Biology subjects

Render, A. C.

Publications and source records attributed to Render, A. C..

7 recordsLinked to original sources

bioRxiv2026

How Visual Context Influences Lateral Stepping Regulation While Walking on Winding Paths

Goal-directed walking involves regulating foot placements to achieve specific tasks. This requires visuomotor integration. Perceptual, cognitive, and contextual salience guide attention and motor planning for navigation. Here, we quantified how perceptual salience informs lateral foot placement while walking. Participants walked along prescribed virtual paths (straight or winding), thus keeping contextual salience (the task itself) constant. We manipulated perceptual salience by systematically altering environment richness (rich vs. sparse) and path color contrast (high vs. low). We thus tested the extent to which stepping control is determined only by the walking path (i.e. its shape), or is also influenced by task-relevant salience of the paths (only), and/or the salience of the surrounding environment. We quantified head pitch angle to approximate gaze direction. We quantified lateral stepping regulation from a Goal Equivalent Manifold framework. On winding (vs. straight) paths, participants looked down more (lower mean head pitch) and more consistently (less variable head pitch). They took narrower, more variable steps and corrected stepping errors more strongly. This confirmed the predominant influence of task (contextual salience) on stepping control. On low (vs. high) contrast paths, participants looked down more and exhibited greater variability in lateral position on their path with weaker error correction. Higher contrast paths elicited stronger and more consistent stepping control. Walking in sparse (vs. rich) environments yielded somewhat less consistent, but still significant changes in head pitch and stepping regulation. Salience manipulations affected stepping differently on straight versus winding paths. Therefore, perceptual salience influences step-to-step control during naturalistic walking.

neuroscience↗

bioRxiv2026

Visual Context Influences Lateral Balance While Walking on Winding Paths

Effectively navigating daily environments necessitates achieving adaptability while maintaining stability. This requires integrating sensory feedback, primarily from the visual system, to maintain balance and maneuverability as we walk. This study examined the impact of visual information salience on lateral balance and stepping. Twenty-eight healthy adults (16F/12M; 26.16{+/-}4.23 years) participated. Participants walked along each of two virtual paths (Straight vs. Winding), having each of two path color contrasts (High vs. Low), in each of two environments with differing visual richness (Rich vs. Sparse). We quantified stepping errors as the percentage of steps landing outside designated path boundaries. We computed means () and standard deviations ({sigma}) of the minimum mediolateral margins of stability (MoSL), and we computed lateral Probability of Instability (PoIL) to assess participants risk of taking unstable (MoSL < 0) steps. On Straight paths, participants made more stepping errors on Low (vs. High) contrast paths for both environments, and exhibited decreased{sigma} (MoSL) in Sparse (vs. Rich) environments on paths of both visual contrasts. On Winding paths, participants made the most stepping errors on Low Contrast paths in Sparse environments. They walked with smaller (MoSL) and exhibited higher PoIL on Low Contrast paths in both environments, and they exhibited higher PoIL in Sparse environments on paths of both visual contrasts. The effects of diminished visual information were far more pronounced on Winding paths (vs. Straight), hindering performance and balance maintenance, as these conditions challenged both mechanical and sensory mechanisms underlying balance control.

neuroscience↗

bioRxiv2026

Effects of one night of sleep deprivation on single- and dual-task gait

Sleep deprivation impairs cognitive control, which may affect movements that rely on these processes, such as walking. To test whether gait changes after one night of sleep deprivation reflect reduced cognitive capacity, we compared its effects with those of dual-task walking (i.e., walking while performing a simultaneous cognitive task). We hypothesize that sleep deprivation will produce gait changes similar to those under dual-task conditions. Eighteen healthy adults (9 female, 9 male; 22.2 (2.3) yrs) were tested the morning after a sleep deprivation (SDEP) and a control night. Participants completed two 2-min trials: single-task walking and walking with a concurrent 2-back working memory task (DT, dual-task). Using lateral foot and pelvis marker trajectories, we calculated spatiotemporal parameters, foot placement error in antero-posterior (FPEAP) and mediolateral (FPEML) directions, and mediolateral margin of stability (MoSML). SDEP increased average step time (p<0.001) and step length (p=0.001), and DT reduced spatiotemporal variability. Both SDEP (p=0.001) and DT (p<0.001) reduced FPEAP, but only DT reduced FPEML (p<0.001). Additionally, mean MoSML decreased only in SDEP (p=0.011). Overall, these findings suggest that while sleep deprivation and dual-tasking both affect gait, the effects of sleep deprivation on gait cannot be fully explained by reduced cognitive resources.

neuroscience↗

bioRxiv2025

Misalignment between perceived and actual ability on a balance beam walking task

Effective dynamic balance control is necessary to maintain stability, but it is an individuals self-perceived ability that ultimately determines movement selection. Accurate self-estimation of balance ability is therefore essential to ensure that movement choices align with true capability. This study examined individuals perception of their ability on a clinically standardized Narrowing Beam Walking Task (NBWT) to examine 1) the initial perception of balance ability before attempting the task, and 2) how experience completing the task improves the accuracy of self-perceived balance. Collegiate athletes provided self-estimates of performance at baseline (before any trials with the task), early-training (after completing two trials), and post-training (after a further 8 trials). Actual task performance was quantified using the final 8 trials. At baseline, athletes poorly estimated their ability: individuals with poorer task performance tended to overestimate their ability while higher-performing individuals tended to underestimate their ability. With practice, absolute estimation error significantly decreased, indicating that task-specific exposure facilitated recalibration to bring self-estimates of performance in closer alignment to actual performance. These effects were consistent across all tested sporting disciplines. These findings show that effective balance control and frequent engagement in similar, but unrelated balance tasks, does not facilitate accurate self-perception of performance on the NBWT. Instead, brief task-specific exposure was required to refine balance estimates. These findings have implications for balance testing and rehabilitation that seeks to improve mobility in populations whose misjudgments of balance ability are often associated with negative outcomes, such as falls.

physiology↗

bioRxiv2024

Probability of Lateral Instability While Walking on Winding Paths

People with balance impairments often struggle performing turns or lateral maneuvers, which can increase risk of falls and injuries. Here we asked how peoples mediolateral balance is impacted when walking on non-straight winding paths. Twenty-four healthy adults (12F/12M; 25.8{+/-}3.5 yrs) participated. Each walked on each of six paths projected onto a treadmill, comprised of three pseudo-random path oscillation frequency combinations (straight, slowly-winding, quickly-winding), each presented at either wide or narrow width. We quantified stepping errors as the percent of steps taken off each path. We quantified minimum mediolateral Margin of Stability (MoSL) at each step and calculated means () and standard deviations ({sigma}) for each trial. We calculated lateral Probability of Instability (PoIL) as participants statistical risk of taking unstable (MoSL < 0) steps. On narrower paths, participants made more stepping errors and walked with smaller (MoSL) on all paths (p < 0.001), and exhibited increased PoIL on the straight and slowly-winding paths (p < 0.001). On winding paths, participants made progressively more stepping errors and walked with smaller (MoSL) for increasingly sinuous narrow paths (all p < 0.001) and wide quickly-winding paths (all p < 0.001). They also consistently walked with larger{sigma} (MoSL), and increased PoIL on higher sinuosity paths of both widths (all p < 0.001). Though many took numerous unstable steps, no participant fell. Our results demonstrate healthy adults ability both to trade off increased risk of lateral instability for greater maneuverability, and to employ highly-versatile stepping strategies to maintain balance while walking.

bioengineering↗

bioRxiv2024

Adapting Lateral Stepping Control to Walk on Winding Paths

Most often, gait biomechanics is studied during straight-ahead walking. However, real-life walking imposes various lateral maneuvers people must navigate. Such maneuvers challenge peoples lateral balance and can induce falls. Determining how people regulate their stepping movements during such complex walking tasks is therefore essential. Here, 24 adults (12F/12M; Age 25.8{+/-}3.5yrs) walked on wide or narrow virtual paths that were either straight, slowly-winding, or quickly-winding. From each trial, we computed time series of participants step widths and their lateral body positions relative to their path. We applied our Goal Equivalent Manifold framework - an analysis of how task-level redundancy impacts motor regulation - to quantify how participants adjusted their step width and lateral position from step to step as they walked on these paths. On the narrower paths, participants walked with narrower steps and less lateral position and step width variability. They did so by correcting step-to-step deviations in lateral position more, while correcting step-to-step deviations in step width less. On the winding paths, participants took both narrower and more variable steps. Interestingly, on slowly-winding paths, participants corrected step-to-step deviations in step width more by correcting step-to-step deviations in lateral position less: i.e., they prioritized maintaining step width over position. Conversely, on quickly-winding paths, participants strongly corrected step-to-step deviations in both step width and lateral position: i.e., they prioritized maintaining both approximately equally, consistent with trying to maximize their maneuverability. These findings have important implications for persons with gait impairments who may have elevated fall risk.

bioengineering↗

bioRxiv2023

Generalizing Stepping Concepts To Non-Straight Walking

People rarely walk in straight lines. Instead, we make frequent turns or other maneuvers. Spatiotemporal parameters fundamentally characterize gait. For straight walking, these parameters are well-defined for that task of walking on a straight path. Generalizing these concepts to non-straight walking, however, is not straightforward. People also follow non-straight paths imposed by their environment (store aisle, sidewalk, etc.) or choose readily-predictable, stereotypical paths of their own. People actively maintain lateral position to stay on their path and readily adapt their stepping when their path changes. We therefore propose a conceptually coherent convention that defines step lengths and widths relative to known walking paths. Our convention simply re-aligns lab-based coordinates to be tangent to a walkers path at the mid-point between the two footsteps that define each step. We hypothesized this would yield results both more correct and more consistent with notions from straight walking. We defined several common non-straight walking tasks: single turns, lateral lane changes, walking on circular paths, and walking on arbitrary curvilinear paths. For each, we simulated idealized step sequences denoting "perfect" performance with known constant step lengths and widths. We compared results to path-independent alternatives. For each, we directly quantified accuracy relative to known true values. Results strongly confirmed our hypothesis. Our convention returned vastly smaller errors and introduced no artificial stepping asymmetries across all tasks. All results for our convention rationally generalized concepts from straight walking. Taking walking paths explicitly into account as important task goals themselves thus resolves conceptual ambiguities of prior approaches.

neuroscience↗