Footlift asymmetry during obstacle avoidance in high-risk elderly.

OBJECTIVES

To test the hypothesis that vertical footlift asymmetries and low obstacle clearing distance during obstacle avoidance are characteristics of elderly people classified as high risk for falls.

DESIGN

Controlled cross-sectional design with two conditions to cue selection of the foot-for-step initiation: sound cue and visual cue.

SETTING

Senior independent living facilities.

PARTICIPANTS

Eighteen community-dwelling elderly with a history of falling or prolonged Timed Up and Go score greater than 13.5 seconds, 16 elderly with no fall history and Timed Up & Go score of 13.5 seconds or less, and 15 younger subjects.

MEASUREMENTS: Video kinematic analysis of bilateral footlift displacement and velocity using reflective markers as subjects stepped over foam obstacles scaled to a maximum tolerated height.

RESULTS

High-risk elders contacted the obstacle more frequently and had significantly greater vertical footlift asymmetries adjusted for obstacle/subject height (mean+/-standard error asymmetry index for sound cue 3.25+/-0.42 cm, for visual cue 2.51+/-0.45 cm) than low-risk and younger subjects (P<.001). In low-risk elderly and younger subjects, the asymmetry index approached 0, which indicated symmetrical lower limb movements when stepping over the obstacles.

CONCLUSION

High-risk elderly show a marked asymmetry in foot clearance while stepping over an obstacle, with the lag foot clearing the obstacle at a much lower distance than the lead foot. Possible mechanisms responsible for these findings (limited hip extension and deficits in executive cognitive function) are discussed.