One-leg stance in healthy young and elderly adults: a measure of postural steadiness?

Objective. To investigate postural steadiness during 30 s of one-leg stance in healthy young and elderly adults, by analysing the pattern of the ground reaction force variability. Design. A laboratory set-up was used to analyse the variability of the ground reaction forces in relation to time as a measure of postural steadiness. Background. The one-leg stance test is a measure considered to assess postural steadiness in a static position by a temporal measurement. The common notion is that a better postural steadiness, i.e. less force variability, allows for longer time standing on one leg. However, there is lack of evidence how postural steadiness during one-leg stance changes over time. Methods. Twenty-eight healthy elderly and 28 healthy young adults were tested by means of force plates assessing ground reaction forces while performing one-leg stance. Results. During one-leg stance, two phases could be identified in both groups: First a dynamic phase, a rapid decrease of force variability, and thereafter a static phase, maintaining a certain level of force variability. During the first 5 s of one-leg stance the force variability decreased significantly more in the young group resulting in a lower force variability level during the static phase than in the elderly. Conclusions. The difficulties in maintaining the static position in elderly seems dependent on the reduced initial decrease in force variability and/or musculoskeletal components. We suggest that the first 5 s are crucial when assessing balance during one-leg stance.