Validation of a step detection algorithm during straight walking and turning in Patients with Parkinson's disease and older adults using an inertial measurement unit at the lower back

Minh H. Pham*, Morad Elshehabi, Linda Haertner, Silvia Del Din, Karin Srulijes, Tanja Heger, Matthis Synofzik, Markus A. Hobert, Gert S. Faber, Clint Hansen, Dina Salkovic, Joaquim J. Ferreira, Daniela Berg, Álvaro Sanchez-Ferro, Jaap H. van Dieën, Clemens Becker, Lynn Rochester, Gerhard Schmidt, Walter Maetzler

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

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Introduction: Inertial measurement units (IMUs) positioned on various body locations allow detailed gait analysis even under unconstrained conditions. From a medical perspective, the assessment of vulnerable populations is of particular relevance, especially in the daily-life environment. Gait analysis algorithms need thorough validation, as many chronic diseases show specific and even unique gait patterns. The aim of this study was therefore to validate an acceleration-based step detection algorithm for patients with Parkinson's disease (PD) and older adults in both a lab-based and home-like environment. Methods: In this prospective observational study, data were captured from a single 6-degrees of freedom IMU (APDM) (3DOF accelerometer and 3DOF gyroscope) worn on the lower back. Detection of heel strike (HS) and toe off (TO) on a treadmill was validated against an optoelectronic system (Vicon) (11 PD patients and 12 older adults). A second independent validation study in the home-like environment was performed against video observation (20 PD patients and 12 older adults) and included step counting during turning and non-turning, defined with a previously published algorithm. Results: A continuous wavelet transform (cwt)-based algorithm was developed for step detection with very high agreement with the optoelectronic system. HS detection in PD patients/older adults, respectively, reached 99/99% accuracy. Similar results were obtained for TO (99/100%). In HS detection, Bland-Altman plots showed a mean difference of 0.002 s [95% confidence interval (CI) -0.09 to 0.10] between the algorithm and the optoelectronic system. The Bland-Altman plot for TO detection showed mean differences of 0.00 s (95% CI -0.12 to 0.12). In the home-like assessment, the algorithm for detection of occurrence of steps during turning reached 90% (PD patients)/90% (older adults) sensitivity, 83/88% specificity, and 88/89% accuracy. The detection of steps during non-turning phases reached 91/91% sensitivity, 90/90% specificity, and 91/91% accuracy. Conclusion: This cwt-based algorithm for step detection measured at the lower back is in high agreement with the optoelectronic system in both PD patients and older adults. This approach and algorithm thus could provide a valuable tool for future research on home-based gait analysis in these vulnerable cohorts.

Original languageEnglish
Article number457
JournalFrontiers in Neurology
Issue numberSEP
Publication statusPublished - 4 Sept 2017


The study was supported by the EU project FAIR-PARK II, funded under the Horizon2020 Program of the European commission (grant no. 633190, PHC13 2014–2015; NCT02655315) and by Lundbeck. The funding sources did not have any role in conception and design of the study, acquisition, analysis, and interpretation of data, and in writing of the manuscript. The authors acknowledge financial support by Land Schleswig-Holstein within the funding program Open Access Publikationsfonds. SD and LR are supported by the Newcastle Biomedical Research Centre (BRC) and Unit (BRU) based at Newcastle upon Tyne and Newcastle University. They are also supported by the NIHR/ Wellcome Trust Clinical Research Facility (CRF) infrastructure at Newcastle upon Tyne Hospitals NHS Foundation Trust. KS and MS received financial support from the Forschungskolleg Geriatrie of the Robert Bosch Foundation, Stuttgart, Germany. All opinions are those of the authors and not the funders.

FundersFunder number
Forschungskolleg Geriatrie of the Robert Bosch Foundation
Horizon2020 Program of the European commissionPHC13 2014–2015, NCT02655315
Land Schleswig-Holstein
Wellcome Trust
Horizon 2020 Framework Programme633190
Manchester Biomedical Research Centre
National Institute for Health Research
Newcastle University
European Commission
NIHR Newcastle Biomedical Research Centre
H. Lundbeck A/S


    • Accelerometer
    • Gait Analysis
    • Home-Like Activities
    • Older Adults
    • Parkinson's Disease
    • Turning


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