Fall risk monitoring: From laboratory to portable device, influence of sampling frequency

The understanding of locomotor stability is a critical issue in the assessment of subjects with high level of fall risk either pathological (e.g. stroke subjects) or elderly. Clinical assessment of fall risk is typically based on clinical rating scales; however, this approach heavily relies on the clinician’s subjective judgment. Instrumental stability and variability indexes of gait can represent a promising solution for the objective quantification of locomotor function and fall risk. Furthermore clusters of stability and variability indexes give important information about the clinical deficits of subjects that could be the causes of the fall risk. An important step for the improvement of the assessment of fall risk is to analyze the subject’s walk not only in the laboratory but also in his daily life. This is possible with the implementation of the stability and variability indexes in a portable device. Mobile phone is the ideal device for this goal. Indeed it is user friendly, cheap and although the IMUs mounted on standard smart phones have nothing to envy to other commercially available devices, but sampling frequency at 100 or 200 Hz is not compatible with the computational characteristics. The influence of reduced sampling frequency on the assessment of variability and stability indexes used for the monitoring must be assessed, and this is the aim of the present work. The preliminary obtained results show that the influence of the sampling frequencies in the computation of the stability and variability indexes is not an obstacle to move the assessment and monitoring of fall risk from the laboratory to a portable device.