Katrina D. DuBose

Blood Lipid and Lipoprotein Adaptations to Exercise A Quantitative Analysis

Dose-response relationships between exercise training volume and blood lipid changes suggest that exercise can favourably alter blood lipids at low training volumes, although the effects may not be observable until certain exercise thresholds are met. The thresholds established from cross-sectional literature occur at training volumes of 24 to 32km (15 to 20 miles) per week of brisk walking or jogging and elicit between 1200 to 2200 kcal/wk. This range of weekly energy expenditure is associated with 2 to 3 mg/dl increases in high-density lipoprotein- cholestrol (HDL-C) and triglyceride (TG) reductions of 8 to 20 mg/dl. Evidence from cross-sectional studies indicates that greater changes in HDL-C levels can be expected with additional increases in exercise training volume. HDL-C and TG changes are often observed after training regimens requiring energy expenditures similar to those characterised from cross-sectional data. Training programmes that elicit 1200 to 2200 kcal/wk in exercise are often effective at elevating HDL-C levels from 2 to 8 mg/dl, and lowering TG levels by 5 to 38 mg/dl. Exercise training seldom alters total cholesterol (TC) and low-density lipoprotein-cholesterol (LDLC). However, this range of weekly exercise energy expenditure is also associated with TC andLDL-C reductions when they are reported. The frequency and extent to which most of these lipid changes are reported are similar in both genders, with the exception of TG. Thus, for most individuals, the positive effects of regular exercise are exerted on blood lipids at low training volumes and accrue so that noticeable differences frequently occur with weekly energy expenditures of 1200 to 2200 kcal/wk. It appears that weekly exercise caloric expenditures that meet or exceed the higher end of this range are more likely to produce the desired lipid changes. This amount of physical activity, performed at moderate intensities, is reasonable and attainable for most individuals and is within the American College of Sports Medicine’s currently recommended range for healthy adults.

Physical Activity Across the Curriculum (PAAC): a randomized controlled trial to promote physical activity and diminish overweight and obesity in elementary school children

BACKGROUND Physical Activity Across the Curriculum (PAAC) was a three-year cluster randomized controlled trial to promote physical activity and diminish increases in overweight and obesity in elementary school children. METHODS Twenty-four elementary schools were cluster randomized to the Physical Activity Across the Curriculum intervention or served as control. All children in grades two and three were followed to grades four and five. Physical Activity Across the Curriculum promoted 90 min/wk of moderate to vigorous intensity physically active academic lessons delivered by classroom teachers. Body Mass Index was the primary outcome, daily Physical activity and academic achievement were secondary outcomes. RESULTS The three-year change in Body Mass Index for Physical Activity Across the Curriculum was 2.0+/-1.9 and control 1.9+/-1.9, respectively (NS). However, change in Body Mass Index from baseline to 3 years was significantly influenced by exposure to Physical Activity Across the Curriculum. Schools with > or =75 min of Physical Activity Across the Curriculum/wk showed significantly less increase in Body Mass Index at 3 years compared to schools that had <75 min of Physical Activity Across the Curriculum (1.8+/-1.8 vs. 2.4+/-2.0, p=0.02). Physical Activity Across the Curriculum schools had significantly greater changes in daily Physical activity and academic achievement scores. CONCLUSIONS The Physical Activity Across the Curriculum approach may promote daily Physical activity and academic achievement in elementary school children. Additionally, 75 min of Physical Activity Across the Curriculum activities may attenuate increases in Body Mass Index.

Cardiorespiratory fitness and C-reactive protein among a tri-ethnic sample of women

Background—Elevated C-reactive protein (CRP) is associated with increased coronary heart disease (CHD) risk. Cardiorespiratory fitness (“fitness”) is related with lower CHD risk; however, its relationship with CRP is relatively unknown. Methods and Results—Cross-sectional associations between fitness and plasma CRP were examined among 135 African American (AA), Native American (NA), and Caucasian (CA) women (55±11 year; 28±6 kg/m2). Fitness was assessed with a maximal treadmill exercise test. Plasma CRP concentrations were determined with the Dade Behring high-sensitivity immunoassay. Geometric mean CRP levels were 0.43, 0.25, and 0.23 mg/dL, and average maximal MET levels of fitness were 7.2, 9.1, and 10 METs for AA, NA, and CA, respectively. CRP decreased across tertiles of fitness (P =0.002), increased across tertiles of BMI (P =0.0007), and varied by race (P =0.002). After adjustment for covariates, lower CRP (P <0.05) was observed across tertiles of fitness among NA and CA, but not AA. Among all women, after adjusting for race and covariates, the odds of high-risk CRP (>0.19 mg/dL) were 0.67 (95% CI=0.19 to 2.4) among fit (>6.5 METs) versus unfit women. Conclusions—The health benefits from enhanced fitness may have an antiinflammatory mechanism.

Aerobic Fitness Attenuates the Metabolic Syndrome Score in Normal-Weight, at-Risk-for-Overweight, and Overweight Children

OBJECTIVE. The purpose of this study was to examine the combined influence of aerobic fitness and BMI on the metabolic syndrome score in children. METHODS. A total of 375 children (193 girls and 182 boys) aged 7 to 9 years were categorized as being normal weight, at risk for overweight, and overweight on the basis of BMI and aerobic fitness (high or low based on median split) via a submaximal physical working capacity test. Participants were cross-tabulated into 6 BMI fitness categories. High-density lipoprotein cholesterol and triglyceride levels, homeostasis assessment model of insulin resistance, mean arterial pressure, and waist circumference were used to create a continuous metabolic syndrome score. RESULTS. Both BMI and fitness were associated with the metabolic syndrome score. In general, the metabolic syndrome score increased across the cross-tabulated groups with the normal-weight, high-fit group possessing the lowest metabolic syndrome score and the overweight, unfit group possessing the highest metabolic syndrome score. Children who were at risk for overweight and had high fitness had a lower metabolic syndrome score compared with those at-risk-for-overweight, less-fit children, and the score was similar to that of the less-fit, normal-weight children. Furthermore, a high fitness level resulted in a lower metabolic syndrome score in overweight children compared with overweight children with low fitness. CONCLUSIONS. High fitness levels modified the impact that BMI had on the metabolic syndrome score in children. Increasing a childs fitness level could be one method for reducing the risk of obesity-related comorbidities.

Physical activity across the curriculum: year one process evaluation results

BackgroundPhysical Activity Across the Curriculum (PAAC) is a 3-year elementary school-based intervention to determine if increased amounts of moderate intensity physical activity performed in the classroom will diminish gains in body mass index (BMI). It is a cluster-randomized, controlled trial, involving 4905 children (2505 intervention, 2400 control).MethodsWe collected both qualitative and quantitative process evaluation data from 24 schools (14 intervention and 10 control), which included tracking teacher training issues, challenges and barriers to effective implementation of PAAC lessons, initial and continual use of program specified activities, and potential competing factors, which might contaminate or lessen program effects.ResultsOverall teacher attendance at training sessions showed exceptional reach. Teachers incorporated active lessons on most days, resulting in significantly greater student physical activity levels compared to controls (p < 0.0001). Enjoyment ratings for classroom-based lessons were also higher for intervention students. Competing factors, which might influence program results, were not carried out at intervention or control schools or were judged to be minimal.ConclusionIn the first year of the PAAC intervention, process evaluation results were instrumental in identifying successes and challenges faced by teachers when trying to modify existing academic lessons to incorporate physical activity.

Construct validity of a continuous metabolic syndrome score in children.

ObjectiveThe primary purpose of this study was to examine the construct validity of a continuous metabolic syndrome score (cMetS) in children. The secondary purpose was to identify a cutpoint value(s) for an adverse cMetS based on receiver operating characteristic (ROC) curve analysis.Methods378 children aged 7 to 9 years were assessed for the metabolic syndrome which was determined by age-modified cutpoints. High-density-lipoprotein cholesterol, triglycerides, the homeostasis assessment model of insulin resistance, mean arterial pressure, and waist circumference were used to create a cMetS for each subject.ResultsAbout half of the subjects did not possess any risk factors while about 5% possessed the metabolic syndrome. There was a graded relationship between the cMetS and the number of adverse risk factors. The cMetS was lowest in the group with no adverse risk factors (-1.59 ± 1.76) and highest in those possessing the metabolic syndrome (≥3 risk factors) (7.05 ± 2.73). The cutoff level yielding the maximal sensitivity and specificity for predicting the presence of the metabolic syndrome was a cMetS of 3.72 (sensitivity = 100%, specificity = 93.9%, and the area of the curve = 0.978 (0.957-0.990, 95% confidence intervals).ConclusionThe results demonstrate the construct validity for the cMetS in children. Since there are several drawbacks to identifying a single cut-point value for the cMetS based on this sample, we urge researchers to use the approach herein to validate and create a cMetS that is specific to their study population.

Nonoccupational physical activity by degree of urbanization and U.S. geographic region

PURPOSE To estimate levels of nonoccupational leisure-time physical activity (LTPA) by degree of urbanization and geographic region of the United States. METHODS Participants were respondents to the Behavioral Risk Factor Surveillance System (BRFSS) in 2001 (N = 137,359). Moderate- and vigorous-intensity LTPA was categorized as meeting recommended levels, insufficient, or inactive. The U.S. Department of Agriculture rural-urban continuum codes were used to describe degrees of urbanization (metro, large urban, small urban, and rural). Geographic regions were defined by the U.S. Bureau of the Census (Northeast, Midwest, South, and West). Prevalence estimates were calculated using sample weights to account for the design of the BRFSS. Multivariate logistic regression analyses examined regional differences in the odds of physical inactivity (physically inactive vs insufficient or meets) by degree of urbanization after adjustment for sex, age, race, BMI, education, and occupational physical activity. RESULTS Large urban areas (49.0%) and the western United States (49.0%) had the highest prevalence of recommended levels of LTPA. Rural areas (24.1%) and the southern United States (17.4%) had the highest prevalence of inactivity. Adults living in the four urbanization categories of the midwestern (metro (OR = 1.47, 95% CI = 1.31, 1.65), large urban (OR = 1.83, 95% CI = 1.51, 2.23), small urban (OR = 1.99, 95% CI = 1.65, 2.40), and rural (OR = 2.59, 95% CI = 1.35, 4.97)); and southern (metro (OR = 1.70, 95% CI = 1.53, 1.88), large urban (OR = 2.04, 95% CI = 1.72, 2.41), small urban (OR = 2.32, 95% CI = 2.02, 2.67), and rural (OR = 5.49, 95% CI = 2.82, 10.68)) U.S. regions were more likely to be inactive than adults living in similar areas of the western United States. Adults in northeast metro and large urban areas (OR = 1.62, 95% CI = 1.45, 1.81; and OR = 1.37, 95% CI = 1.08, 1.74, respectively) were more likely to be inactive than those residing in western metro and large urban areas. CONCLUSION The prevalence of physical inactivity varies by degree of urbanization and geographic region of the United States.

Prevalence of the metabolic syndrome in elementary school children

Aim: To determine the prevalence of the metabolic syndrome (MS) and its related components in elementary‐aged school children. Methods: Three hundred and seventy‐five 7–9‐y‐old boys (n=182) and girls (n=193) in the eastern Kansas area served as participants. Criteria for the MS were the presence of three or more of the following components: 1) central obesity (waist circumference ≥90th percentile in males and females); 2) elevated triglyceride concentrations (≥1.13 mmol/l); 3) low HDL‐C concentrations (≤1.04 mmol/l in males and females); 4) elevated blood pressure (systolic and/or diastolic ≥90th percentile, age and gender specific); or 5) elevated fasting glucose levels (≥6.10 mmol/l). Results: The prevalence of the MS in this sample was 5%, and was similar across gender and race. Fifty percent of the children had no components and 15% had at least two components, with elevated blood pressure the most common component (37%).

Walking Patterns in a Sample of African American, Native American, and Caucasian Women: The Cross-Cultural Activity Participation Study:

This analysis describes walking patterns among African American, Native American, and Caucasian women from South Carolina and New Mexico. Walking was assessed using pedometer and physical activity (PA) record data based on 4 consecutive days on either three (Study Phase 1) or two (Study Phase 2) occasions. Participants walked 5,429 ± 2,959 steps per day and recorded 159 ± 59 minutes per day of total walking in the PA record. Most daily walking was accumulated during household (46%), transportation (26%), occupation (16%), and exercise-related (10%) walking. There was a modest correlation between steps per day and minutes per day. Steps per day were higher with education and household size, and lower with increasing age and body mass index. These findings have implications for developing PA surveys and for planning interventions related to walking patterns among women.

Fatness, fitness, and insulin sensitivity among 7- to 9-year-old children.

Objective: The purpose of this study was to examine the relationships among fatness and aerobic fitness on indices of insulin resistance and sensitivity in children.