Assessment of postural stability in stable and unstable conditions

The aim of the study was to determine whether it is possible to assess static balance on an unstable surface using center of pressure velocities obtained with a force platform when standing on a wobble board. Methods: The center of pressure velocities were recorded with a force platform within three days (four trials per day) in thirty young adults in three conditions: standing on a rigid surface, compliant surface, and on a wobble board. Reliability of mean velocities of the center of pressure was examined using intraclass correlation coefficients. Relationships between the three conditions were assessed with Pearson correlation coefficients. Results: Intra-session reliability was excellent for standing on a rigid surface and on a compliant surface and good for standing on a wobble board. Inter-session reliability was good for all parameters in all conditions, except for poor reliability in the anterior-posterior direction in standing on a wobble board. All correlations between the same parameter in different conditions were statistically significant (P < 0.05), except for velocity of the center of pressure in the anterior-posterior direction between stance on a rigid surface and stance on a wobble board. Conclusions: Centre of pressure velocity parameters obtained with a force plate when standing on a wobble board can provide valuable information about postural stability in unstable conditions.