Construct Validity And Reproducibility of C-Mill Walking-Adaptability Assessment in Polio Survivors

Research Objectives To the assess construct validity and reproducibility of walking-adaptability assessment on an instrumented treadmill (the C-Mill) in polio survivors. Design Observational study with two repeated walking-adaptability measurements (target stepping, with 0%, 20% and 30% target position variance, and anticipatory and reactive obstacle avoidance), separated by 2-3 weeks. Setting Outpatient clinic of a university hospital. Participants Polio survivors (n=46) who fell in the previous year and/or reported fear of falling. Interventions Not applicable. Main Outcome Measures We examined 1) face validity by determining Group (for subgroups stratified for fall frequency, fear of falling and leg-muscle weakness) and Condition effects (for difficulty level) on walking-adaptability outcomes, 2) construct validity by correlating walking-adaptability and balance outcomes, and 3) content validity by establishing possible ceiling effects. We determined whether face-validity findings were reproducible over test occasions and calculated Intraclass Correlation Coefficients (ICC) and the 95% Limits of Agreement (LoA) for walking-adaptability outcomes. Results Walking-adaptability outcomes differed in to-be-expected directions for subgroups stratified for fall frequency and leg-muscle weakness and for difficulty levels, all reproducible over test occasions. Correlations between walking-adaptability and balance outcomes were mainly low (r Conclusions We proved face, construct and content validity of C-Mill walking-adaptability assessment in polio survivors with a history and/or fear of falling. Adding walking-adaptability assessment, particularly the more challenging tests given their superior reproducibility, to currently used clinical tests could improve fall-risk evaluation in this population. Author(s) Disclosures None.