Ambulatory gait analysis with accelerometer on smart phone

Gait analysis has been used to investigate gait features in the clinical field and to monitor activities in daily-living. MEMS (micro electro-mechanical system) inertial sensors such as accelerometers and gyroscopes are suitable for ambulatory human motion analysis because they are small, light, and cheap. Smart phones have many advantages such as built-in accelerometers, magnetometers, and wireless communication. In this study, an ambulatory gait analysis method using an accelerometer in a smart phone is presented. The smart phone is attached to a subject's lower trunk. The accelerometer signals are transmitted via Bluetooth and saved on a PC. Foot contacts are detected by the peak of the forward acceleration signal, and the supporting leg is determined from the sign of the mediolateral displacement or mediolateral acceleration. This method is verified using an optical motion capture system for sampled gait steps. The feasibility is evaluated using the walking patters of five young, healthy subjects. Several specific topics regarding a smart phone's application to gait analysis are addressed. This study shows the feasibility of using a smart phone to analyze gait parameters.