Bernstein's theory of movement behavior: historical development and contemporary relevance

Increasing load carriage and running speed differentially affect the magnitude, variability and coordination patterns of muscle forces

The study aims to investigate the effects of different loads and speed during running on inter- and intra-individual muscle force amplitudes, variabilities and coordination patterns. Nine healthy participants ran on an instrumentalized treadmill with an empty weight vest at two velocities (2.6 m/s and 3.3 m/s) or while carrying three different loads (4.5, 9.1, 13.6 kg) at 2.6 m/s while kinematics and kinetics were synchronously recorded. The major lower limb muscle forces were estimated using a musculoskeletal model. Muscle force amplitudes and variability, as well as coordination patterns were compared at the group and at the individual level using respectively statistical parametric mapping and covariance matrices combined with multidimensional scaling. Increasing the speed or the load during running increased most of the muscle force amplitudes (p < 0.01). During the propulsion phase, increasing the load increased muscle force variabilities around the ankle joint (modification of standard deviation up to 5% of body weight (BW), p < 0.05) while increasing the speed decreased variability for almost all the muscle forces (up to 10% of BW, p < 0.05). Each runner has a specific muscle force coordination pattern signature regardless of the different experimental conditions (p < 0.05). Yet, this individual pattern was slightly adapted in response to a change of speed or load (p < 0.05). Our results suggest that adding load increases the amplitude and variability of muscle force, but an increase in running speed decreases the variability. These findings may help improve the design of military or trail running training programs and injury rehabilitation by progressively increasing the mechanical load on anatomical structures.

Coupled and Synchronization Models of Rhythmic Arm Movement in Planar Plane

Nonlinear dynamics have become a new perspective on model human movement variability; however, it is still a debate whether chaotic behavior is indeed possible to present during a rhythmic movement. This paper reports on the nonlinear dynamical behavior of coupled and synchronization models of a planar rhythmic arm movement. Two coupling schemes between a planar arm and an extended Duffing-Van der Pol (DVP) oscillator are investigated. Chaos tools, namely phase space, Poincare section, Lyapunov Exponent (LE), and heuristic approach are applied to observe the dynamical behavior of orbit solutions. For the synchronization, an orientation angle is modeled as a single well DVP oscillator implementing a Proportional Derivative (PD)-scheme. The extended DVP oscillator is used as a drive system, while the orientation angle of the planar arm is a response system. The results show that the coupled system exhibits very rich dynamical behavior where a variety of solutions from periodic, quasi-periodic, to chaotic orbits exist. An advanced coupling scheme is necessary to yield the route to chaos. By modeling the orientation angle as the single well DVP oscillator, which can synchronize with other dynamical systems, the synchronization can be achieved through the PD-scheme approach.

Inter-strides variability affects internal foot tissue loadings during running

Running overuse injuries result from an imbalance between repetitive loadings on the anatomical structures and their ability to adapt to these loadings. Unfortunately, the measure of these in-vivo loadings is not easily accessible. An optimal amount of movement variability is thought to decrease the running overuse injury risk, but the influence of movement variability on local tissue loading is still not known. A 3D dynamic finite element foot model driven by extrinsic muscle forces was developed to estimate the stress undergone by the different internal foot structures during the stance phase. The boundary conditions of different trials with similar running speed were used as input. Variability in bone stress (10%) and cartilage pressure (16%) can be expected while keeping the overall running speed constant. Bone and cartilage stress were mainly influenced by the muscle force profiles rather than by ground reaction force. These findings suggest, first, that the analysis of a single trial only is not representative of the internal tissue loadings distribution in the foot and second, that muscle forces must be considered when estimating bone and cartilage loadings at the foot level. This model could be applied to an optimal clinical management of the overuse injury.

Scapular motion is accelerated in asymptomatic individuals with dyskinesis: An observational study

INTRODUCTION

Individuals with shoulder and upper extremity pathology often present with altered scapular motion. Few studies have looked at variations in scapular acceleration as a way of quantifying scapular motion. The purpose was to determine the effectiveness of wireless accelerometers for detecting changes in acceleration in individuals with scapular dyskinesis.

MATERIALS/METHODS

Twenty-seven asymptomatic college students (mean age 24 (SD ± 1.54), 65% female, 93% right handed) were visually screened for scapular dyskinesis using previously described criteria. Of the students recruited, fifteen students were determined to have scapular dyskinesis. After securing a wireless accelerometer (MyoResearch 3D DTS) on the dominate scapula, the participants performed five repetitions of standing scaption from 0 to 140°. Linear scapular accelerations along three orthogonal axes (frontal-y, transverse-z, and sagittal-x) were collected. Intraclass correlation coefficients (ICC_{3, k}) were used to determine the between day intra-rater reliability while a one-way analysis of variance was used to determine differences in acceleration between those with and without dyskinesis.

RESULTS

There was good between day intra-rater reliability for the average of all three axes (ICC = 0.79) and for the x and y axes (ICC > 0.78). Reliability was poor (ICC = 0.31) for the z-axis. There was a significant increase in overall acceleration of the scapula in those with dyskinesis (p = .039). There was also a significant increase in acceleration along the y-axis for those with dyskinesis (p = .003) but not for the other axes (p > .16).

CONCLUSION

Wireless accelerometers reliably quantify scapular acceleration in healthy individuals. In a healthy population with dyskinesis, the overall magnitude of scapular acceleration was greater when compared to a healthy group without dyskinesis.

Motor Learning, Neuroplasticity, and Strength and Skill Training: Moving From Compensation to Retraining in Behavioral Management of Dysphagia

Purpose Learning a motor skill and regaining a motor skill after it is lost are key tenets to the field of speech-language pathology. Motor learning and relearning have many theoretical underpinnings that serve as a foundation for our clinical practice. This review article applies selective motor learning theories and principles to feeding and swallowing across the life span. Conclusion In reviewing these theoretical fundamentals, clinical exemplars surrounding the roles of strength, skill, experience, compensation, and retraining, and their influence on motor learning and plasticity in regard to swallowing/feeding skills throughout the life span are discussed.

Comparing supraspinatus to acromion proximity and kinematics of the shoulder and thorax between manual wheelchair propulsion styles: A pilot study

BACKGROUND

Repetitive glenohumeral joint movement during manual wheelchair propulsion has been associated with shoulder pain in individuals with spinal cord injury. Clinical guidelines for shoulder health maintenance encourage semi-circular over arc propulsion to reduce loading frequency. This study aimed to determine the difference in estimated supraspinatus to acromion compression risk, and shoulder, thorax kinematics between (1) arc and semi-circular propulsion; and (2) self-selected and coached strategies.

METHODS

Shoulder and thorax kinematics were captured during wheelchair propulsion, noting individually self-selected styles. Participants were then coached to perform the other style(s) of interest, arc and/or semi-circular. CT bone models of the humerus and scapula were animated using glenohumeral kinematics to estimate the minimum distance between the supraspinatus humeral attachment and the acromion. Compression risk was defined as the proportion of each propulsion phase where the minimum distance fell below 5 mm. Comparisons were made between conditions evaluating compression risk, minimum distances and kinematics at events throughout propulsion.

FINDINGS

Ten individuals with spinal cord injury (9 male) participated. Arc and semi-circular propulsion did not significantly differ in compression risk or minimum distance across propulsion phases. Self-selected styles yielded lower compression risk and larger proximity values compared to coached styles. Glenohumeral horizontal abduction and thorax flexion differed between arc and semi-circular propulsion. Multiple glenohumeral and humerothoracic differences emerged between self-selected and coached conditions.

INTERPRETATION

Supraspinatus compression was observed during both arc and semi-circular propulsion, suggesting risk may be unavoidable in this task. Self-selected styles yield less risk, likely related to coached style unfamiliarity.

Movement analysis in early infancy: Towards a motion biomarker of age

BACKGROUND

Early motor development is characterized by progressive changes in general movements paralleled by a gradual organization of the four limbs' repertoire towards the midline, as shown by computerised movement analysis.

AIMS

Our aim was to test the performance of quantitative computerised kinematic indexes as predictors of post-term age in an independent cohort of typically developing subjects at fidgety age, tested cross-sectionally.

SUBJECTS

We selected twelve low risk term infants, who were video recorded between 9 and 20 weeks (fidgety age) during one spontaneous movements session.

STUDY DESIGN

We correlated post-term age with I)indexes of coordination including interlimb correlation of velocity and position, II)indexes of distance, including interlimb and limb-to- ground, both expressed as linear distance and as probability of midline limbs position III)indexes of global movement quality by calculating Hjorth's activity, mobility and complexity parameters. All indexes were calculated for both upper and lower limbs.

RESULTS

Significant positive correlations were found between post-term age and indexes of distance, and probability of occurrence of upper-limb antigravity patterns, and with both indexes of global movement quality. By combining linear and non-linear parameters related to the upper limb kinematics, we determined individual post-term age with a mean error of <1 week (5.2 days). No correlations were found between age and indexes of coordination.

CONCLUSIONS

Quantitative computerised analysis of upper-limb movements is a promising predictor of post-term age in typically developing subjects at fidgety age.

Synergies in coordination: a comprehensive overview of neural, computational, and behavioral approaches

At face value, the term "synergy" provides a unifying concept within a fractured field that encompasses complementary neural, computational, and behavioral approaches. However, the term is not used synonymously by different researchers but has substantially different meanings depending on the research approach. With so many operational definitions for the one term, it becomes difficult to use as either a descriptive or explanatory concept, yet it remains pervasive and apparently indispensable. Here we provide a summary of different approaches that invoke synergies in a descriptive or explanatory context, summarizing progress, not within the one approach, but across the theoretical landscape. Bernstein's framework of flexible hierarchical control may provide a unifying framework here, since it can incorporate divergent ideas about synergies. In the current motor control literature, synergy may refer to conceptually different processes that could potentially operate in parallel, across different levels within the same hierarchical control scheme. There is evidence for the concurrent existence of synergies with different features, both "hard-wired" and "soft-wired," and task independent and task dependent. By providing a comprehensive overview of the multifaceted ideas about synergies, our goal is to move away from the compartmentalization and narrow the focus on one level and promote a broader perspective on the control and coordination of movement.

Tensometric tremorography in high-precision medical diagnostic systems

BACKGROUND

The objective of the study was to develop a system for the precision diagnostics of pathologies of motor brain regions based on tensometric measurement and to explore its diagnostic capabilities.

MATERIALS AND METHODS

Tremor is a syndrome that indicates the abnormal state of the central nervous system, primarily in the motor brain regions. Analysis of tremor parameters provides significant information about the changes in the body motion control and can be used as an objective index of the central nervous system state. Existing methods are aimed at the analysis of visible tremor based on the use of different sensors. We suggest an alternative approach based on the use of a tensometric system performing tremor measurements when the tremor appears on the background of voluntary isometric efforts. The key advantage of our approach is that it allows to determine the tremor before its visible manifestation. In the article, we describe hardware implementation of our tremor analysis system.

RESULTS

In the article, we represent the new methodology and the original equipment based on the control of isometric effort. Isometric effort formed by a patient is controlled with the use of a feedback system on the patient's monitor. We evaluated the performance of our equipment with more than 400 healthy volunteers and patients with various pathologies of the central nervous system motor regions, and the results of the investigations, allowing to identify tremor parameters typical for parkinsonism, are represented in our article.

CONCLUSION

Testing of the system confirmed its high diagnostic validity and reliability, high sensitivity, simplicity and high speed of information processing. The approach based on tensometric measurements is very promising for the diagnostics of Parkinson disease and dysfunctions of a central nervous system.

Application of motor learning in neurorehabilitation: a framework for health-care professionals

Learning motor skills is an essential part of most rehabilitation processes. Facilitating and supporting motor learning is particularly challenging in neurological rehabilitation: patients who suffer from neurological diseases experience both physical limitations and difficulties of cognition and communication that affect and/or complicate the motor learning process. Therapists (e.g. physiotherapists and occupational therapists) who work in neurorehabilitation are therefore continuously searching for the best way to facilitate patients during these intensive learning processes. To support therapists in the application of motor learning, a framework was developed, integrating knowledge from the literature and the opinions and experiences of international experts. This article presents the framework, illustrated by cases from daily practice. The framework may assist therapists working in neurorehabilitation in making choices, implementing motor learning in routine practice, and supporting communication of knowledge and experiences about motor learning with colleagues and students. The article discusses the framework and offers suggestions and conditions given for its use in daily practice.

Functional systems theory and the activity-specific approach in psychological taxonomies

This brief opinion contribution reflects on the application of Anokhin's functional systems theory in the development of models of temperament in Russian differential psychophysiology. It points to the benefits of using an activity-specific approach in temperament theory. This approach suggests separating traits related to physical, communicative and mental aspects of behaviour.This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.

Functionality versus dimensionality in psychological taxonomies, and a puzzle of emotional valence

This paper applies evolutionary and functional constructivism approaches to the discussion of psychological taxonomies, as implemented in the neurochemical model Functional Ensemble of Temperament (FET). FET asserts that neurochemical systems developed in evolution to regulate functional-dynamical aspects of construction of actions: orientation, selection (integration), energetic maintenance, and management of automatic behavioural elements. As an example, the paper reviews the neurochemical mechanisms of interlocking between emotional dispositions and performance capacities. Research shows that there are no specific neurophysiological systems of positive or negative affect, and that emotional valence is rather an integrative product of many brain systems during estimations of needs and the capacities required to satisfy these needs. The interlocking between emotional valence and functional aspects of performance appears to be only partial since all monoamine and opioid receptor systems play important roles in non-emotional aspects of behaviour, in addition to emotionality. This suggests that the Positive/Negative Affect framework for DSM/ICD classifications of mental disorders oversimplifies the structure of non-emotionality symptoms of these disorders. Contingent dynamical relationships between neurochemical systems cannot be represented by linear statistical models searching for independent dimensions (such as factor analysis); nevertheless, these relationships should be reflected in psychological and psychiatric taxonomies.This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.

Critical and Theoretical Perspective on Scapular Stabilization: What Does It Really Mean, and Are We on the Right Track?

Stabilization exercises have been a focus and mainstay of many therapeutic and performance training programs in the past decade. Whether the focus is core stabilization for the spine or scapular stabilization, clinicians and trainers alike have endorsed these programs, largely on the basis of conceptual theory and anecdotal experience. The notion that an unstable scapula is related to shoulder dysfunction and pathology is well accepted, but is it accurate? The aim of this perspective article is to challenge the concept of scapular stabilization through the application of biomechanical and motor control constructs. The objectives are to critically examine current beliefs about scapular stabilization, to discuss definitions of stabilization and stability in the context of the scapulothoracic region, and to evaluate key evidence regarding scapular stabilization and scapular dyskinesia. Several new approaches that may affect the understanding of normal and atypical scapula motion are explored. Finally, a historical analogy is presented and future research and clinical directions are suggested. The aims are to lead readers to the essential concepts implied on scapular stabilization, to increase the critical thought process in rehabilitation practice, and to suggest some open topics to be explored in future research.

Force-displacement differences in the lower extremities of young healthy adults between drop jumps and drop landings

We measured ground reaction force and lower extremity shortening in ten healthy, young adults in order to compare five trials of drop jumps to drop landings. Our dependent variable was the percentage of displacement (shortening) between the markers on the ASIS and second metatarsal heads on each LE, relative to the maximum shortening (100% displacement) for that trial at the point of greatest ground reaction force. We defined this as "percent displacement at maximum force" (%dFmax). The sample mean %dFmax was 0.73%±0.14% for the drop jumps, and 0.47%±0.09% for the drop landings. The mean within-subject difference score was 0.26%±0.20%. Two-tailed paired t test comparing %dFmax between the drop jump and drop landing yielded P=0.002. For all participants in this study, the %dFmax was greater in drop jumps than in drop landings. This indicates that in drop jumps, the point of maximum force and of maximum shortening was nearly simultaneous, compared to drop landings, where the point of maximum shortening followed that of maximum force by a greater proportion. This difference in force to displacement behavior is explained by linear spring behavior in drop jumps, and linear damping behavior in drop landings.

Using Nonlinear Tools to Evaluate Movement of Fragile Objects

We investigated the movement strategies of young, healthy participants (7 men/7 women) during the movement of a fragile object using nonlinear analysis. The kinematic variables of position, velocity, and acceleration were quantified using largest Lyapunov exponent (LyE) and approximate entropy (ApEn) analysis to identify the structure of their movement variability and movement predictability, respectively. Subjects performed a total of 15 discrete trials of an upper extremity movement task without crushing the object at each fragility condition, using each hand (left/right). We tested four fragility conditions hypothesizing that an increase in fragility would result in higher movement predictability and decreased temporal variability. Comparisons between the structure of movement variability and movement predictability were based on fragility condition, handedness, and kinematic measures. In this specific population, object fragility and participant handedness did not significantly impact the structure of movement variability (LyE) in the primary direction of movement (Z direction), although some effects were observed in the anterior/posterior directions. ApEn values were minimized across conditions, showing increased movement predictability, and is suggested for the analysis of discrete kinematic movements. In healthy populations, the results of this study suggest minimal effects on task performance and movement predictability as a result of object fragility.

Influence of task on interlimb coordination in adults with cerebral palsy

OBJECTIVE

To examine movement time and kinematic properties of unilateral and bilateral reaching movements in adults with cerebral palsy (CP), focusing on how different types of bilateral movements, simultaneous or sequential, may influence interlimb coordination.

DESIGN

Quantitative study using between-group repeated-measures analyses.

SETTING

Motor control laboratory at a research university.

PARTICIPANTS

Adults with hemiplegic CP (n=11; mean age ± SD, 33±10y; 4 men) and age-matched controls (mean age ± SD, 32±9y; 4 men).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Movement time (MT), maximum deviation from a straight trajectory to the target, and peak speed.

RESULTS

Although adults with hemiplegic CP showed strong unilateral deficits, bilateral simultaneous reaching movements were temporally and spatially coupled. Movement of the less affected arm slowed to match the movement of the more affected arm. In contrast, bilateral sequential movements improved MTs of the less affected and more affected arms.

CONCLUSIONS

Bilateral sequential movements were conducive to faster MT compared with unilateral or bilateral simultaneous movements. Training that includes bilateral sequential movements may be beneficial to adults with hemiplegic CP. Upper-limb movements are coordinated in a variety of ways to perform routine bilateral tasks. Some bilateral tasks, such as stacking boxes, require more symmetric movements of the upper limbs. Other bilateral tasks, such as opening the refrigerator with 1 hand while placing an item on the shelf with the other hand, emphasize coordinated sequential action between upper limbs. Despite the prevalence of integrative upper-limb use, the control of different forms of bilateral movement is not well understood. A more comprehensive knowledge of upper-limb bilateral movements may hold important implications for developing more effective upper-limb movement therapies.

The effects of stride length and stride frequency on trunk coordination in human walking

In speeding-up normal walking, relative phase between horizontal thorax and pelvis rotations changes from more in-phase (synchronous) to more out-of-phase. In pathology (stroke, Parkinson's disease, low-back pain, pregnancy-related pelvic girdle pain), this often fails to happen. Even in healthy gait, however, these phenomena remain poorly understood. Thorax-pelvis relative phase may increase with either stride length, or stride frequency. Sixteen healthy male subjects walked on a treadmill at 0.5m/s, 1.0m/s, or 1.5m/s, with small, normal, or large steps. Increasing stride length (with lower frequency) led to larger spinal rotations, larger thorax-pelvis relative phase, and lower pelvis-leg relative phase, while the thorax continued to counterrotate with respect to the leg. With small steps, speeding-up hardly affected thorax-pelvis relative phase, and spinal amplitudes remained low. From a certain walking speed onwards, pelvis rotations start to contribute to stride length, and thus to speed (the "pelvic step"). This phenomenon appears to be driven, and the present study suggests, at least for higher speeds, that also thoracic counterrotations are driven, and not determined by the passive dynamics of the system. For patients, several strategies may exist to avoid large thorax-pelvis relative phase, and the concomitant large rotations of the spine: walking slowly, walking with small steps, adapting the timing of thorax rotations to that of the pelvis, or refraining from adapting the timing of pelvis rotations to the movements of the leg.

The loyal dissident: N.A. Bernstein and the double-edged sword of Stalinism

Nikolai Aleksandrovich Bernstein (1896-1966) studied movement in order to understand the brain. Contra Pavlov, he saw movements (thus, the brain) as coordinated. For Bernstein, the cortex was a stochastic device; the more cortexes an animal species has, the more variable its actions will be. Actions are planned with a stochastic "model of the future," and relevance is established through blind mathematical search. In the 1950 neoPavlovian affair, he came under strong attack and had to stop experimenting. It is argued that the consistency of his work derived both from both dialectical materialism and the relentless attacks of the neoPavlovians.

Correlates of measures of voluntary force with the functional state of the motor system

Oscillation spectra were analyzed for prolonged isometric force recorded in healthy subjects of three age groups. Changes in the distributions of spectral components of the oscillations in force were noted, along with differences in the distributions of spectral density as exhaustion developed in the age groups. The amplitude-frequency ranges of changes in the spectral densities of oscillations in force characterized the activity at the suprasegmental and segmental levels of the motor system which support the voluntary control and automatic regulation of posture during the performance of movements. Correlates of the functional state of the motor system are discussed in terms of the voluntary and involuntary components of control. A significant increase in activity in the central structures of the movement control system was seen with the development of exhaustion, along with decreases in the frequency range of the activity of subcortical structures with age.

Approximate Optimal Control as a Model for Motor Learning

Current models of psychological development rely heavily on connectionist models that use supervised learning. These models adapt network weights when the network output does not match the target outputs computed by some agent. The authors present a model of motor learning in which the child uses exploration to discover appropriate ways of responding. The model is consistent with what is known about how neural systems evaluate behavior. The authors model the development of reaching and investigate N. Bernstein's (1967) hypotheses about early motor learning. Simulations show the course of learning as well as model the kinematics of reaching by a dynamical arm.