Human Movement Science

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.

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.

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.

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;

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.

Purpose: To identify, through iterative user-centered design, the auditory biofeedback requirements and sound preferences supporting gait training in children with cerebral palsy (CP), and to determine which feedback variables, sound mappings, and sound types yield clinically viable and movement-interpretable paradigms. Methods: The iterative process spanned two prototype phases. Prototype A comprised seven paradigms demonstrated to two experienced physiotherapists (Workshop 1A). Two of these were subsequently discarded owing to poor sound-movement interpretability and two were modified. Six paradigms were added to Prototype B, demonstrated to four children, five parents, and one therapist (Workshop 1B) and two therapists (Workshop 2B). Data were analyzed using systematic text condensation. Results: Within-child sound preferences varied with energy level and sensory state on a given day. Sound-movement interpretability tended to suffer for paradigms with greater acoustic complexity (e.g. computer-generated music). Therapists endorsed a repertoire spanning both movement quality and movement quantity targets. Participants independently proposed paradigms rewarding restrained and controlled movement, a feedback category absent from the current prototype. Conclusions: Session-level calibration is preferable to fixed sound profiles, requiring real-time interface support for paradigm adjustment. Acoustic complexity must remain subordinate to movement-sound interpretability. Paradigms targeting movement restraint are a development priority unaddressed in the literature.

Mental rotation in 3D is a key cognitive skill involving dynamic spatial transformations, for which pronounced individual differences have been documented. Here we ask whether individual differences in 3D abilities can be explained by analogous differences in 2D abilities. 3D mental-rotation was assessed by the Vandenberg & Kruse Mental Rotation Test (3D-MRT) and examined for association with performance and underlying electrocortical mechanisms during a 2D letter rotation task. Participants (N=40) first completed the MRT and then performed a computerized 2-D letter rotation task in which they had to identify whether letters were oriented in a standard or a mirrored direction (parity judgment) when rotated at 0{degrees}, 60{degrees}, 120{degrees}, and 180{degrees} while EEG was recorded. Reaction times (RTs) and error rates increased with angular disparity. The angular disparity effect on RT was smaller for mirrored letters. Low, relative to high, 3D-MRT scoring participants showed more pronounced accuracy declines at higher rotation angles. An EEG Event Related Potential (ERP) known as the Rotation-Related Negativity (RRN) became more pronounced with increasing angular disparity. High 3D-MRT scores were associated with a stronger RRN response at central-parietal sites. In addition, the ERP-P3b wave was more pronounced at central-parietal sites for low 3D-MRT scorers, independent of angular disparity. It is concluded that 3D rotational ability is positively associated with 2D mental rotation performance, and more strongly with enhanced recruitment of neural visual-spatial cortical representations than with enhanced recruitment of more general cognitive resources.

Internal forward models predict the sensory consequences of motor commands; however, whether the anticipated availability of post-action feedback contributes to the precision of the action itself remains unknown. We manipulated the predictability of post-release visual occlusion in skilled basketball players. Participants performed three-point shots while wearing liquid-crystal shutter goggles. The study tested three conditions: a no-occlusion baseline, certain-occlusion condition in which players knew that their vision would be occluded at ball release in every trial, and random-occlusion condition in which they could not predict whether an occlusion would occur. Shooting accuracy declined in the certain-occlusion condition relative to the no-occlusion condition (49.2% vs 41.7%). The random-occlusion condition did not differ from the baseline (46.1%). Within the random condition, the accuracy in occluded trials were virtually identical to that in non-occluded trials (46.6% vs 46.2%), even though the immediate visual occlusion was the same as in the certain-occlusion condition. These results demonstrate that it is not the absence of post-action information per se that disrupts motor execution, but the prior certainty that action consequences will be unavailable. We interpret this finding as a prospective influence of anticipated consequence loss, whereby motor execution depends on whether the prediction-outcome loop remains closable.

PurposeThe para-cycling classification system aims to minimize the impact of impairments on competition outcomes with the help of scientific evidence. This study investigated the impact of unilateral and bilateral ankle immobility on cycling performance, quantified by the maximal average mechanical power output (AMPO) over one revolution relative to that without ankle immobility. MethodsTen well-trained non-disabled cyclists performed all-out 6-second sprints on a cycle ergometer at 120 rpm under three conditions: without ankle foot orthoses (AFOs), with 1 AFO and with 2 AFOs immobilizing the ankle joint(s). Mechanical power output, pedal forces, cycling kinematics and surface-electromyography were measured. Maximal AMPO; ankle, knee and hip joint AMPO; and the amount of muscle excitation were calculated. ResultsWith 1 AFO and 2 AFOs, respectively, maximal AMPO was 96% (p<0.05) and 91% (p<0.001) of that without AFOs (1188 W). The decrease in maximal AMPO with ankle immobilization was less than the decrease in ankle joint AMPO (126 W decrease with 2 AFOs; p<0.001), due to an increase in hip joint AMPO (69 W increase with 2 AFOs; p<0.05). The amount of muscle excitation was not significantly different across conditions. ConclusionsThese findings provide a first quantitative and mechanistic indication of the impact of ankle immobility on cycling performance, which may offer valuable evidence to support the development of an evidence-based para-cycling classification system.

Human pointing is often used to test whether dogs extract object-specific information from human communicative cues. However, above-chance responses in standard object-choice tasks do not by themselves distinguish between a referential interpretation, in which the gesture identifies a specific target, and an attentional interpretation, in which it primarily biases behaviour toward a broader spatial region. We addressed this issue using an asymmetric six-cup arrangement designed to separate coarse side guidance from exact cup localisation more clearly than a symmetric multi-cup design. Performance in domestic dogs was analysed using three measures: the probability of reaching the correct side, the probability of choosing the correct cup overall, and the probability of choosing the correct cup conditional on having first reached the correct side. The principal comparison involved three matched trial classes: the symmetric 3-vs-3 condition, 2-vs-4 trials with the baited cup on the 2-cup side, and 2-vs-4 trials with the baited cup on the 4-cup side. Descriptively, pointing trials exceeded matched no-point control trials more clearly for side selection than for overall cup choice. The clearest condition effect was observed at the level of side guidance. Dogs were most likely to reach the correct side when the baited cup was located on the 4-cup side of the unequal arrangement. Mixed-effects models confirmed a reliable group effect for side accuracy, whereas overall cup accuracy showed only a weaker and less robust condition effect, and within-side localisation revealed no reliable group difference once condition-specific chance baselines were taken into account. A complementary generative model comparison converged on the same conclusion: a referential-only model fit poorly, an attention-only model captured most of the grouped outcome structure, and a combined model yielded only a modest improvement. Dog point-following is therefore best understood as a layered process dominated by attentional guidance, with only limited additional target-specific localisation.

Singing is an innate human behaviour present across cultures and the lifespan. Despite lacking direct biological advantages, its ubiquity suggests that it is intrinsically rewarding. This research aimed to investigate the underlying factors that explain variability in sensitivity to deriving reward and enjoyment from natural singing in the general population. In Study 1 (n = 606), an initial pool of items describing daily, non-professional singing behaviours were administered to an international adult sample. Exploratory factor analysis revealed a unidimensional structure of 20 items with acceptable model fit, organized into five facets representing distinct domains of singing-related rewards: 1) pleasure and emotional evocation, 2) social singing reward, 3) singing frequency, 4) mood regulation through singing, and 5) inattentional singing during routine tasks. In Study 2 (n = 430), confirmatory factor analysis in a new sample supported this structure. When both samples were combined (n = 1036), the unidimensional model defined by these five facets showed acceptable to excellent goodness-of-fit indices, supporting the conceptualization of singing reward as a multidimensional construct with differentiated facets. This led to the Barcelona-Aarhus Natural Singing Engagement Questionnaire (BANSEQ), which demonstrated excellent reliability ( = .94) and population-level stability. Study 3 (n = 1036) tested the convergent validity of BANSEQ with measures of music reward and engagement and identified sociodemographic and psychological correlates across the five facets of singing reward. Overall, these findings characterize the sources of individual differences in the hedonic experience of natural singing and propose BANSEQ as a robust psychometric tool for its assessment in the general population.

Parkinsons Disease (PD) Motor Scores (MDS-UPDRS Part III) are quite noisy. This paper proposes a new methodology for processing these scores by first denoising the scores to enhance the underlying progression signal, and then conducting a high-dimensional analysis which does not sum the scores into a total movement score. The analysis gives novel insights into PD progression heterogeneity: it reveals that the heterogeneity is continuously variable rather than clustered into "subtypes" and that the variability is along two easily understood axes. This analysis also resolves some of the discrepancies in previously reported progression subtypes. Finally, the analysis reveals that patient-specific progression cannot be predicted from baseline using only MDS-UPDRS Part III scores.

Conventional diagonal stride skiing traditionally includes a glide phase, characterised by a period of relatively passive gliding on one ski. While the glide phase may take advantage of low ski-snow friction, it does not exhibit the same whole-cycle mechanical energy fluctuations seen in running or walking on foot. A new sub-technique, known as running style, substantially reduces the glide phase and may alter the role of elastic tissues, making the movement pattern more similar to uphill running on foot in its temporal organisation. We examined knee extensor and plantar flexor muscle-tendon behaviour in eight competitive skiers performing conventional diagonal and running techniques on a treadmill inclined at 10{degrees}. Using synchronised ultrasonography, 3D kinematics, ski forces and EMG, we quantified gastrocnemius medialis and vastus lateralis fascicle and muscle-tendon unit (MTU) dynamics in both the running (RUN) and conventional (CON) styles. Shorter glide and total cycle durations during RUN shifted MTU peak length and velocity earlier during the kick phase. Fascicles in both muscles operated at similar velocities across techniques, showing MTU-fascicle decoupling. Vastus lateralis fascicles shortened at higher absolute peak velocities than gastrocnemius in both conditions, while normalised velocities were similar. RUN increased preactivation and advanced EMG timing, while integrated EMG during the kick was lower compared to CON. These findings suggest that, despite large shifts in external mechanics between glide-based and more running-like skiing, elastic tissues may help stabilise fascicle behaviour and preserve a similar contractile strategy across muscles and techniques.

Mental imagery is known to be accompanied by autonomic responses, traditionally viewed as merely downstream consequences of imagery. Recent theoretical work has challenged this view, proposing that mental imagery requires the integration of cortical sensory representations with ascending interoceptive signals supplied by the autonomic nervous system. These two views make opposite predictions: if autonomic activity is only a consequence of imagery, then the responsiveness of the autonomic nervous system should not predict imagery vividness. If instead autonomic input shapes the generation of mental images, individuals with greater autonomic responsiveness should experience more vivid imagery. The present study tested these competing predictions by examining whether individual differences in cardiac vagal reactivity (indexed by the magnitude of HRV change in response to a paced breathing manipulation) predict self-reported visual imagery vividness. Imagery vividness was assessed using the Vividness of Visual Imagery Questionnaire (VVIQ) at a separate time point from the paced breathing protocol, ensuring that any observed relationship between cardiac vagal capacity cannot reflect autonomic activation driven by imagery itself. The key result was that cardiac vagal reactivity (indexed by RMSSD change normalized by mean R-R interval), significantly predicted higher VVIQ scores (r = .30, p = .031). These findings demonstrate that vividness of mental imagery is not exclusively central in origin but also shaped by the capacity of the autonomic nervous system to enter a high-parasympathetic state. Imagery thus likely involves bidirectional autonomic-cortical interaction, with descending pathways triggering the intention to generate an image and ascending interoceptive signals contributing to its generation.

Background: Quadriceps strength and landing mechanics are two modifiable factors associated with anterior cruciate ligament (ACL) injury risk. Collecting detailed biomechanical data is an arduous task. Identifying a relationship using more easily measured variables, such as quadriceps strength, would offer value for athlete counseling and injury prevention programs. Although quadriceps weakness has been associated with altered landing strategies in ACL-reconstructed (ACLR) individuals, this relationship is less clear in healthy athletes. Purpose: To investigate the association between isokinetic quadriceps strength and peak knee flexion angle during a vertical drop jump in healthy adolescent athletes. Study Design: Secondary analysis of previously collected data. Methods: Healthy adolescent athletes had their dominant leg quadriceps strength measured using an isokinetic dynamometer at 60{degrees}/s from 0-90{degrees} of knee flexion. Landing mechanics were assessed during a vertical drop jump using three-dimensional motion capture synchronized with force plates. Pearson correlation was used to evaluate the association between quadriceps strength and peak knee flexion angle during landing, with statistical significance defined as p < .05. Results: There was a weak negative correlation between quadriceps strength and peak knee flexion angle (p = .017, R = -.22 [-.04, -.38]), suggesting that stronger athletes achieved greater knee flexion angles. Discussion: Greater quadriceps strength was associated with increased peak knee flexion angles during landing; however, the weak correlation suggests that strength explains only a small portion of the variability in landing mechanics. These findings deviate slightly from prior literature in healthy populations but are consistent with studies demonstrating that greater quadriceps strength is associated with achieving greater peak knee flexion in ACLR patients. Accordingly, quadriceps strengthening should remain a key component of multifactorial ACL injury prevention programs.

Elite athletes exhibit sport-specific neural adaptations, yet it remains unclear whether such changes reflect general effects of training or the unique demands of individual sports. Skiing requires postural control and whole-body coordination under dynamically unstable environments, placing high demands on somatosensory processing and sensorimotor integration. The present study aimed to identify structural brain characteristics specific to elite skiers by comparing them with athletes from other sports disciplines and non-athletes. T1-weighted MRI data were analyzed using voxel-based morphometry in 13 skiers, 23 non-ski control athletes and 25 non-athletes. Whole-brain analysis comparing skiers with non-ski athletes revealed a significant cluster showing greater gray matter volume in skiers compared with non-ski athletes in the left postcentral gyrus, extending into the superior parietal lobule. The identified cluster primarily encompassed cytoarchitectonic Areas 2 and 5L. These regions are involved in higher-order somatosensory processing and multisensory integration. Importantly, region-of-interest analysis demonstrated that gray matter volume within this cluster was greater in skiers compared with non-ski athletes and non-athletes, with no difference between non-ski athletes and non-athletes. These findings highlight the relative prominence of structural adaptations within somatosensory-parietal networks, reflecting the unique integration of proprioceptive and other sensory information required for elite skiing. Overall, these findings provide evidence for sport-specific structural brain differences in elite athletes and highlight the importance of somatosensory and parietal regions in sensorimotor integration relevant to skiing. These findings may have implications for understanding neural markers of expertise and may inform future approaches to training and performance evaluation in skiing.