PubMed Health⌕ Search

Biomedical subjects

V H Heyward

Publications and source records attributed to V H Heyward.

31 records · Page 2Linked to original sources
PubMed1995

Predictive accuracy of bioimpedance equations in estimating fat-free mass of Hispanic women.

This study assessed the predictive accuracy of previously published bioelectrical impedance analysis equations for estimating fat-free mass of young (20-39 yr) Hispanic women (N = 29). The reference method was hydrostatic weighing at residual lung volume. Body density was converted to percent body fat using the Siri equation. Resistance and reactance were measured with a Valhalla bioimpedance analyzer. The bioelectrical impedance analysis equations of Lohman, Rising, Stolarczyk, Segal, Gray, and Van Loan were cross-validated. There were significant correlations between criterion and predicted fat-free mass (r = 0.86-0.95) for all equations. The standard error of estimate for each equation was acceptable; however, the total error for the Stolarczyk (3.2 kg) and the Van Loan (4.6 kg) equations exceeded the recommended value (2.8 kg). For all equations, the difference between average criterion and predicted fat-free mass was significant (P < 0.05). However, the mean differences for the Lohman (0.8 kg), Segal (0.8 kg), and Gray (0.9 kg) equations were small. In conclusion, the Segal, Lohman, and Gray equations may have potential for assessing the body composition of healthy, acculturated, Hispanic women.

Acculturation↗
PubMed1994

Predictive accuracy of bioelectrical impedance in estimating body composition of Native American women.

The predictive accuracy of race-specific and fatness-specific bioelectrical impedance analysis (BIA) equations for estimating criterion fat-free mass (FFM) derived from two-component (2C) and multicomponent (MC) models was examined. Body density (Db) of Native American women (n = 151) aged 18-60 y was measured by hydrostatic weighing at residual volume. Total body bone ash was obtained by dual-energy, x-ray absorptiometry. Cross-validation of the Rising (5), Segal (3), and Gray (4) equations against FFM2C yielded high correlation coefficients (0.86-0.95) and acceptable SEEs (1.47-2.72 kg). Cross-validation of these equations against criterion FFMMC, with Db adjusted for total body mineral, yielded similar correlation coefficients (0.82-0.94) and SEEs (1.69-2.80 kg). However, each BIA equation significantly overestimated FFMMC. A new race-specific BIA equation based on an MC model was developed: FFMMC = 0.001254(HT2)-0.04904(R) + 0.1555(WT) + 0.1417(Xc) - 0.0833(AGE) + 20.05 (R = 0.864, and SEE = 2.63 kg).

Adolescent↗
PubMed1993

Body composition of Native-American women estimated by dual-energy X-ray absorptiometry and hydrodensitometry.

In the present sample, the Native-American women varied in age (18-60 y) and fatness (23.0-57.4% BF). The cross-validation analysis for %BF estimated by DXA for this sample yielded a high validity coefficient (r = 0.89), and the average %BFDXA (37.3%) and %BFHW (37.6%) did not differ significantly. The prediction error (3.28% BF) was less than the theoretical expected value, given the wide range in age and fatness in this sample. Thus, it appears that DXA may be a viable alternative method for estimating the %BF of a diverse group of Native-American women. The DXA method is more practical than hydrostatic weighing, especially for subjects who are uncomfortable in the water. Also, DXA estimates of bone mineral may lead to improved estimates of FFB density for different ethnic populations.

Absorptiometry, Photon↗
PubMed1992

Relationship of optical density and skinfold measurements: effects of age and level of body fatness.

We examined relationships between skinfold (SKF) and optical density (delta OD) measurements across age and levels of body fatness (%BF) for 151 women, 20 to 72 years. There were significant (p < .05) relationships between delta ODs and SKFs at all sites, except the thigh. The interaction (SKF x Age) was significant (p < .05) for pectoral and biceps delta ODs. Slope comparisons indicated the relationships for younger (29 years) and older (59 years) women differed significantly from zero and each other (p < .05). Analysis of SKF x %BF interactions revealed that relationships between SKFs and delta ODs at the pectoral and biceps sites for leaner (22% BF) women differed significantly from zero (p < .05) and were larger than those for obese (39% BF) women (p < or = .05). Thus, the relationship between SKFs and delta ODs is stronger for younger and leaner women compared to older and fatter women. These findings may reflect differences in fat layering due to age or body fatness and provide insight as to why the manufacturer's near-infrared (NIR) equation significantly underestimates the %BF of obese women.

Adipose Tissue↗
PubMed1992

Predictive accuracy of three field methods for estimating relative body fatness of nonobese and obese women.

Three methods of body composition assessment were used to estimate percent body fat (%BF) in nonobese (n = 77) and obese (n = 71) women, 20-72 yrs of age. Skinfolds (SKF), bioelectrical impedance (BIA), and near-infrared interactance (NIR) methods were compared to criterion-derived %BF from hydrostatic weighing (%BFHW). Nonobese subjects had < 30% BFHW and obese subjects had > or = 30% BFHW. The Jackson, Pollock, and Ward SKF equation and the manufacturer's equations for BIA (Valhalla) and NIR (Futrex-5000) were used. For nonobese women there were no significant differences between mean %BFHW and %BFSKF, %BFBIA, and %BFNIR. The rs and SEEs were 0.65 and 3.4% BF for SKF, 0.61 and 3.6% BF for BIA, and 0.58 and 3.7% BF for NIR for nonobese subjects. For obese women, mean %BFHW was significantly underestimated by the SKF, BIA, and NIR methods. The rs and SEEs for the obese group were 0.59 and 3.4% BF for SKF, 0.56 and 3.5% BF for BIA, and 0.36 and 3.9% BF for NIR. The total errors of the equations ranged from 5.6 to 8.0% BF in the obese group. It is concluded that all three field methods accurately estimate %BF for nonobese women; however, none of the methods is suitable for estimating %BF for obese women.

Adipose Tissue↗
PubMed1991

Food selection patterns of bodybuilders.

This paper describes the changes in the food selection patterns of male (n = 7) and female (n = 12) bodybuilders as they prepared for competition. Non-competition dietary data were obtained 6 to 17 weeks (M = 12.5 wks) prior to competition using a 3-day food record. Precompetition food intake was recorded for the 3 days preceding competition. Foods were classified using the Exchange System and three additional categories which included desserts, alcoholic beverages, and other beverages. The noncompetition diets of the bodybuilders contained servings from each exchange, with the largest number of selections coming from the meat and bread/starch exchanges. Choices from the milk and meat exchanges were almost exclusively low-fat or lean. Primarily complex carbohydrates and high-fiber foods were selected from the bread/starch exchange. The number of different food items reported over 3 days and the total number of food items were greater in the noncompetition diet than in the precompetition diet. Also, variety among food groups and within some of the exchange groups was less in the precompetition diet. Although there was not much variety in the precompetition diets of the bodybuilders, the average nutrient density of their diets exceeded the Index of Nutritional Quality for all nutrients except calcium and zinc.

Adult↗
PubMed1991

Coronary heart disease knowledge test: developing a valid and reliable tool.

This study tested the validity and reliability of a written test designed to assess knowledge of coronary heart disease (CHD) and its risk factors. The subjects were 93 males diagnosed with CHD. Subjects were classified into a treatment group (n = 48) or a control group (n = 45) based on whether or not they participated in a cardiac rehabilitation program (CRP). An additional 38 subjects were used to pilot test the original form of the knowledge test, which consisted of 80 multiple-choice questions. Content validity was established by a five-member jury of cardiac rehabilitation experts. Each question was rated using a Likert-type scale. Questions that did not receive an average rating of at least four were eliminated. The revised form was pilot tested for validity and internal consistency with the discrimination index (point biserial correlation coefficient) and the Kuder-Richardson formula 20 (KR-20). Questions with a discrimination index of less than 0.14 were eliminated; thus, the final form of the test consisted of 40 questions. Validation of this test yielded difficulty ratings (DRs) between 0 percent and 98 percent, with an average DR of 63 percent. Construct validation indicated that the average test score of subjects participating in a CRP was significantly higher than that of non-participants (t = 3.51, df = 91, p less than or equal to 0.01). The internal-consistency reliability of the test was 0.84. The results indicate that this test is a valid and reliable tool for assessing patients' knowledge of CHD and its risk factors.

Adult↗
PubMed1989

Comparison of body composition, exercise and nutritional profiles of female and male body builders at competition.

Limited research information is available on the training programs and dietary practices of competitive male and female body builders. Information on body composition, training programs, and nutritional profiles of eleven competitive male and female body builders were obtained 48 hours prior to competition. Body composition was assessed by hydrostatic weighing. Skinfold data were obtained to assess the distribution of subcutaneous fat. Questionnaires concerning training programs and a three day food intake record were collected. The female body builders achieved a degree of leanness similar to the males. The relative training volumes for the women were greater than those of the men for all body regions. Gender differences were found in regional deposition of subcutaneous fat between males and females, with the males showing a more uniform distribution of subcutaneous fat. The nutritional profiles of male and female body builders were similar. The pre-competitive diets were low in kilocalories, and the relative energy intakes for men and women were 28.6 kcal/kg and 29.2 kcal/kg respectively. Both men and women consumed low fat and high protein foods. All of the vitamin/mineral intakes of the body builders exceeded the RDA's with the exceptions of calcium for men and women and iron for women only.

Adult↗
PubMed1979

Prediction of maximal oxygen uptake in boys, ages 7-15 years.

Predictions of Vo2max (1 min-1 and ml kg-1 min-1) were obtained via multiple regression procedures from a sample of 100 boys, ages 6.7-14.8 years. Prediction equations for Vo2max (1 min-1) were obtained from the subjects' height, and the Vo2 (1 min-1) and heart rate observed during the third min of a treadmill walk (R = 0.95; CV = +/- 9.3%). A similar prediction was obtained when the subjects' age, height and weight were used (R = -0.94; CV = +/- 9.7%). Vo2max (ml kg-1 min-1) was predicted with similar accuracy (CV = +/- 8.4%) from age, and heart rate, VCO2(1 min-1), Vo2 (ml kg min-1), or from simply age, height and weight (CV = +/- 9.2%). Cross-validation of the equations with another sample of 39 boys demonstrated that the prediction equations based on laboratory data were quite stable, % errors approximately 1-2 +/- 9%. However, the equations based on age, height and weight underestimated the Vo2max slightly, both in 1 min (X = -0.091 min) and ml kg min (X = -2.2 ml kg min, P less than 0.05). The results indicate that reasonably reliable and accurate estimates of Vo2max for children may be obtained from either laboratory data, or simply from their age, height and weight.

Adolescent↗