Statement of the problem: Balance impairments and falls are common among people with stroke. Muscle spasticity is also common and may influence balance control. However, the effect of spasticity on balance control among people with stroke is not well understood. Methods: Twenty-seven post-stroke individuals with low or high spasticity at the ankle completed quiet standing trials with eyes open and closed. Balance control was measured by estimating centre of pressure (COP) movement and trunk sway. Results: Individuals with high spasticity had greater COP velocity, trunk sway velocity, and trunk sway velocity frequency, particularly in the eyes closed condition. These effects were predominantly in the mediolateral direction (vision by group interaction effects p= 0.033, p= 0.037, and p= 0.015 respectively). Main effect of group revealed that individuals with high spasticity had higher mediolateral mean power frequency measures (p= 0.045). Conclusion: Individuals with high spasticity post-stroke demonstrated greater balance control challenges especially in absence of vision. Furthermore, these challenges were specifically noted in the frontal plane
