Effects of perturbation magnitude on dynamic stability when walking in destabilizing environments

Sinitksi, Emily H.; Terry, Kevin; Wilken, Jason M.; Dingwell, Jonathan B.

doi:10.1016/j.jbiomech.2012.05.039

Cited by 41 publications

(45 citation statements)

References 40 publications

(68 reference statements)

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“…3B, Table 3) dynamic instability of the ML COM movements of all body segments. This indicates that visual and walking surface perturbations significantly affect whole body stability, as previously shown (McAndrew et al, 2011; Sinitski et al, 2012; Terry et al, 2012). Importantly, the present findings extend these prior results to other body segments.…”

Section: Discussionsupporting

confidence: 82%

“…Hip and knee flexion increases to lower center of mass, and ankle dorsi flexion and hip and knee flexion increase during swing phase to increase toe clearance (Gates et al, 2012). When exposed to side to side perturbations of the visual field or walking surface, healthy young adults exhibited greater dynamic instability (McAndrew et al, 2011; Sinitski et al, 2012) and increased stepping and trunk movement variability (McAndrew et al, 2010). These became more pronounced with larger perturbation amplitudes (Sinitksi et al, 2012; Terry et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Dynamic stability of superior vs. inferior body segments in individuals with transtibial amputation walking in destabilizing environments

Beurskens

Wilken

Dingwell

2014

Journal of Biomechanics

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Interestingly, young and highly active people with lower limb amputation appear to maintain a similar trunk and upper body stability during walking as able bodied individuals. Understanding the mechanisms underlying how this stability is achieved after lower leg amputation is important to improve training regimens for improving walking function in these patients. This study quantified how superior (i.e., head, trunk, and pelvis) and inferior (i.e., thigh, shank, and feet) segments of the body respond to continuous visual or mechanical perturbations during walking. Nine persons with transtibial amputation (TTA) and 12 able bodied controls (AB) walked on a 2m × 3m treadmill in a Computer Assisted Rehabilitation Environment (CAREN). Subjects were perturbed by continuous pseudo random mediolateral movements of either the treadmill platform or the visual scene. TTA maintained a similar local and orbital stability in their superior body segments as AB throughout both perturbation types. However, for their inferior body segments, TTA subjects exhibited greater dynamic instability during perturbed walking. In TTA subjects, these increases in instability were even more pronounced in their prosthetic limb compared to their intact leg. These findings demonstrate that persons with unilateral lower leg amputation maintain upper body stability in spite of increased dynamic instability in their impaired lower leg. Thus, transtibial amputation does significantly impair sensorimotor function, leading to substantially altered dynamic movements of their lower limb segments. However, otherwise relatively healthy patients with unilateral transtibial amputation appear to retain sufficient remaining sensorimotor function in their proximal and contralateral limbs to adequately compensate for their impairment.

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Section: Discussionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Dynamic stability of superior vs. inferior body segments in individuals with transtibial amputation walking in destabilizing environments

Beurskens

Wilken

Dingwell

2014

Journal of Biomechanics

Self Cite

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“…Short-term LDE of trunk motion and the variability of MOS and step measures detect the effects of stroke on walking stability. Although these stability measures can directly reflect the increased instability resulting from experimentally induced perturbations [13,15,16], it is unclear to what extent these measures are related to actual falls. Thus, it is necessary to validate these stability measures [14] before applying them to detect potential fallers clinically.…”

Section: Discussionmentioning

confidence: 99%

“…It is unknown if the sensitivity of locomotor system to small perturbations will predict its capacity to resist all perturbations without falling [14]. However, these measures that quantify responses to small perturbations can directly reflect the increased instability of human walking resulting from larger perturbations [13,15,16]. The amplitude of short-term LDE and maxFM increased substantially and responded specifically to different types of external perturbations [13,16].…”

Section: Introductionmentioning

confidence: 99%

“…However, these measures that quantify responses to small perturbations can directly reflect the increased instability of human walking resulting from larger perturbations [13,15,16]. The amplitude of short-term LDE and maxFM increased substantially and responded specifically to different types of external perturbations [13,16]. In addition, short-term LDE was associated with fall history in elders in a retrospective study [17].…”

Section: Introductionmentioning

confidence: 99%

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Dynamic instability during post-stroke hemiparetic walking

et al. 2014

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Falls and fall-related injuries cause extremely costly and potentially fatal health problems in people post-stroke. However, there is no global indicator of walking instability for detecting which individuals will have increased risk of falls. The purposes of this study were to directly quantify walking stability in stroke survivors and neurologically intact controls and to determine which stability measures would reveal the changes in walking stability following stroke. This study thus provided an initial step to establish objective measures for identifying potential fallers. Nine post-stroke individuals and nine controls walked on a treadmill at four different speeds. We computed short-term local divergence exponent (LDE) and maximum Floquet multiplier (maxFM) of the trunk motion, average and variability of dynamic margins of stability (MOS) and step spatiotemporal measures. Post-stroke individuals demonstrated larger short-term LDE (p = 0.002) and maxFM (p = 0.041) in the mediolateral (ML) direction compared to the controls but remained orbitally stable (maxFM < 1). In addition, post-stroke individuals walked with greater average step width (p = 0.003) but similar average ML MOS (p = 0.154) compared to the controls. Post-stroke individuals also exhibited greater variability in all MOS and step measures (all p < 0.005). Our findings indicate that post-stroke individuals walked with greater local and orbital instability and gait variability than neurologically intact controls. The results suggest that short-term LDE of ML trunk motion and the variability of MOS and step spatiotemporal measures detect the changes in walking stability associated with stroke. These stability measures may have the potential for identifying those post-stroke individuals at increased risk of falls.

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Visual control of trunk translation and orientation during locomotion

et al. 2014

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Previous studies have suggested distinct control of gait characteristics in the anterior–posterior (AP) and medial–lateral (ML) directions in response to visual input. Responses were larger to a ML visual stimulus, suggesting that vision plays a larger role in stabilizing gait in the ML direction. Here, we investigated responses of the trunk during locomotion to determine whether a similar direction dependence is observed. We hypothesized that translation of the trunk would show a similar ML dependence on vision, but that angular deviations of the trunk would show equivalent responses in all directions. Subjects stood or walked on a treadmill at 5 km/h while viewing a virtual wall of white triangles that moved in either the AP or ML direction according to a broadband input stimulus. Frequency response functions between the visual scene motion and trunk kinematics revealed that trunk translation gain was larger across all frequencies during walking compared with standing. Trunk orientation responses were not different from standing at very low frequencies; however, at high frequencies, trunk orientation gain was much higher during walking. Larger gains in response to ML visual scene motion were found for all trunk movements. Higher gains in the ML direction while walking suggest that visual feedback may contribute more to the stability of trunk movements in the ML direction. Vision modified trunk movement behavior on both a slow (translation) and fast (orientation) time scale suggesting a priority for minimizing angular deviations of the trunk. Overall, trunk responses to visual input were consistent with the theme that control of locomotion requires higher-level sensory input to maintain stability in the ML direction.

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Effects of perturbation magnitude on dynamic stability when walking in destabilizing environments

Cited by 41 publications

References 40 publications

Dynamic stability of superior vs. inferior body segments in individuals with transtibial amputation walking in destabilizing environments

Dynamic stability of superior vs. inferior body segments in individuals with transtibial amputation walking in destabilizing environments

Dynamic instability during post-stroke hemiparetic walking

Visual control of trunk translation and orientation during locomotion

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