Electrical Impedance Myography Quantifies Holding and Pushing During Isometric Muscle Contractions

Area of Science:

• Biomedical Engineering
• Physiology
• Geriatrics

Background:

• Age-related muscle loss (sarcopenia) impacts mobility and health in older adults.
• Accurate assessment of muscle performance is crucial for geriatric care and rehabilitation.
• Current methods may not fully capture dynamic muscle function during specific exercises.

Purpose of the Study:

• To introduce and evaluate a local Electrical Impedance Myography (EIM) framework for the quadriceps femoris muscle group.
• To assess EIM's capability for estimating muscle force during isometric seated leg extension exercises.
• To explore EIM as a tool for geriatric assessment and tracking therapeutic interventions.

Main Methods:

• A pilot study was conducted with ten healthy male adults performing isometric leg extensions.
• Electrical Impedance Myography (EIM) signals were recorded and analyzed using Debye/Cole models and characteristic frequency.
• Muscle activity was normalized, and torque was estimated by multiplying estimated activity by maximal voluntary torque.

Main Results:

• Systematic variations in EIM signals were observed due to joint angle, isometric pushing, and repetitive contractions.
• Resistance and reactance showed sensitivity to muscle activity below a specific frequency (${f} \leq {f}_{x}$).
• A strong Pearson correlation (nearly 0.9) was found between EIM parameters and muscle torque.

Conclusions:

• The developed EIM framework demonstrates potential for non-invasive muscle force estimation.
• EIM shows promise as a tool for assessing muscle function in geriatric populations.
• The study highlights the sensitivity of EIM to muscle contractions and its correlation with torque.