In addition to a measurement system, appropriate algorithmic approaches are needed to accurately delineate limb’s trajectory and extract clinically relevant parameters e.g., as in a wearable gait analysis system [5]. The extraction of trajectory using body fixed sensor relies on a 2D or 3D kinematic model that takes into account the limb’s workspace.The foot trajectory tracking can be used for a comprehensive study of fall in old age [6]. Fall is considered to be a major source of morbidity and mortality in older adults and imposes huge costs to the healthcare systems [7]. The classical foot trajectory descriptors such as stride length, stride velocity and temporal parameters have been extensively investigated to determine the fall related factors [5,8,9].

When the swing foot progression is unexpectedly obstructed, a trip occurs that leads to a forward rotation of the body and eventually might cause a fall. About 53% of falls happen due to tripping [10,11], which indicates the importance of the swing foot trajectory scrutiny. Nevertheless, clinical implications of foot clearance parameters amongst old population and their inter-relation with other gait parameters have not been adequately explored. The mean and SD values of clearance parameters reported for different age groups were not consistent in the literature [12�C14] since small populations were studied. This small sample size is a natural consequence of complexity of measurement in gait laboratories. Moreover, assessment of gait variability based on limited field of view of camera-based motion capture systems (and thereof limited number of cycles) can be misleading.

The inertial measurement unit (IMU) has been employed to estimate just a limited subset of foot clearance parameters Drug_discovery [5,15]. On the other hand, by employing the IMU the measurement protocol is not anymore restricted to the in-lab capture volume. Besides, a continuous recording of the motion signals is possible contrary to the standard optical motion capture techniques when occlusion of markers could lead to loss of a part of movement trajectory.In view of the introduced problems, this study proposes the application of a shoe-worn IMU to investigate several foot clearance parameters as well as other gait parameters in a clinically relevant setting. We employed the method introduced by Mariani and co-workers in [6] to extract these parameters from gait kinematics on a population-based cohort of community-dwelling 66 to 77 year old individuals. In the second part of this paper we summarized the algorithmic approach to extract the gait temporal, spatial and clearance parameters. The third part of the study has two main focuses.