Polio survivors have poorer walking adaptability than healthy individuals

Background: Falling is a major health problem in polio survivors, often occurring as a result of tripping, slipping or misplaced steps. Therefore, reduced walking adaptability possibly plays an important role. Research question: Does walking adaptability, assessed on an interactive treadmill, differ between polio survivors and healthy individuals? Methods: In this cross-sectional study, 48 polio survivors with at least one reported fall in the past year and/or fear of falling and 25 healthy individuals of similar age walked at self-selected comfortable fixed speed on an instrumented treadmill. Walking adaptability was measured as i) target-stepping accuracy (determined as variable error [VE] in mm independent of speed) in three conditions; 0 %, 20 % and 30 % variation in step length and width, and ii) anticipatory and reactive obstacle avoidance (ObA and ObR, in percentage successfully avoided). All trials were checked for valid step detection. Results: 46 polio survivors (mean +/- SD age: 63.2 +/- 8.7 years) and 25 healthy individuals (64.3 +/- 6.6 years, p = 0.585) showed valid step detection. Compared to healthy individuals (mean +/- SE VE: 30.6 +/- 1.2 mm), polio survivors stepped less accurately onto targets (36.4 +/- 0.9 mm, p = 0.001), especially with their least-affected leg. Polio survivors avoided fewer obstacles successfully (mean +/- SE ObA: 83 +/- 3 %, ObR: 59 +/- 4 %) than healthy individuals (100 +/- 0.3 %, p < 0.001 and 94 +/- 3 %, p < 0.001, respectively), with a stronger decline in success rates from anticipatory to reactive obstacle avoidance for polio survivors (p < 0.001). Significance: Polio survivors reporting falls and/or fear of falling had a demonstrably reduced walking adaptability, especially so for reactive obstacle avoidance, which requires step adjustments under high time-pressure demands. Future research should study the merit of walking-adaptability assessment to currently used clinical methods of fall-risk assessment within this population.