Quantification of whole-body and segmental skeletal muscle mass using phase-sensitive 8-electrode medical bioelectrical impedance devices

Abstract

Background/Objectives:Bioelectrical impedance analysis (BIA) provides noninvasive measures of skeletal muscle mass (SMM) and visceral adipose tissue (VAT). This study (i) analyzes the impact of conventional wrist-ankle vs segmental technology and standing vs supine position on BIA equations and (ii) compares BIA validation against magnetic resonance imaging (MRI) and dual X-ray absorptiometry (DXA).Subjects/Methods:One hundred and thirty-six healthy Caucasian adults (70 men, 66 women; age 40±12 years) were measured by a phase-sensitive multifrequency BIA (seca medical body composition analyzers 515 and 525). Multiple stepwise regression analysis was used to generate prediction equations. Accuracy was tested vs MRI or DXA in an independent multiethnic population.Results:Variance explained by segmental BIA equations ranged between 97% for total SMMMRI, 91–94% for limb SMMMRI and 80–81% for VAT with no differences between supine and standing position. When compared with segmental measurements using conventional wrist-ankle technology. the relationship between measured and predicted SMM was slightly deteriorated (r=0.98 vs r=0.99, P<0.05). Although BIA results correctly identified ethnic differences in muscularity and visceral adiposity, the comparison of bias revealed some ethnical effects on the accuracy of BIA equations. The differences between LSTDXA and SMMMRI at the arms and legs were sizeable and increased with increasing body mass index.Conclusions:A high accuracy of phase-sensitive BIA was observed with no difference in goodness of fit between different positions but an improved prediction with segmental compared with conventional wrist-ankle measurement. A correction factor for certain ethnicities may be required. When compared with DXA MRI-based BIA equations are more accurate for predicting muscle mass.

Limitations of Fat-Free Mass for the Assessment of Muscle Mass in Obesity

“…In obesity, a higher hydration of FFM is due to an increased water fraction of FFM in adipose tissue [17]. For obesity, these effects were not adequately accounted for in the original BIA equations [4, 15], since inclusion criteria for the reference population used to generate the BIA algorithm were limited to BMI <35 kg/m 2 [15]. On the other hand, overestimation of FFM by DXA can be explained by an underestimation of trunk FM by fan beam DXA devices [18].…”

“…kg., Hamburg, Germany) was used for BIA measurements, and a 4C model based on D 2 O dilution, DXA, and ADP was used as reference for FFM, whereas whole-body magnetic resonance imaging (MRI) and sodium bromide (NaBr) dilution were used as references for SMM and ECW, respectively. Details of the study protocol were described previously [4, 15]. In a second phase, 35 obese Caucasian men and women with a BMI ≥30 kg/m 2 were examined using the same study protocol.…”

“…In a first phase of this study, 153 Caucasian men and women with a BMI <35 kg/m 2 were recruited from the area of Kiel, Germany, and FFM and SMM prediction equations for the seca medical body composition analyzer (mBCA) devices were developed [4, 15]. A seca mBCA 515 device (seca gmbh & co.…”

“…Identification of muscle loss at an early stage as well as monitoring of body composition during therapeutic interventions are therefore critical and require repeat measurements with noninvasive and clinically accessible technology. In this regard, bioelectrical impedance analysis (BIA) has gained importance because of technological advances and improved validation of outcome measures [4]. This is supported by the growing number of publications that provide impedance-based reference data for fat-free mass (FFM) or skeletal muscle mass (SMM) [5-10].…”

“…Finally, the increase in connective tissue (i.e., adipose tissue) with obesity impairs the “metabolic quality” of FFM [4]. As a secondary aim of the study, the relationship between FFM and SMM was analyzed in order to evaluate the use of FFM as a proxy for SMM in obesity.…”