The development and concurrent validity of a real-time algorithm for temporal gait analysis using inertial measurement units
Section snippets
Background
Gait analysis provides information related to diagnosing pathology (Andriacchi et al., 1977), fall risk (Maki, 1997) and mortality (Fritz et al., 2009). Advances in technology, which include optical motion capture systems, instrumented walkways, and forceplates, have become gold standards (Najafi, 2011), but their use is constrained by cost, time, and physical space. Body worn inertial measurement units (IMU) have arisen as a low-cost, portable alternative to these traditional systems and holds
Description of shank angular velocity waveform
Gyroscope-derived shank angular velocity during gait has a well-defined, quasi-periodic waveform that consists of a region of positive angular velocity corresponding to advancing the shank relative to the knee and a region of negative angular velocity corresponding to advancing the shank relative to the ground (Fig. 1). In the middle of the negative angular velocity region exists a maximum corresponding to MidStance (MSt) (Hanlon and Anderson, 2009) and in the middle of the positive angular
Subjects and data acquisition
Eleven subjects participated in the study (5 females) with a mean age of 32.4 ± 6.9 yrs (20.3–45.9 yrs), height of 173.4 ± 11.4 cm, and weight of 75.9 ± 23.2 kg. The IMU system captured roughly 6 times as many measurements of GCT and SLS and 3 times as many measurements of DLS as the MatScan (Table 1).
Temporal gait parameters
CoV was calculated for each temporal gait parameter across subjects under the SSWS condition (Table 2). The Wilcoxon sign-ranked test found no significant difference between NZC and the criterion measure
Discussion
The results show that while both NZC and LP yield accurate and precise estimates of GCT, only NZC accurately estimates SLS and DLS time intervals. NZC identifies HS concurrently with LP, validating our earlier hypothesis that mean difference in SLS and DLS times from the instrumented walkway reflects the accuracy of TO event detection. Using Bland-Altman results and Eq. (2), LP identifies TO 170 ms early, while NZC identifies TO only 27 ms (∼1 sample) late, demonstrating that the zero-crossing
Conclusion
The NZC method, although an indirect measure of temporal gait parameters, has been shown to be concurrently valid with the direct measure instrumented walkway. NZC produces stable and repeatable measures of gait event landmarks that yield accurate and precise estimates of gait phase intervals that can be acquired in the subject’s everyday life. The ability of NZC to accurately detect GCT variability and DLS interval times allows for clinicians to utilize an IMU system for gait assessment.
Conflict of interest
All authors declare that there is no proprietary, financial, professional or other personal interest of any nature or kind in any product, service or company that could be construed as influencing the position presented in this manuscript.
Acknowledgments
The Authors would like to thank the Joint Incentive Fund for supporting this work under the DoD-VA Mobile Device Outcomes-based Rehabilitation Program.
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2021, Medical Engineering and PhysicsCitation Excerpt :In Fig. 4, the results of the different methods for IC and TC detection are presented: the detection of zero-crossings (Shank0) and minima (ShankMin), in the shank and foot (Foot0 and FootMin) angular velocities, and the minima detection in the foot acceleration signals (FootXMin, FootZMin). During walking, comparable signals referred to in the literature [6,11,12,16,18,23] were measured and the previously described characteristics (Table 1) can be determined. Small differences of a few milliseconds in the evaluated time points for IC and TC between the methods were visible (Fig. 4).
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