Randal P. Claytor

Dietary patterns associated with fat and bone mass in young children

BACKGROUND Obesity and osteoporosis have origins in childhood, and both are affected by dietary intake and physical activity. However, there is little information on what constitutes a diet that simultaneously promotes low fat mass and high bone mass accrual early in life. OBJECTIVE Our objective was to identify dietary patterns related to fat and bone mass in children during the age period of 3.8-7.8 y. DESIGN A total of 325 children contributed data from 13 visits over 4 separate study years (age ranges: 3.8-4.8, >4.8-5.8, >5.8-6.8, and >6.8-7.8 y). We performed reduced-rank regression to identify dietary patterns related to fat mass and bone mass measured by dual-energy X-ray absorptiometry for each study year. Covariables included race, sex, height, weight, energy intake, calcium intake, physical activity measured by accelerometry, and time spent viewing television and playing outdoors. RESULTS A dietary pattern characterized by a high intake of dark-green and deep-yellow vegetables was related to low fat mass and high bone mass; high processed-meat intake was related to high bone mass; and high fried-food intake was related to high fat mass. Dietary pattern scores remained related to fat mass and bone mass after all covariables were controlled for (P < 0.001-0.03). CONCLUSION Beginning at preschool age, diets rich in dark-green and deep-yellow vegetables and low in fried foods may lead to healthy fat and bone mass accrual in young children.

Adiposity and TV viewing are related to less bone accrual in young children

OBJECTIVE To examine the relation between baseline fat mass and gain in bone area and bone mass in preschoolers studied prospectively for 4 years, with a focus on the role of physical activity and TV viewing. STUDY DESIGN Children were part of a longitudinal study in which measures of fat, lean and bone mass, height, weight, activity, and diet were taken every 4 months from ages 3 to 7 years. Activity was measured by accelerometer and TV viewing by parent checklist. We included 214 children with total body dual energy x-ray absorptiometry (Hologic 4500A) scans at ages 3.5 and 7 years. RESULTS Higher baseline fat mass was associated with smaller increases in bone area and bone mass over the next 3.5 years (P < .001). More TV viewing was related to smaller gains in bone area and bone mass accounting for race, sex, and height. Activity by accelerometer was not associated with bone gains. CONCLUSIONS Adiposity and TV viewing are related to less bone accrual in preschoolers.

Cardiovascular physiology during supine cycle ergometry and dobutamine stress.

PURPOSE This study compared cardiac hemodynamics during supine cycle ergometry and dobutamine stress. METHODS Thirty-two healthy volunteers (19 female, 13 male, 23.5 +/- 3.5 yr old) completed respective tests on separate days and in random order. Heart rate, blood pressure, and cardiac output were recorded at baseline and peak stress. Echocardiographic measures included left ventricular end-diastolic dimension, fractional shortening, heart rate corrected velocity of circumferential fiber shortening, end-systolic wall stress, and the difference between measured and predicted fiber shortening for measured wall stress. RESULTS Compared with peak exercise, dobutamine infusion resulted in lower cardiac output (12 +/- 2 vs 16 +/- 4 l x min(-1), P < 0.0001), heart rates (163 +/- 7 vs 175 +/- 12 beats x min(-1), P < 0.0001), and systolic blood pressure (160 +/- 22 vs 185 +/- 20 mm Hg, P < or = 0.0001). Echocardiography demonstrated smaller left ventricular end-diastolic dimension (4.2 +/- 0.7 vs 4.5 +/- 0.7 cm, P = 0.013), higher fractional shortening (0.55 +/- 0.07 vs 0.50 +/- 0.06%, P < 0.001), higher VCFc (2.07 +/- 0.36 vs 1.54 +/- 0.20 circs x s(-1), P < 0.001) higher VCFdiff (0.94 +/- 0.35 vs 0.48 +/- 0.20 circs x s(-1), P < 0.001), and lower end-systolic wall stress (25 +/- 11 vs 42 +/- 16 g x cm(-2), P < 0.001). The stress-velocity relationship during dobutamine demonstrated higher y-intercept and steeper slope, indicating greater load-independent contractility. CONCLUSION The cardiovascular adaptation to exercise and dobutamine stress differ significantly. Cardiac output during peak exercise is greater than during peak dobutamine secondary to increased heart rate and stroke volume. Despite a greater increase in contractility and decrease in afterload, a smaller increase in cardiac output during dobutamine stress may be secondary to limited ventricular preload.

Exercise Capacity Improves after Transcatheter Closure of the Fontan Fenestration in Children

OBJECTIVES This study evaluated the aerobic capacity, exercise capacity, and arterial oxygen saturation (O(2)Sat) in children before and after transcatheter Fontan fenestration closure. DESIGN Observational study comparing exercise parameters and hemodynamics before and after transcatheter fenestration closure in Fontan patients. OUTCOME MEASURES Working capacity, exercise duration, oxygen consumption (VO(2)), and arterial O(2)Sat were evaluated during aerobic exercise. RESULTS Twenty patients (mean age 11.4 years) underwent standardized exercise testing before and after fenestration closure. Twelve patients underwent cycle ergometry testing (mean age 14.8 years) (group 1), and eight younger patients (mean age 6.4 years) underwent Bruce treadmill testing (group 2). The same exercise protocol was used in each patient before and after fenestration closure (interval between tests: 118 +/- 142 days). Immediately following fenestration closure at cardiac catheterization, cardiac index decreased (3.0 to 2.1 L/minute/m(2)) and Fontan pressure increased (11 +/- 2 to 12 +/- 2 mm Hg) with an increased arterial saturation (92 to 96%) (P < .001). The total group demonstrated no significant change in pre- and postclosure maximal heart rates (164 +/- 21 and 169 +/- 19 bpm). Rest and exercise O(2)Sat increased (89 and 82 to 95 and 92%) (P < .0001). Exercise duration increased (7.7 +/- 1.9 to 9.2 +/- 2.4 minutes) (P < .0005). Maximal VO(2), indexed maximal VO(2), and total working capacity in kilopond-meters (kpm) increased (1.2 +/- 0.5, 27 +/- 7 and 2466 +/- 1012 to 1.3 +/- 0.4 L/minute, 31 +/- 9 mL/kg/minute and 2869 +/- 1051 kpm, respectively) (P < .005). CONCLUSION In children with a univentricular heart after Fontan palliation, transcatheter fenestration closure improves exercise arterial O(2)Sat and aerobic capacity despite a restricted resting cardiac output documented by catheterization immediately after the closure procedure.

Body Fat has No Effect on the Maximal Fat Oxidation Rate in Young, Normal, and Overweight Women

Abstract Blaize, AN, Potteiger, JA, Claytor, RP, and Noe, DA. Body fat has no effect on the maximal fat oxidation rate in young normal and overweight women. J Strength Cond Res 28(8): 2121–2126, 2014—The purpose of this study was to examine how fat mass affects the maximal fat oxidation rates of women. Fourteen active, healthy women (age, 21–31 years) with body composition ranging from 18.6 to 30.0% fat were divided into 2 groups (15–24.9% = lower-fat group; 25–35% = higher-fat group). On day 1, subjects performed a graded exercise test on the treadmill to determine maximal oxygen consumption (V[Combining Dot Above]O2max). On day 2, subjects were measured for % fat and performed a maximal fat oxidation test. Fat and carbohydrate oxidation rates were determined using gas exchange analysis. Fat oxidation in absolute (in gram per minute) and relative to fat-free body mass (in milligram per kilogram of fat-free mass per minute) was determined using stoichiometric equations and appropriate energy equivalents. There were no significant differences (p > 0.05) in maximal fat oxidation rates between the women in lower-fat (0.39 ± 0.10 g·min−1, 8.52 ± 2.69 mg·kg−1 FFM·min−1) and higher-fat (0.49 ± 0.13 g·min−1, 10.81 ± 2.80 mg·kg−1 FFM·min−1) groups. Maximal fat oxidation occurred at an exercise intensity of 55.7 ± 11.1% and 59.1 ± 5.4% V[Combining Dot Above]O2max for the lower-fat and higher-fat groups, respectively, with no significant difference between groups (p > 0.05). The maximal fat oxidation rate (g·min−1 and mg·kg−1 FFM·min−1) was not significantly correlated with any of the descriptive variables (fat mass, fat-free mass, percent body fat, or V[Combining Dot Above]O2max). In conclusion, personal trainers and health practitioners can use the exercise intensities that elicited the highest rate of fat oxidation to prescribe exercise programs to women, despite their body composition, that prevent weight gain and/or promote body fat and body weight loss.

Effects of different meal compositions after exercise on fat and carbohydrate oxidation in women with different levels of body fat

We investigated the effects of consuming a high-carbohydrate meal (HC), high-fat meal (HF), or no meal (CON) following exercise on fat and carbohydrate oxidation (FAT-OX, CHO-OX) in women with differing levels of body fat. Healthy, physically active females were divided into a Lower Fat (<25% fat, n = 10) or Higher Fat (>25% fat, n = 9) group and tested on 4 occasions. During session 1, body composition and maximal oxygen consumption were determined. During 3 treatment sessions, subjects preformed treadmill exercise at 55% of maximal oxygen consumption until 350 kcal were expended. At 10 min postexercise subjects consumed a liquid meal standardized to provide energy equal to 20% of 24-h energy expenditure plus the 350 kcal of exercise. The HC meal comprised 64% carbohydrate, 21.6% fat, and 14.4% protein. The HF meal comprised 24% carbohydrate, 62% fat, and 14% protein. CON consisted of water equal to the meal volume. During exercise and 2 h postexercise, expired gases were collected to determine FAT-OX and CHO-OX. During exercise CHO-OX was a significantly higher for the Lower Fat group and FAT-OX was significantly higher for the Lower Fat group for each of the meal conditions. A significant difference was observed across meals (p < 0.05) for CHO-OX (first hour) and for CHO-OX and FAT-OX (second hour) postexercise. There were no significant differences (p > 0.05) between the Lower Fat and Higher Fat groups for either recovery period. In physically active females, the macronutrient composition of the postexercise meal affects substrate oxidation, but the level of body fat does not.