Biocultural approach of the association between maturity and physical activity in youth / Abordagem biocultural da associação entre maturação e atividade física na juventude

Abstract Objective: To test the biocultural model through direct and indirect associations between biological maturation, adiposity, cardiorespiratory fitness, feelings of sadness, social relationships, and physical activity in adolescents. Methods: This was a cross-sectional study conducted with 1,152 Brazilian adolescents aged between 10 and 17 years. Somatic maturation was estimated through Mirwald's method (peak height velocity). Physical activity was assessed through Baecke questionnaire (occupational, leisure, and sport contexts). Body mass index, body fat (sum of skinfolds), cardiorespiratory fitness (20-m shuttle run test), self-perceptions of social relationship, and frequency of sadness feelings were obtained for statistical modeling. Results: Somatic maturation is directly related to sport practice and leisure time physical activity only among girls (β = 0.12, p < 0.05 and β = 0.09, respectively, p < 0.05). Moreover, biological (adiposity and cardiorespiratory fitness), psychological (sadness), and social (satisfaction with social relationships) variables mediated the association between maturity and physical activity in boys and for occupational physical activity in girls. In general, models presented good fit coefficients. Conclusion: Biocultural model presents good fit and emotional/biological factors mediate part of the relationship between somatic maturation and physical activity.

Resumo Objetivo: Testar o modelo biocultural por meio de associações diretas e indiretas entre maturação biológica, adiposidade, capacidade cardiorrespiratória, sentimentos de tristeza, relacionamentos sociais e atividade física em adolescentes. Métodos: Este foi um estudo transversal feito com 1.152 adolescentes brasileiros entre 10 e 17 anos. A maturação somática foi estimada por meio do método de Mirwald (pico da velocidade de crescimento). A atividade física foi avaliada por meio do questionário de Baecke (contextos ocupacional, lazer e prática de esportes). Foram obtidos o índice de massa corporal, gordura corporal (soma de dobras cutâneas), capacidade cardiorrespiratória (teste shuttle run de 20 metros), autopercepções de relação social e frequência de sensação de tristeza para modelagem estatística. Resultados: A maturação somática mostrou-se diretamente relacionada à prática de esportes e à atividade física de lazer somente entre meninas (β = 0,12, p < 0,05 e β = 0,09, respectivamente, p < 0,05). Ademais, as variáveis biológicas (adiposidade e aptidão cardiorrespiratória), psicológica (tristeza) e social (satisfação com os relacionamentos sociais) mediaram a associação entre maturação e atividade física em meninos e para atividade física ocupacional em meninas. Em geral, os modelos apresentaram bons coeficientes de ajuste. Conclusão: O modelo biocultural apresenta bom ajuste e fatores emocionais/biológicos mediam parte da relação entre maturação somática e atividade física.

Agreement between dual x-ray absorptiometers using pencil beam and fan beam: indicators of bone health and whole-body plus appendicular tissue composition in adult athletes

SUMMARY OBJECTIVE: The current study was aimed to examine intra-individual variation on indicators of bone health in addition to whole-body plus appendicular tissue measurements using two concurrent assessments based on pencil beam and fan beam dual energy X-ray absorptiometry (DXA) systems in adult athletes from several sports. METHOD: Thirty-two male participants (27.6±10.1 years) were measured on anthropometry including multifrequency bioelectric impedance and air-displacement plethysmography. Bone mineral content (BMC), bone area, fat and lean soft tissue were derived using pencil beam (Lunar DPX-MD+) and fan beam (Lunar iDXA) absorptiometry. Bone mineral density (BMD) was obtained for the femoral neck, trochanter and triangle of ward. Finally, the right thigh was defined as a region of interest (ROI). Analyses comprised intra-class correlation (ICC), Effect size (d) from mean differences of repeated measurements, coefficient of variation (CV) RESULTS: ICC were >0.900 for all measurements. Intra-individual differences were large for BMC (d=1,312; CV=2,7%), bone area (d=1,761; CV=2,7%), fat tissue (d=1,612; CV=11%) and all indicators of appendicular lean soft tissue (d=1,237-1687; CV=2,0-4,1%). A very large difference (d=4,014; CV=8.4%) was diagnosed for lean soft tissue of the ROI. CONCLUSION: Although differences among concurrent instruments for BMC and bone area, the effect size of mean differences was negligible for BMD. Fat and lean soft tissue derived from DXA should be interpreted as reference values (not criterion) due to equipment-related variation, more apparently in the ROI values.

RESUMO OBJETIVO: O presente estudo examinou a concordância entre os indicadores de saúde óssea e composição tecidual resultantes da aplicação de equipamentos concorrentes de absorciometria de raios X de dupla energia (DXA). MÉTODO: A amostra (n = 32), com 27,6 ± 10,1 anos de idade avaliados antropometricamente, inclui impedância bioelétrica com multifrequência e pletismografia de ar deslocado. O conteúdo mineral ósseo (CMO), a área de tecido ósseo, o tecido magro e o tecido gordo de corpo inteiro foram obtidos considerando o modo pencil beam (Lunar DPX-MD+) e o fan beam (Lunar iDXA). Para cada um dos equipamentos, foi efetuado um scanner proximal do fêmur, sendo produzida informação sobre a densidade mineral óssea (DMO) do colo, nomeadamente triângulo de Ward, trocanter e haste. Na fase de processamento, foi definida uma região de interesse (ROI; coxa direita). As análises compreenderam a diferença de médias de medidas repetidas com cálculo da magnitude de efeitos (d), coeficiente de correlação intraclasse (CCI), coeficiente de variação (CV). RESULTADOS: Foram obtidos CCI>0,900 para todas as medidas, com diferenças intraindividuais largas apenas para CMO (d = 1,312; CV = 2,7%), área de tecido ósseo (d = 1,761; CV = 2,7%), tecido gordo total (d = 1,612; CV = 11%) e tecido magro em todos os segmentos (d = 1,237-1,687; CV = 2,0-41%). A massa magra da ROI apresentou uma variaçāo intraindividual muito larga (d = 4,014; CV = 8,4%). CONCLUSÃO: Foram encontradas diferenças negligenciáveis para a DMO de corpo todo. As medidas de massa gorda e massa magra obtidas por DXA nāo devem ser tidas como critério, mas antes como referenda, muito especialmente quando se delimita uma ROI.

Twenty minutes of post-exercise hypotension are enough to predict chronic blood pressure reduction induced by resistance training in older women

AIM: This study investigated the correlation between post-exercise hypotension (PEH) and chronic blood pressure (BP) reduction in older women after a resistance training (RT) program. METHODS: Twenty-five older women (≥60 years) performed a RT program for 8 weeks, 3x/week consisting of 3 sets of 8-12 repetitions maximum in 8 exercises. Acute and chronic BP measurements were performed using automatic equipment, in which acute BP was measured before and after 10, 20, 30, 40, 50 and 60 min following the sixth exercise session, while chronic BP was measured pre and post-training. RESULTS: Significant decrease for systolic blood pressure (SBP) was observed after the intervention period, however, the diastolic blood pressure (DBP) did not change. To acute changes in BP, SBP decreased at all times after a single RT session, while DBP increased after 40 min. The reduction for SBP after a single RT session at baseline showed positive and significant correlations with the reductions in basal SBP observed after the 8 weeks of RT, the strongest correlations were observed at 20 min. A linear relationship between the magnitude of change in chronic SBP and the 20 min for acute SBP, and 30 min for acute DBP of post-exercise was observed. CONCLUSION: The results suggest that acute BP lowering after RT session is a reliable predictor of chronic BP response to exercise training, and 20 min of resting, after RT training, is enough to indicate chronic response of BP as this measure was highly associated with chronic BP lowering in older women.(AU)

Screen-based sedentary behaviors, mental health, and social relationships among adolescents

Abstract Aim: To analyze the association between screen-based sedentary behaviors, mental health, and social relationships in Brazilian adolescents. Methods: A representative sample of the adolescents from Londrina/PR was selected (n = 1,158; 10 to 17 y). Weekday and weekend screen time (TV-viewing and computer/video-game), mental health indicators (self-rated health, stress, feelings of sadness, and satisfaction with own body), and perceived social relationships (friends, family, and teachers) were collected through questionnaires. Somatic maturation, body mass index, and physical activity were assessed as covariates. Results: Adolescents who reported higher TV-viewing presented higher odds (p < 0.05) for poor self-rated health (boys), higher stress (both sexes), and dissatisfaction with own body (boys), friendships (girls), and teachers (girls). In contrast, higher computer/video-game use was associated with lower odds (p < 0.05) for poor self-rated health (girls), higher stress (boys), feelings of sadness (both sexes), and dissatisfaction with friends (both sexes) and family (both sexes). Conclusion: While higher TV-viewing is associated with negative outcomes, higher computer/video-game users demonstrate better mental health and lower satisfaction with their social relationships.

Validade dos métodos para avaliação da gordura corporal em crianças e adolescentes por meio de modelos multicompartimentais: uma revisão sistemática / Validity of the methods to assess body fat in children and adolescents using multi-compartment models as the reference method: a systematic review

OBJETIVO: Analisar a validade de métodos para avaliação de gordura corporal em crianças e adolescentes. MÉTODOS: A busca foi realizada por dois pesquisadores independentes, nas bases eletrônicas MEDLINE, BioMed Central, SciELO e LILACS. Como critérios de inclusão, os artigos deveriam ser escritos nas línguas inglesa ou portuguesa, ter utilizado como medida critério modelos multicompartimentais, com medida de gordura corporal em crianças e adolescentes não atletas. RESULTADOS: A busca preliminar resultou em 832 artigos, e após todas as etapas de seleção 12 compuseram esta revisão. Os trabalhos selecionados foram publicados entre 1997 e 2010, com amostras formadas por crianças e adolescentes com níveis de gordura corporal relativa de 20,7-41,4%. Os métodos utilizados foram: absortometria radiológica de dupla energia (58,3%), diluição de isótopos (41,6%), espessura de dobras cutânea (33,3%), pesagem hidrostática (25%), impedância bioelétrica (25%), pletismografia por deslocamento de ar (16,6%) e condutividade elétrica corporal total (8,3%). CONCLUSÃO: A partir da análise dos estudos, concluímos que os métodos diluição de isótopos e pletismografia por deslocamento de ar foram os que se apresentaram mais confiáveis, apesar do número reduzido de investigações. Já para a utilização clínica e em estudos populacionais, a equação de Slaughter et al., que utiliza a espessura das dobras cutâneas tricipital e subescapular, foi a que apresentou melhores resultados para avaliação da gordura corporal nessa população.

OBJECTIVE: To analyze the validity of methods to assess body fat in children and adolescents using a systematic review. METHODS: The search was conducted by two independent researchers using the MEDLINE, BioMed Central, SciELO and LILACS electronic databases. For inclusion, the articles should be written in English or Portuguese, andmust have usedmulti-compartment models as the criterion measure of the model, with body fat measurement of whole body in non-athlete children and adolescents. RESULTS: A preliminary search resulted in 832 studies. After all selection steps were performed, 12 articles were included. The selected studies were published between 1997 and 2010, whose samples consisted of children and adolescents with levels of relative body fat ranging from 20.7% to 41.4%. The methods used were: dual energy X-ray absorptiometry (58.3%), isotope dilution (41.6%), skinfold thickness (33.3%), hydrostatic weighing (25%), bioelectrical impedance analysis (25%), air displacement plethysmography (16.6%), and total body electrical conductivity (8.3%). CONCLUSIONS: Based on the analysis of the studies, isotope dilution and air displacement plethysmography methodswere the most reliable, despite the limited number of studies. As for clinical use or for population-based studies, the equation of Slaughter et al. (1998), wich uses the triceps and subscapular skinfolds thickness, showed the best results for assessment of body fat in this population.

Determinação do máximo déficit acumulado de oxigênio: efeito da duração dos testes submáximos para predição da demanda de oxigênio / Determination of the maximum accumulated oxygen deficit: effects of the submaximal tests duration for prediction of oxygen demand

O objetivo do presente estudo foi verificar a influência de diferentes tempos de análise dos testes submáximos para determinação do máximo déficit acumulado de oxigênio (MAOD), adotando diferentes janelas de tempo 4-6min, 6-8min e 8-10min. Participaram do estudo 10 ciclistas com idade média de 27,5 ± 4,1 anos, massa corporal 74,4 ± 12,7kg e tempo médio de prática de 9,8 ± 4,7 anos. Os atletas realizaram um teste de esforço progressivo para determinação do consumo de oxigênio de pico (VO2pico) e quatro testes retangulares submáximos (60, 70, 80 e 90 por cento VO2pico) com 10min de duração para estimar os valores da demanda de O2 (DEO2). Os valores médios de VO2 obtidos nas cargas para o tempo 4-6min, 6-8min e 8 a 10min foram aplicados em uma regressão linear entre a intensidade e o consumo de O2 para cada janela de tempo. Os sujeitos realizaram ainda um teste retangular supramáximo (110 por cento VO2pico) para a quantificação do MAOD. Não foi constatada nenhuma diferença significativa no VO2 entre os diferentes períodos de tempo dos testes submáximos (P > 0,05). Da mesma forma, nenhuma diferença significativa foi constatada no DEAO2 e MAOD nos diferentes períodos de análise (P > 0,05). Verificou-se ainda que os valores de MAOD obtidos nos três intervalos de tempo apresentaram boa concordância e forte correlação. Dessa forma, os dados sugerem que os testes submáximos utilizados para gerar os valores do MAOD podem ser reduzidos ao menos nesse tipo de amostra e com a utilização de ciclossimulador.

The aim of this study was to investigate the influence of different assessment time periods of submaximal tests on the determination of the maximal accumulated oxygen deficit (MAOD), through the adoption of different time slots of 4 to 6, 6 to 8 and 8 to 10 min. Ten cyclists with mean age of 27.5 ± 4.1 years, body mass 74.4 ± 12.7 kg and time experience of 9.8 ± 4.7 years participated in this study. The athletes underwent an incremental exercise test to determine the peak oxygen consumption (VO2peak), and four submaximal constant work-load test sessions (60, 70, 80 and 90 percent VO2peak) of 10 min in order to estimate the O2 demand (DEO2). The mean VO2 values obtained on each constant work-load for the 4 to 6, 6 to 8 and 8 to 10 min time-periods intervals were used to perform a linear regression between the intensity and O2 consumption for each time-period. In addition, the subjects performed one supramaximal rectangular test (110 percent VO2peak) for the quantification of MAOD. There was no significant difference in VO2 between the different time-periods for all submaximal tests (P> 0.05). Similarly, no significant difference was found in DEAO2 and MAOD (P> 0.05). Furthermore, the values of MAOD for the three time-periods intervals showed good agreement and strong correlation. Thus, the data suggest that the submaximal tests used to estimate the values of MAOD can be reduced, at least in this type of sample, and with the use of a cycle simulator.