Does local dynamic stability during unperturbed walking predict the response to balance perturbations? An examination across age and falls history

Qiao, Mu; Truong, Kinh; Franz, Jason R.

doi:10.1016/j.gaitpost.2018.03.011

Cited by 16 publications

(23 citation statements)

References 35 publications

(48 reference statements)

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“…Qiao et al ( 2018a ) investigated the effect of perturbed optical flow at joint level and found a general increase in variance that was larger in older compared to young adults. Surprisingly, Qiao et al ( 2018b ) found a negative relationship between local dynamic instability measures and responses to optical flow perturbations in young adults, and failed to establish any significant relationship in older adults. Kazanski et al ( 2020 ) used optical flow perturbations in a similar paradigm, but failed to find significantly increased visual dependency in the older adult group.…”

Section: Effects Of Aging On Balance Controlmentioning

confidence: 97%

“…One possible explanation is that age-related decreases in muscle strength compromise balance in older adults, and the CNS adapts the gains of the sensorimotor control loop to reestablish robustness. This might explain why Qiao et al (2018b) found that young people who responded more strongly to visual perturbations tended to have higher local dynamic stability measures. But this pattern did not show up in older adults in the same study, possibly because of the confounding influence of other age-related factors affecting postural stability.…”

Section: Increased Visual Dependencymentioning

confidence: 99%

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Interactions Between Different Age-Related Factors Affecting Balance Control in Walking

Reimann

Ramadan

Fettrow

et al. 2020

Front. Sports Act. Living

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Maintaining balance during walking is a continuous sensorimotor control problem. Throughout the movement, the central nervous system has to collect sensory data about the current state of the body in space, use this information to detect possible threats to balance and adapt the movement pattern to ensure stability. Failure of this sensorimotor loop can lead to dire consequences in the form of falls, injury and death. Such failures tend to become more prevalent as people get older. While research has established a number of factors associated with higher risk of falls, we know relatively little about age-related changes of the underlying sensorimotor control loop and how such changes are related to empirically established risk factors. This paper approaches the problem of age-related fall risk from a neural control perspective. We begin by summarizing recent empirical findings about the neural control laws mapping sensory input to motor output for balance control during walking. These findings were established in young, neurotypical study populations and establish a baseline of sensorimotor control of balance. We then review correlates for deteriorating balance control in older adults, of muscle weakness, slow walking, cognitive decline, and increased visual dependency. While empirical associations between these factors and fall risk have been established reasonably well, we know relatively little about the underlying causal relationships. Establishing such causal relationships is hard, because the different factors all co-vary with age and are difficult to isolate empirically. One option to analyze the role of an individual factor for balance control is to use computational models of walking comprising all levels of the sensorimotor control loop. We introduce one such model that generates walking movement patterns from a short list of spinal reflex modules with limited supraspinal modulation for balance. We show how this model can be used to simulate empirical studies, and how comparison between the model and empirical results can indicate gaps in our current understanding of balance control. We also show how different aspects of aging can be added to this model to study their effect on balance control in isolation.

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Section: Effects Of Aging On Balance Controlmentioning

confidence: 97%

Section: Increased Visual Dependencymentioning

confidence: 99%

Interactions Between Different Age-Related Factors Affecting Balance Control in Walking

Reimann

Ramadan

Fettrow

et al. 2020

Front. Sports Act. Living

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“…After acclimating to the treadmill, participants completed a series of 3-minute walking trials in randomized order. For each, subjects viewed a virtual hallway that was rear-projected onto a semi-circular, curved screen positioned in front of the treadmill [17,35,36]. The optical flow of the hallway in the direction of motion was prescribed to match the speed of the treadmill.…”

Section: Experimental Protocol and Instrumentationmentioning

confidence: 99%

“…In other trials, we applied to this baseline motion continuous optical flow perturbations to the foreground of the virtual hallway. To ensure that the visual perception of self-motion induced by these perturbations was complex and difficult to anticipate, they were created as the sum of 3 sine waves: one with an amplitude of 35 cm applied at 0.25Hz and two with amplitudes of 17.5 cm applied at 0.125 Hz and 0.442 Hz [17,35,36]. In one trial, optical flow was perturbed in the AP direction, thereby eliciting the visual perception that the hallway was accelerating and decelerating at random.…”

Section: Experimental Protocol and Instrumentationmentioning

confidence: 99%

Can optical flow perturbations detect walking balance impairment in people with multiple sclerosis?

et al. 2020

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People with multiple sclerosis (PwMS) who exhibit minimal to no disability are still over twice as likely to fall as the general population and many of these falls occur during walking. There is a need for more effective ways to detect preclinical walking balance deficits in PwMS. Therefore, the purpose of this study was to investigate the effects of optical flow perturbations applied using virtual reality on walking balance in PwMS compared to age-matched controls. We hypothesized that susceptibility to perturbations-especially those in the mediolateral direction-would be larger in PwMS compared to controls. Fourteen PwMS and fourteen age-matched controls walked on a treadmill while viewing a virtual hallway with and without optical flow perturbations in the mediolateral or anterior-posterior directions. We quantified foot placement kinematics, gait variability, lateral margin of stability and, in a separate session, performance on the standing sensory organization test (SOT). We found only modest differences between groups during normal, unperturbed walking. These differences were larger and more pervasive in the presence of mediolateral perturbations, evidenced by higher variability in step width, sacrum position, and margin of stability at heel-strike in PwMS than controls. PwMS also performed worse than controls on the SOT, and there was a modest correlation between step width variability during perturbed gait and SOT visual score. In conclusion, mediolateral optical flow perturbations revealed differences in walking balance in PwMS that went undetected during normal, unperturbed walking. Targeting this difference may be a promising approach to more effectively detect preclinical walking balance deficits in PwMS.

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“…By leveraging their reliance on visual feedback, optical flow perturbations designed to elicit the visual perception of instability routinely provoke corrective motor responses to preserve walking balance that are larger in older non-fallers than in young adults [8, 16] and larger still in older fallers [17, 18]. The cumulative insights from those studies suggests that older adults respond to those unpredictable balance challenges, at least during early exposure, by adopting what may be interpreted as a more cautious or generalized anticipatory balance control strategy.…”

Section: Introductionmentioning

confidence: 99%

Time-dependent tuning of balance control and aftereffects following optical flow perturbation training in older adults

Richards

Selgrade

Qiao

et al. 2019

J NeuroEngineering Rehabil

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Background Walking balance in older adults is disproportionately susceptible to lateral instability provoked by optical flow perturbations. The prolonged exposure to these perturbations could promote reactive balance control and increased balance confidence in older adults, but this scientific premise has yet to be investigated. This proof of concept study was designed to investigate the propensity for time-dependent tuning of walking balance control and the presence of aftereffects in older adults following a single session of optical flow perturbation training. Methods Thirteen older adults participated in a randomized, crossover design performed on different days that included 10 min of treadmill walking with (experimental session) and without (control session) optical flow perturbations. We used electromyographic recordings of leg muscle activity and 3D motion capture to quantify foot placement kinematics, lateral margin of stability, and antagonist coactivation during normal walking (baseline), early (min 1) and late (min 10) responses to perturbations, and aftereffects immediately following perturbation cessation (post). Results At their onset, perturbations elicited 17% wider and 7% shorter steps, higher step width and length variability (+171% and +132%, respectively), larger and more variable margins of stability (MoS), and roughly twice the antagonist leg muscle coactivation ( p -values<0.05). Despite continued perturbations, most outcomes returned to values observed during normal, unperturbed walking by the end of prolonged exposure. After 10 min of perturbation training and their subsequent cessation, older adults walked with longer and more narrow steps, modest increases in foot placement variability, and roughly half the MoS variability and antagonist lower leg muscle coactivation as they did before training. Conclusions Findings suggest that older adults: ( i ) respond to the onset of perturbations using generalized anticipatory balance control, ( ii ) deprioritize that strategy following prolonged exposure to perturbations, and ( iii ) upon removal of perturbations, exhibit short-term aftereffects that indicate a lessening of anticipatory control, an increase in reactive control, and/or increased balance confidence. We consider this an early, proof-of-concept study into the clinical utility of prolonged exposure to optical flow perturbations as a training tool for corrective motor adjustments relevant to walking balance integrity toward reinforcing task-specific, reactive control and/or improving balance confidence in older adults. Trial registration clinicaltrials.gov ( NCT03341728 ). Registered 14 November 2017. Electronic supplementary material The online version of this article (10.1186/s...

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Does local dynamic stability during unperturbed walking predict the response to balance perturbations? An examination across age and falls history

Abstract: We propose that predicting the response to balance perturbations in older fallers, at least that measured using local dynamic stability, likely requires measuring that response directly.

Cited by 16 publications

References 35 publications

Interactions Between Different Age-Related Factors Affecting Balance Control in Walking

Interactions Between Different Age-Related Factors Affecting Balance Control in Walking

Can optical flow perturbations detect walking balance impairment in people with multiple sclerosis?

Time-dependent tuning of balance control and aftereffects following optical flow perturbation training in older adults

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