Does footwear type impact the number of steps required to reach gait steady state?: An innovative look at the impact of foot orthoses on gait initiation
Introduction
The gait initiation phase is the transient period between upright posture and steady state gait [1]. Walking at a constant mean velocity is considered ‘steady state’ activity where the body is neither accelerating nor decelerating (i.e. relatively low inter-cycle speed variability). Various aspects of steady state walking have been analyzed extensively in an attempt to better understand both healthy and pathological gait [2], [3]. However, limited focus has been placed on the other two components of human locomotion: gait initiation and stopping. The dynamic processes of gait initiation and stopping are much more complex since the human body needs to accelerate and decelerate, respectively, often in a limited amount of time. As a result, the skills necessary to maintain stability, weight transfer, foot clearance, etc., become more critical during these transition phases than during the steady state conditions [1], [4], [5], [6]. Such requirements become even more significant in patients with neurological disorders, lower limb complications, and in older adults, where there are inherent difficulties with postural stability and gait [1], [7], [8].
Both sensory input and muscular actions are necessary to create the postural and dynamic conditions for progression and reaching a given gait velocity. Recently, it has been suggested that foot orthoses may act as proprioceptive stimulators or gait perturbation devices [9], [10]. This theory has lead to preliminary investigation into the role of foot orthoses in postural control and balance [11], [12], [13]. Despite the fact that an appropriate equilibrium is of key importance in a faster gait initiation, little attention has been paid to examining the impact of using foot orthoses to improve gait initiation.
One of the major obstacles in assessing the impact of foot orthoses on gait initiation is measuring natural locomotion. In the gait lab, there are apparatus limitations, subject targeting, and subsequent methodological issues that constrain this assessment. Camera-based motion analysis systems [14], [15], [16], [17] demonstrate high accuracy for assessing locomotion, but the number of consecutive strides that can be measured is limited. Instrumented treadmills are also not well suited for this purpose due to the constraints on the base of gait as well as the frictional and inertial changes they impart on the gait initiation process. Instrumented mats also have length limitations that make it difficult to accurately identify the acceleration and deceleration phases of walking. A larger number of consecutive strides should be measured to assess inter-cycle gait speed variability, an important variable for reaching steady state walking. Motion capture with body-worn sensors offers an appropriate alternative for assessing human locomotion continuously over long periods of time outside of a gait laboratory and in a free condition [15], [16]. A range of body-attached sensors including electromechanical switches, goniometers, accelerometers, gyroscopes, pedometers, and actometers, have been used in several clinical studies to capture and analyze human movement performance in free-living conditions [15], [17], [18], [19].
In a recent work [16], we found that when laboratory constraints are removed, subjects frequently change their walking patterns. In this prior study, elderly subjects were found to walk significantly faster outdoors despite excellent test-retest reliability (ICC > 0.9) for both measurements inside and outside a gait laboratory [16]. These results seem to indicate that at least some gait parameters assessed inside of a gait laboratory environment may not replicate the subject's gait outdoors where they are most likely to wear their prescribed footwear.
The purpose of this new research was to assess spatio-temporal parameters of gait initiation outside of a gait laboratory. Our objective was twofold: (1) examine whether the type of footwear may impact the number of steps required to reach steady state walking, (2) assess the impact of foot orthoses on spatio-temporal parameters of gait during both steady state and gait initiation phases. It was hypothesized that foot orthoses may improve the dynamics necessary to induce the appropriate equilibrium for reaching a given gait velocity.
Section snippets
Subjects
Eligible subjects were recruited from students and employees at the Rosalind Franklin University of Medicine and Science (North Chicago, IL, USA) by verbal communication. Interested individuals were scheduled a time to come to the Human Performance Laboratory, provide informed consent, and consequently participate in the trial. Fifteen healthy subjects (6 female, 9 male) were recruited with an average age 24.2 ± 1.78 years, average height 173.77 ± 14.02 cm, and average weight 76.44 ± 17.5 kg. All
The impact of foot orthoses on gait initiation
The results demonstrated that by wearing foot orthoses with their habitual footwear, subjects needed significantly fewer steps to reach steady state walking (Fig. 3A) compared to a barefoot condition (−49%, p < 0.05) as well as compared to shod with their standard footwear alone (−34%, p < 0.05). The average number of steps for reaching gait steady state was 3.5 ± 2.0 (95% CI = [1.25,8] steps, minimum = 1 step, maximum = 8 steps) wearing foot orthoses, and was increased to 4.66 ± 1.58 (95% CI = [2.25,8.25]
The impact of foot orthoses on gait initiation
We believe this study is the first quantification of gait initiation parameters across three footwear conditions. We found that wearing habitual shoes with prefabricated foot orthoses enabled subjects to reach steady state walking in 3.5 steps compared to 5.2 steps for the barefoot condition and 4.7 steps for the habitual shoes alone condition. These results put into context other studies that have described the minimum steps necessary to achieve stable estimates of plantar pressure. McPoil et
Conclusion
In conclusion, under single task walking conditions, the shod with foot orthoses condition resulted in significantly fewer number of steps needed to reach steady state walking. Considering that many falls in elderly people occur during initiating walking [18], [34], the developed algorithm for discriminating between gait initiation and gait steady state, may represent a new potential target for interventions designed to mitigate the risk of falling and/or improve postural stability.
Conflict of interest
None declared.
Acknowledgements
This study was supported by Award Number T35DK074390 from the National Institute of Diabetes And Digestive And Kidney Diseases. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Diabetes And Digestive And Kidney Diseases or the National Institutes of Health.
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