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Biomedical subjects

Oded Bar-Or

Publications and source records attributed to Oded Bar-Or.

28 records · Page 2Linked to original sources
PubMed2003

Energy cost of walking in boys who differ in adiposity but are matched for body mass.

PURPOSE: To compare the energy cost of treadmill walking, in pairs of obese and lean adolescents who were matched for total body mass. METHODS: Metabolic energy expenditure was determined at 67, 83, and 100 m.min-1, in nine obese and nine nonobese 11- to 18-yr-old boys. Total adiposity and fat distribution in the trunk and limbs were assessed using DXA. RESULTS: There were no intergroup differences in the net (exercise minus rest) energy cost at the two lower speeds, but the obese boys expended more energy at 100 m.min-1 (12%, P < 0.05). Heart rate was consistently higher in the obese boys: 18% at 67 m.min-1, 22% at 83 m.min-1, and 28% at 100 m.min-1. Pooling all subjects together, body mass, rather than adiposity, was the main predictor of energy cost: 89.1%, 76.3%, and 62.1% (P < 0.05 for all) of the total variance at 67, 83, and 100 m.min-1, respectively. The variance explained by total body fat was only 2.1%, 8.4%, and 16%, respectively. There was no relationship between [OV0312]O(2net) and the proportion of fat in body segments. CONCLUSION: It is total body mass, more than adiposity (total and regional) per se, that affects the energy cost of locomotion in obese boys.

Adipose Tissue↗
PubMed2003

Repeated treadmill walks affect physiologic responses in children with cerebral palsy.

PURPOSE: To determine whether physiologic responses during treadmill walking in children with cerebral palsy (CP) are affected by repeated walking bouts on different days, and whether effects are different at different speeds. METHODS: Three girls and five boys (9.2-15.7 yr, 23.3-64.4 kg) with mild CP received 12-15 min of treadmill walking practice and had their fastest walking speed (FWS) determined during an introductory visit. During each of three subsequent visits (day 1, day 2, day 3), subjects walked for 3 min at 60, 75, and 90% FWS. Resting physiologic measures were taken on day 1. RESULTS: From day 1 to day 3, net ventilation ([OV0312]E), and net heart rate (HR) at 90% FWS decreased by 3.6 L.min-1 and 8 beats.min-1, respectively. There were no differences between day 1 and day 2 or day 1 and day 3 for any other physiologic variable at any speed. Day 3 was less than day 2 for net HR (60% FWS) and, independent of speed, net [OV0312]O2 (per kilogram of body mass and per stride) and net energy expenditure (kJ.min-1). Between-day reliability (R) of physiologic responses was > or = 0.95, except respiratory rate (R = 0.75). Intrasubject, between-day variability for the [OV0312]O2 measures was 7.6-12.9%. CONCLUSION: Because there were no day 1 to day 3 reductions in metabolic variables, day 1 to day 3 reductions at 90% FWS in net HR may reflect decreased emotional stress over time and reductions in net [OV0312]E, an uncoupling of [OV0312]O2 and [OV0312]E. Despite between-day differences, reliable net physiologic and stable net metabolic variables may be collected in subjects with mild CP after one treadmill walking practice session.

Adolescent↗
PubMed2003

RPE during prolonged cycling with and without carbohydrate ingestion in boys and men.

PURPOSE: To examine the effect of prolonged cycling on ratings of perceived exertion (RPE) in boys and men and whether carbohydrate (CHO) ingestion would lower RPE during exercise. METHODS: Ten boys (9-10 yr) and 10 men (20-25 yr) cycled for 60 min at approximately 70% VO2peak on two occasions. In a double-blind, counterbalanced design, a total volume of 24 mL.kg(-1) body mass of either a 6% CHO-electrolyte (CT) or flavored water (WT) beverage was consumed intermittently before and during exercise in each trial. Oxygen consumption (VO2), ventilation (VE), respiratory rate (RR), RPE (Borg's 6-20 scale), and heart rate (HR) were recorded periodically throughout exercise. Plasma glucose (GLU) was determined before and after exercise. RESULTS: Postexercise GLU was not different between age groups but higher (P<0.001) during CT (5.6 +/- 0.2 mmol.L(-1)) compared with WT (4.7 +/- 0.1 mmol.L(-1)). CHO ingestion had no effect (P>0.05) on VO2, VE, RR, or RPE in either group. RR during exercise was higher (P<0.01) in boys (39.0 +/- 2.2 breaths.min(-1)) than in men (30.9 +/- 1.3 breaths.min(-1)). HR was slightly higher (P=0.047) during CT (160 +/- 3 beats.min(-1)) compared with WT (156 +/- 4 beats.min(-1)) and increased less over time (P<0.01) in boys compared with men. RPE at 5 min of exercise was similar (P>0.05) between boys (11.8 +/- 0.7) and men (12.0 +/- 0.7) but increased faster (P<0.01) over time in boys. The average exercise RPE was higher (P<0.01) in boys (15.8 +/- 0.5) than in men (14.0 +/- 0.4). CONCLUSIONS: The higher and faster increase in RPE during exercise in boys, compared with men, may reflect a sensitivity to RR that outweighed any effect of CHO ingestion on RPE.

Adult↗
PubMed2003

Physical activity, energy expenditure and intake in 11 to 12 years old Japanese prepubertal obese boys.

The purpose of this study is to find out the differences in physical activity (PA), energy expenditure (EE) and energy intake (EI) under free-living conditions between Japanese prepubertal obese and nonobese boys. The subjects were 15 prepubertal obese boys (Age: 11.7+/-0.4 years old, Body fat: 35.2+/-1.6%) who do not have obese parents and siblings and 15 prepubertal nonobese boys (Age: 11.8+/-0.4 years old, Body fat: 18.5+/-0.8%). We assessed their daily PA by heart rate (HR) monitoring, pedometer step counts (PSC) and time for sedentary activities (SA). We also examined calculated EE from HR-VO(2) regression, EI and percentage of macronutrient EI. Results are as follows: Percentage of body fat had significant correlation with weight, BMI, time for SA, percentage EI of protein (positive, p<0.001), VO(2max), VO(2max) per body weight, VO(2max) per LBM, PSC, TEE per body weight, TEI per body weight (negative, p<0.001), percentage of EI of carbohydrate (negative, p<0.01). The values of the obese were significantly lower in total EE per body weight and in total EI per body weight. EI from dinner was significantly higher in the obese group. The values of the obese were significantly higher in percentage EI from protein and that from carbohydrate. The results of this study showed prepubertal obese boys who do not have obese parents and siblings have low PA and spend much time for sedentary activities. Obese boys consume higher percentage energy of protein and lower percentage of carbohydrate though differences in EE and EI were found only in total EE per body weight and total EI per body weight between obese boys and nonobese boys.

Asian People↗
PubMed2002

Oxidation rate of exogenous carbohydrate during exercise is higher in boys than in men.

To determine whether the relative utilization of exogenous carbohydrate (CHO(exo)) differs between children and adults, substrate utilization during 60 min of cycling at 70% peak O(2) uptake was studied in 12 pre- and early pubertal boys (9.8 +/- 0.1 yr) and 10 men (22.1 +/- 0.5 yr) on two occasions. Subjects consumed either a placebo or a (13)C-enriched 6% CHO(exo) beverage (total volume per trial: 24 ml/kg). Substrate utilization was calculated for the final 30 min of exercise. During both trials, total fat oxidation was higher (5.4 +/- 0.5 vs. 3.0 +/- 0.4 mg x kg(-1) x min(-1), P < 0.001) and total CHO oxidation lower (27.4 +/- 1.5 vs. 34.8 +/- 1.2 mg x kg(-1) x min(-1), P < 0.001) in boys than in men, respectively. During the CHO(exo) trial, CHO(exo) oxidation was higher (P < 0.001) in boys (8.8 +/- 0.5 mg x kg(-1) x min(-1)) than in men (6.2 +/- 0.5 mg x kg(-1) x min(-1)) and provided a greater (P < 0.001) relative proportion of total energy in boys (21.8 +/- 1.4%) than in men (14.6 +/- 0.9%). These results suggest that, although endogenous CHO utilization during exercise is lower, the relative oxidation of ingested CHO is considerably higher in boys than in men. The greater reliance on CHO(exo) in boys may be important in preserving endogenous fuels and may be related to pubertal status.

Adipose Tissue↗
PubMed2002

Temperature-related overestimation of energy expenditure, based on heart-rate monitoring in obese boys.

An equation has been developed to reduce the error in predicting energy expenditure (EE) from heart rate (HR) monitoring, by correcting for climate-related HR increases. To evaluate the effects of such a correction in a "real life" situation, a group of 9- to 14-year-old obese boys [mean (SD) 36.6 (3.3)% body fat; n=14] was monitored for 6 days during the summertime. An activity interview was taken daily. During times of outdoor activities, measurements of HR were corrected for the influence of ambient temperature ( T) using the aforementioned equation. Time spent outdoors was 196.7 (21.1) min/day at a T of 17-34 degrees C. Temperature correction reduced the time spent at HR>140 beats/min and >160 beats/min by 20-25% during outdoor activity. Estimated outdoor EE corrected for the influence of temperature was 2.46 (2.37) MJ; the uncorrected value was 2.68 (2.45) MJ. The respective values for the waking hours and over 24 h were 7.34 (2.77) MJ versus 7.55 (2.81) MJ and 10.83 (2.72) MJ versus 11.05 (2.77) MJ, respectively. The excessive HR measured in a warm summer climate could explain 8.8 (3.5)% of EE during outdoor activities, which resulted in a 2.9 (2.7)% overestimate of EE during daily waking hours and a 1.9 (1.8)% overestimate of the total 24-h EE. Thus, the influence of temperature on HR may, at least in part, explain the previously reported overestimate of EE calculated using the HR/oxygen consumption relationship versus that calculated using the doubly labelled water method. We recommend correcting HR for the influence of climate in studies using HR profiles to determine outdoor physical activity levels and/or EE during summertime. However, when total daily EE or waking hours EE is assessed, even in subjects who are engaging in long intervals of outdoor play, the temperature correction required is minimal.

Adolescent↗
PubMed2002

Prediction of reflex sympathetic dystrophy in hemiplegia by evaluation of hand edema.

OBJECTIVE: To determine the predictive value of measurements of hand edema for the development of reflex sympathetic dystrophy (RSD). DESIGN: Cohort study. SETTING: Departments of rehabilitation medicine in 3 general hospitals and 1 rehabilitation hospital in Japan. PARTICIPANTS: Thirty-four stroke patients. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Measurement of the circumference of the middle finger was used to evaluate hand edema. The degree of hand edema was expressed by the ratio of circumference of the middle finger (RCMF) in the affected side to that in the uninvolved extremity. RESULTS: Eight of 34 patients developed clinical RSD from 2 to 4 months after stroke. Hand edema showed a significant relationship to the development of RSD (ie, the patients who had an RCMF of above 1.06 at 4 weeks poststroke had significantly higher incidence of RSD than those with a lower RCMF; P=.0127). CONCLUSION: It is possible to predict the development of RSD in hemiplegia by measuring hand edema 4 weeks poststroke.

Adult↗
PubMed2002

Explaining differences in the metabolic cost and efficiency of treadmill locomotion in children.

The metabolic cost of locomotion at any given speed, when expressed per kilogram of body mass, is greater for children than for older individuals. Incomplete explanations for the age-related difference motivated this study, which used a multidisciplinary method to examine metabolic, kinematic and electromyographic data from three maturational groups of children. Thirty children aged 7-8 (n = 10), 10-12 (n = 10) and 15-16 (n = 10) years completed 4 min bouts of submaximal treadmill exercise at six speeds--two walking and four running--assigned in random order. Metabolic (net VO2), kinematic (total body mechanical power, energy transfer rates, stride rate) and electromyographic (co-contraction of agonist and antagonist muscles in thigh and leg segments) data were collected. Multiple regression analysis was performed with net VO2 or efficiency as the dependent variable and mechanical power, thigh and leg co-contraction, stride rate and age as independent variables. It was possible to explain up to 77% of the age-related variance in net VO2 and 62% of the variation in efficiency using combinations of these variables. Age was the best single predictor of both VO2 and efficiency. Co-contraction, possibly used to enhance joint stability, was an important component of the observed age-related differences, although mechanical power was not. Additional variance might be explained as specific growth-related factors affecting the metabolic cost of locomotion are identified, as mechanical work models improve, and as methods are developed to measure the effects of stored elastic energy and the metabolic cost of isometric muscle actions.

Adolescent↗
PubMedDate not supplied

Self-efficacy and perceived exertion of girls during exercise.

BACKGROUND: An important national goal in Healthy People 2010 is to reduce the high prevalence of sedentary lifestyles and resultant overweight and obesity among girls. OBJECTIVES: The purpose of the present study was threefold: (a) to determine if pre-exercise self-efficacy predicted girls' perceptions of exertion during exercise, (b) to determine if these perceptions, in turn, influenced postexercise self-efficacy, and (c) to assess if exercise self-efficacy increased following completion of an exercise task. METHODS: A sample of 103 girls, 8 to 17 years of age, pedaled 20 minutes on a cycle ergometer at 60% of their predetermined peak VO2 in a climatic chamber (90 degrees F, 50% relative humidity). Ratings of perceived exertion were obtained every 4 minutes. Exercise self-efficacy was assessed before and after the exercise session. RESULTS: Controlling for peak VO2 and percent body fat, pre-exercise efficacy exerted an independent effect on perception of exertion during exercise with girls high on pre-exercise self-efficacy reporting lower perceived exertion during exercise, than girls low on self-efficacy. Both pre-exercise efficacy and perceived exertion explained postexercise efficacy. Exercise self-efficacy increased significantly from pre- to postexercise. CONCLUSIONS: Pre-exercise efficacy is an important factor influencing girls' perceptions of exertion during exercise and their postexercise efficacy. Increased exercise self-efficacy of girls following successful completion of an exercise challenge suggests possible strategies to increase physical activity.

Adolescent↗