Falls in elderly are the leading cause of injury and therefore considered a major health problem in our ageing society [1]. A fall is the result of an inadequate restoration of balance when it is compromised. The use of external perturbations to evoke loss of balance in a standardized and safe manner is an increasingly popular approach to measur e dynamic stability, offering opp ortunities for fall prevention research [2]. Although a perturbation - paradigm is promising, little is known about the type of perturbation that is most informative to quantify dynamic stability. Therefore, the first aim of this feasibility study was to evaluate whether mechanical, visual and auditory perturbations can be used to affect dynamic stability. The second aim was to evaluate whether we can distinguish between younger and older adults using the response to external perturbations.
Falls in elderly are the leading cause of injury. A fall can result in serious injuries leading to loss of independence, hospitalization, increased medical costs, and a greater economic burden. Therefore, the development and implementation of effective strategies to prevent falls in elderly is a vital challenge for the health society.
During gait the centre of mass (COM) should be maintained relative to the base of support for optimal efficiency of movement, and reduced risk of falling. The ability to control the COM position is challenged for every step, and is therefore an important tool in clinical practice to predict dynamic stability. To ensure accuracy and precision of COM estimation, motion analysis equipment and full body (FB) tracking is required. Difficulty implementing this due to time and expertise limitations causes clinicians to favour the pelvic model (P), assuming the COM can be represented by the centre point of the pelvis. This may trade accuracy and precision for clinical applicability. The aim of this study was to investigate COM representation during unperturbed and perturbed gait using a reduced kinematic model.
While falls among older adults are considered a major health problem, the sensitivity of conventional fall risk assessments to identify individuals is poor [1]. Among the main risk factors for falls are balance and gait impairments [2]. The ability to resist or recover from gait perturbations requires fast and accurate responses and might discriminate between fallers and non-fallers. We therefore investigated the ability to discriminate between older adults with and without history of falls using perturbation based gait assessment.
Prosthetic gait is often asymmetric in step length, but the direction of this asymmetry varies inconsistently across amputees. This situation is akin to that seen in stroke patients, where step-length asymmetry has been shown to be the additive result of asymmetries in trunk progression and asymmetries in forward foot placement relative to the trunk. The present study examined the validity of this notion in three trans-tibial and seven trans-femoral amputees wearing a unilateral prosthesis while walking over a walkway at a comfortable and slower-than-comfortable speed. The latter manipulation was added to examine the expectation that the magnitude of the trunk-progression asymmetry - attributable to a weaker propulsion generating capacity on the prosthetic side - would be smaller when walking slower because of the diminished propulsion demands. Step length, forward foot placement relative to the trunk, and trunk progression of prosthetic and non-prosthetic steps, as well as asymmetries therein, were quantified. The direction of step-length and forward foot placement asymmetries varied inconsistently across (but consistently within) participants. As expected, step-length asymmetry depended on the combination of asymmetries in forward foot placement and trunk progression, with a smaller contribution of trunk-progression asymmetry at slow speed. These results extend our previous finding for hemiplegic patients that an analysis of gait asymmetry in terms of step length alone is flawed to prosthetic gait, implying that knowledge of asymmetries in trunk progression and forward foot placement relative to the trunk is required to help elucidate the contribution of underlying impairments (viz. propulsion generating capacity) and adopted compensations on prosthetic gait asymmetry.
Perturbation-based gait assessment has been used to quantify gait stability in older adults. However, knowledge on which perturbation type is most suitable to identify poor gait stability is lacking. We evaluated the effects of ipsi- and contra-lateral sway, belt acceleration and deceleration, and visual and auditory perturbations on medio-lateral (ML) and anterior-posterior (AP) margins of stability (MoS) in young and older adults. We aimed to evaluate (1) which perturbation type disturbed the gait pattern substantially, (2) how participants recovered, and (3) whether recovery responses could discriminate between young and older adults. Nine young (25.1 ± 3.4 years) and nine older (70.1 ± 7.6 years) adults walked on the CAREN Extended (Motek BV, The Netherlands). The perturbation effect was quantified by deviation in MoS over six post-perturbation steps compared to baseline walking. Contra-lateral sway and deceleration perturbations resulted in the largest ML (1.9–4 times larger than other types) and AP (1.6–5.6 times larger than other types) perturbation effects, respectively. After both perturbation types, participants increased MoS by taking wider, shorter, and faster steps. No differences between young and older adults were found. We suggest to evaluate the potential of using contra-lateral sway and deceleration perturbations for fall risk identification by including both healthy and frail older adults.
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