Motor Variables Research Articles

Relationship between initial motor variability and learning and adaptive ability. A systematic review.

Motor variability is an intrinsic feature of human beings that has been associated with the ability for learning and adaptation to specific tasks. The purpose of this review is to examine whether there is a possible direct relationship between individuals' initial variability, in both amount and structure variability, in their ability for learning and adaptation in motor tasks. Eighteen articles examined the relationship between initial motor variability and the ability for learning and adaptation. Twelve found a direct relationship. In reward learning task greater amount variability was associated with greater improvement learning, however, this association was not observed with structure variability. While in error learning task associations were reported with both greater amount variability and more complexity structure. Nevertheless, bias in initial performance related to the amount of variability was found, so the structure of initial variability seems to be a better indicator of improvement in this type of task. Further research is needed for further research to better understand the potential relationship between initial motor variability and the ability for learning and adaptation in motor tasks.

Balance Ability Characteristics and Related Factors in Athletes Across Different Sports: A Preliminary Study

Background: We conducted a cross-sectional study to examine two-leg- and one-leg-type balance characteristics in athletes and explore factors related to their balance ability. Methods: A total of 213 participants, including athletes from various sports (gymnastics, boat racing, swimming, soccer, judo, and baseball) and non-athletes, were included (142 men, 71 women, average age 21.5 ± 2.1 years). Balance ability was classified into two-leg and one-leg types using the modified index of postural stability (mIPS) in a two-leg stance and the one-legged stance duration with eyes closed (OLS). Body composition, upper and lower limb strength, and lower limb sensation were also measured. To examine the balance characteristics of each sport, the mIPS and OLS were used as dependent variables in a multiple regression model with age, height, weight, and sex as independent variables. Results: The results showed a significantly higher mIPS in gymnastics (estimate: 0.22) and boat racing (0.14), and it was lower in swimming (−0.25). The OLS was significantly higher in soccer (16.98), judo (16.23), gymnastics (9.77), and baseball (9.12) and significantly lower in swimming (7.93). Additionally, the mIPS was independently associated with knee extension strength (0.12), sensory motor variables (−0.004), and height (−0.01). The OLS was associated with skeletal muscle mass (1.85) and height (−1.42). Conclusions: In summary, gymnasts showed superior two-leg and one-leg balance; boat racers excelled in two-leg balance; swimmers showed inferior two-leg but better one-leg balance; and soccer, judo, and baseball athletes demonstrated superior one-leg balance. Additionally, the mIPS was associated with knee extensor strength, plantar pressure sensation, and height, whereas the OLS was associated with skeletal muscle mass and height.

Rehabilitative subacute inpatient care-Optimizing posthospital care for geriatric patients with rehabilitation needs: results of the REKUP study

Geriatric patients in subacute inpatient care (SC) with rehabilitation needs after hospitalization seldom utilize rehabilitative services and are often transitioned to long-term care (LTC), suggesting that their care in SC can be optimized. To evaluate the effectiveness of rehabilitative subacute inpatient care (REKUP) in improving the care of geriatric patients in SC with rehabilitation needs after hospitalization. The study was conducted as anonrandomized intervention trial with an historical control group (CG). The intervention group (IG: n = 49) received REKUP (activating therapeutic care, functional rehabilitative therapy, psychosocial services, medical care), while the CG (n = 57) received usual care during SC. Primary outcomes were transition to inpatient rehabilitation, home, and LTC, deteriorated care setting, care level, and mortality within 3months after SC. Secondary outcomes were functional, motor and psychological variables. The transition rate to inpatient rehabilitation (82% vs.37%) and home (86% vs.65%) was higher (p < 0.05) in the IG than in the CG. The proportion of persons utilizing LTC (12% vs.35%) and with deteriorated care setting (35% vs.60%) was lower (p < 0.01) in the IG than in the CG. The Barthel Index, visual analogue scale of the EQ-5D, and numerical pain scale improved (p < 0.05) during the SC stay in the IG but not in the CG. REKUP as anew care model for SC promotes the transition to inpatient rehabilitation, reduces the utilization of LTC and improves the chances of returning home and achieving greater independence in geriatric patients with rehabilitation needs after hospitalization.

Motor variability during resistance training: Acceleration signal as intensity indicator

Analysis of variability in physiological time series has been shown to be an indicator of the state of the organism. Although there is evidence of the usefulness of analysis of the amount and/or structure of variability (complexity) in cycling actions, there is limited knowledge about its application in resistance exercise. The aim of this study is to find out whether variability in acceleration signals can be an indicator of intensity level in a squat task. For this purpose, an experimental design was developed in which the following participated seventy-two participants (age = 25.7 ± 4.4 years; height = 169.2 ± 9.8 cm; body mass = 67.7 ± 11.2 kg; ratio 1RM/body mass = 1.4 ± 0.3). They performed four repetitions of back squat at loads of 10%, 30%, 50%, 70%, and 90% of 1RM. Acceleration during the exercise was recorded using an inertial measurement unit (IMU) and a force platform. The variability of the movement was then analyzed using Standard Deviation (SD), Detrended Fluctuation Analysis (DFA), Fuzzy Entropy (FuzzyEn), and Sample Entropy (SampEn). For the IMU and for the force platform, significant effects were observed in all variables (p &lt; 0.001). In pairwise comparisons, IMU showed a significant increase in motor complexity with increasing intensity, among most intensities, in DFA, FuzzyEn and SampEn. Differences in force platform were more limited, and only DFA detected differences between most intensities. The results suggest that measures of signal and acceleration variability may be a useful indicator of the relative intensity at which a squat exercise is performed.

Prior coordination solutions shape motor learning and transfer in redundant tasks

Motor learning does not occur on a ‘blank slate’, but in the context of prior coordination solutions. The role of prior coordination solutions is likely critical in redundant tasks where there are multiple solutions to achieve the task goal – yet their influence on subsequent learning is currently not well understood. Here we addressed this issue by having human participants learn a redundant virtual shuffleboard task, where they held a bimanual manipulandum and made a discrete throwing motion to slide a virtual puck towards a target. The task was redundant because the distance traveled by the puck was determined by the sum of the left- and right-hand speeds at the time of release. On the first day, 37 participants in different groups practiced symmetric or asymmetric solutions. On the second day, all participants transferred to a common criterion task, which required an asymmetric solution. Results showed that: (i) the symmetry of the practiced solution affected motor variability during practice, with more asymmetric solutions showing higher exploration of the null space, (ii) when transferring to the common criterion task, participants in the symmetric group showed much higher null space exploration, and (iii) when no constraints were placed on the solution, participants tended to return to the symmetric solution regardless of the solution originally practiced. Overall, these results suggest that the stability of prior coordination solutions plays an important role in shaping learning in redundant motor tasks.

Online stimulation of the prefrontal cortex during practice increases motor variability and modulates later cognitive transfer: a randomized, double-blinded and sham-controlled tDCS study

The benefits of learning a motor skill extend to improved task-specific cognitive abilities. The mechanistic underpinnings of this motor-cognition relationship potentially rely on overlapping neural resources involved in both processes, an assumption lacking causal evidence. We hypothesize that interfering with prefrontal networks would inhibit concurrent motor skill performance, long-term learning and associated cognitive functions dependent on similar networks (transfer). We conducted a randomised, double-blinded, sham-controlled brain stimulation study using transcranial direct current stimulation (tDCS) in young adults spanning over three weeks to assess the role of the prefrontal regions in learning a complex balance task and long-term cognitive performance. Balance training combined with active tDCS led to higher performance variability in the trained task as compared to the sham group, impacting the process of learning a complex task without affecting the learning rate. Furthermore, active tDCS also positively influenced performance in untrained motor and cognitive tasks. The findings of this study help ascertaining the networks directly involved in learning a complex motor task and its implications on cognitive function. Hence, opening up the possibility of harnessing the observed frontal networks involved in resource mobilization in instances of aging, brain lesion/injury or dysfunction.

Effect of Phasic Experimental Pain Applied during Motor Preparation or Execution on Motor Performance and Adaptation in a Reaching Task: A Randomized Trial.

Musculoskeletal conditions often involve pain related to specific movements. However, most studies on the impact of experimental pain on motor performance and learning have used tonic pain models. This study aimed to evaluate the effect of experimental phasic pain during the preparation or execution of a reaching task on the acquisition and retention of sensorimotor adaptation. Participants were divided into three groups: no pain, pain during motor preparation, and pain during motor execution. Pain was induced over the scapula with a laser while participants performed a force field adaptation task over two days. To assess the effect of pain on motor performance, two baseline conditions (with or without pain) involving unperturbed pointing movements were also conducted. The results indicated that the timing of the nociceptive stimulus differently affected baseline movement performance. Pain during motor preparation shortened reaction time, while pain during movement execution decreased task performance. However, when these baseline effects were accounted for, no impact of pain on motor adaptation or retention was observed. All groups showed significant improvements in all motor variables for both adaptation and retention. In conclusion, while acute phasic pain during motor preparation or execution can affect the movement itself, it does not interfere with motor acquisition or retention during a motor adaptation task.

From Novice to Expert: How Expertise Shapes Motor Variability in Sports Biomechanics-a Scoping Review.

With expertise, athletes develop motor strategies that enhance sports performance or reduce functional costs. Motor variability is known as a relevant way to characterize these strategies in athletes with different levels of expertise. The aim of this scoping review is to gather and discuss the latest advances in the impact of expertise on motor variability during sports-related tasks. A search encompassing three databases, Medline, SportDiscus, and Academic Search Complete, was performed. Our research methodology included three core themes: motor variability, laboratory instruments, and sports. Motor variability metrics (e.g., standard deviation and approximate entropy) and laboratory instruments (e.g., motion capture system, EMG, and force plate) were compiled. Athletes' expertise was defined by the time of deliberate practice, the performance results, or the level in which they performed. Overall, 48 of the 59 included studies determined that higher-skilled athletes had lesser motor variability than lower-skilled athletes. This difference in motor variability between skill levels was present within individual athletes (intra-individual) and between athletes (inter-individual). This result was independent of the criteria used to define expertise, the type of instrumentation used, and the metrics used to quantify motor variability.

Exploring the Real-Time Variability and Complexity of Sitting Patterns in Office Workers with Non-Specific Chronic Spinal Pain and Pain-Free Individuals.

Chronic spinal pain (CSP) is a prevalent condition, and prolonged sitting at work can contribute to it. Ergonomic factors like this can cause changes in motor variability. Variability analysis is a useful method to measure changes in motor performance over time. When performing the same task multiple times, different performance patterns can be observed. This variability is intrinsic to all biological systems and is noticeable in human movement. This study aims to examine whether changes in movement variability and complexity during real-time office work are influenced by CSP. The hypothesis is that individuals with and without pain will have different responses to office work tasks. Six office workers without pain and ten with CSP participated in this study. Participant's trunk movements were recorded during work for an entire week. Linear and nonlinear measures of trunk kinematic displacement were used to assess movement variability and complexity. A mixed ANOVA was utilized to compare changes in movement variability and complexity between the two groups. The effects indicate that pain-free participants showed more complex and less predictable trunk movements with a lower degree of structure and variability when compared to the participants suffering from CSP. The differences were particularly noticeable in fine movements.

Social networks as a lever for active learning and development of cognitive and technical skills in long jump: a study among Tunisian middle school students

The study was conducted on a sample of 112 students divided into two groups; the experimental group (n = 56; age = 15.46 ± 0.50; body mass = 63.03 ± 3.93; height = 166.09 ± 4.79) and the control group (n = 56, age = 15.55 ± 0.56; body mass = 63.87 ± 4.40; height = 165.8 ± 4.92). The experiment examined the integration of ICT in physical education during a cycle of eight sessions of long jump. The objective of the study was to measure the cognitive and motor variables of each group to test the effect of this integration on the students' skills.

Cognitive training and promoting a healthy lifestyle for individuals with isolated REM sleep behavior disorder: study protocol of the delayed-start randomized controlled trial CogTrAiL-RBD

BackgroundIsolated REM sleep behavior disorder (iRBD) is an early α-synucleinopathy often accompanied by incipient cognitive impairment. As executive dysfunctions predict earlier phenotypic conversion from iRBD to Parkinson’s disease and Lewy body dementia, cognitive training focusing on executive functions could have disease-modifying effects for individuals with iRBD.MethodsThe study CogTrAiL-RBD investigates the short- and long-term effectiveness and the feasibility and underlying neural mechanisms of a cognitive training intervention for individuals with iRBD. The intervention consists of a 5-week digital cognitive training accompanied by a module promoting a healthy, active lifestyle. In this monocentric, single-blinded, delayed-start randomized controlled trial, the intervention’s effectiveness will be evaluated compared to an initially passive control group that receives the intervention in the second, open-label phase of the study. Eighty individuals with iRBD confirmed by polysomnography will be consecutively recruited from the continuously expanding iRBD cohort at the University Hospital Cologne. The evaluation will focus on cognition and additional neuropsychological and motor variables. Furthermore, the study will examine the feasibility of the intervention, effects on physical activity assessed by accelerometry, and interrogate the intervention’s neural effects using magnetic resonance imaging and polysomnography. Besides, a healthy, age-matched control group (HC) will be examined at the first assessment time point, enabling a cross-sectional comparison between individuals with iRBD and HC.DiscussionThis study will provide insights into whether cognitive training and psychoeducation on a healthy, active lifestyle have short- and long-term (neuro-)protective effects for individuals with iRBD.Trial registrationThe study was prospectively registered in the German Clinical Trial Register (DRKS00024898) on 2022–03-11, https://drks.de/search/de/trial/DRKS00024898. Protocol version: V5 2023–04-24.

Applying different levels of practice variability for motor learning: More is not better.

Variable practice is a broadly used tool to improve motor learning processes. However, controversial results can be found in literature about the success of this type of practice compared to constant practice. This study explored one potential reason for this controversy: the manipulation of variable practice load applied during practice and its effects according to the initial performance level and the initial intrinsic variability of the learner. Sixty-five participants were grouped into four practice schedules to learn a serial throwing task, in which the training load of variable practice was manipulated: one constant practice group and three groups with different variable practice loads applied. After a pre-test, participants trained for 2 weeks. A post-test and three retests (96 h, 2 weeks and 1 month) were carried out after training. The participants' throwing accuracy was assessed through error parameters and their initial intrinsic motor variability was assessed by the autocorrelation coefficient of the error. The four groups improved their throwing performance. Pairwise comparisons and effect sizes showed larger error reduction in the low variability group. Different loads of variable practice seem to induce different performance improvements in a throwing task. The modulation of the variable practice load seems to be a step forward to clarify the controversy about its benefits, but it has to be guided by the individuals' features, mainly by the initial intrinsic variability of the learner.

Postural balance and cognitive functions: interaction and significance for rehabilitation (scientific review)

The study analyses the patterns of postural-cognitive interaction and their possible application in physical rehabilitation. The morphofunctional basis of the relationship between postural balance and cognitive functions is considered, particularly the role of the vestibular system in cognitive processes and the participation of cognitive functions in the regulation of equilibrium. The interaction patterns between postural balance and cognitive functions were analyzed, including the global nature of postural-cognitive interaction, influence of multitasking, and type of motor task (static or dynamic), its complexity, novelty and variability. The review presents the prospects and advantages of the practical application of the concept of postural-cognitive interaction in physical rehabilitation. These include the use of cognitive training methods in rehabilitation programs, which, due to the positive transfer of the effect of training, improves cognitive functions and postural stability and increases the ability to perform two or more tasks, including those related to activities of daily living. Vestibular training is another promising area of practical application of interaction between cognitive functions and postural balance; accordingly, vestibular–cognitive interaction contributes to the improvement of cognitive status. Considering the social significance of neurocognitive disorders and the importance of their early diagnosis, issues related to the identification of objective correlates and predictors of cognitive decline, particularly the basic spatial and spatiotemporal parameters of static posturography and stabilometric indices, are taken into account.

RECURRENT NEURAL NETWORK LEARNING ALGORITHM-BASED EVENT-TRIGGERED OBSERVER OF THE PERMANENT MAGNET SYNCHRONOUS MOTOR

In this paper, we propose a novel method to estimate the electrical angular velocity, the electrical angle, and the currents of the permanent magnet synchronous motor. A recurrent neural network learning algorithm is first developed to estimate the states of the permanent magnet synchronous motor. Then, an event-triggered state observer is designed for the recurrent neural network. This state observer robustly estimates state variables of the permanent magnet synchronous motor. A sufficient condition in terms of a convex optimization problem for the existence of the event-triggered state observer is established. In contrast with the abundance of state estimation methods based on time-triggered state observers where the measurements are always continuously available, the ones in this paper are updated when an event-triggered condition holds. Therefore, it lessens the stress on communication resources while can still maintain an estimation performance. Simulation results are provided to demonstrate the merit of the proposed method.

Effects of Speaking Rate Changes on Speech Motor Variability in Adults.

The relationship between speaking rate and speech motor variability was examined in three groups of neurotypical adults, n = 40; 15 young adults (18-30 years), 13 adults (31-40 years), and 12 middle-aged adults (41-50 years). Participants completed a connected speech task at three speaking rates (habitual, fast, and slow) where kinematic (lower lip movement) and acoustic data were obtained. Duration and variability were measured at each speaking rate. Findings revealed a complex relationship between speaking rate and variability. Adults from the middle age range (31-40 years) demonstrated shorter acoustic and kinematic durations compared with the oldest age group (41-50 years) during the habitual speaking rate condition. All adults demonstrated the greatest variability in the slow speaking rate condition, with no significant differences in variability between habitual and fast speaking rates. Interestingly, lip aperture variability was significantly lower in the youngest age group (18-30 years) compared with the two older groups during the fast speaking rate condition. Differences in measures of acoustic variability were not observed across the age levels. Strong negative correlations between kinematic/acoustic duration and lip aperture/acoustic variability in the youngest age group were revealed. Therefore, while a slow speaking rate does result in greater variability compared with habitual and fast speaking rates, longer durations of productions by the different age groups were not linked to higher spatiotemporal index (STI) values, suggesting that timing influences speech motor variability, but is not the sole contributor.

Same principle, but different computations in representing time and space.

Time and space are two intertwined contexts that frame our cognition of the world and have shared mechanisms. A well-known theory on this case is "A Theory of Magnitude (ATOM)" which states that the perception of these two domains shares common mechanisms. However, evidence regarding shared computations of time and space is intermixed. To investigate this issue, we asked human subjects to reproduce time and distance intervals with saccadic eye movements in similarly designed tasks. We applied an observer model to both modalities and found underlying differences in the processing of time and space. While time and space computations are both probabilistic, adding priors to space perception minimally improved model performance, as opposed to time perception which was consistently better explained by Bayesian computations. We also showed that while both measurement and motor variability were smaller in distance than time reproduction, only the motor variability was correlated between them, as both tasks used saccadic eye movements for response. Our results suggest that time and space perception abide by the same algorithm but have different computational properties.

The too many facets of motor output variability. Comment on “From neural noise to co-adaptability: Rethinking the multifaceted architecture of motor variability” by Casartelli, L., Maronati, C., & Cavallo, A.

The too many facets of motor output variability. Comment on “From neural noise to co-adaptability: Rethinking the multifaceted architecture of motor variability” by Casartelli, L., Maronati, C., & Cavallo, A.

Auditory feedback decreases timing variability for discontinuous and continuous motor tasks in autistic adults.

Autistic individuals demonstrate greater variability and timing error in their motor performance than neurotypical individuals, likely due at least in part to atypical cerebellar characteristics and connectivity. These motor difficulties may differentially affect discrete as opposed to continuous movements in autistic individuals. Augmented auditory feedback has the potential to aid motor timing and variability due to intact auditory-motor pathways in autism and high sensitivity in autistic individuals to auditory stimuli. This experiment investigated whether there were differences in timing accuracy and variability in autistic adults as a function of task (discontinuous vs. continuous movements) and condition (augmented auditory feedback vs. no auditory feedback) in a synchronization-continuation paradigm. Ten autistic young adults aged 17-27 years of age completed the within-subjects study that involved drawing circles at 800 milliseconds intervals on a touch screen. In the discontinuous task, participants traced a series of discrete circles and paused at the top of each circle for at least 60 milliseconds. In the continuous task, participants traced the circles without pausing. Participants traced circles in either a non-auditory condition, or an auditory condition in which they heard a tone each time that they completed a circle drawing. Participants had significantly better timing accuracy on the continuous timing task as opposed to the discontinuous task. Timing consistency was significantly higher for tasks performed with auditory feedback. This research reveals that motor difficulties in autistic individuals affect discrete timing tasks more than continuous tasks, and provides evidence that augmented auditory feedback may be able to mitigate some of the timing variability present in autistic persons' movements. These results provide support for future investigation on the use of music-based therapies involving auditory feedback to address motor dysfunction in autistic individuals.

Assessing Motor Variability during Squat: The Reliability of Inertial Devices in Resistance Training.

Movement control can be an indicator of how challenging a task is for the athlete, and can provide useful information to improve training efficiency and prevent injuries. This study was carried out to determine whether inertial measurement units (IMU) can provide reliable information on motion variability during strength exercises, focusing on the squat. Sixty-six healthy, strength-trained young adults completed a two-day protocol, where the variability in the squat movement was analyzed at two different loads (30% and 70% of one repetition maximum) using inertial measurement units and a force platform. The time series from IMUs and force platforms were analyzed using linear (standard deviation) and non-linear (detrended fluctuation analysis, sample entropy and fuzzy entropy) measures. Reliability was analyzed for both IMU and force platform using the intraclass correlation coefficient and the standard error of measurement. Standard deviation, detrended fluctuation analysis, sample entropy, and fuzzy entropy from the IMUs time series showed moderate to good reliability values (ICC: 0.50-0.85) and an acceptable error. The study concludes that IMUs are reliable tools for analyzing movement variability in strength exercises, providing accessible options for performance monitoring and training optimization. These findings have implications for the design of more effective strength training programs, emphasizing the importance of movement control in enhancing athletic performance and reducing injury risks.

Embodimetrics: A Principal Component Analysis Study of the Combined Assessment of Cardiac, Cognitive and Mobility Parameters.

There is a growing body of literature investigating the relationship between the frequency domain analysis of heart rate variability (HRV) and cognitive Stroop task performance. We proposed a combined assessment integrating trunk mobility in 72 healthy women to investigate the relationship between cognitive, cardiac, and motor variables using principal component analysis (PCA). Additionally, we assessed changes in the relationships among these variables after a two-month intervention aimed at improving the perception-action link. At baseline, PCA correctly identified three components: one related to cardiac variables, one to trunk motion, and one to Stroop task performance. After the intervention, only two components were found, with trunk symmetry and range of motion, accuracy, time to complete the Stroop task, and low-frequency heart rate variability aggregated into a single component using PCA. Artificial neural network analysis confirmed the effects of both HRV and motor behavior on cognitive Stroop task performance. This analysis suggested that this protocol was effective in investigating embodied cognition, and we defined this approach as "embodimetrics".