Bioelectrical parameters of the whole human body obtained through bioelectrical impedance analysis

Knowledge of electrical properties of body tissues across the frequency spectrum is useful for tissue characterization. The bioelectric impedance analysis method, operating from 1 to 250 kHz (multi-frequency), was used in 23 normal male human subjects between the ages of 21 and 52 years, for estimation of their bioelectrical parameters. Amplitude of the output current was set to 800 microA(RMS). The experimental data showed that bioelectric parameters were highly dependent on frequency and the presence of a threshold frequency around 4 kHz. In order to explain the unusual features observed in our experimental data, the human body was simulated through the Cole-Fricke-Cole model (RC circuit) and the Extended Cole-Fricke-Cole model (RLC circuit). The simulated data showed that the Extended Cole-Fricke-Cole model had a higher accuracy than the traditional Cole-Fricke-Cole model. These results suggest that the unusual features could be due to the possible existence of inductive effects in biological cells and body tissues and that the inductive parameter and the threshold frequency could be used for characterizing the healthy tissues as well as the traditional bioelectric parameters.     

Luteinizing hormone-releasing hormone in prepubertal and pubertal girls.

Estimations of immunoreactive LH-RH and LH in pooled sera of girls, adult women and postmenopausal women have been carried out. The girls were divided into three groups: I--girls aged 2--4 years, II--girls aged 5--8 years and III--girls 9--12 years of age. The estimated concentrations of LH-RH in particular groups were as following: in group I--1.2 +/- 0.2 pg/ml, in group II--2.2 +/- 0.4 pg/ml, in group III 31.0 +/- 4.4 pg/ml, in adult women 6.3 +/- 1.8 pg/ml. and in postmenopausal women 16.6 +/- 2.4 pg/ml. The concentrations of LH in the same groups were 4.3 +/- 0.7; 4.5 +/- 0.8; 11.0 +/- 1.4, 23.3 +/- 2.4; and 120.0 +/- 14.7 mIU/ml, respectively. The authors suggest that the sexual maturation of girls is initiated by the enhanced hypothalamic activity, reflected in higher concentrations of immunoreactive LH-RH in peripheral serum.     

Why boys will be boys and girls will be girls: Human sex development and its defects

Among the most defining events of an individual's life, is the development of a human embryo into male or a female. The phenotypic sex of an individual depends on the type of gonad that develops in the embryo, a process which itself is determined by the genetic setting of the individual. The development of the gonads is different from any other organ, as they possess the potential to differentiate into two functionally distinct organs, testes, or ovaries. Sex development can be divided into two distinctive processes, “sex determination,” which is the commitment of the undifferentiated gonad into either a testis or an ovary, a process that is genetically programmed in a critically timed manner and “sex differentiation,” which takes place through hormones produced by the gonads, once the developmental sex determination decision has been made. Disruption of any of the genes involved in either the testicular or ovarian development pathway could lead to disorders of sex development. In this review, we provide an insight into the factors important for sex determination, their antagonistic actions and whenever possible, references on the “prismatic” clinical cases are given. Birth Defects Research (Part C) 108:365–379, 2016. © 2016 Wiley Periodicals, Inc.     

Reliability and validity of bioelectrical impedance in determining body composition

This study was designed to examine the reliability and validity of the bioelectrical impedance method (BIA) of measuring body composition and compare its accuracy with the results obtained by standard anthropometric methods BIA, skinfold fat, and hydrostatically measured percent fat (% fat) were obtained on 44 women and 24 men. Each subject was tested four times by two testers on two different days. Generalizability theory was used to estimate reliability and measurement error that considered both day-to-day and intertester error. The BIA, skinfold fat, and hydrostatic methods were all found to be reliable (Rxx = 0.957-0.987) with standard errors ranging from 0.9 to 1.5% fat. An additional 26 men (n = 50) and 38 women (n = 82) were tested once and combined with the data used for the reliability analysis to cross-validate BIA estimates of % fat with hydrostatically determined % fat. The cross-validation correlations for the BIA determinations of % fat ranged from 0.71 to 0.76, which were significantly lower than that obtained with the sum of seven (sigma 7) skinfolds equations (rxy = 0.92 for men and 0.88 for women). The correlations between the weight-to-height ratio body mass index (BMI) and hydrostatically determined % fat were 0.75 and 0.74 for men and women, respectively. The standard errors of estimate for the two BIA models ranged from 4.6 to 6.4% fat compared with 2.6 and 3.6% fat for the sigma 7 equations. The BIA method for measuring body composition was comparable to the BMI method, with height and weight accounting for most of the variance in the BIA equation.     

Aerobic power and pubertal peak height velocity in Belgian boys

To determine the cardiorespiratory response to maximal exercise before, during and after the pubescent growth spurt, thirty boys were tested at yearly intervals over a period of six consecutive years. For each individual, peak height velocity (PHV) was determined. The age at PHV (X = 13.6 years) was taken as a standard of maturation. The results from all subjects at 1.5 and 0.5 years before and 0.5 and 1.5 years after PHV are presented. The highest oxygen uptake (VO2) obtained during an incremental bicycle ergometer test to voluntary exhaustion was taken as peak oxygen uptake (VO2 peak). Across each of the four years studied, mean VO2 peak (min = 49.6; max = 52.5 ml.kg-1.min-1) and mean heart rate (HR) at VO2 peak (min = 190; max = 192) did not change significantly as a function of PHV. On the other hand, the respiratory quotient at VO2 peak increased considerably from mean minima and maxima of 0.99 and 1.01 before PHV to 1.07 and 1.10 after PHV. Ventilatory equivalent for VO2 (VE/VO2), taken as an indicator of ventilatory economy, seemed to be unaffected by the maturation process. The steepest increase in circumpubertal oxygen pulse was found one year after PHV. Average stability coefficients (r), calculated from the inter-years correlations were high for height (r = 0.95), weight (r = 0.92), HR at VO2 peak (r = 0.74), VO2 peak in 1/min (r = 0.71), oxygen pulse (r = 0.68) and tidal volume (r = 0.64).     

Effects of different electrodes on bioelectrical impedance values

Effects of different electrodes on bioelectrical impedance values measured by the Selco bioelectrical impedance plethysmograph (SIF-881, Japan) were investigated using 8 adult females (age: 35.3 +/- 7.6 yr, Ht: 156.9 +/- 3.8 cm, Wt: 57.1 +/- 9.9 kg, and hydrodensitometrically determined body fat: 29.4 +/- 6.0%). The Lectec MP3000 electrode (Liberty Carton, USA) and the Bipolar electrode (Sanwa, Japan) produced significantly higher impedance values when compared to the Disposable electrode (Adovance, Japan) and the ECG electrode (Nihon Kohden, Japan). The coefficient of variation was significantly lower for the Disposable electrode (0.8%) and the ECG electrode (0.2%) than that for the Lectec MP3000 electrode (2.3%) and the Bipolar electrode (4.9%). In conclusion, the ECG electrode provides higher bioelectrical impedance values with the highest reproducibility in the assessment of human body composition by the bioelectrical impedance plethysmography.     

Comparison of bioelectrical impedance and BMI in predicting obesity-related medical conditions

Objective : To determine the relative validity of specific bioelectrical impedance analysis (BIA) prediction equations and BMI as predictors of physiologically relevant general adiposity. Research Methods and Procedures : Subjects were >12, 000 men and women from the Third National Health and Nutrition Examination Survey population. We examined the correlations between BMI and percentage body fat based on 51 different predictive equations, blood pressure, and blood levels of glucose, high‐density lipoprotein cholesterol, and triglycerides, which are known to reflect adiposity, while controlling for other determinants of these physiological measures. Results : BMI consistently had one of the highest correlations across biological markers, and no BIA‐based measure was superior. Percent body fat estimated from BIA was minimally predictive of the physiological markers independent of BMI. Discussion : These results suggest that BIA is not superior to BMI as a predictor of overall adiposity in a general population.     

Longitudinal study of anthropometric,skinfold, work,and motor characteristics of boys and girls,three to six years of age

Groups of preschool children were followed longitudinally: boys, n = 36, from 3.48 up to 6.02 years and girls, n = 22, from 3.53 up to 6.03 years. Anthropometric dimensions, skinfold thicknesses, reaction of the cardiovascular system to a work load (modified step test), motor performance, and hand grip strength were measured. Boys had greater values for height, weight, length, and circumferential measures, with the exception of the thigh. Boys had also smaller skinfolds and better performances in 20 meter dash, broad jump, cricket ball throw, and grip strength compared to girls. All anthropometric dimensions increased with age, but these increase did not have the same character. Children became more linear in spite of relatively greater increase in total body weight. Chest and abdomen circumferences increased more in boys during the last year of the study. Skinfold thicknesses decreased significantly in boys, and stayed the same in girls. Motor performance and muscle strength also increased during the experimental period. Pulse rate at rest, during modified step test and recovery period decreased with age, and the economy of cardiac work improved significantly as indicated by step test index and/or cardiac efficiency index. The changes derived from longitudinal observations corresponded to previous results of cross-sectional data.     

Validity of leg-to-leg bioelectrical impedance measurement in highly active women

The aim of this study was to compare the validity of the leg-to-leg bioelectrical impedance analysis (BIA) method with that of anthropometry using hydrostatic weighing (HW) as the criterion test. A secondary objective was to cross-validate previously developed anthropometric regression equations as well as to develop a new regression equation formula based on the anthropometric data collected in this study. Three methods for assessing body composition (HW, BIA, and anthropometric) were applied to 60 women university athletes. The means and standard deviations of age, weight, height, and body mass index (BMI) of athletes were as follows: age, 20.70 +/- 1.43; weight, 56.19 +/- 7.83 kg; height, 163.33 +/- 6.11 cm; BMI, 21.01 +/- 2.63 kg x m(-2). Leg-to-leg BIA (11.82 +/- 2.39) has shown no statistical difference between percentage body fat determined by HW (11.63 +/- 2.42%) in highly active women (p > 0.05). This result suggests that the leg-to-leg BIA and HW methods were somewhat interchangeable in highly active women (R = 0.667; standard error of estimate [SEE] = 1.81). As a result of all cross-validation analyses, anthropometric and BIA plus anthropometric results have generally produced lower regression coefficients and higher SEEs for highly active women between the ages of 18 and 25 years. The regression coefficients (0.903, 0.926) and SEE (1.08, 0.96) for the new regression formulas developed from this study were better than the all the other formulas used in this study.     

Natural selection on anthropometric traits of Estonian girls

Natural selection is a key mechanism of evolution, which results from the differential reproduction of individuals due to differences in phenotype. We describe fecundity selection on 13 anthropometric traits in a sample of 4000–10,000 of Estonian girls, who were born between 1937 and 1962 and measured at around 13 years of age. Direct selection favoured shorter, slimmer and lighter girls with smaller heads, more masculine facial and body shapes and slower rates of sexual maturation. Selection was stabilizing for weight, body mass index and face roundness. Direct selection was absent on two markers of general health and viability – handgrip strength and vital lung capacity – although these traits experience negative indirect selection due to their association with educational attainment. Similarly, indirect selection, mediated by educational attainment, accounted for a significant portion of selection for girls with smaller heads, narrower faces, and higher shoulder/hip ratios. These traits are thus subject to gene-culture coevolution, in that selection on body dimensions arises via cultural and behavioural mechanisms.     

Physical fitness differences between prepubescent boys and girls

The purpose of this study was to analyze in which physical capabilities boys and girls are closer or distant. An additional objective was to find which of the body fat, physical activity, and somatotype factors have a greater effect on prepubescent children's physical fitness. This was a cross-sectional study involving 312 children (10.8 ± 0.4 years). The physical fitness assessment employed sets of aerobic fitness, strength, flexibility, speed, agility, and balance. The boys presented higher values in all selected tests, except tests of balance and flexibility, in which girls scored better. Gender differences in the physical fitness were greatest in the explosive strength of upper (p ≤ 0.01, η(p)(2) = 0.09) and lower limbs (p ≤ 0.01, η(p)(2) = 0.08), although with a medium-size effect of gender, and smaller in the abdominal (p > 0.05, η(p)(2) = 0.007) and upper limbs (p > 0.05, η(p)(2) = 0.003) muscular endurance, and trunk extensor strength and flexibility (p > 0.05, η(p)(2) = 0.001). The endomorphic (p ≤ 0.01, η(p)(2) = 0.26) in the girls, and the ectomorphic (p ≤ 0.01, η(p)(2) = 0.31) and mesomorphic (p ≤ 0.01, η(p)(2) = 0.26) in the boys, had the high-sized effect on the physical fitness. The physical activity in the girls, and the endomorphic and body fat in the boys, did not have a significant effect. These findings can help in the planning of activities that take into account the success and motivation of both boys and girls and thus increase levels of physical activity and physical fitness at school. However, in prepubescent children, one cannot neglect the influence of genetic determinism, observed from the morphoconstitutional point of view.     

Effects of orthostatic fluid shifts on bioelectrical impedance measurements

This study analyzes the effect of orthostatic fluid shift caused by body postural changes on the reliability and stability of bioelectrical impedance. It has been found that following a fluid distribution perturbation caused by postural changes, impedance values change for a period of time that can be longer than the measurement time. Based on these preliminary measurements, it is recommended that new measurement protocols for bioelectrical impedance be developed in order to minimize perturbations on existing fluid distribution, thus increasing the reliability of bioelectrical impedance data.     

Ethnic differences in the relationship between bioelectrical impedance and body size

The present study compared the regression equations of bioelectrical impedance on body size among various groups to investigate potential differences due to ethnicity. Data consisted of 30 Japanese and 28 Caucasoid subjects, and other groups of Aborigines, Danes, Melanesians and Polynesians from literature. The relationship between impedance and body weight fot the groups showed the ethnic difference. In the regression equations for Japanese and Caucasoid, a statistically significant difference was observed between both groups. The regression equation for Japanese was lower in the elevation. This seemed to be attributable to differences in the volume of fat-free mass for the same body build, configuration of the body, and fat-free mass density.