Muscle Activation and Postural Sway in Response to Task Complexity: A Study of Balance Control in Older Adults

In this study, we investigate muscle activation patterns and postural sway in older adults across different stance conditions with varying challenges. Muscle activity from lower limb and trunk muscles was recorded in seven older adults during four stance tasks: double stance, tandem stance, tandem stance with a cognitive task, and tandem stance with combined cognitive and motor tasks (TSCM). We analyzed CoP (centre of pressure) features, EMG (electromyography) patterns, and the coherence between EMG-CoP, to gain insights into neuromuscular coordination and balance control. Our findings indicate that task complexity significantly impacts postural stability, with tandem stances-particularly TSCM-leading to increased instability along the anterior-posterior axis. Key stabilizing muscles, such as the gastrocnemius medialis and tibialis anterior, showed heightened activation and strong EMGCoP coherence under complex tasks, highlighting their essential role in counteracting gravitational forces to maintain balance. A lateral asymmetry in muscle activation was also observed, with left-side muscles consistently showing greater activity than right-side counterparts, suggesting lateralized contributions to postural control. These results emphasize the importance of specific muscles for stability in challenging postural tasks and may offer valuable insights for designing targeted interventions, including robotic rehabilitation systems and assistive technologies, to enhance balance and reduce fall risk in older adults.