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Biomedical subjects

A S Jackson

Publications and source records attributed to A S Jackson.

At least 55 records · Page 3Linked to original sources
PubMed1980

A conduit for life.

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Carcinoma, Transitional Cell↗
PubMed1980

Fitness variables and the lipid profile in United States astronauts.

The study examines the relationship between several measures of fitness and the lipid profile in United States astronauts. Data were collected on 89 astronauts, previously selected (PSA) and newly selected (NSA), during their annual physical examinations. Several similarities were seen in the two groups. The PSA (mean age of 46.1) had a lower maximum VO2 (41.7 ml . mg . min-1 vs. 47.5 ml . kg . min-1); when adjusted for age, it was no different from the NSA (mean age 33.5). The PSA had similar body composition with 15.7%--lower than expected for age. The lipid profiles of the two groups were basically the same with the differences being a function of age. Compared to a normative population, the astronauts had similar cholesterols, lower triglycerides, and higher HDLs. The astronaut profiles were generally more favorable than the age-matched controls, which is felt to be a result of the self-supervised conditioning program and annual preventive medicine consultation and education.

Adult↗
PubMed1980

Longitudinal evaluation of an exercise prescription intervention program with periodic ergometric testing: a ten-year appraisal.

The purpose of this investigation was to identify the longitudinal physiological and cardiological changes that occurred in a sample of male NASA executives who participated in an individualized physical conditioning program for 10 years. Only 19% discontinued program participation. Oxygen uptake increased significatnly during the 10 years and the increase was attributed to those who exercised three or more days per week. Serum cholesterol exhibited an upward trend similar to the trend reported in the Framingham population, but systolic blood pressure decreased with age. About 30% of the executives exhibited cardiac arrhythmias during exercise. The incidence of PVCs and PACs increased with age. During the period studied, five executives developed sudden acute myocardial symptomatology which was not detected by the exercise stress test.

Adult↗
PubMed1980

Generalized equations for predicting body density of women.

Previous research with women has shown that body composition regression equations derived from anthropometric variables were population specific. This study sought to derive generalized equations for women differing in age and body composition. The hydrostatic method was used to determine body density (BD) and percent fat (%F) on 249 women in 18 to 55 years (X = 31.4 +/- 10.8 yrs) and 4 to 44 %F (X = 24.1 +/-7.2 %F). Skinfold fat (S), gluteal circumference (C) and age were independent variables. The quadratic form of the sum of three, four and seven S in combination with age and gluteal C produced multiple correlations that ranged from 0.842 to 0.867 with standard errors of 3.6 to 3.8 %F. The equations were cross-validated on a different sample of 82 women with similar age and %F characteristics. The correlations between predicted and hydrostatically determined %F ranged from 0.815 to 0.820 with standard errors of 3.7 to 4.0 %F. This study showed that valid generalized body composition equations could be derived for women varying in age and body composition, but care need to be exercised with women over an age of forty.

Adipose Tissue↗
PubMed1978

Generalized equations for predicting body density of men.

1. Skinfold thickness, body circumferences and body density were measured in samples of 308 and ninety-five adult men ranging in age from 18 to 61 years. 2. Using the sample of 308 men, multiple regression equations were calculated to estimate body density using either the quadratic or log form of the sum of skinfolds, in combination with age, waist and forearm circumference. 3. The multiple correlations for the equations exceeded 0.90 with standard errors of approximately +/- 0.0073 g/ml. 4. The regression equations were cross validated on the second sample of ninety-five men. The correlations between predicted and laboratory-determined body density exceeded 0.90 with standard errors of approximately 0.0077 g/ml. 5. The regression equations were shown to be valid for adult men varying in age and fatness.

Adolescent↗
PubMed1978

A comparison of body fat determined by underwater weighing and volume displacement.

Two hydrostatic techniques, underwater weighing and water displacement, were used to determine body fat for 67 volunteer men between 25 and 61 yr of age (-/x=41 yr). All tests were administered in random order in the morning on the same day while subjects were in the postabsorptive state. Test-retest reliabilities for the underwater weighing and water displacement techniques were 0.995 and 0.96, respectively. The correlation between the two hydrostatic techniques was r=0.96. The mean percent fat determined by underwater weighing (-/x=20.1 +/- 6.4) and water displacement (-/x=19.4 +/- 6.1) were significantly different (t=28.16; df=65; P less than 0.001). These analyses showed that both techniques were reliable in measuring percent body fat, but produced slight systematic differences. Regression equations were provided to adjust for the difference.

Adipose Tissue↗
PubMed1977

Prediction accuracy of body density, lean body weight, and total body volume equations.

The purpose of this study was to determine the accuracy of percent fat estimates derived from regression equations with functions of predicting body density (BD), lean body weight (LBW), and total body volume (TBV) from anthropometric variables. BD, LBW, and TBV equations were derived from the data of 95 young, adult men (percent fat X = 13.4%). The multiple correlations for these equations were: BD, 0.86-0.83; LBW, 0.96-0.95; and TBV, 0.99. The zero order correlations between laboratory determined percent fat and percent fat derived by the BD, LBW, and TBV equations ranged from 0.80 to 0.86 with standard errors from 3.1% to 3.7%. This shows that BD, LBW, and TBV equations have similar accuracy when transformed to percent fat. The derived equations were cross validated with three additional, but diverse, samples (percent fat X = 5.1%; 16.7%; 27.1%). The cross validations results revealed that all equations exhibited similar accuracy. With samples differing in percent fat, systematic prediction errors occurred. The results further confirm population specificity of prediction equations.

Adipose Tissue↗
PubMed1976

Factor analysis and multivariate scaling of anthropometric variables for the assessment of body composition.

This study was designed to identify the body composition factors measured by skinfold fat (S), girth (G), and diameter (D) variables and to provide multivariate scaling models that measure fat (F) and lean body weight (LBW) factors. A total of 7S, 11G, and 7D measurements were determined on 83 young women (YW) and 95 young men (YM). Body density (BD) was determined by the hydrostatic technique. All variables were factor analyzed, and F and LBW were used to validate isolated factors. The YM data showed one F factor and two LBW factors. LBW factor I measured muscle mass and bone structure; LBW factor II, bone D. The YW data isolated four factors: the same three of YM plus a second F factor specific to the pelvic girdle. Factor score models were used to develop scaling strategies to measure F and LBW factors. Full models of all 27 variables and restricted models of 14 S, G, and D variables were developed; the correlations between factor scores scaled from the full and restricted models ranged from 0.84 to 0.98. The multiple correlation between factor scores calculated from the restricted models and laboratory-determined F and LBW ranged from 0.90 to 0.94 for YM and from 0.88 to 0.89 for YW. The multivariate scaling models provide a valid field method of measuring body composition.

Adolescent↗