Association between sedentary behavior and bone mass in adolescents.

The effects of sedentary behavior on adolescents' bone health are controversial because, even in normal weight individuals, the excessive time spent in some specific types of these behaviors appears to have no negative effect on bone health. PURPOSE: To analyze the relationship between sedentary behaviors and bone mass in adolescents. METHODS: One hundred four adolescent boys and girls, aged 10 to 14 years, were divided into normal weight and overweight according to weight status. Specific sedentary behaviors (time spent on the Internet for school and non-school purposes, using the computer, watching television, and playing videogames) were assessed by questionnaire, and the total sedentary behavior time by accelerometry. Bone parameters were collected using X-ray absorptiometry, using total and lumbar bone mineral density (BMD) and total and lumbar bone mineral content (BMC) values. RESULTS: In both groups, the time spent on the Internet for non-school purposes was positively correlated to the total and lumbar BMD. Also, while in the overweight group, the time spent using the computer was negatively correlated to lumbar BMD, and the time spent on the Internet for non-school purposes was positively correlated to the total and lumbar BMC, and in the normal weight group, the time spent on the Internet for non-school purposes was positively correlated to lumbar BMC. CONCLUSIONS: Adolescents who spend more time in sedentary behavior, especially using the Internet for non-school purposes, have higher BMD and BMC, while normal weight adolescents who spend more time on the computer have lower BMD.

Aptidão cardiorrespiratória em adolescentes / Aptitud cardiorrespiratoria en adolescentes / Cardiorespiratory fitness in adolescents

Objetivo. O presente estudo tem como objetivo verificar as prevalências de aptidão cardiorrespiratória e a sua associação com aspectos sociodemográficos e composição corporal em adolescentes. Método. Estudo transversal realizado com 601 escolares (14‐17 anos de idade) da rede de ensino pública do Meio‐Oeste catarinense. A aptidão cardiorrespiratória foi mensurada pelo teste de vai‐e‐vem de 20 metros. Foram coletadas informações referentes ao sexo, idade e nível econômico, massa corporal, estatura, perímetro da cintura e dobras cutâneas. As análises estatísticas (U de Mann‐Whitney, qui‐quadrado e regressão logística) foram realizadas, com nível de significância de 5%. Resultados. A prevalência de aptidão cardiorrespiratória inadequada foi de 61.1%, sendo maior nos rapazes e naqueles com composição corporal inadequada. A composição corporal inadequada esteve associada à aptidão cardiorrespiratória inadequada, mesmo após ajustada pelo sexo, idade e nível econômico. Conclusão. Conclui‐se que a maioria dos adolescentes apresentam níveis inadequados de aptidão cardiorrespiratória, e a associação entre composição corporal e aptidão cardiorrespiratória inadequadas independe dos aspectos sociodemográficos dos adolescentes (AU)

Objetivo. El presente estudio tuvo como objetivo verificar las prevalencias de aptitud cardiorrespiratoria y su asociación con aspectos sociodemográficos y composición corporal en adolescentes. Método. Estudio transversal realizado con 601 escolares (14‐17 años) de la red de educación pública del Medio‐Oeste catarinense. La aptitud cardiorrespiratoria fue medida por el test de carrera de ida y vuelta de 20 metros. Fueron recogidas informaciones referentes al sexo, edad y nivel económico, masa corporal, estatura, perímetro de la cintura y pliegues cutáneos. Los análisis estadísticos (U de Mann‐Whitney, Chi cuadrado y regresión logística) fueron realizados, con nivel de significación del 5%. Resultados. La prevalencia de aptitud cardiorrespiratoria inadecuada fue de 61.1%, siendo mayor en los muchachos y en aquellos con composición corporal inadecuada. La composición corporal inadecuada estuvo asociada a la aptitud cardiorrespiratoria inadecuada, incluso después de ajustarla por el sexo, edad y nivel económico. Conclusión. Se concluye que la mayoría de los adolescentes presentan niveles inadecuados de aptitud cardiorrespiratoria y la asociación entre composición corporal y aptitud cardiorrespiratoria inadecuadas no depende de los aspectos sociodemográficos de los adolescentes (AU)

Objective. The aim of this study was to determine the prevalence of cardiorespiratory fitness and its association with sociodemographic characteristics and body composition in adolescents. Method. This is a cross‐sectional study with 601 students (14‐17 years) of the public school system in the Mid‐western state of Santa Catarina. Cardiorespiratory fitness was measured by the 20‐meter back‐and‐forth test. Information on gender, age and economic status, body weight, height, waist circumference and skinfold thickness were collected. Statistical analysis (Mann‐Whitney U, chi‐square and logistic regression tests) was performed, with 5% significance level. Results. The prevalence of inadequate cardiorespiratory fitness was 61.1%, being higher in boys and in those with inadequate body composition. Inadequate body composition was associated with poor cardiorespiratory fitness even after adjusted by sex, age and economic status. Conclusion. It was concluded that most adolescents showed inadequate levels of cardiorespiratory fitness and the association between body composition and inadequate cardiorespiratory fitness is independent of sociodemographic characteristics of adolescents (AU)