Scaling peak VO2 to body mass in young male and female distance runners.

This study examined age- and sex-associated variation in peak oxygen consumption (VO2) of young male and female distance runners from an allometric scaling perspective. Subjects were from two separate studies of 9- to 19-yr-old distance runners from the mid-Michigan area, one conducted between 1982 and 1986 (Young Runners Study I, YRS I) and the other in 1999-2000 (Young Runners Study II, YRS II). Data from 27 boys and 27 girls from YRS I and 48 boys and 22 girls from the YRS II were included, and a total of 139 and 108 measurements of body size and peak VO2 in boys and girls, respectively, were available. Subjects were divided into whole year age groups. A 2 x 9 (sex x age group) ANOVA was used to examine differences in peak VO2. Intraindividual ontogenetic allometric scaling was determined in 20 boys and 17 girls measured annually for 3-5 yr. Allometric scaling factors were calculated using linear regression of log-transformed data. Results indicated that 1) absolute peak VO2 increases with age in boys and girls, 2) relative peak VO2 (ml x kg(-1) x min(-1)) remains relatively stable in boys and in girls, 3) relative peak VO2 (ml x kg(-0.75) x min(-1)) increases throughout the age range in boys and increases in girls until age 15 yr, and 4) peak VO2 adjusted for body mass (ml/min) increases with age in boys and girls. The overall mean cross-sectional scaling factor was 1.01 +/- 0.03 (SE) in boys and 0.85 +/- 0.05 (SE) in girls. Significant age x sex interactions and significant scaling factors between sexes identify the progressive divergence of peak VO2 between adolescent male and female distance runners. Mean ontogenetic allometric scaling factors were 0.81 [0.71-0.92, 95% confidence interval (CI)] and 0.61 (0.50-0.72, 95% CI) in boys and girls, respectively (P = 0.002). There was considerable variation in individual scaling factors (0.51-1.31 and 0.28-0.90 in boys and girls, respectively). The results suggest that the interpretation of growth-related changes in peak VO2 of young distance runners is dependent upon the manner of expressing peak VO2 relative to body size and/or the statistical technique employed.     

The influence of physical activity on lean mass accrual during adolescence: a longitudinal analysis.

During childhood, physical activity is likely the most important modifiable factor for the development of lean mass. However, the effects of normal growth and maturation must be controlled. To distinguish effects of physical activity from normal growth, longitudinal data are required. One hundred nine boys and one hundred thirteen girls, participating in the Saskatchewan Pediatric Bone Mineral Accrual Study, were repeatedly assessed for 6 yr. Age at entry was 8-15 yr. Stature, body mass, and physical activity were assessed biannually. Body composition was assessed annually by dual-energy X-ray absorptiometry. Physical activity was determined using the physical activity questionnaires for children and adolescence. Biological age was defined as years from age of peak height velocity. Data were analyzed using multilevel random-effects models. In boys, it was found that physical activity had a significant time-dependent effect on lean mass accrual of the total body (484.7+/-157.1 g), arms (69.6+/-27.2 g), legs (197.7+/-60.5 g), and trunk (249.1+/-91.4 g) (P<0.05). Although the physical activity effects were similar in the girls (total body: 306.9+/-96.6 g, arms: 31.4+/-15.5 g, legs: 162.9+/-40.0 g, and trunk: 119.6+/-58.2 g; P<0.05), boys for the same level of activity accrued, depending on the site, between 21 and 120% more absolute lean mass (g). In conclusion, habitual physical activity had a significant independent influence on the growth of lean body mass during adolescence, once biological maturity and stature were controlled.     

Comparison of running performances and prevalence of overweight and obesity in Hungarian and Ukrainian adolescents

The 20-m shuttle run (20-mSRT) is a widely used field test to estimate peak oxygen consumption (VO2peak) and thus to assess aerobic fitness of adolescents (11). The purpose of this study was to analyse differences in basic anthropometric measurements (stature, body mass, percent body fat, BMI) and in aerobic fitness of Hungarian and Ukrainian adolescent boys and girls. We examined gender differences in maximal speed (km h-1), in peak VO2 (mL kg-1 min-1) and maximal heart rate (HRmax min-1). Two hundred ninety-two Ukrainian (mean age=16.5±0.5) and 374 (mean age=16.5±0.5) Hungarian adolescents volunteered to participate in this study. Differences were analysed using factorial analysis of the variance (ANOVA) and Student's t-test. Statistical significance was set at p<0.05. Hungarian boys and girls were significantly taller, heavier and had higher percent body fat than their Ukrainian counterparts. Altogether 10% of Hungarians and 7% of Ukrainians were classified overweight or obese according to Cole's BMI classification (4). VO2peak of Ukrainians (mean=49.44±5.29 mL kg-1 min-1) were significantly higher than that of Hungarians (mean=41.93±8.40 mL kg-1 min-1). Maximal heart rate also differed significantly (Ukrainians mean=201.12±8.43 min-1 vs. Hungarians mean=185.38±18.38 min-1).In conclusion, aerobic fitness of the Ukrainian adolescents was significantly higher than that of the Hungarians independently of BMI or gender.     

The peak oxygen uptake of British children with reference to age, sex and sexual maturity

The purposes of this study were to provide baseline data on the peak oxygen consumption (VO2) of British children, aged 11-16 years and to examine the peak VO2 of children in relation to their pubertal stage of development. The peak VO2 of 226 boys and 194 girls was determined during either treadmill running or cycle ergometry. The sexual maturity of 320 of the children was estimated using Tanner's indices. Peak VO2 increased with chronological age in both sexes and from about the age of 12 years boys exhibited significantly higher (P less than 0.05) values than girls. Boys' peak VO2 in relation to body mass was consistent over the age range studied and was superior (P less than 0.05) to girls' values at all ages. It appears that mass-related peak VO2 is independent of sexual maturity in both sexes. The more mature boys demonstrated a significantly higher (P less than 0.05) peak VO2 (1.min-1) than the less mature boys on both ergometers. The more mature girls demonstrated significantly higher (P less than 0.05) peak VO2 (1.min-1) than the less mature girls only on the cycle ergometer. On both ergometers the differences between the peak VO2 of the girls and boys were more pronounced in the mature children whether expressed in relation to body mass or not. Comparison of the results with earlier data drawn from smaller samples failed to provide evidence to suggest that British children's peak VO2 has declined in recent years. No study with which to compare our maturity peak VO2 data appears to be available.     

Scaling Vo2 Peak in Obese and Non‐obese Girls

Objective: The conventional ratio method (milliliters O₂ per mass) typically is used to express Vo ₂ peak. The goal of the current study was to compare Vo ₂ peak of obese girls with normal‐weight girls by ratio and allometric scaling methods. Research Methods and Procedures: We compared Vo ₂ peak by ratio and allometric methods in 46 obese and 47 normal‐weight girls. Indirect calorimetry was used to measure Vo ₂ peak during either treadmill running or walking. Regression analysis was used to determine coefficients for mass and stature for each group with ANOVA used to compare data between groups. Results: The obese girls were taller and had higher values of body fatness (p ≤ 0.05). Absolute Vo ₂ peak (liters per minute) was similar between groups ; however Vo ₂ peak relative to mass was 50% lower (p ≤ 0.05) in the obese girls. When Vo ₂ peak (milliliters per minute per kilogram) and mass were correlated, r = ?0.48 was found in the obese group. Allometric scaling of logarithmic transformed stature and mass reduced this to r = ?0.002, thus eliminating the bias associated with the ratio method. Adjusting Vo ₂ peak allometrically scaled for mass, stature, and the combination of mass and stature reduced the difference between groups from 50% (ratio method) to 10% to 11% (p ≤ 0.05) with higher values found in the normal‐weight girls. Discussion: These results demonstrate the bias associated with the ratio method when comparing Vo ₂ peak in obese girls with Vo ₂ peak in normal‐weight girls. Allometric scaling eliminated the bias and thus may reflect a truer comparative response.     

Fat oxidation rate and the exercise intensity that elicits maximal fat oxidation decreases with pubertal status in young male subjects

The range of exercise intensities that elicit high fat oxidation rates (FOR) in youth and the influence of pubertal status on peak FOR are unknown. In a longitudinal design, we compared FOR over a range of exercise intensities in a small cohort of developing prepubertal male subjects. Five boys all at Tanner stage 1 (ages 11-12 yr) and nine men (ages 20-26 yr) underwent an incremental cycle ergometry test to volitional exhaustion. FOR curves were determined from indirect calorimetry during the final 30 s of each increment. The same protocol was duplicated annually in the boys as they progressed through puberty. The peak FOR was considerably higher (P<0.05) in boys at Tanner 1 (8.6+/-1.5 mg.kg lean body mass(-1).min(-1)) (mean+/-SD) compared with men (4.2+/-1.1 mg.kg lean body mass(-1).min(-1)). FOR dropped as boys developed through puberty (Tanner 2/3 peak rate=7.6+/-0.6 mg.kg lean body mass(-1).min(-1); Tanner 4 peak rate=5.4+/-1.8 mg.kg lean body mass(-1).min(-1), main effect of Tanner stage; P<0.05) to the levels found in men (not significant). The exercise intensity that elicited peak FOR was higher in the boys at Tanner 1 [56+/-6% peak aerobic power (VO2 peak)] than in men (31+/-4% VO2 peak) (P<0.001). This value tended to decrease by Tanner stage 4 (45+/-10% VO2 peak, main effect of Tanner stage; P=0.06). We conclude that, compared with men, prepubertal boys have higher relative FOR throughout a wide range of exercise intensities and that FOR drops as boys develop through puberty.     

Peripheral effects of endurance training in young and old subjects

The effects of 12 wk of endurance training at 70% peak O2 consumption (VO2) were studied in 10 elderly (65.1 +/- 2.9 yr) and 10 young (23.6 +/- 1.8 yr) healthy men and women. Training had no effect on weight or body composition in either group. The elderly had more adipose tissue and less muscle mass than the young. Initial peak VO2 was lower in the elderly, but the absolute increase of 5.5-6.0 ml.kg-1.min-1 after training was similar for both groups. Muscle biopsies taken at rest showed that, before training, muscle glycogen stores were 61% higher in the young. Before training, glycogen utilization per joule during submaximal exercise was higher in the elderly. Glycogen stores and muscle O2 consumption increased significantly in response to training in the elderly only. After training, the proportion of energy derived from whole body carbohydrate oxidation during submaximal exercise declined in the young only. The absolute changes that training produced in peak VO2 were similar in both age groups, but the 128% increase in muscle oxidative capacity was greater in the elderly, suggesting that peripheral factors play an important role in the response of the elderly to endurance exercise.     

Cardiorespiratory fitness predicts changes in adiposity in overweight Hispanic boys

We have previously shown that cardiorespiratory fitness predicts increasing fat mass during growth in white and African-American youth, but limited data are available examining this issue in Hispanic youth. Study participants were 160 (53% boys) overweight (BMI>or=85th percentile for age and gender) Hispanic children (mean+/-s.d. age at baseline=11.2+/-1.7 years). Cardiorespiratory fitness, assessed by VO2max, was measured through a maximal effort treadmill test at baseline. Body composition through dual-energy X-ray absorptiometry and Tanner stage through clinical exam were measured at baseline and annually thereafter for up to 4 years. Linear mixed models were used to examine the gender-specific relationship between VO2max and increases in adiposity (change in fat mass independent of change in lean tissue mass) over 4 years. The analysis was adjusted for changes in Tanner stage, age, and lean tissue mass. In boys, higher VO2max at baseline was inversely associated with the rate of increase in adiposity (beta=-0.001, P=0.03); this effect translates to a 15% higher VO2max at baseline resulting in a 1.38 kg lower fat mass gain over 4 years. However, VO2max was not significantly associated with changes in fat mass in girls (beta=0.0002, P=0.31). In overweight Hispanic boys, greater cardiorespiratory fitness at baseline was protective against increasing adiposity. In girls however initial cardiorespiratory fitness was not significantly associated with longitudinal changes in adiposity. These results suggest that cardiorespiratory fitness may be an important determinant of changes in adiposity in overweight Hispanic boys but not in girls.     

Longitudinal study of ventilation threshold and maximal O2 uptake in athletic boys

Ventilation threshold (VET) and peak O2 uptake (VO2max) were determined annually from ages 11 to 15 yr in 18 athletic boys. The treadmill protocol consisted of a constant-run speed with grade increments every second minute. Ventilation, VO2, and CO2 production were measured using online open-circuit spirometry. Coefficients of variation for determination of VO2max and VET were 3.4 and 5.6%, respectively. VO2max increased across age 11-15 yr, from 60.8 to 68.0 ml X kg-1 X min-1. VET at 11 yr was 34.4 and at 15 yr 41.9 ml X kg-1 X min-1, thus increasing from 56 to 62% of VO2max. Previous studies of children have shown a decline of VET relative to VO2max across age; however, in the present study the increase may have been due to the training of the boys in competitive athletics. However, the trained youth did not achieve the high relative threshold of trained adults. Across age, both VO2max and VET scaled to weight to the power 1 (in a log-log transformation). The increase in VO2max (l/min) showed greatest increments corresponding to gains in size (a growth curve), whereas increases of VET were consistent year to year. Thus VET was altered independently of VO2max. Factors other than size (and presumably muscle mass) such as the maturation of an enzymatic profile of fast glycolytic fibers might have an important influence on the threshold during youth.     

Gender differences in the endocrine and metabolic responses to hypoxic exercise.

This study tested the hypothesis that women would have blunted physiological responses to acute hypoxic exercise compared with men. Fourteen women taking oral contraceptives (28 +/- 0.9 yr of age) and 15 men (30 +/- 1.0 yr of age) with similar peak O(2) consumption (VO(2 peak)) values (56 +/- 1.1 vs. 57 +/- 0.8 ml x kg fat-free mass(-1) x min(-1)) were studied under hypoxic (H; fraction of inspired oxygen = 13%) vs. normoxic (fraction of inspired oxygen = 20.93%) conditions. Cardiopulmonary, metabolic, and neuroendocrine measures were taken before, during, and 30 min after three 5-min consecutive workloads at 30, 45, and 60% VO(2 peak). In women compared with men, glucose levels were greater during recovery from H (P < 0.05) and lactate levels were lower at 45% VO(2 peak), 60% VO(2 peak), and up to 20 min of recovery (P < 0.05), regardless of trial (P < 0.0001). Although the women had greater baseline levels of cortisol and growth hormone (P < 0.0001), gender did not affect these hormones during H or exercise. Catecholamine responses to H were also similar between genders. Thus the endocrine response to hypoxia per se was not blunted in women as we had hypothesized. Other mechanisms must be at play to cause the gender differences in metabolic substrates in response to hypoxia.     

Fatty acid oxidation in African-American and Caucasian women during physical activity.

The goal of this study was to determine whether differences in physical activity-related fat oxidation exist between lean and obese African-American (LAA and OAA) and lean and obese Caucasian (LC and OC) premenopausal women. Lean AA (28.4 +/- 2.8 yr, n = 7), LC (24.7 +/- 1.8 yr, n = 9), OAA (30.9 +/- 2.2 yr, n = 11), and OC (34.1 +/- 2.5 yr, n = 9) women underwent preliminary assessment of peak aerobic capacity (VO2 peak). On a subsequent testing day, participants exercised after an 8-h fast on a cycle ergometer at 15 W (approximately 40% VO2 peak) for 10 min and then for 10 min at approximately 65% VO2 peak). Fatty acid oxidation was determined using the average respiratory exchange ratio and O2 consumption during minutes 5-9 of the exercise session. Percent body fat and fat-free mass were lower (P < 0.05) in LAA (25.8 +/- 2.8% and 48.3 kg) and LC (26.4 +/- 2.0% and 45.8 +/- 1.7 kg) than in OAA (41.2 +/- 1.3% and 58.8 +/- 3.3 kg) and OC (39.3 +/- 2.7% and 58.6 kg) women. Fat oxidation among the groups was analyzed statistically using analysis of covariance with fat-free mass and VO2 peak) as covariates. During exercise at 15 W, fat oxidation was as low in LAA (0.134 +/- 0.024 g/min) as in OAA (0.144 +/- 0.026 g/min) and OC (0.156 +/- 0.020 g/min) women: all these rates of fat oxidation were lower than in LC women (0.200 +/- 0.021 g/min, P < 0.05, LC vs. all other groups). Fatty acid oxidation during higher-intensity exercise (65% VO2 peak)) was higher in LC than in OC women but was not statistically different between African-American and Caucasian groups. Fatty acid oxidation was therefore lower during low-intensity physical activity in OAA, LAA, and OC than in LC women.     

Effects of oral contraceptives on peak exercise capacity.

We examined the effects of menstrual cycle phase and oral contraceptive (OC) use on peak oxygen consumption (VO(2 peak)). Six moderately active, eumenorrheic women (25.5 +/- 1.5 yr) were studied before and after 4 mo of OC. Subjects were tested during the follicular and luteal phases before OC and the inactive and high-dose phases after OC. Before OC, there were no significant differences between the follicular and luteal phases in any of the variables studied. There were also no differences between the inactive and high-dose phases. Dietary composition, exercise patterns, and peak heart rate, minute ventilation, and respiratory exchange ratio did not change with OC use. However, OC use significantly (P 相似文献   

Reference norms for a fat-free mass index and fat mass index in the Japanese child population

The aims of this study were to determine reference norms for a fat-free mass index (FFMI) and fat mass index (FMI) in a large population of healthy children in Japan, to observe differences in these values in three age groups between ages three and eleven, and to develop percentile distributions for these parameters. Five hundred twenty-two boys and six hundred forty-nine girls with a wide spectrum of stature, body mass, and body composition underwent bioelectrical impedance analysis (BIA) for the determination of fat-free mass (FFM) and fat mass (FM). Both FFM and FM were divided by stature(2) to give FFMI and FMI, as described previously. Normal FFMI and FMI were defined within the range of the 25th to 75th percentile of age- and gender-specific data in this study. The reference norms for FFMI (3-11 yrs) were 12.7-13.4 kg/m(2) in boys and 12.0-13.0 kg/m(2) in girls. A modest increase in boys was observed with an age increase; otherwise, there were no marked age differences in FFMI for the children as a whole. The reference norms for FMI were 2.8-3.6 kg/m(2) in boys and 3.2-3.8 kg/m(2) in girls. For each 3-year category (i.e., ages 3-5, 6-8 and 9-11 yrs.), FMI progressively increased by an average of 28.6% in boys and 18.8% in girls, compared to an increase in BMI of 11.0 and 11.3% respectively. FFMI and FMI are appropriate for many purposes, and have the advantage of expressing both aspects of body composition in common units. In conclusion, the data presented as percentiles can serve as reference in comparing a child's body composition to that of healthy children of the same age and gender. The reference standards should be appropriate for almost all children in the Japan for whom stature, body mass, and body composition can be measured satisfactorily. However, a more sophisticated approach is ultimately required for evaluating body composition. This article is a preliminary attempt to promote future research in the area of childhood body composition.     

Aerobic work capacity of mentally retarded boys and girls in junior high schools.

The maximal oxygen uptake (Vo2 max) and ergometer load at a heart rate of 170 beats/min (PWC170) were determined in mentally retarded children (74 boys and 53 girls) of ages 12-15, whose IQ ranged from 36 to 91, and the results were compared with those for normal children. Mentally retarded boys and girls showed significantly inferior body height and weight, but no significant difference was found in skinfold thickness. The mean value of PWC170 for boys and girls was 14.34 kpm/kg/min and 11.31 kpm/kg/min, respectively, significantly less than that of the normal group. The mentally retarded boys had mean VO2 max per unit body weight of 42.4 ml/kg/min, which was significantly less than the 51.2 ml/kg/min of normal boys. The mentally retarded girls had a mean of 33.1 ml/kg/min which was also less than the 41.3 ml/kg/min of normal girls. The correlation coefficient between body weight and PWC170 (kpm/min) was 0.711 and 0.720 for boys and girls, respectively, while that between body weight and VO2 max (liter/min) was 0.641 for boys and 0.656 for girls. No significant correlation was found between IQ and PWC170 (kpm/kg/min) nor between IQ and VO2 max (ml/kg/min) both for boys and for girls. Similarly, no significant correlation was found between mental age and the VO2 max value (ml/kg/min).     

Role of muscle loss in the age-associated reduction in VO2 max

A progressive decline in maximal O2 consumption (VO2max) expressed traditionally as per kilogram body weight generally occurs with advancing age. To investigate the extent to which this decline could be attributable to the age-associated loss of metabolically active tissue, i.e., muscle, we measured 24-h urinary creatinine excretion, an index of muscle mass, in 184 healthy nonobese volunteers, ages 22-87 yr, from the Baltimore Longitudinal Study of Aging who had achieved a true VO2max during graded treadmill exercise. A positive correlation was found between VO2max and creatinine excretion in both men (r = 0.64, P less than 0.001) and women (r = 0.47, P less than 0.001). As anticipated, VO2max showed a strong negative linear relationship with age in both men and women. Creatinine excretion also declined with age in men and women. When VO2max was normalized for creatinine excretion, the variance in the VO2max decline attributable to age declined from 60 to 14% in men and from 50 to 8% in women. Thus comparing the standard age regression of VO2max per kilogram body weight with that in which VO2max is normalized per milligram creatinine excretion, the decline in VO2max between a hypothetical 30 yr old and a 70 yr old was reduced from 39 to 18% in men and from 30 to 14% in women. We conclude that in both sexes, a large portion of the age-associated decline in VO2max in non-endurance-trained individuals is explicable by the loss of muscle mass, which is observed with advancing age.     

Formula feeding in infancy is associated with adolescent body fat and earlier menarche.

The tempo, level of growth and maturation during adolescence may have important implications to future adult health. The purpose of the study was to examine factors associated with menarche. Three hundred and forty girls, 9 to 14 years old, were selected from all age eligible girls at Kaiser Permanente Oahu (Honolulu). Girls' age, ethnicity, menstrual status and feeding pattern during infancy were obtained by questionnaire. The mean age of girls was 11.5 +/- 1.4 yr and the mean age at menarche among 112 (33%) girls who had reached menarche was 11.6 +/- 1.1 yr. In logistic regression, achievement of menarche was positively explained by age, Asian ethnicity and formula feeding during infancy. In simple linear regression, higher body mass index (BMI) and subcutaneous fat were also positively associated with formula feeding during infancy. The study suggests that girls who were formula fed deposit more body fat than girls who were breast-fed, resulting in early attainment of menarche.     

Peak oxygen uptake during arm cranking for men and women

To determine upper body peak O2 uptake (VO2) in a group of young females and to obtain information on possible sex differences, 40 subjects, 20 females and 20 males, mean age 26 +/- 4 (SD) and 31 +/- 6 yr, respectively, were studied during maximal arm-cranking exercise. Peak values for power output, VO2, minute ventilation (VE), and heart rate (HR) were determined for each subject. In addition, arm-shoulder volume (A-SV) was measured before exercise. Significant differences between males and females (P less than 0.05) were found for peak power output (134 +/- 18 vs. 86 +/- 13 W), peak VO2 expressed in liters per minute (2.55 +/- 0.45 vs. 1.81 +/- 0.36) and milliliters per kilogram per minute (34.2 +/- 5.3 vs. 29.2 +/- 4.9), peak VE (95.4 +/- 14.5 vs. 70.1 +/- 19.2 1 X min-1), and A-SV (3,126 +/- 550 vs. 2,234 +/- 349 ml), whereas peak HR was not significantly different between the two groups (174 +/- 14 vs. 174 +/- 36 beats X min-1). However, when peak VO2 was corrected for arm and shoulder size there was no significant difference between the groups (0.82 +/- 0.13 vs. 0.78 +/- 0.13 ml X ml A-SV-1 X min-1). These results suggest that the observed differences between men and women for peak VO2 elicited during arm cranking when expressed in traditional terms (1 X min-1 and ml X kg-1 X min-1) are a function of the size of the contracting muscle mass and are not due to sex-related differences in either O2 delivery or the O2 utilization capacity of the muscle itself.     

Endurance training increases fatty acid turnover, but not fat oxidation, in young men.

We examined the effects of exercise intensity and a 10-wk cycle ergometer training program [5 days/wk, 1 h, 75% peak oxygen consumption (VO2 peak)] on plasma free fatty acid (FFA) flux, total fat oxidation, and whole body lipolysis in healthy male subjects (n = 10; age = 25.6 +/- 1.0 yr). Two pretraining trials (45 and 65% of VO2 peak) and two posttraining trials (same absolute workload, 65% of old VO2 peak; and same relative workload, 65% of new VO2 peak) were performed by using an infusion of [1-13C]palmitate and [1,1,2,3, 3-2H]glycerol. An additional nine subjects (age 25.4 +/- 0.8 yr) were treated similarly but were infused with [1,1,2,3,3-2H]glycerol and not [1-13C]palmitate. Subjects were studied postabsorptive for 90 min of rest and 1 h of cycling exercise. After training, subjects increased VO2 peak by 9.4 +/- 1.4%. Pretraining, plasma FFA kinetics were inversely related to exercise intensity with rates of appearance (Ra) and disappearance (Rd) being significantly higher at 45 than at 65% VO2 peak (Ra: 8.14 +/- 1.28 vs. 6.64 +/- 0.46, Rd: 8. 03 +/- 1.28 vs. 6.42 +/- 0.41 mol. kg-1. min-1) (P 相似文献   

Pubertal alterations in growth and body composition. V. Energy expenditure, adiposity, and fat distribution

We determined whether activity energy expenditure (AEE, from doubly labeled water and indirect calorimetry) or physical activity [7-day physical activity recall (PAR)] was more related to adiposity and the validity of PAR estimated total energy expenditure (TEE(PAR)) in prepubertal and pubertal boys (n = 14 and 15) and girls (n = 13 and 18). AEE, but not physical activity hours, was inversely related to fat mass (FM) after accounting for the fat-free mass, maturation, and age (partial r = -0.35, P < or = 0.01). From forward stepwise regression, pubertal maturation, AEE, and gender predicted FM (r(2) = 0.36). Abdominal visceral fat and subcutaneous fat were not related to AEE or activity hours after partial correlation with FM, maturation, and age. When assuming one metabolic equivalent (MET) equals 1 kcal. kg body wt(-1). h(-1), TEE(PAR) underestimated TEE from doubly labeled water (TEE bias) by 555 kcal/day +/- 2 SD limits of agreement of 913 kcal/day. The measured basal metabolic rate (BMR) was >1 kcal. kg body wt(-1). h(-1) and remained so until 16 yr of age. TEE bias was reduced when setting 1 MET equal to the measured (bias = 60 +/- 51 kcal/day) or predicted (bias = 53 +/- 50 kcal/day) BMR but was not consistent for an individual child (+/- 2 SD limits of agreement of 784 and 764 kcal/day, respectively) or across all maturation groups. After BMR was corrected, TEE bias remained greatest in the prepubertal girls. In conclusion, in children and adolescents, FM is more strongly related to AEE than activity time, and AEE, pubertal maturation, and gender explain 36% of the variance in FM. PAR should not be used to determine TEE of individual children and adolescents in a research setting but may have utility in large population-based pediatric studies, if an appropriate MET value is used to convert physical activity data to TEE data.