bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Muscle Fatigue on Position Sense in an Upper Limb Multi-joint Task
Authors: Vafadar Amirhossein K. , Côté Julie N. , Archambault Philippe S.
Published: August 2016

The purpose of this study was to estimate the extent to which muscle fatigue can impact on the position sense in the upper limb. Twelve healthy volunteers were asked to do a reaching task while grasping a wooden block and match the block’s position with a corresponding target displayed on a flat screen, without vision. Following that, subjects performed resistive exercises with Thera-band strips until fatigue was induced and then the position sense task was repeated. A significant change in the endpoint position was observed after fatigue, in the up/down direction (p ≤ .001). The variability of endpoint positions in up/down direction was also significantly increased after fatigue (p ≤.03). There was no significant change in endpoint orientation but there was a significant fatigue × orientation effect on endpoint rotational variability. In a follow-up experiment, a group of subjects repeated the same protocol, but with a period of quiet rest between the two position sense tasks. In that group, there were no differences in endpoint position, orientation or variability. Muscle fatigue is an important factor that should be taken into consideration during the treatment of musculoskeletal injuries as well as athletic training.
Phase-Dependent Respiratory-Motor Interactions in Reaction Time Tasks During Rhythmic Voluntary Breathing
Authors: Li Sheng , Park Woo-Hyung , Borg Adam
Published: August 2016

The study investigated squeezing reaction time (RT) in response to a visual cue during rhythmic voluntary breathing at 0.6 Hz paced by a metronome, breath holding, or at rest in 13 healthy subjects. Rhythmic voluntary breathing slowed down RT, only in the expiratory phase with accompanied changes in the length of respiratory phases, while breath-holding reduced RT. The prolonged RT during voluntary expiratory phases and the absence of changes in RT during voluntary inspiratory phases are most likely related to disproportionally increased cognitive demands during the expiratory phase of voluntary breathing. The absence of changes in RT during voluntary inspiration is likely to be compensated by respiratory-motor facilitation mechanisms in this phase. Shortened RT during breath holding is possibly associated with increased attention.
Relationship Between Muscle Cocontraction and Proficiency in Whole-Body Sensorimotor Synchronization: A Comparison Study of Street Dancers and Nondancers
Authors: Miura Akito , Kudo Kazutoshi , Ohtsuki Tatsuyuki , Kanehisa Hiroaki , Nakazawa Kimitaka
Published: August 2016

In this study, we investigated muscle cocontraction during a street dance movement task to provide evidence that the level of muscle cocontraction is associated with degree of proficiency in whole-body sensorimotor synchronization movement. Skilled street dancers and nondancers were required to synchronize a knee-bending movement in a standing position to a metronome beat. The dancer group showed significantly smaller variability of temporal deviation (defined as the peak kneeflexion time minus beat onset time), and lower level of muscle cocontraction analyzed by electromyographic data of the agonist and antagonist muscles of the upper and lower leg than did the nondancer group. In addition, multiple regression analyses revealed that the group effect significantly predicted the level of muscle cocontraction. These results show that the level of muscle cocontraction in the lower limbs during whole-body sensorimotor synchronization movement is associated with the degree of proficiency of the movement.
Freely Chosen Cadence During a Covert Manipulation of Ambient Temperature
Authors: Hartley Geoffrey L. , Cheung Stephen S.
Published: August 2016

The present study investigated relationships between changes in power output (PO) to torque (TOR) or freely chosen cadence (FCC) during thermal loading. Twenty participants cycled at a constant rating of perceived exertion while ambient temperature (Ta) was covertly manipulated at 20-min intervals of 20 °C, 35 °C, and 20 °C. The magnitude responses of PO, FCC and TOR were analyzed using repeated-measures ANOVA, while the temporal correlations were analyzed using Auto-Regressive Integrated Moving Averages (ARIMA). Increases in Ta caused significant thermal strain (p < .01), and subsequently, a decrease in PO and TOR magnitude (p < .01), whereas FCC remained unchanged (p = .51). ARIMA indicates that changes in PO were highly correlated to TOR (stationary r2 = .954, p = .04), while FCC was moderately correlated (stationary r2 = .717, p = .01) to PO. In conclusion, changes in PO are caused by a modulation in TOR, whereas FCC remains unchanged and therefore, unaffected by thermal stressors.
Facilitating the Use of Online Visual Feedback: Advance Information and the Inter-Trial Interval?
Authors: Cheng Darian T. , Manson Gerome A. , Kennedy Andrew , Tremblay Luc
Published: August 2016

Cheng et al. (2008) showed that when goal-directed reaching movements are performed with a 2.5 s inter-trial interval (ITI) under a randomized visual feedback schedule, individuals use online visual information on trial n to perform efficient online corrections on trial n + 1 (i.e., “reminiscence” effect). These results persisted even when participants were given knowledge of the up-coming vision condition. In this study, the ITI was extended to 5 s in an attempt to negate any effects of the preceding trial. Results from this study revealed that trials with vision were always more accurate than trials performed without vision, suggesting that individuals relied significantly on online information. Furthermore, aiming precision improved when participants knew the vision condition before each trial. It is thus suggested that the reminiscence effects are not longer evident with a 5 s ITI, which in turn allows prior knowledge of visual feedback to influence the use of online vision.
The Control of Sequential Goal-Directed Movement: Learning to Use Feedback or Central Planning?
Authors: Elliott Digby , Ricker Kathryn L. , Lyons James
Published: August 2016

Fifteen participants practiced a two-target sequential aiming movement with either full vision of the movement environment, vision during flight, or vision while in contact with the first target. After 100 acquisition trials, participants performed a retention test in their own condition and then were transferred to each of the other two vision conditions. Both performance and kinematic data indicated that rather than becoming less dependent on visual information with practice, subjects learned to adjust their movement trajectories to use the visual information available in their particular vision condition. Although transfer to a degraded vision condition disrupted performance, when vision was augmented participants quickly adjusted their aiming trajectories to use the added information. The findings suggest that at least part of learning involves the development of rapid and efficient procedures for processing afferent information, including visual response-produced feedback.
Bimanual Circle Drawing during Secondary Task Loading
Authors: Summers Jeffery J. , Byblow Winston D. , Bysouth-Young Don F. , Semjen Andras
Published: August 2016

Seven right-handed participants performed bimanual circling movements in either a symmetrical or an asymmetrical coordination mode. Movements were paced with an auditory metronome at predetermined frequencies corresponding to transition frequency, where asymmetrical patterns became unstable, or at two-thirds transition frequency, where both symmetrical and asymmetrical patterns were stable. The pacing tones were presented in either a high (1000 Hz) or low (500 Hz) pitch, and the percentage of high-pitched tones during a 20 s trial varied between 0% and 70%. Participants were instructed to count the number of high-pitched pacing tones that occurred during a trial of bimanual circling. Overall, the symmetrical pattern was more stable than the asymmetrical pattern at both frequencies. Errors on the tone-counting task were significantly higher during asymmetrical circling than symmetrical circling but only at the transition movement frequency. The results suggest that cognitive processes play a role in maintaining coordination patterns within regions of instability.
Lip and Tongue Function in Multiple Sclerosis: A Physiological Analysis
Authors: Murdoch Bruce E. , Spencer Tracey J. , Theodoros Deborah G. , Thompson Elizabeth C.
Published: August 2016

A physiological analysis of the articulatory function of 16 adults with multiple sclerosis (MS) was performed using lip and tongue transduction systems. Sixteen nonneurologically impaired adults, matched for age, gender, and education, served as controls. The MS speakers demonstrated patterns of tongue function that were significantly different from those of the control speakers. Specifically, the MS speakers had significantly reduced tongue strength, endurance, and rate of repetitive movements. In addition, preclinical signs of lingual dysfunction were evident in nondysarthric MS speakers on endurance and rate tasks when compared to control subjects. These physiological findings could account for the perceptual findings of impaired articulation and reduced intelligibility. No lip dysfunction was revealed through either the physiological or the perceptual assessments.
Pointing to Remembered Targets in 3-D Space in Parkinson's Disease
Authors: Poizner Howard , Fookson Olga I. , Berkinblit Michail B. , Hening Wayne , Feldman Gregory , Adamovich Sergei
Published: August 2016

A three-dimensional tracking system was used to examine whether subjects with Parkinson's disease (PD) would show characteristic performance deficits in an unconstrained pointing task. Five targets were presented in a pyramidal array in space to 11 individuals with mild to moderate PD and 8 age-matched controls. After the target was indicated, subjects closed their eyes and pointed to the remembered target locations without vision. Despite the absence of visual feedback during movement, PD subjects were as accurate overall as controls. However, PD subjects showed greater variable errors, more irregular trajectories, and a vertical endpoint bias in which their endpoints were significantly lower than controls. They also showed deficiencies in the compensatory organization of joint rotations to ensure consistency in azimuthal (horizontal) positioning of the arm endpoint. We concluded that, under appropriate task conditions, PD subjects may not show overall deficits in accuracy even when making targeted movements at normal speed without visual feedback. Nevertheless, our findings indicate that there are certain dimensions of performance which are selectively altered in Parkinson's disease even when overall performance is normal.
Patterns of Center of Pressure Migration during Prolonged Unconstrained Standing
Authors: Duarte Marcos , Zatsiorsky Valdimir M.
Published: August 2016

Prolonged (>30 min) unconstrained standing (PUS) was studied in 10 young healthy subjects. The usual methods of stabilographic analysis assume a random center of pressure (COP) migration. This study was based on the opposite idea and showed that during PUS, specific and consistent patterns of the COP migration can be recognized by a computer algorithm. Three COP migration patterns were found: (a) shifting, a fast displacement of the average position of COP from one region to another; (b) fidgeting, a fast and large displacement and returning of COP to approximately the same position; and (c) drifting, a slow continuous displacement of the average position of COP. A software code was written and default parameter values were chosen for recognizing COP migration patterns. For 30-min PUS the following patterns were identified: Shifting was generally observed every 316 ± 292 sec in the anterior-posterior (a-p) direction with an average shift amplitude of 17 ± 15 mm, and every 199 ± 148 sec in the medial-lateral (m-1) direction with an average shift amplitude of 22 ± 38 mm. Corresponding time intervals for fidgeting were 59 ± 15 sec in the a-p direction and 49±16 sec in the m-1 direction. The average drift-to-drift interval was 319 ± 173 sec in the a-p direction and 529 ± 333 sec in the m-1 direction.
On Taking the Grasping out of Prehension
Authors: Newell Karl M. , Cesari Paola
Published: August 2016

Smeets and Brenner provide a very clear and useful statement of the work that has been stimulated by Jeannerod's 1984 paper but seem more concerned about the viability of model fitting than model assumptions. The theoretical and practical limitations of viewing “grasping as nothing more than pointing” are noted. We reemphasize the importance in prehension of the union of the hand with the object in the act of realizing a task goal.
The Reach-to-Grasp Movement: A New Look at an Old Problem?
Authors: Weir Patricia L.
Published: August 2016

This commentary raises some issues still unresolved in the study of the reach-to-grasp movement, namely the operational definition of the components of the reach-to-grasp movement, the independence of these components, and the equivocal interpretation of the existing literature. Lastly, this commentary addresses issues pertaining to object properties that require both visual and haptic determination.
Kinematic Characteristics of Aiming Movements as a Function of Temporal and Spatial Constraints
Authors: Yao Wan-Xiang , Fischman Mark G.
Published: August 2016

This study investigated, in aiming movements, the conditions needed to produce a single movement and those needed to produce secondary submovements. Using a 2 × 2 (Temporal Constraint × Spatial Constraint) factorial design with repeated measures on both factors, subjects moved a stylus from a starting position to a target position 12 cm away. They participated in two testing sessions on consecutive days. The first session involved two nonrestrictive target (a set of crosshairs) conditions, moving to the target either within a goal of 400 ms (temporal-accuracy procedure) or within a minimum time (time-minimization procedure). In the second session the subjects performed two strict-target (circle) conditions, moving to the target either within a goal of 400 ms or within a minimum time. The results showed that the two strict-target conditions had a greater percentage of trials containing multiple-submovements than the two nonrestrictive target conditions, regardless of temporal requirements. Therefore, whether an aiming movement contains a single movement or multiple submovements may be a function of spatial constraints regardless of temporal constraints. It appears that with respect to the nature of the speed-accuracy tradeoff, spatial constraints are an important factor.
Grasping Neurones
Authors: Smeets Jeroen B.J. , Brenner Eli
Published: August 2016

We agree with Robertson that our new view on grasping is a description of motor behavior rather than an exploration into the nature of the neural processing underlying this behavior. However, neurophysiologists might be inspired by our new view to ask other questions, perform other experiments, and analyze these differently. In this way, they could generate new insights about the neural control of grasping.
Overcomplete Musculature or Underspecified Tasks?
Authors: Loeb Gerald E.
Published: August 2016

The number of muscles in the body is actually fairly close to the number required to control completely all its degrees of freedom. The apparent need for a coordinating principle arises from the experimental practice of asking subjects to perform simple movements and assuming that they make no implicit assumptions about other constraints. Natural activities include implicit constraints that differ greatly for different tasks and circumstances and that would be met best by a nervous system free of a priori principles.
Vestibulopathy and the Age Effects on Protective Stepping during Unperturbed Standing
Authors: Krebs David E. , Velyvis Peter H. , Rogers Mark W.
Published: August 2016

This study examined the prevalence of protective stepping and accompanying preparatory postural responses associated with lateral weight transfer (WT) while subjects attempted to sustain stationary standing. The subjects were 92 healthy young and older adults and persons with vestibular hypo-function. Force platform and whole-body-motion recordings were used to evaluate the prevalence of stepping and WT responses during stationary standing (eyes open or closed) using a semi-tandem foot position. WT components were also evaluated for volitionally requested step initiation, and as a function of support base configuration and direction of stepping among younger subjects. Only 10% of trials by subjects with bilateral vestibular hypofunction (BVH) during semi-tandem standing with eyes closed were completed without a step, while 31% of subjects with UVH, 69% of healthy elders, and all young healthy subjects were able to stand for the entire 7-sec trials. WT responses always preceded volitional steps from a standard feet-parallel orientation but occurred in only 13% of the spontaneous steps. The prevalence of WT was influenced by the direction of volitional stepping from semi-tandem standing, but not by the initial standing width. Spontaneous stepping to maintain standing balance is a naturally occurring and prevalent behavior among older adults and persons with vestibular hypo-function during tests of quasi-static standing. Differences between volitional and spontaneous step initiation involving the prevalence of preparatory lateral WT are a complex function of motor planning, mechanical constraints, and functional context.
Vibration-Induced Postural Reaction Continues after the Contact with Additional Back Support
Authors: Talis Vera L. , Solopova Irina A
Published: August 2016

We investigated the development of postural reactions induced in standing subjects by Achilles tendon vibration. We compared vibratory reactions in 3 different conditions: normal standing, standing near support, and when the solid support being protracted forward changed the initial posture. Additional support for the back was placed at subject's sacral or shoulder level. In the easy standing condition, the postural vibration reaction consists of progressive backward upper body movement. When the body contacted the additional support on the sacral level during the vibratory reaction, the movement of the upper body continued in most of the subjects. This was accompanied by an increase of pressure on the toes. When the support was applied at the shoulder level, the body motion reversed its direction in half of the subjects. In this case, backward-forward oscillations occurred near the support. The initial change of body-support interaction did not influence the ensuing vibration reaction; namely the reaction was similar to that with the support near to the body at the sacral level. Our data demonstrate that the vibration-induced reaction is not a local reaction limited to one joint, but a complex postural synergy that involves both leg and trunk muscles and integrates the information from touch and pressure afferents of the upper body.
Relevance of the Force-Velocity Relationship in the Activation of Mono- and Bi-Articular Muscles in Slow Arm Movements in Humans
Authors: Welter Tom G. , Bobbert Maarten F. , van Bolhuis Bauke M. , Gielen Stan C.A.M. , Rozendaal Leonard A. , Veeger Dirkjan H.E.J.
Published: August 2016

We have investigated whether differences in EMG activity in mono- and bi-articuiar muscles for concentric and eccentric contractions (van Bolhuis, Gielen, & van Ingen Schenau, 1998) have to be attributed to a specific muscle coordination strategy or whether they are merely a demonstration of adaptations necessary to adjust for muscle contractile properties. Slow, multi-joint arm movements were studied in a horizontal plane with an external force applied at the wrist. Kinematics and electromyography data from 10 subjects were combined with data from a 3-D model of the arm and a Hill-type muscle model Data for both mono- and bi-articular muscles revealed a higher activation in concentric than in eccentric contractions. The model calculations indicated that the measured difference in activation (20%) was much larger than expected based on the force-velocity relationship (predicting changes of ~5%). Although these findings eliminate the force-velocity relationship as the main explanation for changes in EMG, it cannot be ruled out that other muscle contractile properties, such as history dependence of muscle force, determine muscle activation levels in the task that was studied.
Learning of a New Bimanual Coordination Pattern Is Governed by Three Distinct Processes
Authors: Wenderoth Nicole , Bock Otmar
Published: August 2016

Learning of a new bimanual coordination pattern was investigated by practicing rhythmical arm movements with a required relative phase of ϕ = 90°. To quantify the learning process, we determined the mean and the standard deviation of the relative phase, and the switching lime from a well-established coordination pattern to the to-be-leamed pattern. We then calculated for each parameter the time constant of improvement. We found that with practice, all three parameter improved but each following a significantly different time-course. We therefore conclude that the learning of a new bimanual coordination pattern is governed by three separate processes, which can be visualized in a potential landscape of the intrinsic dynamics as distinct topographical features—namely, the location, depth, and steepness of the attractor basin.
Planning Reaching and Grasping Movements: Simulating Reduced Movement Capabilities in Spastic Hemiparesis
Authors: Meulenbroek Ruud C.J. , Rosenbaum David A. , Vaughan Jonathan
Published: August 2016

In this paper we describe how a theory of posture-based motion planning recently applied to human grasping may contribute to the understanding of grasping pathology. The theory is implemented as a computer model rendered as a stick-figure animation capable of generating realistic multi-joint grasping movements. As shown here, the model can also be used to simulate grasping movements whose kinematics resemble those of grasps performed by people with spastic hemiparesis. The simulations demonstrate effects of: (a) reduced ranges of motion of arm joints on the size of the reachable workspace, (b) awkward starting postures on me time course of the hand closing around an object, (c) increased costs of joint rotations on movement time, and (d) addition of noise to biphasic joint rotations on the low-velocity phase of wrist transport.
Stability Boundaries and Lateral Postural Control in Parkinson's Disease
Authors: van Wegen Erwin E.H. , van Emmerik Richard E.A. , Wagenaar Robert C. , Ellis Terry
Published: August 2016

Postural instability is a major problem in patients with Parkinson's disease (PD). We examined balance control in PD by using center of pressure (CP) variability and time-to-contact to investigate boundary relevant postural control behavior under quiet stance leaning conditions. Postural orientation was manipulated by having patients (n = 10) and healthy older controls (n = 7)lean Forward and backward with varying degrees of lean on a force platform. The subjects were instructed to lean forward or backward (either halfway or as far as possible) without bending their hips or lifting their heels or toes off the ground. Time-to-contact of the CP with the geometric stability boundary defined by the feet as well as CP position and variability were analyzed. Mediolateral CP variability was increased in the patients with PD. Medio-lateral average time-to-contact was decreased in the patients but not so in the antcrior-posterior direction. In contrast to the CP variability, the medio-lateral variability of time-lo-contact was lower in the patients. Patients as well as healthy older controls responded to lean manipulations with an increase in CP variability. Boundary relevant CP measures thus show clear changes in control strategies and confirm the role of lateral instability in PD.
Corticospinal Control of Human Erector Spinae Muscles
Authors: Nowicky Alex V. , McGregor Alison H. , Davey Nick J.
Published: August 2016

We used transcranial magnetic stimulation (TMS) to study corticospinal excitability to erector Spinae (ES) muscles during graded voluntary contractions in bilateral trunk extension (BTE) and forced expiratory breath holding (FEBH) in normal individuals. Motor evoked potentials (MEPs) could be produced in all subjects in the absence of voluntary activation. At maximum voluntary contraction, levels of surface electromyographic (EMG) activity were 4 times greater during BTE than FEBH. When EMG was normalized to maximum. MEP amplitudes increased in proportion to contraction in both tasks. MEPs in FEBH were compared with extrapolated values at similar EMG levels in BTE and were found to be larger. EMG and MEPs in left and right ES were symmetrical throughout the range of contractions in both tasks. ES muscles have a facilitation pattern similar to that previously shown in leg muscles, but subtle differences at low levels of EMG suggest that the facilitation is dependent on the task.
Initial Muscle Activity in Planar Ballistic Arm Movements with Varying External Force Directions
Authors: Welter Tom G. , Bobbert Maarten F.
Published: August 2016

We have investigated, in fast movements, the hypothesis that bi-articular muscles are preferentially selected to control me direction of force exerted on the environment, while mono-articular muscles are selected to control both this exerted force direction as well as the movement direction. Fourteen subjects performed ballistic arm movements involving shoulder and elbow rotations in the horizontal plane, either with or without an external force applied at the wrist. Joint torques required to counteract the external force were in the same order of magnitude as those required to overcome the inertial load during movements. EMG was recorded from mono- and bi-articular flexors and extensors of me elbow and shoulder. Signals were rectified and integrated (IREMG) over 100 ms following the first detected activity. MANOVA revealed mat, contrary to the hypothesis, IREMG of bi-articular muscles varied with movement direction just as that of the mono-articular muscles. It was concluded that the present data do not support me hypothesis mentioned above. A second finding was that movement effects on IREMG were much stronger than external force effects. This could not be explained using Hill's force-velocity relationship. It may be an indication that in the initiation of fast movements, IREMG is not only tuned to movement dynamics and muscle contractile properties, but also to me dynamics of the build up of an active state of the muscle.
Goal-Equivalent Joint Coordination in Pointing: Affect of Vision and Arm Dominance
Authors: Tseng Yaweng , Scholz John P. , Schöner Gregor
Published: August 2016

This study used the uncontrolled manifold (UCM) approach to study joint coordination underlying the control of task-related variables important for success at reaching and pointing to targets. More combinations of joint motions are available to the control system to achieve task success than are strictly necessary. How this abundance of motor solutions is managed by the nervous system and whether and how the availability of visual information affects the solution to joint coordination was investigated in this study. The variability of joint angle combinations was partitioned into 2 components with respect to control of either the hand's path or the path of the arm's center of mass (CM). The goal-equivalent variability (GEV) component represents trial-to-trial fluctuations of the joint configuration consistent with a stable value of the hand or CM path. The other component, non-goal-equivalent variability (NGEV), led to deviations away from the desired hand or CM path. We hypothesized a style of control in which the NGEV component is selectively restricted while allowing a range of goal-equivalent joint combinations to be used to achieve stability of the hand and CM paths. Twelve healthy right-handed subjects reached across their body to the center of a circular target with both the right and left arms and with their eyes open or closed on different trials. When repeating the task with the same arm under identical task conditions, subjects used a range of goal-equivalent joint configurations to control the entire trajectory of both the hand's and the arm's CM motion, as well as the terminal position of the pointer-tip. Overall joint configuration variability was consistently larger in the middle of the movement, near the time of peak velocity. The style of joint coordination was qualitatively similar regardless of the arm used to point or the visual condition. Quantitative differences in the structure of joint coordination were present for the non-dominant arm, however, when pointing in the absence of vision of the hand and target. The results of this study suggest that the nervous system uses a control strategy that provides for a range of goal-equivalent, rather than unique, joint combinations to stabilize the values of important task-related variables, while selectively restricting joint configurations that change these values. The possible advantage of this style of control is discussed. Absence of vision during reaching affected joint coordination only quantitatively and only for the less skilled left arm, suggesting that the role of visual information may be greater when organizing the motor components of this arm.
Initial Arm Muscle Activation in a Planar Ballistic Arm Movement with Varying External Force Directions: A Simulation Study
Authors: Welter Tom G. , Bobbert Maarten F.
Published: August 2016

It has been shown in previous research that the initial phase of EMG for a punching movement remained almost unchanged regardless of whether an external force was applied to the arm. The purpose of the present study was to explain this finding with the help of simulations. A two-dimensional model of me arm actuated by 6 Hill-type muscles was used to simulate a punching movement in the horizontal plane from a prescribed starting position with 90° elbow flexion. Input to the model was the stimulation of me muscles, and output were, among others, muscle forces and segmental accelerations. A genetic algorithm was used to determine the muscle onset times mat minimized movement duration and targeting error. In a subsequent forward simulation, the optimized muscle onset times for an unloaded punching movement were superimposed on the isometric stimulation necessary to hold me arm in the starting position while an external force was applied to the arm. The resulting movement was only slightly different from the unloaded movement. It appeared that because of the low level of isometric muscle force prior to the movement, and the high level of stimulation during the movement, muscle force was increased at a rate mat was almost independent of the prior force level. These results confirmed the suggestion that the initial phase of EMG in ballistic movements is more related to the rate of change of force than to the absolute force level. It is hypothesized mat this may simplify the task of the nervous system in the choice of initial muscle activity in ballistic arm movements because no adjustments to varying external forces are required.
Symmetry of Discrete and Oscillatory Elbow Movements: Does It Depend on Torque That the Agonist and Antagonist Muscle Can Exert?
Authors: Mirkov Dragan M. , Milanovic Sladjan , Ilie Dusko B. , Jaric Slobodan
Published: August 2016

The hypothesis that strength of active muscles affects the symmetry of the velocity profiles of voluntary movements was tested. In particular, it was assumed that the duration of acceleration and deceleration phases reflects the ability of the antagonistic muscles to exert torque in such a way that stronger muscle requires less time for action. Twelve subjects performed consecutive 50° flexions and extensions in blocks of either discrete or oscillatory movements. They were tested under high and moderate speed conditions, as well as within different ranges of elbow joint angles. The symmetry ratio (SR; acceleration lime divided by deceleration time) was calculated in order to assess movement symmetry. The results demonstrated SR > 1 under most of the discrete and, particularly, oscillatory movement conditions. A velocity-associated increase in SR was recorded, while different ranges of elbow movements, assumed to provide different torques of the agonist and antagonist muscles, also provided different SR. The findings were generally in line with the predicted effects of movement conditions on muscle strength, particularly those related to elbow angle and elbow angular velocity. Deviations from me ideal movement symmetricity have usually been interpreted as either weakness of various motor control models and hypotheses, or as a sub-optimal control of movements in certain subject populations; the present study suggests an alternative interpretation based upon the ability of active muscles to exert torque.
Influence of Biomechanical Constraints on Horizontal Arm Movements
Authors: Dounskaia Natalia V. , Ketcham Caroline J. , Stelmach George E.
Published: August 2016

Influence of mechanical interactions between the shoulder and elbow on production of different coordination patterns during horizontal arm movements is investigated in the present study. Subjects performed cyclical movements along a circle and along lines of 4 different orientations. Cycling frequency was manipulated to highlight control features responsible for interactive torque regulation. When the shoulder was involved in motion, torque analysis revealed that this joint was controlled similarly during all movement types. At the elbow, however, each movement type required a specific pattern of regulation of interactive torque with muscle torque. When interactive torque acted in the direction of the required elbow rotation, the demands for active control were lower than when the interactive torque resisted elbow motion and had to be actively suppressed. Kinematic analysis demonstrated that increases in cycling frequency systematically deformed the fingertip path. The amount of these deformations differed across movement types, being more pronounced for movements where the interactive torque resisted joint motion. It appears that interactive torque can assist or resist movement at the joints, making control of some movement types more difficult than others.
Prism Exposure Affects the Proprioceptive Frames of Reference for Interlimb Rhythmic Coordination
Authors: Riley Michael A. , Black David P.
Published: August 2016

Adaptation to prisms can produce a change in felt arm position, termed proprioceptive shift. We studied the effects of prism-induced proprioceptive shift on interlimb rhythmic coordination performed under proprioceptive guidance, in the absence of vision. Relative to interlimb rhythmic coordination performed before prism exposure, the observed steady states of relative phase for postexposure coordination were shifted by a small but reliable amount. The shift was in the direction expected, given the direction of optical displacement. The amount of variability of interlimb rhythmic coordination was unaffected by prism exposure. The results suggest that the same spatial frames of reference altered by prism adaptation are involved in the production of interlimb rhythmic coordination patterns.
The Effect of Changes in the Body Configuration on Anticipatory Postural Adjustments
Authors: Aruin Alexander S.
Published: August 2016

A number of factors are likely to play a major role in the process of generation of anticipatory postural adjustments (APAs). Among them are the magnitude and direction of an expected perturbation, properties of a voluntary action associated with the perturbation, and features of the postural task such as a body's configuration prior to the action. The aim of this study was to analyze the effect of body configuration on APAs. Experiments were performed on 8 healthy subjects performing fast bilateral shoulder extension movements while standing. Body configuration was modified by instructions to the subjects to stand vertically or with a forward upper body bend varying from 15 to 60°. The electrical activity of postural muscles and displacements of the center of pressure were recorded. Results indicated that APAs were modified with changes in the angular position of the upper body. Decreased anticipatory activation was seen in rectus abdominis and rectus femoris, while increased anticipatory inhibition was observed in erecteor spinae and biceps femoris across conditions with forward bend. As a result, the total anticipatory activity of muscles in a muscle pair in series with a forward bend showed only slight modulation as compared to vertical posture. These results suggest that the CNS uses reorganization of the anticipatory activity of postural muscles by compensating for the changes in APAs of individual muscles in a muscle pair in such a way that the overall anticipatory activity of the muscle pair stays unchanged. Such compensation in counteracting the expected mechanical effects of the perturbation is used to accommodate both changes in the length of postural muscles and diminished stability of the body due to forward bend.
Acquisition of Operant-Trained Bipedal Locomotion in Juvenile Japanese Monkeys (Macaca Fuscata): A Longitudinal Study
Authors: Tachibana Atsumichi , Mori Futoshi , Boliek Carol A. , Nakajima Katsumi , Takasu Chijiko , Mori Shigemi
Published: August 2016

This study investigated developmental aspects of the acquisition of operant-trained bipedal (Bp) standing and Bp walking in the normally quadrupedal (Qp) juvenile Japanese monkey (M. fuscata). Four male monkeys (age: 1.6 to 2.4 years, body weight: 3.3 to 4.6 kg) were initially operantly trained to stand upright on a smooth floor and a stationary treadmill belt (width = 60 cm, walking length = 150 cm). They were then trained to walk bipedally on the moving treadmill belt (speed: 0.4–0.7 m/s). A regular training program (5 days/week; 30–60 min/day) was given to each monkey for the first 40 to 60 days, followed by less intensive training. After the beginning of locomotor training, upright postural stability and Bp walking capability were assessed kinematically for 592, 534, 526, and 537 days on monkeys A, B, C, and D, respectively. Left side- and back-views of the walking monkey were photographed (10 frames/s) and videotaped (250 frames/s). Stick figures of the head, body, and hindlimbs were drawn with reference to ink-marks positioned in front of the ear and over the pivot points of hindlimb joints. All kinematic data were digitized and analyzed using image-analyzing software. After sufficient physical growth and locomotor training, all the monkeys gradually acquired: (a) a more upright and a more stable posture with a constant body axis orientation during Bp locomotion; (b) a more stable and a stronger functional coupling between the body and hindlimb movements with a less anterior (A)-posterior (P) fluctuation of a body axis; (c) a smaller leftward (Lt)-rightward (Rt) displacement of the midline pelvic position, allowing the monkey to walk along a straight course; (d) a more coordinated relationship among hip-knee, knee-ankle, and ankle-metatarsophalangeal (MTP) joints; and finally (e) the acquisition of well-coordinated Bp walking even at high treadmill belt speeds up to 1.5 m/s. All of these results demonstrated the capability of the physically developing monkey to integrate the neural and musculoskeletal mechanisms required for sufficient coordination of upper (head, neck, trunk) and lower (hindlimbs) motor segments so that Bp standing and Bp walking could be elaborated.
Bimanual Directional Interference: The Effect of Normal versus Augmented Visual Information Feedback on Learning and Transfer
Authors: Puttemans Veerle , Vangheluwe Sophie , Wenderoth Nicole , Swinnen Stephan P.
Published: August 2016

When performing movements with different spatial trajectories in both upper limbs simultaneously, patterns of interference emerge that can be overcome with practice. Even though studies on the role of augmented feedback in motor learning have been abundant, it still remains to be discovered how overcoming such specific patterns of spatial interference can be optimized by instructional intervention. In the present study, one group acquired a bimanual movement with normal vision, whereas a second group received augmented feedback of the obtained trajectories on a computer screen in real time. Findings revealed that, relative to normal vision, the augmented feedback hampered skill learning and transfer to different environmental conditions. These observations are discussed in view of the benefits and pitfalls of augmented feedback in relation to task context and instructional condition.
Effect of Movement Termination in Single- and Dual-Phase Pointing Tasks
Authors: Roy Eric A. , Rohr Linda E. , Weir Patricia L.
Published: August 2016

Two experiments are reported that focus on manipulating both the context and the spatial precision of a computer-pointing task. Single goal-directed actions are compared to dual-phase tasks, where participants are required to sequentially attain two goal locations. Results support the idea that for movements in series, movement planning, and online feedback, control can occur simultaneously. Additionally, for single-phase tasks and the final phase of dual-phase tasks, the termination requirement influences the temporal components of the movement. The effects of termination and movement context appear to hold regardless of the spatial precision of the task. This suggests that the effects of spatial precision and movement termination are independent, although both have an impact on the deceleration time for goal-directed movements.
Bimanual Coordination and Musical Experience: The Role of Intrinsic Dynamics and Behavioral Information
Authors: Verheul Martine H.G. , Geuze Reint H.
Published: August 2016

Rhythmic interlimb coordination arises from the interaction of intrinsic dynamics and behavioral information, that is, intention, memory, or external information specifying the required coordination pattern. This study investigates the influence of the content of memorized behavioral information on coordination in musically experienced and inexperienced participants. These groups are hypothesized to have different intrinsic dynamics for this task. Stability was assessed in a switching task (variability and switching time). The in-phase, antiphase, and 90°-phase difference were specified in a neutral and an ecologically relevant manner. Musicians showed more stable coordination than nonmusicians did. No interaction effect was found with memorized behavioral information. Behavioral information showed an interaction effect with phase pattern on coordination variability, with the strongest effect for the 90°-phase pattern. Switching time was affected largely in line with the findings for coordination variability. Participants showed an intraindividual preference for one type of gallop and one type of switch strategy, suggesting different hand roles.
Evaluation of Scanning Methodology in Bimanual Coordination
Authors: Maslovat Dana , Bredin Shannon S.D. , Chua Romeo , Franks Ian M.
Published: August 2016

A major component of a dynamical paradigm involves a “scanning” procedure in an attempt to determine an individual’s intrinsic coordination tendencies before learning, as well as subsequent changes in the coordination landscape after practice. The purpose of the present study was to evaluate two methods of the scanning procedure. Scans were performed before and after 75 trials of a 90° bimanual-coordination pattern and were compared with early and late acquisition trials. Four groups of participants performed scanning and acquisition trials using a combination of either concurrent visual feedback in the form of Lissajous figures, paced by an auditory metronome, or visual metronomes in the form of flashing stimuli. Analyses revealed that all groups improved performance of the 90° pattern with practice. As predicted by the theory of practice specificity, scanning via the same method as acquisition appears to be valid. Scanning via Lissajous figures when the acquisition procedure was flashing squares was also found to be valid, but not the opposite condition. Reasons for this unidirectional transfer are given with these results suggesting that the sensitivity of a given scanning method might be influenced by the method of acquiring the coordination pattern.
Coordination of Reaching in Children with Spastic Hemiparetic Cerebral Palsy under Different Task Demands
Authors: Ricken Annieck X.C. , Bennett Simon J. , Savelsbergh Geert J.P.
Published: August 2016

Coordination of reaching with the impaired and non-impaired arm in 10 children with spastic hemiparetic cerebral palsy (SHCP) was examined in a stationary ball and moving ball context. Kinematic data on trunk, arm, and wrist movements, and coordination patterns between joint angles of elbow, shoulder, and trunk, were analyzed to determine how reaching was influenced by impairment and object motion. Results showed longer deceleration time and movement time and greater trunk contribution following decreased elbow and shoulder excursion when reaching with the impaired arm compared to the non-impaired arm. The coordination of joint angle pairs showed little linearity for the impaired arm, indicating more segmented movements of shoulder and elbow. It was also found that coordination patterns between elbow, shoulder, and trunk displayed less similarity when reaching with the impaired arm compared to the non-impaired arm in both stationary and moving ball conditions. Regardless of the timing constraints, children with SHCP could make successful interceptions using the impaired arm, indicating that they coordinated and controlled the degrees of freedom within their own functional possibilities.
Reliability and Validity of Physical Activity Questionnaires for Children: The Children’s Leisure Activities Study Survey (CLASS)
Authors: Telford Amanda , Salmon Jo , Jolley Damien , Crawford David
Published: August 2016

This study aimed to develop a reliable, valid, and feasible method for assessing physical activity among children ages 5–6 and 10–12 years. Test–retest reliability of a parental proxy questionnaire and a children’s self-report questionnaire was assessed in 280 children and parents. The criterion validity of the questionnaires was assessed using accelerometry. The proxy questionnaire provided a reliable measure of the type, frequency, and duration of children’s physical activity. Neither version of the questionnaire provided an accurate estimate of individual children’s physical activity. To assess the type, frequency, intensity, and duration of children’s activity, a combination of questionnaire and objective measures should be employed.
Relationships between Fundamental Movement Skills and Objectively Measured Physical Activity in Preschool Children
Authors: Cliff Dylan P. , Okely Anthony D. , Smith Leif M. , McKeen Kim
Published: August 2016

Gender differences in cross-sectional relationships between fundamental movement skill (FMS) subdomains (locomotor skills, object-control skills) and physical activity were examined in preschool children. Forty-six 3- to 5-year-olds (25 boys) had their FMS video assessed (Test of Gross Motor Development II) and their physical activity objectively monitored (Actigraph 7164 accelerometers). Among boys, object-control skills were associated with physical activity and explained 16.9% (p = .024) and 13.7% (p = .049) of the variance in percent of time in moderate-to-vigorous physical activity (MVPA) and total physical activity, respectively, after controlling for age, SES and z-BMI. Locomotor skills were inversely associated with physical activity among girls, and explained 19.2% (p = .023) of the variance in percent of time in MVPA after controlling for confounders. Gender and FMS subdomain may influence the relationship between FMS and physical activity in preschool children.