PubMed Health⌕ Search

Biomedical subjects

D A Fields

Publications and source records attributed to D A Fields.

13 recordsLinked to original sources
PubMed2001

Effect of scalp and facial hair on air displacement plethysmography estimates of percentage of body fat.

OBJECTIVE: The objective of this study was to determine the effect of body hair (scalp and facial) on air displacement plethysmography (BOD POD) estimates of percentage of body fat. RESEARCH METHODS AND PROCEDURES: A total of 25 men (31.4 +/- 8.0 years, 83.4 +/- 12.2 kg, 181.8 +/- 6.9 cm) agreed to grow a beard for 3 weeks to participate in the study. Total body density (g/cm(3)) and percentage of body fat were evaluated by BOD POD. To observe the effect of trapped isothermal air in body hair, BOD POD measures were performed in four conditions: criterion method (the beard was shaven and a swimcap was worn), facial hair and swimcap, facial hair and no swimcap, and no facial hair and no swimcap(.) RESULTS: The presence of only a beard (facial hair and swimcap) resulted in a significant underestimation of percentage of body fat (16.2%, 1.0618 g/cm(3)) vs. the criterion method (17.1%, 1.0597 g/cm(3), p < 0.001). The effect of scalp hair (no swim cap worn) resulted in a significant underestimation in percentage of body fat relative to the criterion method, either with facial hair (facial hair and no swimcap; 14.8%, 1.0649 g/cm(3)) or without facial hair (no facial hair and no swimcap; 14.8%, 1.0650 g/cm(3), p < 0.001 for both). DISCUSSION: A significant underestimation of percentage of body fat was observed with the presence of facial hair ( approximately 1%) and scalp hair ( approximately 2.3%). This underestimation in percentage of body fat may be caused by the effect of trapped isothermal air in body hair on body-volume estimates. Thus, excess facial hair should be kept to a minimum and a swimcap should be worn at all times to ensure accurate estimates of body fat when using the BOD POD.

Adipose Tissue↗
PubMed2001

Comparison of the BOD POD with the four-compartment model in adult females.

PURPOSE: This study was designed to compare the accuracy and bias in estimates of total body density (Db) by hydrostatic weighing (HW) and the BOD POD, and percent body fat (%fat) by the BOD POD with the four-compartment model (4C model) in 42 adult females. Furthermore, the role of the aqueous and mineral fractions in the estimation of body fat by the BOD POD was examined. METHODS: Total body water was determined by isotope dilution ((2)H(2)0) and bone mineral was determined by dual-energy x-ray absorptiometry. Db and %fat were determined by the BOD POD and HW. The 4C model of Baumgartner was used as the criterion measure of body fat. RESULTS: HW Db (1.0352 g x cm(-3)) was not statistically different (P = 0.35) from BOD POD Db (1.0349 g x cm(-3)). The regression between Db by HW and the BOD POD significantly deviated from the line of identity (Db by HW = 0.90 x Db by BOD POD + 0.099; R(2) = 0.94). BOD POD %fat (28.8%) was significantly lower (P < 0.01) than %fat by the 4C model (30.6%). The regression between %fat by the 4C model and the BOD POD significantly deviated from the line of identity (%fat by 4C model = 0.88 x %fat by BOD POD + 5.41%; R(2) = 0.92). BOD POD Db and %fat showed no bias across the range of fatness. Only the aqueous fraction of the fat-free mass (FFM) had a significant correlation with the difference in %fat between the 4C model and the BOD POD. CONCLUSION: These data indicate that the BOD POD underpredicted body fat as compared with the 4C model, and the aqueous fraction of the FFM had a significant effect on estimates of %fat by the BOD POD.

Absorptiometry, Photon↗
PubMed2000

Validation of the BOD POD with hydrostatic weighing: influence of body clothing.

OBJECTIVE: Whole body air-displacement plethysmography (BOD POD), a new body composition technique, was validated against hydrodensitometry (UWW) in 67 women wearing a one-piece swimsuit (OP) who represent a wide range of body fatness and age. Additionally, the effect of trapped isothermic air in clothing while in the BOD POD was examined by comparing different clothing schemes (a one-piece swimsuit (OP), two-piece swimsuit (TP), a hospital gown (HG), and a hospital gown previously included in a volume calibration (GC)) in a subset of 25 women. DESIGN: Cross-sectional data analysis. SUBJECTS: 67 healthy Caucasian females. MEASUREMENTS: Body density g/cm3 (Db) by BOD POD and UWW. RESULTS: In 67 females UWW Db (1.030+/-0.020 g/cm3) was higher (P<0.01) than BOD POD Db (1. 028+/-0.020 g/cm3). This is a difference of 1.0% fat. The R2 was 0. 94, SEE was 0.005 g/cm3 and the regression between Db by UWW and BOD POB did not significantly deviate from the line of identity. In the subset group of 25 subjects, OP Db (1.040+/-0.014 g/cm3) and TP Db (1.040+/-0.014 g/cm3) were significantly lower (P<0.01) than UWW Db (1.044+/-0.014 g/cm3) or a difference of 1.9% fat. The R2 was 0.86 and the SEE was 0.005 g/cm3 and the regression between Db by UWW and both OP and TP did not significantly deviate from the line of identity. HG Db (1.056+/-0.016 g/cm3) and GC Db (1.037+/-0.016 g/cm3) were significantly different (P<0.01) from UWW Db (1.044+/-0. 014 g/cm3). This difference in density translates to a difference of 5.5% and 3.2% fat respectively. The regression between Db by UWW and both HG and GC significantly deviated from the line of identity. CONCLUSION: This study supports the use of the BOD POD as a substitute for UWW. However, caution should be made in using the BOD POD if subjects are clothed in anything other than a tight fitting swimsuit.

Adolescent↗
PubMed2000

Total body fat does not influence maximal aerobic capacity.

OBJECTIVE: The objective of this study was to examine the influence of body weight and body composition on aspects of aerobic fitness. Our hypothesis was that increased body weight, specifically increased fat mass (FM), would not limit VO2max relative to fat-free mass (FFM), but would reduce maximal and sub-maximal VO2max relative to body weight. DESIGN: We used data from two ongoing studies. In Study 1 a cross-sectional analysis of 129 children across a wide spectrum of body composition was performed. In Study 2 we examined data from 31 overweight women before and after weight loss. METHODS: VO2max was measured using a treadmill test. Sub-maximal aerobic capacity was evaluated with respiratory exchange ratio (RER), heart-rate (HR), and oxygen uptake relative to VO2max at a given workload (%VO2max). Body composition was assessed using dual energy X-ray absorptiometry (DXA) (Study 1) and a four-compartment model (Study 2). RESULTS: In Study 1, FFM was the strongest determinant of VO2max (r=0.87; P<0.0001). After adjusting for FFM, there was no significant influence of FM on VO2max. After separating children into lean and obese sub-groups, absolute VO2max was significantly higher in the obese (1.24+/-0.27 vs 1.56+/-0.40) and VO2max relative to body weight was significantly lower (44.2+/-3.2 vs 32.0+/-4.1 ml/(kg-min)), whereas there was no significant difference when expressed relative to FFM (57.9+/-5.8 vs 59.2+/-4.9 ml/(kgFFM-min)). Sub-maximal aerobic capacity was significantly lower in the obese children, as indicated by a higher HR and %VO2max; time to exhaustion was significantly lower in the obese children (15.3+/-2.9 vs 11.1+/-2.1 min). In Study 2, FFM was also the strongest determinant of VO2max before and after weight loss. The relationship between VO2max and FFM was identical before and after weight loss so that VO2max relative to FFM was identical before and after weight loss (43.8+/-4.9 vs 45.5+/-6.4 ml/(kgFFM-min)). However, sub-maximal aerobic capacity was lower in the obese state, as indicated by a significantly higher RER (0.85+/-0.06 vs 0.79+/-0.05), HR (124+/-14 vs 102+/-11 bpm), and %VO2max (44% vs 36%). CONCLUSION: The major influence of body weight on VO2max is explained by FFM; FM does not have any effect on VO2max. Fatness and excess body weight do not necessarily imply a reduced ability to maximally consume oxygen, but excess fatness does have a detrimental effect on submaximal aerobic capacity. Thus, fatness and VO2max should be considered independent entities.

Absorptiometry, Photon↗
PubMed2000

Body composition techniques and the four-compartment model in children.

The purpose of this study was to compare the accuracy, precision, and bias of fat mass (FM) as assessed by dual-energy X-ray absorptiometry (DXA), hydrostatic weighing (HW), air-displacement plethysmography (PM) using the BOD POD body composition system and total body water (TBW) against the four-compartment (4C) model in 25 children (11.4 +/- 1.4 yr). The regression between FM by the 4C model and by DXA deviated significantly from the line of identity (FM by 4C model = 0.84 x FM by DXA + 0.95 kg; R(2) = 0.95), as did the regression between FM by 4C model and by TBW (FM by 4C model = 0. 85 x FM by TBW - 0.89 kg; R(2) = 0.98). The regression between FM by the 4C model and by HW did not significantly deviate from the line of identity (FM by 4C model = 1.09 x FM by HW + 0.94 kg; R(2) = 0. 95) and neither did the regression between FM by 4C (using density assessed by PM) and by PM (FM by 4C model = 1.03 x FM by PM + 0.88; R(2) = 0.97). DXA, HW, and TBW all showed a bias in the estimate of FM, but there was no bias for PM. In conclusion, PM was the only technique that could accurately, precisely, and without bias estimate FM in 9- to 14-yr-old children.

Absorptiometry, Photon↗
PubMed2000

Resistance training increases total energy expenditure and free-living physical activity in older adults.

The purpose of this study was to determine what effects 26 wk of resistance training have on resting energy expenditure (REE), total free-living energy expenditure (TEE), activity-related energy expenditure (AEE), engagement in free-living physical activity as measured by the activity-related time equivalent (ARTE) index, and respiratory exchange ratio (RER) in 61- to 77-yr-old men (n = 8) and women (n = 7). Before and after training, body composition (four-compartment model), strength, REE, TEE (doubly labeled water), AEE (TEE - REE + thermic response to meals), and ARTE (AEE adjusted for energy cost of standard activities) were evaluated. Strength (36%) and fat-free mass (2 kg) significantly increased, but body weight did not change. REE increased 6.8%, whereas resting RER decreased from 0.86 to 0.83. TEE (12%) and ARTE (38%) increased significantly, and AEE (30%) approached significance (P = 0.06). The TEE increase remained significant even after adjustment for the energy expenditure of the resistance training. In response to resistance training, TEE increased and RER decreased. The increase in TEE occurred as a result of increases in both REE and physical activity. These results suggest that resistance training may have value in increasing energy expenditure and lipid oxidation rates in older adults, thereby improving their metabolic profiles.

Aged↗
PubMed2000

Aerobic fitness, not energy expenditure, influences subsequent increase in adiposity in black and white children.

BACKGROUND: Low levels of energy expenditure and aerobic fitness have been hypothesized to be risk factors for obesity. Longitudinal studies to determine whether energy expenditure influences weight gain in whites have provided conflicting results. To date, no studies have examined this relationship in blacks or whether aerobic fitness influences weight gain in white or black children. METHODS: One hundred fifteen children, 72 white (55 girls and 17 boys) and 43 black (24 girls and 19 boys) were recruited for this study. Aerobic fitness, resting, total, and activity-related energy expenditure and body composition were measured at baseline. The children returned annually for 3 to 5 repeated measures of body composition. The influence of the initial measures of energy expenditure and fitness on the subsequent rate of increase in adiposity was examined, adjusting for initial body composition, age, ethnicity, gender, and Tanner stage. Because 20 children did not attain maximum oxygen consumption, the sample size for the combined analysis was 95. RESULTS: Initial fat mass was the main predictor of increasing adiposity in this cohort of children, with greater initial fat predicting a higher rate of increase of adiposity. There was also a significant negative relationship between aerobic fitness and the rate of increasing adiposity (F(1,82) = 3.92). With every increase of.1 L/minute of fitness, there was a decrease of.081 kg fat per kg of lean mass gained. None of the measures of energy expenditure significantly predicted increasing adiposity in white or black children. CONCLUSIONS: Initial fat mass was the dominant factor influencing increasing adiposity; however, aerobic fitness was also a significant independent predictor of increasing adiposity in this cohort of children. Resting, total, or activity-related energy expenditure did not predict increasing adiposity. It seems that aerobic fitness may be more important than absolute energy expenditure in the development of obesity in white or black children. energy expenditure, fitness, longitudinal, obesity.

Adipose Tissue↗
PubMed1997

The influence of muscle group location and race on the relationship between muscle strength and power.

OBJECTIVE: This study investigated the influence of muscle group location and racial background on the relationship between measures of muscle strength and power. It was hypothesized that both African American (AA) and Caucasian American (CA) males would exhibit similar strength-power relationships, but these relationships would be dependent upon muscle group location. EXPERIMENTAL DESIGN: A cross-sectional, comparative design was used. SETTING: The Human Performance Laboratory at the U. of Oklahoma. SUBJECTS: Normal, healthy college-aged AA (n = 14) and CA (n = 15) males volunteered for this study. MEASURES: Upper and lower body strength (IRM) was assessed using a Smithpress bench press and Polaris leg press, and upper and lower body power was measured with a piezoresistive accelerometer. RESULTS: When comparing power between upper and lower body muscle groups, both AA and CA groups exhibited similar relationships (r = 0.68 and r = 0.61, respectively), however, the relationship between upper and lower body strength was relatively stronger for the AA group (r = 0.65 vs r = 0.42). When evaluating the strength-power relationship within a given muscle group, i.e., upper or lower body, there were no racial differences, but the relationship between strength and power did differ with respect to muscle group location. CONCLUSIONS: There were stronger relationships between measures of muscular strength and power for the lower limbs when compared to the upper body indicating the importance of muscle group location rather than racial ethnicity as a confounding factor that can affect neuromuscular force production. This information is important when attempting to characterize neuromuscular function relative to specific skills or motor sport performance, thus emphasizing the principle of specificity.

Acceleration↗
PubMed1984

Inhibition by azelastine of nonallergic histamine release from rat peritoneal mast cells.

The ability of azelastine and selected antiallergic drugs to inhibit compound 48/80-induced and PS-potentiated, Con A-induced histamine release from RPMC was investigated. Azelastine, ketotifen, theophylline, and DSCG added simultaneously with the secretagogues or preincubated with the RPMC for 10 min before the addition of secretagogues produced concentration-dependent inhibition of histamine release. In general, the relative order of potency at calculated IC50 level was as follows: azelastine greater than ketotifen greater than theophylline greater than DSCG. The preincubation of RPMC with azelastine for 10 min exerted 3.5 times greater inhibition of Con A plus PS-stimulated histamine release but did not influence the inhibitory activity on compound 48/80-induced release. The duration of preincubation did not influence the inhibitory effects of ketotifen with either secretagogue. Theophylline and DSCG exerted significantly greater inhibition when they were added simultaneously with Con A plus PS. The inhibitory activity of DSCG was also significantly improved upon simultaneous addition with compound 48/80. These data demonstrated that azelastine is the most potent inhibitor of nonallergic histamine release from RPMC among the four antiallergic drugs examined.

Animals↗
PubMed1976

Characterization of a ts beta' mutant RNA polymerase of Escherichia coli.

RNA polymerase isolated from ts XH56, a conditional lethal mutant unable to grow and synthesize RNA at 42 degrees, was found to be temperature sensitive in vitro. The mutation affects the beta' subunit as determined by mixed reconstitution of isolated subunits from wild-type and mutant enzyme. The mutant RNA polymerase is unstable; addition of glycerol stabilizes the enzyme and increases its activity on native DNA. In addition, the mutant enzymes is sensitive to high ionic strength. Both high temperature and high ionic strength do not affect chain elongation; thus, the mutation renders the enzyme unable either to bind to or melt out promotor sites. From these data we conclude that the beta' subunit plays an important role in promotor selection.

DNA, Bacterial↗