Biology subjects

Kazanski, M. E.

Publications and source records attributed to Kazanski, M. E..

5 recordsLinked to original sources

bioRxiv2024

How Older Adults Maintain Lateral Balance While Walking on Narrowing Paths

BackgroundOlder adults have difficulty maintaining side-to-side balance while navigating daily environments. Losing balance in such circumstances can lead to falls. We need to better understand how older adults adapt lateral balance to navigate environment-imposed task constraints. Research QuestionHow do older adults adjust mediolateral balance while walking along continually-narrowing paths, and what are the stability implications of these adjustments? MethodsEighteen older (71.6{+/-}6.0 years) and twenty younger (21.7{+/-}2.6 years) healthy adults traversed 25m-long paths that gradually narrowed from 45cm to 5cm. Participants switched onto an adjacent path when they chose. We quantified participants lateral center-of-mass dynamics and lateral Margins of Stability (MoSL) as paths narrowed. We quantified lateral Probability of Instability (PoIL) as the cumulative probability that participants would take a laterally unstable (MoSL<0) step as they walked. We also extracted these outcomes where participants switched paths. ResultsAs paths narrowed, all participants exhibited progressively smaller average MoSL and increasingly larger PoIL. However, their MoSL variability was largest at both the narrowest and widest path sections. Older adults exhibited consistently both larger average and more variable MoSL across path widths. Taken into account together, these resulted in either comparable or somewhat larger PoIL as paths narrowed. Older adults left the narrowing paths sooner, on average, than younger. As they did so, older adults exhibited significantly larger average and more variable MoSL, but somewhat smaller PoIL than younger. SignificanceOur results directly challenge the predominant interpretation that larger average MoSL as indicating "greater stability", which we argue is inconsistent with the principles underlying its derivation. In contrast, analyzing step-to-step gait dynamics, together with estimating PoIL allows one to properly quantify instability risk. Furthermore, the adaptive strategies uncovered using these methods suggest potential targets for future interventions to reduce falls in older adults.

bioengineering↗

bioRxiv2023

Associations between music and dance relationships, rhythmic proficiency, and spatiotemporal movement modulation ability in adults with and without mild cognitive impairment

BackgroundPersonalized dance-based movement therapies may improve cognitive and motor function in individuals with mild cognitive impairment (MCI), a precursor to Alzheimers disease. While age- and MCI-related deficits reduce individuals abilities to perform dance-like rhythmic movement sequences (RMS)--spatial and temporal modifications to movement--it remains unclear how individuals relationships to dance and music affect their ability to perform RMS. ObjectiveCharacterize associations between RMS performance and music or dance relationships, as well as the ability to perceive rhythm and meter (rhythmic proficiency) in adults with and without MCI. MethodsWe used wearable inertial sensors to evaluate the ability of 12 young adults (YA; age=23.9{+/-}4.2 yrs; 9F), 26 older adults without MCI (OA; age=68.1{+/-}8.5 yrs; 16F), and 18 adults with MCI (MCI; age=70.8{+/-}6.2 yrs; 10F) to accurately perform spatial, temporal, and spatiotemporal RMS. To quantify self-reported music and dance relationships and rhythmic proficiency, we developed Music (MRQ) and Dance Relationship Questionnaires (DRQ), and a rhythm assessment (RA), respectively. We correlated MRQ, DRQ, and RA scores against RMS performance for each group separately. ResultsThe OA and YA groups exhibited better MRQ and RA scores than the MCI group (p<0.006). Better MRQ and RA scores were associated with better temporal RMS performance for only the YA and OA groups (r2=0.18-0.41; p<0.045). DRQ scores were not associated with RMS performance in any group. ConclusionsCognitive deficits in adults with MCI likely limit the extent to which music relationships or rhythmic proficiency improve the ability to perform temporal aspects of movements performed during dance-based therapies.

neuroscience↗

bioRxiv2023

How Older Adults Regulate Lateral Stepping on Narrowing Walking Paths

Walking humans often navigate complex, varying walking paths. To reduce falls, we must first determine how older adults purposefully vary their steps in contexts that challenge balance. Here, 20 young (21.7{+/-}2.6 yrs) and 18 older (71.6{+/-}6.0 yrs) healthy adults walked on virtual paths that slowly narrowed (from 45 cm to as narrow as 5 cm). Participants could switch onto an "easier" path whenever they chose. We applied our Goal Equivalent Manifold framework to quantify how participants adjusted their lateral stepping variability and step-to-step corrections of step width and lateral position as these paths narrowed. We also extracted these characteristics where participants switched paths. As paths narrowed, all participants reduced their lateral stepping variability, but older adults less so. To stay on the narrowing paths, young adults increasingly corrected step-to-step deviations in lateral position more, by correcting step-to-step deviations in step width less. Conversely, as older adults also increasingly corrected lateral position deviations, they did so without sacrificing correcting step-to-step deviations in step width, presumably to preserve balance. While older adults left the narrowing paths sooner, several of their lateral stepping characteristics remained similar to those of younger adults. While older adults largely maintained overall walking performance per se, they did so by changing how they balanced the competing stepping regulation requirements intrinsic to the task: maintaining position vs. step width. Thus, balancing how to achieve multiple concurrent stepping goals while walking provides older adults the flexibility they need to appropriately adapt their stepping on continuously narrowing walking paths.

bioengineering↗

bioRxiv2023

How Healthy Older Adults Enact Lateral Maneuvers While Walking

BackgroundWalking requires frequent maneuvers to navigate changing environments with shifting goals. Humans accomplish maneuvers and simultaneously maintain balance primarily by modulating their foot placement, but a direct trade-off between these two objectives has been proposed. As older adults rely more on foot placement to maintain lateral balance, they may be less able to adequately adapt stepping to perform lateral maneuvers. Research QuestionHow do older adults adapt stepping to enact lateral lane-change maneuvers, and how do physical and perceived ability influence their task performance? MethodsTwenty young (21.7 {+/-} 2.6 yrs) and 18 older (71.6 {+/-} 6.0 yrs) adults walked on a motorized treadmill in a virtual environment. Following an audible and visual cue, participants switched between two parallel paths, centered 0.6m apart, to continue walking on their new path. We quantified when participants initiated the maneuver following the cue, as well as their step width, lateral position, and stepping variability ellipses at each maneuver step. ResultsYoung and older adults did not differ in when they initiated the maneuver, but participants with lower perceived ability took longer to do so. Young and older adults also did not exhibit differences in step width or lateral positions at any maneuver step, but participants with greater physical ability reached their new path faster. While only older adults exhibited stepping adaptations prior to initiating the maneuver, both groups traded-off stability for maneuverability to enact the lateral maneuver. SignificancePhysical and perceived balance ability, rather than age per se, differentially influenced maneuver task performance. Humans must make decisions related to the task of walking itself and do so based on both physical and perceived factors. Understanding and targeting these interactions may help improve walking performance among older adults.

neuroscience↗

bioRxiv2021

Rethinking Margin of Stability: Incorporating Step-To-Step Regulation to Resolve the Paradox

Derived from inverted pendulum dynamics, mediolateral Margin of Stability (MoSML) is a mechanically-grounded measure of instantaneous stability. However, average MoSML measures yield paradoxical results. Gait pathologies or perturbations often induce larger (supposedly "more stable") average MoSML, despite clearly destabilizing factors. However, people do not walk "on average" - they walk (and sometimes lose balance) one step at a time. We assert the paradox arises because averaging discards step-to-step dynamics. We present a framework unifying the inverted pendulum with Goal-Equivalent Manifold (GEM) analyses. We identify in the pendulums center-of-mass dynamics constant-MoSML manifolds, including one candidate "stability GEM" signifying the goal to maintain some constant [Formula]. We used this framework to assess step-to-step MoSML dynamics of humans walking in destabilizing environments. While goal-relevant deviations were readily corrected, humans did not exploit equifinality by allowing deviations to persist along this GEM. Thus, maintaining a constant [Formula] is inconsistent with observed step-to-step fluctuations in center-of-mass states. Conversely, the extent to which participants regulated fluctuations in foot placements strongly predicted regulation of center-of-mass fluctuations. Thus, center-of-mass dynamics may arise indirectly as a consequence of regulating mediolateral foot placements. To resolve the paradox caused by averaging MoSML, we present a new statistic, Probability of Instability (PoIL), to predict instability likelihood. Participants exhibited increased PoIL when destabilized (p = 9.45x10-34), despite exhibiting larger ("more stable") average MoSML (p = 1.70x10-15). Thus, PoIL correctly captured peoples increased risk of losing lateral balance, whereas average MoSML did not. PoIL also explains why peoples average MoSML increased in destabilizing contexts.

bioengineering↗