[Validity of body mass index and fat mass index as indicators of overweight status in Spanish adolescents: Esccola Study]. / Validez de los índices de masa corporal y de masa grasa como indicadores de sobrepeso en adolescentes españoles: estudio Esccola.

BACKGROUND AND OBJECTIVES: To determine the accuracy of body mass index (BMI), fat mass index (FMI) and fat-free mass index (FFMI) to find cut-off points related to overweight in adolescents aged 12-18 years. SUBJECTS AND METHOD: 150 adolescents were assessed (75 boys aged 14.81+/-1.86yr, height 168.8+/-8.8cm, weight 65.84+/-16kg and BMI 22.89+/-4.4kg x m(2), and 75 girls aged 14.88+/-1.94yr, height 159.4+/-7.6cm, weight 54.77+/-9.54kg and BMI 21.48+/-3.1kg x m(2)). Body composition was measured by using the deuterium dilution technique with an isotope ratio mass spectrometer and fat free mass hydration constants were applied. Taylor's age-related overweight classification was applied and receiver operating characteristic (ROC) curves analyses were performed. Areas under curve were calculated for every index (BMI, FMI and FFMI). Sensitivity and specificity values of BMI and FMI to diagnose overweight were evaluated. RESULTS: Among boys, predictive positive values for BMI were 78.1% and 89.2% for FMI; predictive positive values in girls was 34.8% for BMI and 81.4% for FMI. Predictive negative values were 81.4% and 100% in boys and 98.1% and 100% in girls for BMI and FMI. Areas under curve of FMI for boys (0.988, 95%CI: 0.930-0.998) and girls (0.996, 95%CI: 0.943-1.000) showed high accuracy for overweight diagnose. Cutoff points of 4.58kg x m(2) in boys and 7.76kg x m(2) in girls for FMI and 23.07kg x m(2) in boys and 23.18kg x m(2) in girls for BMI had high sensitivity and specificity as indicators of overweight classification. CONCLUSIONS: FMI showed high accuracy for overweight screening. Thus, our cut-off points may be useful as a tool to surveillance children's overweight on clinical and epidemiologic settings.

Body composition changes after sport detraining period / Cambios de la composición corporal tras un periodo de desentrenamiento deportivo

Introduction: The infl uence of exercise in trained subjects has beneficial effects in the physical fi tness and body composition; however, detraining has an unfavorable effect in all of them. Objective: The current study was designed to ascertain the infl uence of a six week-detraining period on body composition in both well-trained young soccer players (GE, n = 43) and sedentary male adolescents (GC, n = 10). Methods: Forty-three well-trained soccer players and ten sedentary adolescents accepted to participate in the study. Body composition measurements included fat mass and skeletal muscle mass (SMM), which were estimated by anthropometry. In addition, total body water (TBW), intracellular water (ICW) and extracellular water (ECW) were assessed by bioelectrical impedance analysis (BIA) at the end of training and after detraining periods. Results: After the six-week-detraining period, signifi cant increments were found in TBW (35.5 ± 5.2 vs.36.7 ± 4.9 kg; p < 0.001), ICW (14.2 ± 1.8 vs. 14.8 ± 1.6 kg; p < 0.001) and ECW (21.5 ± 3.6 vs. 22.0 ± 3.4 kg; p < 0.001) in soccer players. Conversely, no changes were observed in ECW/TBW (0.4 ± 0.02 vs. 0.4 ± 0.02; p > 0.05) and ICW/TBW (0.6 ± 0.02 vs. 0.597 ± 0.02; p > 0.05) ratios. Finally, fat mass was significantly increased (8.6 ± 3.2 vs. 8.95 ± 3.1 kg; p < 0.01) in the detrained group. No signifi cant changes were found in SMM (21.2 ± 2.5 vs. 22.22 ± 2.8 kg, p > 0.05). Conclusions: After a six-week detraining period, body composition changed signifi cantly in well-trained adolescents. The main fi nding of this study was that increments of TBW and water distribution were observed in the soccer group, which refl ects an increase of fat free mass compartment. The physiological importance of this miss-adaptation needs to be elucidated in future research. Further studies on this topic are still required to assess its impact on physical performance.

Reliability and Validity of the PAQ-C Questionnaire to Assess Physical Activity in Children.

BACKGROUND: Physical activity (PA) assessment by questionnaire is a cornerstone in the field of sport epidemiology studies. The Physical Activity Questionnaire for Children (PAQ-C) has been used widely to assess PA in healthy school populations. The aim of this study was to evaluate the reliability and validity of the PAQ-C questionnaire in Spanish children using triaxial accelerometry as criterion. METHODS: Eighty-three (N = 46 boys, N = 37 girls) healthy children (age 10.98 ± 1.17 years, body mass index 19.48 ± 3.51 kg/m(2) ) were volunteers and completed the PAQ-C twice and wore an accelerometer for 8 consecutive days. Reliability was analyzed by the intraclass correlation coefficient (ICC) and the internal consistency by the Cronbach's α coefficient. The PAQ-C was compared against total PA and moderate to vigorous PA (MVPA) obtained by accelerometry. RESULTS: Test-retest reliability showed an ICC = 0.96 for the final score of PAQ-C. Small differences between first and second questionnaire administration were detected. Few and low correlations (rho = 0.228-0.278, all ps < .05) were observed between PAQ-C and accelerometry. The highest correlation was observed for item 9 (rho = 0.311, p < .01). CONCLUSIONS: PAQ-C had a high reliability but a questionable validity for assessing total PA and MVPA in Spanish children. Therefore, PA measurement in children should not be limited only to self-report measurements.

[Physical activity and accelerometer; methodological training, recommendations and movement patterns in school]. / Actividad física y acelerometría; orientaciones metodológicas, recomendaciones y patrones.

INTRODUCTION: Over the last years, the use of accelerometers has become relevant to quantify physical activity among youth. Methods used with accelerometers might modify the results and the possibility to compare different papers. These devices have been proved to be effective and valid quantifying long periods of physical activity compared to other methods. OBJECTIVE: To show methodological criteria regarding physical activity assessed by accelerometry with schoolars. METHODOLOGY: It was conducted a review of the literature related to accelerometers and scholar-aged subjects at PubMed from January 2002 to August 2013, selecting 133 papers. RESULTS: As far as it is shown, it appears to be some tendencies related to the choice of attachment of the device, wearing time and a shorter epoch-length; however, it has been found a wide variability regarding the model of accelerometer and cutoff points used. DISCUSSION AND CONCLUSIONS: The different criterion used makes it difficult to compare methodological aspects among studies in spite of some papers carried out similar methods.

Introducción: En los últimos años, ha cobrado especial importancia el empleo de acelerómetros para valorar la actividad física de niños y jóvenes. La metodología utilizada en el uso de la acelerometría determina los resultados obtenidos y condiciona la posibilidad de comparar diferentes estudios. Objetivo: El objetivo de esta revisión, se centra en aspectos metodológicos relacionados con la evaluación de la actividad física en escolares utilizando la acelerometría. Metodología: Se realizó una revisión de la literatura de los artículos incluidos en las bases de datos Medline/ Pubmed y Scielo que utilizaran acelerómetros con participantes en edad escolar entre Enero de 2002 y Agosto de 2013, seleccionándose 133 artículos científicos. Resultados: Parece existir un cierto consenso respecto a la elección del lugar de colocación, el tiempo de registro y el empleo de epochs cada vez más reducidos; sin embargo, se encuentra una gran variabilidad respecto al modelo de acelerómetro empleado y los puntos de corte seleccionados. Discusión y Conclusiones: Los diferentes criterios empleados, dificultan la comparación en la metodología empleada entre estudios a pesar de que existan ciertos puntos en común entre ellos.

Skeletal muscle triglycerides, diacylglycerols, and ceramides in insulin resistance: another paradox in endurance-trained athletes?

OBJECTIVE: Chronic exercise and obesity both increase intramyocellular triglycerides (IMTGs) despite having opposing effects on insulin sensitivity. We hypothesized that chronically exercise-trained muscle would be characterized by lower skeletal muscle diacylglycerols (DAGs) and ceramides despite higher IMTGs and would account for its higher insulin sensitivity. We also hypothesized that the expression of key skeletal muscle proteins involved in lipid droplet hydrolysis, DAG formation, and fatty-acid partitioning and oxidation would be associated with the lipotoxic phenotype. RESEARCH DESIGN AND METHODS: A total of 14 normal-weight, endurance-trained athletes (NWA group) and 7 normal-weight sedentary (NWS group) and 21 obese sedentary (OBS group) volunteers were studied. Insulin sensitivity was assessed by glucose clamps. IMTGs, DAGs, ceramides, and protein expression were measured in muscle biopsies. RESULTS: DAG content in the NWA group was approximately twofold higher than in the OBS group and ~50% higher than in the NWS group, corresponding to higher insulin sensitivity. While certain DAG moieties clearly were associated with better insulin sensitivity, other species were not. Ceramide content was higher in insulin-resistant obese muscle. The expression of OXPAT/perilipin-5, adipose triglyceride lipase, and stearoyl-CoA desaturase protein was higher in the NWA group, corresponding to a higher mitochondrial content, proportion of type 1 myocytes, IMTGs, DAGs, and insulin sensitivity. CONCLUSIONS: Total myocellular DAGs were markedly higher in highly trained athletes, corresponding with higher insulin sensitivity, and suggest a more complex role for DAGs in insulin action. Our data also provide additional evidence in humans linking ceramides to insulin resistance. Finally, this study provides novel evidence supporting a role for specific skeletal muscle proteins involved in intramyocellular lipids, mitochondrial oxidative capacity, and insulin resistance.

Estimaciones de la masa grasa y la masa muscular por métodos antropométricos y de bioimpedancia eléctrica / Assessment of fat mass and skeletal muscle mass by means of conventional anthropometry and bioelectrical impedance analysis

Determinar la masa grasa y sus diferencias estimadas por técnicas de antropometría y bioimpedancia eléctrica de cuerpo entero, así como presentar datos de masa muscular esquelética en jóvenes en edad escolar, por métodos antropométricos. Método: Se ha procedido a la valoración de la composición corporal de 75 niños y 75 niñas de entre 12 y 18 años, mediante técnicas antropométricas y de bioimpedancia eléctrica de cuerpo entero para estimar la masa grasa (Slaughter y Houtkooper, respectivamente), así como la masa muscular esquelética (Poortmans). El análisis estadístico consistió en un estudio comparativo entre métodos que se realizó mediante la prueba de la t de Student, un estudio correlacional mediante el coeficiente de correlación de Spearman, así como un estudio de concordancia entre métodos mediante los procedimientos de Bland-Altman. Resultados: No existen diferencias significativas de la masa grasa determinada por ambos métodos (p > 0.05). Existen diferencias estadísticas en la masa muscular esquelética entre niños y niñas (p < 0.05). El estudio de concordancia muestra pequeñas diferencias entre métodos con errores proporcionales para el grupo de niños, no así en niñas,y con muy amplios límites de concordancia entre métodos. Conclusiones: En general, se puede concluir que la metodología antropométrica y de bioimpedancia eléctrica para la estimación de la composición corporal no son intercambiables para valoraciones longitudinales, en niños en edad escolar de 12 a 18 años, y aunque se observan pequeñas diferencias, existe un efecto de error proporcional entre método...