Influences Of Adipose And Bone Tissues On Lean Soft Tissues Estimated By BIA

Abstract

Skeletal muscle size is closely related to its mechanical usage, and so optimization of muscle mass and function is crucial for assurance of a high quality of life. Bioelectrical impedance analysis (BIA) is accepted as a useful method for assessing accurately both favorable and unfavorable changes in limb muscle size and/or lean soft tissue mass (LST) with exercise, or alternatively, early detection of muscle wasting with ageing, in humans. However, the influences of concurrent exercise/ageing related changes in adipose tissue mass (ATM) and bone mineral density (BMD) on estimates of muscle and/or LST mass by BIA have been ignored. PURPOSE The purpose of this study is to investigate the influences of BMD and ATM on the accuracy of BIA estimates of LST in the forearm. METHODS Fifteen healthy females (age: 34.5 ± 4yrs, height: 163.6 ± 7.2cm, body mass: 71.6 ± 18.9 kg, mean ± SD) were recruited as subjects. The bio-electrical impedance (BI) of the whole forearm (elbow to wrist in the right arm) was measured. The LST of the whole forearm was obtained by DXA (LSTDXA) and used as reference data. A simple regression equation for the relationship between the LST index (forearm length2/BI) and (LSTDXA) was used to estimate LST (LSTBIA). BMD and ATM of the whole forearm were also obtained by DXA. RESULTS The LSTBIA was strongly correlated with the LSTDXA (r=0.857, P < 0.05, SEE=50.2g, 7.2%). Bland and Altman plot did not show a significant systematic error. There was no significant correlation between ATM and BMD. However, the residual (LSTBIA - LSTDXA) of the estimate was negatively and positively related to BMD (r=−0.536, p < 0.05) and ATM (r=0.635, p < 0.05), respectively. CONCLUSION The findings obtained here indicate that bio-electrical impedance analysis is applicable to estimate limb lean soft tissue mass, but the error of estimation is affected by both adipose tissue mass and bone mineral density.