The relationship between ankle quasi-stiffness and postural stability in older adults during obstacle negotiations using the dominant and non-dominant sides.

In this study, we aimed to analyze the differences in ankle quasi-stiffness between the dominant and non-dominant sides during obstacle negotiations in older adults and examine their relationship with postural stability. A total of 16 older adult participants performed 10 obstacle-crossing trials with each limb. The margin of stability (MoS), ankle quasi-stiffness, and integrated electromyography of the tibialis anterior, soleus, and gastrocnemius lateralis in the stance limb were analyzed. Negative correlation was found between frontal-plane stiffness (p = 0.007, r = -0.371) and sagittal-plane stiffness (p = 0.027, r = -0.306) with the MoS under high fall-risk conditions during dominant-side negotiations. A similar negative correlation was found under low fall-risk conditions, with frontal-plane stiffness (p = 0.041, r = -0.473) and sagittal-plane stiffness (p = 0.001, r = -0.676) correlating with the MoS. Additionally, a positive correlation was observed between frontal-plane stiffness (p = 0.005, r = 0.361) and the MoS under high fall-risk conditions during non-dominant-side negotiations. During obstacle negotiation, when using the dominant side, ankle quasi-stiffness was lower to enhance postural stability, whereas when using the non-dominant side, ankle quasi-stiffness was greater for faster obstacle negotiation. These findings highlight distinct limb-dominance-based strategies when dealing with complex dynamic tasks. Future training methods and assistive device designs should be specifically targeted to the distinct functional roles of each limb.