Maximum force and the center of pressure trajectory length according to foot angles during stair walking

[Purpose] Walking with the feet turned inward or outward often causes issues for the people with these walking patterns. The purpose of this study was to examine the influence of in-toeing and out-toeing on maximum force and the center of pressure (COP) trajectory length during stair walking. [Subjects and Methods] The subjects were 30 female university students without orthopedic diseases of the foot. The foot angle was divided into three types: in-toeing, normal, and out-toeing. A plantar pressure measurement instrument was used, and the maximum force was obtained by dividing the foot into six regions covering the anterior medial-lateral, middle medial-lateral, and posterior medial-lateral regions. The COP trajectory length was statistically calculated by measuring the medial-lateral, anterior-posterior, and total travel distances. [Results] During stair climbing, the maximum force was significantly different in the anterior lateral region. During stair descending, the maximum force was significantly different in the anterior lateral, middle medial, middle lateral, posterior medial, and posterior lateral regions. The COP trajectory length showed a statistically significant difference in the medio-lateral travel distance. [Conclusion] Walking with abnormal foot angles causes deformed foot structures and can result in musculoskeletal disabilities in the long term. Therefore, therapeutic intervention is required to maintain normal foot angles.