Assessment of surface EMG biomarkers in sarcopenic motor dysfunction during postural stabilization.

Purpose: This study aimed to investigate neuromuscular adaptations in individuals with pre/sarcopenia during postural balance perturbations, using surface electromyography (sEMG) signal features as potential functional biomarkers of early motor decline.

Methods: Twenty-eight older adults (14 pre/sarcopenic, 14 controls) were subjected to a series of forward balance perturbations while standing on a force platform. sEMG signals were recorded from four lower limb muscles and analyzed across five defined postural epochs established by the perturbation. Six sEMG features were extracted to capture amplitude, frequency, shape, and complexity characteristics of the signals. Linear mixed-effects models were used to evaluate group differences and trial-by-trial adaptation.

Results: The Post-stab epoch (350-2350 ms post-perturbation) revealed the most pronounced differences between groups. The pre/sarcopenic group exhibited significantly lower amplitude and complexity values. Additionally, shape analysis showed a distribution more closely resembling a Laplacian profile in the pre/sarcopenic group, indicative of increased motor unit synchronization and diminished recruitment variability.

Conclusion: This study identifies specific sEMG-derived features, particularly signal shape and complexity metrics, as potential non-invasive biomarkers for neuromuscular decline in sarcopenia. The Post-stab epoch emerges as a sensitive window for detecting deficits in motor control, supporting the use of perturbation-based tasks and sEMG analysis for early detection, monitoring, and intervention planning in aging populations.