Multifrequency Bioelectrical Impedance Spectroscopy Research Articles

Effect Of Acute Feeding On Raw Bioimpedance Values And Body Water Estimates In Healthy Adults

Raw bioimpedance values of resistance (R), reactance (Xc), impedance (Z), and phase angle (PhA) are indicators of cell hydration, health, and membrane integrity. There is increasing interest in using these values as indicators of hydration and nutritional status, but effects of acute nutritional intake on raw bioimpedance values is currently unknown. PURPOSE: To determine the effects of acute feeding on raw bioimpedance values and derived body water estimates (total body water [TBW], extracellular water [ECW], intracellular water [ICW]) obtained from multi-frequency bioelectrical impedance spectroscopy (BIS). METHODS: Twenty-nine healthy young adults (59% Female; Age: 21.3 ± 2.7 yrs; Height: 172.5 ± 9.2 cm; Weight: 71.2 ± 10.3 kg) completed three randomly assigned feeding conditions: high carbohydrate (CHO: 116.5 g CHO; 882.5 g total; 0.83 ml fluid), high protein (PRO; 63.5 g PRO; 913 g total; 0.83 ml fluid), and fasted (FAST; 8 hrs fasted). Whole-body, multi-frequency BIS was completed one hour post-meal consumption. Differences in raw bioimpedance values and derived body water estimates between feeding conditions were evaluated using separate repeated measure ANOVAs covaried for average urine specific gravity to account for pre-visit hydration status. RESULTS: There were no significant differences in raw bioimpedance values [R (FAST, CHO, PRO means: 543.0, 545.1, 548.6 Ω; p = 0.418), Xc (67.2, 67.7, 67.7 Ω; p = 0.453), Z (547.2, 549.4, 552.8 Ω; p = 0.416), PhA (7.14, 7.16, 7.12°; p = 0.680)] or derived body water estimates [TBW (40.0, 40.0, 39.8 L; p = 0.289), ECW (16.1, 16.1, 16.1 L; p = 0.131), or ICW (23.9, 23.9, 23.8 L; p = 0.671)] between feeding conditions. CONCLUSION: Acute feeding did not alter raw bioimpedance values taken 1 hr post-meal in healthy young adults. Bioimpedance may not be sensitive to acute changes in nutrition/hydration or consumption of food/drink 1 hr prior to testing was not a long enough equilibration time. Acute food intake may not need to be restricted prior to bioimpedance measurements, which increases feasibility of application in clinical and athletic populations.

Bioelectrical Impedance Analysis Derived-Phase Angle as a Pragmatic Tool to Detect Protein Energy Wasting among Multi-Ethnic Hemodialysis Patients.

Protein-energy wasting (PEW) is a devastating metabolic derangement that leads to increased morbidity and mortality in hemodialysis (HD) patients. This study aimed to determine the diagnostic test accuracy of bioelectrical impedance analysis derived-phase angle (PhA) in detecting PEW among HD patients. This was a multi-centre, cross-sectional study conducted amongst 152 multi-ethnic HD patients in Klang Valley, Malaysia. PEW was assessed using the International Society of Renal Nutrition and Metabolism criteria as the reference method. PhA was measured using a multi-frequency bioelectrical impedance spectroscopy at 50 kHz. Multiple and logistic regressions were used to determine factors associated with PhA and PEW diagnosis, respectively. A receiver operating characteristics curve analysis was used to establish the gender-specific PhA cut-offs to detect PEW. PEW existed in 21.1% of the HD patients. PhA was found as an independent predictor of PEW (adjOR = 0.308, p = 0.001), with acceptable to excellent discriminative performance (adjAUCmale = 0.809; adjAUCfemale = 0.719). Male patients had higher PhA cut-off compared to female patients (4.26° vs. 3.30°). We concluded that PhA is a valid and pragmatic biomarker to detect PEW in multi-ethnic Malaysian HD patients and a gender-specific cut-off is necessary, attributed to the gender differences in body composition.

Are we overfeeding hemodialysis patients with protein? Exploring an alternative method to estimate protein needs.

Sufficient protein intake is of great importance in hemodialysis (HD) patients, especially for maintaining muscle mass. Daily protein needs are generally estimated using bodyweight (BW), in which individual differences in body composition are not accounted for. As body protein mass is best represented by fat free mass (FFM), there is a rationale to apply FFM instead of BW. The agreement between both estimations is unclear. Therefore, the aim of this study is to compare protein needs based on either FFM or BW in HD patients. Protein needs were estimated in 115 HD patients by three different equations; FFM, BW and BW adjusted for low or high BMI. FFM was measured by multi-frequency bioelectrical impedance spectroscopy and considered the reference method. Estimations of FFM x 1.5g/kg and FFM x 1.9g/kg were compared with (adjusted)BW x 1.2 and x 1.5, respectively. Differences were assessed with repeated measures ANOVA and Bland-Altman plots. Mean protein needs estimated by (adjusted)BW were higher compared to those based on FFM, across all BMI categories (P<0.01) and most explicitly in obese patients. In females with BMI >30, protein needs were 69±17.4g/day higher based on BW and 45±9.3g/day higher based on BMI adjusted BW, compared to FFM. In males with BMI >30, protein needs were 51±20.4g/day and 23±20.9g/day higher compared to FFM, respectively. Our data show large differences and possible overestimations of protein needs when comparing BW to FFM. We emphasize the importance of more research and discussion on this topic.

MO047COMPARISON BETWEEN DUAL-ENERGY X-RAY ABSORPTIOMETRY AND BIOELECTRICAL IMPEDANCE FOR BODY COMPOSITION MEASUREMENTS IN ADULTS WITH CHRONIC KIDNEY DISEASE

Abstract Background and Aims Chronic kidney disease (CKD) patients frequently have an altered body composition driven by metabolic disorders from the uremic syndrome that usually leads to increased protein catabolism, with obesity and muscle impairment being common conditions associated with worse clinical prognosis and high mortality rates. Therefore, with increased mortality and disability rates of CKD patients in the last quarter of a century and the association of a poor body composition with low survival, routine and longitudinal assessment of body composition could improve clinical outcomes. Due to limited availability of reference methods to assess nutritional status, alternative methods are used. In view of the above, our goal was to evaluate the agreement between multifrequency bioelectrical impedance spectroscopy (BIS) and Dual-energy X-ray Absorptiometry (DXA) for assessment of body composition in CKD. Method Cross-sectional and prospective analyses by DXA (Hologic, GE®) and BIS (BCM, Fresenius Medical Care®) in whole-body (BISWB) and segmental (BISSEG) protocols were performed in CKD non-dialysis-dependent, hemodialysis and peritoneal dialysis (for at least 3 months), and renal transplantation (for at least 6 months) adult (18 ≤ age ≤ 60 years old) patients. Measurements were performed consecutively by the same professional after an 8-hour fast, drainage of the peritoneal dialysate and just after the midweek hemodialysis session. Intraclass correlation coefficient (ICC) and Bland-Altman plots were evaluated for agreement analysis in group and individual levels, respectively; linear regression analysis was performed for bias assessment and development of new equations; ROC curve was constructed for diagnosis of inadequate error tolerance (DXA - BIS &amp;gt; ± 2kg). Results A total of 266 patients were included: 137 men (M) and 129 women (W); 81 were in non-dialysis-dependent treatment, 83 in hemodialysis, 24 in peritoneal dialysis, and 80 had renal transplantation. Total sample had a mean age of 47 ± 10 years old. CKD was secondary to systemic arterial hypertension in 29% of the total sample, to glomerulonephritis in 25%, to diabetes mellitus in 10%, to polycystic kidney in 7%, to glomerulosclerosis and systemic syndromes in 8%, and to other causes and unknown etiology in 20%. Fourteen patients (4 M and 10 W) were in automated and 9 (4 M and 5 W) in continuous ambulatory PD. KTx was by living donor in 18 (14 M and 4 W) and by deceased donor in 63 (34 M and 29 W) patients. The agreement with DXA was greater for BISWB than BISSEG; for fat mass (FM) (ICC in M = 0.89; ICC in W = 0.93) than for fat free mass (FFM) (ICC in M = 0.57; ICC in W = 0.52). Bland-Altman plots showed high limits of agreement (FFM: from -9.51 to 15.64kg; FM: from -7.71 to 7.32kg) with greater bias for FFM as muscular mass increases and for FM in extremes of body fat. The agreement was lower when using the prospective data (body change analysis) (ICC for FFM in M = 0.20; ICC for FFM in W = 0.49; ICC for FM in M = 0.46; ICC for FM in W = 0.58). The factors that interfered in bias between methods were extra to intracellular water ratio (ECW/ICW), body mass index, fat mass index, waist circumference, resistance and reactance (adjusted r2 for FFM = 0.90; r2 for FM = 0.87). FFM had poorer agreement in the last tertile of ECW/ICW sample (ICC in M = 0.69, 0.68 and 0.51; ICC in W = 0.71, 0.74 and 0.38 for first, second and third tertiles, respectively). An ECW/ICW cut-off point of &amp;gt; 0.725 for inadequate error tolerance was determined. New prediction equations for FFM (r2 = 0.91) and FM (r2 = 0.89) presented adequate error tolerance in 55% and 63% in the validation sample compared to 30% and 39% of the original equation, respectively. Conclusion For body composition evaluation in CKD, BIS applied using the whole-body protocol, in normal hydration CKD patients is as reliable as DXA; BIS must be used with caution among overhydrated patients with ECW/ICW &amp;gt; 0.725. The newly developed equations are indicated for greater precision.

Relationship between total physical activity and physical activity domains with body composition and energy expenditure among Brazilian adults.

The aim of this study was to evaluate the relationship of total physical activity (PA) and its different domains with sex, weight, body mass index, body composition, and resting energy expenditure (REE) among Brazilian adults. The secondary aim was to assess if the Baecke Habitual Physical Activity Questionnaire (BHPAQ) could be used to screen fat mass excess. Three hundred and sixty-six volunteers participated. PA was assessed with the BHPAQ, body composition with multifrequency bioelectrical impedance spectroscopy, and REE with indirect calorimetry. Total PA and sports/exercise PA were lower in women than men. The participants most active for sports/exercise and leisure-time/locomotion PA domains had higher fat free mass and phase angle, and lower fat mass and weight than the least active subjects. The occupational PA domain was associated with higher fat mass and weight. REE was associated only with the exercise/sports PA domain. The BHPAQ could discriminate subjects with excess body fat with a 9.375 cutoff point for total PA. Exercise/sports and leisure-time/locomotion are PA domains associated with a better body composition. A gender gap still exists in PA, as women are less active than men. The BHPAQ could screen subjects with excess fat mass.

Estimation of Body Composition and Water Data Depends on the Bioelectrical Impedance Device.

Overweight, obese and chronic kidney disease patients have an altered and negative body composition being its assessment important. Bioelectrical impedance analysis is an easy-to-operate and low-cost method for this purpose. This study aimed to compare and correlate data from single- and multi-frequency bioelectrical impedance spectroscopy applied in subjects with different body sizes, adiposity, and hydration status. It was a cross-sectional study with 386 non-chronic kidney disease volunteers (body mass index from 17 to 40 kg/m2), 30 patients in peritoneal dialysis, and 95 in hemodialysis. Bioelectrical impedance, body composition, and body water data were assessed with single- and multi-frequency bioelectrical impedance spectroscopy. Differences (95% confidence interval) and agreements (Bland-Atman analyze) between devices were evaluated. The intraclass correlation coefficient was used to measure the strength of agreement and Pearson’s correlation to measure the association. Regression analyze was performed to test the association between device difference with body mass index and overhydration. The limits of agreement between devices were very large. Fat mass showed the greatest difference and the lowest intraclass and Pearson’s correlation coefficients. Pearson’s correlation varied from moderate to strong and the intraclass correlation coefficient from weak to substantial. The difference between devices were greater as body mass index increased and was worse in the extremes of water imbalance. In conclusion, data obtained with single- and multi-frequency bioelectrical impedance spectroscopy were highly correlated with poor agreement; the devices cannot be used interchangeably and the agreement between the devices was worse as body mass index and fat mass increased and in the extremes of overhydration.

Lack of agreement of in vivo raw bioimpedance measurements obtained from two single and multi-frequency bioelectrical impedance devices.

It is important for highly active individuals to accurately assess their hydration level. Bioelectrical impedance (BIA) can potentially meet these needs but its validity in active individuals is not well established. We compared whole-body bioimpedance measurements obtained from multi-frequency bioelectrical impedance spectroscopy (BIS, Xitron 4200) at a 50 kHz frequency with those determined by a phase-sensitive single-frequency device (SF-BIA, BIA-101, RJL/Akern Systems) in two populations: active adults and elite athletes. One hundred twenty-six participants, including active males involved in recreational sports (N = 25, 20-39 yr) and elite athletes (females: N = 26, 18-35 yr; males: N = 75, 18-38 yr) participated in this study. Reactance (Xc), Resistance (R), Impedance (Z), and phase angle (PhA) were obtained by BIS and SF-BIA. Small but significant differences (R: -9.91 ± 15.09 Ω; Xc: -0.97 ± 2.56 Ω; Z: -9.96 ± 15.18 Ω; PhA: 0.12 ± 0.2°) were observed between the bioimpedance equipment in all measured variables (p < 0.05) though differences were within the devices' technical error of measurements. Device-specific values were highly (p < 0.0001) correlated [R2 ranged from 0.881 (Xc) to 0.833 (R)], but slopes and intercepts were different (p < 0.0001) from 1 and 0, respectively. Relatively large limits of agreement were observed for R (-40 to 21 Ω), Xc (-6 to 4 Ω), PhA (-0.4 to 0.5°), and impedance (-40 to 20 Ω). Bioimpedance measurements from the current single- and multi-frequency devices should not be used interchangeably. The of lack of agreement between devices was observed in determining individual values of R, Xc, Z and PhA of highly active populations possibly due to methodological and biological factors.

Wearable Multi-Frequency and Multi-Segment Bioelectrical Impedance Spectroscopy for Unobtrusively Tracking Body Fluid Shifts during Physical Activity in Real-Field Applications: A Preliminary Study.

Bioelectrical Impedance Spectroscopy (BIS) allows assessing the composition of body districts noninvasively and quickly, potentially providing important physiological/clinical information. However, neither portable commercial instruments nor more advanced wearable prototypes simultaneously satisfy the demanding needs of unobtrusively tracking body fluid shifts in different segments simultaneously, over a broad frequency range, for long periods and with high measurements rate. These needs are often required to evaluate exercise tests in sports or rehabilitation medicine, or to assess gravitational stresses in aerospace medicine. Therefore, the aim of this work is to present a new wearable prototype for monitoring multi-segment and multi-frequency BIS unobtrusively over long periods. Our prototype guarantees low weight, small size and low power consumption. An analog board with current-injecting and voltage-sensing electrodes across three body segments interfaces a digital board that generates square-wave current stimuli and computes impedance at 10 frequencies from 1 to 796 kHz. To evaluate the information derivable from our device, we monitored the BIS of three body segments in a volunteer before, during and after physical exercise and postural shift. We show that it can describe the dynamics of exercise-induced changes and the effect of a sit-to-stand maneuver in active and inactive muscular districts separately and simultaneously.

Validation of Bioelectrical Impedance Spectroscopy to Measure Total Body Water in Resistance-Trained Males

The three-compartment (3-C) model of physique assessment (fat mass, fat-free mass, water) incorporates total body water (TBW) whereas the two-compartment model (2-C) assumes a TBW of 73.72%. Deuterium dilution (D2O) is the reference method for measuring TBW but is expensive and time consuming. Multifrequency bioelectrical impedance spectroscopy (BIS SFB7) estimates TBW instantaneously and claims high precision. Our aim was to compare SFB7 with D2O for estimating TBW in resistance trained males (BMI >25kg/m2). We included TBWBIS estimates in a 3-C model and contrasted this and the 2-C model against the reference 3-C model using TBWD2O. TBW of 29 males (32.4 ± 8.5 years; 183.4 ± 7.2 cm; 92.5 ± 9.9 kg; 27.5 ± 2.6 kg/m2) was measured using SFB7 and D2O. Body density was measured by BODPOD, with body composition calculated using the Siri equation. TBWBIS values were consistent with TBWD2O (SEE = 2.65L; TE = 2.6L) as were %BF values from the 3-C model (BODPOD + TBWBIS) with the 3-C reference model (SEE = 2.20%; TE = 2.20%). For subjects with TBW more than 1% from the assumed 73.72% (n = 16), %BF from the 2-C model differed significantly from the reference 3-C model (Slope 0.6888; Intercept 5.093). The BIS SFB7 measured TBW accurately compared with D2O. The 2C model with an assumed TBW of 73.72% introduces error in the estimation of body composition. We recommend TBW should be measured, either via the traditional D2O method or when resources are limited, with BIS, so that body composition estimates are enhanced. The BIS can be accurately used in 3C equations to better predict TBW and BF% in resistance trained males compared with a 2C model.

Comparison of single- or multifrequency bioelectrical impedance analysis and spectroscopy for assessment of appendicular skeletal muscle in the elderly

Bioelectrical impedance analysis (BIA) is used to assess skeletal muscle mass, although its application in the elderly has not been fully established. Several BIA modalities are available: single-frequency BIA (SFBIA), multifrequency BIA (MFBIA), and bioelectrical impedance spectroscopy (BIS). The aim of this study was to examine the difference between SFBIA, MFBIA, and BIS for assessment of appendicular skeletal muscle strength in the elderly. A total of 405 elderly (74.2 ± 5.0 yr) individuals were recruited. Grip strength and isometric knee extension strength were measured. Segmental SFBIA, MFBIA, and BIS were measured for the arms and upper legs. Bioelectrical impedance indexes were calculated by squared segment length divided by impedance (L2/Z). Impedance at 5 and 50 kHz (Z5 and Z50) was used for SFBIA. Impedance of the intracellular component was calculated from MFBIA (Z250-5) and BIS (RICW). Correlation coefficients between knee extension strength and L2/Z5, L2/Z50, L2/RICW, and L2/Z250-5 of the upper legs were 0.661, 0.705, 0.790, and 0.808, respectively (P < 0.001). Correlation coefficients were significantly greater for MFBIA and BIS than SFBIA. Receiver operating characteristic curves showed that L2/Z250-5 and L2/RICW had significantly larger areas under the curve for the diagnosis of muscle weakness compared with L2/Z5 and L2/Z50. Very similar results were observed for grip strength. Our findings suggest that MFBIA and BIS are better methods than SFBIA for assessing skeletal muscle strength in the elderly.

Analysis of concordance between the bioelectrical impedance vector analysis and the bioelectrical impedance spectroscopy in haemodialysis patients.

The values of body composition provided by the two most commonly used bioelectrical impedance systems in Spain, single-frequency bioelectrical impedance vector analysis (SF-BIVA) and multi-frequency bioelectrical impedance spectroscopy (MF-BIS) are different and not comparable. Analyse whether the inter-method variability is due to bioelectrical variables measured by the different monitors, or rather due to the equations used to calculate body volume and mass. Another objective was to determine whether, despite the inter-method variability, the classification of hydration status by the two methods is consistent. Bioelectrical impedance was measured by SF-BIVA and MF-BIS immediately before a dialysis session in 54 patients on haemodialysis. In 38 patients, the study was repeated by SF-BIVA at the end of the same dialysis session. Resistance and phase angle values provided by the two monitors at a frequency of 50kHz were consistent. For resistance, variability was 1.3% and the intra-class correlation coefficient was 0.99. For phase angle, variability and the intra-class correlation coefficient were 11.5% and 0.92, respectively. The volume values for total body water, extracellular water, fat mass and body cell mass were biased, with a level of variability that would not be acceptable in clinical practice. The intra-class correlation coefficient also suggested a poor level of agreement. SF-BIVA systems define overhydration or dehydration as a vector below or above the tolerance ellipse of 75% on the longitudinal axis. MF-BIS uses two criteria for pre-dialysis hyper-hydration: overhydration (OH) greater than 2.5 litres, or greater than 15% of extracellular water. The degree of equivalence with the results of the SF-BIVA monitor was better with the second criterion (kappa: 0.81, excellent agreement) than with the first one (kappa: 0.71, acceptable agreement). The MF-BIS system defines post-dialysis normal hydration as a difference between OH and ultrafiltratation volume between –1.1 and 1.1 litres and agreement with the SF-BIVA system for this parameter was acceptable (weighted kappa index: 0.64). The MF-BIS and SF-BIVA systems provide similar readings for bioelectrical parameters, and the wide variation in the quantification of volume and body mass must be attributed to the different equations used for calculation. Furthermore, the criteria used by both systems to define both pre- and post-dialysis hydration have an acceptable level of equivalence.

The Effect of Racial Origin on Total Body Water Volume in Peritoneal Dialysis Patients

Peritoneal dialysis adequacy is typically assessed by urea clearance corrected for total body water (TBW) on the basis of anthropomorphic equations, which do not readily take into account changes in body composition, which may vary between ethnic groups. To determine whether ethnicity could affect estimates of peritoneal dialysis adequacy, we compared TBW estimated by anthropomorphic equations and that measured by multifrequency bioimpedance spectroscopy. We calculated TBW in 600 healthy adult peritoneal dialysis outpatient attending two tertiary university hospitals serving an inner-city multiethnic population who had TBW measured by multifrequency bioimpedance spectroscopy performed. 600 adult peritoneal dialysis patients were studied: mean age, 56.7 ± 0.6 years; 54.2% men; 29.7% diabetic; mean body mass index, 26.1 ± 0.2; 47.3% Caucasian; 29.2% South Asian; 12.8% African/Afro-Caribbean. Total body water was calculated using several anthropomorphic equations and was higher than that calculated MEASURED BY MF-BIS for all ethnic groups, apart from African/Afro-Caribbeans, with the greatest difference between Watson calculated TBW and multifrequency bioelectrical impedance spectroscopy 12.3 ± 0.6% for the South Asians, 9.0 ± 2.6% for Far Eastern Asians, 2.8 ± 0.6% Caucasians, and -0.2 ± 1.5% for African/Afro-Caribbeans. In this United Kingdom-based multiethnic population, body composition differed particularly for the South Asian patients compared with Caucasians and African/Afro-Caribbeans. Overestimation of TBW by anthropomorphic-based equations would lead to a lower calculation of Kt/V(urea), which may lead to changes in peritoneal dialysis prescription to achieve clinical standard targets and also affect studies examining the relationship between Kt/V and survival.

Factors Contributing to Formation of Edema in Volume Overloaded Continuous Ambulatory Peritoneal Dialysis Patients

Volume control is critical for the success of peritoneal dialysis (PD) but dry weight in PD has been difficult to obtain. Edema free is, in general, accepted clinically as a target for volume control in PD patients. However, PD patients can be free of edema despite significant volume overload. The present study investigates the possible factors that influence the formation of pitting edema in volume-overloaded PD patients. In this cross-sectional study, patients' fluid status was evaluated by multifrequency bioelectrical impedance spectroscopy analysis. Values for overhydration were obtained. Patients with overhydration ≥ 2.0 kg were considered volume overloaded and were eligible for inclusion. From 1 March 2009 to 1 December 2009, a total of 96 patients on continuous ambulatory PD were included. Endothelial function was evaluated by flow-mediated dilatation (FMD). Other clinical indicators, such as blood pressure, dialysis adequacy, nutrition status, and biochemical parameters, were recorded. Patients were divided into 2 groups based on edema status: the edema group (n = 35 volume-overloaded patients with bilateral pitting edema) and the non-edema group (n = 61 volume-overloaded patients without bilateral pitting edema). Overhydration in the edema group was significantly higher than in the non-edema group (4.28 ± 1.75 kg vs 3.12 ± 0.81 kg, p < 0.001), whereas both FMD and serum albumin in the edema group were significantly lower than in the non-edema group (6.65% ± 5.2% vs 10.3% ± 5.1%, p = 0.001; 37.6 ± 4.2 g/L vs 39.3 ± 3.5 g/L, p = 0.047, respectively). Edema status (edema = 1, non-edema = 0) was positively correlated with overhydration (r = 0.341, p < 0.001), gender (male = 1, female = 2: r = 0.184, p = 0.072), and total fluid removal (r = 0.188, p = 0.074) and negatively correlated with endothelial function, as assessed by FMD (r = -0.33, p = 0.001), and serum albumin (r = -0.18, p = 0.055). Logistic regression analysis showed that FMD [odds ratio (OR) 0.90, 95% confidence interval (CI) 0.81 - 0.99; p = 0.036], gender (male = 1, female = 2: OR 4.06, 95% CI 1.23 - 13.35; p = 0.021), overhydration (OR 3.06, 95% CI 1.53 - 6.13; p = 0.002), and serum albumin (OR 0.86, 95% CI 0.75 - 0.99; p = 0.035) were independent factors affecting the edema status of the study population. Our study showed that endothelial function (assessed by FMD), gender, serum albumin, and overhydration are independent determinants of edema status in PD patients. This may explain why some PD patients can maintain free of edema despite significant volume overload.

Skeletal Muscle Cell Volume In Lower Limb Might Be A Determinant Of Aerobic Work Capacity In Lean Young Women

PURPOSE: Skeletal muscle tissue holds a large amount of water, which is partitioned into intracellular water (ICW) and extracellular water (ECW, the sum of interstitial fluid and blood plasma) fractions. Thus, the muscle volume estimated using these imaging methods includes not only the muscle cell mass but also ECW, which is not related to muscle strength. In other words, a cellular approach is required to measure actual skeletal muscle cell mass. Recently, estimating the regional ICW and ECW became possible using segmental multifrequency bioelectrical impedance spectroscopy (S-BIS), and the ICW is proportional to the regional muscle cell mass. The present study examined the hypothesis that the muscle cell mass in the lower extremities might be related to aerobic work capacity in lean young women. METHODS: Thirteen Japanese female college students aged 20-26 years old (height, 161.3 ± 6.5 cm; weight, 53.63 ± 6.17 kg; BMI, 20.56 ± 1.64 kg/m2) were recruited. The ICW and ECW in the upper and lower extremities were measured by S-BIS. Incremental exercise test from 10 w to completely exhaustion was performed on electrically breaked cycle ergometer with metabolic cart to evaluate VO2peak. Lactate threshold (LT) were determined by lactate concentration of the blood obtained from earlap. Muscle strength and power in the lower extremities was measured. Daily physical activities were monitored by a previously validated triaxial accelerometer during two weeks. RESULTS: The ICW in the lower leg was significantly and highly correlated with the work and VO2 at LT, VO2peak, leg muscle strength and power, and the duration of moderate intensity physical activity, but not light or vigorous intensity physical activity. In contrast, the ICW in the upper extremities and the ECW in the upper and lower extremities were not significantly or just weakly correlated with those variables. CONCLUSIONS: The results suggest that the daily moderate intensity physical activity would be important to maintain muscle cell mass in the lower leg, and the muscle cell mass in the lower extremities might be a determinant of aerobic work capacity in lean young women.

Extracellular Water May Mask Actual Muscle Atrophy During Aging

Skeletal muscle tissue holds a large volume of water partitioned into extracellular water (ECW) and intracellular water (ICW) fractions. As the ECW may not be related to muscle strength directly, we hypothesized that excluding ECW from muscle volume would strengthen the correlation with muscle strength. A total of 119 healthy men aged 20-88 years old participated in this study. Knee isometric extension strength, vertical jump, and standing from a chair were measured as indices of muscle strength and power in the lower extremities. The regional lean volume (LV), total water (TW), ICW, and ECW in the lower leg were estimated by anthropometry (skinfold and circumference measurements) and segmental multifrequency bioelectrical impedance spectroscopy (S-BIS). Then, we calculated the ECW/TW and ICW/TW ratios. Although ICW and the LV index decreased significantly with age (p < .001), no significant changes in ECW were observed (p = .134). Consequently, the ECW/TW ratio increased significantly (p < .001) with age (young adult, 27.0 +/- 2.9%; elderly, 34.3 +/- 4.9%; advanced elderly, 37.2 +/- 7.0%). Adjusting for this by including the ICW/TW ratio in our models significantly improved the correlation between the LV index and strength-related measurements and correlated with strength-related measurements independently of the LV index (p < .001). The ECW/TW ratio increases in the lower leg with age. The results suggest that the expansion of ECW relative to ICW and the LV masked actual muscle cell atrophy with aging.

The Effects of Betaine Supplementation on Strength and Power Performance

Betaine (B) is an organic osmolyte and methyl donor. Organic osmolytes are important for fluid balance during osmotic stress and metabolic methylation reactions. Both are important during resistance exercise given the flux of substrates through metabolic pathways and may benefit strength and power performance. PURPOSE: To determine the efficacy of B supplementation in improving strength and power performance. METHODS: Twelve men (mean ± SD age, 21 ± 3 yr; mass, 79.1 ± 10.7 kg) with a minimum of 3 months resistance training, including the squat exercise, completed two 14-day trials in a balanced, randomized, double-blind, repeated measures, crossover design. Prior to and following 14 days of B supplementation (1.25 g mixed in 240 ml Gatorade®) or placebo (P), consumed twice per day, subjects completed two consecutive days (D1 and D2) of a standardized high intensity/power resistance exercise challenge (REC). A 14-day washout period separated the 14-day B and P trials. Two standardized resistance training workouts were completed during B and P trials, and during the washout period, to maintain the subject's training status. Total body water was measured via multi-frequency bio-electrical impedance spectroscopy. ANOVA were conducted with alpha set at 0.05. RESULTS: Body mass and total body water values did not change over the course of the study. Following 14-days of B supplementation, bench throw power (1779 ± 90 W) and isometric bench press force (2922 ± 297 N) increased (p<0.05) during REC compared to pre-supplementation values and corresponding P values (1535 ± 81 W, 2345 ± 146 N, respectively). Compared to pre-supplementation, vertical jump power and isometric squat force increased (p<0.05) on both D1 and D2. There were no differences in bench press repetitions, number of squat repetitions, and jump squat power between D1 and D2, or between B and P values. CONCLUSION: B supplementation increased power, force and maintenance, particularly in the smaller upper-body muscle groups compared to larger lower-body muscle groups. Funded by Danisco USA Incorporated, Ardsley, NY.

Bioimpedance electrical spectroscopy in the first six months of life: some methodologic considerations

Objectives The objectives of this study were to evaluate the feasibility of using multifrequency bioelectrical impedance spectroscopy (BIS) in newborns and first-semester infants and to assess the influence of diverse methodologic and biological factors on BIS measurements. Methods We studied 69 infants of both sexes, from the first day after birth through age 6 mo. They were healthy term infants who had no congenital malformations and were born in a low-income, peri-urban neighborhood of Guatemala City. The design was based on serial, repeated BIS measurements. Results Overall mean values of extra- and intracellular resistance (mean ± standard deviation) were 470.0 ± 73.3 Ω and 604.6 ± 179.2 Ω, respectively. We found statistical differences in both resistances in relation to advancing age and degree of movement while taking the measurements. With respect to repeat measurements by two separate observers, interobserver differences were a non-significant 7.6 Ω for both resistances. Restraining the infants and previous consumption of milk or formula had a significant effect on extracellular resistance measurements. The mean standard errors of measurement was 4.5 Ω for extracellular resistance and 73.9 Ω for intracellular resistance. Conclusion The BIS technique is feasible in newborn and young children when physiologic and methodologic aspects are respected or controlled.

The effect of dehydration on wrestling minimum weight assessment.

Given that some wrestlers arrive for minimum weight (MW) testing in a dehydrated condition, it is important to understand the effects of dehydration on MW assessment methods. To determine the effect of dehydration on the assessment of MW by three-site skinfolds with the Lohman formula (SF), leg-to-leg bioelectrical impedance analysis (BIA), and multifrequency bioelectrical impedance spectroscopy (BIS) compared with a four-component (4C) criterion. Twenty-two male collegiate wrestlers (mean +/- SD, age: 19.9 +/- 1.4 yr, height: 174.0 +/- 6.8 cm, body mass: 77.4 +/- 9.1 kg) had their body composition assessed by the 4C criterion, hydrostatic weighing (HW), SF, BIA, and BIS in euhydration (EUH) and dehydration (DEH). Subjects dehydrated 2-5% of body weight through fluid restriction and exercise in a hot environment. In EUH, the total error (TE) for HW (1.75 kg) and SF (2.15 kg) were not significantly different, but the TE for HW and SF methods were significantly lower than the TE for both BIS (3.68 kg) and BIA (3.77 kg). In DEH, SF, BIA, and BIS methods had a TE approaching or exceeding 4 kg (8.8 lb). Dehydration increased the TE for SF and BIA through an artificial lowering of body weight and for BIS by an increased error in intracellular water prediction. Acute thermal dehydration violates assumptions necessary for the accurate and precise prediction of MW by SF, leg-to-leg BIA, and multifrequency BIS.

Body composition, as assessed by bioelectrical impedance spectroscopy and dual‐energy X‐ray absorptiometry, in a healthy paediatric population

The aim of this study was to determine the level of agreement between body composition measurements by dual‐energy X‐ray absorptiometry (DXA), single‐frequency bioelectrical impedance analysis (BIA) and multifrequency bioelectrical impedance spectroscopy (BIS). Fat‐free mass (FFM), body fat mass and body fatness (percentage fat) were measured by DXA, BIA and BIS in 61 healthy children (37M, 24F, aged 10.9–13.9 y). Estimates of FFM, body fat mass and body fatness were highly correlated (r= 0.73–0.96, p &gt; 0.0001) between the different methods. However, a Bland‐Altman comparison showed wide limits of agreement between the methods. The mean differences between methods for FFM ranged from 2.31 ± 7.76 kg to 0.48 ± 7.58 kg. Mean differences for body fat mass ranged from 0.16 ± 5.06 kg to 2.95 ± 5.65 kg and for body fatness from 2.3 ± 7.8% to 0.8 ± 9.3%. Calculations of body composition with BIS were not superior to BIA. However, BIA overestimated fat mass in lean subjects and underestimated fat mass in overweight subjects more than BIS, compared with DXA. Conclusion: The methods used provided estimates of FFM, body fat mass and body fatness that were highly correlated in a population of healthy children. However, the large limits of agreement derived from the Bland‐Altman procedure suggest that the methods should not be used interchangeably.

Assessment of body fluid compartment volumes by multifrequency bioelectrical impedance spectroscopy in children with dengue

Dengue haemorrhagic fever (DHF), the most severe form of illness following infection with a dengue virus, is characterized by plasma leakage and a period of increased microvascular permeability. Monitoring of plasma volume and body fluid compartment shifts is an integral part of the clinical management of DHF, and is crucial to the performance of clinical research studies on DHF pathogenesis. Multifrequency bioelectrical impedance spectroscopy (BIS) was assessed as a non-invasive method to monitor body fluid compartment shifts in children participating in a prospective, hospital-based, study of dengue virus infections in Thailand. Over the 48 h surrounding defervescence, the extracellular water/intracellular water ratio (ECW/ICW) rose in children with dengue virus infections and correlated with increasing disease severity [DHF > intermediate dengue fever (DF)/DHF>DF]. Plasma leakage remained within the ECW compartment and was not directly measured by multifrequency BIS. Expansion of the ECW space in DHF appeared to be primarily due to diminished renal water clearance. During the course of dengue illness, multifrequency BIS did not improve on serial haematocrit and bodyweight determinations for monitoring plasma volume contraction and ECW expansion, respectively.