Elsevier

Journal of Biomechanics

Volume 79, 5 October 2018, Pages 218-222
Journal of Biomechanics

Short communication
Validation of gait event detection by centre of pressure during target stepping in healthy and paretic gait

https://doi.org/10.1016/j.jbiomech.2018.07.039Get rights and content

Abstract

Background

Target-stepping paradigms are increasingly used to assess and train gait adaptability. Accurate gait-event detection (GED) is key to locating targets relative to the ongoing step cycle as well as measuring foot-placement error. In the current literature GED is either based on kinematics or centre of pressure (CoP), and both have been previously validated with young healthy individuals. However, CoP based GED has not been validated for stroke survivors who demonstrate altered CoP pattern.

Methods

Young healthy adults and individuals affected by stroke stepped to targets on a treadmill, while gait events were measured using three detection methods; verticies of CoP cyclograms, and two kinematic criteria, (1) vertical velocity and position and of the heel marker, (2) anterior velocity and position of the heel and toe marker, were used. The percentage of unmatched gait events was used to determine the success of the GED method. The difference between CoP and kinematic GED methods were tested with two one sample (two-tailed) t-tests against a reference value of zero. Differences between group and paretic and non-paretic leg were tested with a repeated measures ANOVA.

Results

The kinematic method based on vertical velocity only detected about 80% of foot contact events on the paretic side in stroke survivors while the method on anterior velocity was more successful in both young healthy adults as stroke survivors (3% young healthy and 7% stroke survivors unmatched). Both kinematic methods detected gait events significantly earlier than CoP GED (p < 0.001) except for foot contact in stroke survivors based on the vertical velocity.

Conclusions

CoP GED may be more appropriate for gait analyses of SS than kinematic methods; even when walking and varying steps.

Introduction

Force instrumented treadmills facilitate online kinetic measurement of a high volume of steps in a small space with the safety of support harnesses (Merholz and Elsner, 2014) and, combined with visual projection, can allow practice of altering walking in response to cues (e.g. stepping to targets, over or around obstacles (Heeren et al., 2013). For these reasons use of instrumented treadmills for rehabilitation and clinical assessment is increasing (Bank et al., 2011, Duysens et al., 2012, Heeren et al., 2013, Hollands et al., 2014, Hollands et al., 2013, Mazaheri et al., 2015, Mazaheri et al., 2014, Peper et al., 2015, Timmermans et al., 2016, van Ooijen et al., 2015, Weerdesteyn et al., 2006).

Single uniaxial force instrumentation of the treadmill belt affords centre of pressure (CoP) gait event detection (GED) as a proxy for gold standard kinetic (dual, multi-axial, force-plates) or kinematic GED. CoP GED has been shown to correspond well with kinematic GED during steady-state treadmill walking in young healthy adults (Roerdink et al., 2008). However, it is not known whether CoP GED corresponds with kinematic GED when steps are altered in response to environmental cues, or when alterations in CoP trajectories occur due to pathology (i.e. stroke (Wong et al 2004)).

To support valid gait assessment in the context of growing treadmill use in clinical assessment, this study aimed to determine if there are differences in CoP and kinematic GED in young healthy (YH) and stroke survivors (SS) during treadmill walking. We compare GED methods in the walking condition of varying steps; the context in which they are increasingly being applied. Specific questions are:

  • (1)

    Are there significant differences between methods within groups?

  • (2)

    Are differences between methods greater in SS than YH (and according to paretic and non-paretic limbs)?

Section snippets

Participants

YH, aged 18–35 years, were recruited by poster advertisement across the University. SS were recruited from community stroke support and exercise groups in Greater Manchester. Participants were included if they could walk ten-metres within 30 s, had no visual impairments preventing sight of stepping targets, and no co-morbidities affecting walking.

The University of Salford, College of Health and Social Care Research Ethics Committee approved the study, and all participants provided written

Results

A total of 7 YH and 13 SS participated (demographics see Table 1). No abnormalities in cyclograms which would have prevented CoP GEDs were found on visual inspection of individual participant data (Fig. 2).

Discussion

Traditionally, GED is applied during steady state walking on a treadmill/over-ground (Roerdink et al., 2008, Roerdink et al., 2007). However, owing to the importance of adapting steps in response to environmental cues and the increasing use of instrumented treadmills to train and assess gait in this context, we robustly compared the performance of GED methods during step alterations (longer, shorter, and narrowing) for both YH and SS.

We found that, for SS, detecting FC using VFC and FO using

Conclusion

This study showed that CoP based GED agreed within 100 ms with kinematic algorithms suggested for use with SS walking on a treadmill. The differences in GED methods reflect the differences between movement (kinematics) vs weight transfer (kinetics) and suggest CoP GED may be more appropriate for gait analyses of SS than kinematic methods; even when walking and varying steps.

Conflict of interest statement

We confirm that there is no conflict of interest with the current submission and a full review and understanding of copyright guidelines has been completed.

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