Successful Negotiation of Anticipated and Unanticipated Obstacles in Young and Older Adults: Not All Is as Expected

BACKGROUND: Tripping over an obstacle is one of the most common causes of falls among older adults; however, the impact of obstacle parameters and subject characteristics are not well described. OBJECTIVES: To evaluate age-associated changes in the ability to negotiate obstacles and the role of obstacle parameters (e.g., anticipated vs. unanticipated, height, and available response time [ART]), and subject characteristics. METHODS: Twenty healthy older adults (77.7 +/- 3.4 years; 50% women) and 20 healthy young adults (29.3 +/- 3.8 years; 50% women) underwent cognitive, gait, and balance testing before negotiating a computer-controlled obstacle course. The primary outcome measure was the ability to successfully negotiate the obstacles (without touching them). RESULTS: The success rate for all subjects was higher when the obstacle was anticipated (99.0 +/- 2.8%) than when unanticipated (66.0 +/- 20.2%; p < 0.001). The obstacle height had a significant effect on the success rate (p = 0.022); the success rate was lower when the obstacle height was lower. No significant interaction between group and obstacle height was observed (p = 0.096). ART had no significant effect on the success rate (p = 0.294) in both of the groups (ART x group, p = 0.136). However, a significant interaction between group, obstacle height, and ART was found (p = 0.013), reflecting a lower success rate in the older adults when the obstacles were low and unanticipated. In general, older adults demonstrated a trend towards a lower success rate in all types of obstacles compared to the young adults (p = 0.057). Among the older adults, the success rate in the anticipated obstacle condition was correlated with stride length (rho = 0.600, p = 0.005), step time coefficient of variation (rho = -0.635, p = 0.003), and gait speed (rho = 0.530, p = 0.016). Montreal Cognitive Assessment scores tended to be related to the difference in the success rate between the anticipated and unanticipated conditions. CONCLUSIONS: These findings support the idea that motor and, to some degree, cognitive functions are needed to successfully negotiate obstacles, and provide new insights into the ability of older adults to successfully negotiate obstacles. Furthermore, the present results suggest that when it comes to the physical properties of obstacles, not all is as expected, and low obstacles may impose a greater danger to tripping than obstacles that have a higher height.