Multifrequency Bioimpedance Analysis Research Articles

Bioimpedance analysis for identifying new indicators of exercise-induced muscle damage

A noninvasive, immediate, and convenient method for assessing muscle tissue status during exercise-induced muscle damage (EIMD) has not been established. This study was designed to assess and determine parameters suitable for measuring EIMD after eccentric exercise, using multi-frequency bioimpedance analysis (BIA). Thirty-five young male participants performed dumbbell exercises with their left arm, and their BIA parameters were measured at various time points up to 168 h post exercise using a multi-frequency BIA device. At all-time points, intra and extracellular water content was greater in the left arm than in the right arm, whereas the impedance, reactance, resistance, and phase angle were lower in the left arm than in the right arm. Established EIMD indices, such as maximal isometric voluntary contraction, were measured and used in correlational analyses. Only reactance was correlated with biomarkers, indicating muscle damage (r = − 0.56 to − 0.49). Furthermore, reactance was found to correlate well with indirect indicators of EIMD, suggesting that it may be a suitable marker for evaluating EIMD. However, the relationship with the limited evaluation indices employed in this study is constrained. Future studies should investigate the correlation between reactance and direct damage indicators, such as structural damage, observed in biopsies.

Differences in anthropometric and vertical jump force-time characteristics between U16 and U18 female basketball players.

Considering the importance of body composition and lower-body strength and power for basketball players' on-court performance, as well as a lack of sports science research focused on female athletes, the purpose of the present investigation was to record the anthropometric and countermovement vertical jump (CMJ) characteristics of top-tier U16 and U18 female basketball players and examine between-group differences in the aforementioned tests. Thirty-two athletes who were a part of the national basketball academy volunteered to participate in the present investigation. Following the body composition assessment conducted via a segmental multifrequency bioimpedance analyzer, athletes performed three CMJs while standing on a force plate system sampling at 1000 Hz. Independent t-test and Mann-Whitney U-test were used to examine between-group differences. The findings reveal significant differences in body composition and lower-body neuromuscular performance characteristics between female basketball players ages 16 and 18. Although no differences were observed in muscle and body fat percentages, the U18 group had significantly greater height, overall body mass (both muscle and fat mass), as well as greater segmental fat-free mass (trunk, both legs and arms), intracellular and extracellular water, and body mass index when compared to their U16 counterparts. On the other hand, the U18 group demonstrated longer eccentric, concentric, and braking phase duration, as well as overall contraction time when compared to the U16 players. In addition, the U18 athletes exhibited higher eccentric mean force and power, concentric impulse, peak power, and mean and peak force.

Lower-body muscular power predicts performance on urban combat simulation.

Military operations in urban environments requires faster movements and therefore may place greater demands on soldier strength and anaerobic ability. The aim was to study how physical fitness and body composition are associated with occupational test for urban combat soldiers before and after a 5-day military field exercise (MFE). Twenty-six conscripts (age = 20±1 yrs.) volunteered, of which thirteen completed the study. Occupational performance was determined by using the newly developed Urban Combat Simulation test (UCS); which included 50-m sprinting, moving a truck tire (56 kg) 2 meters with a sledgehammer, a 12-m kettlebell carry (2×20 kg) up the stairs with a 3-m ascent, 4-time sandbag lifts (20 kg) with obstacle crossing, and a 20-m mannequin (85 kg) drag. Aerobic and muscle fitness, as well as anaerobic capacity were measured, and, body composition was assessed with multifrequency bioimpedance analysis. The UCS performance correlated significantly with standing long jump performance, as well as lower and upper body maximal strength before (r = -0.56 to -0.66) and after (r = -0.59 to -0.68) MFE, and, with body mass and FFM before (r = -0.81 to -0.83) and after (r = -0.86 to -0.91) MFE. In the regression analyses, fat free mass (R2 = 0.50, p = 0.01) and counter movement jump in combat load (R2 = 0.46, p = 0.009) most strongly explained the UCS performance. This study demonstrated that muscle mass and lower body explosive force production together with maximal strength are key fitness components related to typical urban combat soldiers' military tasks. Physical training developing these components are recommended.

DETERMINING THE ACCURACY OF THE SMART BRACE USING MULTI-FREQUENCY BIOIMPEDANCE ANALYSIS TO MEASURE KNEE SWELLING

Knee swelling is common after injury or surgery, resulting in pain, restricted range of movement and limited mobility. Accurately measuring knee swelling is critical to assess recovery. However, current measurement methods are either unreliable or expensive [1,2]. Therefore, a new measurement method is developed. This wearable (the ‘smart brace’) has shown the ability to distinguish a swollen knee from a not swollen knee using multi-frequency-bio impedance analysis (MF-BIA) [3].This study aimed to determine the accuracy of this smart brace. The study involved 25 usable measurements on patients treated for unilateral knee osteoartritis with a 5mL injection of Lidocaïne + DepoMedrol (1:4). MF-BIA measurements were taken before and after the injection, both on the treated and untreated knee. The smart brace accurately measured the effect of the injection by a decrease in resistance of up to 2.6% at 100kHz (p<0.01), where commonly used gel electrodes were unable to measure the relative difference. Remarkably, both the smart brace and gel electrodes showed a time component in the MF-BIA measurements.To further investigate this time component, 10 participants were asked to lie down for 30 minutes, with measurements taken every 3 minutes using both gel electrodes and the smart brace on both legs. The relative change between each time step was calculated to determine changes over time. The results showed presence of a physiological aspect (settling of knee fluids), and for the brace also a mechanical aspect (skin-electrode interface) [4]. The mechanical aspect mainly interfered with reactance values.Overall, the smart brace is a feasible method for quantitatively measuring knee swelling as a relative change over time. However, the skin-electrode interface should be improved for reliable measurements at different moments in time. The findings suggest that the smart brace could be a promising tool for monitoring knee swelling during rehabilitation.

Body composition analysis via spatially resolved NIR spectroscopy with multifrequency bioimpedance precision.

Near-infrared spectroscopy (NIRS) is often criticized due to its insufficient accuracy in determining body composition compared to the gold standard methods. In this work, we show that the use of multiple source-detector distances, as well as the simultaneous use of physiological and optical features, can significantly improve the accuracy of determination of fat and lean mass percentage in the human body using NIR spectroscopy. The study performed on the n = 292 cohort revealed the mean absolute errors of 3.5% for fat content and 3.3% for soft lean mass percentage prediction (r = 0.93) using the multifrequency bioimpedance analysis (BIA) as a reference. Hence, NIRS can serve as an independent reliable method for body composition analysis with precision close to that of advanced multifrequency BIA.

Phase Angle as a Risk Factor for Mortality in Patients Undergoing Peritoneal Dialysis

Phase angle (PhA) is measured using bioimpedance analysis and calculated using body reactance and resistance in the waveform at 50 kHz. Further studies are necessary to clarify the predictive efficacy of PhA in the mortality of peritoneal dialysis (PD) patients. The objective of this study was to assess the utility of PhA for predicting patient mortality and technique failure and compare the predictability of PhA with other risk factors. Our study had a retrospective cohort design. Our center routinely evaluates bioimpedance measurements for all prevalent PD patients (n = 199). The PhA was measured using multifrequency bioimpedance analysis. Our study evaluated patient and technique survival. There were 66, 68, and 65 patients in the low, middle, and high tertiles of PhA, respectively. The PhA values of the low, middle, and high tertiles were 3.6° (3.4–3.9), 4.4° (4.2–4.7), and 5.5° (5.2–6.0), respectively. The 5-year patient survival rates for the high, middle, and low tertiles were 100%, 81.7%, 69.9%, respectively (p < 0.001). The 5 year technique survival rates for the high, middle, and low tertiles were 91.9%, 74.8%, 63.7%, respectively (p = 0.004). Patient and technique survival increased as the PhA tertiles increased. Both univariate and multivariate Cox regression analyses demonstrated a consistent pattern. The prediction of patient or technique survival was better in PhA than in the other classical indicators. The present study demonstrated that PhA may be an effective indicator for predicting patient or technique survival in PD patients. Furthermore, it suggests that routine measurement of PhA and pre-emptive intervention to recover PhA according to causes of low PhA may help improve patient or technique survival in PD patients.

A Pilot Study Examining the Dielectric Response of Human Forearm Tissues.

This work aims to describe the dielectric behaviors of four main tissues in the human forearm using mathematical modelling, including fat, muscle, blood and bone. Multi-frequency bioimpedance analysis (MF-BIA) was initially performed using the finite element method (FEM) with a 3D forearm model to estimate impedance spectra from 10 kHz to 1 MHz, followed by a pilot study involving two healthy subjects to characterize the response of actual forearm tissues from 1 kHz to 349 kHz. Both the simulation and experimental results were fitted to a single-dispersion Cole model (SDCM) and a multi-dispersion Cole model (MDCM) to determine the Cole parameters for each tissue. Cole-type responses of both simulated and actual human forearms were observed. A paired t-test based on the root mean squared error (RMSE) values indicated that both Cole models performed comparably in fitting both simulated and measured bioimpedance data. However, MDCM exhibited higher accuracy, with a correlation coefficient (R2) of 0.99 and 0.89, RMSE of 0.22 Ω and 0.56 Ω, mean difference (mean ± standard deviation) of 0.00 ± 0.23 Ω and -0.28 ± 0.23 Ω, and mean absolute error (MAE) of 0.0007 Ω and 0.2789 Ω for the real part and imaginary part of impedance, respectively. Determining the electrical response of multi-tissues can be helpful in developing physiological monitoring of an organ or a section of the human body through MF-BIA and hemodynamic monitoring by filtering out the impedance contributions from the surrounding tissues to blood-flow-induced impedance variations.

Reference values for body composition in healthy urban Mexican children and adolescents.

Given the increasing incidence of chronic degenerative diseases related to changes in tissues, the availability of diagnostic tools with greater accuracy in the estimation of body composition (BC) has become necessary. Interpreting the BC values of individuals requires reference data obtained from a healthy population with the same ethnicity, to identify individuals at risk for the development of negative health outcomes. Generate reference values (RV) of body composition (BC) for Mexican children and adolescents. This was an urban-population-based cross-sectional study of healthy Mexican children and adolescents. BC estimations by anthropometry, multifrequency bioimpedance analysis (MF-BIA) and dual-energy X-ray absorptiometry (DXA) where used to create sex- and age-specific RV by means of generalized additive models for location, scale and shape (GAMLSS). We assessed 2104 subjects, and after confirming a clinically and metabolically healthy status, we measured 1659 subjects aged 5-20 years, [806 females (49%) and 853 males (51%)] by anthropometry, MF-BIA and DXA to create sex- and age- smoothed reference centiles, lambda (L), mu (M), and sigma (S) values. We also built sex- and age-smoothed graphic curves for each variable of interest. We present valid RV and curves for BC variables estimated by anthropometry, MF-BIA and DXA from clinically and metabolically healthy urban Mexican children and adolescents. These RV are different from those reported for other populations, and therefore, should be used for clinical and research purposes involving urban Mexican children and adolescents.

Phase angle is associated with sarcopenic obesity in post-stroke patients

Evidence is limited concerning the association between bioimpedance analysis-derived phase angle and sarcopenic obesity. This study examined this association in patients who underwent convalescent rehabilitation after stroke. This cross-sectional study included hospitalized patients with post-acute stroke. The phase angle was measured using a multifrequency bioimpedance analysis. Sarcopenic obesity was diagnosed according to the European Society of Clinical Nutrition and Metabolism/European Association for the Study of Obesity criteria. A multiple linear regression analysis was used to examine the association between the phase angle and sarcopenic obesity after adjusting for confounding factors. A receiver operating characteristic curve was used to calculate the optimal phase angle cutoff value for predicting sarcopenic obesity. A total of 760 patients (median age 71 years; 352 women) were analyzed. The median (interquartile range, 25th and 75th percentiles) phase angle was 4.45° (4.10°, 4.88°). Sarcopenic obesity was diagnosed in 16 (3.9%) men, 18 (5.1%) women, and 34 (4.5%) patients overall. The multiple linear regression analysis showed that sarcopenic obesity (β=-0.185, p=0.017) and sarcopenia (β=-0.121, p=0.012) were significantly and negatively associated with the phase angle. Obesity was not significantly associated with the phase angle (β=-0.078, p=0.094). The optimal cutoff value of the phase angle for diagnosing sarcopenic obesity was 4.29° (sensitivity 0.65, specificity 0.80, area under the curve [AUC] 0.79, 95% CI 0.77-0.87, p<0.001) in men and 3.84° (sensitivity 0.67, specificity 0.84, AUC 0.81, 95% CI 0.79-0.86, p<0.001) in women. The phase angle was associated with sarcopenic obesity, and the cutoff values of the phase angle that could predict sarcopenic obesity were 4.29° for men and 3.84° for women. This simple and practical phase angle-based prediction of sarcopenic obesity can be useful in clinical practice.

Reduced body cell mass and functions in lower extremities are associated with mild cognitive impairment and Alzheimer’s dementia

This study examined the alterations of segmental body composition in individuals with Alzheimer’s pathology (AD), including mild cognitive impairment (MCI) and dementia. A multifrequency bioimpedance analysis (BIA) was used to provide segmental water and impedance variables from 365 cognitively normal (CN), 123 MCI due to AD, and 30 AD dementia participants. We compared the BIA variables between the three groups, examined their correlations with neuropsychological screening test scores, and illustrate their 95% confidence RXc graphs. AD dementia participants were older, more depressive, and had worse cognitive abilities than MCI due to AD and CN participants. Although the BIA variables showed weak partial correlations with the cognitive test scores, we found patterns of an increasing water content in lean mass, increasing extra to intracellular water ratio, and decreasing reactance and phase angle in the lower extremities with effect sizes ranging from 0.26 to 0.51 in the groups of MCI and dementia due to AD compared with CN individuals. The RXc graphs upheld the findings with a significant displacement downward and toward the right, dominantly in the lower extremities. Individuals with AD pathology exhibit a reduced body cell mass or cell strength, an abnormal cellular water distribution, and an overhydration status in lean mass, especially in the lower extremities.

Evaluation of a Rapid Four-Compartment Model and Stand-Alone Methods in Hispanic Adults

BackgroundA rapid 4-compartment (4C) model integrates dual-energy x-ray absorptiometry (DXA) and multi-frequency bioimpedance analysis (MFBIA), which may be useful for clinical and research settings seeking to employ a multi-compartment model. ObjectivesThis study aimed to determine the added benefit of a rapid 4C model over stand-alone DXA and MFBIA when estimating body composition. MethodsOne hundred and thirty participants (n = 60 male; n = 70 female) of Hispanic descent were included in the present analysis. A criterion 4C model that employed air displacement plethysmography (body volume), deuterium oxide (total body water), and DXA (bone mineral) was used to measure fat mass (FM), fat-free mass (FFM), and body fat percent (%BF). A rapid 4C model (DXA-derived body volume and bone mineral; MFBIA-derived total body water) and stand-alone DXA (GE Lunar Prodigy) and MFBIA (InBody 570) assessments were compared against the criterion 4C model. ResultsLin’s concordance correlation coefficient values were >0.90 for all comparisons. The standard error of the estimates ranged from 1.3 to 2.0 kg, 1.6 to 2.2 kg, and 2.1 to 2.7% for FM, FFM, and %BF, respectively. The 95% limits of agreement ranged from ±3.0 to 4.2 kg, ±3.1 to 4.2 kg, and ±4.9 to 5.2% for FM, FFM, and %BF, respectively. ConclusionsResults revealed that all 3 methods provided acceptable body composition results. The MFBIA device used in the current study may be a more economically friendly option than DXA or when there is a need to minimize radiation exposure. Nonetheless, clinics and laboratories that already have a DXA device in place or that value having the lowest individual error when conducting a test may consider continuing to use the machine. Lastly, a rapid 4C model may be useful for assessing body composition measures observed in the current study and those provided by a multi-compartment model (e.g., protein).

Ultrasonography of the multifidus muscle in student circus artists with and without low back pain: a cross-sectional study

BackgroundDegenerative structural changes and functional deficits of the lumbar multifidus (LM) muscle were observed in athletes with low back pain. While spinal injuries are common in circus artists, there is no information on LM characteristics in this population. The aims of this study were to investigate LM morphology and function and explore the relationship between LM characteristics and low back pain in male and female circus artists.Methods31 college circus students were recruited. Participants completed an online survey to acquire demographic data and low back pain history. Body composition was measured using multi-frequency bio-impedance analysis. Ultrasound examinations at the fifth lumbar vertebrae in prone and standing positions were performed to assess LM cross-sectional area, echo-intensity, thickness. Independent and dependent t-test assessed the difference between sex and side, respectively. The relationships between measures were assessed with Pearson’s correlations. The LM characteristics’ difference between artists with and without low back pain (group binary variable) was assessed with Analysis of covariance using lean body mass, height and % body fat as continuous covariates.ResultsMales had significantly larger LM cross-sectional area, lower echo-intensity and greater thickness change from rest to contracted than females. LM cross-sectional area asymmetry in prone was greater in artists reporting low back pain in the previous 4-weeks (p = 0.029) and 3-months (p = 0.009). LM measures were correlated with lean body mass, height, and weight (r = 0.40–0.77, p ≤ 0.05).ConclusionThis study provided novel insights into LM characteristics in circus artists. Greater LM asymmetry was observed in artists with a history of low back pain. In accordance with previous studies in athletes, LM morphology and function were highly correlated with body composition measurements.

A Simple Estimate of Visceral Fat Area by Multifrequency Bioimpedance Analysis Is Associated with Multiple Biomarkers of Inflammation and Cardiometabolic Disease: A Pilot Study

There is a need for identifying whether simple techniques for estimating visceral fat can accurately predict inflammatory and cardiometabolic disease (CMD) biomarkers in various populations. We aimed to determine whether a simple estimate of visceral fat area by multifrequency bioelectrical impedance analysis (MFBIA) was independently associated with multiple biomarkers of inflammation and CMD. Seventy-eight men and women (mean ± SD: age 52.0 ± 10.8 y; visceral fat area 105.6 ± 55.0 cm2) self-reported their medical histories and activity levels. Visceral fat area was estimated with MFBIA, CMD and inflammatory biomarkers were measured by fasting blood draw, and homeostasis model assessment for insulin resistance (HOMA-IR) was calculated. Associations were assessed using multivariable linear regression. With adjustment for age, sex, height, race/ethnicity, family history of diabetes, and smoking, a 1-standard deviation (1-SD) increase in visceral fat (55 cm2) was associated with higher levels of insulin (60.4%), triglycerides (43.6%), C-reactive protein (38.7%), interleukin-6 (33.9%), leptin (77.9%), and HOMA-IR (51.8%, p &lt; 0.01 for all). These associations were attenuated but remained significant when physical activity and sedentary behavior were entered into the model (p ≤ 0.01). These findings suggest that a simple estimate of visceral fat area by MFBIA may be a good indicator of increased CMD risk and may be useful in clinical practice.

Changes in Segmental Impedances and Selected Body Composition Parameters Assessed by Multi-Frequency Bioimpedance Analysis after Fluid Consumption in Healthy Young Population.

Objectives: Body composition (BC) analysis is a routine part of comprehensive public health care. Assessment of BC is more important source of information than BMI. Adherence to the standard measurement conditions is essential for the correct results. Our study aimed to examine the effect of acute fluid consumption on measures of body mass (BM), percentage of body fat (%BF), visceral fat (VF), percentage of body water (%BW), and impedance at 100 kHz (I100) and 20 kHz (I20) using segmental multi-frequency bioelectrical impedance analysis (SMF-BIA) in a general healthy population. Methods: 95 consecutive healthy normal-weight adults (42 men; 53 women) were involved in the study (mean ± s.d.; age 23.9±1.6 years; body mass 68.3±14.1 kg). All subjects underwent two separate series of body composition (BC) measurements at 0 (BASELINE), 30, 60, 90 min (POST): the first series after drinking 600 ml of isotonic carbohydrate/electrolyte drink (IST) and the second after no fluid administration (CON). Individual measurements were performed in the morning on two consecutive days. Results: In the IST group, BM, VF (both P<0.001), and %BF (P<0.05) increased significantly at 30 min POST compared to BASELINE. BM and VF remained elevated at 90 min POST (both P<0.001). %BW decreased significantly at 30 min POST (P<0.01) then increased at 60 min (P<0.001) and 90 min (P<0.01) POST. There were no significant changes in I100. I20 increased significantly at 30 min POST (P<0.001) then decreased at 60 min (P<0.001) and 90 min POST (P<0.01) compared to BASELINE. In the CON group, BM and VF decreased below BASELINE at 90 min POST (P<0.001), %BF, %BW and I100 did not change significantly. The difference between IST and CON was statistically significant for all POST measurement times only in BM and VF (both P<0.001). The VF results are also underlined by the detected impedance changes in the trunk area at 20 kHz (B20) and 100 kHz (B100) at 60 min and 90 min (both P<0.001). Conclusions: Our study suggests that segmental impedances and BC measurement in healthy young normal-weight adults requires strict adherence to fluid restriction at least 90 min before the measurement to avoid false impedance values and overestimation of BM and VF.

Whole-body phase angle correlates with pre-operative markers in total joint arthroplasty.

Bioimpedance derived whole body phase angle (ϕ), a measure of cellular integrity, has been identified as an independent marker of morbidity and mortality in many medical and surgical specialties. While similar measures of water homeostasis like extracellular edema (EE) have been associated with pre-operative risk, ϕ has not been studied in orthopaedics, despite potential to serve as a pre-operative marker. This study aims to identify relationships between ϕ, EE, and body composition metrics, laboratory values, patient reported outcomes, and comorbidities. Multi-frequency bioimpedance analysis (BIA) records, laboratory values, and patient reported outcomes of adult patients presenting to an academic arthroplasty clinic were retrospectively reviewed. Correlation coefficients between ϕ, EE, and reviewed information were conducted. ϕ was significantly correlated (p<0.001) most positively with measures of lean tissue such as skeletal muscle mass (r=0.48), appendicular skeletal muscle index (r=0.39), lean body mass (r=0.43), and dry lean mass (r=0.47), while it held negative correlations (p<0.001) with age (r= -0.55), and body fat mass (r= -0.11). ϕ was not correlated with body mass index (BMI, p = 0.204). In contrast, EE demonstrated its strongest positive correlations (p<0.001) with body fat mass (r=0.32), age (r=0.50), and BMI (r=0.26), and its strongest negative correlations (p<0.001) with serum albumin (r= -0.37) and total protein (r= -0.23). Based on their associations with markers of health and fitness, BIA determined ϕ and EE demonstrate relationships to markers currently implemented in orthopaedic practice. This likely indicates that ϕ has potential as a comprehensive surrogate for several commonly used markers to quantify pre-operative risk. In the future, ϕ may aid in developing risk-stratifications for intervention and prevention of complications.

Impact of volume status on sarcopenia in non-dialysis chronic kidney disease patients

There were few data regarding the association of volume status with sarcopenia using muscle mass, strength, and physical performance in non-dialysis chronic kidney disease (ND-CKD) patients. We aimed to evaluate the association between volume status and sarcopenia in ND-CKD patients. Our retrospective study analyzed data from a previous study which included ND-CKD patients who had stable renal function. Our study used its baseline data alone. The edema index and muscle mass were measured using a multi-frequency bioimpedance analysis machine. The edema index was calculated using extracellular water/total body water ratio. The skeletal muscle index (SMI, kg/m2) was calculated using appendicular muscle mass per height squared. Handgrip strength (HGS, kg) was measured during the standing position in all patients. Dynamic gait speed (GS, m/s) was evaluated using 6-m walking speed. Patients with both low muscle mass (SMI < 7.0 kg/m2 for men and < 5.7 kg/m2 for women using bioimpedance analysis) and low HGS (< 28 kg for men and < 18 kg for women) or low GS (< 1.0 m/s) were classified as having sarcopenia. The patients (n = 147) were divided into tertiles based on the edema index level. The mean edema index in the low, middle, and high tertiles was 0.377 ± 0.006, 0.390 ± 0.003, and 0.402 ± 0.006, respectively. The edema index was significantly correlated with SMI, HGS, and GS (r = − 0.343 for SMI, − 0.492 for HGS, and − 0.331 for GS; P < 0.001 for three indicators). The SMI, HGS, and GS values were 8.1 ± 1.0 kg/m2, 33.0 ± 9.4 kg, and 1.2 ± 0.2 m/s in the low tertile,7.8 ± 1.2 kg/m2, 30.0 ± 7.5 kg, and 1.0 ± 0.3 m/s in the middle tertile, and 7.2 ± 1.4 kg/m2, 23.7 ± 7.4 kg, and 1.0 ± 0.3 m/s in the high tertile, respectively. Univariate analyses revealed that SMI was lower in patients in the high tertile than in those in the low tertile. HGS was lowest in high tertile, and GS was greatest in the low tertile. The high tertile for predicting sarcopenia had an odds ratio of 6.03 (95% CI, 1.78–20.37; P = 0.004) compared to low or middle tertiles. The results of multivariate analyses were similar to those of the univariate analyses. The subgroup analyses showed that statistical significance was greater in < 65 years and men than ≥ 65 years and women. The present study showed that the edema index is inversely associated with sarcopenia, muscle mass index, strength, and physical performance in ND-CKD patients. However, considering the limitations of our study such as its small sample size, this association was not strong. Further studies that include volume-independent measurements, data on physical activity and diet, and a larger number of patients are warranted to overcome these limitations.

Smartwatch-based bioimpedance analysis for body composition estimation: Precision and agreement with a 4-compartment model.

Given that the prevalence of smartwatches has allowed them to become a hallmark in health monitoring, this technology is primed to provide accessible body composition estimations. The purpose of this study was to evaluate the precision and agreement of smartwatch-based bioimpedance analysis and multifrequency bioimpedance analysis to a 4-compartment model criterion. A total of 186 participants (114 F) underwent body composition assessments necessary for a 4-compartment model and smartwatch and multifrequency bioimpedance analysis. Total body water from each device were also compared to bioimpedance spectroscopy. Precision was adequate though slightly lower for the smartwatch compared to other methods. No device demonstrated equivalence with the 4-compartment model. Specifically, the smartwatch overestimated and multifrequency underestimated body fat. Multifrequency bioimpedance analysis, but not smartwatch bioimpedance analysis, demonstrated equivalence for total body water. Overall error was higher for males using the smartwatch compared to females. While these findings do not invalidate the use of smartwatch-based estimates, clinicians should consider that there may be large errors relative to clinical measures. If this wearable device is intended to be used to monitor body composition change over time, these findings demonstrate the need for future research to evaluate its accuracy during follow-up testing.

Segmental bioelectrical impedance analysis for Korean older population with cold pattern.

This study examined the association of whole-body composition and segmental bioimpedance variables with cold pattern (CP) in different sexes. We assigned 667 older individuals to a CP group (n = 488) and a non-CP group (n = 179) by using an eight-item self-administered questionnaire. Seven body composition variables and three pairs of segmental bioimpedance variables for the upper and lower extremities, which were obtained from a segmental multifrequency bioimpedance analyzer, were employed to investigate their association with CP. Participants' characteristics were first described. Then we compared the selected body composition and bioimpedance variables between the CP and non-CP groups. Finally, their association with CP was investigated using univariate and multivariate regression analyses. All analyses were performed separately for women and men. Both women and men exhibited a comparable mean age in the CP and non-CP groups; however, women with CP had significantly lower blood pressures, whereas men with CP showed a higher proportion of osteoarthritis than those without CP. Compared with the non-CP group, individuals with CP exhibited significantly smaller body sizes indicated by shorter height and smaller weight, lower body mass index, and smaller volume-to-body surface area ratio in both sexes. After controlling for age, height, weight, and other covariates, we found significant reductions in body lean mass such as fat-free mass and body cell mass, basal metabolic rate per unit mass, total body water, and intra-to-extracellular water ratio in the CP group. With regard to segmental bioimpedance analysis, the resistance ratios and phase angles in the upper and lower extremities yield significant associations with CP incidence, as demonstrated by the odds ratio (95% confidence interval) of 1.72 (1.16-2.57), 1.69 (1.18-2.48), 0.60 (0.40-0.89), and 0.57 (0.39-0.82), respectively. However, these results did not emerge in men. Abnormal cellular water distribution and deterioration in body cell mass and/or cell strength are associated with CP prevalence, regardless of age, height, weight. These findings are similar in the upper and lower extremities and are more pronounced in women. The abovementioned patterns may be considered effective indicators for identifying CP in the older adult population.

0.6-V 1.65-μW Second-Order Gm-C Bandpass Filter for Multi-Frequency Bioimpedance Analysis Based on a Bootstrapped Bulk-Driven Voltage Buffer

A bootstrapping technique used to increase the intrinsic voltage gain of a bulk-driven MOS transistor is described in this paper. The proposed circuit incorporates a capacitor and a cutoff transistor to be connected to the gate terminal of a bulk-driven MOS device, thus achieving a quasi-floating-gate structure. As a result, the contribution of the gate transconductance is cancelled out and the voltage gain of the device is correspondingly increased. The technique allows for implementing a voltage follower with a voltage gain much closer to unity as compared to the conventional bulk-driven case. This voltage buffer, along with a pseudo-resistor, is used to design a linearized transconductor. The proposed transconductance cell includes an economic continuous tuning mechanism that permits programming the effective transconductance in a range sufficiently wide to counteract the typical variations that process parameters suffer during fabrication. The transconductor has been used to implement a second-order Gm-C bandpass filter with a relatively high selectivity factor, suited for multi-frequency bioimpedance analysis in a very low-voltage environment. All the circuits have been designed in 180 nm CMOS technology to operate with a 0.6-V single-supply voltage. Simulated results show that the proposed technique allows for increasing the linearity and reducing the input-referred noise of the bootstrapped bulk-driven MOS transistor, which results in an improvement of the overall performance of the transconductor. The center frequency of the bandpass filter designed can be programmed in the frequency range from 6.5 kHz to 37.5 kHz with a power consumption ranging between 1.34 μW and 2.19 μW. The circuit presents an in-band integrated noise of 190.5 μVrms and is able to process signals of 110 mVpp with a THD below −40 dB, thus leading to a dynamic range of 47.4 dB.

Assessment of Standing Multi-Frequency Bioimpedance Analyzer to Measure Body Composition of the Whole Body and Limbs in Elite Male Wrestlers

We investigated differences in body composition measurements for the whole body and limb segments in elite male wrestlers between results of multi-frequency bioelectrical impedance analyses (MFBIA) and dual energy X-ray absorptiometry (DXA). Sixty-six elite male wrestlers from Taiwan were recruited. Wrestlers' body fat percentage (PBFWB), whole body fat-free mass (FFMWB), whole body lean soft tissue mass (LSTMWB), and fat-free mass of arms, legs and trunk (FMArms, FFMLegs, FFMTrunk) were measured by MFBIA and DXA, and analyzed using Pearson correlation coefficient and Bland-Altman plot. Correlations of FFMWB, LSTMWB, and PBFWB between devices were 0.958, 0.954, and 0.962, respectively. Limits of agreement (LOA) of Bland-Altman plot were -4.523 to 4.683 kg, -4.332 to 4.635 kg and -3.960 to 3.802%, respectively. Correlations of body composition parameters FFMArms, FFMLegs and FFMTurnk between devices in each limb segment were 0.237, 0.809, and 0.929, respectively; LOAs were -2.877 to 2.504 kg, -7.173 to -0.015 kg and -5.710 to 0.777 kg, respectively. Correlation and consistency between the devices are high for FFM, LSTM and PBF but relatively low for limb segment FFM. MFBIA may be an alternative device to DXA for measuring male wrestlers' total body composition but limb segment results should be used cautiously.