Evaluating muscle aging during relaxed standing, squats and lunges through electrical bioimpedance.

Electrical bioimpedance (EBI) is widely used for body composition analysis and shows promise for assessing muscle activation during physical activities (PAs), particularly in aging. This study investigated EBI’s sensitivity to age-related changes in muscle function by analyzing data from 40 adult participants divided into young (20–29 years), middle-aged (32–60 years), and older (62–73 years) groups. EBI signals were recorded from the Quadriceps and Extensor Digitorum Longus (EDL) muscles during three PAs: relaxed standing position, squats, and lunges. Key features were extracted to identify age-related differences. Results revealed distinct muscle-specific patterns: In the relaxed standing position, the EDL muscle exhibited a consistent, monotonic decline in the PrePAmagnitude feature from young to old adults, while the Quadriceps muscle displayed greater variability and a non-monotonic trend. Among the dynamic activities, squats revealed the most pronounced age-related differences, with 62.5% of the features showing statistical significance, whereas fewer differences in the features (25%) where shown during lunges. The findings suggest that EBI can detect age-related reductions in muscle activation and neuromuscular coordination, supporting its potential as a non-invasive tool for functional muscle assessment in aging.