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Context: Recently, studies using a social ecological perspective have identified important micro- and macro-level risk factors for excessive adiposity in youth. Although considerable research exists examining these relationships, few studies have applied a socioecological approach to simultaneously examine both micro- and macro-level factors in young children while objectively assessing adiposity via dual-energy x-ray absorptiometry (DXA)., Objective: To examine race and sex differences in adiposity measured by DXA in a large sample of young children and to identify both micro- and macro-level correlates of adiposity., Design: Cross-sectional., Setting and Participants: Elementary school children (N = 495) from the southeastern United States participated. Anthropometrics, percentage body fat via DXA, and psychosocial variables via questionnaire were assessed in the Fall of 2003. Community-level sociodemographic data and built-environment variables via geographic information system were collected in Spring 2009. Data analyses were completed in the Spring of 2010., Results: Percentage body fat in white children was higher than in nonwhite children. Higher percentage body fat and poorer cardiovascular fitness were found in females compared with males. Percentage body fat was higher in children who had lower athletic competence and lived in neighborhoods with higher percentages of minority residents., Conclusion: This study provides preliminary support for the social-ecological model to explain variance in adiposity in children. Developers of health promotion programs for children living in minority neighborhoods should consider factors at multiple levels of the ecological model when designing and implementing programs.

Background: Children tend to be sedentary during the after-school hours, and this has deleterious effects on their health. The objective of the present study was to determine the effects of a 3-year after-school physical activity (PA) program, without restriction of dietary energy intake, on percent body fat (%BF), cardiorespiratory fitness (CRF), and cardiometabolic markers in children., Methods: A cluster randomization design was employed. A total of 574 3rd grade children from 18 elementary schools in the southeastern United States participated. The intervention consisted of 80 minutes of age-appropriate moderate-to-vigorous PA each school day. The main outcomes of interest were %BF measured by dual-energy X-ray absorptiometry; CRF measured by heart rate in response to a submaximal step test; nonfasting total and high-density lipoprotein cholesterol (HDL-C); and resting blood pressure (BP)., Results: Intent-to-treat analyses showed significant treatment by time interactions for %BF (p = 0.009) and CRF (p = 0.0003). The change pattern of the means suggested that %BF and CRF in intervention children improved relative to control children during the school months, rebounding to the levels of control children over the summers following years 1 and 2. Year-by-year analyses of what occurred during the months when the program was offered revealed dose–response relations for %BF and CRF, such that the clearest beneficial effects were seen for those youth who attended at least 60% of the after-school sessions. No significant intervention effects were seen for cholesterol or BP., Conclusions: An after-school PA program was effective in reducing adiposity and improving CRF, especially in the children who attended the sessions at least 3 days/week. However, the favorable effects on %BF and CRF were lost over the summer. Thus, it is critical to incorporate strategies that attract and retain the children to receive an adequate dose of PA year-round.

Objectives: The objectives were to characterize the vitamin D status of black and white adolescents residing in the southeastern United States (latitude: approximately 33 degrees N) and to investigate relationships with adiposity., Methods: Plasma 25-hydroxyvitamin D levels were measured with liquid chromatography-tandem mass spectroscopy for 559 adolescents 14 to 18 years of age (45% black and 49% female). Fat tissues, physical activity, and cardiovascular fitness also were measured., Results: The overall prevalences of vitamin D insufficiency (<75 nmol/L) and deficiency (< or = 50 nmol/L) were 56.4% and 28.8%, respectively. Black versus white subjects had significantly lower plasma 25-hydroxyvitamin D levels in every season (winter, 35.9 + or - 2.5 vs 77.4 + or - 2.7 nmol/L; spring, 46.4 + or - 3.5 vs 101.3 + or - 3.5 nmol/L; summer, 50.7 + or - 4.0 vs 104.3 + or - 4.0 nmol/L; autumn, 54.4 + or - 4.0 vs 96.8 + or - 2.7 nmol/L). With adjustment for age, gender, race, season, height, and sexual maturation, there were significant inverse correlations between 25-hydroxyvitamin D levels and all adiposity measurements, including BMI percentile (P = .02), waist circumference (P < .01), total fat mass (P < .01), percentage of body fat (P < .01), visceral adipose tissue (P = .015), and subcutaneous abdominal adipose tissue (P = .039). There were significant positive associations between 25-hydroxyvitamin D levels and vigorous physical activity (P < .01) and cardiovascular fitness (P = .025)., Conclusions: Low vitamin D status is prevalent among adolescents living in a year-round sunny climate, particularly among black youths. The relationships between 25-hydroxyvitamin D levels, adiposity, physical activity, and fitness seem to be present in adolescence.

Objective: To evaluate the effect of a 3-year after-school physical activity (PA) intervention on aerobic fitness and percent body fat (%BF)., Methods: In total, 18 schools were randomized into intervention or control arms. Measurements were made at the beginning and end of the third, fourth and fifth grades. Fitness was measured with heart rate response to a bench-stepping task.%BF and bone density were measured with dual-energy x-ray absorptiometry. The intervention included 40 min of academic enrichment activities, during which healthy snacks were provided, and 80 min of moderate-to-vigorous PA (MVPA)., Results: Data analyses were performed on 206 youths who remained in the same schools for the 3-year period, who were measured at all six time points and, for the intervention group, who attended at least 40% of the sessions in each of the 3 years. The group by time interactions were significant for fitness (p < 0.01) and %BF (p < 0.05). Children in intervention schools improved in fitness and %BF during the school years and returned to levels similar to those in control schools during the summers. Over the six measurement points, the intervention group increased more than the control group in bone density (p < 0.01), fat-free soft tissue (p < 0.01), weight (p < 0.01), height (p < 0.01), and body mass index (p < 0.05)., Conclusions: An after-school program focusing on MVPA had a beneficial effect on fitness and body composition. During the summers, the beneficial effect of the previous year's participation on fitness and %BF was lost. This highlights the importance of year-round programs to promote healthy growth in youths.

Objective: The goal of this study was to evaluate the impact of a 10-month after-school physical activity (PA) program on body composition and cardiovascular (CV) fitness in young black girls., Research Methods and Procedures: Subjects were 8- to 12-year-olds recruited from elementary schools. Body composition was measured using anthropometrics {waist circumference and BMI, DXA [percentage body fat (%BF)] and bone mineral density (BMD)}, and magnetic resonance imaging [visceral adipose tissue (VAT)]. CV fitness was measured using a graded treadmill test. The intervention consisted of 30 minutes homework/healthy snack time and 80 minutes PA (i.e., 25 minutes skills instruction, 35 minutes aerobic PA, and 20 minutes strengthening/stretching). Analyses were adjusted for age, baseline value of the dependent variable, and sexual maturation (pediatrician observation)., Results: Mean attendance was 54%. Compared with the control group, the intervention group had a relative decrease in %BF (p < 0.0001), BMI (p < 0.01), and VAT (p < 0.01) and a relative increase in BMD (p < 0.0001) and CV fitness (p < 0.05). Higher attendance was associated with greater increases in BMD (p < 0.05) and greater decreases in %BF (p < 0.01) and BMI (p < 0.05). Higher heart rate during PA was associated with greater increases in BMD (p < 0.05) and greater decreases in %BF (p < 0.005)., Discussion: An after-school PA program can lead to beneficial changes in body composition and CV fitness in young black girls. It is noteworthy that the control and intervention groups differed in change in VAT but not waist circumference. This suggests that changes in central adiposity can occur in response to PA, even in young children, but that waist circumference may not be a good indicator of central adiposity.

Objective: The main purpose of this study was to determine the relationship between physical activity (PA) levels and adiposity. The secondary purpose was to assess the effect of physical fitness and living area on adiposity., Research Methods and Procedures: A cross-sectional study was carried out in a regional representative sample of 1068 children 7 to 12 years of age. Anthropometric and physical fitness values (including BMI, aerobic capacity, strength levels, velocity assessment, and flexibility) were measured in all children., Results: The prevalence of being overweight and obese in the entire sample was 31% and 6%, respectively. No difference between urban and rural children was found. The proportion of boys who were classified as overweight and obese was similar in physically active and sedentary (non-physically active) groups. However, physically active girls tended to show lower obesity prevalence compared with their sedentary counterparts (p = 0.06). In girls, the sum of the 6 skinfolds thickness (SSF) measurements was lower in the physically active group when compared with the non-physically active group (p < 0.05); however, this effect was not observed in boys. Multiple regression analysis revealed that the level of physical activity (PA) had a significant effect on BMI and SSF in boys but not in girls, while maximal oxygen uptake (VO2max) was significantly related to adiposity in both sexes., Discussion: Regular participation in at least 2 hours per week of sports activities on top of the compulsory education program is associated with better physical fitness and lower whole body adiposity. In the children included in our study, among all physical fitness variables, VO2max showed the strongest relationship with BMI and fat mass assessed by means of skinfold measurements.

The Physical Activity Questionnaire for Older Children (PAQ-C) is a validated self-report measure of physical activity widely used to assess physical activity in children (8-14 years of age). To date, however, the instrument has been validated in largely White Canadian samples. The purpose of the present article is to determine the psychometric properties of the PAQ-C for African American, European American, and Hispanic children. Two studies were conducted in which independent samples were administered the PAQ-C, along with varying indices of cardiovascular fitness, fatness, and psychological measures related to physical activity. Results showed that the reliability and validity of the PAQ-C varied by race and that modifications might be necessary.

Objectives: 1) Examine the association between Black mothers' and daughters' body fatness, physical activity (PA) beliefs and levels of PA, and daughters' PA behavior; 2) determine whether family sociodemographic factors influence these relationships., Design and Setting: Cross-sectional; Black girls recruited from elementary schools in a low socioeconomic area. Data collected at the Georgia Prevention Institute., Participants: 133 Black girls (8-12 years of age) and their mothers (24-66 years of age)., Analyses: Spearman correlations, regressions., Outcome Measures: Body mass index (BMI) as a measure of body fatness. Moderate and vigorous PA collected from a 7-d recall. Beliefs about PA collected from questionnaires., Results: There was a positive relation between mothers' and daughters' BMI (rs=0.34, P<.0001). Mothers' and daughters' PA beliefs were positive but not significantly related. A significant inverse relation was seen between vigorous PA (rs=-0.16, P<.05); and a non-significant correlation between moderate PA (rs=0.05). Mothers' body fatness, PA beliefs and behavior did not predict daughters' PA. The BMI association was stronger when spouse lived in household (P<.01). Daughters' BMI was lower (P<.05) and intent to be active higher (P<.05) when more people lived in the household. Family income accentuated the relation of mothers' belief in the usefulness of PA and daughters' PA physical outcomes beliefs (P=.1). Mothers' age and education had no significant influence on daughters' PA beliefs and behaviors., Conclusion: Mothers and daughters believed PA to have beneficial outcomes. Mothers' body fatness, PA beliefs and behaviors were not associated with daughters' PA. Family income and structure appeared to influence these relationships.

Purpose: We determined the degree to which variation in cardiac autonomic modulation was explained by race, sex, moderate-vigorous physical activity (MVPA), cardiovascular fitness (CVF), percent body fat (%BF), waist girth, subcutaneous abdominal adipose tissue (SAAT), and visceral adipose tissue (VAT)., Methods: Subjects were 304 adolescents; SAAT and VAT values were available for 168 youths. Cardiac parasympathetic modulation (PM) was the root mean square of successive differences (RMSSD). Sympathetic-parasympathetic balance was the ratio of low- to high-frequency power (LFnu:HFnu). MVPA was measured with accelerometry, CVF with a treadmill, %BF with dual-energy x-ray absorptiometry (DXA), and SAAT and VAT with magnetic resonance imaging (MRI)., Results: Root mean square of successive differences was higher, and LFnu:HFnu was lower, in blacks than in whites. The final regression model revealed positive relations with CVF and MVPA, and a %BF by race by sex interaction, such that higher %BF was associated with lower RMSSD in black females and higher RMSSD in white females. Higher RMSSD was associated with lower VAT; for SAAT, the relationship was negative for blacks and positive for whites. For LFnu:Hfnu, a negative relationship was seen with MVPA and higher waist girth was associated with a higher ratio in blacks, but not in whites. Both higher VAT and SAAT were related to higher LFnu:HFnu., Conclusions: Black youths had a more favorable HRV profile than white youths. After controlling for age, race, and sex, more favorable HRV profiles were associated with more MVPA, better CVF, and less visceral and subcutaneous adiposity. The deleterious impact of higher adiposity was greater in blacks, especially females, than in whites. Enhancement of cardiac autonomic modulation may be a pathway through which physical activity, fitness, and leanness contribute to cardiovascular health early in life.

Objective: To investigate the relations of attendance of children in an after-school physical activity (PA) program to changes in body composition and cardiovascular fitness (CVF)., Design: Eight-month after-school PA-based intervention., Subjects: In all, 278 third-grade boys and girls from nine elementary schools (age, 8.7 y (s.d. = 0.6 y), body mass index (BMI) 19.1 kg/m2 (s.d. = 4.4) and percent body fat (%BF) 26.0 (s.d. = 9.0))., Measurements: Body composition (from dual-energy X-ray absorptiometry), BMI (from height and weight), waist circumference (WC) and CVF (from the YMCA submaximal bench-stepping test)., Results: There was a significant negative linear trend between level of attendance in the after-school program and change in %BF and fat mass; there was also a significant positive linear trend between program attendance and change in CVF. There was a marginally significant linear trend between program attendance and fat-free mass. Greater increases in bone mineral density were observed with higher program attendance. Changes in BMI and WC were not influenced by program attendance., Conclusion: Understanding the dose-response effect of PA on health outcomes, particularly body composition, in children is crucial in our effort to prevent overweight and its health consequences. Since there is limited data available to base PA dose recommendations for youths, findings from this study are relevant, and suggest that greater health benefits can be obtained in young children with more frequent participation in PA.

Background: It is unclear how moderate and vigorous intensities of physical activity (PA) are associated with cardiovascular fitness (CVF) and percentage of body fat (%BF) in adolescents., Objective: We tested the hypothesis that vigorous PA, to a greater degree than moderate PA, would be associated with better CVF and lower %BF., Design: This was a cross-sectional study of 421 black and white high school students (x age: 16 y). PA was measured with 5 d of accelerometry and expressed in min/d of moderate or vigorous PA. CVF was measured with a multistage treadmill test and was expressed as the oxygen consumption at a heart rate of 170 bpm. %BF was measured with dual-energy X-ray absorptiometry. Multiple regressions were used to determine the degree to which variance in CVF and %BF was explained by PA, after control for age, sex, race, and the sex x race interaction., Results: A higher index for CVF was associated with higher amounts of moderate and vigorous PA; more variance was explained by vigorous than by moderate PA. Lower %BF was associated with higher amounts of vigorous PA but not with the amount of moderate PA., Conclusion: Black and white adolescents who engaged in relatively large amounts of free-living vigorous exercise were likely to be relatively fit and lean.

Objective: Little is known about the relations of fitness and fatness to left ventricular structure and function in obese adolescents. This project had 2 purposes: 1) to determine the correlations of cardiovascular fitness and adiposity to left ventricular parameters in obese adolescents; and 2) to see the effect of 8 months of physical training (PT) at low and high intensities., Design: Obese 13- to 16-year-olds (N = 81) were tested at baseline and then randomly assigned to lifestyle education (LSE) alone, LSE plus moderate-intensity PT, or LSE plus high-intensity PT. Follow-up testing was conducted 8 months later. Because no significant differences were found between moderate-intensity and high-intensity PT, the groups were combined to form a LSE + PT group., Intervention: Eight months of PT, offered 5 days per week with the target energy expenditure for all PT participants being 250 kcal/session, and LSE every 2 weeks. Outcome Measures. Left ventricular mass divided by height to the 2.7th power (LVM/Ht(2.7)), midwall fractional shortening (MFS), and relative wall thickness (RWT) were measured using M-mode echocardiography. Cardiovascular fitness was measured by a maximal multistage treadmill test; percent body fat (%BF) with dual-energy radiograph absorptiometry; and visceral adipose tissue (VAT) with magnetic resonance imaging., Results: At baseline, high levels of VAT were associated with higher RWT (r = 0.30) and lesser MFS (r = -0.29). Compared with the LSE-alone group, the LSE + PT group significantly improved in cardiovascular fitness and decreased in %BF and VAT. However, there were no significant differences between groups on changes in LVM/Ht(2.7), MFS, or RWT. Individual changes in cardiovascular fitness, %BF, and VAT did not correlate significantly with interindividual changes in left ventricular structure and function., Conclusions: High levels of VAT were associated with unfavorable left ventricular structure and function. However, no evidence was provided that an 8-month PT program, which improved cardiovascular fitness and reduced general and visceral adiposity, improved left ventricular structure and function. Future studies consisting of longer training programs and/or greater weight reductions are needed to see whether the adverse left ventricular effects of obesity can be ameliorated by exercise training.

Background: Little is known about how the intensity of exercise influences cardiovascular fitness and body composition, especially in obese adolescents., Objective: Our goal was to determine the effects of physical training intensity on the cardiovascular fitness, percentage of body fat (%BF), and visceral adipose tissue (VAT) of obese adolescents., Design: Obese 13-16-y-olds (n = 80) were assigned to 1) biweekly lifestyle education (LSE), 2) LSE + moderate-intensity physical training, or 3) LSE + high-intensity physical training. The intervention lasted 8 mo. Physical training was offered 5 d/wk, and the target energy expenditure for all subjects in physical training groups was 1047 kJ (250 kcal)/session. Cardiovascular fitness was measured with a multistage treadmill test, %BF with dual-energy X-ray absorptiometry, and VAT with magnetic resonance imaging., Results: The increase in cardiovascular fitness in the high-intensity physical training group, but not in the moderate-intensity group, was significantly greater than that in the LSE alone group (P = 0.009); no other comparisons of the 3 groups were significant. Compared with the LSE alone group, a group composed of subjects in both physical training groups combined who attended training sessions >or=2 d/wk showed favorable changes in cardiovascular fitness (P < 0.001), %BF (P = 0.001), and VAT (P = 0.029). We found no evidence that the high-intensity physical training was more effective than the moderate-intensity physical training in enhancing body composition., Conclusions: The cardiovascular fitness of obese adolescents was significantly improved by physical training, especially high-intensity physical training. The physical training also reduced both visceral and total-body adiposity, but there was no clear effect of the intensity of physical training.

Background: It is unclear whether cardiovascular fitness influences risk factors for coronary artery disease and non-insulin-dependent diabetes mellitus independently of level of body fat because fitness is often measured in tasks that involve moving body weight (eg, running) and because body weight and level of body fat are correlated., Objective: To measure fitness during a task in which body weight was controlled experimentally (ie, supine cycling)., Design: Cross-sectional., Participants: Seventy-four children, 7 to 13 years of age, recruited through school flyers and newspaper advertisements, varying in level of body fat from 7% to 61%. There were 31 boys and 43 girls; 35 were white and 39 were black., Main Independent Variables: Cardiovascular fitness was expressed as submaximal heart rate while cycling at a power output of 49 W, and level of body fat was measured with dual x-ray absorptiometry., Main Outcome Measures: Blood pressure and levels of triglycerides, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, insulin, glucose, and glycohemoglobin., Results: Controlling for age and sex, level of body fat was significantly (P < .01) related to unfavorable levels of systolic blood pressure (r = 0.32), triglycerides (r = 0.42), high-density lipoprotein cholesterol (r = -0.31), insulin (r = 0.50), and total cholesterol to high-density lipoprotein cholesterol ratio (r = 0.37); submaximal heart rate was not significantly correlated with any of the other variables., Conclusions: When cardiovascular fitness was measured in a weight-independent task, it was not significantly related to level of body fat or the major coronary artery disease and non-insulin-dependent diabetes mellitus risk factors. In addition, we confirmed previous findings that higher levels of body fat are associated with a very unfavorable risk profile.

The effects of supervised physical training (PT) and lifestyle education (LSE) on risk factors for coronary artery disease and non-insulin-dependent diabetes mellitus were compared in obese 7- to 11-yr-old black girls. The subjects were divided into two groups. The PT group (N = 12) completed a 5-d.wk-1, 10-wk, aerobic training program; and the LSE group participated in weekly lifestyle discussions to improve exercise and eating habits. The PT group showed a significant increase in aerobic fitness (P < 0.05) and decrease in percent body fat (P < 0.05), while the LSE group declined significantly more in dietary energy and percent of energy from fat (P < 0.05). Fasting insulin did not change significantly. The LSE group declined significantly more than the PT group in glucose (P < 0.05), and glycohemoglobin declined from baseline in both groups (P < 0.05). Lipid changes were similar in the two groups: total cholesterol/high density lipoprotein cholesterol (P < 0.01) and triglycerides (P < 0.05) declined, the low density lipoprotein (LDL)/apoproteinB ratio increased (which indicates a decrease in small dense LDL) (P < 0.05) and lipoprotein(a) increased (P < 0.05). Thus, the interventions were similarly effective in improving some diabetogenic and atherogenic factors, perhaps through different pathways; i.e., the PT improved fitness and fatness, while the LSE improved diet. Exercise and diet-induced changes in lipoprotein(a) require further investigation.

Objective: To determine whether body fatness, aerobic capacity, and fat distribution are associated with levels of cardiovascular risk factors in children., Methods: Subjects (N = 57) were 7 to 11 years of age; their percentage of body fat ranged from 10% to 58%. The percentage of fat was measured with dual-energy x-ray absorptiometry, maximal aerobic capacity was measured on a treadmill, fat distribution was expressed as the waist/hip circumference ratio, and blood pressures were measured with an automated monitor. Measurements of several lipoproteins and apoproteins were combined into one atherogenic index., Results: The percentage of fat was related to the atherogenic index (p = 0.38; p > 0.01) and insulin level (p = 0.78; p > 0.001). Aerobic capacity was inversely related to the atherogenic index (p = -0.27; p > 0.05) and insulin level (p = -0.72; p > 0.001). The waist/hip ratio was not related to the risk factors, and blood pressures were not related to fatness or aerobic capacity. In multiple regression analyses, only fatness explained significant independent proportions of the variance in the atherogenic index and insulin level. After control for fatness, the black children had higher insulin levels (p > 0.05)., Conclusion: At early ages (7- to 11-year-old children), fatness was related to risk factors for cardiovascular disease and diabetes.

Objective: To determine whether changes in aerobic fitness and body mass index are related to the age-related rise in blood pressure in healthy preschool children., Study Design: Longitudinal analyses of 196 free-living children aged 5 years at baseline who were followed over a mean of 19.7 months. Aerobic fitness was assessed using a treadmill. All measures were obtained on multiple occasions at scheduled visits as part of a longitudinal cohort study., Setting: An inner-city medical center., Outcome Measures: Blood pressure was measured using an automated Dinamap device., Results: Mean systolic blood pressure was 95.3 mmHg (SD 8.38) at baseline and increased by 4.46 mmHg per year. Mean diastolic blood pressure was 53.9 mmHg (SD 5.81) at baseline and did not change significantly. Children in the highest quintile of increase in fitness had a significantly smaller increase in systolic blood pressure compared to children in the lowest quintile (2.92 vs 5.10 mmHg/year; P = .03). Children in the lowest quintile of increase in body mass index did not differ significantly in rate of increase in systolic blood pressure compared to children in the highest quintile (3.92 vs 4.96 mmHg/year). In a multiple regression model including baseline systolic blood pressure, fitness, height, body mass index, and other covariates, greater increase in fitness (P = .03) and lesser increase in body mass index (P < .01) were associated with lower rates of increase in systolic blood pressure. In a similar multivariate analysis, an increase in fitness was also associated with a lower rate of increase in diastolic blood pressure (P = .02)., Conclusion: Young children who increase their aerobic fitness or decrease their body mass index reduce the rate of the age-related increase in blood pressure. These observations may have implications for development of interventions directed at the primary prevention of hypertension.

Objective: To examine the relationships among indicators of physical activity, physical fitness, and body composition with serum lipid and lipoprotein levels in young children., Design: Cross-sectional and 1-year prospective cohort., Setting: Studies of Child Activity and Nutrition (SCAN) program, Galveston, Tex., Subjects: One hundred twenty-three 4- or 5-year-old black, Hispanic (of Mexican origin), and white children., Measurements: Body composition, resting heart rate, and cardiovascular fitness variables and serum lipid and lipoprotein levels were measured at age 3 or 4 years (study year 1) and at age 4 or 5 years (study year 2), and day-long heart rate was measured and the Children's Activity Rating Scale was administered between study years 1 and 2., Results: Year-1 waist/hip ratios were inversely correlated with total serum cholesterol (TSC) and low-density lipoprotein (LDL) levels. Mean activity level was inversely correlated with waist/hip ratios. On the basis of multiple regression analysis, the sum of seven skin-fold measurements, height, and gender explained 15.4% of the variation in triglyceride levels. The sum of seven skin-fold measurements was inversely correlated with the high-density lipoprotein (HDL) level. Resting heart rate, waist/hip ratio, and the slope of the exercise heart rate during fitness testing explained 19.5% of the variation in the concentration of an HDL subclass, HDL2. These children's levels of physical activity were associated with higher fitness levels. Year-1 waist/hip ratios and year-2 sum of seven skin-fold measurements were positively correlated with the LDL/HDL and TSC/HDL ratios., Conclusion: Higher levels of cardiovascular fitness and lower levels of fatness were associated with more favorable serum lipid and lipoprotein levels in these young children. Physical activity appeared to have an indirect association with serum lipid and lipoprotein values through its relationship with higher fitness levels and lower levels of fatness.

Cross-sectional relations among blood pressure (BP), aerobic fitness, body fatness, and fat patterning were studied in 216 primarily Hispanic inner-city 5- and 6-year-olds. Fitness was measured with a submaximal treadmill test, and fatness was measured with five skin folds. Diastolic BP was inversely related to fitness in the boys and girls, and positively related to fatness for the boys. Systolic BP was positively related to fatness for the boys and girls. Using multiple regression and including parental BPs, fatness explained significant proportions of the variance in systolic BP for both the boys and girls and in diastolic BP for the boys. There were tendencies for central skin folds to explain more of the variation in BP than peripheral skin folds only for the boys. Fitness and fatness were inversely related for the boys and girls. Thus, at 5 and 6 years of age children exhibit some of the same risk factors for cardiovascular disease seen in adults.

Two heat-acclimatization protocols were studied in 8- to 10-yr-old boys: exercise in dry heat (WH, n = 9) and exercise in neutral climate (W, n = 9). Five 90-min acclimatization sessions were conducted within a 12-day period. Base-line (BL) and criterion (CT) tests sessions were held at 43 degrees C db and 24 degrees C wb, with three 20-min exercise bouts at approximately 40 Ws. With acclimatization, the WH group showed a significant reduction in heart rate (HR) (11.4 beat x min-1), mean skin temperature (0.64 degrees C), and an increase in the population density of heat-activated sweat glands (HASG) (25.2 glands x cm-2). The W group showed a significant reduction in HR (13.4 beat x min-1) and rectal temperature (0.24 C). Total sweat rate per body surface area did not increase significantly in either group. However, the sweat rate relative to rise in core temperature increased in both groups. No significant differences were found between the two acclimatization procedures in any of the variables studies except for the HASG, which showed a greater increase in the WH group. It is suggested that in 8- to 10-yr-old boys physiological changes compatible with heat acclimatization could be achieved either by exercise in heat or by mere physical conditioning (approximately 65% of VO2max), in neutral climate. It is postulated that age-related factors associated with the thermoregulatory system prevent children from deriving full effectiveness of exercise-in-heat acclimatization protocol as used in this study.

Maximal oxygen consumption (V O2 max) expressed in ml/kg/min and predicted V O2 max were determined before and after 8 weeks of training in 24 boys 10-12 years. Training involved 13 of them while 11 were controls. Predicted V O2 max was based on submaximal cycling heart rate according to the Astrand-Rhyming procedure. Pre-training, V O2 max was underpredicted by 12 per cent. This resulted mainly from an apparently low cycling efficiency in these subjects compared to that implicit in the prediction equation. Although adjustments in the prediction equation could equalize the means for V O2 max and predicted V O2 max, the rather low correlation (r = .55) between these measures precluded the accurate prediction of individual scores. V O2 max remained unchanged with training while submaximal heart rate during bicycle and treadmill exercise showed a significant decrease, resulting in predicted increases in V O2 max in children. Since V O2 max was actually unchanged, the prediction falsely indicated an improvement. Furthermore, despite a significantly lower heart rate in the trained group, there was no difference in predicted V O2 max between the groups post-training. These findings indicate that if V O2 max is the parameter of interest, it would seem to be more satisfactory to measure it directly until more reliable methods of prediction are developed.

The present study was designed to evaluate the specificity-generality of the cardiorespiratory adaptation to swim training. Fifteen male, college age, recreational swimmers utilized interval swim training procedures 1 h/day, 3 days/wk for 10 wk. Maximum physiological measures (Vo2, Ve, HR, R, and work time) were determined prior to and following swim training during treadmill running and tethered swimming Vo2max tests. Identical measures were made on 15 control subjects who did not participate in any form of training. As a result of training, the experimental subjects significantly increased (all P is less than 0.01) their swimming Vo2max (380 ml/min) max Ve (14.9 l/min,btps) and max swim time (4.0 min), and significantly decreased (P is less than 0.05) their max HR (3.5 beats/min). However, there was no significant improvement in Vo2max when the same subjects were evaluated by the treadmill running test. Differences in Vo2max and associated measures during running and swimming tests remained essentially unchanged for control subjects. The results of the present study clearly demonstrate the specificity of the cardiorespiratory adaptation to swim training in male recreational swimmers.