Poststroke consequences upon optimization properties of postural sway during upright stance: a cross-sectional study

Background The understanding of human postural control has advanced with the introduction of optimization process modeling. These models, however, only provide control parameters, rather than analytical descriptors of optimization processes. Here, we use a newly developed direct (pattern) search algorithm to investigate changes in postural optimization process in poststroke individuals. Objective This cross-sectional study investigated the optimization properties of postural stability during upright standing in poststroke individuals. Methods Twenty-nine poststroke and 15 healthy age-matched individuals underwent posturography with a force platform while standing for 60 s for acquisition of center-of-pressure data. Poststroke individuals were grouped depending on their weight-bearing (WB) pattern and their balance capability assessed through Berg Balance Scale (BBS). The optimization properties of postural stability were computed assuming the minimization of postural sway as cost function. Results The asymmetric WB poststroke group showed larger convergence rate toward the local minimum of postural sway than the symmetric WB group. Additionally, the low-balance capability group exhibited smaller values for averaged local minima and global minimum of postural sway coordinates compared with high-balance capability group. Significant correlations were found for BBS and the local minima and global minimum (Pearson's r ranged 0.378-0.424, P < 0.05). Conclusions In summary, the optimization properties describing postural dynamic stability, steadiness, and global reference are altered in poststroke individuals with asymmetric WB pattern and low-balance capability.

Automated summary

This study investigated the optimization properties of postural stability in poststroke individuals using a direct search algorithm. The results showed that the asymmetric weight-bearing poststroke group had a faster convergence rate towards the local minimum of postural sway, while the low balance capability group had smaller values for average local minima and global minimum of postural sway coordinates. Significant correlations were found between the Berg Balance Scale and the local minima and global minimum.