An exploratory study of the effects of strenuous exercise on markers of coagulation activation, circulating microparticles, and inflammation in sickle cell trait.

This exploratory study evaluated the effect of intense exercise on biomarkers of inflammation and coagulation activation in subjects with and without sickle cell trait (SCT). Fifteen healthy African American men (18-35 years, 5 SCT, 10 control) completed a strenuous exercise protocol. Microparticle-associated prothrombinase and tissue factor activities, as well as soluble VCAM, total white cell and monocyte count increased transiently in all subjects following exercise. In the SCT group, exercise resulted in increased d-dimer, erythrocyte phosphatidylserine exposure, as well as increased circulating erythrocyte- and endothelial-derived microparticle numbers. These alterations could contribute to exercise-related complications in people with SCT.

Benefits for African American and white low-income 7-10-year-old children and their parents taught together in a community-based weight management program in the rural southeastern United States.

BACKGROUND: Low-income children and parents are at increased risk for developing overweight and obesity. Therefore, the purpose of this exploratory study was to compare whether African American and white children and parents benefitted equally from a community-based weight management intervention delivered in two rural counties in southeastern North Carolina (N.C.). METHODS: We compared the efficacy of the Family Partners for Health intervention for African American and white children and their parents by testing the three-way interaction of the intervention group according to visit and race. RESULTS: African American children in the intervention group weighed significantly (P = 0.027) less than those in the control group, while white children in the intervention group weighed less than those in the control group, but the difference did not reach statistical significance. African American and white parents in the intervention group weighed less than their respective control groups across all three data collections, but the difference was only significant in the group of white parents (P = 0.010) at the completion of the study. At the completion of the study, African American children in the intervention group received significantly (P = 0.003) more support for physical activity than African American children in the control group. At both time points, white children in the intervention group were not significantly different from those in the control group. African American parents in the intervention group scored slightly worse in the stress management assessment compared to those in the control group, while white parents in the intervention group showed a significantly (P = 0.041) better level of stress management than those in the control group. At the completion of the study, African American parents in the intervention group scored somewhat worse in emotional eating self-efficacy compared to the scores of the African American parents in the control group, while white parents in the intervention group scored significantly (P < 0.001) better than those in the control group. CONCLUSIONS: We were successful in affecting some outcomes in both African American and white children and parents using the same intervention. TRIAL REGISTRATION: NCT01378806 Registered June 22, 2011.

Utility of the Youth Compendium of Physical Activities.

PURPOSE: The purposes of this article are to: (a) describe the rationale and development of the Youth Compendium of Physical Activities (Youth Compendium); and (b) discuss the utility of the Youth Compendium for audiences in research, education, community, health care, public health, and the private sector. METHODS: The Youth Compendium provides a list of 196 physical activities (PA) categorized by activity types, specific activities, and metabolic costs (youth metabolic equivalents of task [METy]) as measured by indirect calorimetry. The utility of the Youth Compendium was assessed by describing ways in which it can be used by a variety of audiences. RESULTS: Researchers can use METy values to estimate PA levels and determine changes in PA in intervention studies. Educators can ask students to complete PA records to determine time spent in physical activities and to identify health-enhancing activities for classroom PA breaks. Community leaders, parents, and health care professionals can identify activity types that promote healthful behaviors. Public health agencies can use the METy values for surveillance and as a resource to inform progress toward meeting national physical activity guidelines. Applications for the private sector include the use of METy in PA trackers and other applications. CONCLUSION: The National Collaborative on Childhood Obesity Research Web site presents the Youth Compendium and related materials to facilitate measurement of the energy cost of nearly 200 physical activities in children and youth. The Youth Compendium provides a way to standardize energy costs in children and youth and has application for a wide variety of audiences.

Correction to: A cluster randomized controlled trial for child and parent weight management: children and parents randomized to the intervention group have correlated changes in adiposity.

[This corrects the article DOI: 10.1186/s40608-017-0175-z.].

Ventilatory Responses During Submaximal Exercise in Children With Prader-Willi Syndrome.

PURPOSE: Prader-Willi syndrome (PWS) is a genetic neurobehavioral disorder presenting hypothalamic dysfunction and adiposity. At rest, PWS exhibits hypoventilation with hypercapnia. We characterized ventilatory responses in children with PWS during exercise. METHODS: Participants were children aged 7-12 years with PWS (n = 8) and without PWS with normal weight (NW; n = 9, body mass index ≤ 85th percentile) or obesity (n = 9, body mass index ≥ 95th percentile). Participants completed three 5-minute ambulatory bouts at 3.2, 4.0, and 4.8 km/h. Oxygen uptake, carbon dioxide output, ventilation, breathing frequency, and tidal volume were recorded. RESULTS: PWS had slightly higher oxygen uptake (L/min) at 3.2 km/h [0.65 (0.46-1.01) vs 0.49 (0.34-0.83)] and at 4.8 km/h [0.89 (0.62-1.20) vs 0.63 (0.45-0.97)] than NW. PWS had higher ventilation (L/min) at 3.2 km/h [16.2 (13.0-26.5) vs 11.5 (8.4-17.5)], at 4.0 km/h [16.4 (13.9-27.9) vs 12.7 (10.3-19.5)], and at 4.8 km/h [19.7 (17.4-31.8) vs 15.2 (9.5-21.6)] than NW. PWS had greater breathing frequency (breaths/min) at 3.2 km/h [38 (29-53) vs 29 (22-35)], at 4.0 km/h [39 (29-58) vs 29 (23-39)], and at 4.8 km/h [39 (33-58) vs 32 (23-42)], but similar tidal volume and ventilation/carbon dioxide output to NW. CONCLUSION: PWS did not show impaired ventilatory responses to exercise. Hyperventilation in PWS may relate to excessive neural stimulation and metabolic cost.

Energy Cost Expression for a Youth Compendium of Physical Activities: Rationale for Using Age Groups.

PURPOSE: This study compared the accuracy of physical activity energy expenditure (PAEE) prediction using 2 methods of accounting for age dependency versus 1 standard (single) value across all ages. METHODS: PAEE estimates were derived by pooling data from 5 studies. Participants, 6-18 years (n = 929), engaged in 14 activities while in a room calorimeter or wearing a portable metabolic analyzer. Linear regression was used to estimate the measurement error in PAEE (expressed as youth metabolic equivalent) associated with using age groups (6-9, 10-12, 13-15, and 16-18 y) and age-in-years [each year of chronological age (eg, 12 = 12.0-12.99 y)] versus the standard (a single value across all ages). RESULTS: Age groups and age-in-years showed similar error, and both showed less error than the standard method for cycling, skilled, and moderate- to vigorous-intensity activities. For sedentary and light activities, the standard had similar error to the other 2 methods. Mean values for root mean square error ranged from 0.2 to 1.7 youth metabolic equivalent across all activities. Error reduction ranged from -0.2% to 21.7% for age groups and -0.23% to 18.2% for age-in-years compared with the standard. CONCLUSIONS: Accounting for age showed lower errors than a standard (single) value; using an age-dependent model in the Youth Compendium is recommended.

A Youth Compendium of Physical Activities: Activity Codes and Metabolic Intensities.

PURPOSE: A Youth Compendium of Physical Activities (Youth Compendium) was developed to estimate the energy costs of physical activities using data on youth only. METHODS: On the basis of a literature search and pooled data of energy expenditure measurements in youth, the energy costs of 196 activities were compiled in 16 activity categories to form a Youth Compendium of Physical Activities. To estimate the intensity of each activity, measured oxygen consumption (V˙O2) was divided by basal metabolic rate (Schofield age-, sex-, and mass-specific equations) to produce a youth MET (METy). A mixed linear model was developed for each activity category to impute missing values for age ranges with no observations for a specific activity. RESULTS: This Youth Compendium consists of METy values for 196 specific activities classified into 16 major categories for four age-groups, 6-9, 10-12, 13-15, and 16-18 yr. METy values in this Youth Compendium were measured (51%) or imputed (49%) from youth data. CONCLUSION: This Youth Compendium of Physical Activities uses pediatric data exclusively, addresses the age dependency of METy, and imputes missing METy values and thus represents advancement in physical activity research and practice. This Youth Compendium will be a valuable resource for stakeholders interested in evaluating interventions, programs, and policies designed to assess and encourage physical activity in youth.

A cluster randomized controlled trial for child and parent weight management: children and parents randomized to the intervention group have correlated changes in adiposity.

Background: Studies have suggested that obesity is linked within families and that successful interventions involve both the parent and child with obesity. However little information exists regarding similarities in adiposity and weight loss between the parent and child, especially in low socio-economic ethnically diverse households. Methods: The purpose of this study was to examine the relationships between the changes from baseline over time in adiposity, weight, health behaviors, and self-efficacy in children (n = 184) and parents (n = 184) participating in an 18-month weight loss program. Within the intervention group only and for each post-baseline time point, Pearson correlation coefficients were computed for children's changes (from baseline) in adiposity, weight, health behaviors, and self-efficacy, with their parents' corresponding changes from baseline, to determine how strongly the dyads were correlated. Results: At the completion of 18 months, the intervention group parents demonstrated strong positive correlations between parent and child change in waist circumference (r = 0.409, p < 0.001), triceps (r = 0.332, p < 0.001), and subscapular (r = 0.292, p = 0.002) skinfolds. There were no significant correlations between weight, health behaviors, eating, and exercise self-efficacy. Conclusions: The results suggest that in the Southern United States low-income parents and their children with obesity are strongly correlated. Trial registration: NCT01378806 Retrospectively Registered on June 22, 2011.

Pediatric Exercise Testing: Value and Implications of Peak Oxygen Uptake.

Peak oxygen uptake (peak V ˙ O 2 ) measured by clinical exercise testing is the benchmark for aerobic fitness. Aerobic fitness, estimated from maximal treadmill exercise, is a predictor of mortality in adults. Peak V ˙ O 2 was shown to predict longevity in patients aged 7-35 years with cystic fibrosis over 25 years ago. A surge of exercise studies in young adults with congenital heart disease over the past decade has revealed significant prognostic information. Three years ago, the first clinical trial in children with pulmonary arterial hypertension used peak V ˙ O 2 as an endpoint that likewise delivered clinically relevant data. Cardiopulmonary exercise testing provides clinicians with biomarkers and clinical outcomes, and researchers with novel insights into fundamental biological mechanisms reflecting an integrated physiological response hidden at rest. Momentum from these pioneering observations in multiple disease states should impel clinicians to employ similar methods in other patient populations; e.g., sickle cell disease. Advances in pediatric exercise science will elucidate new pathways that may identify novel biomarkers. Our initial aim of this essay is to highlight the clinical relevance of exercise testing to determine peak V ˙ O 2 , and thereby convince clinicians of its merit, stimulating future clinical investigators to broaden the application of exercise testing in pediatrics.

The influence of physical characteristics on the resting energy expenditure of youth: A meta-analysis.

OBJECTIVE: To examine the literature on resting energy expenditure (REE) of youth and determine the influence of age, sex, BMI, and body composition on REE. METHODS: A literature search was conducted using PubMed, BIOSIS Previews, NTIS, EMBASE, MEDLINE, and Pascal databases for studies with data on resting metabolic rate, REE, resting oxygen uptake (or VO2 ) in healthy children, youth, or adolescents (age = 1-18 years). Over 200 publications were identified; sixty-one publications met criteria and were included in the meta-analyses, resulting in 142 study population estimates (totaling 5,397 youth) of REE. RESULTS: Pooled mean was 1414 kcal·day-1 with a significant and moderate-to-high between-study heterogeneity [Q(140) = 7912.42, P < 0.001; I2 = 98.97%]. A significantly greater (P < 0.001) pooled mean kcal·day-1 was estimated for studies with male participants (1519 kcal·day-1 ) comparing to studies with female participants (1338 kcal·day-1 ). Age, height, and body mass resulted in the highest R2 of 86.4 for males and 83.9% for females. Fat free mass and body mass index (BMI) did not improve total R2 . CONCLUSIONS: These data suggest that using a linear equation including age, height, and body mass to estimate REE based on kcal·day-1 is more accurate than estimates based on body mass kcal·kg-1 ·h-1 . Further, if kcal·kg-1 ·h-1 is used, including a quadratic component for the physical characteristics improves the predictive ability of the equation. Regardless of the metric, separate equations should be used for each sex.

Comparison of Energy Expenditure of Youth Playing Tennis During Practice and Match Settings.

BACKGROUND: Researchers have investigated the energy expenditure of tennis practice and match play in adults but not youth. METHODS: VO2 was recorded for 36 youth, ages 9 to 18, during 10-minute bouts of tennis practice and match play. A GLM was used to compare VO2 between practice and match play and among age groups (9-12 years, 13-15 years, and 16-18 years); also to compare the difference in adult and child-derived MET values (ΔMET). RESULTS: VO2 was higher for tennis match play vs. practice (P < .05) and there was a trend for 16 to 18 year olds having lower VO2 than 9 to 12 year olds (P = .055). ΔMET did not differ between settings but varied by age group (P = .004); it was highest in 9- to 12-year-olds and lowest in 16- to 18-year-olds. CONCLUSIONS: Youth expend more energy while playing a tennis match than practice, regardless of age. Child-derived MET values equaled those of adults once youth reached ages 16 to 18.

Relationships of physical activity and sedentary time in obese parent-child dyads: a cross-sectional study.

BACKGROUND: Research suggests physical activity is linked to obesity. Further, the physical activity of healthy parents and their children is associated with each other. However, this relationship has not been examined in obese parents and their obese children. METHODS: The purpose of this study was to compare the physical activity and sedentary time of obese, low-income, ethnic minority parents and their children on weekdays and weekend days using accelerometry. Data were obtained from eight rural sites in the middle and eastern part of North Carolina (N.C.), United States (U.S.) from 2007-2010 using a rolling enrollment. One hundred and ninety-nine obese parents (94 % female) and their obese children (54 % female) wore accelerometers simultaneously for three weekdays and one weekend day. Total physical activity, moderate-to-vigorous physical activity (MVPA) and sedentary time and proportions were determined. RESULTS: Parents' and children's total physical activity and MVPA levels were lower on weekend days than weekdays. Total counts per minute for children on weekdays and weekend days were greater than for parents (p < 0.001). Total counts per minute were more highly correlated on weekend days than weekdays (r = 0.352, p < 0.0002 versus r = 0.165, p < 0.025). Parents' performed MVPA for 14 (SD = ±25) and 9 (SD = ±16) minutes/day on weekdays and weekend days, respectively; children performed MVPA for 37 (SD = ±25) and 31(SD = ±38) minutes/day for weekdays and weekend days, respectively. Correlations between parents and children for MVPA were higher on weekend days versus weekdays (r = 0.253 and 0.177, respectively; p < 0.015). Associations for sedentary time followed a similar trend, with r = 0.33 (p < 0.0002) for weekend days and r = 0.016 (p < 0.026) for weekdays. Associations between obese parent-child dyads on sedentary time were stronger for girls, while associations between dyads on MVPA were stronger for boys. However, formal interaction analyses were not significant (p > 0.13). DISCUSSION: Since physical activity levels of obese parents and their obese child are somewhat related, especially on weekend days, combined parent-child obesity programs focused on reducing sedentary time could be beneficial, particularly for the child. CONCLUSION: In conclusion, this study of the physical activity levels of obese parents and their obese children found some relationships between the parents' and children's physical activity and sedentary behavior patterns, especially on weekend days. TRIAL REGISTRATION: NCT01378806 .

Exploring Metrics to Express Energy Expenditure of Physical Activity in Youth.

BACKGROUND: Several approaches have been used to express energy expenditure in youth, but no consensus exists as to which best normalizes data for the wide range of ages and body sizes across a range of physical activities. This study examined several common metrics for expressing energy expenditure to determine whether one metric can be used for all healthy children. Such a metric could improve our ability to further advance the Compendium of Physical Activities for Youth. METHODS: A secondary analysis of oxygen uptake (VO2) data obtained from five sites was completed, that included 947 children ages 5 to 18 years, who engaged in 14 different activities. Resting metabolic rate (RMR) was computed based on Schofield Equations [Hum Nutr Clin Nut. 39(Suppl 1), 1985]. Absolute oxygen uptake (ml.min-1), oxygen uptake per kilogram body mass (VO2 in ml.kg-1.min-1), net oxygen uptake (VO2 - resting metabolic rate), allometric scaled oxygen uptake (VO2 in ml.kg-0.75.min-1) and YOUTH-MET (VO2.[resting VO2] -1) were calculated. These metrics were regressed with age, sex, height, and body mass. RESULTS: Net and allometric-scaled VO2, and YOUTH-MET were least associated with age, sex and physical characteristics. For moderate-to-vigorous intensity activities, allometric scaling was least related to age and sex. For sedentary and low-intensity activities, YOUTH-MET was least related to age and sex. CONCLUSIONS: No energy expenditure metric completely eliminated the influence of age, physical characteristics, and sex. The Adult MET consistently overestimated EE. YOUTH-MET was better for expressing energy expenditure for sedentary and light activities, whereas allometric scaling was better for moderate and vigorous intensity activities. From a practical perspective, The YOUTH-MET may be the more feasible metric for improving of the Compendium of Physical Activities for Youth.

A new approach to define and diagnose cardiometabolic disorder in children.

The aim of the study was to test the performance of a new definition of metabolic syndrome (MetS), which better describes metabolic dysfunction in children. Methods. 15,794 youths aged 6-18 years participated. Mean z-score for CVD risk factors was calculated. Sensitivity analyses were performed to evaluate which parameters best described the metabolic dysfunction by analysing the score against independent variables not included in the score. Results. More youth had clustering of CVD risk factors (>6.2%) compared to the number selected by existing MetS definitions (International Diabetes Federation (IDF) < 1%). Waist circumference and BMI were interchangeable, but using insulin resistance homeostasis model assessment (HOMA) instead of fasting glucose increased the score. The continuous MetS score was increased when cardiorespiratory fitness (CRF) and leptin were included. A mean z-score of 0.40-0.85 indicated borderline and above 0.85 indicated clustering of risk factors. A noninvasive risk score based on adiposity and CRF showed sensitivity and specificity of 0.85 and an area under the curve of 0.92 against IDF definition of MetS. Conclusions. Diagnosis for MetS in youth can be improved by using continuous variables for risk factors and by including CRF and leptin.

Impact of Acute Intermittent Exercise on Natural Killer Cells in Breast Cancer Survivors.

BACKGROUND: Current research examining the effect of exercise on immune responses in cancer survivors is limited. OBJECTIVE: The aim of this pilot study was to examine the effect of 1 bout of intermittent exercise on natural killer (NK) cell numbers in breast cancer survivors. METHODS: A total of 9 women with stage I to III invasive breast cancer who were 3 to 6 months posttreatment and 9 sedentary women without a history of cancer completed 10 three-minute intervals of aerobic exercise on the cycle ergometer at 60% of VO2peak (peak oxygen uptake). Whole blood samples were taken pre-exercise, immediately postexercise, and at 2 hours and 24 hours postexercise. NK cell counts were assessed using flow cytometry. RESULTS: In both groups, NK cell counts significantly increased immediately postexercise compared with pre-exercise (P = .004-.008) and returned to near pre-exercise levels during recovery (P = .129-.547). Absolute NK cell counts were significantly lower in breast cancer survivors immediately postexercise when compared with controls (P = .046). CONCLUSIONS: The breast cancer survivor group exhibited NK cell responses to 30 minutes of moderate-intensity intermittent aerobic exercise that were comparable with that in the group of physically similar women without a history of cancer. Immune changes related to cancer treatments may be related to the lower absolute NK cell counts observed in the breast cancer survivor group. Although the results of this study are preliminary in nature, they suggest that this type of exercise does not disrupt this aspect of innate immunity in recent breast cancer survivors, thereby supporting current exercise recommendations for this population.

Accelerometer-measured sedentary time among Hispanic adults: Results from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL).

Excessive sedentary behavior is associated with negative health outcomes independent of physical activity. Objective estimates of time spent in sedentary behaviors are lacking among adults from diverse Hispanic/Latino backgrounds. The objective of this study was to describe accelerometer-assessed sedentary time in a large, representative sample of Hispanic/Latino adults living in the United States, and compare sedentary estimates by Hispanic/Latino background, sociodemographic characteristics and weight categories. This study utilized baseline data from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) that included adults aged 18-74 years from four metropolitan areas (N = 16,415). Measured with the Actical accelerometer over 6 days, 76.9% (n = 12,631) of participants had > 10 h/day and > 3 days of data. Participants spent 11.9 h/day (SD 3.0), or 74% of their monitored time in sedentary behaviors. Adjusting for differences in wear time, adults of Mexican background were the least (11.6 h/day), whereas adults of Dominican background were the most (12.3 h/day), sedentary. Women were more sedentary than men, and older adults were more sedentary than younger adults. Household income was positively associated, whereas employment was negatively associated, with sedentary time. There were no differences in sedentary time by weight categories, marital status, or proxies of acculturation. To reduce sedentariness among these populations, future research should examine how the accumulation of various sedentary behaviors differs by background and region, and which sedentary behaviors are amenable to intervention.

Cardiometabolic risk assessments by body mass index z-score or waist-to-height ratio in a multiethnic sample of sixth-graders.

Convention defines pediatric adiposity by the body mass index z-score (BMIz) referenced to normative growth charts. Waist-to-height ratio (WHtR) does not depend on sex-and-age references. In the HEALTHY Study enrollment sample, we compared BMIz with WHtR for ability to identify adverse cardiometabolic risk. Among 5,482 sixth-grade students from 42 middle schools, we estimated explanatory variations (R (2)) and standardized beta coefficients of BMIz or WHtR for cardiometabolic risk factors: insulin resistance (HOMA-IR), lipids, blood pressures, and glucose. For each risk outcome variable, we prepared adjusted regression models for four subpopulations stratified by sex and high versus lower fatness. For HOMA-IR, R (2) attributed to BMIz or WHtR was 19%-28% among high-fatness and 8%-13% among lower-fatness students. R (2) for lipid variables was 4%-9% among high-fatness and 2%-7% among lower-fatness students. In the lower-fatness subpopulations, the standardized coefficients for total cholesterol/HDL cholesterol and triglycerides tended to be weaker for BMIz (0.13-0.20) than for WHtR (0.17-0.28). Among high-fatness students, BMIz and WHtR correlated with blood pressures for Hispanics and whites, but not black boys (systolic) or girls (systolic and diastolic). In 11-12 year olds, assessments by WHtR can provide cardiometabolic risk estimates similar to conventional BMIz without requiring reference to a normative growth chart.

Examining variations of resting metabolic rate of adults: a public health perspective.

PURPOSE: There has not been a recent comprehensive effort to examine existing studies on the resting metabolic rate (RMR) of adults to identify the effect of common population demographic and anthropometric characteristics. Thus, we reviewed the literature on RMR (kcal·kg(-1)·h(-1)) to determine the relationship of age, sex, and obesity status to RMR as compared with the commonly accepted value for the metabolic equivalent (MET; e.g., 1.0 kcal·kg(-1)·h(-1)). METHODS: Using several databases, scientific articles published from 1980 to 2011 were identified that measured RMR, and from those, others dating back to 1920 were identified. One hundred and ninety-seven studies were identified, resulting in 397 publication estimates of RMR that could represent a population subgroup. Inverse variance weighting technique was applied to compute means and 95% confidence intervals (CI). RESULTS: The mean value for RMR was 0.863 kcal·kg(-1)·h(-1) (95% CI = 0.852-0.874), higher for men than women, decreasing with increasing age, and less in overweight than normal weight adults. Regardless of sex, adults with BMI ≥ 30 kg·m(-2) had the lowest RMR (<0.741 kcal·kg(-1)·h(-1)). CONCLUSIONS: No single value for RMR is appropriate for all adults. Adhering to the nearly universally accepted MET convention may lead to the overestimation of the RMR of approximately 10% for men and almost 15% for women and be as high as 20%-30% for some demographic and anthropometric combinations. These large errors raise questions about the longstanding adherence to the conventional MET value for RMR. Failure to recognize this discrepancy may result in important miscalculations of energy expended from interventions using physical activity for diabetes and other chronic disease prevention efforts.

Insights into physical activity and cardiovascular disease risk in young children: IDEFICS study.

The association between physical activity and cardiovascular disease risk factors in children has been the focus of research for over two decades. The majority of this research has focused on children over 10 years of age with little information on very young children. The data recently published in BMC Medicine by Jiménez-Pavón and colleagues suggest that adverse cardiovascular disease (CVD) risk profiles, as indicated by a clustered risk score for the metabolic syndrome, are evident in very young children (two to six years of age), but differ between the sexes. The authors evaluated the relationship of CVD risk profiles and protective levels of moderate-to-vigorous physical activity (MVPA) and concluded that boys aged six years or younger needed >60 minutes of MVPA per day, whereas boys from six to nine years of age needed >80 minutes of MVPA per day; girls in either age group needed approximately 15 minutes less. Therefore, when clinicians recommend physical activity for children they should evaluate "at risk" children on a case-by-case basis rather than using generalized guidelines.

BMI change, fitness change and cardiometabolic risk factors among 8th grade youth.

This paper examined whether a two-year change in fitness, body mass index (BMI) or the additive effect of change in fitness and BMI were associated with change in cardiometabolic risk factors among youth. Cardiometabolic risk factors, BMI group (normal weight, overweight or obese) were obtained from participants at the start of 6th grade and end of 8th grade. Shuttle run laps were assessed and categorized in quintiles at both time points. Regression models were used to examine whether changes in obesity, fitness or the additive effect of change in BMI and fitness were associated with change in risk factors. There was strong evidence (p < .001) that change in BMI was associated with change in cardiometabolic risk factors. There was weaker evidence of a fitness effect, with some evidence that change in fitness was associated with change in total cholesterol, HDL-C, LDL-C and clustered risk score among boys, as well as HDL-C among girls. Male HDL-C was the only model for which there was some evidence of a BMI, fitness and additive BMI*fitness effect. Changing body mass is central to the reduction of youth cardiometabolic risk. Fitness effects were negligible once change in body mass had been taken into account.