ABSTRACT
The purpose of this study was to investigate the accuracy of estimating human body composition changes using bioelectrical impedance (BI) methods during a weight-loss intervention. Subjects were forty-three obese men (age : 49.2±10.5 yr, BMI : 27.8±1.7 kg/m<sup>2</sup>) who completed a 14-week weight-loss intervention. In all subjects, fat mass (FM) and fat-free mass (FFM) were assessed by dual energy x-ray absorptiometry (DXA) as well as single- and multi-frequency BI methods (SBIM, MBIM) before and after the intervention. Resistance parameters were measured by SBIM and MBIM (SBIM : R<sub>50</sub> ; MBIM : R∞, R0, and Rfc). In nine subjects these variables were also measured at weeks 1 and 4. Weight decreased (P<0.05) by -8.0±3.2 kg during the intervention while FFM changes averaged -0.4±1.6 kg (DXA), -2.0±1.5 kg (SBIM), and -1.6±1.7 kg (MBIM). BI methods overestimated FFM before the intervention (before ; DXA : 54.4±4.8 kg, SBIM : 56.5±4.3 kg, MBIM : 55.9±4.5 kg). In nine subjects, FFM measured by SBIM (FFM<sub>SBIM</sub>) and MBIM (FFM<sub>MBIM</sub>) was similar to FFM measured by DXA(FFM<sub>DXA</sub>)(after ; DXA : 54.6±5.4 kg, SBIM : 54.6±3.8 kg, MBIM : 54.6±4.1 kg), although BI methods overestimated the FFM before the intervention (before ; DXA : 54.9±5.1 kg, SBIM : 56.9±3.8 kg, MBIM : 56.3±4.4 kg). The ΔFM<sub>SBIM</sub> and ΔFM<sub>MBIM</sub> were highly correlated with the ΔFM<sub>DXA</sub>(SBIM : r=0.87, MBIM : r=0.88). The ΔFFM<sub>SBIM</sub> andΔFFM<sub>MBIM</sub> were significantly correlated with the ΔFFM<sub>DXA</sub>(SBIM : r=0.54, MBIM : r=0.49). The ΔR<sub>50</sub> and ΔRfc were also significantly correlated with the ΔFFM<sub>DXA</sub>(R<sub>50</sub> : r=-0.63, Rfc : r=-0.48). These results suggest that during a weight-loss intervention, 1) BI methods and DXA provide similar estimates of human body composition change, although they overestimate FFM in obese men, and 2) changes of resistance parameters observed with BI methods may estimate human body composition change more accurately.
ABSTRACT
A number of studies have shown that sleep disordered breathing (SDB) has a strong relation with obesity. The purpose of this study was to examine the effect of a short-term weight-loss program in obese men with SDB. In our 14-week weight-loss program, forty-one obese men (mean±SD, age ; 49.6±10.8 yr, body mass index ; 27.9±2.5 kg/m<sup>2</sup>) were assigned to 2 subgroups : diet only (DO ; n=19) and diet plus aerobic exercise (DE ; n=22). 2%, 3%, and 4% oxygen desaturation index (ODI) were measured by pulse oximetry before and after the weight-loss program. Weight and %fat significantly (<i>p</i><0.05) decreased in the total subject pool consisting of DO plus DE (weight ; -8.4±3.5 kg, %fat ; -7.5±3.5%). 2%, 3%, and 4% ODI significantly decreased by -3.46±5.01 event/hour, -2.37±3.57 event/hour, and -1.99±2.84 event/hour, respectively. Significant correlations were found between 2%, 3%, and 4% ODI at baseline and changes of 2%, 3%, and 4% ODI during the weight-loss program (2% ODI ; r=0.48, 3% ODI ; r=0.51, 4% ODI ; r=0.67). Weight loss and %fat loss did not differ significantly between DO and DE (DO : -7.6±3.2 kg, -6.8±3.2%, DE : -9.2±3.7 kg, -8.1±3.7%). The increase in maximal oxygen uptake was slightly larger for DE (4.7±4.6 ml/kg/min) compared to DO (2.5±3.3 ml/kg/min), but there was no significant interaction. Changes of 2%, 3%, and 4% ODI did not differ significantly between groups. These results suggest that for obese men with SDB, the weight-loss program is an effective method, leading to improvement in SDB, although the combination of aerobic exercise to diet may not produce additional effects to SDB, compared with the diet only.
ABSTRACT
The purpose of this study was to compare estimates of human body composition determined from single-frequency bioelectrical impedance methods (S-BIM) and multi-frequency bioelectrical impedance methods (M-BIM) . The human body composition was assessed by dual energy X-ray absorptiometry (DEXA), 5 brands of S-BIM, and 2 brands of M-BIM. Forty-five women, aged 26-58 years, served as subjects. The S-BIM and M-BIM fat-free mass (FFM) estimates were highly correlated with the FFM measured by DEXA (r=0.82-0.93) . The standard errors of estimate (SEE) for FFM were approximately 2 kg. With the exception of the MLT-100 (which slightly underestimated FFM), all brands of BIM slightly overestimated FFM. The absolute mean differences between FFMDEXA and each of the 7 BIM estimates ranged from -3.02 kg to 3.46 kg. Although the 7 brands of BIM provided slightly different estimates, the results of this study suggest that 5-BIM and M-BIM are relatively valid in human body composition.
ABSTRACT
The purpose of this study was to compare estimates of human body composition determined from single-frequency bioelectrical impedance methods (S-BIM) and multi-frequency bioelectrical impedance methods (M-BIM) . The human body composition was assessed by dual energy X-ray absorptiometry (DEXA), 5 brands of S-BIM, and 2 brands of M-BIM. Forty-five women, aged 26-58 years, served as subjects. The S-BIM and M-BIM fat-free mass (FFM) estimates were highly correlated with the FFM measured by DEXA (r=0.82-0.93) . The standard errors of estimate (SEE) for FFM were approximately 2 kg. With the exception of the MLT-100 (which slightly underestimated FFM), all brands of BIM slightly overestimated FFM. The absolute mean differences between FFMDEXA and each of the 7 BIM estimates ranged from -3.02 kg to 3.46 kg. Although the 7 brands of BIM provided slightly different estimates, the results of this study suggest that 5-BIM and M-BIM are relatively valid in human body composition.
ABSTRACT
A study was conducted to determine the accuracy of body composition prediction equations using the bioelectrical impedance (BI) method and skinfold thickness (ST) method for predicting longitudinal alterations in the body composition of schoolchildren. Seventeen healthy junior high school boys, aged 12 to 13 yr, participated in the study. Body density (Db) was determined by underwater weighing (UW) . Impedance was measured using a portable four-terminal impedance plethysmograph (800 μA, 50 kHz ; Selco, SIF-891) . Db values by the BI method were estimated from the equations developed for schoolchildren by Watanabe et al. (1993) and Kim et al. (1993) . Db by the ST method was estimated from the equations developed for schoolchildren by Nagamine et al. (1974) and Watanabe et al. (1993), using the sum of skinfold thickness at the triceps and subscapular area. Skinfold thickness was measured on the right side of the body with an Eiken-type skinfold caliper. The changes in Db and body fat measured by UW were small every year. The fat free mass (FFM) measured by UW increased significantly every year. The body composition (average Db, body fat and FFM) values estimated by the BI and ST methods showed no significant differences against average UW values. However, these average values estimated using the equation of Nagamine et al. (1974) were significantly different from the average UW values. The absolute amount of change in FFM (Δ FFM) estimated from BI and ST methods were correlated significantly with absolute amount of change in FFM (Δ FFM) determined by UW. In particular, the accuracy of body composition prediction equations for the BI method (r<SUP>2</SUP>= 0.81 for Watanabe et al., r<SUP>2</SUP> = 0.77 for Kim et al.) was higher than that of body composition prediction equations for the ST method (r<SUP>2</SUP>=0.41 for Nagamine et al., r<SUP>2</SUP>= 0.55 for Watanabe et al) . The findings of this study suggest that the body composition prediction equations based on the BI method are useful for valid assessment of longitudinal alterations in the body composition of schoolchildren.
ABSTRACT
The tetrapolar bioelectrical impedance (BI) method has been proposed as a convenient, valid approach for estimating the body composition of normal healthy adults. However, the validity of the BI method has not yet been confirmed for Japanese junior high school boys and girls. The purpose of this study was to develop convenient and useful equations for predicting the body composition in junior high school boys and girls by the BI method. The subjects were 297 healthy boys and girls, aged 12.15 years, all of whom were Japanese. Impedance was measured using a tetrapolar bioelectrical impedance plethysmograph (800 pA, 50 kHz SIF-891) manufactured by Selco. Multiple regression analysis was used to derive prediction equations for Db that were specifically applicable to boys and girls. The effective prediction equations for Db were as follows : 1) Db=1.1860-0.1282 (Wt·Z) /Ht<SUP>2</SUP>, and 2) Db=1.1402-0.0706 (Wt·Z) /Ht<SUP>2</SUP>-0.0007· (abdomen) for boys. 1) Db=1.1337-0.0778 (Wt·Z) /Ht<SUP>2</SUP>, and 2) Db=1.1124-0.0498 (Wt·Z) /Ht<SUP>2</SUP>-0.0006· (subscapular) for girls, where Db=body density (g/ml), Wt=weight (kg), Z =impedance (ohms), Ht=height (cm) . Db estimated by each respective equation was highly correlated with body density measured by underwater weighing (UW-Db) : 1) r=0.881, SEE=0.00868/ml, 2) r=0.902, SEE=0.00788/nil for boys and 1) r= 0.741, SEE=0.0101 g/ml, 2) r=0.775, SEE =0.0095g/ml for girls. Furthermore, in a cross-validation analysis of prediction equations for Db, another sample consisting of 40 boys and 66 girls was used. Db estimated from each respective equation was correlated highly with UW-Db : 1) r=0.856, 2) r=0.887 for boys and 1) r=0.837, 2) r=0.860 for girls. There were no significant differences between the mean Db obtained by the BI method and that by the criterion method. We suggest that the prediction equations proposed in this study are useful for valid assessment of body composition of Japanese junior high school boys and girls aged 12 through 15 years.
ABSTRACT
A study was conducted to investigate the validity of skinfold-based prediction equations for body density (Db, g/m<I>l</I>) developed by Nagamine et al. (1974), and to formulate convenient, useful equations for predicting Db by the skinfold thickness (ST) method in junior high school boys and girls. The subjects of the study were 269 healthy boys and girls, aged 12-15 years. The dependent variable, Db, was determined by underwater weighing (UW) . Independent variables included single skinfold thickness at three sites (triceps, subscapular and abdomen) and the sum of two skinfolds. Db by the ST method was estimated from the equations developed by Nagamine et al. (1974) for boys and girls, using the sum of skinfold thickness at the triceps and subscapular area. Skinfold thickness was measured on the right side of the body with an Eiken-type skinfold caliper. Db estimated by the ST method was correlated significantly with Db determined by UW (r=0.873 for boys and r=0.723 for girls) . However, average Db values estimated by the ST method were significantly lower than those deter-mined by UW (differences in Db values when predicted by the Nagamine equations: 0.0099 for boys and 0, 0114 for girls) . Therefore, we developed linear regression equations for predicting Db. The best-fitting prediction equation for Db was Db=1.0881-0.0010·X for boys, and Db=1.0715-0.0007·X for girls, where X is the sum of the triceps and subscapular skinfold thickness (mm) for boys and girls. Db estimated from the respective equation was correlated significantly with hydrodensitometrically determined Db (r=0.872, SEE=0.0089 for boys; r=0.722, SEE=0.0104 for girls) .<BR>Furthermore, in a cross-validation analysis of prediction equations for Db developed in the present study, Db estimated from the respective equation was correlated highly with hydrodensitometrically determined Db (r=0.887 for boys and r=0.740 for girls) . There were no significant differences between the Db values predicted by the ST method against hydrodensitometrically determined Db values (difference values: 0.0012 for boys and 0.0013 for girls) . The final phase of this study was to develop more stable equations, combining validation and cross-validation samples. On the basis of the final analyses, we recommend the equations Y=1.0875-0.0010X and Y=1.0716-0.0007X, with SEE of 0.0088g/m<I>l</I> for boys and 0.0105g/m<I>l</I> for girls, respectively. It is suggested that the prediction equations finally developed in the present study will be applicable to junior high school boys and girls.
ABSTRACT
Several prediction equations for estimating body composition of Japanese men and women have recently been developed using a linear regression model with a combination of impedance and anthropometric measurements as independent variables. The purpose of this study was to determine the cross-validity of body density (Db) estimated from bioelectrical impedance (BI) and skinfold thickness (ST) methods in comparison with underwater weighing (UW) as a criterion reference method. Percentage body fat (%BF) was derived from Db according to the equation Brozek et al. Fifty-seven healthy Japanese women, aged 19 to 57 years, volunteered to participate in the study. Impedance was measured by use of a portable four-terminal impedance plethysmograph (Selco, SIF-891) . %BF derived from the BI method (r=0.860-0.875) was correlated with hydrodensitometrically determined %BF to a greater extent than %BF obtained using the ST method (r=0.7330.758) or ultrasound method (r=0.536-0.721) . Correlations of various anthropometric indices (r=0.655-0.691) with hydrodensitometrically determined %BF were even lower. It was noteworthy, however, that mean %BF derived from existing BI equations differed significantly from hydrodensitometrically determined mean %BF. Therefore, we attempted to develop a new equation that was applicable to Japanese adult women as follows: Db=1.1613-0.1038 (Wt⋅Z ) /Ht<SUP>2</SUP>, where Wt=weight in kg, Z=impedance in ohms, and Ht=height in cm. The prediction accuracy of this equation was r=0.866 or SEE=0.0077 g/ml. Cross-validation of this equation on a different sample (122 Japanese women, aged 18 to 59 years) revealed a correlation of r=0.869 in terms of %BF, SEE=3.2%, and no significant difference between estimated %BF and the criterion. We suggest that the BI method is one of the most convenient, valid means of assessing human body composition, and that the newly developed BI equation could be useful particularly when the subjects are Japanese adult women in their late teens to fifties.
ABSTRACT
In previous assessments of body composition by whole body bioelectrical impedance (BI) analysis, electrodes have almost always been placed on the right side of the body. In fact, the most commonly used equations of Lukaski et al, were developed using BI measurements obtained on the right side of the body. However, in some individuals with traumatic injury or orthopedic problems, it would sometimes be necessary to measure BI on the right left side of the body. In the present study, we investigated the effects of electrode placement on BI and the derived percentage body fat. Subjects were 72 nontrained, healthy adult women : age ; 28.1±12.6 yr (1866), height ; 156.3±6.0cm, weight ; 50.5±7.7 kg, percentage body fat ; 24.4±5.2%. BI was measured for each subject in a supine position by use of a Selco SIF-881 plethysmograph (800 μA, 50 kHz) and ECG electrodes (Nikon Kohden) . The tetrapolar configuration was adopted in order to minimize contact impedance or skin-electrode interation. Eating and exercise were prohibited for at least 3 h prior to assessment. The effects of electrode placement were determined under four conditions: 1) the right arm and right leg (R side), 2) the right arm and left leg (R side-L side), 3) the left arm and right leg (L side-R side), 4) the left arm and left leg (L side) . Body density was predicted from the equation developed by Nagamine et al., and percentage body fat was derived from the body density according to Brozek et al. There were significant differences in BI values among the four conditions. Dominant side BI values were significantly lower than those on the non-dominant side. Percentage body fat values estimated under four different BI test conditions (i, e., R, R-L, L-R, and L) in terms of electrode placement were found to be highly correlated (r= 0.9420-0.956) with hydrodensitometrically determined percentage body fat. However, the mean percentage body fat on the dominant side of the body were significantly lower than that on the non-dominant side. We suggest that electrodes can be placed either on the dominant side or on the non-dominant side of the body for normal individuals, assuming that the lowest value from the four combinations of measurements can be used as the criterion value of BI. When the subjects are athletes, BI values obtained on the dominant side or a mean of the values measured on both sides should be adopted.
ABSTRACT
Recently, bioelectrical impedance analysis systems (BIA) have become available for determination of human body composition. The validity of BIA has been found to be sufficiently in the American population. However, more work is needed to assess the validity and applicability of BIA to the Japanese population. The purposes of this study were (1) to test the validity of body composition measured by BIA in comparison with the underwater weighing criterion method, and (2) to develop a convenient equation that would reliably predict body composition using BIA and anthropometric measurements in Japanese females. The subjects were 226 Japanese women and girls aged 11 to 55 years (23.9±8.3) . Body impedance was measured using a tetrapolar electrode method, with a localized 800-μA and 50-kHz current injection (Selco SIF-881) . The percentage of body fat (%fat) estimated by BIA was significantly correlated with densitometrically determined %fat (r=0.793, Lukaski et al, method ; and r=0.800, Segal et al, method) . The magnitude of these correlations was substantially higher when compared with r=0.615 found between the skinfold thickness method and the criterion method. Absolute %fat values estimated by BIA were, however, significantly lower than those determined by the criterion method, thereby indicating the need for a more accurate method of assessing Japanese body composition. For this, we propose the use of D=1.1303-0.0726 (Wt×R/Ht<SUP>2</SUP>), where D=body density in g/m<I>l</I>, Wt=body weight in kg, R= (R<SUP>2</SUP>+Xc<SUP>2</SUP>) <SUP>0.5</SUP> in ohms, and Ht=body height in cm. Lean body mass (LBM) and %fat predicted from this equation were correlated significantly (r=0.924 and r=0.799, respectively) with values determined by densitometry. The standard error of estimates of LBM and %fat resulted in figures of 1.9 kg and 3.7%, respectively. Thus we suggest that BIA is valid, convenient, and inexpensive, and that the prediction equation proposed in this study is useful for assessment of body composition in Japanese adult females.
ABSTRACT
The present study was undertaken (1) to evaluate to what extent percent body fat predicted from commonly used equations differs from that determined by hydrostatic weighing technique, and (2) to propose sample specific equations to predict percent body fat in obese women. Subjects were 51 adult obese women (23 sedentary women and 28 active women, mostly middle-aged) . Percent body fat (% fat) determined by hydrostatic weighing (densitometry) averaged 33.1±3.7%, while % fat velues (X=27.1-30.0 in sedentary women, 24.2-27.1 in active women, and 25.4-28.4 in all women) predicted from Nagamine equations were significantly lower and correlated in the order of only 0.1 to 0.6 with densitometry %fat. Of the eight equations developed for predicting % fat of obese women, Y=8.87+ 0.223 X<SUB>1</SUB>-0.180 X<SUB>2</SUB> was considered the best choice, where X<SUB>2</SUB>: Katsura Index and X<SUB>2</SUB> : sub-scapular skinfold (mm) . It is recommended that this equation or some other equations developed in the present study be applicable to a wide range of adult obese women. Caution is necessary, however, as to if those equations could be generalized to younger obese women.
ABSTRACT
This study examined if modified Wingate Anaerobic Test (Wingate method) and Evans-Quinney Anaerobic Test (Evan-Quinney method) procedures could be applied to the meas-urement of maximal anaerobic power output (POmax) which is usually determined during 8-s maximal cycling depending predominantly on alactacid energy sources. The criterion measure of POmax was either the highest power output among 5 to 7 power outputs meas-ured at different workloads (Selection method) or the peak power output estimated from quadratic regression (Peak method) . POmax and anaerobic power outputs with these four methods were measured during 8-s maximal cycling on Monark bicycle ergometer with toe-stirrups. Forty-four young athletes (25 males and 19 females) served as subjects. Analysis of the data indicated that: 1) There was a very high correlation (r=0.995, P<0.001) between POmax determined by Selection and Peak methods, with no statistical difference in their absolute means. 2) POmax determined by Wingate method correlated (r=0.937, P<0.001) significantly with POmax determined by Peak method, while mean values differed signif-icantly. 3) POmax determined by Evans-Quinney method also correlated (r=0.890, P<0001) significantly with that determined by Peak method; however, mean values differed significantly and degree of the difference in POmax was particularly greater in females. It is concluded that both Wingate and Evans-Quinney methods with a cycling duration of 8 s might be applicable for the assessment of POmax by utilizing linear regression equations developed in this study. Further studies are needed as to the feasibility of using these methods, particularly on females.
ABSTRACT
Intraindividual variation in oxygen debt was determined following maximumeffort work and a near-maximum-effort work at a given rate by means of the Monark's bicycle ergometer for sixty seconds. Both experiments were carried out four times, respectively. At the same time the measurement of work done and rectal temperature at rest were taken. Every experiment was carried out once a day at the same hour (9 : 00) on the moring of Monday.<BR>Intraindividual variation in oxygen debt, work done and rectal temperature was expressed in terms of a coefficient of variation (C. V.: %) . The subjects were four healthy male students, aged 18-21.<BR>The results obtained are as follows<BR>1) The C. V. value of intraindividual variation in oxygen debt following maximum-effort work was from 4.7% to 15.3% and its mean value was 9.1%.<BR>2) The C. V, value of intraindividual variation of the work done following maximum-effort work was from 0.7% to 2.5% and its mean value was 1.4%.<BR>3) The C. V. value of intraindividual variation in oxygen debt following a nearmaximum-effort work at a given rate was from 7.0% to 12.8% and its mean value was 9.5%.<BR>4) The mean value of the work done following a near-maximum-effort work at a given rate was 85.8% in contradistinction to maximum effort work. The mean value of C.V, of work done was 1.1%.
ABSTRACT
We measured the power that sprinters and non-athletes put out by Monark's bicycle ergometer under eight work loads from light to heavy.<BR>Also we measured the power that was put out when sprinters and non-athletes repeated the work that recorded the maximum power respectively 10 and 9 times.<BR>The results were as follows :<BR>1) Large difference was not found between the largest power of sprinters and that of non-athletes in the works of 3 or 4 kp light work loads. But considerable difference between the largest power of sprinters and that of non-athletes was found as the work loads got on heavy from 5 to 7 kp. Sprinters who had best record of 10''7-10''9 in 100 meters dash put out the maximum power (90.4-105.8kgm/sec) under the work loads of 7 or 8 kp. On the other hand non-athletes put out the maximum power (62.1-85.2kgm/sec) under the work loads of 5 or 6 kp.<BR>2) As the work loads got on heavy from 5 to 7 kp, such a large difference between sprinters and non-athletes was not found in forces, but remarkable difference was found in speed. And sprinters were better in speed under comparatively heavier work loads than non-athletes. This was a factor which caused the large difference in the max-imum power between sprinters and non-athletes.<BR>3) The maximum powers which were put out by all subjects except two sprinters were situated on almost a straight line. But those of two sprinters were situated on the left of that line. This means that two sprinters excelled power output especially in speed.<BR>4) When sprinters and non-athletes repeated the work which put out the maximum power respectively 10 and 9 times, having a rest for 4 minutes between the works, the powers did not indicate great decline from 1 to 910 times in both sprinters and non-athletes. But when they repeated the same work, having a rest for 1 mimute between the works, the powers indicated a considerable decline from about 5 to 910 times in both sprinters and non-athletes. And the rate of those decline did not indicate great difference between sprinters and non-athletes.<BR>5) We found out three types on the power output in both sprinters and non-athletes as follows : (1) compared with the power decline from 4 to 5 sec, the rate of that from 5 to 6 sec was considerably high, (2) the power declined from 4 to 6 sec, and the rate of this decline was comparatively small, (3) the rate of power decline 4 to 6 sec was wholly maintained high.