Gait recording with inertial sensors--How to determine initial and terminal contact.

Lightweight inertial sensors are increasingly used for recording of gait in medicine, rehabilitation and sport. Several distinct events during the gait cycle such as heel-strike or toe-off have to be detected in the data obtained from these sensors. We re-investigated the correlation between the data of shank-mounted gyroscopes and three reference systems, namely accelerometers, pressure-sensitive soles and a motion capture system in a group of 14 young healthy men. We confirmed that the heel strike corresponds to a trough in the gyroscope curve, as several previous reports have stated. However, the toe-off moment clearly did not coincide with another trough of the gyroscope trace, as had been assumed in the past. The heel-off moment was reliably at 51% of the step cycle, irrespective of gait velocity, in our data. These findings are crucial for gait recording systems which aim to assess the temporal as well as spatial descriptors of human gait.