Kate A. Heelan

Associations Between Sedentary Behavior and Blood Pressure in Young Children

OBJECTIVE To examine the effect of sedentary behavior on blood pressure (BP) in young children using different indicators of sedentariness. DESIGN Cross-sectional study. SETTING A rural Midwestern US community. PARTICIPANTS Children aged 3 to 8 years (N = 111). Intervention Adiposity was assessed using dual energy x-ray absorptiometry. Objective measurements of sedentary activity were obtained from the accelerometers that participants wore continuously for 7 days. Measurements of television (TV) viewing, computer, and screen time (TV + computer) were obtained via parent report. MAIN OUTCOME MEASURES Systolic and diastolic BP. RESULTS The sample spent a mean of 5 hours per day in sedentary activities, of which 1.5 hours were screen time. Accelerometer-determined sedentary activity was not significantly related to systolic BP or diastolic BP after controlling for age, sex, height, and percentage of body fat. However, TV viewing and screen time, but not computer use, were positively associated with both systolic BP and diastolic BP after adjusting for potential confounders. Participants in the lowest tertile of TV and screen time had significantly lower levels of systolic and diastolic BP than participants in the upper tertile. CONCLUSIONS Sedentary behaviors, particularly TV viewing and screen time, were associated with BP in children, independent of body composition. Other factors that occur during excessive screen time (eg, food consumption) should also be considered in the context of sedentary behavior and BP development in children.

Physical Activity, Media Time, and Body Composition in Young Children

BACKGROUND It is uncertain as to whether physical activity (PA) may influence the body composition of young children. PURPOSE To determine the association between PA, media time, and body composition in children age 4 to 7 y. METHODS 100 children (52 girls, 48 boys) were assessed for body-mass index (BMI), body fat, fat mass (FM), and fat-free mass using dual energy x-ray absorbtiometryptiometry (DXA). PA was monitored using accelerometers and media time was reported by parental proxy. RESULTS In general, correlations were low to moderate at best (r < 0.51), but in the expected direction. Total media time and TV were significantly associated with BMI (r = 0.51, P < 0.05) and FM (r = 0.29 to 0.30, P < 0.05) in girls. In boys, computer usage was significantly associated with FM in boys (r = 0.31, P < 0.05). CONCLUSION The relatively low correlations suggest that other factors may influence the complex, multi-factorial body composition phenotype of young children.

ACE I/D genotype, adiposity, and blood pressure in children

BackgroundAngiotensin converting enzyme (ACE) is a possible candidate gene that may influence both body fatness and blood pressure. Although several genetic studies have been conducted in adults, relatively few studies have examined the contribution of potential candidate genes, and specifically ACE I/D, on adiposity and BP phenotypes in childhood. Such studies may prove insightful for the development of the obesity-hypertension phenotype early in life. The purpose of this study was to examine differences in body fatness and resting blood pressure (BP) by ACE I/D genotype, and determine if the association between adiposity and BP varies by ACE I/D genotype in children.Methods152 children (75 girls, 77 boys) were assessed for body composition (% body fat) using dual energy x-ray absorbtiometry and resting BP according to American Heart Association recommendations. Buccal cell samples were genotyped using newly developed PCR-RFLP tests for two SNPs (rs4341 and rs4343) in complete linkage disequilibrium with the ACE I/D polymorphism. Partial correlations were computed to assess the ociations between % body fat and BP in the total sample and by genotype. ANCOVA was used to examine differences in resting BP by ACE I/D genotype and fatness groups.ResultsApproximately 39% of youth were overfat based on % body fat (>30% fat in girls, 25% fat in boys). Body mass, body mass index, and fat-free mass were significantly higher in the ACE D-carriers compared to the II group (p < 0.05). BP was not significantly different by ACE I/D genotypes. In the total sample, correlations between adiposity and BP ranged from 0.30 to 0.46, and were not significantly different between genotypes. When grouped by genotype and body fat category, the overfat D-carrier subjects had significantly higher SBP and MAP compared to the normal fat D-carrier and normal fat II groups (p < 0.05).ConclusionACE D-carriers are heavier than ACE II children; however, BP did not differ by ACE I/D genotype but was adversely influenced in the overfat D-carriers. Further studies are warranted to investigate the genetics of fatness and BP phenotypes in children.

Walking to School: Taking Research to Practice.

JOPERD • Volume 79 No. 6 • August 2008 A lthough walking to and from school, up hill both ways, was once the norm among school children in the United States, children’s and parents’ perceptions are different today. Biking and walking to and from school are no longer considered normal activities, as only 23 percent of children ages fi ve to 15 bike or walk to and from school (Toor & Havlick, 2004). To many children, it is normal to load up in the family car, drive a few blocks to wait in line behind dozens of other cars, inching along until they are within a few feet of the school, and then hop out near the front entrance. For parents, this morning routine is usually repeated in the afternoon. Why? Is it safer than letting children walk to school? The vehicle congestion in front of the school caused by this daily routine increases the risk of a vehicle-pedestrian accident and increases neighborhood safety concerns. Unfortunately, this has become “normal.”

Associations between moderate-to-vigorous physical activity and central body fat in 3–8-year-old children

The aim of this study was to examine the associations between objectively measured moderate-to-vigorous physical activity (MVPA) and central body fat (CBF) indicators by anthropometry and dual energy X-ray absorptiometry (DXA) in young children. This study comprised 110 children aged 3-8 years. The associations between MVPA and CBF measures by anthropometry (waist circumference, waist-to-height ratio, skinfold thicknesses [subscapular, suprailiac, trunk-to-extremity and trunk-to-total skinfold ratios] and total trunk-to-waist circumference), DXA (trunk fat) and a combination of both (total trunk skinfolds-to-trunk fat by DXA) were examined by linear regression. Levels of MVPA showed a significant inverse association with 8 of 9 indicators of CBF after controlling for age, gender and height, and fat-free mass. When total fat mass measured by DXA was included into the model, levels of MVPA remained significantly associated with 6 of 9 indicators of CBF. The results highlight the plausible role of MVPA on CBF in young children but longitudinal studies are necessary.

COMPARISON OF ENERGY EXPENDITURE ON A TREADMILL VS. AN ELLIPTICAL DEVICE AT A SELF-SELECTED EXERCISE INTENSITY

Brown, GA, Cook, CM, Krueger, RD, and Heelan, KA. Comparison of energy expenditure on a treadmill vs. an elliptical device at a self-selected exercise intensity. J Strength Cond Res 24(6): 1643-1649, 2010-Treadmills (TM) and elliptical devices (EL) are popular forms of exercise equipment. The differences in the training stimulus presented by TM or EL are unknown. The purpose of this investigation was to evaluate oxygen consumption, energy expenditure, and heart rate on a TM or EL when persons exercise at the same perceived level of exertion. After measuring peak oxygen uptake (&OV0312;O2peak) in 9 male and 9 female untrained college-aged participants, the subjects performed 2 separate 15-minute submaximal exercise tests on the TM and EL at a rating of perceived exertion (RPE) of 12-13. &OV0312;O2peak was higher (p < 0.05) in the males (48.6 ± 1.5 vs. 45.2 ± 1.6 ml/kg/min) than the females (41.7 ± 1.8 vs. 38.8 ± 2.2 ml/kg/min) for both TM and EL (means ± standard error of the mean; for TM vs. EL respectively), but there were no differences in the measured &OV0312;O2peak between TM or EL. During submaximal exercise there were no differences in RPE between TM and EL. Total oxygen consumption was higher (p < 0.05) in males (30.8 ± 2.2 vs. 34.9 ± 2.2 L) than females (24.1 ± 1.8 vs. 26.9 ± 1.7 L) but did not differ between TM and EL. Energy expenditure was not different between TM (569 ± 110 J) or EL (636 ± 120 kJ). Heart rate was higher (p < 0.05) on the EL (164 ± 16 beats/min) compared to the TM (145 ± 15 beats/min). When subjects exercise at the same RPE on TM or EL, oxygen consumption and energy expenditure are similar in spite of a higher heart rate on the EL. These data indicate that during cross training or noncompetition-specific exercise, an elliptical device is an acceptable alternative to a treadmill.

Morning cortisol is not associated with truncal fatness or resting blood pressure in children: cross-sectional and 1-2 year follow-up analyses.

ABSTRACT Objective: To evaluate the cross-sectional and longitudinal relationships of morning cortisol with trunk fat and resting blood pressure (BP) in children. Methods: Participants included 72 children aged 4-10 years (mean 7.4 yrs) for the cross-sectional analysis and 58 for the longitudinal analysis. Height, weight, waist circumference, body fat by dual x-ray absorptiometry, and resting BP measures were obtained during a laboratory visit. Saliva samples were collected at home on a single morning and assayed for cortisol. Results: Approximately 21% were overweight (15.3%) or obese (5.6%). Mean morning cortisol was 0.25 ± 0.12 μg/dL (6.99 ± 3.46 nmol/L). There were no significant correlations between morning cortisol and any of the measures of fatness (r<-0.17) or BP (r<-0.10) at baseline. Cortisol at baseline was not associated with changes in body size parameters after the 1- and 2- year follow-up period. Conclusion: Morning cortisol was not associated with body fatness or BP. Future studies should examine the associations between the diurnal cortisol patterns, trunk fat, and BP by collecting samples throughout an entire day.

Validity of HydraTrend Reagent Strips for the Assessment of Hydration Status

Abstract Abbey, BM, Heelan, KA, Brown, GA, and Bartee, RT. Validity of HydraTrend reagent strips for the assessment of hydration status. J Strength Cond Res 28(9): 2634–2639, 2014—Hydration is used by athletic governing organizations for weight class eligibility. The measurement of urine specific gravity (USG) as a measure of hydration by reagent strips is a controversial issue. The purpose of this study was to determine the validity of HydraTrend reagent strips that facilitate the correction of USG for alkaline urine samples against refractometry for the assessment of USG. Fifty-one participants (33 males, age = 22.3 ± 1.3 years; 18 females, age = 22.4 ± 1.2 years) provided 84 urine samples. The samples were tested for USG using refractometry and reagent strips and for pH using reagent strips and a digital pH meter. Strong correlation coefficients were found between refractometry and reagent strips for USG (rs(82) = 0.812, p < 0.01) and between reagent strips and pH meter for pH (rs(82) = 0.939, p < 0.01). It was observed that false negative results for National Collegiate Athletic Association (NCAA) requirements (fail refractometry with USG >1.020, pass reagent strips with USG ⩽1.020) occurred 39% (33/84) of the time and false negative results for National Federation of State High School Association (NFHS) requirements (fail refractometry with USG >1.025, pass reagent strips with USG ⩽1.025) occurred 14% (12/84) of the time. There were no false positives (pass refractometry and fail reagent strips) for NCAA or NFHS requirements. These data show that refractometry and reagent strips have strong positive correlations. However, the risk of a false negative result leading to incorrect certification of euhydration status outweighs the benefits of the HydraTrend reagent strips for the measurement of USG.

A fitness screening model for increasing fitness assessment and research experiences in undergraduate exercise science students

When students analyze and present original data they have collected, and hence have a cultivated sense of curiosity about the data, student learning is enhanced. It is often difficult to provide students an opportunity to practice their skills, use their knowledge, and gain research experiences during a typical course laboratory. This article describes a model of an out-of-classroom experience during which undergraduate exercise science students provide a free health and fitness screening to the campus community. Although some evidence of the effectiveness of this experience is presented, this is not a detailed evaluation of either the service or learning benefits of the fitness screening. Working in small learning groups in the classroom, students develop hypotheses about the health and fitness of the population to be screened. Then, as part of the health and fitness screening, participants are evaluated for muscular strength, aerobic fitness, body composition, blood pressure, physical activity, and blood cholesterol levels. Students then analyze the data collected during the screening, accept or reject their hypotheses based on statistical analyses of the data, and make in-class presentations of their findings. This learning experience has been used successfully to illustrate the levels of obesity, hypercholesterolemia, and lack of physical fitness in the campus community as well as provide an opportunity for students to use statistical procedures to analyze data. It has also provided students with an opportunity to practice fitness assessment and interpersonal skills that will enhance their future careers.

Calibration of context-specific survey items to assess youth physical activity behaviour.

ABSTRACT This study tests calibration models to re-scale context-specific physical activity (PA) items to accelerometer-derived PA. A total of 195 4th–12th grades children wore an Actigraph monitor and completed the Physical Activity Questionnaire (PAQ) one week later. The relative time spent in moderate-to-vigorous PA (MVPA%) obtained from the Actigraph at recess, PE, lunch, after-school, evening and weekend was matched with a respective item score obtained from the PAQ’s. Item scores from 145 participants were calibrated against objective MVPA% using multiple linear regression with age, and sex as additional predictors. Predicted minutes of MVPA for school, out-of-school and total week were tested in the remaining sample (n = 50) using equivalence testing. The results showed that PAQ β-weights ranged from 0.06 (lunch) to 4.94 (PE) MVPA% (P < 0.05) and models root mean square error ranged from 4.2% (evening) to 20.2% (recess). When applied to an independent sample, differences between PAQ and accelerometer MVPA at school and out-of-school ranged from −15.6 to +3.8 min and the PAQ was within 10–15% of accelerometer measured activity. This study demonstrated that context-specific items can be calibrated to predict minutes of MVPA in groups of youth during in- and out-of-school periods.