Relationship between body composition and bone mass in normal-weight and overweight adolescents.

Adolescence is a period characterized by large accumulation of bone mass. Body composition is an important determinant of bone mass. This study aimed to assess the relationship of bone mass with lean mass (LM) and fat mass (FM) in normal-weight and overweight adolescents with consideration of sex, sexual maturation and physical activity covariates. A total of 118 adolescents (60 girls and 58 boys) aged between 10 and 14 years participated in the study. Individuals were classified as normal weight or overweight according to body mass index. Bone mineral density (BMD), bone mineral content (BMC), LM, and FM were measured by dual-energy X-ray absorptiometry. In normal-weight adolescents, LM (ß = 0.725, p < 0.001) and FM (ß = 0.185, p = 0.019) were associated with lumbar spine BMC, whereas in overweight adolescents only LM (ß = 0.736, p < 0.001) was associated with lumbar spine BMC. Furthermore, in the normal-weight group, FM and LM were associated with total body less head BMD (LM, ß = 0.792, p < 0.001; FM, ß = 0.257, p = 0.007) and lumbar spine BMD (LM, ß = 0.553, p < 0.001; FM, ß = 0.199, p < 0.035). In the overweight group, only LM was associated with total body less head BMD (ß = 0.682, p < 0.001) and lumbar spine BMD (ß = 0.528, p < 0.001). LM was the main predictor of bone mass in normal-weight and overweight adolescents. FM was associated with bone mass in normal-weight adolescents only. LM may be considered an important and useful marker in adolescents, when investigating bone health in this population. Activities that promote LM gain to reduce the risk of bone fractures and diseases in adulthood are recommended.

Relationship Between Muscle Strength, Body Composition and Bone Mineral Density in Adolescents.

Adolescence is an important period for the acquisition of bone mass, which can be enhanced by several factors. This study aimed examine the relationships of handgrip strength, free-fat mass, and fat mass with bone mineral density in adolescents. 118 adolescents (60 girls), aged 10 to 14 years, participated in the study. Information on sex, age, handgrip strength, free-fat mass, fat mass and bone mineral density were collected. Multiple linear regression analyses were conducted to examine possible relationships between bone mineral density and handgrip strength, free-fat mass and fat mass. There was a relation between handgrip strength and free-fat mass with bone mineral density in both sexes. Fat mass was correlated with bone mineral density only in girls (r= 0.314, p< 0.014). The final models, adjusted for sexual maturation, included free-fat mass (girls - ß= 0.419, p< 0.001; boys - ß= 0.455; p< 0.001) and handgrip strength (girls - ß= 0.358, p< 0.05; boys - ß= 0.325; p< 0.05) and these variables together explained 51.8% and 62.9% of the variation of bone mineral density, in girls and boys, respectively. Handgrip strength and free-fat mass were positively associated with bone mineral density. A sex-specific difference indicated that higher levels of free-fat mass are of paramount importance for both sexes.

Concordância entre dois critérios de classificação da atividade física e fatores associados em adolescentes / Agreement between two criteria of physical activity classification and associated factors in adolescents

O objetivo deste estudo foianalisar a concordância entre dois critérios de classificação da atividade física (AF) e os respectivos fatores associados. Os participantes foram 2.517 adolescentes amazonenses (14 a 19 anos de idade). O nível de AF e as variáveis independentes (sexo, faixa etária, ano escolar, turno de estudo, renda familiar, escolaridade materna e situação ocupacional) foram coletados por meio de questionário. O coeficiente kappa e a regressão logística binária foram empregados, respectivamente, para analisar a concordância entre as prevalências e os fatores associados aos dois critérios de classificação da AF (300 e 420 minutos/semana). Verificou-se moderada concordância entre os critérios (kappa = 0,58; p< 0,001) para classificação do nível de AF, com diferença de 8,5 pontos percentuais entre as prevalências, sendo que para os 300 e 420 minutos/semana foram classificados como fisicamente ativos 15,5% (IC95% = 14,2-16,7) e 7,0% (IC95% = 6,0-7,0) dos participantes, respectivamente. Os adolescentes do sexo masculino e os que não trabalhavam tiveram mais chances de serem fisicamente ativos em ambos os critérios. Os adolescentes mais novos (14 a 16 anos) tiveram mais chances de serem fisicamente ativos no critério de 300 minutos/semana. O ano escolar, turno de estudo, renda familiar e escolaridade materna não se associaram aos critérios utilizados. A concordância entre os dois critérios de classificação do nível de AF foi moderada e os fatores associados foram semelhantes em ambos os critérios, com exceção da faixa etária.

This study aimed to analyze the agreement between two criteria to classify physical activity (PA), and the respective associated factors.Participants were 2.517 adolescents (aged 14 to 19) from Amazonas. The PA level and the independent variables (sex, age group, school year, school shift, family income, maternal educational level and work) were collected by means of a questionnaire. The kappa coefficient and binary logistic regression were used to analyze the agreement between the prevalence and the associated factors to both criteria (300 and 420 minutes/week of PA), respectively. We found a moderate agreement between the two criteria to classify PA level (kappa = 0.58), with a difference of 8.5 percentage points between the prevalence, considering that for 300 and 420 minutes/week, 15.5% (95%CI = 14.2-16.7) and 7.0% (95%CI = 6.0-7.0) of the participants were classified as physically active, respectively. Male adolescents and those who did not work were more likely to be physically active in both criteria, compared to their peers. Younger adolescents (14 to 16 years) were more likely to be physically active in the criterion of 300 minutes/week. School year, school shift, family income and maternal educational level were not associated to the used criteria. In conclusion, the agreement between two criteria to classify PA level was moderated and the associated factors to sufficient PA were similar in both criteria with an exception for age group.