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Biomedical subjects

E R Buskirk

Publications and source records attributed to E R Buskirk.

At least 19 recordsLinked to original sources
PubMed1992

Body composition and the expiratory reserve volume of pre-pubertal lean and obese boys and girls.

Previously, we examined the expiratory reserve volume (ERV) of the lungs as a function of percentage body fat in an adult population (age range 18-58 years). A negative correlation resulted when ERV (expressed as a percentage of vital capacity, (ERV/VC) x 100) was regressed on percentage fat for both sexes. In the present study, similar comparisons were made for 33 pre-pubertal boys and girls (aged 7-12.5 years). The regression equation for the boys ((ERV/VC) x 100 = 44.2 - 0.56%fat, r = -0.77, P = 0.002) was similar to that of the adult men ((ERV/VC) x 100 = 48.7 - 0.80 %fat, r = -78) and women ((ERV/VC) x 100 = 49.5 - 0.63 %fat, r = -0.70). However, the girls studied did not follow the same pattern. In this group of pre-pubertal girls, a significant increase in (ERV/VC) x 100 with increasing body fatness was seen ((ERV/VC) x 100 = 29.3 + 0.19 %fat, r = 0.48, P = 0.03). In all four groups, no correlation was seen with age or height. Whereas there was a significant correlation between weight and (ERV/VC) x 100 in the adults, no such relationship was evident in the younger subjects. In pre-pubertal obese girls limited upper body muscle development, perhaps as a result of limited physical activity, may explain the different relationship between ERV and body fatness.

Body Composition↗
PubMed1991

Fat-free mass in relation to stature: ratios of fat-free mass to height in children, adults, and elderly subjects.

A cross-sectional relationship of fat-free mass to height expressed as a ratio (FFM:ht) is presented for 1103 people aged 6-86 y. Data are presented for 13 specific age groups by gender. By providing information for normal, healthy individuals, these data may be of comparative value for nutritionists and clinicians concerned with body composition of patients with wasting diseases. The data were collected over 20 y in our laboratory by using the same densitometric procedure. A significant increase in FFM:ht occurs during the preadolescent and adolescent years. The adolescent spurt continues for a longer period for boys than for girls, resulting in a significant gender difference beginning at approximately age 16 y and continuing throughout adulthood. A decline in FFM:ht, not statistically significant, appears to occur in men greater than 60 y of age, and a significant decline occurs among women greater than 50 y of age (alpha less than 0.01). Thus, both gender- and age-related trends that have implications for the interpretation of comparative body-composition status are suggested.

Adolescent↗
PubMed1991

Energy turnover and heat exchange in mature lean and obese Zucker rats acutely exposed to three environmental temperatures for 24 hours.

Differences between lean (FA/?, n = 6) and obese (fa/fa, n = 6) mature male Zucker rats' energy turnover and heat storage were compared during a 24-h period when the animals were exposed to ambient temperatures of 30, 15 or 5 degrees C. Energy turnover was examined through measurements of heat production rates via indirect calorimetry and heat loss rates via direct calorimetry. Heat storage rates were calculated as the difference between heat production and heat loss rates. Predicted heat storage rates were also calculated as the product of the change in core temperature and the calculated specific heat of the animal based on body composition (carcass) analysis. A minimal heat loss rate was determined for each animal representing a period of least activity. Various comparisons were made: between groups (lean/obese), temperature (30, 15, 5 degrees C), calorimetry method (indirect/direct), period (light/dark), heat storage (experimental/predicted), and minimal heat loss. Immediately before a test, pretest weight and colonic temperature were obtained. Then, the animal was placed into the calorimeter chamber and remained there unrestrained for 24 h. Normal light/dark periods were maintained. On removal from the calorimeter, core temperature and body weight measurements were again obtained. Upon completion of all tests, body composition was analyzed and surface area determined. Energy turnover, i.e. both heat production and heat loss in the lean and obese animals differed among the 30, 15 and 5 degrees C exposures. The obese animals had relatively greater heat production rate and heat loss rate (kcal/day or kcal/kg (FFM)/day than the lean animals at 30, 15 and 5 degrees C. But, on a relative basis, the increments in heat production in the cold environments were greater for the lean animals. Both the lean and obese animals tended to be more active during the dark period when at 30 degrees C, but the difference was less at 15 degrees C and even less at 5 degrees C. Experimental heat storage rates did not differ significantly from predicted values at any of the temperatures with the possible exception of the animals at 5 degrees C. It was concluded that the mature obese Zucker rats had no major discernible defect in thermoregulation as revealed by rates of heat production and loss, although three of the obese rats did elicit a drop in colonic temperature during exposure to 5 degrees C, i.e. their excessive subcutaneous adiposity and thermal insulation did not prevent a fall in colonic temperature.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of Variance↗
PubMed1991

Ventilatory response of moderately obese women to submaximal exercise.

To investigate the effect of moderate obesity on ventilatory responses to graded exercise, we compared the ventilatory responses of ten moderately obese (35 +/- 5 percent body fat) and nine leaner women (22 +/- 2 percent body fat) during walking on a treadmill with incremental increases in percent grade. Speed remained constant at 3.0 mph. In the obese women, VO2 in l/min and ml/FFW/min, fb (b/min), VE (l/min), and HR were significantly greater (P less than 0.05) at all four absolute workloads. At 10.0 and 12.5 percent grade, VO2 (ml/kg/min) was smaller and VE/VO2 was greater in the obese women. The difference in VE/VO2 suggests a lower ventilatory threshold for the obese women. Percent VO2 max and R (VCO2/VO2) were significantly different at 12.5 percent grade only. When VO2 was divided by HR (oxygen pulse), the two groups were not significantly different at any of the four workloads tested. The groups were compared further at workloads representing approximately 55, 65, 75, and 85 percent of VO2 max. HR was not significantly different at any of the four relative exercise intensities. VE was significantly greater in the obese at 85 percent of maximum only (P less than 0.05) and fb was significantly greater at 55, 75, and 85 percent of maximum. Whereas cardiorespiratory responses of moderately obese women are increased at absolute workloads when compared to that of leaner women, HR is similar at comparable intensities of exercise. VE is also similar at comparable intensities of exercise below ventilatory threshold but fb is greater. The effect of the higher fb on exercise tolerance is unknown.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Exercise end-expiratory lung volumes in lean and moderately obese women.

End-expiratory lung volumes (EELV) and expiratory flow rates were determined in 10 moderately obese (mean, 35 percent fat) and 10 relatively lean women (22 percent fat) at rest and during exercise on a treadmill at 55 and 85 percent of VO2max. Expiratory reserve volume (ERV) as a percentage of forced vital capacity (FVC) was used as an index of EELV. Differences in body weight, body fatness, and VO2max were significant (P less than 0.05). The resting EELV in the obese women was less than (P less than 0.01) that in the leaner women (32 vs 37 percent). During exercise at the two intensities, the EELV remained near the resting value in the obese women (approximately 30 percent). In contrast, the leaner women experienced an initial decrease in EELV during exercise at 55 percent of VO2max (i.e., from 37 to 32 percent) (P less than 0.01); thereafter, the EELV changed no further during exercise at 85 percent of VO2max. There were no significant differences in relative expiratory flow rates at rest or during exercise between the obese and lean women. In conclusion, moderately obese women fail to decrease their EELV during exercise in contrast to leaner women who do. A non-linear respiratory system pressure-volume curve, plus increased resistance as maximal flow is approached may combine to determine a lower limit of EELV during exercise.

Body Composition↗
PubMed1987

Habitual daily energy expenditure and activity levels of lean and adult-onset and child-onset obese women.

The energy expenditure (EE) of eight lean, eight adult-onset obese (AOO), and eight child-onset obese (COO) women was determined over three 24-h periods by the factorial method, modified by subject-keypunched and mechanically recorded activity diaries. Mean daily EE was significantly higher in the pooled obese women (2472 +/- 488 kcal) than in lean women (1979 +/- 302 kcal) due to higher energy costs of sedentary and light activity in the obese. EE during moderate-to-strenuous activity was similar between groups because lean women performed these activities more vigorously. AOO and COO differed significantly in neither mean EE nor habitual activity. Fat-free mass (FFM) was a better predictor than body weight of both mean daily EE and the energy cost of activity. These data indicate that EE is positively related to obesity. Obese women tend to limit possible EE by reducing the vigorousness of weight-supported activity.

Activities of Daily Living↗
PubMed1987

Age and aerobic power: the rate of change in men and women.

The historic studies by Robinson and Astrand as well as more recent studies present a fairly uniform rate of decline in VO2max with age at 0.40-0.50 ml X kg-1 X min-1 X year-1 in men. In women the rate of decline appears to be less--approximately 0.20-0.35 ml X kg-1 X min-1 X year-1, at least in cross-sectional studies. Further, there is no clear distinction in the rate of change in VO2max when comparing active and inactive populations. Longitudinal studies varying from 2.5 to 21 to 56 years present a confounding picture. The rate of decline in VO2max varies from 0.04 to 1.43 ml X kg-1 X min-1 X year-1. There is some indication that active individuals decline at a slower rate than inactive persons but the results are not uniform. A possible explanation is that changes in VO2max over the entire age range may be curvilinear, with active individuals declining slowly as long as they maintain a regular exercise program, and sedentary individuals declining at a rapid rate during their 20's and 30's followed by a slower rate of decline of their VO2max as they age further.

Adult↗
PubMed1978

A method for assessing volunteer bias and its application to a cardiovascular disease prevention progamme involving physical activity.

Studies of chronic disease may require long-term observation of volunteer participants. This is a characteristic of investigations of primary or secondary prevention of cardiovascular disease by increased level of physical activity. Activation of sedentary, middle-aged, high risk men requires a substantial personal commitment on their part to a long-term programme. Because of self-selection, individuals who volunteer for such programmes cannot be assumed to be representative of the populations from which they come. To the best of our knowledge, there has been no systematic investigation of such self-selection based upon a study designed for that purpose. We found little consistent tendency for vouunteering behaviour to be associated with serum cholesterol, blood pressure, relative weight, level of activity at work, or Type A hehaviour variables.

Adult↗
PubMed1978

Respiratory flow integrator with improved stability.

A circuit was designed for integrating respiratory flow signals over time to produce volume signals. The circuit involves a simple integrator and three compensation subcircuits which control integrator drift caused by ambient temperature changes, flow signal base-line errors, and random signal errors. A functional unit built according to the circuit design requires initial adjustment, but no further adjustment before or during sustained use. Integration errors are typically less than 1%. The only flow signal requirements are that they be bidirectional and within the human physiological frequency range.

Humans↗
PubMed1977

Diet and athletic performance.

There are no dietary tricks or special diets that will give athletes a competitive advantage. Appetite and satiety are sensitive regulators of food intake to meet the caloric requirements of physical conditioning, training, and athletic competition.

Body Composition↗
PubMed1977

Effects of an endurance training regimen on assessment of work capacity in prepubertal children.

The cardiovascular effects of a 12-week endurance training regimen were studied among normally active and healthy prepubertal children. Twenty-six 8- to 12-year-old children (20 boys and 6 girls) volunteered and 10 acted as control subjects. The training regimen consisted of distance running for progressively longer periods (from 10 to 35 min) 2 to 3 times per week, with 2 additional sessions per week devoted to running games. Those who were trained ran a cumulative average distance of 95.6 km (58.9 miles). Intensity of work was assessed from running pace and heart rate. The target workout intensity was 75% to 80% of aerobic capacity (Vo2 max). Growth and development accounted for increases in height, weight, body circumferences, and diameters, and fat-free body weight. Heart rate (HR) during submaximal workloads, both running and walking, decreased in the trained group (p less than 0.01) and (p less than 0.05). HRmax did not change, but Vo2 max increased significantly (average 7%) in the trained group but not in the controls. No significant change attributable to training was found for submaximal cardiac output, stroke volume, or arteriovenous oxygen difference. The Vo2 max value before conditioning was a relatively poor predictor of the magnitude of improvement in functional capacity, but those with higher initial Vo2 max logged more cumulative training mileage. It was concluded that prepubertal children respond to an endurance training regimen by improving their running capacity, which is, to a limited extent, associated with increased aerobic capacity.

Child↗