider uncertainties from geological variability, from uncertainty in the choice of mechanical behaviour hypothesis, and from uncertainties in parameters adopted in numerical model construction. These uncertainties can be analyzed in simple deterministic models, but a new methodology was developed for numerical models with results of several natures. The methodology is based on Monte Carlo simulations and uses principles of Paraconsistent Logic. It will be presented in the analysis of a final slope of a large-dimensioned surface mine.

Goals and reputations amongst young children - The validation of the importance of goals and reputation enhancement scales

The aim of the present research was to provide school psychologists with valid instruments with which to assess the goals and reputations of young children. This was achieved by ascertaining whether the factor structures and the second-order factor models of the high school versions of the Importance of Goals (Carroll, et al., 1997) and Reputation Enhancement Scales (Carroll, et al., 1999) could be replicated with a primary school sample. Eight hundred and eighty-six 10 to 12 year old children were administered modified versions of the two scales, which were combined and renamed the Children's Activity Questionnaire. For the two scales, the factor structure proved replicable and reliable with the primary school sample. A comparison between the factor loadings of the primary school and the high school samples using the coefficient of congruence procedure demonstrated similarity indicating that the scales are replicable and able to be used with a younger primary school sample. Structural equation modelling indicated that the second-order factor structure of the Importance of Goals Scale was acceptable but this was not the case for the second-order factor structure of the Reputation Enhancement Scale.

Natural selection and quantitative genetics of life-history traits in Western women: A twin study

Whether contemporary human populations are still evolving as a result of natural selection has been hotly debated. For natural selection to cause evolutionary change in a trait, variation in the trait must be correlated with fitness and be genetically heritable and there must be no genetic constraints to evolution. These conditions have rarely been tested in human populations. In this study, data from a large twin cohort were used to assess whether selection Will cause a change among women in contemporary Western population for three life-history traits: age at menarche, age at first reproduction, and age at menopause. We control for temporal variation in fecundity (the baby boom phenomenon) and differences between women in educational background and religious affiliation. University-educated women have 35% lower fitness than those with less than seven years education, and Roman Catholic women have about 20% higher fitness than those of other religions. Although these differences were significant, education and religion only accounted for 2% and 1% of variance in fitness, respectively. Using structural equation modeling, we reveal significant genetic influences for all three life-history traits, with heritability estimates of 0.50, 0.23, and 0.45, respectively. However, strong genetic covariation with reproductive fitness could only be demonstrated for age at first reproduction, with much weaker covariation for age at menopause and no significant covariation for age at menarche. Selection may, therefore, lead to the evolution of earlier age at first reproduction in this population. We also estimate substantial heritable variation in fitness itself, with approximately 39% of the variance attributable to additive genetic effects, the remainder consisting of unique environmental effects and small effects from education and religion. We discuss mechanisms that could be maintaining such a high heritability for fitness. Most likely is that selection is now acting on different traits from which it did in pre-industrial human populations.

Determinants of general practitioner use among women in Australia

This study investigates the use of general practitioner services by women in Australia. Although there is a universal health insurance system (Medicare) in Australia, there are variations in access to services and out of pocket costs for services. Survey data from 2350 mid-age (45-50 years) and 2102 older (70-75 years) women participating in the Australian Longitudinal Study on Women's Health were linked with Medicare data to provide a range of individual and contextual variables hypothesised to explain general practitioner use. Structural equation modelling showed that physical health was the most powerful explanatory factor of general practitioner use. However, after adjusting for self-reported health, out of pocket cost per consultation was inversely associated with use of services. The out of pocket cost was generally lower for women with low socioeconomic status but cost was also directly related to geographical remoteness. Women living in more remote areas had higher out of pocket costs and poorer access to services. Women who reported better access to care were more likely to be satisfied with their most recent general practice consultation and less likely to be sceptical of the value of medical care. These results show the need for health policies that improve the equitable use of general practitioner services in Australia. (C) 2001 Elsevier Science Ltd. All rights reserved.

Developmental genetics of red cell indices during puberty: A longitudinal twin study

Red cell number and size increase during puberty, particularly in males. The aim of the present study was to determine whether expression of genes affecting red cell indices varied with age and sex. Haemoglobin, red cell count, and mean cellular volume were measured longitudinally on 578 pairs of twins at twelve, fourteen and sixteen years of age. Data were analysed using a structural equation modeling approach, in which a variety of univariate and longitudinal simplex models were fitted to the data. Significant heritability was demonstrated for all variables across all ages. The genes involved did not differ between the sexes, although there was evidence for sex limitation in the case of haemoglobin at age twelve. Longitudinal analyses indicated that new genes affecting red cell indices were expressed at different stages of puberty. Some of these genes affected the different red cell indices pleiotropically, while others had effects specific to one variable only.

Biometrical Genetics

Biometrical genetics is the science concerned with the inheritance of quantitative traits. In this review we discuss how the analytical methods of biometrical genetics are based upon simple Mendelian principles. We demonstrate how the phenotypic covariance between related individuals provides information on the relative importance of genetic and environmental factors influencing that trait, and how factors such as assortative mating, gene-environment correlation and genotype-environment interaction complicate such interpretations. Twin and adoption studies are discussed as well as their assumptions and limitations. Structural equation modeling (SEM) is introduced and we illustrate how this approach may be applied to genetic problems. In particular, we show how SEM can be used to address complicated issues such as analyzing the causes of correlation between traits or determining the direction of causation (DOC) between variables. (C) 2002 Elsevier Science B.V. All rights reserved.

Repeated blood pressure measurements in a sample of Swedish twins: heritabilities and associations with polymorphisms in the renin-angiotensin-aldosterone system Iliadou, Anastasia, Lichtenstein, Paul, Morgenstern, Ralf, Forsberg, Lena, Svensson, Richard, de Faire, Ulf, Martin, Nicholas, Pedersen, Nancy

Background Twin and family studies have shown that genetic effects explain a relatively high amount of the phenotypic variation in blood pressure. However, many studies have not been able to replicate findings of association between specific polymorphisms and diastolic and systolic blood pressure. Methods In a structural equation-modelling framework the authors investigated longitudinal changes in repeated measures of blood pressures in a sample of 298 like-sexed twin pairs from the population-based Swedish Twin Registry. Also examined was the association between blood pressure and polymorphisms in the angiotensin-I converting enzyme and the angiotensin 11 receptor type 1 with the 'Fulker' test Both linkage and association were tested simultaneously revealing whether the polymorphism is a Quantitative Trait Locus (QTL) or in linkage disequilibrium with the QTL. Results Genetic influences explained up to 46% of the phenotypic variance in diastolic and 63% of the phenotypic variance in systolic blood pressure. Genetic influences were stable over time and contributed up to 78% of the phenotypic correlation in both diastolic and systolic blood pressure. Non-shared environmental effects were characterised by time specific influences and little transmission from one time point to the next. There was no significant linkage and association between the polymorphisms and blood pressure. Conclusions There is a considerable genetic stability in both diastolic and systolic blood pressure for a 6-year period of time in adult life. Non-shared environmental influences have a small long-term effect Although associations with the polymorphisms could not be replicated, results should be interpreted with caution due to power considerations. (C) 2002 Lippincott Williams Wilkins.