Development of a Wearable Framework for the Assessment of a Mechanical-Based Indicator of Falling Risk in the Field

Abstract

The characterization of the instability of gait is a current challenge of biomechanics. Indeed, risks of falling naturally result from the difficulty to control perturbations of the locomotion pattern. Hence, the assessment of a synthetic parameter able to quantify the instability in real time will be useful for the prevention of falls occurring in this context. Thus, the objective of the present study, in two steps, was to propose and evaluate a relevant parameter to quantifiy the risk of fallings. Experimental analysis of the gait of 11 able-bodied subject from a motion capture system in laboratory condition was performed. The distance of the Body Center of Mass (BCOM) to the Minimal Moment Axis (MMA) was computed as a proxy of whole-body angular momentum variations. In a second step, we quantified the kinematics during gait with wearable Inertial Measurement Units (IMU) fixed on two individuals (one able bodied person and one person with transfemoral amputation). We compared the IMU-based BCOM kinematics with a motion capture reference system to verify the accuracy of our measures in the field. Normative thresholds of the distance of the Body Center of Mass (BCOM) to the Minimal Moment Axis (MMA) during able-bodied level walking were assessed. The average error between the BCoM displacement computed from the IMU and from the reference vicon data of 4 mm, 3 mm and 53 mm on the mediolateral, antero posterior and vertical axes respectively. All these results make it possible to consider the determination of the risks of falls in the field at mid-term. the research on an optimal configuration that maintain the performance while simplifying the device will be essential to make it acceptable by the individuals. • Gait instability can be quantified by the distance between the BCoM and the Minimal Moment Axes. • The kinematics of the BCoM can be determined with 6 wearable IMUs fixed at the lower limbs. • It should be possible to quantify the gait instability in the field with IMUs.