Comparison of anthropometric indicators as predictors of the percentage of fat mass in young people and older adults in Chile.

OBJECTIVE: To verify whether triponderal mass index (TMI) has a greater accuracy than body mass index (BMI), waist circumference (WC) and waist-to-height ratio (WHtR) as predictors of obesity in young people and older adults in a region of Chile. MATERIAL AND METHODS: A cross-sectional descriptive study was carried out in 1176 adults (565 men and 611 women) from the Maule region (Chile). Their ages ranged from 20 to 80 years. The percentage of fat mass (%FM) was evaluated by means of dual energy X-ray absorptiometry (DXA). Weight, height and waist circumference (WC) were evaluated. TMI, BMI and WHtR were calculated. RESULTS: The %FM predictions for BMI were 0.47% for men and 0.50% for women; for TMI, it was 0.50% for men and 0.51% for women; for WC, it was 0.28% for men and 0.21% for women; and finally, for WHtR, it was 0.28% in men and 0.21% in women. The area under the curve (AUC) for BMI was 0.85 in men and 0.85 in women; for TMI, it was 0.87 in men and 0.86 in women; for WHtR, it was 0.76 in men and 0.72 in women; and for WC, the AUC was 0.72 in men and 0.71 in women. CONCLUSION: It was shown that TMI is the indicator that presented the greatest association with %FM and estimates body fat levels with greater precision than BMI, WC and WHtR. The results suggest its use and application as an indicator that discriminates obesity in young, middle-aged and elderly adults.

Relationship between age and handgrip strength: Proposal of reference values from infancy to senescence.

Introduction: Measurement of hand grip strength (HGS) has been proposed as a key component of frailty and has also been suggested as a central biomarker of healthy aging and a powerful predictor of future morbidity and mortality. Objectives: (a) To determine whether a nonlinear relationship model could improve the prediction of handgrip strength (HGS) compared to the linear model and (b) to propose percentiles to evaluate HGS according to age and sex for a regional population of Chile from infancy to senescence. Methods: A cross-sectional descriptive study was developed in a representative sample of the Maule region (Chile). The volunteers amounted to 5,376 participants (2,840 men and 2,536 women), with an age range from 6 to 80 years old. Weight, height, HGS (right and left hand) according to age and sex were evaluated. Percentiles were calculated using the LMS method [(L (Lambda; asymmetry), M (Mu; median), and S (Sigma; coefficient of variation)]. Results and discussion: There were no differences in HGS from 6 to 11 years of age in both sexes; however, from 12 years of age onwards, males presented higher HGS values in both hands (p < 0.05). The linear regression between age with HGS showed values of R 2 = 0.07 in males and R 2 = 0.02 in females. While in the non-linear model (cubic), the values were: R 2 = 0.50 to 0.51 in men and R 2 = 0.26 in women. The percentiles constructed by age and sex were: P5, P15, P50, P85, and P95 by age range and sex. This study demonstrated that there is a nonlinear relationship between chronological age with HGS from infancy to senescence. Furthermore, the proposed percentiles can serve as a guide to assess and monitor upper extremity muscle strength levels at all stages of life.

Comparison of anthropometric indicators as predictors of the percentage of fat mass in young people and older adults in Chile. / Comparación de indicadores antropométricos como predictores del porcentaje de masa grasa en jóvenes y adultos mayores de Chile.

OBJECTIVE: To verify whether tri-ponderal mass index (TMI) has a higher accuracy than body mass index (BMI), waist circumference (WC) and waist-to-height ratio (WHtR) as predictors of obesity in young people and older adults in a region of Chile. MATERIAL AND METHODS: A cross-sectional descriptive study was carried out in 1,176 adult subjects (565 men and 611 women) from the Maule region (Chile). The age range was from 20 to 80 years old. The percentage of fat mass (%FM) was evaluated by means of dual energy X-ray absorptiometry (DXA). Weight, height and WC were evaluated. TMI, BMI and WHtR were calculated. RESULTS: The predictions of %FM for BMI were 0.47% for men and 0.50% for women, for TMI it was 0.50% for men and 0.51% for women, for WC it was 0.28% for men and 0.21% for women, and finally, for the WHtR it was 0.28% in men and 0.21% in women. The area under the curve (AUC) for the BMI was 0.85 in both men and women, for the TMI, it was 0.87 in men and 0.86 in women, for the WHtR, in men it was 0.76 and in women it was 0.72, and for WC, the AUC in men was 0.72 and in women it was 0.71. CONCLUSION: It was shown that TMI is the indicator that presented the greatest association with %FM and estimates body fat levels with greater precision than BMI, WC and WHtR. The results suggest its use and application as an indicator that discriminates obesity in young, middle and late-aged adults.

Relationship between muscular fitness and bone health in young baseball players.

The physical actions developed by baseball players can increase muscular fitness, and consequently improve bone health. The objective was to relate some indicators of muscular fitness to bone health in young baseball players. A descriptive cross-sectional study was carried out in 102 children and adolescent baseball players of the Brazilian National Team. The age range ranged from 9.0 to 15.0 years, the average chronological age was 12.2±2.2 years and the maturity status was 14.8±0.5 APHV (age at peak height velocity). Anthropometry, body composition [% fat, fat mass (FM) and fat-free mass (FFM)], physical tests [horizontal jump (HJ) and medicine ball throw (MBT)] bone health was estimated by anthropometry [bone mineral density (BMD) and bone mineral content (BMC)]. There was positive and significant correlation between bone health with FFM (r2= 89%) and with muscle strength tests (HJ and MBT) (R2= 55 to 75%). Young baseball players classified with low bone health level, reflected decreased values of FFM, HJ and MBT, in relation to young players classified with moderate and high bone health level (p<0.05). It was shown that good bone health is a consequence of a greater presence of muscular fitness, as a result of increased physical activity. These results suggest that emphasis should be placed on those young people who present a greater risk of having low BMD and BMC.

Muscle Mass in Children and Adolescents: Proposed Equations and Reference Values for Assessment.

Objectives: The goal of this study was to develop regression equations to estimate LM with anthropometric variables and to propose percentiles for evaluating by age and sex. Methods: A cross sectional study was conducted with 2,182 Chilean students (1,347 males and 835 females). Ages ranged from 5.0 to 17.9 years old. A total body scan was carried out with the double energy X-ray anthropometry (DXA) to examine and measure lean muscle mass of the entire body. Weight, height, and the circumference of the relaxed right arm were also measured. Results: Four anthropometric equations were generated to predict lean mass for both sexes (R 2 = 83-88%, SEE = 3.7-5.0%, precision = 0.90-0.93, and accuracy = 0.99). The Lambda-mu-sigma method was used to obtain the sex-specific and age-specific percentile curves of lean mass (p3, p5, p10, p15, p25, p50, p75, p85, p90, p95, and p97). Conclusion: The four proposed equations were acceptable in terms of precision and accuracy to estimate lean mass in children and adolescents. The percentiles were created by means of anthropometric equations and real values for DXA. These are fundamental tools for monitoring LM in Chilean children and adolescents of both sexes.

Evaluación de los trastornos del sueño y propuesta de percentiles para los adolescentes / Assessment of sleep disorders and proposed percentiles for adolescents

Objetivos. Los objetivos del estudio fueron los siguientes: a) construir un instrumento válido y confiable que evaluara, por autoinforme, los trastornos del sueño en adolescentes escolares chilenos y b) desarrollar valores percentílicos según la edad y el sexo. Metodología. Se efectuó un estudio de tipo descriptivo de corte transversal en 2310 adolescentes escolares de la Región del Maule, Chile. Se construyó el autoinforme de trastornos del sueño considerando cinco categorías (duración, alteraciones, problemas en la respiración, fatiga y uso de estimulantes). Se validó por medio del análisis factorial confirmatorio. La fiabilidad se evaluó por la consistencia interna. Se crearon percentiles a través del método LMS (L: asimetría, M: mediana y S: coeficiente de variación). Resultados. Las preguntas 3, 9 y 12 presentaron saturaciones inferiores a 0,40, y las demás preguntas reflejaron saturaciones superiores a 0,41. El valor de adecuación Kaiser-Meyer-Olkin fue 0,749 y la prueba de esfericidad de X2= 4790,09; el porcentaje de la varianza explicó el 62,1 %. El alfa de Cronbach mostró valores entre 0,71 y 0,76. Conclusión. El autoinforme desarrollado para medir los trastornos del sueño en los adolescentes puede ser aplicado de forma válida y confiable en programas de ciencias de la salud, de la educación y del deporte. Se sugiere el uso de percentiles para identificar los patrones normales y/o trastornos del sueño por edad y género.

Objectives. The objectives of this study included: a) to develop a valid and reliable self-reporting instrument to assess sleep disorders among Chilean adolescent students and b) to develop percentiles for age and sex. Methodology. This was a descriptive, crosssectional study in 2310 adolescent students conducted in the Maule Region, Chile. The sleep disorder self-report was developed considering five categories: duration, alterations, breathing problems, fatigue, and stimulant use. The instrument was validated using a confirmatory factor analysis. Reliability was assessed based on internal consistency. Percentiles were developed using the LMS method (L: lambda, asymmetry; M: mu, median; S: sigma, coefficient of variation). Results. Questions 3, 9, and 12 showed saturation values below 0.40, while the rest had saturation values above 0.41. The Kaiser-Meyer-Olkin measure of adequacy was 0.749 and the test of sphericity X2 was 4790.09; the percentage of variance accounted for 62.1%. Cronbach's alpha ranged between 0.71 and 0.76. Conclusion. The self-report developed to measure sleep disorders in adolescents is valid and reliable for its use in health, education, and sports science programs. Percentiles should be used to identify normal patterns and/or sleep disorders by sex and age.

Assessment of sleep disorders and proposed percentiles for adolescents. / Evaluación de los trastornos del sueño y propuesta de percentiles para los adolescentes.

OBJECTIVES: The objectives of this study included: a) to develop a valid and reliable self-reporting instrument to assess sleep disorders among Chilean adolescent students and b) to develop percentiles for age and sex. METHODOLOGY: This was a descriptive, crosssectional study in 2310 adolescent students conducted in the Maule Region, Chile. The sleep disorder self-report was developed considering five categories: duration, alterations, breathing problems, fatigue, and stimulant use. The instrument was validated using a confirmatory factor analysis. Reliability was assessed based on internal consistency. Percentiles were developed using the LMS method (L: lambda, asymmetry; M: mu, median; S: sigma, coefficient of variation). RESULTS: Questions 3, 9, and 12 showed saturation values below 0.40, while the rest had saturation values above 0.41. The Kaiser-Meyer-Olkin measure of adequacy was 0.749 and the test of sphericity X2 was 4790.09; the percentage of variance accounted for 62.1 %. Cronbach's alpha ranged between 0.71 and 0.76. CONCLUSION: The self-report developed to measure sleep disorders in adolescents is valid and reliable for its use in health, education, and sports science programs. Percentiles should be used to identify normal patterns and/or sleep disorders by sex and age.

Objetivos. Los objetivos del estudio fueron los siguientes: a) construir un instrumento válido y confiable que evaluara, por autoinforme, los trastornos del sueño en adolescentes escolares chilenos y b) desarrollar valores percentílicos según la edad y el sexo. Metodología. Se efectuó un estudio de tipo descriptivo de corte transversal en 2310 adolescentes escolares de la Región del Maule, Chile. Se construyó el autoinforme de trastornos del sueño considerando cinco categorías (duración, alteraciones, problemas en la respiración, fatiga y uso de estimulantes). Se validó por medio del análisis factorial confirmatorio. La fiabilidad se evaluó por la consistencia interna. Se crearon percentiles a través del método LMS (L: asimetría, M: mediana y S: coeficiente de variación). Resultados. Las preguntas 3, 9 y 12 presentaron saturaciones inferiores a 0,40, y las demás preguntas reflejaron saturaciones superiores a 0,41. El valor de adecuación Kaiser-Meyer-Olkin fue 0,749 y la prueba de esfericidad de X2= 4790,09; el porcentaje de la varianza explicó el 62,1 %. El alfa de Cronbach mostró valores entre 0,71 y 0,76. Conclusión. El autoinforme desarrollado para medir los trastornos del sueño en los adolescentes puede ser aplicado de forma válida y confiable en programas de ciencias de la salud, de la educación y del deporte. Se sugiere el uso de percentiles para identificar los patrones normales y/o trastornos del sueño por edad y género.

Tracking of physical fitness in elementary school children: The role of changes in body fat.

OBJECTIVES: The aim of the present study was to examine the stability of physical fitness, and the interrelationships among intra-individual changes in fitness and fatness among elementary school children. METHODS: A longitudinal study was conducted among 372 adolescents (196 boys) and followed up over 3 years (from childhood to adolescence). Physical fitness was estimated using three indicators: cardiorespiratory fitness (through a 9-minute running test), flexibility (through a sit-and-reach test), and muscle resistance (through maximal abdominals in 1 minute). Body adiposity was obtained through triceps and subscapular skinfolds. Somatic maturation was assessed by the peak of height velocity. Kappa and Lin's tests of concordance as well as logistic regression analyses were conducted with P < 0.05 in STATA 15.1. RESULTS: Tracking of physical fitness from childhood to adolescence was moderate for both sexes [boys: kappa = 0.441 (P < 0.001); LCCC = 0.591 (P < 0.001). Girls: kappa = 0.335 (P < 0.001); LCCC = 0.534 (P < 0.001)]. A larger increment in body fat was associated with a higher likelihood to decrease a tertile in physical fitness among boys [OR: 4.17 (95% CI: 1.31-13.22)] and with a lower likelihood to increase a tertile in physical fitness among both sexes [boys: OR = 0.25 (95% CI: 0.09-0.67); girls: OR: 0.37 (95% CI: 0.15-0.92)]. CONCLUSIONS: Health-related physical fitness has moderate tracking from childhood to adolescence. Increases in body adiposity from childhood to adolescence are associated with a reduction in physical fitness tertile.

Peso, estatura e índice de masa corporal de niños y adolescentes de moderada altitud de Colombia / Weight, height and body mass index of children and adolescents living at moderate altitude in Colombia

Introducción. Existe preocupación progresiva por estudiar el crecimiento físico de diversas regiones del mundo, aunque no se considera la altitud como factor de ajuste. Objetivos. Comparar variables de crecimiento físico y patrones de índice de masa corporal (IMC) con la referencia del Centro para el Control y Prevención de Enfermedades 2012 (CDC según siglas en inglés) y desarrollar percentiles para niños y adolescentes. Metodología. Se investigaron escolares de moderada altitud de Bogotá (Colombia). Se evaluó el peso, la estatura y se calculó el IMC. Las variables antropométricas fueron comparadas con referencia al CDC-2012, Brasil, Perú y Argentina. Se construyeron curvas por el método LMS (least-mean-square algorithm). Resultados. Se estudió a 2241 escolares (1159 mujeres), entre 6,0 y 17,9 años. No hubo diferencias significativas en el peso e IMC entre 6 y 8 años con relación al CDC-2012; sin embargo, desde los 9 a 17 años, esta muestra evidenció valores inferiores de peso e IMC en relación con el CDC-2012. En la estatura, en ambos sexos, se mostraron valores inferiores del CDC-2012. Las comparaciones con las curvas regionales de Argentina, Perú y Brasil fueron relativamente similares, excepto en el IMC en mujeres, que presentron valores inferiores desde 13 a 17 años. Conclusión. Las variables de crecimiento de los escolares fueron inferiores con referencia al CDC-2012. Hubo ligeras discrepancias en el crecimiento físico y en el IMC con las curvas de Argentina, Brasil y Perú. Se construyeron curvas para evaluar el crecimiento y el IMC de escolares de moderada altitud de Colombia.

Introduction. There is increasing concern over the study of physical growth in different regions of the world, although altitude is not considered an adjustment factor. Objectives. Compare physical growth variables and body mass index (BMI) patterns with the Centers for Disease Control and Prevention (CDC) 2012 reference data and develop percentiles for children and adolescents. Methodology. School children living at moderate altitude in Bogotá (Colombia) were studied. Their weight and height were evaluated and their BMI was calculated. Anthropometric variables were compared against reference data of the CDC-2012, Brazil, Peru and Argentina. Curves were constructed using the least mean square (LMS) method. Results. A total of 2241 school children (1159 girls) aged 6.0 to 17.9 years were included. There were no significant differences in weight and BMI in 6 to 8 year-olds relative to CDC-2012 reference data; in 9 to 17 year-old children, however, this sample evidenced lower values in terms of weight and BMI as compared to those of the CDC-2012. As far as height is concerned, in both sexes, values were lower than those of the CDC-2012. Comparisons against the regional curves of Argentina, Peru and Brazil yielded relatively similar results, with the exception of girls' BMI, as 13 to 17 year-old girls exhibited lower values. Conclusion. Growth variables of school children were lower relative to the CDC-2012 reference data. There were slight discrepancies in physical growth and BMI in relation to the curves of Argentina, Peru and Brazil. Curves were constructed to evaluate growth in school children living at moderate altitude in Colombia.

Weight, height and body mass index of children and adolescents living at moderate altitude in Colombia. / Peso, estatura e índice de masa corporal de niños y adolescentes de moderada altitud de Colombia.

INTRODUCTION: There is increasing concern over the study of physical growth in different regions of the world, although altitude is not considered an adjustment factor. OBJECTIVES: Compare physical growth variables and body mass index (BMI) patterns with the Centers for Disease Control and Prevention (CDC) 2012 reference data and develop percentiles for children and adolescents. METHODOLOGY: School children living at moderate altitude in Bogotá (Colombia) were studied. Their weight and height were evaluated and their BMI was calculated. Anthropometric variables were compared against reference data of the CDC-2012, Brazil, Peru and Argentina. Curves were constructed using the least mean square (LMS) method. RESULTS: A total of 2241 school children (1159 girls) aged 6.0 to 17.9 years were included. There were no significant differences in weight and BMI in 6 to 8 year-olds relative to CDC-2012 reference data; in 9 to 17 year-old children, however, this sample evidenced lower values in terms of weight and BMI as compared to those of the CDC-2012. As far as height is concerned, in both sexes, values were lower than those of the CDC-2012. Comparisons against the regional curves of Argentina, Peru and Brazil yielded relatively similar results, with the exception of girls' BMI, as 13 to 17 year-old girls exhibited lower values. CONCLUSION: Growth variables of school children were lower relative to the CDC-2012 reference data. There were slight discrepancies in physical growth and BMI in relation to the curves of Argentina, Peru and Brazil. Curves were constructed to evaluate growth in school children living at moderate altitude in Colombia.

INTRODUCCIÓN: Existe preocupación progresiva por estudiar el crecimiento físico de diversas regiones del mundo, aunque no se considera la altitud como factor de ajuste. OBJETIVOS: Comparar variables de crecimiento físico y patrones de índice de masa corporal (IMC) con la referencia del Centro para el Control y Prevención de Enfermedades 2012 (CDC según siglas en inglés) y desarrollar percentiles para niños y adolescentes. METODOLOGÍA: Se investigaron escolares de moderada altitud de Bogotá (Colombia). Se evaluó el peso, la estatura y se calculó el IMC. Las variables antropométricas fueron comparadas con referencia al CDC-2012, Brasil, Perú y Argentina. Se construyeron curvas por el método LMS (least-mean-square algorithm). RESULTADOS: Se estudió a 2241 escolares (1159 mujeres), entre 6,0 y 17,9 años. No hubo diferencias significativas en el peso e IMC entre 6 y 8 años con relación al CDC-2012; sin embargo, desde los 9 a 17 años, esta muestra evidenció valores inferiores de peso e IMC en relación con el CDC-2012. En la estatura, en ambos sexos, se mostraron valores inferiores del CDC-2012. Las comparaciones con las curvas regionales de Argentina, Perú y Brasil fueron relativamente similares, excepto en el IMC en mujeres, que presentron valores inferiores desde 13 a 17 años. CONCLUSIÓN: Las variables de crecimiento de los escolares fueron inferiores con referencia al CDC-2012. Hubo ligeras discrepancias en el crecimiento físico y en el IMC con las curvas de Argentina, Brasil y Perú. Se construyeron curvas para evaluar el crecimiento y el IMC de escolares de moderada altitud de Colombia.

Hand grip strength and maximum peak expiratory flow: determinants of bone mineral density of adolescent students.

BACKGROUND: Maintaining and building healthy bones during the lifetime requires a complicated interaction between a number of physiological and lifestyle factors. Our goal of this study was to analyze the association between hand grip strength and the maximum peak expiratory flow with bone mineral density and content in adolescent students. METHODS: The research team studied 1427 adolescent students of both sexes (750 males and 677 females) between the ages of 11.0 and 18.9 years in the Maule Region of Talca (Chile). Weight, standing height, sitting height, hand grip strength (HGS), and maximum peak expiratory flow (PEF) were measured. Furthermore, bone mineral density (BMD) and total body bone mineral content (BMC) were determined by using the Dual-Energy X-Ray Absorptiometry (DXA). Hand grip strength and PEF were categorized in tertiles (lowest, middle, and highest). Linear regression was performed in steps to analyze the relationship between the variables. Differences between categories were determined through ANOVA. RESULTS: In males, the hand grip strength explained 18-19% of the BMD and 20-23% of the BMC. For the females, the percentage of variation occurred between 12 and 13% of the BMD and 17-18% of the BMC. The variation of PEF for the males was observed as 33% of the BMD and 36% of the BMC. For the females, both the BMD and BMC showed a variation of 19%. The HGS and PEF were divided into three categories (lowest, middle, and highest). In both cases, significant differences occurred in bone density health between the three categories. CONCLUSIONS: In conclusion, the HGS and the PEF related positively to the bone density health of both sexes of adolescent students. The adolescents with poor values for hand grip strength and expiratory flow showed reduced values of BMD and BMC for the total body. Furthermore, the PEF had a greater influence on bone density health with respect to the HGS of the adolescents of both sexes.

Reference standards to assess physical fitness of children and adolescents of Brazil: an approach to the students of the Lake Itaipú region-Brazil.

BACKGROUND: The importance of assessing body fat variables and physical fitness tests plays an important role in monitoring the level of activity and physical fitness of the general population. The objective of this study was to develop reference norms to evaluate the physical fitness aptitudes of children and adolescents based on age and sex from the lake region of Itaipú, Brazil. METHODS: A descriptive cross-sectional study was carried out with 5,962 students (2,938 males and 3,024 females) with an age range of 6.0 and 17.9 years. Weight (kg), height (cm), and triceps (mm), and sub-scapular skinfolds (mm) were measured. Body Mass Index (BMI kg/m2) was calculated. To evaluate the four physical fitness aptitude dimensions (morphological, muscular strength, flexibility, and cardio-respiratory), the following physical education tests were given to the students: sit-and-reach (cm), push-ups (rep), standing long jump (cm), and 20-m shuttle run (m). RESULTS AND DISCUSSION: Females showed greater flexibility in the sit-and-reach test and greater body fat than the males. No differences were found in BMI. Percentiles were created for the four components for the physical fitness aptitudes, BMI, and skinfolds by using the LMS method based on age and sex. The proposed reference values may be used for detecting talents and promoting health in children and adolescents.

Desarrollo de ecuaciones y propuesta de valores referenciales para estimar la masa grasa de niños y adolescentes chilenos / Development of equations and proposed reference values to estimate body fat mass among Chilean children and adolescents

Introducción. La evaluación de la composición corporal es relevante para determinar el estado nutricional e identificar posibles riesgos para la salud. Objetivo. a) Desarrollar ecuaciones de regresión para predecir la masa grasa (MG) utilizando como método de referencia la absorciometría de rayos X de doble energía; b) proponer valores referenciales de MG en función de la edad cronológica y biológica para niños y adolescentes chilenos. Metodología. Estudio transversal en niños y adolescentes de 5,0 a 18,9 años de la región del Maule (Chile). La muestra fue conformada de forma probabilística (estratificada) por 3593 sujetos. Se evaluó el peso, estatura de pie, estatura sentada y circunferencia de la cintura. Se calculó el índice de masa corporal y los años de pico de velocidad del crecimiento (APVC). La composición corporal (MG, masa libre de grasa, masa ósea y porcentaje de grasa) fueron determinados por medio del escaneo de absorciometría de rayos X de doble energía. Resultados. Los APVC (edad biológica) se presentaron en los hombres a los 14,9 ± 0,9 APVC y, en las mujeres, a los 11,5 ± 0,7 APVC. Se generaron ecuaciones para estimar la MG para hombres y mujeres, utilizando como predictores la edad cronológica, APVC y circunferencia de cintura. Se desarrollaron percentiles para evaluar la MG por absorciometría de rayos X de doble energía y por ecuaciones de regresión. Conclusión. Las ecuaciones mostraron aceptabilidad para determinar la MG; además, se han propuesto valores referenciales para evaluar la MG en función de la edad cronológica y biológica.

Introduction. The assessment of body composition is relevant to establish nutritional status and identify potential health risks. Objective. a) To develop regression equations to predict fat mass (FM) using a dual-energy X-ray absorptiometry as reference method; b) to propose reference FM values based on chronological and biological age for Chilean children and adolescents. Methodology. Cross-sectional study in children and adolescents aged 5.0 to 18.9 years from the Maule Region (Chile). The sample was made up of 3593 subjects in a probabilistic fashion (stratified). Subjects' weight, standing height, sitting height, and waist circumference were assessed. Body mass index and age at peak development velocity (APGV) were estimated. Body composition (FM, fat-free mass, bone mass, and fat percentage) were established based on a dual-energy X-ray absorptiometry scan. Results. APGV (biological age) was 14.9 ± 0.9 years among boys and 11.5 ± 0.7 among girls. Equations were developed to estimate FM among boys and girls using chronological age, APGV, and waist circumference as predictors. Percentiles were estimated to assess FM by dual-energy X-ray absorptiometry and regression equations. Conclusion. Equations were acceptable to establish FM; in addition, reference values were proposed to assess FM based on chronological and biological age.

Development of equations and proposed reference values to estimate body fat mass among Chilean children and adolescents. / Desarrollo de ecuaciones y propuesta de valores referenciales para estimar la masa grasa de niños y adolescentes chilenos.

INTRODUCTION: The assessment of body composition is relevant to establish nutritional status and identify potential health risks. OBJETIVE: a) To develop regression equations to predict fat mass (FM) using a dual-energy X-ray absorptiometry as reference method; b) to propose reference FM values based on chronological and biological age for Chilean children and adolescents. METHODOLOGY: Cross-sectional study in children and adolescents aged 5.0 to 18.9 years from the Maule Region (Chile). The sample was made up of 3593 subjects in a probabilistic fashion (stratified). Subjects' weight, standing height, sitting height, and waist circumference were assessed. Body mass index and age at peak development velocity (APGV) were estimated. Body composition (FM, fat-free mass, bone mass, and fat percentage) were established based on a dual-energy X-ray absorptiometry scan. RESULTS: APGV (biological age) was 14.9 ± 0.9 years among boys and 11.5 ± 0.7 among girls. Equations were developed to estimate FM among boys and girls using chronological age, APGV, and waist circumference as predictors. Percentiles were estimated to assess FM by dual-energy X-ray absorptiometry and regression equations. CONCLUSION: Equations were acceptable to establish FM; in addition, reference values were proposed to assess FM based on chronological and biological age.

INTRODUCCIÓN: La evaluación de la composición corporal es relevante para determinar el estado nutricional e identificar posibles riesgos para la salud. OBJETIVO: a) Desarrollar ecuaciones de regresión para predecir la masa grasa (MG) utilizando como método de referencia la absorciometría de rayos X de doble energía; b) proponer valores referenciales de MG en función de la edad cronológica y biológica para niños y adolescentes chilenos. Metodología. Estudio transversal en niños y adolescentes de 5,0 a 18,9 años de la región del Maule (Chile). La muestra fue conformada de forma probabilística (estratificada) por 3593 sujetos. Se evaluó el peso, estatura de pie, estatura sentada y circunferencia de la cintura. Se calculó el índice de masa corporal y los años de pico de velocidad del crecimiento (APVC). La composición corporal (MG, masa libre de grasa, masa ósea y porcentaje de grasa) fueron determinados por medio del escaneo de absorciometría de rayos X de doble energía. RESULTADOS: Los APVC (edad biológica) se presentaron en los hombres a los 14,9 ± 0,9 APVC y, en las mujeres, a los 11,5 ± 0,7 APVC. Se generaron ecuaciones para estimar la MG para hombres y mujeres, utilizando como predictores la edad cronológica, APVC y circunferencia de cintura. Se desarrollaron percentiles para evaluar la MG por absorciometría de rayos X de doble energía y por ecuaciones de regresión. CONCLUSIÓN: Las ecuaciones mostraron aceptabilidad para determinar la MG; además, se han propuesto valores referenciales para evaluar la MG en función de la edad cronológica y biológica.

Linear and nonlinear relationships between body mass index and physical fitness in Brazilian children and adolescents.

OBJECTIVES: The purpose of this study was to evaluate the linear and curvilinear relationship between body mass index (BMI) and physical fitness in children and adolescents. METHODS: Participants were 4567 (2505 girls) children aged 6-16 years. Weight and height were measured and BMI was calculated and adjusted for age and sex using WHO z-scores. Physical fitness was evaluated with the following tests: Yo-Yo test, standing long jump, seated 2-kg medicine ball throw, and 20-m dash. Participants were grouped into two groups according to their maturity status, estimated as years from peak height velocity. Associations were determined with linear and nonlinear quadratic regression models. RESULTS: The nonlinear quadratic regression coefficient was significant for the 20-m dash among girls of both maturity status levels, and in maturity status level 1 boys; for the standing long jump among boys of both maturity status levels, and in maturity status level 1 girls. The Yo-Yo test was only significant for maturity status level 1 boys. For the medicine ball throw, the linear regression coefficient was significant for both maturity status levels in both sexes. Almost all physical fitness items were observed to have meaningfully large nonlinear relationships with BMIz, but they were not all significant due to the small sample size, especially in maturity status level 2. CONCLUSION: The association between BMI and physical fitness is nonlinear in the majority of its components, and those with lower and higher BMI had poorer fitness.

Secular trends of physical growth and abdominal adiposity of school children and adolescents living at a moderate altitude in Peru.

OBJECTIVE: Identify changes in physical growth and abdominal adiposity at an interval of 14 years in children and adolescents living at a moderate altitude in Peru. MATERIALS AND METHODS: The data comes from two cross-sectional studies carried out in the city of Arequipa, Peru, located at a moderate altitude of 2,320 meters. In 2001, 473 males and 482 females were assessed, and in 2015, 432 males and 403 females between 6.0 and 12.9 years old were evaluated. Data were collected in public state schools and measured using the anthropometric variables for weight, height, and waist circumference. Body mass index (BMI) was calculated according to age and sex. RESULTS: Positive trends for weight were identified for both males and females at all ages (p < .001). For height, significant increases were observed in males for all ages. No significant increases (p > .05) occurred in height for females between the ages of 6 and 8 years. However, commencing at age 9 until 12 years, females showed positive and significant increases (p < .001) in height. In 2015, BMI and waist circumference increased significantly for both sexes at all ages. DISCUSSION: Between 2001 and 2015, positive trends in physical growth and abdominal adiposity were identified for children and adolescents living in Arequipa, Peru. These changes may be associated with the rapid economic development in the country.

Accuracy of Body Mass Index Cutoffs for Classifying Obesity in Chilean Children and Adolescents.

OBJECTIVE: To determine the accuracy of two international Body Mass Index (BMI) cut-offs for classifying obesity compared to the percentage of fat mass (%FM) assessed by Dual-Energy X-ray Absorptiometry (DXA) in a Chilean sample of children and adolescents; MATERIAL AND METHODS: The subjects studied included 280 children and adolescents (125 girls and 155 boys) aged 8 to 17 years. Weight and height were measured. The BMI was calculated. Two international references (IOFT and WHO) were used as cut-off points. The %FM was assessed by DXA. The receiver operating characteristic (ROC) curve was used to assess the performance of BMI in detecting obesity on the basis of %FM; RESULTS: A high correlation was observed between the %FM measured by the DXA and the Z-scores of IOTF and WHO scores in the Chilean adolescents separated by sex (r = 0.78-0.80). Differences occurred in both references (IOFT and WHO) in relation to the criteria (p < 0.001). Both references demonstrated a good ability to predict sensitivity (between 84% and 93%) and specificity (between 83% and 88%) in both sexes of children and adolescents; CONCLUSIONS: A high correlation was observed between the Z-score of the BMI with the percentage of fat determined by the DXA. Despite this, the classifications using the different BMI cut-off points showed discrepancies. This suggests that the cut-off points selected to predict obesity in this sample should be viewed with caution.

Improving Sprint Performance in Soccer: Effectiveness of Jump Squat and Olympic Push Press Exercises.

Training at the optimum power load (OPL) is an effective way to improve neuromuscular abilities of highly trained athletes. The purpose of this study was to test the effects of training using the jump squat (JS) or Olympic push-press (OPP) exercises at the OPL during a short-term preseason on speed-power related abilities in high-level under-20 soccer players. The players were divided into two training groups: JS group (JSG) and OPP group (OPPG). Both groups undertook 12 power-oriented sessions, using solely JS or OPP exercises. Pre- and post-6 weeks of training, athletes performed squat jump (SJ), countermovement jump (CMJ), sprinting speed (5, 10, 20 and 30 m), change of direction (COD) and speed tests. To calculate the transfer effect coefficient (TEC) between JS and MPP OPP and the speed in 5, 10, 20, and 30 m, the ratio between the result gain (effect size [ES]) in the untrained exercise and result gain in the trained exercise was calculated. Magnitude based inference and ES were used to test the meaningful effects. The TEC between JS and VEL 5, 10, 20, and 30 m ranged from 0.77 to 1.29, while the only TEC which could be calculated between OPP and VEL 5 was rather low (0.2). In addition, the training effects of JS on jumping and speed related abilities were superior (ES ranging from small to large) to those caused by OPP (trivial ES). To conclude, the JS exercise is superior to the OPP for improving speed-power abilities in elite young soccer players.

Reproductibilidad de un cuestionario que valora la actividad física en adolescentes escolares de altitud / Reproducibility of a questionnaire that valúes physical activity in school adolescents altitude

Objetivo: Analizar la fiabilidad de un cuestionario que valora la Actividad Física en una muestra de escolares adolescentes que viven a elevada altitud por medio de consistencia interna y test re-test. Materiales y métodos: Descriptivo-transversal (Survey). Institución: Universidad Nacional del Altiplano (Puno, Perú). Adolescentes escolares de 12 a 17 años. Fueron seleccionados de forma sistemática 109 escolares de ambos sexos. Se valoró las medidas antropométricas de peso, estatura, estatura sentada y circunferencia del abdomen. Además se aplicó un cuestionario de actividad física con 11 preguntas (test y re-test) con un intervalo de 7 días. Valoración de la capacidad de reproductibilidad por consistencia interna y estabilidad. Resultados: Los valores de alpha de Cronbach (consistencia interna) mostraron valores de 0,73 a 0,77 para ambos sexos. El Error Técnico de Medida (ETM) fue de 0,50 a 1,61% y el coeficiente de correlación de Spearman osciló entre 0,91 y 0,95. Conclusión: El cuestionario de actividad física muestra altos valores de confiabilidad, tanto en su consistencia interna como en la estabilidad de las medidas.

Objective: To analyze the reliability of a questionnaire to assess physical activity in a sample of school adolescents living at high altitude through internal consistency and test re-test. Materials and methods: Descriptive, transversal (Survey). Universidad Nacional del Altiplano (Puno, Peru). School Teens 12 to 17 years. There were systematically selected 109 students of both sexes. We evaluated anthropometric measurements of weight, height, sitting height and circumference of the abdomen. In addition we applied a physical activity questionnaire with 11 questions (test and re-test) with an interval of 7 days. capacity rating for internal consistency, reproducibility and stability. Results: Cronbach's alpha values (internal consistency) showed values from 0.73 to 0.77 for both sexes. Measuring technical error (SEM) was from 0.50 to 1.61% and the Spearman correlation coefficient ranges from 0.91 to 0.95. Conclusion: The physical activity questionnaire shows high values of reliability, consistency both internally and in the stability of the measures.

Association between health-related physical fitness and body mass index status in children.

The purpose of this study was to investigate the association between body mass index (BMI) status and physical performance in Brazilian children. The analyzed sample was composed of 978 children of both sexes (518 boys and 460 girls), aged 7 to 11 years. BMI and skinfolds were measured, and three motor tests were applied (flexibility, cardiorespiratory fitness, and muscular strength/endurance). In both sexes, overweight/obese children presented poor performance in all motor tests, except flexibility. In general, overweight/obese children have an increased odds ratio (OR) to present poor physical performance (boys: OR = 3.64 for cardiorespiratory fitness, OR = 1.94 for muscular strength/endurance, OR = 1.52 for flexibility; girls: OR = 5.03 for cardiorespiratory fitness and OR = 2.62 for muscular strength/endurance). In conclusion, for both sexes, a poor physical performance in the tests measuring cardiorespiratory fitness and muscular strength/ endurance was associated with the presence of overweight/obesity.