Cross-sectional and longitudinal agreement between two multifrequency bioimpedance devices for resistance, reactance,...

Area of Science:

• Physiology
• Biomedical Engineering
• Exercise Science

Background:

• Raw bioelectrical variables like resistance (R), reactance (Xc), and phase angle (φ) are crucial for assessing physiological changes.
• Accurate measurement of these variables is essential for reliable physiological monitoring and research.

Purpose of the Study:

• To compare multifrequency bioelectrical impedance analysis (MFBIA) and bioimpedance spectroscopy (BIS) devices.
• To evaluate cross-sectional and longitudinal agreement of R, Xc, and φ measurements between MFBIA and BIS.
• To determine device accuracy for detecting changes following resistance training.

Main Methods:

• Adult females underwent resistance training for 8 weeks.
• Measurements of R, Xc, and φ were taken using MFBIA and BIS devices before and after training.
• Data were analyzed for cross-sectional and longitudinal differences and correlations across 16 shared frequencies (3–1000 kHz).

Main Results:

• Strong cross-sectional correlations (r ≥ 0.96) for R were observed, with MFBIA yielding higher values (9–14%).
• Strong cross-sectional correlations (r ≥ 0.92) for Xc and φ were found up to ~150 kHz, with device-specific differences at various frequencies.
• Longitudinal changes (ΔR, ΔXc, Δφ) showed good group-level agreement between devices, but individual-level errors were high.

Conclusions:

• Despite cross-sectional differences, MFBIA and BIS demonstrate group-level agreement in detecting training-induced changes in bioelectrical variables.
• Significant individual-level errors in longitudinal measurements raise concerns about the clinical utility of these devices for precise individual monitoring.
• Further research is needed to refine bioimpedance measurement techniques for improved individual accuracy.