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Biomedical subjects

E R Buskirk

Publications and source records attributed to E R Buskirk.

At least 37 records · Page 2Linked to original sources
PubMed1984

Body composition and expiratory reserve volume in female gymnasts and runners.

Previous research in this laboratory demonstrated a reduction in expiratory reserve volume of the lungs (ERV) with increasing body fatness (%F, by densitometry). The present study was done to determine if smaller ERV values could be demonstrated in lean female athletes with greater than normal upper-body muscle development. Expiratory reserve volume, vital capacity (VC), and segmental body volumes by densitometry were measured in members of two collegiate women's teams--gymnastics (G) (N = 10) and track (R) (N = 10). The runners provided a control group by being similar to gymnasts in age, weight, and body fatness, but they did not engage in upper-body weight training or gymnastic exercises. The two groups were not significantly different in body weight (means G +/- SD = 53.0 +/- 6.1 kg; means R = 50.8 +/- 4.6 kg) or %F (means G = 16.8 +/- 3.2%; means R = 14.8 +/- 3.8%), but R subjects were taller (means = 165.4 +/- 5.5 cm vs 158.7 +/- 4.8 cm, P less than 0.01). Expiratory reserve volume, expressed as a percent of VC, (ERV X VC-1) 100, was significantly (P less than 0.001) less in the gymnasts (means +/- SD = 29.7 +/- 7.1) as compared to the runners (43.1 +/- 6.4). All other lung capacities as volumes were comparable in both groups. Arm and thorax volumes indicated greater upper-body size in the G subjects (arm volume, means +/- SD of G = 4.8 +/- 0.6 liters, of R = 4.0 +/- 0.6 liters, P less than 0.01; thorax volume, means +/- SD of G = 7.8 +/- 1.4 liters, or R = 5.6 +/- 1.0 liters, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Cardiac output and skin blood flow in lean and obese individuals during exercise in the heat.

Five obese (% body fat greater than or equal to 27%) and five relatively lean (% body fat less than 20%) men performed upright exercise on a cycle ergometer at intensities of 30, 50, and 70% of their maximal aerobic power [VO2max (ml X kg fat-free wt-1 X min-1)] in both a thermoneutral [dry bulb temperature (Tdb) = 22 degrees C, wet bulb temperature (Twb) = 14 degrees C] and a hot (Tdb = 38 degrees C, Twb = 20 degrees C) ambient environment. Cardiac output (Q) was measured by CO2 rebreathing and forearm blood flow (FBF) was measured by venous occlusion plethysmography. Esophageal temperature (Tes) was measured by a thermocouple placed in the esophagus at approximately heart level, and mean skin temperature (Tsk) was calculated from the average of thermocouple readings from six skin sites. When the exercise intensity was normalized for metabolic body mass by dividing by fat-free weight, Q was similar between lean and obese at all exercise intensities and in both ambient environments. No differences between the two groups were found in Tes and Tsk under all conditions. The obese had significantly lower FBF compared with the lean during the higher exercise intensities in the hot ambient environment. In both ambient environments, the slope of the FBF-Tes relationship was significantly less in the obese group. It was concluded that body composition may alter the balance between the two opposing sets of cutaneous vascular reflexes (baroreceptor-induced vasoconstriction and thermoregulatory vasodilation) that regulate the competition for blood flow between the skin and working muscle during exercise in the heat.

Adult↗
PubMed1983

Body composition and the expiratory reserve volume in lean and obese men and women.

The expiratory reserve volume (ERV) of the lungs was determined in 40 women and 34 men over a wide range of age (18-58 years) and percent body fat (3.6-48.6 percent). A negative correlation with percent body fat resulted when the ERV values were expressed as a percent of the vital capacities (ERV/VC . 100). The regression equations were: for women, ERV/VC . 100 = 49.5 -0.63 %F, r = -0.70, SEE = 7.77; for men, ERV/VC . 100 = 48.7 -0.80 %F, r = -0.78, SEE = 6.05. No significant correlation with age or height was found for either sex.

Adipose Tissue↗
PubMed1983

Body composition, physical work capacity and physical activity habits at 18-month follow-up of middle-aged women participating in an exercise intervention program.

Thirty-six sedentary women (29-47 yr) participated in a 12-week, 4-d/week physical conditioning program (CP) involving 15-25 min/d of walking/jogging at a heart rate corresponding to 75 percent of aerobic capacity (VO2max). Twenty-three were classified obese (O, greater than 30 percent body fat, mean = 38 percent) and 13 normal (N, less than 30 percent body fat, mean = 25 percent). Significant post-CP changes included increased VO2max and decreased body fat. At 18 months post-CP a volunteer subgroup of the original 36 subjects (Ss) were re-evaluated, 19 being hydrostatically weighed, 21 exercise-tested and 28 interviewed to assess physical activity over the preceding eight quarterly periods. At CP termination 80 percent of N and 78 percent of O had intended to continue jogging, but by follow-up only 40 percent of N and 33 percent of O were so engaged, none at CP frequency, many at reduced duration and intensity. There was no significant difference between follow-up and pre-CP mean h/week of jogging for the entire follow-up group, even though eight of them (28 percent) increased their jogging over pre-CP levels. Follow-up VO2max and percent body fat means were also not significantly different from pre-CP values. It is suggested that the majority of middle-aged women participating in supervised walk-jog conditioning interventions may regress to pre-program physiologic status when left to exercise ad libitum.

Adult↗
PubMed1982

Aerobic capacity during acute exposure to simulated altitude, 914 to 2286 meters.

In order to systematically assess the effects of acute exposure to moderate hypoxia on aerobic capacity (VO2max), 12 men (regular participants in recreational distance running) performed six treadmill-graded exercise tests (GXTs) in a hypobaric chamber. GXTs 1 and 6 were performed at ambient (control) altitude (362 m, barometric pressure = 730 mmHg). GXTs 2-5 were administered during 1-2 h of exposure to barometric pressures of 681, 656, 632, and 574 mmHg simulating altitudes of 914, 1219, 1524, and 2286 m, respectively, with the order of presentation randomized and blinded for each subject. The mean VO2max for GXTs 1 and 6 (control altitude) were essentially identical with a test-retest correlation of r = 0.92. During peak exercise, HR max was unchanged by hypoxia, while VO2max was significantly lower than the control by 4,8, 6.9, and 11.9% at 1219, 1524, and 2286 m, respectively. SaO2@max percent during maximal exercise was significantly reduced from the control by 3.5, 3.6, 7.0, and 11.6% at 914, 1219, 1524, and 2286 m, respectively. It was concluded that VO2max, in physically well-conditioned persons living at 362 m, is reduced during acute exposure to 1219 m and above.

Acclimatization↗
PubMed1982

Effects of exercise in cool water on body weight loss.

Seven obese women (greater than 30 per cent body fat, mean = 43 per cent) performed moderate exercise (30 to 40 per cent of maximal oxygen consumption) for 90 min during head-out immersion in cool water (17 to 22 degrees C) five times per week for eight weeks to determine if cold exposure and the attendant caloric deficit in body heat stores would lead to body weight loss. Exercise was on a cycle ergometer that was modified for underwater use. Body weight, body fat, fat-free body weight, and caloric intake did not change significantly as a result of the exercise program in cool water. The significant heat debts incurred were presumably repaid without an increase in energy expenditure. The caloric balance and the thermal data obtained suggest that body heat stores were slowly repaid during recovery by resting metabolic heat production associated with a reduced rate of body heat loss. Maximal oxygen uptake did not increase significantly. No metabolic or thermal evidence was found to support cold adaptation in the obese women. Ergometer exercise in water as well-tolerated, as evidenced by no exercise-related injuries and an adherence rate of 93 per cent. It was concluded that, while cold exposure does not increase caloric expenditure significantly in obese individuals, exercising regularly in cool water may be beneficial as it may motivate obese people to exercise at higher intensity for thermal comfort and the water environment may help prevent injuries.

Adipose Tissue↗
PubMed1981

A comparison of methods of assessment of body composition including neutron activation analysis of total body nitrogen.

Fourteen healthy men underwent determinations of total body nitrogen (TBN) by prompt gamma neutron activation analysis and total body potassium (TBK) by whole body counting to estimate the muscle and nonmuscle components of the fat-free body mass (FFBM) and their protein contents. Comparison of FFBM estimated from TBN and TBK (60.6 +/- 6.9 kg, mean +/- SD), densitometry (62.3 +/- 7.1 kg), TBK alone (62.2 +/- 8.0 kg) and TBW (63.9 +/- 7.8 kg) showed no differences among the techniques. Similarly, there were neither differences in fat mass nor percent body fat among the methods. Analysis of the chemical composition of FFBM of this group showed TBK/FFBM = 62.6 +/- 2.3 mEq/kg, TBW/FFBM = 74.6 +/- 0.2%, TBN/FFBM = 32.74 +/- 1.09 g/kg, protein/FFBM = 20.5+/- 0.7%. The calculated mineral content of the FFBM was 6.4%. These values are strikingly similar to the values calculated by direct chemical analysis. It was concluded that the combined TBN-TBK method is a valid technique for estimating body composition in man.

Adipose Tissue↗
PubMed1981

Relationship between endogenous 3-methylhistidine excretion and body composition.

Fourteen healthy men (aged 20-30 yr) consumed two isocaloric, isonitrogenous diets in the sequence of a 4-day meat diet (MD) followed by a 7-day meal-free diet (MFD). Urinary 3-methylhistidine (3MH) excretion during the MD (513 +/- 21 mumol . day-1, mean +/- SE) was significantly higher (P less than 0.01) than day 3 of the MFD (230 +/- 10 mumol . day-1), after which the mean daily 3MH output was constant with a mean coefficient of variation of 4.5%. There was no change in fat-free body mass (FFBM) determined by densitometry at the start (62.3 +/- 1.8 kg) and the end (62.2 +/- 1.9 kg) of the 11-day dietary period. Mean muscle mass (MM) calculated from measurements of total-body potassium and nitrogen was 23.4 +/- 1.3 kg. Endogenous 3MH excretion was related more closely to MM (r = 0.91, P less than 0.001) than to FFBM measured by densitometry (r = 0.81, P less than 0.001). Only a low correlation coefficient (r = 0.33, P less than 0.05) was observed between 3MH and the nonmuscle component of FFBM. Urinary creatinine output also was correlated significantly with 3MH (r = 0.87; P less than 0.001) and MM (r = 0.79; P less than 0.01). It is concluded that because endogenous 3MH is significantly related to MM in man, it can be used as a marker to study in vivo total-body muscle protein degradation provided that the necessary dietary restrictions are observed.

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↗