Validating virtual time to contact with home-based technology in young and older adults

Virtual time to contact (VTC) is a measure of postural stability that estimates the virtual time it would take to reach an individual's stability boundary. This study aimed to validate VTC as measured by a depth sensor and determine whether VTC from the depth sensor distinguishes between older adult fallers and nonfallers compared with a force platform. VTC was assessed in 10 young and 20 older adults by having participants lean in a circular direction followed by 5 balance tests: eyes open, dual task, eyes open foam, eyes closed, and eyes closed foam. Spearman rank correlations and Bland-Altman plots were conducted to determine validity, and receiver operating characteristic curves were constructed to discriminate between fallers and nonfallers. Significant correlations were found in the dual task (P = .03), eyes open foam (P < .01), and eyes closed foam conditions (P = .05). The depth sensor discriminated between fallers and nonfallers in the eyes open (P = .02), dual task (P = .03), and eyes open foam conditions (P = .04). VTC was in agreement between the 2 devices, and VTC derived from a depth sensor can be used to discriminate between older adult fallers and nonfallers during challenging balance conditions.