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.

The 12-week SJ program was easily performed by older adults with low skeletal muscle mass, improved aerobic capacity, muscle function, and muscle composition in older adults.

BackgroundSkeletal muscle experiences both quantitative and qualitative changes with aging. Echo intensity (EI) of the skeletal muscle obtained by ultrasonography (US) has been considered to reflect muscle quality. This technique is noninvasive, easily accessible, and is relatively inexpensive than that of other imaging techniques such as computed tomography (CT). Previous studies have reported that EI is related to several physical performances. However, few studies have investigated the validity of EI against other imaging methods in case of imaging of the skeletal muscle. We compared quantitative and qualitative indices evaluated by the US and CT imaging systems to strengthen their validity.Participants and methodsA total of 40 adults participated in this study: 19 young (10 men and 9 women; their mean (±SD) age was 22.7±1.5 years) and 21 older adults (13 men and 8 women; their mean age was 70.6±4.8 years). Both thighs of each participant were evaluated using US and CT imaging systems.ResultsWith respect to the US indices, the young group had significantly higher muscle thickness (MT) of the front thigh (P<0.001) and lower EI (P=0.001) than that of the older group. With respect to the CT indices, the cross-sectional area (CSA) and mean CT value (Hounsfield unit [HU]) of the muscle were found to be significantly higher in the young group (P<0.001) than that of the older group, whereas the percentage of low-density muscle area (%LDMA) was found to be significantly higher in the older group (P<0.001) than that of the young group. A significant, strong, and positive correlation was observed between MT and CSA, which reflects the muscle quantity (r=0.774; P<0.001). With respect to the indices of muscle quality, we found significant and moderate correlations between EI and CT values (r=−0.502; P<0.001) and between EI and %LDMA (r=0.441; P<0.001). However, these correlations were found to be decreased in the older group [between EI and CT value (r=−0.363; P=0.018) and between EI and %LDMA (r=0.257; P=0.100)].ConclusionResults of this study indicate that the EI is moderately associated with muscle attenuation as assessed by CT, which means that higher EI at least partly reflects intramuscular lipid infiltration.

No abstract

Bioelectrical impedance analysis (BIA) has been used to estimate skeletal muscle mass, but its application in the elderly is not optimal. The accuracy of BIA may be influenced by the expansion of extracellular water (ECW) relative to muscle mass with aging. Multifrequency BIA (MFBIA) can evaluate the distribution between ECW and intracellular water (ICW), and thus may be superior to single-frequency BIA (SFBIA) to estimate muscle mass in the elderly. A total of 58 elderly participants aged 65-85 years were recruited. Muscle cross-sectional area (CSA) was obtained from computed tomography scans at the mid-thigh. Segmental SFBIA and MFBIA were measured for the upper legs. An index of the ratio of ECW and ICW was calculated using MFBIA. The correlation between muscle CSA and SFBIA was moderate (r = 0.68), but strong between muscle CSA and MFBIA (r = 0.85). ECW/ICW index was significantly and positively correlated with age (P < 0.001). SFBIA tends to significantly overestimate muscle CSA in subjects who had relative expansion of ECW in the thigh segment (P < 0.001). This trend was not observed for MFBIA (P = 0.42). Relative expansion of ECW was observed in older participants. The relative expansion of ECW affects the validity of traditional SFBIA, which is lowered when estimating muscle CSA in the elderly. By contrast, MFBIA was not affected by water distribution in thigh segments, thus rendering the validity of MFBIA for estimating thigh muscle CSA higher than SFBIA in the elderly.