Gait characterization using wearable inertial sensors in healthy and pathological populations

Gait analysis is emerging as an effective tool to detect an incipient neurodegenerative disease or to monitor its progression. It has been shown that gait disturbances are an early indicator for cognitive impairments and can predict progression to neurodegenerative diseases. Furthermore, gait performance is a predictor of fall status, morbidity and mortality. Instrumented gait analysis provides quantitative measures to support the investigation of gait pathologies and the definition of targeted rehabilitation programs. In this framework, technologies such as inertial sensors are well accepted, and increasingly employed, as tools to characterize locomotion patterns and their variability in research settings. The general aim of this thesis is the evaluation, comparison and refinement of methods for gait characterization using magneto-inertial measurement units (MIMUs), in order to contribute to the migration of instrumented gait analysis from state of the art to state of the science (i.e.: from research towards its application in standard clinical practice). At first, methods for the estimation of spatio-temporal parameters during straight gait were investigated. Such parameters are in fact generally recognized as key metrics for an objective evaluation of gait and a quantitative assessment of clinical outcomes. Although several methods for their estimate have been proposed, few provided a thorough validation. Therefore an error analysis across different pathologies, multiple clinical centers and large sample size was conducted to further validate a previously presented method (TEADRIP). Results confirmed the applicability and robustness of the TEADRIP method. The combination of good performance, reliability and range of usage indicate that the TEADRIP method can be effectively adopted for gait spatio-temporal parameter estimation in the routine clinical practice. However, while traditionally gait analysis is applied to straight walking, several clinical motor tests include turns between straight gait segments. Furthermore, turning is used to evaluate subjects’ motor ability in more challenging circumstances. The second part of the research therefore headed towards the application of gait analysis on turning, both to segment it (i.e.: distinguish turns and straight walking bouts) and to specifically characterize it. Methods for turn identification based on a single MIMU attached to the trunk were implemented and their performance across pathological populations was evaluated. Focusing on Parkinson’s Disease (PD) subjects, turn characterization was also addressed in terms of onset and duration, using MIMUs positioned both on the trunk and on the ankles. Results showed that in PD population turn characterization with the sensors at the ankles lacks of precision, but that a single MIMU positioned on the low back is functional for turn identification. The development and validation of the methods considered in these works allowed for their application to clinical studies, in particular supporting the spatio-temporal parameters analysis in a PD treatment assessment and the investigation of turning characteristic in PD subjects with Freezing of Gait. In the first application, comparing the pre and post parameters it was possible to objectively determine the effectiveness of a rehabilitation treatment. In the second application, quantitative measures confirmed that in PD subjects with Freezing of Gait turning 360° in place is further compromised (and requires additional cognitive effort) compared to turning 180° while walking

An objective assessment to investigate the impact of turning angle on freezing of gait in Parkinson's disease

Freezing of gait (FoG) is often described in subjects with Parkinson's disease (PD) as a sudden inability to continue the forward walking progression. FoG occurs most often during turning, especially at sharp angles. Here, we investigated 180 and 360 degrees turns in two groups: PD subjects reporting FoG (FoG+), and PD subjects without FoG (FoG-). Forty-three subjects (25 FoG+, 18 FoG-) wore an inertial sensor on their back while walking back and forth continuously for 2 min (reversing direction with a 180° turn), and while turning in place for 1 min (alternating 360° turning in opposite directions). Objective measures (turn duration, peak velocity, jerkiness and range of acceleration) were computed during the turns and compared across FoG+ and FoG-groups. Results showed that FoG+ compared to FoG-took significantly a longer time to complete 360° turns than 180° turns. A significant lower turn peak velocity, higher jerkiness and an increased range of medio-lateral acceleration was also found in FoG+. Significant differences between the two groups across the two turning tasks validated the hypothesis that sharper turns might cause higher instability in FoG+ compared to FoG-

Identification of multiple U-turns using gyroscopes : comparative assessment of two methods

The identification of turnings segments during walking trials including the U-turns represents the first preliminary step required for the analysis of gait featuring straights and turns. To this purpose IMU-based methods were developed, however many of them rely on the a-priori knowledge of the number of turns. In this study, we selected two methods and compared them to evaluate their ability to detect the number of turns in continuous gait with multiple U-turns without further assumptions. Gyroscope data were recorded during gait trials performed at different speeds by two groups of subjects (healthy elderly and patients with Parkinson disease). Results show that the method that employs a sensor on the back yields better results than the one making use of a sensor on the ankles

Identification of multiple U-turns using IMUs: Comparative assessment of three methods

4reservedmixedBertoli, M.; Cereatti, A.; Trojaniello, D.; Della Croce, U.Bertoli, M.; Cereatti, A.; Trojaniello, D.; Della Croce, U

The identification of multiple U-turns in gait : comparison of four trunk IMU-based methods

The identification of turns during walking allows for the segmentation into straight and turn walking bouts. Several IMU-based methods were developed to this purpose, however many of them were tested on specific subject population. In this study, we tested four methods for the identification of turns in walking tasks with multiple U-turns that did not exploit any a-priori knowledge of the turn occurrences. We evaluated their robustness by recording IMU data on healthy and pathological subjects (healthy elderly, stroke survivors, patients with Parkinson disease and choreic patients) walking at two different speeds along a closed loop formed by straight bouts and U-turns. Overall, all methods identified correctly the totality of the U-turns when elderly and Parkinsonian patients were analyzed. When stroke survivors and choreic patients were analyzed, U-turns were either missed or erroneously detected in a limited number of cases. The only method using the magnetometer signals was the best performing, highlighting the usefulness of the magnetometer when turns are being investigated

Can MIMUs positioned on the ankles provide a reliable detection and characterization of U-turns in gait?

The detection and characterization of U-turns during locomotion using Magneto-Inertial Measurement Units (MIMU) with the goal of segmenting the walking trial into straight walking bouts and turns is an open issue currently under investigation. Typically, a MIMU located on the lower back or trunk is used to this purpose and turns onset timing and duration are determined. The aim of this study was to assess if an existing method could be satisfactorily applied to signals recorded from MIMUs near the ankles. Additionally, a method is proposed with the aim of limiting the differences of its output from that of the existing method guaranteeing high robustness with respect to the MIMU location. The analysis was conducted on data recorded from healthy elderly subjects and patients with Parkinson's disease walking at two different speeds. The existing method applied to signals from the MIMU near the ankles could detect the same number of U-turns as the original. However, their onset and duration were often more than 200ms away from those obtained with the original method. Similar results were obtained with the proposed method, showing some limitations in part related to the heuristic threshold employed. However, the proposed method demonstrated a superior robustness with respect to the MIMU location. Overall, the proposed method appears to be a good starting point for the definition of a more stable and robust method for U-turn detection and characterization from signals recorded from MIMUs near the ankles

Sardinian Folk Dance for Individuals with Parkinson's Disease: A Randomized Controlled Pilot Trial

Objectives: Among different exercise models proposed for individuals with Parkinson's disease (IwPD), the popularity of traditional forms of dance is increasing. The aim of this study was to evaluate the effects of Sardinian folk dance (Ballu Sardu, BS) on functional performance and motor and nonmotor symptoms in IwPD. Design: Single-blind, randomized controlled pilot trial. Settings: Outpatient health clinic. Subjects and interventions: Twenty IwPD (13M, 7F; 67.4 ± 6.1 years) were randomly assigned to BS (n = 10) or usual care (n = 10). The dance program consisted of two sessions/week, 90-min/class, for 12 weeks. Outcome measures: Motor and nonmotor symptoms, as well as functional performance, were evaluated using different questionnaires and tests such as the Unified Parkinson's Disease Rating Scale Part-III (UPDRS-III), 6-min walking test (6MWT), Berg Balance Scale (BBS), Timed Up-and-Go (TUG) test, Five Times Sit-to-Stand Test (FTSST), Back Scratch Test (BST), Sit-and-Reach Test (SRT), instrumented gait analysis, Parkinson's Disease Fatigue Scale (PFS-16), Beck Depression Inventory, Starkstein Apathy Scale (SAS), and Montreal Cognitive Assessment (MOCA) scale. Results: Repeated-measures analysis of variance revealed significant Time × Group interactions for UPDRS-III and functional variables such as the 6MWT, BBS, FTSST, TUG (all, p < 0.001), BST (p = 0.04), and gait analysis parameters (stride length, p = 0.031; gait speed, p = 0.049; and gait fatigue index (GFI), p = 0.005). For nonmotor symptoms, significant Time × Group interactions for depression (p < 0.001), apathy (p = 0.016), and MOCA scores (p = 0.012) were observed. Of note, for GFI and SAS, the BS group only showed a trend toward improvement, while the condition of the controls worsened significantly. No between-group differences were observed for SRT and PFS-16. Conclusions: BS is an enjoyable activity, which has been proved to be superior to usual care alone in inducing changes in different motor and nonmotor symptoms associated with PD. Results show that BS can be considered a safe tool for contrasting impairments observed in IwPD due to the intrinsic nature of the neurodegenerative disease