Modeling the dynamics of BMI changes during adolescence. The Oporto Growth, Health and Performance Study.

OBJECTIVES: The aims of this study were twofold: (i) to model changes in body mass index (BMI) of 10-18-year-old adolescents, and (ii) to investigate the effects of total physical activity (TPA), physical fitness (PF), sleep duration and fruit/vegetable consumption in BMI trajectories across time. METHODS: Data were obtained from the Oporto Growth, Health and Performance Study and comprised 6894 adolescents (3418 girls) divided into four age cohorts (10, 12, 14 and 16 years) measured annually for 3 years. BMI was computed using the standard formula (kg m(-2)); TPA was estimated with the Baecke questionnaire; PF measures included 1-mile run/walk, 50 yard dash (50YD), standing long jump (SLJ), handgrip strength (HGr) and agility shuttle run. Longitudinal changes in BMI were analyzed using the multilevel modeling approach. RESULTS: The average BMI at age of peak of height velocity was 20.7±0.07 kg m(-2) for girls (P<0.001) and 20.58±0.06 kg m(-2) for boys (P<0.001). The annual increment in BMI was 1.36±0.04 kg m(-2), P<0.001 and 1.23±0.03 kg m(-2), P<0.001 for girls and boys, respectively. PF were related to BMI trajectories in both sexes (Girls: ß1mile=0.12±0.02, P<0.001; ßSLJ=-0.01±0.00, P<0.001; ß50YD=0.28±0.05, P<0.001; ßHGr=-8.91±0.54, P<0.001; Boys: ß1mile=0.18±0.02, P<0.001; ßSLJ=-0.01±0.00, P<0.001; ß50YD=0.26±0.04, P<0.001; and ßHGr=-8.15±0.45, P<0.001). TPA only showed significant, but positive, association with girls' BMI trajectories (ß=0.10±0.03, P=0.001). After adjusting for the covariates, sleep duration and fruit/vegetable intake did not show any significant association with BMI trajectories either sex. CONCLUSIONS: BMI increased linearly with age in both gender. PF levels are negatively associated with BMI across time in both boys and girls. Therefore, promotion of PF in the adolescent years seems to be effective in the early prevention of obesity.

Physical fitness percentile charts for children aged 6-10 from Portugal.

AIM: The present study aims (1) to provide reference percentile charts for the following measures of Physical Fitness (PF): the sit-and-reach, handgrip, standing long jump, 50 yards' dash, 4x10m shuttle run and 1-mile run/walk tests in children aged 6 to 10 years, and (2) to compare the performance of the Portuguese children with their age- and sex peers. METHODS: A total of 3804 Portuguese children (1985 boys and 1819 girls) aged 6-10 years old participated in this study. The sample was stratified from 20 public elementary schools and children were randomly selected in each school. Charts were separately built for each sex using the LMS method. RESULTS: Boys showed better results than girls in handgrip, standing long jump, 50 yards' dash, 4x10 m shuttle run and 1-mile run/walk, while girls are better performers than boys in sit-and-reach. CONCLUSION: Age- and gender- percentiles for a set of physical fitness tests for 6-10 year old (primary school) Portuguese children have been established. Boys showed greater overall PF than girls, except in the flexibility test, in which girls performed better. The reported normative values provide ample opportunities to accurately detect individual changes during childhood. These reference values are especially important in healthcare and educational settings, and can be added to the worldwide literature on physical fitness values in children.

Tracking of aerobic fitness from adolescence to mid-adulthood.

BACKGROUND: Although adults' aerobic fitness is known to be correlated with cardiovascular disease risk, the longitudinal relationship with adolescent aerobic fitness is poorly described. AIM: To longitudinally investigate the relationship between aerobic fitness during adolescence and adulthood. SUBJECTS AND METHODS: Participants (207 boys, 149 girls) aged 7-17 years performed annual measures of VO2peak. In adulthood (40 and 50 years), 78 individuals (59 males and 18 females) were reassessed. Serial height measurements were used to estimate age at peak height velocity (APHV). During adolescence, VO2peak was measured via a treadmill test to voluntary exhaustion; adult VO2peak was assessed using submaximal predictive tests. Correlations were tested using Spearman's rho. ANCOVA was used to assess adult VO2peak group differences based off APHV VO2peak groupings (low, average or high). RESULTS: When sexes were pooled, moderate tracking existed from 2 years prior to APHV to APHV and APHV to 2 years after APHV (0.46, p < 0.001 and 0.35, p < 0.01, respectively). Correlations between APHV and adult values were low when sexes were pooled (p < 0.05). Comparisons of aggregated sexes revealed the low adolescent VO2peak group had lower values in adulthood relative to other groups (p < 0.05). CONCLUSION: Aerobic fitness has a low tracking between APHV and adulthood.

Associations of physical activity and fitness with adipocytokines in adolescents: the AFINOS Study.

BACKGROUND AND AIMS: Adipocytokines may have a key role in the development of atherosclerosis and type 2 diabetes. The purpose of this study was to examine the independent and joint associations of physical activity (PA), cardiorespiratory fitness (CRF) and muscular fitness (MF) with adiponectin and leptin in adolescents. METHODS AND RESULTS: A sample of 198 adolescents (96 girls), aged 13-17-year, was selected. Participants completed anthropometric measurements (height, weight, and waist circumference) and percentage of body fat (%BF) was estimated by bioelectrical impedance. PA was measured by accelerometer for 7-day. The 20-m shuttle-run test was used to assess CRF and two MF tests (handgrip strength and standing broad jump) were used to create an MF score. A cluster score of health status (0-3 risks) was created. Serum adiponectin and plasma leptin were also determined. Regression analyses controlling for age, sex, pubertal status and waist circumference showed that PA was not significantly associated with adiponectin and vigorous PA showed a significant inverse association with leptin. Both CRF and MF were significantly and inversely associated with adiponectin and leptin. Further analyses revealed that the 'healthy' group (0 risks) had significantly lower adiponectin and leptin than 'medium-healthy' (1 risk) and 'unhealthy' (2-3 risks) status groups. CONCLUSIONS: PA, CRF and MF are inversely and jointly associated with adiponectin and leptin concentrations in adolescents.

Concurrent validation of estimated activity energy expenditure using a 3-day diary and accelerometry in adolescents.

Estimates of daily energy expenditure are important to studies of physical activity and energy balance. Objective measures are not always feasible and further research is needed to validate survey instruments and diaries. The study validates estimated activity energy expenditure (AEE) based on a 3-day diary protocol relative to AEE derived from uniaxial accelerometry in adolescents, 265 girls and 227 boys (12.5-16.4 years). Participants completed the diary and wore a GT1M Actigraph accelerometer on the same days. Height and weight were measured. Correlations between protocols were significant (P<0.001) but moderate, r=0.65 in males and r=0.69 in females. The highest correlation occurred among males on Friday, r=0.74 (P<0.01). Controlling for body mass, partial correlations between protocols decreased to 0.44 and 0.35 in males and females, respectively. About 97% of the cases fell within the limits of agreement in a Bland-Altman plot. The criterion of inclusion for the accelerometer excluded 18% of the initial sample. In summary, the 3-day diary was completed without any major problems and provided a reasonably valid alternative for assessing AEE. Concordance between methods was slightly lower for individuals with higher values of AEE.

Western diet increases wheel running in mice selectively bred for high voluntary wheel running.

OBJECTIVE: Mice from a long-term selective breeding experiment for high voluntary wheel running offer a unique model to examine the contributions of genetic and environmental factors in determining the aspects of behavior and metabolism relevant to body-weight regulation and obesity. Starting with generation 16 and continuing through to generation 52, mice from the four replicate high runner (HR) lines have run 2.5-3-fold more revolutions per day as compared with four non-selected control (C) lines, but the nature of this apparent selection limit is not understood. We hypothesized that it might involve the availability of dietary lipids. METHODS: Wheel running, food consumption (Teklad Rodent Diet (W) 8604, 14% kJ from fat; or Harlan Teklad TD.88137 Western Diet (WD), 42% kJ from fat) and body mass were measured over 1-2-week intervals in 100 males for 2 months starting 3 days after weaning. RESULTS: WD was obesogenic for both HR and C, significantly increasing both body mass and retroperitoneal fat pad mass, the latter even when controlling statistically for wheel-running distance and caloric intake. The HR mice had significantly less fat than C mice, explainable statistically by their greater running distance. On adjusting for body mass, HR mice showed higher caloric intake than C mice, also explainable by their higher running. Accounting for body mass and running, WD initially caused increased caloric intake in both HR and C, but this effect was reversed during the last four weeks of the study. Western diet had little or no effect on wheel running in C mice, but increased revolutions per day by as much as 75% in HR mice, mainly through increased time spent running. CONCLUSION: The remarkable stimulation of wheel running by WD in HR mice may involve fuel usage during prolonged endurance exercise and/or direct behavioral effects on motivation. Their unique behavioral responses to WD may render HR mice an important model for understanding the control of voluntary activity levels.

Associations of physical activity, cardiorespiratory fitness and fatness with low-grade inflammation in adolescents: the AFINOS Study.

OBJECTIVE: To examine the independent associations of objectively measured physical activity (PA), cardiorespiratory fitness (CRF) and fatness with low-grade inflammatory markers in adolescents. DESIGN: Cross-sectional study in Spain. SUBJECTS: A sample of 192 adolescents aged 13-17 years. MEASUREMENTS: PA was assessed with an accelerometer for 7 days. A 20-m shuttle-run test was used to assess CRF. Skinfold thicknesses at six sites and WCs were measured. BMI was calculated from measured height and weight. C-reactive protein (CRP), interleukin-6 (IL-6) and complement factors C3 and C4 were assayed. The homeostasis model assessment of insulin resistance (HOMA-IR) was calculated from glucose and insulin. Regression analysis adjusted for potential confounders and HOMA-IR was used to determine the associations between PA, CRF and fatness with low-grade inflammatory markers. RESULTS: Total PA, vigorous PA and MVPA were positively associated with CRF (r=0.25-0.48), whereas vigorous PA was negatively associated with skinfolds (r=-0.27). CRF was inversely associated with fatness, (r=-0.30 to -0.48). CRF and fatness were inversely and positively associated with HOMA-IR (r=-0.16 and 0.21, respectively). PA variables were not independently associated with inflammatory markers. CRF and fatness were inversely and positively associated with CRP, C3 and C4, respectively. Only body fat explained a relevant amount of the variance of the model in CRP (4%) and C4 (19%), whereas CRP and body fat jointly explained the variance in C3 (25%). All these observations were independent of HOMA-IR. CONCLUSIONS: These findings support the key role of CRF and fatness on low-grade inflammation, as well as the possible indirect role of habitual PA through CRF and body fat in adolescents.

The role of physical activity and fitness on the metabolic syndrome in adolescents: effect of different scores. The AFINOS Study.

The aim of this study was to examine the associations of objectively measured physical activity (PA) and cardiorespiratory fitness (CRF) with different continuous metabolic syndrome (MetS) scores in adolescents. A cross-sectional sub-sample of 202 adolescents (99 girls), aged 13-17 years, were selected from the AFINOS Study. Body mass index, sum of 6 skindfold, waist circumference, systolic and diastolic blood pressure, insulin, glucose, triacylglycerol, and HDL-cholesterol levels were determined. Moderate PA (MPA), vigorous PA (VPA) and moderate to vigorous PA (MVPA) were assessed by the ActiGraph accelerometer for 7 consecutive days and CRF was estimated by the 20-m shuttle run test. Three continuous MetS scores were calculated according to the methodology of the Corpus Christi Child Heart Study (CCCHS), the Aerobic Center Longitudinal Study (ACLS), and the European Youth Heart Study (EYHS). VPA and MVPA were significantly related with CRF. Only CRF, and not patterns of PA, was inversely and independently associated with the three MetS scores although with different magnitudes (ranged: beta = 0.22 to 0.36, p < 0.05). A significant VPA x CRF interaction (p = 0.011) was found using the ACLS MetS score. Trends across VPA-CRF groups were significantly different with ACLS and EYHS (p = 0.002 and p = 0.006, respectively), but not with CCCHS (p = 0.313) continuous MetS scores. These findings support the key role of CRF on the MetS and the relevance of PA, especially VPA, to provide CRF in adolescents. A unified pediatric definition of MetS might minimize the discrepancies among studies.

Combined influence of physical activity and television viewing on the risk of overweight in US youth.

OBJECTIVE: The purpose of this study was to examine the combined influence of physical activity (PA) and television viewing (TV) on the risk of overweight in US youth ages 14-18 years. RESEARCH DESIGN AND METHODS: Cross-sectional data from a nationally representative sample of approximately 13,600 US high school students participating in the 2001 Centers for Disease Control and Prevention Youth Risk Behavior Survey (YRBS) were examined. Participants were cross-tabulated into nine PA-TV groups according to the level of moderate (MPA) or vigorous PA (VPA) (low: < or = 2 days per week; moderate: 3-5 days per week; high: 6-7 days per week) and TV (low: < or = 1 h per day; moderate: 2-3 h per day; high: > or = 4 h per day). The referent group was the low TV/high PA group. The body mass index was used to determine overweight and obesity based on the International Obesity Task Force reference values. Logistic regression was used to examine the influence of TV and PA on the odds of overweight in boys and girls, while controlling for age and ethnicity. RESULTS: Boys and girls watching low levels of TV did not have increased odds of overweight regardless of PA level with the exception of girls with low TV/low VPA (odds ratio (OR)=1.48). Girls who watched moderate and high levels of TV had increased odds of overweight at any level of MPA or VPA (OR 1.24-3.11). In girls, the odds of overweight increased in a graded manner across PA levels for both the moderate and high levels of TV. Girls with high TV/low VPA had the highest odds of overweight (OR=3.11). In general, most of the associations were stronger in girls compared to boys. CONCLUSION: The results highlight the importance of considering both PA and TV as risk factors for overweight in adolescents.

Adiposity and cardiac dimensions among 9- to 18-year-old youth: the Québec Family Study.

The relationship between adiposity and cardiac dimensions were considered in healthy 9- to 18-year-old boys (n=198) and girls (n=154). Indicators of adiposity included the body mass index (BMI), sum of skinfolds (SSF) and trunk-to-extremity ratio (TER). The following left ventricular (LV) dimensions were measured by echocardiography: internal diameter (LVIDd); posterior wall thickness (PWT) and intraventricular septal wall thickness. LV mass (LVM) was estimated. In boys, 11 of 45 correlations were significant. The magnitude of the correlations increased across age groups and most of the correlations were significant in the oldest age group. In girls, 18 of 45 correlations were significant, but there were inconsistent patterns in the magnitude of the correlations across age groups. Correlations between BMI and LVIDd and LVM were highest in youth 13-15 years, whereas other correlations involving the BMI were rather constant across age groups. Correlations involving SSF were significant only in 9-12 and 13-15 year olds. There were no significant correlations involving TER in female subjects. In the total sample of boys, only correlations between the BMI and LV parameters were significant (r=0.14-0.38), except for the relationship between SSF and PWT (r=0.21). The TER was weakly associated with LV parameters. In the total sample of girls, correlations for LV parameters were significant for both the BMI (r=0.20-0.43) and SSF (r=0.18-0.28; except for LVIDd). TER was not significantly related to LV parameters except LVIDd (r=0.16). The findings indicate that the BMI is an important determinant of LV structure.

Adolescent Trajectories of Aerobic Fitness and Adiposity as Markers of Cardiometabolic Risk in Adulthood.

Purpose: The aim of this study was to investigate whether adolescent growth trajectories of aerobic fitness and adiposity were associated with mid-adulthood cardiometabolic risk (CMR). Methods: Participants were drawn from the Saskatchewan Growth and Development Study (1963-1973). Adolescent growth trajectories for maximal aerobic capacity (absolute VO2 (AbsVO2)), skinfolds (SF), representing total body (Sum6SF) and central adiposity (TrunkSF), and body mass index (BMI) were determined from 7 to 17 years of age. In mid-adulthood (40 to 50 years of age), 61 individuals (23 females) returned for follow-ups. A CMR score was calculated to group participants as displaying either high or a low CMR. Multilevel hierarchical models were constructed, comparing the adolescent growth trajectories of AbsVO2, Sum6SF, TrunkSF, and BMI between CMR groupings. Results: There were no significant differences in the adolescent development of AbsVO2, Sum6SF, TrunkSF, and BMI between adult CMR groupings (p > 0.05). Individuals with high CMR accrued 62% greater adjusted total body fat percentage from adolescence to adulthood (p=0.03). Conclusions: Growth trajectories of adolescent aerobic fitness and adiposity do not appear to be associated with mid-adulthood CMR. Individuals should be encouraged to participate in behaviours that promote healthy aerobic fitness and adiposity levels throughout life to reduce lifelong CMR.

Within- and between-individual variability in estimated energy expenditure and habitual physical activity among young adults.

OBJECTIVE: To examine the within- and between-individual variability in the estimated total energy expenditure (TEE) and habitual physical activity (PA) in free-living young adults. We were specifically interested in the day-to-day variation. DESIGN: Cross-sectional. SETTING: University. SUBJECTS: A total of 277 (125 males, 152 females) participants aged 18-24 years. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Subjects recorded their daily PA with the Bouchard 3-day diary. Descriptive statistics for TEE, moderate-to-vigorous physical activity (MVPA), inactivity (IA), and activity energy expenditure (AEE) were calculated and presented as a frequency distribution. Within- and between-individual variability were tested by RMANOVA and also presented as the coefficient of variation (CV). RESULTS: Mean values for TEE, MVPA, AEE, and IA were comparable between males and females; however, considerable between-individual variability existed. Only MVPA showed a significant difference between sexes (P<0.05), due to slightly greater vigorous PA in males compared to females (8.0 and 6.8 kcal/kg/day, respectively; P=0.12). Results from the RMANOVA revealed no significant day-to-day variability in any TEE or PA variable and the CVs were not significantly different between males and females. TEE and IA displayed mean CVs of approximately 12% while mean CVs for AEE and MVPA approximated 32 and 84%, respectively. CONCLUSIONS: Results from this study suggest (1) a limited day-to-day variability in TEE and (2) a large degree of between-individual variation for TEE and PA exist. This study highlights the importance of understanding the variability associated with TEE, which is important for PA measurement and proper PA and nutritional recommendations. SPONSORSHIP: None.

Associations between adiposity, family history of CHD and blood pressure in 3-8 year-old children.

The purpose of this study was to examine the relationships between overall and central adiposity, a family history of coronary heart disease (FHCHD), and blood pressure (BP) in young children. We were specifically interested in determining whether the relationship between adiposity and BP was modified by a FHCHD. Subjects were 130 (68 males, 62 females) young children (mean age 6.0 years). Indicators of adiposity included the body mass index, waist circumference, skinfold thickness, and body composition determined by dual energy X-ray absorbtiometry (DXA). BP was measured by standard procedures. FHCHD was reported by the parent on a questionnaire. Approximately 19% of the total sample was classified as overweight and almost 50% were classified as prehypertensive (22.4%) or hypertensive (24.8%). In the total sample, 21 of 27 correlations were significant and ranged from 0.03 to 0.52. Correlations for systolic blood pressure appeared to be stronger in female subjects. Most of the correlations for diastolic blood pressure and mean arterial pressure were significant in both sexes and, in general, ranged between 0.30 and 0.50. Overweight status was significantly associated with high BP (crude odds ratio=3.65, 95% confidence intervals 1.40-9.49). There were no significant associations between a positive FHCHD and BP, and the correlations between BMI, WC, and BP were similar in magnitude in subjects with and without a FHCHD. In conclusion, both overall and central adiposity are important determinants of resting BP in young children. A FHCHD was not associated with BP and nor were the associations between adiposity and BP modified by a FHCHD.

Comparative survival, quality of life and cost-effectiveness of intensive therapy with autologous blood cell transplantation or conventional chemotherapy in multiple myeloma.

We retrospectively compared survival time, quality of life, and the therapy costs in 37 patients suffering from newly diagnosed multiple myeloma (MM), divided into 3 groups. Twelve patients with grade III MM, according to the classification of Durie-Salmon, all with widespread lytic lesions (group I), underwent a two-phase intensive therapy. They first received high-dose melphalan (HDM), both as tumor-reducing and blood cell (BC)-mobilizing chemotherapy, subsequently followed by BC transplantation. Group II comprising 10 patients, also with grade III MM and with characteristics similar to those of group I, were treated with conventional polychemotherapy. Finally, group III enrolled 15 patients with lower grade disease (grade II) who were also treated with conventional chemotherapy. The median overall survival time and the quality of life index were significantly lower in group II than in group I (P = 0.0013 and < 0.001 respectively). Although the overall survival time of group III (43 months) was similar to that of group I, its quality of life index was also significantly lower (P < 0.05). However, the total therapy costs of group I were globally higher than those of the 2 other groups, but when absolute cost-effectiveness as well as qualitative cost-effectiveness (corrected for quality of life) were analyzed, the costs per week of life gained of group I compared extremely favorably with those of group II and, to a lower degree, of group III. Intensive therapy therefore seems capable of substantially improving the survival time for high-risk MM patients with satisfactory quality of life and at a reasonable cost.

Comparison of hematopoietic and immune recovery after autologous bone marrow or blood stem cell transplants.

We studied hematopoietic and immune recovery in 40 subjects receiving autologous bone marrow (ABMT) or blood stem cell transplants (ABSCT). Supportive care, transplant-related morbidity, duration of hospitalization and cost were also considered. ABSCT was associated with more rapid recovery of all hematopoietic lineages than was ABMT. However, kinetics of immune recovery were similar between the groups. In the ABSCT group, there was a correlation between numbers of blood progenitor cells infused and the rate of hematopoietic recovery. The accelerated hematopoietic recovery following ABSCT correlated with less morbidity, fewer transfusions, briefer hospitalization and lower cost than ABMT.

Scaling peak VO2 to body mass in young male and female distance runners.

This study examined age- and sex-associated variation in peak oxygen consumption (VO2) of young male and female distance runners from an allometric scaling perspective. Subjects were from two separate studies of 9- to 19-yr-old distance runners from the mid-Michigan area, one conducted between 1982 and 1986 (Young Runners Study I, YRS I) and the other in 1999-2000 (Young Runners Study II, YRS II). Data from 27 boys and 27 girls from YRS I and 48 boys and 22 girls from the YRS II were included, and a total of 139 and 108 measurements of body size and peak VO2 in boys and girls, respectively, were available. Subjects were divided into whole year age groups. A 2 x 9 (sex x age group) ANOVA was used to examine differences in peak VO2. Intraindividual ontogenetic allometric scaling was determined in 20 boys and 17 girls measured annually for 3-5 yr. Allometric scaling factors were calculated using linear regression of log-transformed data. Results indicated that 1) absolute peak VO2 increases with age in boys and girls, 2) relative peak VO2 (ml x kg(-1) x min(-1)) remains relatively stable in boys and in girls, 3) relative peak VO2 (ml x kg(-0.75) x min(-1)) increases throughout the age range in boys and increases in girls until age 15 yr, and 4) peak VO2 adjusted for body mass (ml/min) increases with age in boys and girls. The overall mean cross-sectional scaling factor was 1.01 +/- 0.03 (SE) in boys and 0.85 +/- 0.05 (SE) in girls. Significant age x sex interactions and significant scaling factors between sexes identify the progressive divergence of peak VO2 between adolescent male and female distance runners. Mean ontogenetic allometric scaling factors were 0.81 [0.71-0.92, 95% confidence interval (CI)] and 0.61 (0.50-0.72, 95% CI) in boys and girls, respectively (P = 0.002). There was considerable variation in individual scaling factors (0.51-1.31 and 0.28-0.90 in boys and girls, respectively). The results suggest that the interpretation of growth-related changes in peak VO2 of young distance runners is dependent upon the manner of expressing peak VO2 relative to body size and/or the statistical technique employed.

Blood lipids in young distance runners.

PURPOSE: The purpose of this study was to examine the age-and sex-associated variation in blood lipids among young athletes. METHODS: A mixed-longitudinal design was used to examine the development of blood lipids in competitive young distance runners followed from 1982 to 1985. Serial data included 99 annual measurements for 27 male subjects and 84 annual measurements for 27 female subjects aged 9-18 yr. Total cholesterol (TC), high-density lipoprotein (HDL-C), low-density lipoprotein (LDL-C), and triglycerides (TG) were determined by standard procedures. RESULTS: In general, cross-sectional age group means showed that TC and LDL-C remained stable and HDL-C declined with age, especially in male subjects. TG increased with age. Age-related trends were statistically significant for HDL-C and TG in boys only (P < 0.05). TC and LDL-C were slightly greater in boys at all ages except 11, 15, and 17 yr (P > 0.05). HDL-C was similar between the sexes until 13 yr when values became greater in girls (3.2-13.8 mg.dL(-1)) (P < 0.05 in 17+ yr). No clear pattern of sex differences emerged for TG. Compared with the general population, blood lipids of young distance runners showed the following trends: 1) TC was above reference medians, 2) LDL-C tended to approximate or to be slightly above reference medians, 3) TG fluctuated about the reference medians, and 4) HDL-C was higher in distance runners compared to the reference medians before age 14 yr, but in the older age groups, especially male subjects, HDL-C either approximated or fell slightly below the reference medians. There was considerable variability in blood lipid levels among the runners. In 21 male and 18 female subjects with serial data for 3-5 yr, HDL-C declined 22.4 and 18.3 mg.dL(-1) (P < 0.05), whereas TG increased 18.0 and 14.0 mg.dL(-1)(P < 0.05 in female subjects only) in male and female subjects, respectively. Tracking coefficients over intervals of 3-5 yr were moderate to high (0.48-0.90), except for TG in male subjects (0.08). CONCLUSIONS: The results indicate that the development of blood lipids in young distance runners is similar to youth in the general population. In contrast to observations in adult endurance athletes, young distance runners did not possess a superior blood lipid profile except for HDL-C in the younger age groups.

Comparative analysis of the Cosmed Quark b2 and K4b2 gas analysis systems during submaximal exercise.

AIM: The purpose of this study was to compare the Cosmed K4b2 portable gas analysis system with the Cosmed Quark b2 metabolic cart. METHODS: Twenty-one subjects attended one testing session that consisted of duplicate measurements of gas volumes and concentrations using both Cosmed gas analysis systems at 3 treadmill work rates; 1) 80m x min(-1), 0% grade, 2) 80m x min(-1), 5% grade, and 3) 80m x min(-1), 10% grade. Subjects walked for 3 min at each rate with one of the gas analysis systems attached to the facemask. The order of the procedures was randomized so that one system was used during both phases (1st or 2nd) of each work rate. RESULTS: The results indicated that oxygen consumption (VO2) was significantly higher in the K4b2 compared to the Quark at 80m x min(-1), 0% grade (14.3+/-1.2 vs 13.6+/-1.2ml x kg(-1) x min(-1), respectively), (p<0.01). The fractional concentration of oxygen in expired air was also significantly lower in the K4b2 at 80 m x min(-1), 0% grade and 80 m x min(-1), 10% grade (p<0.05). There were no significant differences between systems for minute ventilation or carbon dioxide production. Despite the small mean bias in mean VO2 values (0.5-1.0ml x kg-1 x min(-1) higher) in the K4b2, all individual values were within the limits of agreement (mean difference+/-2 SD) as determined by the Bland-Altman technique. CONCLUSION: The findings show a minimal bias in respiratory and metabolic parameters during bi-pedal locomotor activities at low to moderate exercise intensities in the two gas analysis systems.

Effects of early-life exposure to Western diet and wheel access on metabolic syndrome profiles in mice bred for high voluntary exercise.

Experimental studies manipulating diet and exercise have shown varying effects on metabolic syndrome components in both humans and rodents. To examine the potential interactive effects of diet, exercise and genetic background, we studied mice from four replicate lines bred (52 generations) for high voluntary wheel running (HR lines) and four unselected control lines (C). At weaning, animals were housed for 60 days with or without wheels and fed either a standard chow or Western diet (WD, 42% kcal from fat). Four serial (three juvenile and one adult) blood samples were taken to measure fasting total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides and glucose. Western diet was obesogenic for all mice, even after accounting for the amount of wheel running and kilojoules consumed. Western diet significantly raised glucose as well as TC and HDL-C concentrations. At the level of individual variation (repeatability), there was a modest correlation (r = 0.3-0.5) of blood lipids over time, which was reduced with wheel access and/or WD. Neither genetic selection history nor wheel access had a statistically significant effect on blood lipids. However, HR and C mice had divergent ontogenetic trajectories for body mass and caloric intake. HR mice also had lower adiposity, an effect that was dependent on wheel access. The environmental factors of diet and wheel access had pronounced effects on body mass, food consumption and fasting glucose concentrations, interacting with each other and/or with genetic strain. These data underscore the importance (and often unpredictable nature) of genotype-by-environment and environment-by-environment interactions when studying body weight regulation.

Is food insecurity related to overweight and obesity in children and adolescents? A summary of studies, 1995-2009.

In the USA, several nutrition-related issues confront the normal growth, maturation and development of children and adolescents including obesity and food insecurity. The purpose of this paper is to provide a review of the concept of food insecurity and a summary of studies that have examined the association between food insecurity and overweight/obesity in children and adolescents. Besides the initial case report, we review 21 studies (16 cross-sectional and five prospective studies) that have been published on this topic as of December 2009. As there is limited literature in this area, we review studies that sample children and adolescents in the USA. The results are mixed with positive, negative and null associations. The reasons for the mixed results are difficult to disentangle. Among earlier studies, small samples hampered definitive conclusions. More recent studies with larger samples have overcome these limitations and tend to find no associations between these constructs. Nonetheless, all of the studies to date have shown that food insecurity and overweight co-exist - that is, even though there may not be statistically significant differences in overweight between food-insecure and food-secure children, the prevalence of overweight remains relatively high in food-insecure children.