Exploring methods for analyzing abnormal gait using portable devices

【BACKGROUND】 With the recent evolution of mobile devices, methods to collect data on physical exercise using devices that are carried on daily have been attracting attention. In particular, sensors built into smartphones are readily available at low cost, making biometric measurements easy. 【Purpose】 This study investigates differences in gait patterns based on a quaternion obtained by employing a mobile device as a motion sensor. 【Method】 The subject was a healthy adult male (47 years old, 171 cm, 80 kg) who performed simulated Trendelenburg gait, Circumduction gait, Duchenne gait (with hip abduction), and Duchenne gait (without hip abduction) as normal gait and clinically commonly observed abnormal gait. The walking distance was 10m, and the measurements were five each. While walking, a mobile device (iPhone iOS 17.4.1) was worn on the abdomen with an application capable of recording triaxial acceleration, angular velocity, and quaternion. Vertical axis quaternions corresponding to pelvic rotation movements were extracted from the analyzed data. The analysis interval was one gait cycle. Walking was video recorded from the front (30 fps), and the number of steps and the time of the analysis interval were measured. 【Result】 In normal gait, pelvic rotation was equal on both sides. In the Trendelenburg gait, pelvic rotation with a pelvic drop during the stance phase. In Circumduction gait, there was pelvic movement associated with hip abduction. In the Duchenne gait, there was less change in pelvic rotation movement during the stance phase. 【Consideration】 The quaternion results revealed the possibility of different patterns in different gait types. Although quaternions are not a direct indicator of rotational motion, they may be a valuable tool for understanding gait. 【Implications】 A low-cost and efficient gait analysis method using mobile terminals can be developed and used as a tool for early detection of abnormal gait, physical therapy evaluation, and education.