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P Mayclin

Publications and source records attributed to P Mayclin.

5 recordsLinked to original sources
PubMed1992

Predicting total body water and extracellular fluid volumes from bioelectrical measurements of the human body.

Two biological impedance analyzers, a 50 kHz (RJL) and 20-100 kHz (BMA) instrument, and a total body electrical conductivity (TOBEC) instrument were used to estimate total body water (TBW), extracellular (ECF) and intracellular (ICF) fluid volumes by repeated measurements of 16 normal men (19-38 years old) to assess which, if any, would provide the best estimates. At 3-week intervals, TBW was determined by deuterium dilution, ECF by bromide dilution, ICF by difference (TBW-ECF) and lean body mass by density. Prediction equations were obtained by regression; predicted values for the body fluid volumes were calculated and the results were statistically evaluated. Both the TOBEC and the BMA provided rapid and reliable estimates for body fluid volumes with standard errors of the estimates of about 0.5-1.1 L for ECF, 1.0-1.8 L for TBW, and 1.0-1.3 L for ICF. Part of the error was attributable to standard tracer-dilution methods.

Adult↗
PubMed1987

A new TOBEC instrument and procedure for the assessment of body composition: use of Fourier coefficients to predict lean body mass and total body water.

A second-generation total body electrical-conductivity instrument (TOBEC II) that uses convolution principles was evaluated. This study 1) examined the stability of the instrument, 2) validated the relationship of total body electrical conductivity to isotopically determined total body water (TBW) and densitometrically determined lean body mass (LBM), and 3) developed prediction equations for LBM, TBW, and total body potassium using Fourier coefficients. In a sample of 40 men and women aged 19-35 yr and ranging from 6% to 36% body fat, the correlations among the zero-, first-, and second-order Fourier coefficients (FC0, FC1, FC2) with LBM were r = 0.97, 0.98, and 0.99, respectively. Similarly, the correlations with TBW were r = 0.96, 0.97, and 0.98, respectively. The best prediction equation was for LBM: LBM (kg) = 22.998 + 0.102FC0 + 0.062FC1 - 0.29FC2(R2 = 0.983 and SEE = 1.43 kg).

Adult↗
PubMed1987

TOBEC methodology for body composition assessment: a cross-validation study.

The accuracy of prediction equations for estimating lean body mass (LBM) from total-body electrical conductivity (TOBEC) was examined by cross-validation. Two samples of adults, aged 18-35 yr, were drawn from separate geographic locations. LBM was determined by densitometry and TOBEC was measured with TOBEC II instrument. LBM and TOBEC were highly correlated in both samples (r = 0.96 and 0.97). Cross-validation of LBM prediction equations was accomplished by exchanging equations and comparing predicted LBM values. There was a mean difference of 0.974 kg LBM between the two equations (p less than 0.0001). Thus, data from 157 subjects were pooled and one equation was developed that incorporated height (cm), sex (males = 0, females = 1), and the zero-, first-, and second-order Fourier coefficients (FC0, FC1, and FC2) of the TOBEC phase value: LBM, kg = -36.410 + (-1.324 X sex) + (0.01185 X (FC1(0.5)xht)) + (12.347 X FC2(0.5)) + (0.0627 X FC0)-(0.9232 X FC2) This equation, developed from 157 subjects, accounted for 96% of the variability in LBM and had a standard error of estimate of 2.17 kg LBM.

Adolescent↗
PubMed1987

Diet, exercise, weight loss, and energy expenditure in moderately overweight women.

The effect of a moderate energy intake plus exercise (MEEX) vs a low energy intake without exercise (LESD) on weight loss and energy expenditure was examined in two groups of moderately overweight women confined to a metabolic unit. An initial 2-week baseline period was used to determine weight maintenance energy requirement (ER). This was followed by a 6-week weight reduction period. Energy intake was decreased to 0.75 ER in MEEX and treadmill exercise was individually prescribed to increase energy expenditure to 1.25 ER. Energy intake was decreased to 0.5 ER in LESD. Thus, both energy intake and expenditure were manipulated to result in an energy deficit of 50 percent. Although total weight loss was significantly higher in LESD compared to MEEX (7.8 vs 5.7 kg), fat loss did not differ (5.1 vs 4.7 kg) hence the proportion of weight loss due to fat was greater in MEEX. Aerobic capacity, measured by maximum oxygen uptake, significantly improved in MEEX (2.44 to 2.84 l/min) but did not change in LESD (2.51 to 2.50 l/min). Basal metabolic rate, energy cost of standardized activities, and 3-hour thermic response to a test meal did not change in either group throughout the study. Thus, a 50 percent energy deficit, achieved by either diet alone or diet in combination with exercise, did not result in conservation of energy expenditure in moderately overweight women.

Adipose Tissue↗