BACKGROUND:Random practice (RP) impairs acquisition performance but often enhances retention relative to blocked practice (BP), a pattern known as the contextual interference (CI) effect. Whether this benefit varies with baseline task performance remains unclear. OBJECTIVE:To examine whether baseline performance moderates the retention benefit of RP. METHODS:We conducted a secondary analysis of 70 right-handed participants who practiced a discrete sequence production (DSP) task under RP (n = 35) or BP (n = 35). Participants were classified within each practice group as having higher or lower baseline performance based on baseline response time. After excluding one median-ranked participant per group, subgroup analyses included 68 participants. Acquisition and retention at 5 min, 6 h, and 24 h were analyzed using repeated measures ANOVA and generalized estimating equations. RESULTS:BP produced better performance at the end of practice, whereas RP produced better 24-h retention at both levels of baseline performance. No significant BP-RP differences were detected at the 5-min or 6-h retention tests. The directional hypothesis that the retention advantage of RP would be greater in the subgroup with higher baseline performance was not supported. Secondary exploratory comparisons within the RP group did not detect significant retention differences between the two baseline-performance subgroups, but these comparisons were not equivalence tests. CONCLUSION:The 24-h retention benefit of RP was observed at both levels of baseline performance represented in this DSP sample. Prospective studies using continuous measures of baseline performance are needed to determine the generalizability and practical significance of this finding.
Movement variability can either facilitate or impede motor learning, dependent on the context of the learning environment. Most previous studies have evaluated reward- or reinforcement-based learning paradigms with a clear task goal and/or extrinsic feedback. We assessed the effect of movement variability when learning the kettlebell swing in a learner-regulated context, where participants relied solely on intrinsic feedback. We aimed to determine if high variability when first practicing the kettlebell swing enabled exploration of motor solutions that could be utilized to perform the movement under unique task demands. Twelve young adults (9F/3M, 20.53 (1.25) years) practiced the kettlebell swing over a one-week period. An uncontrolled manifold analysis was used to partition solution variability from error variability. Participants were separated into high and low solution variability groups based on their initial performance. At the end of the week, participants were challenged to perform the kettlebell swing with a water-filled kettlebell. A single trial motor equivalent analysis estimated the error variability for each repetition. Results indicated that participants with high relative solution variability during their early practice were able to perform the water-filled kettlebell swing with less errors. Higher solution variability was beneficial to acquiring a transferable kettlebell swing, but only when error variability was low. These findings suggest that high error variability might reduce an individual's ability to perceptually distinguish solutions from errors. Extrinsic feedback should help separate solutions from errors in order to construct a transferable motor skill.
The main objective of this study was to determine the extent to which a virtual reality-based relay simulator can optimize the anticipation skills of novice relay runners. The simulator integrated a head-mounted display (HMD) to immerse participants in a life-sized virtual stadium, requiring them to physically trigger their start based on the approaching virtual incoming runner. A learning protocol was used to compare the respective effectiveness of a self-adaptive method, which progressively adjusts the task difficulty level to the learner's performance, and a method imposing the same progressive reduction in task difficulty on all participants. The results demonstrate a significant improvement in the anticipatory behavior of novice relay runners (e.g., reduction of absolute error from ∼131 ms to ∼58 ms). While both methods yield equivalent learning improvements, the self-adaptive approach provides a foundational benefit, as its prior deployment is essential for the subsequent implementation of the prescriptive method. Moreover, it not only allows learners to be confronted with the most appropriate level of difficulty throughout the learning process, but also adapts as closely as possible to each learner's needs. The precise impact of the learning methods on the processes underlying athletes' anticipation behavior is discussed, and the importance of testing the hypothesis of learning transfer to real-world situations is emphasized.
INTRODUCTION/PURPOSE:Curved running presents specific mechanical demands on the musculoskeletal system and relies on a multi-level coordination of the lower limb to regulate efficient and precise movements. When a subject runs on a curve, the velocity of the body's centre of mass must be deflected laterally and the body must rotate along a vertical axis to match its orientation to the new direction of movement. This study observed the joint and neuromuscular coordination adjustments of the inner and outer limbs during curved running and its comparison to straight-line running. We supported the hypothesis that the inner and outer limbs would adopt distinct functional roles to accommodate lateral forces. METHODS:We recorded the ground reaction force, kinematic motion and muscular activity of eleven recreational male runners on two different radii of curvature at speeds ranging from 7 to 19 km h-1. The joint coordination in frontal and sagittal planes, and muscular activity and spinal motoneuron output were analysed. Each lower limb played a distinct role in curved running, and coordination was limb specific with key traits separating either limb. RESULTS:The inner limb primarily managed lateral redirection of the body, relying on increased joint compliance and enhanced muscular activation in the hip abductors to accommodate the greater lateral forces. In contrast, the outer limb contributed more to propulsion and stabilisation to drive forward motion. CONCLUSION:This study's results provide insight into how humans modulate limb mechanics and coordination to maintain stability and performance in curved trajectories, with potential applications in sports and rehabilitation.
INTRODUCTION:Older adults with poor mobility often experience concerns about falling (CAF), which may increase their risk for mental and physical health declines. While prior research links CAF to poorer cognition, gait, and psychological factors in healthy older adults, it is unclear whether these associations hold in those with mobility limitations. This study aimed to identify predictors of high CAF in older adults with poor mobility. METHODS:Eighty-five adults aged ≥65 years (low/moderate CAF: n = 40, 77.6 ± 7.3 years, 65.0% female; high CAF: n = 45, 81.8 ± 8.6 years, 53.3% female) with self-reported poor mobility and no neurological conditions from the community and residential care settings completed assessments of cognition, depression, perceived health status, gait speed, and functional strength. Participants reported their CAF using the 16-item Falls-Efficacy Scale-International (FES-I); previously defined cut-points were used to differentiate between participants with low/moderate concerns (FESI: 16-27 points) and high concerns (FESI: 28-64 points). RESULTS:Binary logistic regression (adjusting for age, sex, and education) showed that higher MoCA scores [OR = 1.51, CI = 1.11,2.06], greater depression [OR = 3.18, CI = 1.67,6.04], slower gait speed [OR = 0.005, CI ≤0.00,0.18], and slower Sit to stand score [OR = 0.57; CI = 0.33,0.98] predicted high CAF. The model's classification accuracy was 80.7% (χ2(8) = 52.01; R2 = 0.62, p < 0.001). CONCLUSION:While greater depression, slower gait, and reduced strength predicted high CAF - as in prior research - better cognition also did, possibly reflecting greater fall risk awareness without the physical capacity to respond. These findings may inform screening in this high-risk group.
What kinematic features drive emotion encoding (production or expression of emotion by an expressor) and decoding (perception, interpretation, or recognition of that emotional information by a receiver) in human full-body movement? We used upper-body sensor data from the EMOKINE full-body dataset [Christensen, et al. (2024). EMOKINE: A software package and computational framework for scaling up the creation of highly controlled emotional full-body movement datasets. Behavior Research Methods, 56(7), 7498-7542.], to perform a pre-registered, secondary data-analysis, examining this question. Previous work using EMOKINE showed that human observers (N = 132) identify the dancer's intended emotions in full-body movements above chance-level. Yet, no analyses have been presented with regards to which kinematic features contributed to the dancer's encoding of emotional intention, and observers' correct decoding of encoded emotions. The present study examined the role of four of the 12 kinematic features provided with the EMOKINE dataset (acceleration, dimensionless jerk, head tilt, limb contraction), specifically for the upper-body. Finally, in an exploratory analysis, the effect of intended emotional expressivity and kinematic features on aesthetic judgment was examined. Upper-body acceleration, head tilt, and dimensionless jerk were the strongest predictors of emotion encoding, while decoding relied on the dancer's intended emotion, on dimensionless jerk and limb contraction. Aesthetic judgments were only weakly related to upper-body kinematics and depended largely on the dancer's intended emotion at encoding. Results illustrate a possible dissociation between expressive and aesthetic impression, and suggests that recognition and aesthetic responses may draw on partially distinct cognitive mechanisms.
In sequential motor tasks, people reuse prior motor plans to reduce planning cost, causing a persistence of the prior posture. This persistence, termed motor hysteresis, is indicative of planning efficiency. To date, research on motor hysteresis has focused narrowly on reaching movements. However, hysteresis should also apply to full-body movements if it constitutes a general principle of planning efficiency. To test this, we asked participants to perform a binary full-body posture selection task: going over or ducking under a horizontal bar of varying height. Bar height was varied in ordered sequences to induce hysteresis, and binary decision data was recorded. To ascertain whether full-body tasks could be conducted in a virtual reality (VR) environment without compromising scientific validity, we replicated the task in VR with a second group of participants. Results showed that participants went over lower bar heights and ducked under higher ones. The critical height shifted with order. However, the shift direction indicated an inverse hysteresis effect. This inverse hysteresis was replicated in the second participant group in the virtual environment. Here, participants were more cautious in their decisions and switched to ducking under at lower heights. The similarity of the decision-making behavior across environments lends support to the feasibility of using VR to study full-body movements. Nevertheless, it seems advisable to validate the gained insights in a real environment. The inverse hysteresis effect found in the current study has previously been observed in perception research, where it was interpreted as repetition suppression. Our findings suggest that repetition suppression may also apply to motor planning, particularly when mechanical costs are high, like in full-body movements.
Parkinson's Disease (PD) leads to significant deficits in the physical execution of movements. These deficits may stem in part from impaired processing of action representations, which are integral to the planning, monitoring, and execution of voluntary movement. Action representations can be examined using movement imagery. Here we examine whether PD affects movement imagery at the level of behaviour and neural activity. In particular, 20 people with PD and 20 controls completed a movement imagery task while electroencephalographic activity was recorded. Our data analysis focused on activity in the mu rhythm (8-14 Hz) as suppression in this rhythm is associated with sensorimotor network activation and the theta rhythm (3.5-7 Hz), which is proposed to support sensorimotor integration. The PD group was significantly less accurate when imagining successive movements as compared to controls. Successful trials were accompanied by more mu suppression as compared to unsuccessful trials in the control group, but no such effect was observed in the PD group. This result suggests that PD participants relied less on the sensorimotor network to imagine the target movements. Additionally, the PD group exhibited significantly more theta activity over the temporo-occipital region. This increase in theta oscillations may represent increased activity in the extrastriate body area. Taken together, the findings of the present study indicate that impaired processing of action representations may contribute to the motor deficits observed in PD.
We investigated the effects of progressive unilateral hand load carriage on the predictive control of dynamic balance during walking in older adults with and without a recent history of falls. Thirty-one community-dwelling older adults (15 fallers, 16 non-fallers) walked at their preferred speed under six randomized conditions: no load and carrying unilateral dumbbell loads corresponding to 2-10% of body mass. Whole-body kinematics and bilateral gluteus medius electromyography were recorded. Mediolateral margin of stability (MoS) was computed using the extrapolated center of mass, both with and without inclusion of the carried load in the center of mass (COM) calculation, to probe predictive control mechanisms. When the carried load was excluded from the calculation, MoS gradually increased on the ipsilateral side and decreased on the contralateral side as the load increased. In contrast, when the load was included, MoS remained stable across all conditions. This stability was maintained through systematic, load-dependent postural adjustments, including contralateral tilt of the head and thorax and increased abduction of the contralateral shoulder. At higher load levels, these changes were accompanied by increased activation of the contralateral gluteus medius. Load carriage did not affect spatiotemporal walking parameters but reduced the shoulder range of motion differently between fallers and non-fallers. Overall, these findings indicate that predictive control of dynamic balance was preserved despite increasing unilateral loads and was unaffected by fall history. MoS maintenance was accompanied by systematic adjustments in upper-body orientation rather than by changes in lower-limb gait characteristics.
This study investigated the learning and transfer of graphomotor skills in children (7-10 years) and adults using a pseudo-letter copying task on a graphic tablet, which enabled both quality and kinematic analyses of handwriting. We created a scale to assess the quality of written production and analyse velocity, fluency, and the number of stops to assess the writing process. With a varied training of limited intensity, we hypothesized that children and adults would perform similarly during the learning phase, but that younger children would have more difficulty transferring their learning. Results showed that children as young as 7 reached adult-like performance during the learning phase but struggled to transfer these skills, particularly when reusing complex motor sequences (chunks). Seven-year-olds displayed decreased letter quality in two transfer tasks, whereas 8- and 9-year-olds maintained good quality but at the cost of reduced fluency and increased number of stops, suggesting higher cognitive demands. By contrast, 10-years-old children and adults were able to efficiently transfer after a short learning phase, as demonstrated by their good performances in both transfer tasks. This suggests that from the age of 10, child can form sufficiently abstract representations to enable effective transfer. These findings indicate that studying transfer, rather than acquisition alone, provides critical insights into the developmental trajectory of graphomotor skills, and that digital tablets offer valuable tools for assessing underlying motor processes.
Observational learning benefits are reported after watching "learning" models. Reasons for benefits are mostly speculative and the reliability of effects compared to watching correct models is relatively poor. Variation in what an observer sees when watching a learner is one proposed condition for a beneficial effect. Another is related to seeing errors, which engage error detection and correction processes. To date, variable versus errorful conditions have not been distinguished. In a pre-registered design, three groups (n = 34/group) practiced putting a golf ball to the centre of a grid and returned the next day to test for retention and transfer. Practice involved alternating blocks of watching putting videos (8 blocks of 20 trials), with physical practice, without and with outcome feedback (8 blocks, 10 trials each). Self-predictions were captured in no-feedback trials. Two "variable" groups watched a model putt to different corners of the grid, with instructions conveying intended "hits" (variable-correct) or unintentional "misses" (variable-error). A third group watched constant correct putts. Watching variable demonstrations caused more putting variability in practice and accuracy benefits in transfer, compared to constant. However, there were no group differences in retention, nor any error-group related differences. Although watching errors did not impact directional biases or facilitate putting accuracy as expected, it improved self-estimations of outcomes (i.e., error detection related to prediction of sensory effects). These data suggest that variability and errors in demonstrations have small, yet different effects on motor learning, with variability improving generalizability and errors contributing to improved feedforward predictions.
This study examined the role of predictive processing mechanisms in naturalistic visuomotor skill learning. We investigated whether the acquisition of an interceptive skill was characterised by encoding and using learned probabilistic associations. Forty-five participants were randomly assigned to either an intervention or control group and practiced intercepting bouncing balls in virtual reality across two sessions. Only the intervention group received probabilistic visual cues - specifically, ball and room colours - that signalled likely bounce trajectories, offering an opportunity to learn and exploit these associations. We assessed task performance (interception rate, return accuracy), anticipatory gaze behaviour (predictive fixations and gaze tracking), and pupillary responses to unexpected outcomes. Participants in the training group demonstrated more predictive gaze strategies and physiological surprisal responses to probabilistically unlikely bounce outcomes post training. These findings suggest that encoding probabilistic environmental cues can contribute to effective visuomotor control. The results offer novel evidence for the role of top-down prediction and contextual modulation in visuomotor skills, with implications for training and expertise development in sport. More broadly, this work contributes to an alternate account of expertise as the capacity to encode and exploit environmental regularities through predictive mechanisms.
Recreational screen time in early school-aged children is a growing public health concern, with implications for sleep, physical activity, and adiposity. While prior research has identified individual and environmental correlates of screen time, few studies have modeled these influences within a developmental and policy-relevant framework. Thus, this study aimed to examine behavioral, physical, and demographic correlates of categorized screen time among Portuguese children aged 6-10 years. A complete-case subsample of 307 Portuguese children (mean age: 8.5 ± 1.1 years) participated in a cross-sectional analysis. Multinomial logistic regression was employed to examine associations between parent-reported screen time categories and a multi-domain set of behavioral, sleep, anthropometric, and motor competence variables, including device-based measures of sedentary time, moderate-to-vigorous physical activity, and sleep parameters, as well as anthropometric indicators (body mass index, waist circumference) and motor competence. Higher sedentary time significantly increased the odds of belonging to higher screen time categories (OR = 1.13), while longer total sleep time showed a small inverse association (OR = 0.99). Higher sleep efficiency was also associated with greater screen time (OR = 1.07), which may reflect more consolidated sleep patterns in the context of high screen use. Sex was also independently associated with screen time category membership, with girls less likely to exhibit high screen time (OR = 0.41). These findings reinforce the interdependence of daily movement behaviors and highlight specific sleep and sedentary profiles linked to excessive screen time. The results support the application of the 24-h movement framework in public health strategies and underscore the importance of sex-sensitive, context-specific interventions targeting after-school routines and media environments.
The performance of targeted reaching movements can be influenced by speed-accuracy demands such as the distance to the target and biomechanical demands based on target direction. Therefore, task difficulty for whole-arm reaching movements may be influenced by both speed-accuracy and biomechanical demands. This study aimed to examine the interaction of biomechanical factors such as directional inertia and joint movement demands based on variations in target direction and speed-accuracy demands based on variations in target distance on three-dimensional reaches that required endpoint accuracy. Ten right-handed, young adults (5 female, 27.1 ± 3.4 yrs) completed targeted reaches to inter-target combinations in a circular array (Center-Out & Out-Center, 10 cm reach distance, index of difficulty (ID) = 2.78; Long/Diameter, 20 cm reach distance, ID = 3.78) with both the dominant and non-dominant arms in a single session. As predicted by Fitts' Law, movement time increased with increased target distance in both arms (p < 0.05). However, movement times for reaches with the same ID varied with reach direction in both arms (p ≤ 0.05). Directional effects were also found for peak acceleration and joint excursion (p < 0.01) in a manner suggesting that both inertia and joint coordination demands influenced movement time for reaches with the same speed-accuracy demands. In the non-dominant left arm, movement time varied based on start position (p < 0.05), suggesting that the initial shoulder-elbow configuration influenced reach times. Future studies should consider the effects of inertia and limb coordination demands in addition to ID when incorporating and comparing multi-directional reaches in experimental designs.
Pre-performance routines (PPR) are widely used to optimize athletes' attentional, emotional, and physiological readiness before action. Motor imagery (MI), the mental simulation of an action, is an important part of PPR. Yet, how the content of MI within these routines shapes performance remains unclear. This study examined the functional effects of distinct MI types embedded in PPR on subsequent weightlifting performance. A sample of 120 national-level CrossFit® athletes performed clean and snatch lifts under four randomized conditions following a baseline recording session: Motivational General MI (MG-MI) focusing on physiological activation, Motivational Specific MI (MS-MI), Cognitive Specific MI (CS-MI) involving imagery of technical skills, and a control condition without imagery. Power output, barbell trajectory, and self-reported levels of motivation, fatigue, and difficulty were recorded. Results revealed that MG-MI and MS-MI significantly enhanced power and technical accuracy compared to all other conditions (p < 0.001), whereas CS-MI markedly impaired performance (p < 0.001). Subjective measures were unaffected, excluding motivational or fatigue-related influence. These results demonstrate that the functional direction of MI may determine its short-term efficacy within PPR. CS-MI involving imagery of technical skills might interfere with motor fluency through excessive conscious control. By delineating how CS-MI and both MG-MI and MS-MI components differentially affect expert motor behavior, this study offers evidence-based guidance for designing more effective PPR in sports.
To determine how training status influences shoulder and elbow coordination in the transverse plane during the badminton forehand drive, using vector coding and coupling angle mapping. Fifteen trained and fifteen untrained people participated. Motion capture recorded upper limb kinematics during forehand drives. Shoulder internal/external rotation and elbow pronation/supination angles were obtained via inverse kinematics. Data were trimmed from maximal shoulder external rotation to shuttlecock impact and analyzed with vector coding to compute coupling angles and classify eight coordination categories, followed by coupling angle mapping. Range of motion was computed for shoulder, elbow, and wrist. Group differences were tested using multivariate and univariate analyses, and principal component analysis summarized phase counts. Trained participants showed larger upper limb range of motion across several planes and distinct coordination sequences that began predominantly in Anti-Phase and transitioned to In-Phase near impact, with shoulder internal rotation frequently dominant. Untrained participants more often began In-Phase and ended Anti-Phase, indicating a different inter joint sequencing pattern. Phase count analysis and the first principal component differentiated groups, with trained participants showing more In-Phase Shoulder Internal Rotation Dominancy and fewer distal dominant phases. Patterns were visualized with coupling angle mapping. Coordination of the shoulder and elbow in the transverse plane differs by training status during the forehand drive. Trained participants use a strategy that separates and then synchronizes joint motions, favoring proximal dominance to support efficient kinetic transfer and racket acceleration. These findings provide a biomechanical basis for coaching that develops In-Phase shoulder-led coordination while acknowledging variability.
Chronic ankle instability (CAI) is characterized by recurrent episodes of sprain and delayed activation of the fibularis longus, which compromises dynamic ankle stabilization. However, whether delays in muscle reaction time occur uniformly across its neuromuscular compartments or follow a region-specific pattern remains unclear. This study aimed to compare global reaction time and determine whether this temporal response differed between the anterior and posterior regions, while also characterizing the spatial distribution of fibularis longus activation during sudden ankle inversion in individuals with CAI and healthy controls. Fifteen individuals with CAI and fifteen healthy controls (No-CAI) were recruited. Participants performed a sudden 30° ankle inversion task on a custom-built platform, during which high-density surface electromyography (HD-sEMG) was used to assess regional reaction time and spatial activation of the fibularis longus through the displacement of the activation barycenter. No significant interaction was observed between region and group (p = 0.7826). However, the CAI group displayed a significantly longer reaction time (MD = -41.49 ms; 95% CI = -50.15 to -32.83; p = 0.0001) and a significant anterior shift of the barycenter during destabilization (MD = -0.80 mm; 95% CI = -1.46 to -0.13; p = 0.0209) compared to controls. These findings suggest that CAI is characterized by a global delay in fibularis longus activation and a task-dependent spatial redistribution. The anterior shift in activation may reflect a compensatory strategy to maintain eversion torque in mechanically disadvantageous positions. These insights may inform neuromuscular rehabilitation strategies targeting both temporal and spatial aspects of muscle activation.
