Effects of gender and aerobic fitness on cardiac autonomic responses to head-up tilt in healthy adolescents.

Cardiovascular autonomic responses to orthostatic challenges are affected by gender and cardiorespiratory fitness in adults. However, little is know about the effects of these factors in healthy adolescents. We studied 41 adolescents (20 boys and 21 girls) aged 12-17 years, divided into aerobic fitness tertiles based on the results of a maximal treadmill exercise test. Cardiac autonomic modulation was assessed by heart rate variability (HRV) analysis of 5-minute RR interval recordings before and after 70 degrees head-up tilt maneuver. HRV was analyzed by time (TD) and frequency domain (FD) methods. TD was analyzed by standard deviation of the RR intervals and the root mean square of successive differences of RR intervals. The power spectral components were studied at low (LF) and high (HF) frequencies and as the LF/HF ratio. We did not find any differences in TD and FD measures before and after tilt in either gender or fitness groups, except for a higher heart rate response for boys. These results suggests that cardiac autonomic responses to head-up tilt in healthy adolescents are not affected by gender or aerobic fitness.

Physical activity, cardiorespiratory fitness, dietary content, and risk factors that cause a predisposition towards cardiovascular disease.

OBJECTIVE: To analyze associations between levels of physical activity, cardiorespiratory fitness, dietary content, and risk factors that cause a predisposition towards cardiovascular disease. METHODS: Sixty-two individuals aged between 20 and 45 years were evaluated. Levels of physical activity were established by estimates of energy demand corresponding to everyday activity; indices for cardiorespiratory fitness were obtained from estimates of maximal oxygen consumption; information about dietary content was obtained from dietary records kept on seven consecutive days. To indicate risk factors that cause a predisposition towards cardiovascular disease, use was made of body mass indexes, waist-hip circumference relationships, levels of arterial pressure and of plasma lipid-lipoprotein concentration. To establish associations between the variables studied, multiple regression analysis was used. RESULTS: Physical activity levels and cardiorespiratory fitness levels were inversely correlated with the amount and distribution of body fat and arterial pressure. Taken together, the two variables were responsible for between 16% and 19% of the variation in arterial pressure. Total and saturated fat ingestion was associated with higher serum lipid levels. Both dietary components were responsible for between 49% and 61% of the variation in LDL-cholesterol. CONCLUSION: High ingestion of food rich in total and saturated fat and decreased levels of physical activity and of cardiorespiratory fitness are associated with an increased risk of cardiovascular disease, which supports previous data.

Subcutaneous central fat is associated with cardiovascular risk factors in men independently of total fatness and fitness.

The purpose of this study was to analyze the single and independent associations of whole body composition and fat distribution with cardiovascular disease (CVD) risk factors and fitness in middle-aged men. Sixty-two healthy Caucasian men (37.6 +/- 2.9 yr, 81.8 +/- 11.3 kg, 171.5 +/- 4.9 cm) participated in the study. Dual-energy x-ray absorptiometry (DXA) was used to assess total and regional body composition. The triceps, biceps, midthigh, calf, subscapular, chest, abdominal and suprailiac skinfolds, and the waist, hip and midthigh circumferences, and sagittal diameter were estimated. Cardiovascular fitness was estimated with a submaximal test. Bivariate and partial correlation analysis were used to study the association of total body percent fat (%fat), DXA trunk fat and trunk skinfolds (sum of subscapular, chest, abdominal, and suprailiac) and fitness with insulin, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), TC/HDL-C, low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), apolipoprotein AI (apo AI), apolipoprotein B (apo B), lipoprotein(a) [Lp(a)], and diastolic and systolic blood pressure. All anthropometric and DXA body composition variables were significantly correlated with TC/HDL-C (from .26 to .50, P < .05). Similar relationships were found for insulin, HDL-C, and systolic blood pressure (r from .26 to .47, P < .05). Cardiovascular fitness was significantly (P < .05) associated with insulin (r = -.36), HDL-C (r = .27), TC/HDL (r = -.27), and with systolic blood pressure (r = -.37). After controlling for trunk skinfolds, none of the anthropometric and DXA body composition variables were correlated with any of the CVD risk factors. Similarly, when controlling for trunk skinfolds, cardiovascular fitness was not related to any of the metabolic variables. After adjusting for %fat, DXA trunk fat, and cardiovascular fitness, trunk skinfolds remained significantly (P < .05) related to insulin (r = .35), HDL-C (r = -.40), TC/HDL-C (r = .43), and apo AI (r = -.39). In conclusion, this study suggests that subcutaneous truncal fat, as estimated by skinfolds, is an independent predictor of CVD risk factors, and that the association between cardiovascular fitness and these risk factors may be mediated by the levels of abdominal subcutaneous fat in Caucasian middle-aged men.

Comparison of air displacement plethysmography with dual-energy X-ray absorptiometry and 3 field methods for estimating body composition in middle-aged men.

This study was designed to compare air displacement plethysmography with dual-energy X-ray absorptiometry (DXA) and 3 other field methods for estimation of body composition. Subjects were 62 healthy, white men aged 37.6+/-2.9 y (weight: 81.8+/-11.3 kg; height: 171.5+/-4.9 cm). Body composition was also assessed by using body mass index, single-frequency bioelectrical impedance analysis, multi-frequency bioelectrical impedance spectroscopy, and the skinfold-thickness equations of Jackson and Pollock and Durnin and Womersley. Percentage body fat (%BF) with the plethysmograph was 23.4+/-7.0 and with DXA was 26.0+/-7.4. The 2.6% mean difference was significant (P< 0.05). Total error was 3.7%BF. As assessed by multiple regression analysis, %BF with the plethysmograph, age, weight, and height yielded a DXA-adjusted R2 value of 89.5% fat and an SEE of 2.4% fat. All other models had higher SEEs and lower adjusted R2 values: 4.3% and 66.5% for body mass index, 3.3% and 79.8% for bioelectrical impedance analysis, 3.6% and 76.2% for bioelectrical impedance spectroscopy, 3.7% and 74.55% for the equations of Jackson and Pollock, and 3.9% and 71.6% for the equations of Durnin and Womersley, respectively. The plethysmograph also predicted fat mass and fat-free mass more accurately than all other models, with a lower SEE and higher adjusted R2 value. In conclusion, although %BF was systematically underestimated, body composition was closely estimated with air displacement plethysmography in middle-aged men.

[Body fat distribution, blood pressure and plasma lipids and lipoprotein levels]. / Distribuição de gordura corporal, pressão arterial e níveis de lipídios-lipoproteínas plasmáticas.

PURPOSE: To study associations between FAT distribution and blood pressure levels and concentrations of lipids and lipoproteins, irrespective of body fat content and physical activity. METHODS: A sample of 62 subjects of both genders aging 20-45 years-old was used in the study. The adipose tissue distribution was based on the waist-to-hip ratio (WHR). Body fat content was estimated by the body mass index (BMI), and physical activity was assessed by maximal oxygen uptake (VO2max). Partial correlation analyses were used to determine the strength of the associations. RESULTS: After correction for BMI there was a significant partial correlation between centripetal adipose tissue distribution and serum triglyceride, LDL-cholesterol levels, and blood pressure. However, controlling for VO2max, there was no significant association between WHR and any serum variable and blood pressure. CONCLUSION: The centripetal adipose tissue distribution, independent of body fat content, was related to lipid and lipoprotein plasma concentrations and to blood pressure levels in both sexes. Physical activity seems to be an important modifier of this relationship, emphasizing its role in the control of cardiovascular risk factors.

Distribuiçäo de gordura corporal, pressäo arterial e níveis de lipídios-lipoproteínas plasmáticas / Body fat distribution, blood pressure and plasma lipids and lipoprotein levels

OBJETIVO - Investigar associaçöes entre distribuiçäo do tecido adiposo e níveis de pressäo arterial e concentraçöes de lipídios-lipoproteínas plasmáticas, mediante controle de indicadores, quanto à quantidade de gordura corporal e à prática da atividade física. MÉTODOS - Estudo de 62 indivíduos com idades entre 20 e 45 anos. A distribuiçäo do tecido adiposo foi determinada baseando-se na relaçäo circunferência de cintura/quadril (CCQ), e como indicador da quantidade de gordura corporal recorreu-se às informaçöes do índice de massa corporal (IMC), enquanto o nível de prática da atividade física foi estabelecido mediante estimativas do consumo máximo de oxigênio (VO2 max). As associaçöes entre ACQ e níveis de pressäo arterial e de lipídios-lipoproteínas plasmáticas, com efeitos do IMC e do VO2 max controlados estatisticamente, foram estabelecidas pelo coeficiente de correlaçäo parcial. RESULTADOS - Após correçäo pelo IMC verificou-se significativa correlaçäo parcial entre a distribuiçäo centrípeta do tecido adiposo e os níveis de pressäo arterial, LDL-C e triglicerídios plasmáticos. Entretanto, controlando-se o VO2 max, näo foram constatadas associaçöes significativas entre CCQ e qualquer variável sangüínea e pressäo arterial. CONCLUSÄO - A distribuiçäo centrípeta do tecido adiposo, independente da quantidade de gordura corporal, foi relacionada com concentraçöes de lipídios-lipoproteínas plasmáticas e níveis de pressäo arterial em ambos os sexos. A prática da atividade física parece ser um importante modulador dessa associaçäo, enfatizando seu papel no controle dos fatores de risco predisponentes às doenças cardiovasculares.

[Growth and motor performance of schoolchildren from the city of Londrina, Paraná, Brazil]. / Crescimento e desempenho motor em escolares do município de Londrina, Paraná, Brasil.

The purpose of this study was to develop an analysis concerning the behavior of variables aimed at characterizing growth and motor performance in relation to chronological age and gender, attempting to establish the level of importance of morphological aspects in modification of functional-motor activity in schoolchildren from the city of Londrina, Paraná, Brazil. The sample was composed of 1,180 randomly-selected subjects, from 7 to 17 years of age. Growth characteristics were determined by height and body weight. As for motor performance, tests for handgrip strength, sit-and-reach, sit-up, standing long jump, and 50- and 1000-meter races were applied. Analysis of results indicated that growth variables only begin to present important gender-based differences after 15 years of age, while for motor performance differences were found favoring boys in almost all motor tests from seven years on, with an increasing sexual dimorphism index as the children and adolescents grew. The low (albeit statistically significant) correlation between height/body weight and results of motor tests indicated that high growth patterns do not necessarily ensure a satisfactory motor performance index.

[Proposed equations for predicting the amount of body fat in young adults]. / Proposição de equações para predição da quantidade de gordura corporal em adultos jovens.

The purpose of this study was to derive regression equations to estimate body density based on skinfold thickness values in young adults. The sample was formed of 206 subjects, 110 males and 96 females, ranging from 18 to 30 years of age. The hydrostatic method was used to determine body density and fat percent. Skinfold thickness was measured at the biceps, triceps, subscapula, mid-axillary, rupra-iliac, abdomen, thigh, and calf with a HARPENDEN skinfold fat caliper. The equations were cross validated on a different of 41 subjects with similar age and physical characteristics. The regression equations suggested in this study were shown to be valid when applied to the Brazilian population: however the equations using three skinfold measures were considered the most useful ones, because of their practicality when used in evaluations of large populations.