Toward Clinically Feasible Assessment of Muscle Mass: Validation of a Seated Bioelectrical Impedance Device Against Dual-Energy X-Ray Absorptiometry (DXA) in Older Adults.
Piche E, Michel E, et al. • Sensors (Basel, Switzerland) • 2026
Seated bioelectrical impedance analysis provides clinically acceptable estimates of appendicular skeletal muscle mass in older adults, with the Sergi equation demonstrating superior accuracy compared to the Kyle equation when validated against DXA.
Key Findings
Results
The Sergi equation showed better agreement with DXA than the Kyle equation for estimating appendicular skeletal muscle mass using seated BIA.
Sergi equation bias was lower at 0.44 kg vs. Kyle equation bias of 1.11 kg
Sergi equation RMSE was lower at 1.33 kg vs. Kyle equation RMSE of 1.96 kg
Mean absolute error (MAE) was also lower for the Sergi equation
Results support the use of population-specific equations for BIA-based ASMM estimation
Results
Both the Kyle and Sergi equations demonstrated good overall agreement with DXA measurements of appendicular skeletal muscle mass.
Study sample consisted of 59 older adults with mean age 75 ± 7 years
Agreement was assessed using Lin's concordance correlation coefficient, Bland-Altman analysis, RMSE, and MAE
The device used was the Biody XpertZM3 seated BIA device
Both equations were classified as showing 'good agreement' with the DXA reference standard
Seated BIA was described as providing 'clinically acceptable estimates' of ASMM in older adults
Results
Phase angle (PhA) from seated BIA was positively correlated with handgrip strength in older adults.
Pearson correlation coefficient r = 0.315, p = 0.015
This association was statistically significant
PhA was not significantly associated with five-times sit-to-stand (5-STS) performance
Authors suggest PhA 'may provide additional information on muscle quality and sarcopenia'
Associations were evaluated alongside physical performance measures as secondary outcomes
Results
Phase angle was not associated with five-times sit-to-stand (5-STS) performance in the study sample.
The 5-STS test was used as a measure of lower limb physical performance
No statistically significant association was found between PhA and 5-STS
This contrasts with the significant association found between PhA and handgrip strength
The differential associations suggest PhA may be more reflective of upper limb muscle quality or overall muscle cell integrity than functional lower limb performance
Background
Seated BIA was proposed as a practical clinical alternative to DXA for assessing appendicular skeletal muscle mass and screening for sarcopenia in older adults.
DXA is described as 'the reference method for measuring appendicular skeletal muscle mass (ASMM) and diagnosing sarcopenia'
Seated BIA validity was noted as 'still insufficiently documented in specific populations' prior to this study
The seated configuration of the BIA device (Biody XpertZM3) may improve accessibility for older or mobility-limited adults
The study frames seated BIA as a 'clinically feasible assessment' option
Population-specific equations such as Sergi are recommended to improve accuracy
What This Means
This research suggests that a type of body composition measurement device called seated bioelectrical impedance analysis (BIA) can reliably estimate muscle mass in older adults when compared against the gold-standard method, dual-energy X-ray absorptiometry (DXA). The study tested 59 older adults (average age 75 years) and found that seated BIA produced measurements that closely matched DXA results. Importantly, one particular mathematical formula used to interpret the BIA data — called the Sergi equation — worked better than another commonly used formula (the Kyle equation), producing estimates closer to DXA with less error and less systematic bias.
The study also examined whether a BIA measurement called 'phase angle' — which reflects the health and integrity of muscle cells — was related to physical performance. Phase angle was positively associated with handgrip strength, suggesting it may capture something meaningful about muscle quality. However, it was not linked to performance on a test of lower body function (the five-times sit-to-stand test), indicating phase angle may not capture all aspects of physical capability.
This research matters because DXA machines are expensive, large, and not available in many clinical settings such as doctor's offices or community health clinics. A seated BIA device is smaller, less costly, and easier to use, especially for older adults who may have difficulty standing or lying still. This research suggests that seated BIA, particularly when using population-appropriate equations like the Sergi formula, could offer a practical and reasonably accurate way to screen older adults for low muscle mass (sarcopenia) in everyday clinical settings.
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Piche E, Michel E, Guerin O, Gouraud E, Chorin F. (2026). Toward Clinically Feasible Assessment of Muscle Mass: Validation of a Seated Bioelectrical Impedance Device Against Dual-Energy X-Ray Absorptiometry (DXA) in Older Adults.. Sensors (Basel, Switzerland). https://doi.org/10.3390/s26165112