Identifying clinically meaningful tools for measuring comfort perception of footwear

Purpose: Measures of comfort are important in the prescription and development of footwear. The purpose of our study was to examine three commonly used scales (visual analog scale (VAS), Likert scale, and ranking scale) to determine the most reliable, to calculate a minimal clinically important change in rating scales, and to explore dimensions of comfort important to the patient. Methods: Twenty subjects were allocated consecutively to two experiments consisting of five sessions of repeated measures. Using comfort measures from each subject's usual jogging shoe, experiment 1 examined the reliability of VAS and Likert scale over six dimensions of the foot, including overall comfort. The second experiment examined the reliability of ranking scale by assessing the ranked position of the shoe. Comfort measures were obtained in both walking and jogging. Results: The ranking scale was the most stable scale. Mixed linear modeling found that VAS was more stable than the Likert scale. The VAS required two sessions to become reliable for all measures but those obtained from the heel, which required more. Using a data-derived approach, a clinically important change in comfort was 9.59 mm on the 100-mm VAS; using an anchor-based approach, it was 10.2 mm. Subjects identified arch comfort as the most important consideration in footwear comfort. Conclusions: Ranking scale and VAS are reliable measures of footwear comfort. Using the VAS, changes of 9.59 and 10.2 mm indicate a clinically relevant change in comfort. The most important dimensions to the patient are overall comfort and the arch.