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Objective: Four web-based experiments investigated flexibility of disembodiment of a virtual object that is no longer actively controlled. Emphasis was on possibilities to modify the timescale of this process. Background: Interactions with virtual objects are commonplace in settings like teleoperation, rehabilitation, and computer-aided design. These objects are quickly integrated into the operator's body schema (embodiment). Less is known about how long such embodiment lasts. Understanding the dynamics of this process is crucial because different applied settings either profit from fast or slow disembodiment. Method: To induce embodiment, participants moved a 2D virtual hand through operating a computer mouse or touchpad. After initial embodiment, participants either stopped or continued moving for a fixed period of time. Embodiment ratings were collected continuously during each trial. Results: Results across all experiments indicated that embodiment for the virtual hand gradually increased during active use and gradually decreased after stopping to use it. Disembodiment unfolded nearly twice as fast as embodiment and showed a curved decay pattern. These dynamics remained unaffected by anticipation of active control that would be required in an upcoming task. Conclusion: The results highlight the importance of continuously experiencing active control in virtual interactions if aiming at inducing stable embodiment of a virtual object. Application: Our findings suggest that applications of virtual disembodiment such as virtual tools or interventions to affect a person's body representation critically depend on continuous updating of sensorimotor experience. However, if switching between virtual objects, for example, during teleoperation or video gaming, after-effects are unlikely to affect performance. [ABSTRACT FROM AUTHOR]

Objective: This review surveys the literature on sensorimotor challenges impacting performance in laparoscopic minimally invasive surgery (MIS). Background: Despite its well-known benefits for patients, achieving proficiency in MIS can be challenging for surgeons due to many factors including altered visual perspectives and fulcrum effects in instrument handling. Research on these and other sensorimotor challenges has been hindered by imprecise terminology and the lack of a unified theoretical framework to guide research questions in the field. Method: We conducted a systematic survey of the MIS literature, focusing on studies investigating sensorimotor challenges affecting laparoscopic performance. To provide a common foundation for cross-study comparisons, we propose a standardized taxonomy that distinguishes between different experimental paradigms used in the literature. We then show how the computational motor learning perspective provides a unifying theoretical framework for the field that can facilitate progress and motivate future research along clearer, hypothesis-driven lines. Results: The survey identified diverse sensorimotor perturbations in MIS, which can be effectively categorized according to our proposed taxonomy. Studies investigating monitor-, camera-, and tool-based perturbations were systematically analyzed, elucidating their impact on surgical performance. We also show how the computational motor learning perspective provides deeper insights and potential strategies to mitigate challenges. Conclusion: Sensorimotor challenges significantly impact MIS, necessitating a systematic, empirically informed approach. Our proposed taxonomy and theoretical framework shed light on the complexities involved, paving the way for more structured research and targeted training approaches to enhance surgical proficiency. Application: Understanding the sensorimotor challenges inherent to MIS can guide the design of improved training curricula and inform the configuration of setups in the operating room to enhance surgeon performance and ultimately patient outcomes. This review offers key insights for surgeons, educators, and researchers in surgical performance and technology development. [ABSTRACT FROM AUTHOR]

AbstractNumerous devices are being developed to assist visually impaired and blind individuals in performing everyday tasks such as reaching out to grasp objects. Considering that the size, weight, and cost of assistive devices significantly impact their acceptance, it would be useful to know how effective various types of guiding information can be. As an initial exploration of this issue, we conducted four studies in which participants with normal vision were visually guided toward targets. They were guided by information about the direction to the target, and either about the distance to the target or about the time required to reach the target. We compared participants’ performance when provided with different amounts of each of these kinds of information. We found that restricting information about the distance from the target or the time it would take to reach the target to only a few possible values does not affect performance substantially. Restricting information about the direction to the target to only a few possible values appears to be more detrimental, but the disadvantage of having few possible directions can be mitigated by combining values in multiple directions. These findings can help optimize haptic presentations in assistive technology. [ABSTRACT FROM AUTHOR]

Featured Application: This study provides valuable insights into the specific muscle contributions required for adopting and maintaining various postures during indoor skydiving. These findings are essential for preventing joint and muscle overloading in novices and for preparing elite practitioners for competitive choreography. Furthermore, a novel index, termed NeLo, has been introduced to provide quantitative information about muscle excitation when several muscles are concurrently investigated. Such an index can be categorized into general, regional, and functional standpoints and holds potential for applications across several sport science fields where a quantitative contribution of various muscle groups to different tasks must be assessed. The evolution of indoor skydiving from military origins to a globally recreational pursuit has attracted individuals without prior specific training, exposing them to the heightened risk of muscle–joint injuries associated with indoor skydiving. This study aims to assess the muscular excitation patterns in highly skilled instructors to determine the optimal activation strategies for preventing musculoskeletal injuries. Nine expert indoor skydiving instructors (M/F: 8/1; age 31 ± 7 years; body mass: 70.5 ± 11.1 kg; stature: 1.74 ± 0.09 m) were enrolled. The surface electromyographic signal was recorded on the anterior deltoid, AD; posterior deltoid, PD; pectoralis major, PM; latissimus dorsi, LD; rectus abdominis, Rabd; erector spinae, ES; rectus femoris, RF; and biceps femoris, BF for each position: PRONE, SUPINE, SIT, and head-down (HD). A synchronous heart rate was recorded to assess the cardiac engagement. The neuromuscular load (NeLo), representative of the excitation amplitude of a muscle set, was determined for each position across different body regions. PRONE and SUPINE were the least demanding in terms of cardiac engagement (67 ± 6 and 85 ± 8 bpm, respectively) and exhibited the lowest neuromuscular excitation (24 ± 10 and 24 ± 8% Max, respectively). By contrast, HD exhibited the highest cardiac (127 + 18 bpm) and neuromuscular (71 + 11% Max) engagement and particularly in the lower-trunk and lower-limbs muscles. SIT predominantly engaged upper-trunk and shoulder muscles. The findings indicate the significant engagement of the musculature surrounding the shoulder joint and that responsible for lower-trunk stabilization in maintaining the investigated positions. A targeted training regimen on strengthening these muscles is advised before practicing indoor skydiving to prevent shoulder joint injuries or lower back muscle overloads. [ABSTRACT FROM AUTHOR]

This study aimed to first investigate changes in electromyography (EMG) patterns after multilevel surgical treatment in patients with cerebral palsy (CP) and then to assess the connection between the measure of EMG and motor control indices and surgery outcomes. We analyzed retrospective EMG and gait data from 167 patients with CP before and after surgery and from 117 typically developed individuals as a reference group. The patients underwent at least one soft tissue surgery on their shank and foot muscles. Using Repeated Measures ANOVA, we examined the norm-distance (ND) of the kinematics, kinetics, and EMG patterns, in addition to the Kerpape-Rennes EMG-based Gait Index (EDI), EMG Profile Score (EPS), and Walking Dynamic Motor Control Index (DMC) before and after surgery. Participants were divided into different response groups (poor, mild, and good gait quality) according to their pre- and post-treatment Gait Deviation Index (GDI), using the K-means-PSO clustering algorithm. The gait and EMG indices were compared between the responders using the nonparametric Mann–Whitney test. The ND for all kinematics and kinetics parameters significantly improved (p-value < 0.05) after the surgery. Regarding EMG, a significant reduction was only observed in the ND of the rectus femoris (p-value < 0.001) and soleus (p-value = 0.006). Among the indices, DMC was not altered post-operatively (p-value = 0.88). Although EDI and EPS were consistent across responders with a similar pre-treatment gait, a higher DMC was significantly associated with a greater improvement, particularly in patients with poor gait (p-value < 0.05). These findings indicate systematic changes in the EMG of patients with CP following surgery, which can also be demonstrated through indices. DMC is a measure that can potentially serve as a partial predictor of outcomes, particularly in patients with poor pre-operative gait. Future research should investigate the effects of different surgical strategies on the improvement of these patients. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated that engaging in graphomotor activity for creating graphemes can enhance their subsequent visual discrimination. This suggests a positive influence of the motor system on visual learning. However, existing studies have emphasized the dominant hand, which is superiorly dexterous in fine-motor movements. This near-exclusive focus prompts the inquiry of whether the observed perceptual facilitation is a general characteristic of the motor system, or specific to pathways controlling the skilled over-trained dominant hand. Furthermore, the mechanistic underpinning of visual facilitation from graphomotor training (i.e., the individual contribution of motor activity, temporal evolution of the visual trace, variability of visual output) remain unclear. To address these questions, we assessed visual discrimination capabilities of healthy right-handed participants (N = 60) before and after graphomotor or visual training. Contrary to our initial expectation, graphomotor engagement with the non-dominant hand did not yield additional benefits to visual learning beyond those attainable through visual training alone. Moreover, graphomotor training with the non-dominant hand resulted in visual discrimination improvements comparable to those of dominant hand training, despite the inherent differences between hands in motor performance and in the amount of improvement in shape tracing throughout training. We conclude that the motor components of graphomotor activity may not be critical for visual learning of shapes through tracing activity. Instead, our results are in agreement with the symbolic theoretical account, suggesting that basic shape features required for discrimination can be acquired through visual inspection alone, providing a perspective on the improvements observed in prior studies. [ABSTRACT FROM AUTHOR]

Although the dominant hand has been shown to have performance advantages over the nondominant hand, these interlimb differences have found to be dependent on task and biomechanical demands. The dynamic dominance hypothesis suggests that the left hemisphere is specialized for the control of intersegmental dynamics while the nondominant right hemisphere is specialized for postural control, in right-handers. In a real-world scenario, however, cognitive challenges might be expected to modulate these specialized behaviors. Therefore, we hypothesized that with increased cognitive load, lateralized motor control processes would become even more asymmetrical. We recruited 16 right-handed older adults (11 females, 5 males; 65.88 yr ± 1.99 SE) to perform 170 trials of a unilateral reaching task with each of their hands on the Kinereach system. In each trial, participants rapidly memorized pictorial instructions before identifying and reaching for the correct object on a screen. The complexity of the task increased over the course of the experiment. Our results demonstrated higher reaction times in the right than in the left hand (P = 0.0004). Movements became increasingly curved and erroneous with cognitive load, but interlimb differences in movement quality were absent. We found higher joint cocontraction in the right than in the left arm (P < 0.05), but these differences were unaffected by cognitive load. Hence, with the addition of a cognitive load, we observed asymmetries in reaction time but not in joint coordination or movement quality. This highlights the role of cognitive load in modulating limb/hemisphere specializations for control processes. NEW & NOTEWORTHY: Although we know that motor control processes are lateralized to each hemisphere, the role of cognitive load on these specialized processes is undefined. We designed a unique task that incorporates a cognitive challenge to a typical reaching movement to examine how cognitive load affects limb asymmetries in motor control. In a group of typical older adults, we demonstrated interlimb asymmetries in reaction time but not in joint coordination or movement quality. [ABSTRACT FROM AUTHOR]

Successful reactive balance control requires coordinated modulation of hip, knee, and ankle torques. Stabilizing joint torques arise from neurally-mediated feedforward tonic muscle activation that modulates muscle short-range stiffness, which provides instantaneous "mechanical feedback" to the perturbation. In contrast, neural feedback pathways activate muscles in response to sensory input, generating joint torques after a delay. However, the specific contributions from feedforward and feedback pathways to the balance-correcting torque response are poorly understood. As feedforward- and feedback-mediated torque responses to balance perturbations act at different delays, we modified the sensorimotor response model (SRM), previously used to analyze the muscle activation response, to reconstruct joint torques using parallel feedback loops. Each loop is driven by the same information, center of mass (CoM) kinematics, but each loop has an independent delay. We evaluated whether a torque-SRM could decompose the reactive torques during balance-correcting responses to backward support surface translations at four magnitudes into the instantaneous "mechanical feedback" torque modulated by feedforward neural commands before the perturbation and neurally-delayed feedback components. The SRM accurately reconstructed torques at the hip, knee, and ankle, across all perturbation magnitudes (R2 > 0.84 and VAF > 0.83). Moreover, the hip and knee exhibited feedforward and feedback components, while the ankle only exhibited feedback components. The lack of a feedforward component at the ankle may occur because the compliance of the Achilles tendon attenuates muscle short-range stiffness. Our model may provide a framework for evaluating changes in the feedforward and feedback contributions to balance that occur due to aging, injury, or disease. NEW & NOTEWORTHY: Reactive balance control requires coordination of neurally-mediated feedforward and feedback pathways to generate stabilizing joint torques at the hip, knee, and ankle. Using a sensorimotor response model, we decomposed reactive joint torques into feedforward and feedback contributions based on delays relative to the center of mass kinematics. Responses across joints were driven by the same signals, but contributions from feedforward versus feedback pathways differed, likely due to differences in musculotendon properties between proximal and distal muscles. [ABSTRACT FROM AUTHOR]

Movement planning consists of several processes related to the preparation of a movement such as decision making, target selection, application of task demands, action selection, and specification of movement kinematics. These numerous processes are reflected in the reaction time, which is the time that it takes to start executing the movement. However, not all the processes that lead to motor planning increase reaction time. In this paper, we wanted to test whether tuning the control policy to task demands contributes to reaction time. Taking into account that the tuning of the control policy differs for narrow and wide targets, we used a timed response paradigm to track the amount of time needed to tune the control policy appropriately to task demands. We discovered that it does not take any time during motor planning and even that it can occur indistinguishably during motor planning or during motor execution. That is, the tuning the control policy was equally good when the narrow or wide target was displayed before than when it was displayed after the start of the movement. These results suggest that the frontier between motor planning and execution is not as clear cut as it is often depicted. NEW & NOTEWORTHY: Movement preparation consists of different processes such as target selection and movement parameters selection. We investigate the time that it takes to tune movement parameters to task demands. We found that the brain does this instantaneously and that this can even happen during movement. Therefore, this suggests that there exists an overlap during movement planning and execution. [ABSTRACT FROM AUTHOR]

This study explores the role of task constraints over muscle synergies expression in the context of upper limb motor impairment after stroke. We recruited nine chronic stroke survivors with upper limb impairments and fifteen healthy controls, who performed a series of tasks designed to evoke muscle synergies through various spatial explorations. These tasks included an isometric force task, a dynamic reaching task, the clinical Fugl-Meyer (FM) assessment, and a pinch task. Electromyographic data from 16 upper limb muscles were collected during each task, alongside intermuscular coherence (IMC) measurements during the pinch task to assess neuromuscular connectivity. The findings confirm that motor impairment is inversely related to the diversity of muscle synergies, with fewer synergies and more stereotypical synergy structures observed post-stroke. The study further reveals that the nature of motor tasks significantly affects the number of identifiable muscle synergies, with less constrained tasks revealing a broader array of synergies. These findings highlight the importance of carefully selecting motor tasks in the context of clinical research and assessments to understand a patient’s motor impairment, thus aiding in developing tailored rehabilitation strategies. [ABSTRACT FROM AUTHOR]

Current clinical assessment tools don’t fully capture the genuine neural deficits experienced by chronic stroke survivors and, consequently, they don’t fully explain motor function throughout everyday life. Towards addressing this problem, here we aimed to characterise post-stroke alterations in upper-limb control from a novel perspective to the muscle synergy by applying, for the first time, a computational approach that quantifies diverse types of functional muscle interactions (i.e. functionally-similar (redundant), -complementary (synergistic) and -independent (unique)). From single-trials of a simple forward pointing movement, we extracted networks of functionally diverse muscle interactions from chronic stroke survivors and unimpaired controls, identifying shared and group-specific modules across each interaction type (i.e. redundant, synergistic and unique). Reconciling previous studies, we found evidence for both the concurrent preservation of healthy functional modules post-stroke and muscle network structure alterations underpinned by systemic muscle interaction re-weighting and functional reorganisation across all interaction types. Cluster analysis of stroke survivors revealed two distinct patient subgroups from each interaction type that all distinguished less impaired individuals who were able to adopt novel motor patterns different to unimpaired controls from more severely impaired individuals who did not. Our work here provides a nuanced account of post-stroke functional impairment and, in doing so, paves new avenues towards progressing the clinical use case of muscle synergy analysis. [ABSTRACT FROM AUTHOR]

Recent studies highlight a persistent increase in subsequent injury risk following a sport-related concussion (SRC) despite clinical recovery. However, markers of persistent alterations in sensorimotor integration have yet to be identified. One possibility is that compensatory adaptation following SRC may only be unmasked during transient periods of high task complexity in specific sensorimotor circuits. The current study used short-latency afferent inhibition (SAI) to investigate the long-term sequelae of sport-related concussion (SRC) in different short-latency sensorimotor circuits converging in the motor cortex. Specific sensorimotor circuits sensitive to posterior-anterior current with a positive phase lasting 120µs (PA120) and anterior-posterior current with a positive phase lasting 30µs (AP30) were assessed using controllable pulse parameter transcranial magnetic stimulation (cTMS) while young adults with and without a history of SRC were at rest or responded to valid and invalid sensorimotor cues. SAI was quantified as the ratio of the motor-evoked potential (MEP) elicited by peripherally conditioned cTMS stimuli to the unconditioned MEP for each cTMS configuration. Individuals with a SRC history demonstrated persistent adaptation in AP30 SAI, but only in response to invalid cues. Persistent adaptation in AP30 SAI was not apparent at rest or during simple sensorimotor transformations in response to valid cues. PA120 SAI demonstrated similar responses at rest and in response to both valid and invalid cues, regardless of SRC history. AP30-sensitive sensorimotor circuits may mark the long-term SRC sequelae and the increased susceptibility to momentary breakdowns in sensorimotor integration during periods of high cognitive-motor demands. [ABSTRACT FROM AUTHOR]

Recent research suggests that variability enhances motor control, learning, and adaptation by improving the system's response to environmental demands. It also develops the cognitive and executive functions of athletes. The purpose of the study is to evaluate the variability of the split leap in rhythmic gymnastics, performed with and without ribbon handling, analysing in which of the two techniques there is greater variability. The sample consists of six competitive gymnasts with an average age of 15.1 years (±0.94). The acquisitions were carried out with the BTS Bioengineering integrated multifactorial optoelectronic system, using fifteen passive markers, six BTS Smart-DX cameras, two cameras for video support and seven BTS-6000 force platforms. The results show that the coefficient of variation (CV%) in trials performed with ribbon is higher than those without the apparatus. Cohen's Effect Size revealed a small effect size between trials with ribbon and those without. Despite being minimal, this difference emphasizes the presence of variability in jumps executed with ribbon in comparison to free body trials. In conclusion, this study explored both intrinsic (CV%) and extrinsic (task complexity, technical experience) factors of jump performance, highlighting the utility of gold standard motion analysis systems for researching executive variability in rhythmic gymnastics jumps. [ABSTRACT FROM AUTHOR]

Parameter identification in dynamical systems is a well-known problem with many applications in control design, system monitoring, and fault detection. As these systems are increasingly integrated into complex and demanding environments, challenges such as rapid response, uncertainty handling, and disturbance rejection must be addressed. This paper presents a real-time estimation technique for parameters and load torque in brushless DC (BLDC) motors. These electrical machines are extensively used in engineering applications and often operate under hard conditions. The proposed method is based on algebraic identification, known for its robust performance in both linear and nonlinear systems. In utilizing the mathematical model of a BLDC motor, a set of equations is derived to enable parameter estimation, assuming the availability of input and output measurements in open loop. Moreover, unknown load torque is estimated by approximating the disturbance over a short time window using Taylor series expansion polynomials. The theoretical contribution is analytically validated and is also verified through numerical evaluations revealing the effectiveness of the proposed technique for real-time parameter and disturbance estimation in BLDC motors over other important techniques. Additionally, to address potential peaks in the estimation process, a modification involving an exponent is introduced to mitigate these issues. [ABSTRACT FROM AUTHOR]

Haptic simulation systems enable users to manipulate virtual environments through their interaction with haptic devices. Stable high fidelity interaction with virtual environments for many applications requires actuators with both high torque density and low parasitic forces. Brushless direct-current (BLDC) motors offer both high torque density and low friction, making them a prime candidate for this application. This paper evaluates the use of a BLDC motor for use as a direct drive haptic actuator, in comparison with the brushed direct-current (DC) motor and capstan mechanism commonly used in indirect drive actuation of haptic devices. The comparison metrics include data sheet parameters, peak torque determined using a thermal simulation, current and position step responses, uncoupled stability regions, and dynamic rendering areas. It is concluded that a direct drive BLDC motor can supply higher peak torque, while projecting lower inertia and friction and thus offering higher acceleration. These results indicate that BLDC motors are a promising technology for effective direct drive haptic actuation.

Sensory ataxia and cerebellar ataxia share common manifestations including dysmetria, intentional tremor and lack of smoothness. We formulated a theoretical framework to describe the patients’ sensory and cerebellar ataxic behavior as consequences of a forward model impairment. To test this framework, the present study aimed to compare upper limb movement kinematics in an index-to-nose task between three groups: healthy controls, people with CNS focal lesions and cerebellar deficits and people with CNS focal lesions and somatosensory impairment. We recruited 12 healthy controls (age $= 29.0\pm 2.9$ years, female = 5) and 20 participants with focal CNS lesions. We divided the sample according to the lesion site in participants with lesions in areas involved in the somatosensory information processing (n = 12, age $= 62.4\pm 13.6$ years, female = 5) and participants with lesions in the cerebellum or cerebellar peduncle (n = 8, age $= 64.3\pm 13.9$ years, female = 1). Movement features concerning movement efficiency (average velocity, peak velocity), accuracy (spatial error when pointing to the nose) and motor planning (timing and spatial occurrence of velocity peak, velocity and deviation from ideal trajectory at 150ms after the movement onset) were computed. Both the groups of participants with CNS lesions performed the movement slower than healthy controls. When comparing results from the two groups of patients, we showed that participants with cerebellar lesions were characterized by greater trial-to-trial variability of the velocity peak (repeated measure ANOVA group effect: F = 5.242, p = 0.012) and its timing (condition*group interaction: F = 5.38, p = 0.011). Our findings suggested that both participants with cerebellar and somatosensory deficits showed signs of anticipatory motor control impairment.

IntroductionParkinson’s Disease is the second most common neurodegenerative disease in the world. It affects mainly people over 65 and the incidence increases with age. It is characterized by motor and non-motor symptoms and several clinical manifestations. The most evident symptom that affects all patients with Parkinson’s Disease is the impairment of motor control, including bradykinesia, tremor, joint rigidity, and postural instability. In the literature, it has been evaluated with muscle synergies, a well-known method for evaluating motor control at the muscular level. However, few studies are available and there is still a major gap to fill to exploit the potential of the method for assessing motor control in Parkinson’s Disease, both in the understanding of physiopathology and clinical practice.MethodsIn the light of understanding and fostering future developments for the field, in this review we initially screened 212 papers on Scopus and Web of Science and selected 15 of them to summarize the main features of investigations that employed muscle synergies to analyze patients with Parkinson’s Disease. We detailed the features of the screened papers by reporting the clinical findings, a detailed report of EMG processing choices and synergy-based results.ResultsWe found that synergistic control is in general altered in patients with Parkinson’s Disease, but it can improve if patients are subjected to pharmacological and rehabilitation therapies. Moreover, a further understanding of synergistic control in Parkinson’s patients is needed.DiscussionWe discuss the future developments in the field with a detailed assessment of the topic on the view of physicians, including the most promising lines of research for clinical practice and from the perspective of engineers, for methodological application of synergistic approaches.

This study aimed to first investigate changes in electromyography (EMG) patterns after multilevel surgical treatment in patients with cerebral palsy (CP) and then to assess the connection between the measure of EMG and motor control indices and surgery outcomes. We analyzed retrospective EMG and gait data from 167 patients with CP before and after surgery and from 117 typically developed individuals as a reference group. The patients underwent at least one soft tissue surgery on their shank and foot muscles. Using Repeated Measures ANOVA, we examined the norm-distance (ND) of the kinematics, kinetics, and EMG patterns, in addition to the Kerpape-Rennes EMG-based Gait Index (EDI), EMG Profile Score (EPS), and Walking Dynamic Motor Control Index (DMC) before and after surgery. Participants were divided into different response groups (poor, mild, and good gait quality) according to their pre- and post-treatment Gait Deviation Index (GDI), using the K-means-PSO clustering algorithm. The gait and EMG indices were compared between the responders using the nonparametric Mann–Whitney test. The ND for all kinematics and kinetics parameters significantly improved (p-value < 0.05) after the surgery. Regarding EMG, a significant reduction was only observed in the ND of the rectus femoris (p-value < 0.001) and soleus (p-value = 0.006). Among the indices, DMC was not altered post-operatively (p-value = 0.88). Although EDI and EPS were consistent across responders with a similar pre-treatment gait, a higher DMC was significantly associated with a greater improvement, particularly in patients with poor gait (p-value < 0.05). These findings indicate systematic changes in the EMG of patients with CP following surgery, which can also be demonstrated through indices. DMC is a measure that can potentially serve as a partial predictor of outcomes, particularly in patients with poor pre-operative gait. Future research should investigate the effects of different surgical strategies on the improvement of these patients.

The evolution of indoor skydiving from military origins to a globally recreational pursuit has attracted individuals without prior specific training, exposing them to the heightened risk of muscle–joint injuries associated with indoor skydiving. This study aims to assess the muscular excitation patterns in highly skilled instructors to determine the optimal activation strategies for preventing musculoskeletal injuries. Nine expert indoor skydiving instructors (M/F: 8/1; age 31 ± 7 years; body mass: 70.5 ± 11.1 kg; stature: 1.74 ± 0.09 m) were enrolled. The surface electromyographic signal was recorded on the anterior deltoid, AD; posterior deltoid, PD; pectoralis major, PM; latissimus dorsi, LD; rectus abdominis, Rabd; erector spinae, ES; rectus femoris, RF; and biceps femoris, BF for each position: PRONE, SUPINE, SIT, and head-down (HD). A synchronous heart rate was recorded to assess the cardiac engagement. The neuromuscular load (NeLo), representative of the excitation amplitude of a muscle set, was determined for each position across different body regions. PRONE and SUPINE were the least demanding in terms of cardiac engagement (67 ± 6 and 85 ± 8 bpm, respectively) and exhibited the lowest neuromuscular excitation (24 ± 10 and 24 ± 8% Max, respectively). By contrast, HD exhibited the highest cardiac (127 + 18 bpm) and neuromuscular (71 + 11% Max) engagement and particularly in the lower-trunk and lower-limbs muscles. SIT predominantly engaged upper-trunk and shoulder muscles. The findings indicate the significant engagement of the musculature surrounding the shoulder joint and that responsible for lower-trunk stabilization in maintaining the investigated positions. A targeted training regimen on strengthening these muscles is advised before practicing indoor skydiving to prevent shoulder joint injuries or lower back muscle overloads.

This study aimed to examine the influence of real-time feedback on intentional abdominal muscle engagement in adults with chronic low back pain (CLBP) during daily activities. The research further sought to evaluate the outcomes of this training on neuromuscular control, pain perception, and functional capacity.We compared a group of adults who received real-time feedback on changes in waist circumference with a group trained in abdominal contraction without real-time feedback.Surface electromyographic (sEMG) signals were measured in the rectus abdominis (RA), external oblique (EO), internal oblique (IO), and erector spinae (ES) muscles. Pain intensity was assessed using the visual analog scale (VAS), and functional outcomes were assessed using the Oswestry Disability Index (ODI).After the intervention, sEMG signals of the RA, EO, and IO muscles were significantly higher in the experimental group. There were no significant differences in ES muscle activity between the groups. Both the experimental and control groups showed significant decreases in VAS and ODI scores after the intervention.Intentional abdominal contraction aided by real-time feedback can improve functionality in patients with chronic low back pain. [ABSTRACT FROM AUTHOR]

Humans possess a unique ability to manipulate tools to help us navigate the world around us. This ability is facilitated by the dexterity of our hands. However, millions lose this capability annually due to conditions like limb amputation or cerebral vascular accident (i.e., stroke). This great loss of human hand function has led to increased study of human hand action. Although previous research focused on coordinated hand motion, known as synergies, during reaching and grasping, manipulation of complex objects remains understudied. Specifically, we aimed to test two hypotheses: 1 ) the number of synergies underlying manipulation is the same as those underlying reach-and-grasp, and 2 ) the identity of synergies underlying manipulation is different from those underlying reach-and-grasp. To do so, we measured human hand motion during two experiments: 1 ) during reach and grasp of a tool or object commonly used in wire harness installation and 2 ) during manipulation of those objects and tools to install a wire harness on a mock electrical cabinet. Results showed that manipulation generally required more synergies than grasp. Comparison between reach-and-grasp and manipulation revealed a decrease in synergy similarity with synergy-order. Considering that higher-order synergies become significant during manipulation, it is important that we investigate these differences; this study serves as a point of entry to doing so. If we want our prosthetic and rehabilitative devices to restore hand function to those who have lost it, we must study hand function, specifically manipulation, and not just grasping. NEW & NOTEWORTHY This study uncovers new insights into kinematic synergies during functional human hand manipulation of objects and tools, through the study of wire harness installation. It emphasizes the nuanced distinctions between functional hand manipulation and simple grasping, revealing that manipulation tasks require a greater number and distinct subset of hand synergies compared with simple grasp actions. This research marks a significant step toward appreciating the intricacies of hand coordination in complex tasks beyond grasping.

Purpose : Asymptomatic patellar tendon abnormality (APTA) is considered a precursor to patellar tendinopathy (PT), but its pathogenesis remains unclear, especially regarding changes in muscle coordination. Therefore, it is essential to explore the muscle synergy patterns in individuals with APTA. Methods: This study recorded sEMG data during stop-jump tasks in 8 APTA and 8 healthy amateur male basketball players in a simulated basketball game. Muscle synergies were extracted using Non-Negative Matrix Factorization and K -Means clustering. Results : Three synergies were identified in both groups. In Synergy 1, tibialis anterior, semitendinosus and vastus lateralis weights primarily influenced the waveform. In Synergy 2, biceps femoris, vastus lateralis and medial gastrocnemius weights primarily influenced the waveform. In Synergy 3, peroneus longus, vastus medialis and vastus lateralis weights primarily influenced the waveform. Key findings include higher vastus medialis weight in the APTA group during P1 and P2, and higher semitendinosus weight in P3 and P4. Additionally, the gastrocnemius and biceps femoris showed significant differences between groups across phases. Conclusions: The APTA group exhibited different muscle synergy patterns under specific phases and load accumulation conditions, particularly in the vastus medialis, medial gastrocnemius, biceps femoris and peroneus longus. The APTA group demonstrated distinct synergy patterns, suggesting a compensatory mechanism to reduce patellar tendon load, potentially increasing knee injury risk. This finding provides new guidance for clinical assessment and intervention strategies for the training and rehabilitation of APTA individuals., (© 2024 Dongxu Wang et al., published by Sciendo.)

When engaged in dynamic or continuous movements, action initiation involves modifying an ongoing motor program rather than initiating it from rest. Event-related theta synchronization over sensorimotor areas is a neurophysiological marker for modifying motor programs. We used electroencephalography (EEG) to examine how task complexity and age affect event-related synchronization (ERS) in the theta band during a dynamic bimanual, visuomotor pinch force task. Older (mean age = 68) and younger (mean age = 26) participants performed symmetric (SYM) and asymmetric (ASYM) bimanual pinch force adjustments. Trials began with a visually cued contraction from a baseline force to a novel target force (P1). Force had to be maintained at the target until a visually cued return to the familiar baseline (P2). Older adults reacted slower across task conditions, and their accuracy decreased more when shifting from the SYM to the ASYM condition. Older adults also displayed lower theta ERS across conditions. Additionally, older adults were not able to modulate theta expression based on whether a force change was initiated to a novel target or back to baseline. Younger adults showed significantly stronger theta ERS after P1-cues compared to P2-cues, while the theta response to P1 and P2 cues was not different in older adults. Older adults also showed stronger lateralization, displaying higher theta ERS over the dominant motor cortex. Finally, event-related theta synchronization appeared to be behaviorally relevant across groups and correlated with task performance. Together, the results show that theta ERS over sensorimotor areas is a strong, age-sensitive marker of dynamic pinch force adjustments showing an age-related reduction in specificity with reduced context-dependent modulations and more imbalanced bimanual activation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The author is an Editorial Board Member/Editor-in-Chief/Associate Editor/Guest Editor for NeuroImage and was not involved in the editorial review or the decision to publish this article., (Copyright © 2025. Published by Elsevier Inc.)

In trampolining, optimizing body orientation during landing reduces injury risk and enhances performance. As trampolinists are subject to motor variability, anticipatory inflight corrections are necessary to regulate their body orientation before landing. We investigated the evolution of a) body orientation and b) limb position (i.e., arms and legs) variabilities. Secondary objectives were to investigate c) the link between acrobatics difficulty and the variability accumulation, and d) to identify links between body orientation variability and gaze orientation. Kinematics and gaze orientation were captured using inertial measurement units and an eye tracker, respectively. Seventeen trampolinists performed up to 13 different acrobatics (different number of rotations in twist and somersault). Intra-trampolinist pelvis orientation and limb position inter-trial variability was computed for each acrobatic at three key timestamps: takeoff, 75 % completion of the twist, and landing. Pelvis orientation variability significantly increased between takeoff and the instant when 75 % of the twist is completed (+75 %) and then decreased from the instant when 75 % of the twist is completed until landing (-39 %). Conversely, limb variability decreased (upper limbs: -66 % and lower limbs: -46 %), before increasing (+357 % and +127 %), suggesting that trampolinists adapted their limb kinematics to regulate pelvis orientation before landing. It was qualitatively observed that this decrease in body orientation variability occurred mostly when trampolinists were looking at the trampoline bed before landing. In addition, there was a moderate correlation between the number of twists in a straight somersault and the variability accumulation at 75 % of the twist, highlighting that trampolinists accumulate more variability as the number of twist rotations increases., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Many individuals with incomplete spinal cord injury (SCI) exhibit reduced volitional control of trunk muscles, such as impaired voluntary contractions of the erector spinae (ES), due to damage to the neural pathways regulating sensorimotor function. Studies using conventional bipolar electromyography (EMG) showed alterations in the overall, or global, activation of the trunk muscles in people with SCI. However, how activation varied across specific regions within the ES, referred to as regional activation, remains unknown. The aim of the study was to investigate the regional distribution of the ES activity below the level of injury in individuals with incomplete SCI during postural tasks and multidirectional reaching tasks using high-density EMG. Twenty-one individuals with incomplete SCI and age-matched controls were recruited. The EMG amplitude of the thoracic ES and displacement of the arm, trunk, and center of pressure were recorded during the tasks. Activation was more in the lower region of the ES in individuals with SCI compared with the controls during the postural tasks. Additionally, activation was limited to a small area of the ES during the reaching tasks. The EMG amplitude was greater during reaching forward than returning to the upright posture in the controls; however, this phase-dependent difference in the EMG amplitude was not present in individuals with SCI. Our findings demonstrate changes in regional activation of the thoracic ES during postural and reaching tasks, likely reflecting injury-induced changes in selective neural control to activate residual muscle fibers of the ES for postural control and function after SCI.

The interplay between two major forebrain structures-cortex and subcortical striatum-is critical for flexible, goal-directed action. Traditionally, it has been proposed that striatum is critical for selecting what type of action is initiated, while the primary motor cortex is involved in specifying the continuous parameters of an upcoming/ongoing movement. Recent data indicate that striatum may also be involved in specification. These alternatives have been difficult to reconcile because comparing very distinct actions, as is often done, makes essentially indistinguishable predictions. Here, we develop quantitative models to reveal a somewhat paradoxical insight: only comparing neural activity across similar actions makes strongly distinguishing predictions. We thus developed a novel reach-to-pull task in which mice reliably selected between two similar but distinct reach targets and pull forces. Simultaneous cortical and subcortical recordings were uniquely consistent with a model in which cortex and striatum jointly specify continuous parameters governing movement execution., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Inaccurate perception of one's physical abilities is potentially related to age-related declines in motor planning and can lead to changes in walking. Motor imagery training is effective at improving balance and walking in older adults, but most research has been conducted on older adults following surgery or in those with a history of falls. Deficits in motor imagery ability are associated with reduced executive function in older adults with cognitive impairment., Objectives: To determine whether walking-specific motor imagery training could improve walking performance (physical and imagined) in healthy older adults, and identify the relationship between actual and imagined movement, motor imagery accuracy and executive function across 5 different walking tasks in healthy older adults., Methods: A cohort of 53 community dwelling older adults took part in a 4-wk randomized controlled trial to assess the effect of motor imagery training on the physical and imagined performance of 5 walking-related tasks (3 narrow path walking tasks, Timed-up and go and step-over test), together with motor imagery clarity using the kinesthetic and visual imagery questionnaire (KVIQ-10). The association between physical performance, motor imagery accuracy and executive function were identified at baseline., Results: Four weeks of motor imagery training did not improve walking-specific performance (imagined or physical) compared to no-training. Motor imagery training did improve the visual clarity of imagined non-walking tasks. Executive function was significantly correlated with 2 out of 5 imagined walking tasks and 4 out of 5 physical walking tasks but was not associated with motor imagery accuracy., Conclusion: Four weeks of motor imagery training is not effective at improving performance in walking-related tasks in healthy older adults. This lack of improvement may be due in part to the high functional ability of the cohort. Future research should assess the relationship between motor planning and executive function with more complex walking tasks., Trial Registration: ANZCTR registration (ACTRN12619001784101)., Competing Interests: Declaration of competing interest None., (Copyright © 2024 The Author(s). Published by Elsevier Masson SAS.. All rights reserved.)

Numerous studies have reported benefits of music listening to support learning and motor rehabilitation. In the case of handwriting, previous studies suggested that musical background improves movement speed and fluency. Whether this benefit comes from the melody or is specifically related to the rhythmic cues provided by the music remains to be established. In addition, music can influence handwriting differently depending on the child's level of expertise. To disentangle these effects, we recorded graphic movement under different sound backgrounds in children of two different grades. In total, 44 s graders and 44 fifth graders needed to copy loops and isolated words under four sound conditions: silent, melodic without metronome, melodic with slow metronome (1.6 Hz), and melodic with faster metronome (2.2 Hz). The results revealed that listening to a pure melodic background reduced writing velocity, movement fluency, and loop size in both groups. In addition, the rhythmic cues influenced handwriting kinematics differently depending on grade and task. For the younger group, the two rhythms, and especially the slow rate, increased the loop copying velocity, whereas for the words the velocity and movement fluency were reduced by the fast rate. Conversely, for the older group, the two rhythmic conditions reduced writing velocity and movement fluency, and they increased the size of both the loops and the words. Finally, the effects also depend on handwriting level; poor writers seem to benefit more from the adding of rhythmic cues. These results raise interesting perspectives for learning to write and for the rehabilitation of handwriting difficulties., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Context: After completing rehabilitation, patients face a high risk of subsequent injury following anterior cruciate ligament reconstruction. It is important to identify potential barriers to patient success including clinician knowledge. The purpose of this study was to assess clinician knowledge of research related to anterior cruciate ligament reconstruction rehabilitation., Design: This was a survey study using snowball sampling., Methods: Survey development began with the creation of a construct map and contained varying levels of advanced concepts, level I indicating the most basic and level V the most complex. The survey was distributed to advertise to target population. A total of 60 participants (24 athletic trainers, 33 physical therapists, and 3 dual credentialed) completed the study., Results: Overall, participants displayed moderate to high levels of knowledge (79.7%-93.5% correct), apart from the implementation of motor learning principles., Conclusions: Clinician knowledge may not be the primary barrier to patient success, but the implementation of this knowledge should be explored in relation to patient outcomes. Future research should examine a larger cohort to examine differences between clinician types.

Background: While it is evident that stroke impairs motor control, it remains unclear whether stroke impacts motor adaptation-the ability to flexibly modify movements in response to changes in the body and the environment. The mixed results in the literature may be due to differences in participants' brain lesions, sensorimotor tasks, or a combination of both., Objective: We first sought to better understand the overall impact of stroke on motor adaptation and then to delineate the impact of lesion hemisphere and sensorimotor task on adaptation poststroke., Methods: Following the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines, we conducted a systematic review and meta-analysis of 18 studies comparing individuals poststroke to neurotypical controls, with each group consisting of over 200 participants., Results: We found that stroke impairs motor adaptation ( d  = -0.63; 95% confidence interval [-1.02, -0.24]), and that the extent of this impairment did not differ across sensorimotor tasks but may vary with the lesioned hemisphere. Specifically, we observed greater evidence for impaired adaptation in individuals with left hemisphere lesions compared to those with right hemisphere lesions., Conclusions: This review not only clarifies the detrimental effect of stroke on motor adaptation but also underscores the need for finer-grained studies to determine precisely how various sensorimotor learning mechanisms are impacted. The current findings may guide future mechanistic and applied research at the intersection of motor learning and neurorehabilitation., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Objective: To compare center of mass (COM) and center of pressure (COP) displacement, joint angles, and muscle activity for the ankle, knee, and hip during the posteromedial (PM) reach direction of the Star Excursion Balance Test between individuals with chronic ankle instability (CAI) and healthy individuals., Design: Cross-sectional Study., Setting: Biomechanics laboratory., Participants: Fifteen individuals with CAI (age: 20.0 ± 1.2 y) and 20 healthy individuals (age: 20.6 ± 0.8 y)., Main Outcome Measures: The maximum reach distance (MRD). The COM and COP displacement, and ankle, knee, and hip joint angles of the stance limb during the PM reach task measured via a 3D motion analysis system. Electromyography (EMG) was also recorded during the task from the tibialis anterior (TA), soleus, peroneus longus, vastus medialis (VM), biceps femoris, and gluteus medius muscles., Results: MRD of the CAI group was shorter than the healthy group (P = 0.005). The CAI group showed higher COM positioning (P = 0.007), less knee flexion (P = 0.009), and lower muscle activity in TA (P = 0.04), and VM (P = 0.007) during performance of the PM reach as compared to the healthy group., Conclusions: These findings suggest that individuals with CAI demonstrate altered postural control strategies during PM reach performance, likely contributing to a shorter MRD., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Previous research on resting muscles has shown that inter-pulse interval (IPI) duration influences transcranial magnetic stimulation (TMS) responses, which can introduce serious confounding variables into investigations if not accounted for. However, it is far less clear how IPI influences TMS responses in active muscles. Thus, the purpose of this study was to examine the relationship between IPI and corticospinal excitability during submaximal isometric elbow flexion. Corticospinal excitability to the biceps and triceps brachii was measured using motor evoked potentials (MEPs) elicited via TMS. Stimulation intensity was set to 120% of the biceps brachii's active motor threshold while participants produced 10% of their biceps' maximal muscle activity. TMS was delivered as separate trains of five stimulations, with experimental conditions differing between IPIs of 4, 6, 8, 10, 12 or 14 s. Results demonstrated that IPI had no influence on MEP amplitudes for either the biceps or triceps. However, when MEP amplitudes were expressed as a unitless ratio to pre-stimulus muscle activity, a main effect of time was found for the biceps; MEP amplitudes progressively decreased with successive stimulations (MEP 1:32.8 ± 5.9; MEP 5:27.7 ± 4.3, p < 0.05). These results suggest that IPI is unlikely to represent a confounding variable in TMS studies utilizing active contractions. However, studies looking to compare the amplitudes of single MEPs over time should be aware of the possibility that amplitudes may decrease with continuous stimulation. Future research should seek to examine even longer IPIs and explore the influence of higher stimulation intensities., (© 2025 The Author(s). European Journal of Neuroscience published by Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)