Acute effect of continuous perturbations of the base of support on reactive balance response
摘要
Unexpected perturbations (UP) of the support base challenge balance control and require effective reactive postural mechanisms. Continuous perturbations (CPs) of the base of support also affect postural stability but their influence on reactive postural mechanisms is unclear. This study investigated the acute effects of sine-wave (SIN) and random-wave (RND) CPs on reactive postural control, and the impact of prior perturbation exposure on the subsequent static standing (ST). Twenty-seven participants (21.56 ± 0.25 years) performed a perturbation-based protocol on an electrically driven platform. A force plate was positioned on the movable platform to calculate the center of pressure (CoP) trajectory. Five 30-s SIN and RND CPs, as well as a control condition (CTRL) without CP, were administered in a randomized order, each followed by either an UP or no perturbation (NUP) in randomized and counterbalanced sub-trials. Balance performance during CPs, UP, and ST was assessed via CoP velocity and displacement, while Sample Entropy (SampEn) and Power Spectral Density (PSD) analyzed postural control mechanisms during ST. Both SIN and RND CPs enhanced (p < .01) reactive balance performance during UP compared to CTRL. Static balance performance deteriorated (p < .01) following perturbation exposure versus CTRL. SampEn decreased (p < .05) across all post-perturbation conditions, indicating a shift from automatic to voluntary control, with more pronounced reductions following the RND condition. PSD analysis revealed general post-perturbation reweighting toward proprioceptive myotatic and plantar cutaneous contributions (p < .05) which was accentuated after RND compared to SIN and CTRL. Results suggest that both predictable (SIN) and unpredictable (RND) CPs enhance reactive balance in the subsequent UP, likely by potentiating sensory feedback and adaptive motor responses. Conversely, the worsening of static balance performance appears related to the temporal proximity to the preceding perturbation, regardless of perturbation type.