Gait characteristics during inadvertent obstacle contacts in young, middle-aged and older adults.

BACKGROUND: When stepping over obstacles, analyses have focused on the successful trials to understand adaptive gait. However, examination of the inadvertent trips that occasionally occur in the laboratory can provide a rich source of information regarding the gait characteristics underlying trip-related falls. RESEARCH QUESTION: What gait variables during obstacle crossing are associated with inadvertent obstacle contacts, and are these variables different across the lifespan? METHODS: Three age groups included: young adults (20-35 years, N = 20), middle-aged adults (50-64 years, N = 15), and older adults (65-79 years, N = 19). A stationary, visible obstacle (26 cm tall) was placed in the middle of a walkway. Foot trajectories and head angles were compared between contact and non-contact trials. RESULTS: Twelve participants contacted the obstacle: seven young adults (3.5% of young adult trials), two middle-aged adults (1.3%), and three older adults (1.6%). Young and middle-aged adults contacted primarily with the trail limb, while older adults contacted primarily with the lead limb. Contacts occurred for different reasons: Most young adult contact trials had appropriate foot placement, but inadequate elevation; middle-aged and older adults demonstrated inappropriate foot placement before the obstacle, leading to foot contact during the swing phase. SIGNIFICANCE: Lower contact rates in the middle-aged and older adults indicates that the cautious strategies adopted during obstacle crossing are effective. Higher contact rates in young adults may indicate trial-and-error exploratory behavior. Inappropriate foot placement in the middle-aged and older adults may indicate impaired ability to gather obstacle position information during the approach phase.