Mediation effects of lean mass and fat mass on the relationship between body mass index and handgrip strength.

OBJECTIVE: This study aimed to assess the mediation effects of lean mass and fat mass on the relationship between body mass index (BMI) and handgrip strength (HGS) in adolescents. METHOD: The sample included 118 adolescents (60 girls) aged 10-14 years. Body composition, determined from lean mass (LM) and fat mass (FM), was measured by dual-energy x-ray absorptiometry. HGS was measured using a digital dynamometer. Moderate-to-vigorous physical activity and sexual maturation, treated as covariates, were evaluated by accelerometry and pubic hair development, respectively. Spearman correlation and simple mediation analysis were used for statistical analysis. RESULTS: A positive relationship was observed between BMI and HGS (rho = .364, p < .001), BMI and LM (rho = .466, p < .001), LM and HGS (rho = .784, p < .001), BMI and FM (rho = .907, p < .001), and FM and HGS (rho = .291, p = .001). LM was the only significant mediator of the relationship between BMI and HGS. CONCLUSION: Only LM mediated the association between BMI and HGS, almost entirely explaining the relationship. The findings reinforce the need to include LM measurements in routine strength testing. Furthermore, strategies focused on LM development may be promising in preventing low muscle strength in adolescents.

Isolated and combined association of excessive screen time and physical inactivity with negative self-rated health in adolescents.

OBJECTIVE: The aim of this study was to analyze isolated and combined associations of physical inactivity excessive screen time with negative self-rated health, according to sex, among school adolescents. METHODS: In this cross-sectional study conducted with 2,517 adolescents in Amazonas State, participants were asked about their self-rated health with the following question: How do you rate your health? Responses were dichotomized into positive (excellent and good) and negative (regular, bad, and terrible). Information on sex, age group, family income, physical activity, and screen time (watching TV, using a computer, or playing video games) was collected through a self-administered questionnaire. Adolescents simultaneously classified as physically inactive (<60 min/day) and having excessive screen time (>2 h/day) were considered to have two risk factors. Data was analyzed using binary logistic regression. RESULTS: Out of every 10 adolescents, 2 had a negative self-rated health. After adjusting for age and family income, there were no isolated or combined associations between physical inactivity or excessive screen time and negative self-rated health in girls. In boys, negative self-rated health was associated with insufficient levels of physical activity (odds ratio [OR]: 2.39; 95% confidence interval [CI]: 1.03-5.59) and with the accumulation of two risk factors (OR: 1.61; 95%CI 1.10-2.34). CONCLUSIONS: Being insufficiently active and the combination of physical inactivity and excessive screen time become exposure factors to the negative self-rated health of adolescent boys.

Agreement Between Body Mass Index and Body Fat in Adolescents With Different Physical Activity Levels.

Purpose: This study aimed to verify the agreement between body mass index (BMI) and body fat in adolescents with different physical activity (PA) levels. Method: This cross-sectional study collected body fat data in 118 adolescents (aged 10 to 14 years) estimated using air-displacement plethysmography (ADP). Body mass 10 and height were used to calculate BMI. Physical activity levels were measured objectively by accelerometers. Results: For boys with low PA, BMI overestimated body fat values measured by ADP (mean error = -0.42; p = .018) which also occurred in group high PA (mean error = -0.76; p = .001). For girls, BMI underestimated body fat values measured by ADP values in group high PA (mean error = 0.43; p = .001) and low PA (mean error = 0.72; p < .001). Conclusion: It is recommended that researchers and practitioners 15 cautiously interpret BMI results, especially considering that most adolescents do not practice enough PA.

Isolated and combined association of excessive screen time and physical inactivity with negative self-rated health in adolescents / Associação isolada e combinada do tempo de tela excessivo e da inatividade física com autopercepção de saúde negativa em adolescentes

Abstract Objective: The aim of this study was to analyze isolated and combined associations of physical inactivity excessive screen time with negative self-rated health, according to sex, among school adolescents. Methods: In this cross-sectional study conducted with 2,517 adolescents in Amazonas State, participants were asked about their self-rated health with the following question: How do you rate your health? Responses were dichotomized into positive (excellent and good) and negative (regular, bad, and terrible). Information on sex, age group, family income, physical activity, and screen time (watching TV, using a computer, or playing video games) was collected through a self-administered questionnaire. Adolescents simultaneously classified as physically inactive (<60 min/day) and having excessive screen time (>2 h/day) were considered to have two risk factors. Data was analyzed using binary logistic regression. Results: Out of every 10 adolescents, 2 had a negative self-rated health. After adjusting for age and family income, there were no isolated or combined associations between physical inactivity or excessive screen time and negative self-rated health in girls. In boys, negative self-rated health was associated with insufficient levels of physical activity (odds ratio [OR]: 2.39; 95% confidence interval [CI]: 1.03-5.59) and with the accumulation of two risk factors (OR: 1.61; 95%CI 1.10-2.34). Conclusions: Being insufficiently active and the combination of physical inactivity and excessive screen time become exposure factors to the negative self-rated health of adolescent boys.

RESUMO Objetivo: Analisar a associação isolada e combinada do tempo excessivo de tela e inatividade física com a autopercepção negativa de saúde, de acordo com o sexo, em adolescentes estudantes. Métodos: Estudo transversal conduzido em 2.517 adolescentes amazonenses, os quais foram questionados sobre a autopercepção de saúde: "Como você considera a sua saúde?", dicotomizada em positiva (excelente, boa) e negativa (regular, ruim, péssima). Informações sobre sexo, faixa etária, renda familiar, atividade física e tempo excessivo de tela (assistindo TV, usando o computador ou jogando videogame) foram coletadas mediante questionário autoadministrado. Aqueles classificados, simultaneamente, como fisicamente inativos (<60 min/dia) e com tempo excessivo de tela (>2 horas/dia) foram considerados com dois fatores de risco. Os dados foram analisados utilizando-se a regressão logística binária. Resultados: Dois em cada dez adolescentes apresentaram autopercepção negativa de saúde. Após o ajuste pelas variáveis idade e renda familiar, não foram observadas, no sexo feminino, associações da inatividade física e do tempo excessivo de tela, de maneira isolada ou agrupada, com a autopercepção negativa de saúde. No sexo masculino, a percepção negativa de saúde foi associada com os níveis insuficientes de atividade física (odds ratio — OR: 2,39; intervalo de confiança — IC95% 1,03-5,59) e com o acúmulo de dois fatores de risco (OR: 1,61; IC95% 1,10-2,34). Conclusões: Ser insuficientemente ativo e associar a inatividade física com tempo excessivo de tela tornam-se fatores de exposição à percepção negativa em saúde de meninos adolescentes.

Agreement and validity between body fat estimated by skinfold measurement and air displacement plethysmography in adolescents / Concordância e validade entre a gordura corporal estimada por medidas de dobras cutâneas e pletismografia por deslocamento de ar em adolescentes

ABSTRACT Objective: Assess the agreement and validity between relative body fat percentages estimated using anthropometric measurements and air displacement plethysmography (ADP). Methods: A cross-sectional study was conducted on 118 adolescents (60 females) aged 10 to 14 years (x̄=12.19, sd=1.18). Adolescents were classified as eutrophic or with overweight according to body mass index (body weight/height2) (x̄=20,12, sd=3,56). Measurements of skinfold thickness (triceps and medial calf) were collected and used to estimate relative body fat by the Slaughter equation. ADP was used as a reference method for the estimation of relative body fat. Agreement between body fat measurement methods (anthropometry × ADP) was analyzed by the Bland-Altman method. The mean error (ME) was calculated by subtracting the body fat percentage estimated by the Slaughter equation from the body fat percentage estimated by ADP. Validity was tested with the concordance correlation coefficient (CCC). Results: There was no agreement between the methods, regardless of sex and weight status. For boys with overweight (ME = 4.52; p = 0.007), eutrophic girls (ME = 6.37; p < 0.001), and girls with overweight (ME = 5.55; p < 0.001), the Slaughter equation resulted in overestimation of body fat compared with ADP. Skinfold equations did not demonstrate validity when compared with ADP. Conclusion: Slaughter's skinfold equations did not demonstrate agreement and validity compared with ADP in either sex or weight status. Skinfold equations should be used with caution and, whenever possible, in combination with other body composition indicators.

RESUMO Objetivo: Avaliar a concordância e validade entre os percentuais de gordura corporal estimados usando medidas antropométricas e pletismografia por deslocamento de ar (PDA). Métodos: Um estudo transversal foi conduzido em 118 adolescentes (60 meninas) com idade entre 10 e 14 anos (x̄=12,19, dp=1,18). Os adolescentes foram classificados como eutróficos ou com sobrepeso de acordo com o índice de massa corporal (peso/altura2) (x̄=20,12, dp=3,56). Medidas de dobras cutâneas (tríceps e panturrilha medial) foram coletadas e utilizadas para estimar a gordura corporal relativa pela equação de Slaughter. A PDA foi utilizada como método de referência para a estimativa da gordura corporal relativa. A concordância entre os métodos de medida de gordura corporal (antropometria × PDA) foi analisada pelo método de Bland-Altman. O erro médio (EM) foi calculado subtraindo o percentual de gordura corporal estimado pela equação de Slaughter do percentual de gordura corporal estimado pela PDA. A validade foi testada com o coeficiente de correlação de concordância (CCC). Resultados: Não houve concordância entre os métodos, independente do sexo e status de peso. Para meninos com excesso de peso (EM = 4,52; p = 0,007), meninas eutróficas (EM = 6,37; p < 0,001) e meninas com excesso de peso (EM = 5,55; p < 0,001), a equação de Slaughter resultou em superestimação da gordura corporal comparada com PDA. As equações de dobras cutâneas não demonstraram validade quando comparadas ao PDA. Conclusão: As equações de dobras cutâneas de Slaughter não demonstraram concordância e validade em comparação com PDA em ambos os sexos ou status de peso. As equações de dobras cutâneas devem ser utilizadas com cautela e, sempre que possível, acompanhada de outros indicadores de composição corporal.

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.

High waist-to-height ratio and associated factors in adolescents from a city in Southern Brazil: a cross-sectional study / Razão cintura-estatura elevada e fatores associados em adolescentes de uma cidade do Sul do Brasil: um estudo transversal

ABSTRACT Objective: To verify the prevalence of abdominal obesity with the waist-to-height ratio (WHtR) and associated factors in adolescents from a city in Southern Brazil. Methods: A total of 960 adolescents (494 boys) aged 15-18 years old participated in this study. The dependent variable was WHtR; independent variables were self-reported age, economic level, sexual maturation, physical activity level, screen time, and body fat. Data were analyzed using descriptive statistics and logistic regression. Results: It was observed that 36.7% of the adolescents presented high WHtR (50.2% in girls and 23.9% in boys). Regardless of sex, adolescents with high body fat were more likely of having high WHtR (boys: Odds Ratio [OR] 29.79; 95% confidence interval [95%CI] 16.87-52.62; girls: OR 19.43; 95%CI 10.51-35.94). In girls, high WHtR was associated with age (OR 1.83; 95%CI 1.17-2.87), and in boys, with economic level (OR 2.34; 95%CI 1.01-5.45). Conclusions: One in each three adolescents has abdominal obesity. Among adolescents with high body fat, girls aged 15-16 and boys with high-income are the groups most exposed to abdominal obesity.

RESUMO Objetivo: Verificar a prevalência de obesidade abdominal, por meio da razão cintura-estatura (RCE), e fatores associados em adolescentes de uma cidade do sul do Brasil. Métodos: Participaram 965 adolescentes (499 meninos) de 15 a 18 anos. A variável dependente foi a RCE elevada e as variáveis independentes foram idade, nível econômico, maturação sexual, nível de atividade física, tempo de tela e adiposidade corporal. Os dados foram analisados por meio de estatística descritiva e regressão logística. Resultados: 36,7% dos adolescentes apresentaram RCE elevada (50,2% das meninas e 23,9% dos meninos). Independentemente do sexo, os adolescentes com adiposidade corporal elevada apresentaram maiores chances de terem RCE elevada (masculino: OR 30,91; IC95% 17,37-55,00; feminino: OR 19,18; IC95% 10,39-35,40). Nas meninas, observou-se associação da RCE elevada com idade (OR 1,88; IC95% 1,20-2,94) e, nos meninos, com nível econômico (OR 2,35; IC95% 1,01-5,46). Conclusões: Um em cada três adolescentes tem obesidade abdominal. Adolescentes com adiposidade corporal elevada, meninas de 15-16 anos e meninos de nível econômico alto são os grupos mais expostos à obesidade abdominal.

Handgrip strength and associated factors among Brazilian adolescents: A cross-sectional study.

BACKGROUND: The handgrip strength (HGS) is an indicator of muscle strength associated with several health outcomes in adolescents and adults. This cross-sectional study aimed to identify HGS levels and associated modifiable and non-modifiable risk factors in adolescents. METHODS: The study included 971 adolescents (496 boys) aged 15-18 years. The HGS was measured by a dynamometer, and the maximum value of right and left hands were summed for a total score. Age, economic status, balanced diet, physical activity, and sedentary behavior were assessed by questionnaires, while body mass index was determined by measuring body weight and height. Multiple linear regression was carried out to examine the association. RESULTS: 65.4% of the adolescents presented low levels of HGS (boys: 73.8%; girls: 56.6%). Low levels of HGS were associated with weight status and height in both sexes. In boys, low levels of HGS were associated with age, balanced diet, physical activity, and sedentary behavior. CONCLUSION: About six out of ten adolescentes presented low levels of HGS. The main predictors of low levels of HGS in boys were age, physical activity, sedentary behavior, and balanced diet, and weight status and height in both sexes.

High waist-to-height ratio and associated factors in adolescents from a city in Southern Brazil: a cross-sectional study.

OBJECTIVE: To verify the prevalence of abdominal obesity with the waist-to-height ratio (WHtR) and associated factors in adolescents from a city in Southern Brazil. METHODS: A total of 960 adolescents (494 boys) aged 15-18 years old participated in this study. The dependent variable was WHtR; independent variables were self-reported age, economic level, sexual maturation, physical activity level, screen time, and body fat. Data were analyzed using descriptive statistics and logistic regression. RESULTS: It was observed that 36.7% of the adolescents presented high WHtR (50.2% in girls and 23.9% in boys). Regardless of sex, adolescents with high body fat were more likely of having high WHtR (boys: Odds Ratio [OR] 29.79; 95% confidence interval [95%CI] 16.87-52.62; girls: OR 19.43; 95%CI 10.51-35.94). In girls, high WHtR was associated with age (OR 1.83; 95%CI 1.17-2.87), and in boys, with economic level (OR 2.34; 95%CI 1.01-5.45). CONCLUSIONS: One in each three adolescents has abdominal obesity. Among adolescents with high body fat, girls aged 15-16 and boys with high-income are the groups most exposed to abdominal obesity.

Normative values of handgrip strength in adolescents according to chronological age and sexual maturation

Abstract Aim: Handgrip strength is considered an important health indicator. It is extremely important to establish normative values so that the handgrip strength is correctly interpreted in adolescents. The present study aims to establish normative values of handgrip strength (HGS) for adolescents, according to chronological age and sexual maturation. Methods: Data from three large projects carried out in Florianopolis and São José, Santa Catarina were used, corresponding to a sample of 2,637 adolescents aged 14 to 19 years old of both sexes (1,428 girls). The HGS of the right and left hands was measured by a manual dynamometer, and total HGS being defined by the sum of the left hand and the right-hand strength. Sexual maturation was determined by the development of pubic hair. The percentiles 3, 10, 15, 25, 50, 75, 85, 90, and 97 were calculated for the right, left, and total HGS. The percentile ranges < p15 (low), p15-p85 (normal) and > p85 (high) were used. ANOVA and Kruskal-Wallis tests were applied. Results: In boys, the mean total HGS ranged from 67.5 ± 16.5 to 86.9 ± 21.8 (p < 0.001) and 74.3 ± 17.5 to 82.2 ± 17.8 (p < 0.001) for age and sexual maturation, respectively, while in girls the mean HGS total ranged from 48.8 ± 11.3 to 56.4 ± 16.0 (p = 0.127) and 47.8 ± 10.6 to 54.3 ± 12.3 (p < 0.001). Conclusion: Reference values established by the percentile score, can be used to identify adolescents with better athletic condition and can be useful for prescribing exercises.