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Stair negotiation has been identified by older adults as one of the most challenging locomotor tasks, one that is associated with a high risk for falls and serious injury. Currently lacking is a comprehensive understanding of the lower limb during stair negotiation in an older adult population. It has been identified that more research is needed to determine key determinants of difficulty and safety on stairs. The objective of this thesis was to investigate lower limb kinematics and kinetics during stair negotiation and evaluate the impact of handrail use on stair ambulation in young adults, older adults, and older adults with a fear of falling (FOF). The four studies that make up this dissertation provide a detailed picture of the lower limb joint kinematics and kinetics during stair ambulation, as well as provide insight into the role of handrail use and FOF in performance of stair negotiation. Specifically, in the first study principal component analysis (PCA) was used, of the scores generated from the PCA models four principal component (PC) scores were identified that could be used to correctly classify 95% of young and older adults. The second study provided a comprehensive data set of lower limb joint kinematics and kinetics during stair negotiation. The third study identified comparable centre of pressure velocities (VCOP) between young adults and older adults during stair negotiation with and without a handrail. Whereas older adults with FOF demonstrated reduced VCOP during stair negotiation without a handrail and further reduced VCOP when using the handrail. Furthermore, no significant difference in lower limb moments during stair negotiation with and without a handrail were found in older adults, as was similar for older adults with FOF. However, a gait assessment revealed that older adults with FOF demonstrated differences from ‘normal’ gait patterns during stair negotiation with and without a handrail. These studies provide a comprehensive normative dataset of the lower limb joint kinematics and kinetics during stair negotiation, as well as provide insight into the role of handrail use and fear of falling in performance of stair ambulation. It is important to appreciate the nature and extent of normal age-related adaption and compensatory strategies to identify unique patterns of movement due to the superimposition of pathology. / Thesis (Ph.D, Kinesiology & Health Studies) -- Queen's University, 2010-09-24 14:50:22.242

Yes / Older people have an increased risk of falling during locomotion, with falls on stairs being particularly common and dangerous. Step going (i.e., the horizontal distance between two consecutive step edges) defines the base of support available for foot placement on stairs, as with smaller going, the user's ability to balance on the steps may become problematic. Here we quantified how stair negotiation in older participants changes between four goings (175, 225, 275, and 325 mm) and compared stair negotiation with and without a walking approach. Twenty-one younger (29 ± 6 years) and 20 older (74 ± 4 years) participants negotiated a 7-step experimental stair. Motion capture and step-embedded force platform data were collected. Handrail use was also monitored. From the motion capture data, body velocity, trunk orientation, foot clearance and foot overhang were quantified. For all participants, as stair going decreased, gait velocity (ascent pA = 0.033, descent pD = 0.003) and horizontal step clearance decreased (pA = 0.001), while trunk rotation (pD = 0.002) and foot overhang increased (pA,D < 0.001). Compared to the younger group, older participants used the handrail more, were slower across all conditions (pA < 0.001, pD = 0.001) and their foot clearance tended to be smaller. With a walking approach, the older group (Group x Start interaction) showed a larger trunk rotation (pA = 0.011, pD = 0.015), and smaller lead foot horizontal (pA = 0.046) and vertical clearances (pD = 0.039) compared to the younger group. A regression analysis to determine the predictors of foot clearance and amount of overhang showed that physical activity was a common predictor for both age groups. In addition, for the older group, medications and fear of falling were found to predict stair performance for most goings, while sway during single-legged standing was the most common predictor for the younger group. Older participants adapted to smaller goings by using the handrails and reducing gait velocity. The predictors of performance suggest that motor and fall risk assessment is complex and multifactorial. The results shown here are consistent with the recommendation that larger going and pausing before negotiating stairs may improve stair safety, especially for older users. / This study was supported by the New Dynamics of Aging (RES-356-25-0037).

Impairment of stereoacuity is common in the elderly population and is found to be a risk factor for falls. The purpose of these experiments was to extend knowledge regarding impairment of binocular vision and adaptive gait. Firstly using a 3D motion analysis system to measure how impairment of stereopsis affected adaptive gait during a negotiation of a step, secondly by determining which clinical stereotest was the most reliable for measuring stereoacuity in elderly subjects and finally investigating how manipulating the perceived height of a step in both binocular and monocular conditions affected negotiation of a step. In conditions of impaired stereopsis induced by acutely presented monocular blur, both young and elderly subjects adopted a safety strategy of increasing toe clearance of the step edge, even at low levels of monocular blur (+0.50DS) and the effect was greater when the dominant eye was blurred. The same adaptation was not found for individuals with chronic monocular blur, where vertical toe clearance did not change but variability of toe clearance increased compared to full binocular correction. Findings indicate stereopsis is important for accurately judging the height of a step, and offers support to epidemiological findings that impaired stereoacuity is a risk for falls. Poor agreement was found between clinical stereotests. The Frisby test was found to have the best repeatability. Finally, a visual illusion that caused a step to be perceived as taller led to increased toe elevation. This demonstrates a potential way of increasing toe clearance when stepping up and hence increase safety on stairs. / The Study data files are unavailable online.

Impairment of stereoacuity is common in the elderly population and is found to be a risk factor for falls. The purpose of these experiments was to extend knowledge regarding impairment of binocular vision and adaptive gait. Firstly using a 3D motion analysis system to measure how impairment of stereopsis affected adaptive gait during a negotiation of a step, secondly by determining which clinical stereotest was the most reliable for measuring stereoacuity in elderly subjects and finally investigating how manipulating the perceived height of a step in both binocular and monocular conditions affected negotiation of a step. In conditions of impaired stereopsis induced by acutely presented monocular blur, both young and elderly subjects adopted a safety strategy of increasing toe clearance of the step edge, even at low levels of monocular blur (+0.50DS) and the effect was greater when the dominant eye was blurred. The same adaptation was not found for individuals with chronic monocular blur, where vertical toe clearance did not change but variability of toe clearance increased compared to full binocular correction. Findings indicate stereopsis is important for accurately judging the height of a step, and offers support to epidemiological findings that impaired stereoacuity is a risk for falls. Poor agreement was found between clinical stereotests. The Frisby test was found to have the best repeatability. Finally, a visual illusion that caused a step to be perceived as taller led to increased toe elevation. This demonstrates a potential way of increasing toe clearance when stepping up and hence increase safety on stairs.

Intraocular lenses (IOLs) provide distance and near refraction and are becoming the standard for cataract surgery. Multifocal glasses increase the variability of toe clearance in older adults navigating stairs and increase fall risk; however, little is known about the biomechanics of stair navigation in individuals with multifocal IOLs. This study compared clearance while ascending and descending stairs in individuals with monofocal versus multifocal IOLs. Eight participants with multifocal IOLs (4 men, 4 women; mean age = 66.5 yr, standard deviation [SD] = 6.26) and fifteen male participants with monofocal IOLs (mean age = 69.9 yr, SD = 6.9) underwent vision and mobility testing. Motion analysis recorded kinematic and custom software-calculated clearances in three-dimensional space. No significant differences were found between groups on minimum clearance or variability. Clearance differed for ascending versus descending stairs: the first step onto the stair had the greatest toe clearance during ascent, whereas the final step to the floor had the greatest heel clearance during descent. This preliminary study indicates that multifocal IOLs have similar biomechanic characteristics to monofocal IOLs. Given that step characteristics are related to fall risk, we can speculate that multifocal IOLs carry no additional fall risk.