Body fat has no effect on the maximal fat oxidation rate in young, normal, and overweight women.

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 (VO2max). 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 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% VO2max 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 VO2max). 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.

Tracking of accelerometer-measured physical activity in early childhood.

Establishing and maintaining healthy physical activity (PA) levels is important throughout life. The purpose of this study was to determine the extent of PA tracking between ages 3 and 7 y. Objective measures of PA (RT3, triaxial accelerometer) were collected every 4 mo from ages 3-7; data from 234 children with PA measures available during each year of age were analyzed. Mean PA (total, moderate/vigorous (MV), and inactivity [IA]) was calculated for each year of age and adjusted for wear time. Correlations with age 3 PA were moderate at age 4 (r = .42-.45) but declined by age 7 (r = .19-.25). After classification into sex-specific tertiles of PA at age 3, boys in the high age 3 MVPA tertile maintained significantly higher PA at all subsequent ages, while girls in the high age 3 MVPA tertile were not significantly higher at age 6 and 7. Boys and girls in the high age 3 IA tertile had significantly higher IA at multiple subsequent years of age (p < .05 at ages 5 and 6). In conclusion, boys who were relatively more active at age 3 remained more active for several subsequent years. These findings highlight early-childhood differences in physical activity patterns between boys and girls.

Prevalence of metabolic syndrome risk factors in high school and NCAA division I football players.

Metabolic syndrome (MetSyn) is a clustering of metabolic and cardiovascular disease risk factors. The purpose of this study was to determine the prevalence of MetSyn risk factors in high school (HS) and college (College) football players and to examine if the prevalence varied according to body fat percent (%Fat). One hundred twenty-three males (height 179.0 ± 6.7 cm; weight 89.4 ± 19.6 kg) from 7 different high schools and 82 males (height 186.2 ± 6.8 cm; weight 99.6 ± 16.8 kg) from one university participated. All testing occurred in the early morning after an overnight fast. %Fat, waist circumference, resting systolic and diastolic blood pressure, fasting triglyceride, high-density lipoprotein (HDL) cholesterol, and blood glucose were determined using standard testing procedures. The MetSyn risk factor levels were determined using American Heart Association criteria. Subjects were grouped by position and playing level (HS, College). Independent t-tests, chi-square analysis, 2-way analysis of variance, and path analytic models were used in the statistical analysis. Significance was set at p < 0.05. 6.8% (n = 14) of the sample met the American Heart Association criteria for MetSyn. Offensive and defensive linemen accounted for 92.3% of the players meeting MetSyn criteria with each playing level (HS, College) having 7 subjects. The MetSyn criteria differed significantly across %Fat. Obese players were more likely to meet the criteria for MetSyn. %Fat was a statistically significant predictor of mean arterial blood pressure, HDL cholesterol, and waist circumference. The MetSyn exists in both HS- and College-level football players, with almost all cases occurring in the athletes with the highest levels of %Fat (offensive/defensive lineman). Strength and conditioning coaches should be aware of the prevalence of MetSyn risk factors in offensive and defensive linemen and take appropriate actions to ensure athlete safety.

Resistance exercise and aerobic exercise when paired with dietary energy restriction both reduce the clinical components of metabolic syndrome in previously physically inactive males.

The purpose of this study was to compare resistance exercise training (RT) to aerobic exercise training (AE) on the clinical risk factors for metabolic syndrome (MetSyn) in physically inactive overweight males (age 27-48 years). Subjects with at least one risk factor for MetSyn performed RT (n = 13, age 35.1 ± 4.7 years, BMI 31.2 ± 2.7 kg/m(2)) or AE (n = 9, age 37.6 ± 4.9 years, BMI, 31.2 ± 3.2 kg/m(2)) for 6 months. Training frequency and exercise session duration were equal and by 3 months the subjects exercised 4 day/week for 45 min/session. Blood lipids and glucose, waist circumference, and mean arterial blood pressure (MAP) were measured at 0, 3, and 6 months. A MetSyn z score was calculated for each subject from triglycerides, HDL cholesterol, fasting glucose, waist circumference, and MAP. Statistical significance was set at p ≤ 0.05. No significant differences existed between RT and AE groups at 0 month. AE showed a significant reduction in MetSyn z score from 0 (0.91 ± 3.57) to 6 months (-1.35 ± 2.95), while RT approached significance (p = 0.07) from 0 (0.09 ± 2.62) to 6 months (-1.30 ± 2.22). Triglycerides (mmol/L) significantly decreased in AE from 0 (1.93 ± 0.90) to 6 months (1.41 ± 0.70). Waist circumference (cm) significantly decreased in AE from 0 (106.8 ± 7.3) to 6 months (101.2 ± 6.5), and in RT from 0 (108.4 ± 9.0) to 6 months (105.7 ± 7.0). MAP (mmHg) decreased in RT from 0 (93.8 ± 5.8) to 6 months (87.5 ± 6.1) and in AE from 0 (97.6 ± 7.0) to 6 months (91.3 ± 6.8). With equal training frequency and exercise session duration, both RT and AE training, when paired with energy restriction improve the clinical risk factor profile for MetSyn.

Comparison of the PUSH Band 2.0 and Vicon Motion Capture to Measure Concentric Movement Velocity during the Barbell Back Squat and Bench Press.

The purpose of this investigation was to compare concentric movement velocity (CMV) measured with the PUSH Band (v2.0) and a Vicon motion capture system (MC) during the back squat (SQ) and the bench press (BP) resistance exercises (RE). Twelve resistance-trained males (26.0 ± 5.5 years; 175.6 ± 4.9 cm; 96.3 ± 15.8 kg) completed ten repetitions at 50% of one-repetition maximum (1RM), and six repetitions at 75% 1RM for both BP and SQ. Four PUSH devices were utilized and attached to the subject's right forearm, the center barbell, left and right sides of the barbell. MC markers were placed on top of each PUSH device. An overall analysis using a series of least-squares means contrasts suggested CMV did not differ (p > 0.05) between measurement technologies when position, RE, intensity and repetitions were combined. PUSH exhibited the highest Intraclass Correlation Coefficients (ICC = 0.835−0.961) and Pearson Product-Moment Correlation Coefficients (r = 0.742−0.949) at the arm and center barbell locations when compared with MC. The measurement of CMV between MC and PUSH compares favorably during moderate (i.e., 50%) and high (75%) intensity SQ and BP RE. These data indicate individuals can use the PUSH band v2.0 to accurately monitor CMV within a RE set for SQ and BP RE.

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.

An acute bout of aerobic exercise reduces movement time in a Fitts' task.

Movement time (MT) is one of the most important variables influencing the way we control our movements. A few previous studies have generally found that MT reduces with reaction time testing during exercise. However, limited evidence exists concerning change in MT following an acute bout of exercise. Our purpose was to investigate the effect of an acute bout of aerobic exercise on movement time as assessed by a Fitts' Law task. We also sought to determine if exercise would further lower MT during the more difficult task conditions compared with rest. Nineteen (12 male, 7 female) volunteers (19-28 yrs) completed a computerized paired serial pointing task to measure movement time before and after rest (R) and an acute bout of moderate aerobic exercise (E) using a within subjects crossover design. Comparisons between exercise and rest conditions were made to determine if there were differences in movement time. Exercise significantly reduced MT compared with rest. Movement time was reduced by an average of 208 ms following exercise compared with 108 ms following rest. Exercise did not further lower MT during the more difficult task conditions. These results suggest that an acute bout of aerobic exercise reduces movement time which is an important component of motor control. Further studies are needed to determine the duration of the effect as well as the optimum duration and intensity of exercise.

Physical activity intervention studies: what we know and what we need to know: a scientific statement from the American Heart Association Council on Nutrition, Physical Activity, and Metabolism (Subcommittee on Physical Activity); Council on Cardiovascular Disease in the Young; and the Interdisciplinary Working Group on Quality of Care and Outcomes Research.

In this review, our first purpose is to provide an overview of existing physical activity intervention research, focusing on subpopulations and intervention modalities. Our reviews within each area are not exhaustive or quantitative, as each area has been reviewed in more depth in numerous other reports. Instead, our goal is to provide a single document that provides a qualitative overview of intervention research that emphasizes selected topics of particular importance for improving the population-wide impact of interventions. Therefore, in synthesizing this vast literature, we begin with existing reviews of physical activity research in each area and incorporate in our discussions recent reports of well-designed individual physical activity intervention studies that expand the existing research base and/or target new areas of research. Our second purpose is to offer new ideas and recommendations to improve the state of the science within each area and, where possible, to propose ideas to help bridge the gaps between these existing categories of research.

Relationship between proxies for Type II fiber type and resting blood pressure in Division I American Football Athletes.

OBJECTIVE: The risk for cardiovascular disease is well-documented. Perhaps surprisingly, specific athletic populations, including American football players, exhibit increased risk for cardiovascular disease as presented by elevated blood pressure. There is evidence suggesting a link between muscle fiber type distribution and resting blood pressure. Acknowledging this association, it becomes important to clarify an individual's risk for developing cardiovascular disease later in adulthood. The purpose of this study was to assess football performance measures-in particular proxies for muscular power-and their effect on resting blood pressure in football athletes. METHODS: A total of 80 collegiate-level football players participated in this study. Each participant's body fat %, body mass index, waist circumference, and mean arterial pressure (MAP) were measured. Participants performed one-repetition maximums of bench press, back squat, 40-yard dash, and vertical leap, and a power index (PI) defined as the product of vertical leap and mass. Linear regressions were run between body composition variables and performance measures for all players and a subset of skill players only. RESULTS: The PI was found to be positively, significantly correlated with MAP in all players (r = 0.269; P = 0.035) and the skill players subset (r = 0.425; P = 0.004). CONCLUSION: The results of the present study indicate an association between muscle fiber type distribution, as indicated by muscular power capacity, and resting blood pressure.

Heart rate monitoring as a measure of physical activity in children.

PURPOSE: Using a larger sample and broader range of activities than most previous investigations of HR monitoring, this study examined the need for individual calibration of the HR-VO2 prediction equation, the effect of including low-intensity activities when establishing the HR-VO2 equation, comparisons of different methods for calculating HR-VO2 prediction equations for maximum energy expenditure (EE) variance, and the effect of these different methods when applied to free-living HR data. METHODS: Forty-three children ages 8 to 12 completed laboratory assessments of the relationship between HR and VO2. Different methods of estimating daily EE were applied to free-living HR data collected from 37 of these children. RESULTS: There was significant individual variation in the HR-VO2 prediction equations. HR monitoring predicted VO2 during low-intensity activities, below most established cut points. Individual differences persisted during both high- and low-intensity activities. Although a HR-VO2 prediction equation generated from the group accounted for 85% of the variance in EE, significant improvements in prediction were achieved with individualized HR-VO2 prediction equations that took into account low-intensity activity levels. CONCLUSION: Generic equations derived from group data may be suitable for some applications. However, for investigators requiring more precision, individual HR-VO2 equations significantly improve prediction.

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.

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.

Effects of carbohydrate ingestion during exercise on substrate oxidation in physically active women with different body compositions.

We examined the effects of consuming a 6% carbohydrate (CHO) beverage during exercise on substrate oxidation in active, young Caucasian women with higher body fat (HF) (>25%) and lower body fat (LF) (<25%). The HF group (n = 9) had 32.4% ± 5.6% fat and the LF group (n = 8) had 20.0% ± 3.0% fat. Subjects completed 2 sessions of 45 min of treadmill exercise at 55% of maximal oxygen consumption. Immediately prior to and at 15-min intervals during exercise, subjects consumed 25% of a total volume of a CHO beverage (1 g CHO·kg(-1)) or a placebo (PLC). During exercise and for 2 h after exercise, expired gases were analyzed to determine oxidation rates for CHO (CHO-OX) and fat (FAT-OX). During exercise, significant differences (p < 0.05) in CHO-OX (mg·kg fat-free mass(-1)·min(-1)) were found between groups for the CHO trial (LF, 35.4 ± 4.7 vs. HF, 29.8 ± 3.6) and the PLC trial (LF, 33.7 ± 6.4 vs. HF, 26.3 ± 4.3). CHO-OX was significantly higher during the first hour of recovery in both the LF group (CHO, 9.3 ± 2.1 vs. PLC, 5.3 ± 2.4) and the HF group (CHO, 8.7 ± 2.0 vs. PLC, 4.2 ± 1.0), but during the second hour of recovery, only the HF group had a higher CHO-OX (CHO, 5.3 ± 1.8 vs. PLC, 3.9 ± 1.1). FAT-OX was significantly lower during the first hour of recovery in both the LF group (CHO, 0.6 ± 0.4 vs. PLC, 1.0 ± 0.4) and the HF group (CHO, 0.4 ± 0.4 vs. PLC, 1.4 ± 0.4), as well as during the second hour of recovery in both the LF group (CHO, 0.8 ± 0.4 vs. PLC, 1.3 ± 0.5) and the HF group (CHO, 0.9 ± 0.6 vs. PLC, 1.6 ± 0). CHO ingestion promotes CHO-OX and suppresses FAT-OX during and following exercise in physically active women with low and high levels of body fat.

Adolescent physical activity participation and motivational determinants across gender, age, and race.

BACKGROUND: Physical activity (PA) declines as adolescents get older, and the motivational determinants of PA warrant further investigation. The purposes of this study were to investigate the amount of physical and sedentary activity that adolescents participated in across age, gender, and race, and to investigate adolescents' attraction to PA and their perceived barriers and benefits across age, gender, and race. METHODS: High school students (N = 1163) aged between 13 and 16 years completed questionnaires on minutes and intensity of physical and sedentary activity, interests in physical activity, and perceived benefits and barriers to participating in PA. RESULTS: A series of multivariate analyses of variance were conducted and followed up with discriminant function analysis. PA participation decreased in older females. In addition, fun of physical exertion was a primary attraction to PA for males more than females. Body image as an expected outcome of participating in PA contributed most to gender differences. CONCLUSION: There is a need to determine why PA drops-off as females get older. Findings underscore the importance of structuring activities differently to sustain interest in male and female adolescents, and highlights motives of having a healthy body image, and making PA fun to enhance participation.

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.

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.

Exercise evaluation of upper- versus lower-extremity blood pressure gradients in pediatric and young-adult participants.

The aim of this study was to provide a normal reference for arm-leg blood pressure gradients in normal pediatric and young-adult patients before and after exercise. We assessed 216 normal participants by physical or echocardiographic exam, maximally tested using the James Cycle Protocol, with arm and leg blood pressures taken pre- and postexercise. Arm-leg gradients significantly increased from -5 mmHg at rest to 4, 2, and 1 mmHg 1, 3, and 4 min postexercise (p < .05). There was a small, statistically significant increase in arm-leg blood pressure with exercise, which is probably clinically insignificant. These data serve as a normal reference.