title: A new measure of trip risk integrating minimum foot clearance and dynamic stability across the swing phase of gait.
abstract: Minimum toe clearance (MTC) is thought to quantify the risk of the toe contacting the ground during the swing phase of gait and initiating a trip, but there are methodological issues with this measure and the risk of trip-related falls has been shown to also be associated with gait speed and dynamic stability. This paper proposes and evaluates a new measure, trip risk integral (TRI), that circumvents many issues with MTC as typically calculated at a single point by considering minimum foot clearance across the entire swing phase and taking into account dynamic stability to estimate risk of falling due to a trip rather than risk of the foot contacting the floor. Shoes and floor surfaces were digitized and MTC and TRI calculated for unimpaired younger (N=14, age=26±5), unimpaired older (N=14, age=73±7), and older adults who had recently fallen (N=11, age=72±5) walking on surfaces with no obstacles, visible obstacles, and hidden obstacles at slow, preferred, and fast gait speeds. MTC and TRI had significant (F≥5, p≤0.005) but differing effects of gait speed and floor surface. As gait speed increased (which increases risk of trip-related falls) MTC indicated less and TRI greater risk, indicating that TRI better quantifies risk of falling due to a trip. While MTC and TRI did not differ by subject group, strong speed-related effects of TRI (F≥8, p≤0.0007) resulted in improved TRI for fallers due to their slower self-selected preferred gait. This demonstrates that slower gait is both an important covariate and potential intervention for trip-related falls.
authors.affiliation: VA Office of Research and Development, Washington, DC, United States. Electronic address: Brian.Schulz@va.gov.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Schulz
mesh_terms: D000058:Accidental Falls / Q000517:prevention & control; D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D005430:Floors and Floorcoverings; D005528:Foot / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008297:Male; D055595:Mechanical Phenomena; D018570:Risk Assessment; D055815:Young Adult
keywords: Dynamic stability; Fallers; Irregular floor; Minimum toe clearance; Obstacles; Older adults; Tripping