Human Movement Science

Walking is an attentionally demanding process that draws from a limited pool of attentional resources. Dual-task assessments, where individuals perform a cognitive task while walking, often reveal changes in gait and balance due to competing attentional demands. As cognitive task difficulty increases, the attentional resources necessary to complete the task also increase, leading to greater interference with gait and balance. However, these interactions are typically examined using contrived lab-based tasks, leaving it unclear how the cognitive processes engaged during real-world movement impact walking. In the present study, we investigated whether increasing the attentional demand of spatial navigation, a cognitive process intrinsically linked to movement, interferes with gait and balance. Healthy adults completed an ambulatory virtual reality homing task in which they walked through a virtual environment and navigated to previously visited locations while wearing ankle and lumbar trackers. We increased the attentional demand of navigation by removing sensory cues during this homing phase: full cues, visual cues only, or self-motion cues only. Navigation performance declined as sensory cues were removed, but we observed no corresponding changes in their spatiotemporal gait and balance metrics. These results show that, in healthy adults, increasing the attentional demand of spatial navigation does not interfere with gait and balance during real-world movement. This finding suggests that locomotor control may be robust to navigation-related cognitive demands. Further research is needed to determine why navigation did not interfere with mobility and to clarify the relationship between these two interconnected processes.

Purposeto characterize the dynamic postural control during weight load shifting with and without support surface reduction with temporal metrics commonly used in linear control systems identification. MethodsFrom the COP coordinates temporal, global and structural parameters were calculated. Reliability of derived parameters were determined using Bland-Altman analysis. ResultsFor the observed population, temporal variables tend to decrease when the complexity of the task is increased with the reduction in the support surface and the non dominance. ConclusionDelay and rise times were significantly shorter for the non-dominant limb in the anteroposterior direction when volunteers performed the same task with different limbs. In the mediolateral direction, delay and rise times were shorter in both unipodal stances with respect to their bipodal homologues. An increase in COP path length, velocity and sample entropy was observed when the support area was reduced. All parameters showed good reliability in both directions at all stances. This framework could be used in the clinical practice to assess dynamic postural control capabilities in patients whose balance is pathologically affected. The trial was evaluated and approved by the Central Committee of Bioethics in Biomedical Practice and Research of the province of Entre Rios.

Practice-transfer paradigms are central to motor learning research, yet dynamic balance lacks standardized, internally valid practice-transfer task pairings. This study evaluated whether a mediolateral tilt board can serve as a valid transfer task for stabilometer-based balance assessment. Sixteen healthy young adults (20-35 years) completed a single session consisting of two 40-second trials on a mediolateral stabilometer and two 40-second trials on a mediolateral tilt board. Participants aimed to keep each platform horizontal during each trial. Performance outcomes were derived from platform deviation angle. Neuromuscular outcomes were derived from surface EMG of bilateral gluteus medius, vastus lateralis, and vastus medialis, including muscle synergy structure, bilateral co-activation index, RMS amplitude of muscle activation, and strategy ratios (hip-to-knee and asymmetry metrics). Between-task associations were assessed using Spearman correlations. Cross-task muscle synergy similarity was high (mean cosine similarity = 0.915 {+/-} 0.044) and close to within-task trial-to-trial similarity, indicating preserved modular coordination across devices. Performance metrics were moderately to strongly correlated between tasks (RMS deviation angle: {rho} = 0.621, p = 0.0089; time-in-balance: {rho} = 0.668, p = 0.0036). EMG-derived strategy metrics also correlated significantly across tasks, including bilateral co-activation ({rho} = 0.688, p = 0.0023), hip-to-knee ratio ({rho} = 0.765, p = 0.0003), hip asymmetry ratio ({rho} = 0.688, p=0.0023), and knee asymmetry ratio ({rho} = 0.679, p = 0.0028). In contrast, EMG RMS amplitude did not correlate across tasks ({rho} = -0.044, p = 0.873), suggesting task-specific gain of activation magnitude. Stabilometer and tilt board tasks shared a similar coordination structure and showed a high correlation in balance performance and neuromuscular strategy, supporting the tilt board as an internally valid transfer task for stabilometer-based dynamic balance paradigms. Similarity of tasks appears strongest at the level of modular control and strategy organization, with device-specific gain scaling of activation amplitude.

Flow state, characterized by optimal engagement and performance, represents a key concept in understanding human performance and cognitive resource allocation. Grounded in Csikszentmihalyis and Sherrys flow theory and the Limited Capacity Model of Motivated Mediated Message Processing (LC4MP), this study investigated physiological and neural correlates of flow state during a simulated driving task under different music conditions and difficulty levels. Using a 2 x 3 factorial design with 20 participants, this study examined self-selected versus non-self-selected music across three difficulty levels, testing the relationship between task switching, cognitive resource allocation, and flow state. Physiological measures included heart rate and EEG (alpha/theta power) using a 4-channel Muse 2 headband, alongside a self-report measure of flow experience. Hierarchical linear modeling revealed significant physiological changes during self-selected music: heart rate decreased ({beta} = -5.15, p < .001), while alpha ({beta} = 5829.77, p < .001) and theta power ({beta} = 7637.24, p < .001) increased. Task difficulty also showed significant effects, with heart rate decreasing during hard ({beta} = -6.70, p < .001) and moderate ({beta} = -3.40, p = .001) conditions. In particular, while physiological measures showed robust changes, the self-reported flow state did not reach significance. Task switching rates showed significant decreases during self-selected music ({beta} = -0.86, p < .001) and hard difficulty ({beta} = -0.61, p < .001), supporting the LC4MP frameworks predictions regarding cognitive resource allocation. These findings demonstrate how task switching and cognitive resource allocation relate to flow state induction. The results highlight the importance of multimodal measurement approaches and demonstrate that personal relevance through music selection and task difficulty significantly influence physiological and neural responses during performance. Future research should employ more comprehensive measurement approaches to better capture the complexity of flow-related neural activity and its relationship to task switching and cognitive resource allocation.

Gait asymmetry is a common manifestation of walking impairment among clinical populations. We recently developed a novel treadmill walking approach called dynamic treadmill walking that can provide asymmetric gait training by changing the treadmill speed between fast and slow speeds within a single stride. Here, we studied the energy expenditure associated with a variety of dynamic treadmill walking conditions. We hypothesized that the metabolic power required for dynamic treadmill walking in all conditions would approximate the metabolic power associated with conventional walking at the mean of the fast and slow speeds employed in the task. Eleven young adults without gait impairment walked on an instrumented treadmill and breathed into a metabolic measurement system. During dynamic treadmill walking, the treadmill fluctuated between 0.75m/s and 1.50m/s, each for 50% of an individuals stride time. We used a metronome to synchronize participants right heel-strikes with four different timing conditions. Net metabolic power during dynamic treadmill walking was significantly greater than normal walking at the mean speed of the task (1.125m/s) and generally lower than walking at the fast speed (1.5m/s). We did not observe any significant associations between net metabolic power and several measures of gait asymmetry during dynamic treadmill walking. These findings establish dynamic treadmill walking as a promising technique for improving gait symmetry in individuals who cannot tolerate fast treadmill walking, a common gait rehabilitation approach. Future work will assess the feasibility, metabolic demands, and clinical efficacy of using dynamic treadmill walking to improve gait symmetry in clinical populations. Key Points SummaryO_LIDynamic treadmill walking (i.e., walking with oscillating treadmill speeds) has previously been shown to drive gait asymmetries, but little is known about the energy expenditure required to complete the task. C_LIO_LIOur hypothesis was that dynamic treadmill walking would have similar metabolic power requirements to normal walking at a speed that is intermediate between the two dynamic treadmill walking speeds. C_LIO_LIWe found that dynamic treadmill walking actually requires metabolic power that is greater than the average of the two belt speeds, but less than that used for fast walking. C_LIO_LIDynamic treadmill walking is a promising and clinically translatable technique for rehabilitating populations with gait asymmetries that is not more energetically costly than fast treadmill walking, a common gait rehabilitation approach. C_LI

A consistent finding across studies with older adults is that they typically perform worse at spatial memory tasks, particularly those conducted in virtual reality and involving novel environments, compared to young adults. While the underlying reasons for this difference remain unclear, some proposed hypotheses include differences in sensory cue integration and cue conflict resolution. Here, we tested older (n = 29) and young adults (n = 28) in immersive and walkable virtual reality using both correctly rendered and illusory hallways to test how visual cues (i.e., an intersection) and self-motion cues are integrated. In the illusory or false-intersection condition, we hypothesized that participants who walked an uncrossed path would merge two disconnected intersections, creating the illusion of a crossed path. The overall accuracy and pointing patterns were similar between young and older adults in both true- and false-intersection conditions. We did find, however, a significant age by condition interaction effect in egocentric pointing variability where older adults showed lower variability in the illusory condition and higher variability in the control condition. At the same time, older adults also drew worse maps for the control condition compared to young adults. However, the pointing error correlated with the accuracy of maps drawn regardless of age, suggesting that the pointing patterns shown by both age groups related to their underlying representations of the paths. Our findings are inconsistent with a global deficit in allocentric navigation or path integration and instead suggest that more subtle differences in strategy use might manifest with age.

Sensorimotor learning and tool use involve synchronizing with external dynamics. Many everyday tools possess nonlinear hidden dynamics. Here we investigate how learning to synchronize with the complex dynamics of a tool depends on the degree of predictability and reciprocal coupling between user and tool. We introduce the concept of optimal coupling to measure adaptive user-tool coordination. Groups of participants practiced tracking an auditory stimulus in three conditions: 1) the tool was non-interactive and produced a periodic stimulus, 2) non-interactive and unstable stimulus, and 3) unstable but interactive stimulus which was coupled weakly to the participants movements and thus afforded control. Learning, retention, and transfer to visual modality were assessed using unpracticed test stimuli. Directional effective coupling was quantified using transfer entropy. Results showed that learning tended to be task-specific and there was no transfer to the visual modality. Interactive unstable practice exhibited some retention and generalization. We found a convergent reorganization of coupling during practice with the interactive unstable tool: stimulus-to-human coupling started high and decreased while human-to-stimulus coupling started low and increased. This suggests that embodiment of personalized rehabilitation technologies brings optimal reciprocal coupling in which sensorimotor-tool control is consistent with the minimal intervention principle postulated for within-body control.

BackgroundTreadmill walking is often employed for tightly controlled gait and energetics research, but growing evidence suggests that treadmill-based metabolic and biomechanical measurements may not directly reflect the ecologically valid mode of overground walking. While many previous studies focused on older adults, much less is known about how treadmill walking influences gait energetics and spatiotemporal parameters in young healthy adults across matched speeds. Aims and ObjectivesWe investigated energy expenditure, metabolic cost of walking and spatiotemporal gait parameters in healthy young adults walking overground and on a treadmill at three speeds (slow-1.0, comfortable-1.3, fast-1.5 m/s). Our hypothesis was that at the comfortable speed, treadmill and overground energetics and gait parameters would be comparable. However, at slow and fast speeds, there would be a significant energetic penalty, accompanied by significant differences in spatiotemporal parameters. MethodsTwenty young participants (10 males and 10 females) completed a randomized cross-over walking protocol with a minimum of ten minutes treadmill familiarization at 1.3 m/s. Breath-by-breath oxygen consumption [Formula] and Respiratory Exchange Ratio were measured using a portable indirect calorimetry system and gait parameters were calculated from Inertial Measurement Units. Gross and net energy expenditures, costs of walking, cadence, average step and stride lengths were calculated. A three-way mixed ANOVA was used for primary statistical analyses. ResultsTreadmill walking was characterized by higher gross and net energy expenditures and metabolic costs (p<0.001, p2 = 0.6) across all speeds compared to overground. It was also characterized by faster cadence and shorter average step and stride lengths (p<0.001, p2 = 0.9). Additionally, there was an effect of sex (p = 0.01, p2 = 0.3) on the gait parameters, with females exhibiting a faster cadence and shorter average step and stride lengths than males. Discussion and ConclusionsOur findings show that treadmill walking imposes a medium-to-large metabolic penalty even in healthy young adults, with compensatory gait adaptations, possibly reflecting increased stabilization demands and altered neuromuscular control strategies. These results underscore the limits of generalizing treadmill derived gait data to overground walking and we caution against the uncritical use of treadmills, especially while trying to understand ecologically relevant human walking mechanics and energetics.

Response inhibition, the ability to suppress contextually inappropriate actions, is a cornerstone of cognitive control and is commonly assessed using paradigms such as the go/no-go task. However, traditional go/no-go paradigms rely on binary outcomes such as commission errors, which offer limited insight into the dynamic, graded behavioral adjustments underlying successful stopping. The present study developed a novel mouse-tracking go/no-go paradigm with a dynamic start to capture inhibitory processes during ongoing execution. Twenty-three healthy young adults completed the task in two sessions separated by approximately one week to evaluate the test-retest reliability of standard behavioral measures (error rates and reaction times), and three kinematic features: path length, mean velocity, and mean acceleration. Results revealed robust differences between go and no-go trials across all measures. Successful inhibition was characterized by significantly shorter path lengths and reduced mean velocity and acceleration compared to go trials. Critically, all measures demonstrated moderate-to-good test-retest reliability across sessions, with intraclass correlation coefficients ranging from .75 to .85 for go trials and from .59 to .83 for no-go trials. These findings establish construct validity and psychometric reliability of the current mouse-tracking go/no-go paradigm. The demonstrated stability of these measures provides the methodological foundation for their use in cross-sectional, longitudinal, and intervention research targeting inhibitory control.

Virtual Reality (VR) applications depend on eliciting spatial presence, the subjective experience of being physically located within a virtual environment. Although individual differences have long been theorised to contribute to this experience, their role in highly immersive VR systems remains contested. The present study investigated whether trait absorption predicts spatial presence and whether this relationship is mediated by attention allocation. Seventy participants (44 female, 26 male; M age = 22.90, SD = 4.88) completed a 6-minute VR session using a Meta Quest 3 Head-Mounted Display and validated self-report measures of trait absorption (Tellegen Absorption Scale), attention allocation, and spatial presence (MEC-Spatial Presence Questionnaire). Path analysis confirmed a significant, complete mediation pathway: trait absorption positively predicted attention allocation ({beta} = 0.27, p = .013), which in turn strongly predicted spatial presence ({beta} = 0.54, p < .001). The direct path from absorption to spatial presence was non-significant ({beta} = 0.11, p = .325), indicating complete mediation. The indirect effect was significant ({beta} = 0.15; 95% BCa CI [0.025, 0.291]). The model explained a sizeable 33.8% of the variance in spatial presence (Cohens f{superscript 2} = 0.51). Post-hoc dose-response analysis revealed that trait absorption acts as a cognitive amplifier: the strength of the attention-presence relationship tripled from low-absorption ({beta} = 0.33, R{superscript 2} = .15) to high-absorption individuals ({beta} = 1.00, R{superscript 2} = .56). These findings demonstrate that individual differences remain important in highly immersive VR by modulating the effectiveness of attentional focus, offering promising directions for tailoring VR interventions.

Sensory degradation with aging can impair balance control, partly by disrupting visual contributions to self-motion estimation. We investigated how aging affects the control of frontal plane center of mass (CoM) trajectories during walking with exposure to repeated visual perturbations. We hypothesized that aging would increase responses to visual perturbations and decrease adaptation to repeated visual perturbation exposure. We applied three visual perturbations to 14 healthy older (age: 75.0{+/-}2.4) and 16 younger adults (age: 23.4{+/-}3.9) walking on a treadmill: fixating a stationary target with the background moving to the right (MB), tracking a target moving rightward over a stationary background with head rotation (MT-HR), and tracking a moving target with eye movement only (MT-EM). Deviations of CoM position and foot placement due to the visual perturbations were assessed. Over the whole trial, the older adults exhibited larger CoM position variability in MB and MT-HR conditions. During visual perturbation epochs, both age groups deviated in the same direction except MB. In MB, the older adults deviated to an opposite direction after a few perturbation repetitions. Moreover, in MT-HR and MT-EM, the older adults deviated earlier than the younger adults and they deviated more in the MT-HR condition. This indicates that older adults exhibit reduced ability to accurately estimate self-motion through correction by other sensory modalities when exposed to visual perturbations. Over repeated perturbations, the older adults showed decreased CoM deviations in MT-EM, which suggests that they still maintain the capacity to downweight visual information after repeated exposure.

Background: Accurate evaluation of fine motor abilities is a key aspect of neurological rehabilitation. However, conventional approaches like goniometry are limited by variations among raters and their difficulty in detecting active movement. On the other hand, computer vision-based software delivers non-invasive and quantitative analysis of hand movements. An innovative computer-vision-based software tool, F.A.I.R. Chance(C), was developed to track and analyze individual finger joint movements on a camera-equipped laptop and give real-time numerical feedback. However, its metrics require validation in a healthy population before the tool can be used for clinical purposes. Objective: To assess the reliability and validity of finger movement assessment by the F.A.I.R. Chance computer vision-based tool in healthy adult participants. Methods: An observational cross-sectional study was done at MGM School of Physiotherapy, comprising 30 healthy participants between 18 and 60 years of age. Finger movements like flexion, extension, abduction, and adduction were measured with a standard handheld goniometer. These same finger movements were then measured with the tool at two time points separated by a 30-minute interval to determine the test-retest reliability. The tool's measurements were compared with the goniometric measurements to determine its concurrent validity. Test retest reliability was checked by the Intra-class Correlation Coefficient ICC (2,1), while concurrent validity was tested through Pearson's correlation coefficients. Results: Metacarpophalangeal and proximal interphalangeal joint motions demonstrated moderate to good test-retest reliability (ICC: 0.716-0.953) for the F.A.I.R. Chance tool. However, distal interphalangeal joint movements had lower consistency. Good reliability (ICC: 0.754-0.908) was seen for movements of abduction and adduction in the fingers. Strong concurrent validity for extension movements of the metacarpophalangeal joints (r=0.760-0.914) and moderate concurrent validity for flexion movements of the metacarpophalangeal joints (r=0.427-0.604) was demonstrated for all fingers for the F.A.I.R. Chance tool. Concurrent validity for adduction and abduction movements demonstrated a low to fair correlation with goniometric measurements (r=0.210-0.440). This is consistent with previous research showing poor agreement between goniometry and adduction-abduction movements of the fingers. Conclusion: The F.A.I.R. Chance tool shows good reliability and acceptable concurrent validity to assess fine motor movements in the healthy adult population. This sets a basis for further clinical study of the tool in the target population with fine motor impairments. Keywords: artificial intelligence; assistive technology; computer vision; fine motor evaluation; hand function;

The role of passive muscle mechanical properties in explosive performance is important to understand to maximize training and performance in strength sports. The objective of this study was to create and test a Structural Equation Model (SEM) to analyze the interrelations between muscle mechanical properties and neuromuscular performance in competitive weightlifters. The MyotonPRO was used to measure muscle stiffness, muscle tone, muscle elasticity, relaxation time and creep of four major muscles: Quadriceps Femoris, Hamstrings, Trapezius and Biceps Brachii, on thirty elite male weightlifters. This involved performance metrics of the rate of force development (RFD), countermovement jump (CMJ) and time to contraction threshold (TCT). AMOS was used to analyze the direct and indirect relationships between variables through SEM analysis. These findings indicated that muscle stiffness and relaxation time were significant predictors of explosive performance measures (p < 0.05) but there were weak or no relationships between tone, elasticity and creep. The model proposed had good fit indices (CFI = 0.97, RMSEA = 0.049) indicating its structural soundness. These results present the significance of muscle stiffness and relaxation time as important predictors of neuromuscular performance. The proposed model suggests an effective structure of monitoring athletes, their performance optimization, and individual training design in strength-based sports.

Mental fatigue is induced by prolonged engagement in cognitively demanding tasks and impairs endurance performance. The neuropsychophysiological mechanisms underlying this decreased performance remain unclear, with suggestion that mental fatigue may disrupt motor command and consequently muscle activation. We aimed to test this hypothesis in a repeated cross-over design study in which 18 participants completed two experimental sessions involving a time-to-exhaustion cycling test at 80% of peak power output. Each cycling task was preceded by 1h of a prolonged Stroop task (Stroop session) or a neutral control task (Control session). Perception of effort and surface electromyography from ten lower-limb muscles of the right leg were recorded at regular intervals during cycling. Mental fatigue was higher in the Stroop compared to the Control session (p = .002). Endurance cycling time was 111 {+/-} 160 s shorter in the Stroop than in the Control session (p = .009). No significant differences in electromyography parameters were observed between Stroop and Control sessions, for any muscle (p > .05). Perception of effort was higher in the Stroop session from the onset of the cycling task (p = .006), and the rate of increase in perception of effort was significantly higher in the Stroop than Control session (p = .031). Our findings do not support the hypothesis that mental fatigue alters motor control or increases central motor command, as no changes in muscle activation were detected. Conversely, our results reinforce the notion that prolonged cognitive engagement impairs endurance performance primarily through an increased perception of effort. Future research should consider combining surface electromyography with more sensitive neurophysiological techniques to investigate potential subtle changes in motor drive during dynamic, whole-body tasks under mental fatigue. Impact statementOur study confirms that mental fatigue induced by prolonged cognitive exertion impairs cycling endurance performance. By combining measurements of perceptual responses and multi-muscle surface EMG during the endurance task, we observed that the decreased endurance performance is related to an increased perceived effort in the presence of mental fatigue, not related to alterations in motor command.

Dance is a core form of human-environment interaction and a powerful medium for emotional expression, yet dancers are routinely exposed to environmental affective cues that may shape their movement. We tested whether a negative emotional context induced immediately before improvisation alters dance biomechanics. Twenty professional dancers performed two 3-min improvised dances. Between dances, they viewed either Neutral or Negatively valenced pictures from the International Affective Picture System (IAPS; 2 min 40 s, 5 s per image). Eye tracking verified attention to the visual stream. Mood was assessed at four time points (PT1-PT4) using the Brazilian Mood Scale (BRAMS), and full-body, three-dimensional kinematics were captured at 300 Hz using a 9-camera optoelectronic system (Qualisys) and processed to measure global movement amplitude and expansion. Negative IAPS exposure increased tension, depression, fatigue, and decreased vigor from PT2 to PT3. Biomechanically, the Negative Stimulus dancers showed a significant reduction in global movement amplitude after negative IAPS exposure, with reduced movement amplitude of the body extremities. In contrast, global movement expansion remained unchanged; that is, the extremities were not positioned closer or farther from the pelvis. Neutral images produced no mood change and no measurable modulation of movement amplitude or expansion. Together, these results support the hypothesis that improvised dance carries biomechanical signatures of the dancers current affective state, beyond the intended expressive content, and provide an automated motion-capture workflow for studying emotion-movement coupling in spontaneous dance. HighlightsNegative visual context shifted dancers mood toward negative affect Negative images reduced movement amplitude in improvised dance Movement expansion remained stable despite mood induction Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/711707v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@aeaacdorg.highwire.dtl.DTLVardef@14f9bf5org.highwire.dtl.DTLVardef@18805fcorg.highwire.dtl.DTLVardef@1411256_HPS_FORMAT_FIGEXP M_FIG C_FIG

An increasing number of studies highlight the role of saccadic remodulation in compensatory mechanisms following vestibular injury, and the reappearance of SHIMP saccades correlates with symptom improvement measured by the Dizziness Handicap Inventory (DHI). To investigate the influence of attentional processes and working memory on visuo-vestibular interaction, three independent but interrelated experiments were conducted. In the first two experiments, healthy subjects and patients with unilateral or bilateral vestibular deficits underwent vHIT in SHIMP mode and the Functional Head Impulse Test (fHIT), performed first separately and subsequently simultaneously. Mean latency and clustering of SHIMP saccades, together with Landolt C recognition rates, were analyzed. Differences between separate and combined protocols were assessed, and, in patients, correlated with symptom severity measured by the DHI, to determine whether the near-simultaneous execution of tasks mediated by shared parietal cortical substrates influenced performance. In the third experiment, vHIT in HIMP mode and fHIT were performed using separate and combined protocols to evaluate whether recognition-related cognitive load affected recovery saccade latency and clustering. Results suggest that visual recognition modulates visuo-vestibular interaction, supporting integrated dual-task protocols for ecological balance assessment and helping explain clinical discrepancies.

Objective: To develop the first inventory to measure psychosocial concerns about use of the non-preferred hand, toward the long-term goal of identifying the casual factors of left-right hand choices ("hand usage"). Design: Cross-sectional Setting: Online question battery Participants: 181 healthy adults Interventions; Not applicable Main Outcome Measures: Self-reported concerns about emotional and physical consequences of using the non-preferred hand. Results: Emotional and physical consequences reflected internally consistent categories (Cronbach's > 0.9) that were moderately correlated with each other ({rho} = 0.783 p = 0.002). Concerns were activity-dependent in each category ({rho} < 1x10-100). Reliability analysis and principal components analysis were used to reduce the battery to the 51-item Changed Hand Usage Concerns inventory, which encompasses everyday tasks and concerns about physical and emotional consequences of using the non-preferred hand in those tasks. Conclusions: Concerns about emotional vs. physical consequences of non-preferred hand use reflect coherent and internally consistent categories The Changed Hand Usage Concerns inventory allows assessment of psychosocial concerns about usage of the non-preferred hand for future attempts to manipulate hand usage via rehabilitation in patients with unilateral or asymmetric impairment.

The aim of this study was to improve our understanding of muscle contractions in the arm as a function of hand orientation for grasp. While there have been several reports on arm kinematics for reach and grasp movements, little has been done at the muscular level. To this end, we analyzed the modulation of shoulder, elbow and hand muscles for a reach and grasp task involving a target in either horizontal or vertical orientation. We hypothesized that unlike what has been observed for kinematics, at the muscular level we would see less correlation between the three muscle groups. A decoding approach with Machine Learning revealed adaptation patterns that were not visible using classical methods. Reach-and-grasp has traditionally been treated as being made of two components - the reach and the grasp components. Our dynamic decoding approach revealed a more complex picture with very different dynamics in the shoulder and elbow muscle groups during reach. All muscle groups showed peak capacity for predicting hand orientation before the start of grasp and followed the ubiquitous proximo-distal organization. The patterns of muscular modulation for hand orientation were strongly perturbed by the eyes closed and slow movement conditions, potentially decreasing the available degrees of freedom for adaptation.

Cybersickness is a major barrier to the widespread adoption of virtual reality (VR), yet its underlying neurophysiological mechanisms remain poorly understood. This study investigated the relationship between vestibulomotor weighting and cybersickness. Vestibulomotor weighting was quantified using electrical vestibular stimulation (EVS), with coherence and gain between the EVS input and medial-lateral center-of-pressure (ML-CoP) responses indexing the contribution of vestibular input to postural control. Thirty-eight healthy young adults (females n=21, males n=17) completed a standing VR rollercoaster task while receiving continuous stochastic EVS (0-25 Hz; {+/-}4.5 mA), with ML-CoP responses recorded using a force plate. Cybersickness was assessed using the Fast Motion Sickness Scale (FMS) and Simulator Sickness Questionnaire, and participants were classified as non-sick (FMS < 5), medium-sick (FMS [&ge;] 5), or high-sick (terminated the VR exposure early due to intolerance). Baseline EVS-ML-CoP coherence across 2.5-8 Hz was significantly greater in high-sick than in non-sick participants, indicating elevated vestibulomotor weighting in individuals who developed symptoms. During VR exposure, coherence declined over time in symptomatic groups (mean slope = -0.0027 for medium-sick), whereas non-sick participants maintained consistently low coherence (mean slope = -0.0005). Despite this reduction in vestibular coupling, postural sway increased in the high-sick group relative to the medium-and non-sick groups (+29% vs. -7% and -30% change in ML-CoP RMS, respectively), while vestibular-evoked response amplitude decreased (gain reduced by 64% across 2.5-3.5 Hz). These findings indicate that greater baseline vestibulomotor weighting was associated with increased susceptibility to cybersickness, whereas reductions in vestibular contributions during VR with EVS reflected adaptive reweighting that was insufficient to prevent instability and symptom progression. Together, the results highlight baseline sensory reliance as a key determinant of cybersickness vulnerability and suggest that reweighting during exposure plays a secondary, mitigating role. New and NoteworthyWe provide the first evidence that baseline vestibulomotor weighting predicts susceptibility to cybersickness in virtual reality and is dynamically reduced during exposure. Using electrical vestibular stimulation, we show that symptomatic individuals begin with greater reliance on vestibular input for postural control and progressively downweight these signals in response to sensory conflict.

Motor skills such as bicycle riding are considered robust and transferable across bicycle types. However, when the steering direction is inverted (reversed bicycle) control is disrupted to the extent that the bicycle cannot be ridden. With sufficient practice, the reversed bicycle can be learned, but this learning appears to produce impairment of normal bicycle riding suggesting modification of this long-established motor memory. Here we investigate the learning process of riding a reversed bicycle over four days of practice, while repeatedly assessing normal bicycle performance to measure any potential interference. Introduction of the reversed bicycle disrupted predictive control, reflected in a consistently increased time lag in the steering-roll coupling during reversed bicycle trials. This increase in delay suggests that predictive behavior in normal bicycle riding cannot be transferred to the reversed bicycle. With training, some participants successfully learned to ride the reversed bicycle by gradually reorganizing this coupling, whereas others failed to acquire this inverted coupling. Notably, even short-term exposure to the reversed bicycle interfered with normal bicycle riding, reducing distance ridden and increasing variability in steering rate. Together, we show that even a highly practiced whole-body motor skill is susceptible to rapid interference when control dynamics are altered.