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Investigating gait characteristics and dynamic stability during challenging walking

Madehkhaksar, Forough

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Abstract

Fall is a leading cause of injuries in older adults, which mostly occurs during walking and under a challenging condition. Examples of challenging conditions are an unexpected perturbed walking, stair walking, or walking while positional transitions. A better understanding of postural control to maintain balance during similar tasks can help in reducing the risk of fall. For this aim, one approach is to examine the effects of the challenged walking on gait stability. This dissertation consists of three studies focusing on postural responses under four different challenging circumstances including 1) walking while performing a manual and a cognitive secondary task, 2) stair walking at different inclinations (i.e. different levels of complexity), 3) sudden mechanically perturbed walking, and 4) gaze-shift walking. Firstly, the postural responses of healthy adults under the mentioned conditions were assessed. Secondly, different representative measures in order to quantify balance during perturbed walking were evaluated. Thirdly, the postural responses of young and old healthy adults during walking while gaze-shifting in terms of gait parameters and their variability were contrasted. The first study examined how secondary cognitive and manual tasks interfere with stair gait when a person concurrently performed tasks at different levels of complexity. Gait kinematic data and secondary task performance measures were obtained from fifteen healthy young males while ascending and descending a four-step staircase at three inclinations (17.7°, 29.4°, and 41.5°) as well as level walking. They performed a cognitive task, ‘backward digit recall’, a manual task, ‘carrying a cup of water’ and a combination of the two tasks. Gait performance and dynamic stability were assessed by gait speed and whole body center of mass (CoM) range of motion in the medial-lateral direction, respectively. No significant effect of the gait task on the cognitive task performance was observed. In contrast, stair walking adversely affected the performance of the manual task compared to level walking. Overall, more difficult postural and secondary tasks resulted in a decrease in gait speed and variation in CoM displacement within a normal range. Results suggest that CoM displacement and gait alterations might be adopted to enhance the stability, and optimize the secondary task performance while walking under challenging circumstances. The findings of this study are useful for balance and gait evaluation, and for future falls prediction. The second study examined changes in spatiotemporal gait and stability parameters in response to sudden mechanical perturbations in mediolateral (ML) and anterior-posterior (AP) direction during treadmill walking. Moreover, the most representative parameters to quantify postural recovery responses were evaluated. Ten healthy adults (mean=26.4, SD=4.1 years) walked on a treadmill that provided unexpected discrete ML and AP surface horizontal perturbations. Participants walked under no perturbation (normal walking), and under left, right, forward, and backward sudden mechanical perturbation conditions. Gait parameters were computed including stride length (SL), step width (SW), and cadence, as well as dynamic stability in AP- (MoS-AP) and ML- (MoS-ML) directions. Gait and stability parameters were quantified by means, variability, and extreme values. Overall, participants walked with a shorter stride length, a wider step width, and a higher cadence during perturbed walking, but despite this, the effect of perturbations on means of SW and MoS-ML was not statistically significant. These effects were found to be significantly greater when the perturbations were applied toward the ML-direction. Variabilities, as well as extremes of gait-related parameters, showed strong responses to the perturbations. The higher variability as a response to perturbations might be an indicator of instability and fall risk, on the same note, an adaptation strategy and beneficial to recover balance. Parameters identified in this study may represent useful indicators of locomotor adaptation to successfully compensate sudden mechanical perturbation during walking. The third study was aimed to determine the gait characteristics of healthy young and older adults during gaze-shifting while treadmill-walking. Eleven young (age: 25 ± 4.5 years, 3 females) and 13 older (age: 72 ± 3.9 years, 6 females) adults performed normal treadmill-walking (no visual-triggers) and then treadmill-walking while rapidly gaze-shifting to randomly presented visual-triggers. A multilevel linear regression model was used to assess changes in a set of gait parameters between subject groups and walking conditions: normal walking, one gait cycle before (Pre-Cycle), and after (Post-Cycle) each triggering during gaze-shift walking. Comparing Pre-Cycle to normal walking, young adults showed no instability-related changes in their gait but older adults showed a more cautious gait with shorter step length (Est. = -1.59cm [95% CI: -2.2cm; -0.9cm]), reduced step width (Est. = -0.8cm [95% CI: -1.1cm; -0.6cm]), increased step frequency (Est. = 0.04 1/s [95% CI: 0.03 1/s; 0.05 1/s]), decreased maximum toe clearance (Est. = -0.3cm [95% CI: -0.4cm; -0.2cm]), and 30% higher minimum toe clearance variability. During Post-Cycle compared to Pre-Cycle, direct effects of gaze-shifts on gait parameters were significant but rather small. This experiment shows an influence of gaze-shifts on gait in both groups, although, the effect is larger in the older which might therefore need more compensation compared to the young adults. Present insights may facilitate the development of specific training paradigms to improve the oculomotor-locomotor interaction.

Item Type: Dissertation
Supervisor: Schwenk, Dr. Michael
Date of thesis defense: 25 October 2018
Date Deposited: 22 Nov 2018 13:22
Date: 2018
Faculties / Institutes: The Faculty of Behavioural and Cultural Studies > Institut für Sport und Sportwissenschaft
Subjects: 500 Natural sciences and mathematics
610 Medical sciences Medicine
620 Engineering and allied operations
Controlled Keywords: Biomechanics, Human movement, Gait stability
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