bluuebunny/crossref_metadata_2025 huggingface dataset:
Undergraduate Preparedness and Partnerships to Enhance Diversity in Kinesiology
Authors: Gregory-Bass Rosalind Chonise , Williams Richard H. , Peters Bridget A. , Blount Asherah N.
Published: August 2016

Diversity and inclusion in Kinesiology is needed to ensure the future professionals of tomorrow engage in recognizing the shared fabric of science and inquiry. Initiatives targeting inclusion and diversity have shown promise in bridging the existing gap. Vital to this process is the role of faculty, administrators and students in providing academic support and paracurricular exposure to the field of Kinesiology. Historical perspectives and knowledge of best practices shape the conversation regarding innovative 21st century options deemed necessary for meeting this challenge. Our review describes programs that strengthen the preparedness of undergraduate students. In addition, we outline existing strategies leading to effective partnerships between undergraduate and graduate institutions. Diversity and inclusion are integral to the achievement of excellence and enhance each institution's ability to accomplish its academic mission and to serve its constituents.
Is Physical Fitness Associated With Health in Overweight and Obese Youth? A Systematic Review
Authors: Millard-Stafford Mindy , Becasen Jeffrey S. , Beets Michael W. , Nihiser Allison J. , Lee Sarah M. , Fulton Janet E.
Published: August 2016

A systematic review of literature was conducted to examine the association between changes in health-related fitness (e.g., aerobic capacity and muscular strength/endurance) and chronic disease risk factors in overweight and/or obese youth. Studies published from 2000–2010 were included if the physical activity intervention was a randomized controlled trial and reported changes in fitness and health outcomes by direction and significance (p< .05) of the effect. Aerobic capacity improved in 91% and muscular fitness improved in 82% of measures reported. Nearly all studies (32 of 33) reported improvement in at least one fitness test. Changes in outcomes related to adiposity, cardiovascular, musculoskeletal, metabolic, and mental/emotional health improved in 60%, 32%, 53%, 41%, and 33% of comparisons studied, respectively. In conclusion, overweight and obese youth can improve physical fitness across a variety of test measures. When fitness improves, beneficial health effects are observed in some, but not all chronic disease risk factors.
The Role of Mechanoreceptive Information in the Stability of Human Upright Posture: A Theoretical Consideration
Authors: Wu Ge , Zhao Weifeng
Published: August 2016

This study examined the role of feedback from cutaneous mechanoreceptors in the stability of human upright posture. A two-link, one degree of freedom, inverted pendulum model was constructed for the human body with ankle joint torque proportional to the delayed outputs from muscle receptors, joint receptors, and cutaneous mechanoreceptors in the foot. Theoretical analysis and numerical simulations indicated that the use of mechanoreceptive information reduced the frequency range and the maximum peak-peak value of the dynamic response of the system. However, without the use of muscle receptors, the mechanoreceptive feedback could not stabilize the system. In addition, body movement of human subjects was measured when their balanced upright posture was disturbed by a transient, forward/backward movement of a supporting platform. The loss of or change in cutaneous mechanoreceptive sense in their feet was induced by (a) having healthy subjects stand on a soft surface and (b) testing neuropathic patients with loss of vibratory sensation in their feet. The results showed significant increases in frequency range and maximum peak-peak value of ankle rotation and velocity for subjects standing on a soft (vs. hard) surface and for neuropathic patients (vs. age- and gender-matched healthy subjects).
Effects of Target Eccentricity on Temporal Costs of Point of Gaze and the Hand in Aiming
Authors: Helsen Werner F. , Starkes Janet L. , Buekers Martinus J.
Published: August 2016

This experiment addresses the coordination of point of gaze (PG) and hand movements in a speeded aiming task to predictable targets of three different eccentricities (35, 40, and 45 cm). In each condition subjects moved the eyes, head, trunk, and hand freely. Performance was assessed on 5 blocks of 5 trials. Analyses were conducted for (a) frequencies for initiation order of PG and the hand, (b) correlation between initiation latencies of PG and the hand, and (c) initiation, movement, and response times of PG and the hand. PG always arrived on target in advance of the hand and at approximately 50% of the response time of the hand (proportional time).Varying eccentricity increased initiation time of PG but not of the hand. With learning there was an initial temporal improvement and decreased variability of response within the first 10 trials, and with additional practice response times were further reduced. The importance of proportional time and its relationship to the first submovement in aiming are discussed.
A Coactivation Strategy in Anticipatory Postural Adjustments in Persons with Down Syndrome
Authors: Aruin Alexander S. , Almeida Gil L.
Published: August 2016

The hypothesis that persons with Down syndrome are likely to trade mechanical efficacy of motor patterns for safety was tested in a study of postural adjustments associated with fast voluntary movements. Control subjects and subjects with Down syndrome performed bilateral shoulder flexion and extension movements “as fast as possible” while standing on a force platform. Anticipatory changes in the background activity of postural muscles were seen in both groups of subjects. Subjects with Down syndrome demonstrated simultaneous EMG bursts in postural “agonist-antagonist” pairs. Subjects with Down syndrome also demonstrated patterns of deviations in the major postural joints, suggesting that they were using a different strategy which may be a correlate of “clumsiness.” It was concluded that practice in conditions of changing components of a motor task is the most promising way to encourage the central nervous system of persons with Down syndrome to search for alternative strategies and improve these individuals' ability to solve everyday motor problems.
Trajectory Formation and Development of the Control of Standing Up from Sitting
Authors: Scholz John P. , Brandt L. Courtenay
Published: August 2016

We tested the hypothesis that the movement trajectory of the center of mass (CM) and the horizontal trajectory of the head are the primary focus of the brain's control of the task of standing up from sitting to reach an object. Both infants and older children were studied. Stability was estimated by intertrial variability of actual CM, head, and wrist movement trajectories. They were compared to each other and indirectly to the stability of body segment motions via comparison to head or wrist motion variability estimated from body segment motion variability. The results suggest that standing up from a seat is organized primarily around controlling global task parameters: trajectories of the body CM and, during the postliftoff phase of the task, the head horizontal trajectory, rather than individual movement components. Infants at the earliest age of independent performance exhibited the major effects.
Reorganization of Catching Coordination under Varying Temporal Constraints
Authors: Mazyn Liesbeth I.N. , Montagne Gilles , Savelsbergh Geert J.P. , Lenoir Matthieu
Published: August 2016

In the present study, the limits of human catching behavior were challenged to investigate quantitative and qualitative adaptations of the catching movement when performing under varying ball speeds, implying minor as well as severe temporal constraints. Nine male participants caught balls approaching at speeds ranging from 8.5 to 19.7 m/s with their preferred hand. Although a decrease in catching performance was undeniable, several quantitative adaptations provided the catcher with extra time and allowed to compensate the decrease in spatial accuracy with increasing speed. More importantly, changes in the coordination between hand, elbow, and shoulder emerged with increasing movement velocity. More demanding temporal constraints lead to a shift from relatively independent activity of each joint towards a mode in which several joints act as one unit. This reorganization of the coordination pattern of the catch is discussed in the context of Bernstein’s degrees of freedom problem.
Load and Grip Force Coordination in Static Bimanual Manipulation Tasks in Multiple Sclerosis
Authors: Marwaha Rahul , Hall Susan J. , Knight Christopher A. , Jaric Slobodan
Published: August 2016

The aim of the study was to reveal specific aspects of impaired hand function in mildly affected multiple sclerosis (MS) patients. Static manipulation tasks were tested in 13 mildly impaired (EDSS 1.5-4) MS patients and 13 age and gender matched controls. The tasks were based either on presumably visually (i.e., feedback) controlled tracing of depicted patterns of load force (LF; produced by symmetric bimanual tension and/or compression applied against an externally fixed device) or on predominantly feed-forward controlled amplitudes of sinusoidal patterns of LF. The task variables (based on accuracy of exerting the required LF pattern) suggested poor performance of MS subjects in feedback, but not in the feed-forward controlled tasks. The patients also revealed higher GF/LF ratio in all tasks. However, the coordination of GF and LF appeared to be comparable in the two groups. These results continue to support the chosen experimental paradigm and suggest that in mildly affected MS patients, sensorimotor deficits and overgripping precede the decoupling of grip and load forces observed in more severely affected patients.
Force Coordination in Static Bimanual Manipulation: Effect of Handedness
Authors: Ferrand Leanna , Jaric Slobodan
Published: August 2016

The purpose of this study was to explore the effects of handedness on coordination of grip (G) and load (L) forces in static bimanual manipulation tasks. Participants (N = 10) exerted various L profiles against an externally fixed hand-held device based on presumably open-loop and closed-loop neural control mechanisms, (i.e., mediated and not mediated, respectively, by sensory feedback). Average G/L ratio and the coupling of G and L (i.e., stability of the G/L ratio and correlation between G and L) were separately assessed in each hand. The results revealed a lower average G/L ratio in the non-dominant hand suggesting a more economical grip, while the indices of G and L coupling were similar in two hands. The dominant and non-dominant hand failed to reveal relative advantages in the tasks predominantly based on open- and closed-loop control mechanisms, respectively. We conclude that, due to the static nature of the tested tasks, the particular advantage of the non-dominant hand in G and L coordination could be in line with the recently proposed specialization of the non-dominant limb for control of position. However, the overall results are not in line with classic views of the prevailing open- closed-loop neural mechanisms in the control of the dominant and nondominant limb, respectively.
The Beneficial Effects of a Functional Task Target on Reaching and Postural Balance in Patients with Right Cerebral Vascular Accidents
Authors: Chen Hsieh-ching , Lin Keh-chung , Chen Chia-ling , Wu Ching-yi
Published: August 2016

This study evaluated the effect of context on the reaching performance of the unaffected arm and postural control while standing in patients with right cerebral vascular accidents (RCVA) and in healthy adults. Fifteen subjects with RCVA and sixteen healthy subjects performed tasks with the right hand under two conditions while standing. One condition involved moving coins forward on a table as far as possible (concrete task) and the other reaching forward without a target (abstract task). Forward reaching distance, forward displacement and lateral shift of center of pressure (CoP), and weight distribution were the dependent variables. The RCVA and control groups achieved significantly greater reaching distances in the concrete task than in the abstract one. The RCVA group showed significantly less lateral shift of the CoP and placed more weight on the affected leg in the concrete than the abstract task, whereas the control group made a greater lateral shift in the concrete task and had a similar mean ratio of weight distribution during both tasks. The results demonstrate that a functional application of task targets may favorably modulate both reaching and posture performance and exert various positive affects on postural control. Such applications may have a place in the therapeutic recovery efforts for patients afflicted with stroke.
Gait Initiation in Multiple Sclerosis
Authors: Remelius Jebb G. , Hamill Joseph , Kent-Braun Jane , Van Emmerik Richard E.A.
Published: August 2016

Individuals with multiple sclerosis (MS) often have poor balance control that is especially apparent during dynamic tasks such as gait initiation (GI). The purpose of this study was to investigate how balance symptoms due to MS alter spatiotemporal variables, coordination, and temporal margins within the stability boundary during gait initiation. Twelve women with MS (Expanded Disability Status Scale [EDSS] mean = 4.0, SD = 1.4) and 12 women without MS (control group) initiated gait at their preferred speed. MS participants attained a slower anterior velocity because of smaller anterior center of mass displacements and took longer to complete the initiation of gait than the control group. MS participants exhibited a smaller posterior shift in center of pressure during GI and stepped with a longer dual support time than the control group. However, these changes may be due to differences in initiation velocity. Relative timing analysis showed invariance in postural and locomotor phases of gait initiation between groups. The MS group showed different coordination between anterior-posterior and medio-lateral center of pressure components while increasing temporal margins to the posterior and lateral stability boundaries in comparison with the control group. Overall, during gait initiation at their preferred speed the MS participants adopted a functional strategy that produces lower speed and reduced proximity to the stability boundaries prior to stepping.
Organization of Goal-Directed Action at a High Level of Motor Skill: The Case of Stone Knapping in India
Authors: Biryukova E.V. , Bril B.
Published: August 2016

We analyzed the relationship between goal achievement and execution variability in craftsmen who have acquired the highest “ultimate” skills of stone knapping. The goal of a knapping movement is defined as the vector of the final velocity of a hammer, crucial for detaching a flake and, consequently, for the shape of the final product. The execution of the movement is defined by the kinematic pattern of the arm (i.e., by the coordination between the joint angles corresponding to the seven arm degrees of freedom). The results show that (a) the direction of final velocity is very stable for all craftsmen, whereas the amount of kinetic energy transmitted to the stone was craftsman specific and (b) the kinematic pattern of the arm was strongly individual and was a reliable sign of the level of skill—the highest level was characterized by the highest flexibility of movement kinematics. We stress the importance of conducting the experiment in natural conditions for better understanding of the relationship among the purpose (the final shape of the stone), the goal, and the execution of the movement.
Visual Feedback Use during a Back Tuck Somersault: Evidence for Optimal Visual Feedback Utilization
Authors: Luis Marlene , Tremblay Luc
Published: August 2016

We aimed to determine if visual feedback use during aerial skills is more efficient at low angular head velocity (AHV; i.e., <350 deg/s) than at high AHV. Twelve experienced female acrobats performed 20 back tuck somersaults under four experimental conditions: full-vision (FV), vision at AHV below 350 deg/s (VBelow), vision at AHV above 350 deg/s (VAbove), and no-vision (NV). AHV was calculated in real time, and liquid crystal goggles were used to manipulate vision. Two gymnastics judges scored landing stability using a four-point scale. All vision conditions that allowed some vision yielded significantly better landing scores than in the NV condition. Furthermore, a nonparametric test revealed that VBelow yielded a better performance ranking than the FV condition. We conclude that visual feedback during a back tuck somersault is used for landing stability at all angular head velocities, but optimal feedback use occurs when there is retinal stability.
Movement Variability and Muscle Activity Relative to Center of Pressure during Unipedal Stance on Solid and Compliant Surfaces
Authors: Croft James L. , von Tscharner Vinzenz , Zernicke Ronald F.
Published: August 2016

Compliant surfaces are used to challenge postural stability, but assessments are frequently limited to summary measures of center of pressure that do not provide insights into the temporal dynamics of motor coordination. Here, we measured center-of-pressure changes on three surfaces (solid, foam, and air-filled disc) and quantified the relative timing of changes in joint angles and muscle activity with respect to center-of-pressure changes. Nine active male subjects (20–30 years old) performed ten 30-s trials of unipedal stance on each of the three surfaces. Sway range, mean sway, mean sway velocity, path length, and fitted ellipse area increased, monotonically, from solid surface to foam to air-filled disc. The number of significant cross-correlations was greater for the compliant surfaces compared with the solid surface. Muscle activity preceded changes in center-of-pressure displacement, with the type of surface affecting the magnitude of the lead in the mediolateral direction. Center of pressure was more constrained on less stable surfaces and in the mediolateral direction.
Task Constraints on Affordance Boundaries
Authors: Lopresti-Goodman Stacy M. , Richardson Michael J. , Baron Reuben M. , Carello Claudia , Marsh Kerry L.
Published: August 2016

The actualization of a simple affordance task—grasping and moving wooden planks of different sizes using either one or two hands—was assessed in the context of taskrelevant (plank sequence, plank presentation speed) and task-irrelevant (cognitive load) manipulations. In Experiment 1, fast (3 s/plank) and self-paced (≈5 s/plank) presentation speeds revealed hysteresis; the transition point for ascending series was greater than the transition point for descending series. Hysteresis was eliminated in the slowest presentation speed (10 s/plank). In Experiment 2, hysteresis was exaggerated by a cognitive load (counting backward by seven) for both fast and slow presentation speeds. These results suggest that behavioral responses to the attractor dynamics of perceived affordances are processes that require minimal cognitive resources.
The Development of the Fastest Isometric Grip Force Changes and Clinical Relevance
Authors: Blank Rainer , Hermsdörfer Joachim
Published: August 2016

Fast force changes with hand-held objects are an important prerequisite for object manipulation in everyday life. This study examines the development of fastest isometric force changes in a precision grip. One hundred sixty-five children (76 girls, 89 boys), 3–14 years, without neurological abnormalities increased and decreased repetitively isometric grip forces as rapidly as possible by their dominant hand using a small cylindrical pinch grip object (20 g). The frequency of repetitive force changes increased in a linear way from the age of 4 years until about 12 years by 0.23 Hz per year (r2 = .54) without noticeable gender difference. The ratio of the duration of force increase and decrease slightly declined from 1.05 (4-year-olds) to 0.95 (11- to 14-year-olds). The development of force amplitudes and the mean force were more variable. Temporal parameters become less variable with age, whereas force parameters become more variable. In particular, the temporal parameters of fastest isometric force changes are best predictors for developmental changes. Fastest isometric force changes may be an important basic capacity for fast object manipulation, particularly in young children and in children with movement disorders.
Effects of Stick Use on Bimanual Coordination Performance during Rapid Alternate Tapping in Drummers
Authors: Fujii Shinya , Oda Shingo
Published: August 2016

The aim of this study is to establish the effects of stick use on rhythmic bimanual coordination in drummers. Eighteen drummers performed a rapid antiphase coordination task using their fingers and handheld drumsticks. We found no significant differences in the speed of tapping between finger and stick-use tapping, while stick-use tapping had a larger peak force and smaller variability in coordination pattern than finger tapping. As a consequence, the quotient of the number of taps divided by the variability of coordination pattern, named the bimanual performance quotient, was higher for stick-use tapping than for finger tapping. A significant correlation was found between years of drumming experience and the bimanual performance quotient for both finger and stick-use tapping, but not between the years of drumming experience and the degree of improvement in the bimanual performance quotient with stick use relative to finger tapping. These results indicate that stick use enhances drummers’ bimanual coordination during rapid alternate tapping, whereas the degree of improvement with stick use does not depend on drumming experience.
Brief Electrical Stimulation Accelerates Axon Regeneration in the Peripheral Nervous System and Promotes Sensory Axon Regeneration in the Central Nervous System
Authors: Gordon Tessa , Udina Esther , Verge Valerie M.K. , de Chaves Elena I. Posse
Published: August 2016

Injured peripheral but not central nerves regenerate their axons but functional recovery is often poor. We demonstrate that prolonged periods of axon separation from targets and Schwann cell denervation eliminate regenerative capacity in the peripheral nervous system (PNS). A substantial delay of 4 weeks for all regenerating axons to cross a site of repair of sectioned nerve contributes to the long period of separation. Findings that 1h 20Hz bipolar electrical stimulation accelerates axon outgrowth across the repair site and the downstream reinnervation of denervated muscles in rats and human patients, provides a new and exciting method to improve functional recovery after nerve injuries. Drugs that elevate neuronal cAMP and activate PKA promote axon outgrowth in vivo and in vitro, mimicking the electrical stimulation effect. Rapid expression of neurotrophic factors and their receptors and then of growth associated proteins thereafter via cAMP, is the likely mechanism by which electrical stimulation accelerates axon outgrowth from the site of injury in both peripheral and central nervous systems.
Visual Feedback of Force Platform Displacements for Balance Control Training: What Postural Ability Do Healthy Subjects Have To Develop To Decrease the Difference Between Center of Pressure and Center of Gravity Movements?
Authors: Rougier Patrice R. , Boudrahem Samir
Published: August 2016

Past studies have emphasized the beneficial effect of additional visual feedback (VFB) on the capacity of healthy adults to decrease the amplitudes of the center-of-pressure minus center-of-gravity (CP-CGv) movements. To better assess these capacities, 56 subjects were asked to stand still on a force platform and to use the visual information provided. Dependency coefficients, based on their capacity to lower their CP-CGv movements and therefore relax their lower limb muscles, as well as parameters aimed at characterizing their postural strategies were measured across VFB conditions including (1) CP displacements in real time (VFBCP0), (2) CP displacements with a 600-ms delay (VFBCP600), and (3) CP-CGv displacements with a 600-ms delay (VFBCP-CG600). A non-VFB condition (eyes open) was also included. Several linear correlations were used to specify the relation between subjects’ capacity to relax, compared with the VFBCP0 condition, across the three remaining conditions. The data highlight the complementary nature of the VFB conditions and establish the postural control behaviors necessary to use these VFB protocols efficiently.
The Effects of Physical Activity in the Anticipatory Postural Adjustments in Elderly People
Authors: Carvalho Raquel , Vasconcelos Olga , Gonçalves Pedro , Conceição Filipe , Vilas-Boas João Paulo
Published: August 2016

Exercise seems to attenuate the postural control system and anticipatory postural adjustments (APAs) decline, but no conclusive findings are available. This study analyses, in elderly people, the exercise effect in APAs during the raising of a load with both arms in the sagittal plane. Twenty eight males over the age of 60 (65,8 ± 4,07 yr old)—9 veterans in exercising, 9 who exercise recently, and 10 sedentary—were asked to raise a load with both arms simultaneously to shoulder level, in standing position, as fast as possible. It was studied the electromyography (EMG) pattern of the main muscles. The APAs were quantified through the time integral of EMG records (iEMG). Anticipatory changes in the postural muscles were seen in all groups. We observed, in the tibialis anterior activity, a higher significant activation in the sedentary compared with the other groups, suggesting that exercise can modulate the postural control system.
Shaping by Stiffening: A Modeling Study for Lips
Authors: Nazari Mohammad A. , Perrier Pascal , Chabanas Matthieu , Payan Yohan
Published: August 2016

On the basis of simulations carried out with a finite element biomechanical model of the face, the influence of the muscle stress stiffening effect was studied for the protrusion/rounding of the lips produced with the Orbicularis Oris (OO). It is shown that the stress stiffening effect influences lip shape. When stress stiffening is modeled, the variation in the crucial geometrical characteristics of the lips shows a clear saturation effect as the OO activation level increases. Similarly, for a sufficient amount of OO activation, a saturation effect is observed when stiffening increases. In both cases, differences in lip shaping associated with the absence or presence of stiffening have consequences for the spectral characteristics of the speech signal obtained for the French vowel /u/. These results are interpreted in terms of their consequences for the motor control strategies underlying the protrusion/rounding gesture in speech production.
Effects of Aging on Control of Timing and Force of Finger Tapping
Authors: Sasaki Hirokazu , Masumoto Junya , Inui Nobuyuki
Published: August 2016

The present study examined whether the elderly produced a hastened or delayed tap with a negative or positive constant intertap interval error more frequently in self-paced tapping than in the stimulus-synchronized tapping for the 2 N target force at 2 or 4 Hz frequency. The analysis showed that, at both frequencies, the percentage of the delayed tap was larger in the self-paced tapping than in the stimulus-synchronized tapping, whereas the hastened tap showed the opposite result. At the 4 Hz frequency, all age groups had more variable intertap intervals during the self-paced tapping than during the stimulus-synchronized tapping, and the variability of the intertap intervals increased with age. Thus, although the increase in the frequency of delayed taps and variable intertap intervals in the self-paced tapping perhaps resulted from a dysfunction of movement timing in the basal ganglia with age, the decline in timing accuracy was somewhat improved by an auditory cue. The force variability of tapping at 4 Hz further increased with age, indicating an effect of aging on the control of force.
The Reliance on Visual Feedback for Online and Offline Processing
Authors: Lawrence Gavin P. , Khan Michael A. , Mourton Stuart , Bernier Pierre-Michel
Published: August 2016

The objective of the current study was to determine whether the reliance on visual feedback that develops with practice is to due utilizing vision to adjust trajectories during movement execution (i.e., online) and/or to enhance the programming of subsequent trials (i.e., offline). Participants performed a directional aiming task with either vision during the movement, dynamic feedback of the trajectory of the movement or the movement endpoint. The full vision condition was more accurate during practice than the other feedback conditions but suffered a greater decrement in performance when feedback was removed. In addition, the reliance on trajectory feedback was greater compared with the endpoint feedback. It appears that the reliance on visual feedback that develops with practice was due to both online and offline processing.
From the W-Method to the Canonical-Dissipative Method for Studying Uni-Manual Rhythmic Behavior
Authors: Dotov Dobromir G. , Frank Till D.
Published: August 2016

A novel method for the analysis of repetitive limb behavior oscillation is presented. It is based on a model used to account for self-sustained limit cycles that involve energy pumping compensating for dissipative processes. The experiment involved a uni-manual pendulum swinging task paced at five frequencies. The median frequency corresponded to the resonant one for the chosen pendulum and hand parameters. We applied the model-based analysis to explore the relationship between behavioral observables and model parameters not available from previous methods. Oscillation amplitude and energy, and motor variability were the behavioral observables we focused on while energy pumping, attractor strength, and noise amplitude were the model parameters. As expected, energy pumping was found to increase with pacing frequency. Noise amplitude did not change and stability decreased.
The Relationship Between Attention and Gait in Aging: Facts and Fallacies
Authors: Holtzer Roee , Wang Cuiling , Verghese Joe
Published: August 2016

The current study critically assessed the relationship between cognitive functions and gait in nondemented older adults. Quantitative measures of gait (velocity, cadence, and a coefficient of variance in stride length) were assessed in single and dual-task conditions. Three cognitive factors captured the domains of Executive Attention, Verbal IQ, and Memory. Linear regressions showed that Executive Attention was related to velocity in both walking conditions. However, Memory and Verbal IQ were also related to velocity. Memory was related to Cadence in both walking conditions. Executive Attention was related to the coefficient of variance in stride length in both walking conditions. Linear mixed effects models showed that dual-task costs were largest in velocity followed by cadence and the coefficient of variance in stride length. The relationship between cognitive functions and gait depends, in part, on the analytic approach used, gait parameters assessed, and walking condition.
Handwriting: Three-Dimensional Kinetic Synergies in Circle Drawing Movements
Authors: Hooke Alexander W. , Karol Sohit , Park Jaebum , Kim Yoon Hyuk , Shim Jae Kun
Published: August 2016

The purpose of this study was to investigate central nervous system (CNS) strategies for controlling multifinger forces during a circle-drawing task. Subjects drew 30 concentric, discontinuous clockwise and counter clockwise circles, at self and experimenter-set paces. The three-dimensional trajectory of the pen’s center of mass and the three-dimensional forces and moments of force at each contact between the hand and the pen were recorded. Uncontrolled Manifold Analysis was used to quantify the synergies between pen-hand contact forces in radial, tangential and vertical directions. Results showed that synergies in the radial and tangential components were significantly stronger than in the vertical component. Synergies in the clockwise direction were significantly stronger than the counterclockwise direction in the radial and vertical components. Pace was found to be insignificant under any condition.
Proactive Action Preparation: Seeing Action Preparation as a Continuous and Proactive Process
Authors: Pezzulo Giovanni , Ognibene Dimitri
Published: August 2016

In this paper, we aim to elucidate the processes that occur during action preparation from both a conceptual and a computational point of view. We first introduce the traditional, serial model of goal-directed action and discuss from a computational viewpoint its subprocesses occurring during the two phases of covert action preparation and overt motor control. Then, we discuss recent evidence indicating that these subprocesses are highly intertwined at representational and neural levels, which undermines the validity of the serial model and points instead to a parallel model of action specification and selection. Within the parallel view, we analyze the case of delayed choice, arguing that action preparation can be proactive, and preparatory processes can take place even before decisions are made. Specifically, we discuss how prior knowledge and prospective abilities can be used to maximize utility even before deciding what to do. To support our view, we present a computational implementation of (an approximated version of) proactive action preparation, showing its advantages in a simulated tennis-like scenario.
Effect of Aging on Coordinated Eye and Hand Movements With Two-Segment Sequence
Authors: Rand Miya K. , Stelmach George E.
Published: August 2016

This study examined how aging compromises coordinative eye-hand movements with multiple segments. Older adults and young controls performed two-segment movements with the eyes only or with the eyes and hand together. The results showed minimal age-related changes on the initiation and execution of primary saccade during the first segment. However, the older adults showed a scaling problem of saccade velocity when hand movements were included. They were also slow in stabilizing gaze fixation to the first target. Regarding hand movements, the older adults pronouncedly increased the deceleration phase compared with the controls while fixating their gazes to the target. They also increased the intersegment interval for both eye and hand movements. Taken together, aging differentially affects various components of movements, which contributes to the slowness of overall performance.
Postural Adjustments in Catching: On the Interplay Between Segment Stabilization and Equilibrium Control
Authors: Tijtgat Pieter , Vanrenterghem Jos , Bennett Simon J. , De Clercq Dirk , Savelsbergh Geert J.P. , Lenoir Matthieu
Published: August 2016

The purpose of this study was to investigate postural adjustments in one-handed ball catching. Specifically, the functional role of anticipatory postural adjustments (APA) during the initial arm raising and subsequent postural adjustments (SPA) for equilibrium control and ball-hand impact were scrutinized. Full-body kinematics and kinetics allowed an analysis of the mechanical consequences of raising up the arm and preparing for ball-hand impact. APA for catching were suggested to be for segment stabilization. SPA had a functional role for equilibrium control by an inverted pendulum mechanism but were also involved in preparing for the impact of the ball on the hand, which was illustrated by an increased postural response at the end of the movement. These results were compared with raising up the arm in a well-studied reaction-time task, for which an additional counter rotation equilibrium mechanism was observed. Together, our findings demonstrate that postural adjustments should be investigated in relation to their specific functional task constraints, rather than generalizing the functional role of these postural adjustments over different tasks.
Integration of Alternating Monocular Samples During Goal-Directed Aiming
Authors: Hansen Steve , Hayes Spencer J. , Bennett Simon J.
Published: August 2016

The current study examined the effect of interocular delay in a manual aiming task that required accurate end-point placement, but not precise control of a grip aperture. Participants aimed in binocular, monocular, or alternating monocular vision conditions. For the latter, 25ms monocular samples were provided to alternate eyes without delay (0ms), or a delay of 25 or 50ms. The interocular delay resulted in a longer movement time, caused by a longer time-to-peak and time-after-peak velocity, and a reduction in peak velocity. We suggest that the change in kinematics reflect a strategic response to preserve terminal aiming accuracy and variability when faced with an informational perturbation. These findings indicate that the response to the interocular delay between alternating monocular samples depends on the task-specific information used to control that behavior.
Hypohydration Does Not Alter Standing Balance
Authors: Seay Joseph F. , Ely Brett R. , Kenefick Robert W. , Sauer Shane G. , Cheuvront Samuel N.
Published: August 2016

We examined the effect of body water deficits on standing balance and sought to determine if plasma hyperosmolality (Posm) and/or volume reduction (%ΔVplasma) exerted independent effects. Nine healthy volunteers completed three experimental trials which consisted of a euhydration (EUH) balance test, a water deficit session and a hypohydration (HYP) balance test. Hypohydration was achieved both by exercise-heat stress to 3% and 5% body mass loss (BML), and by a diuretic to 3% BML. Standing balance was assessed during quiet standing on a force platform with eyes open and closed. With eyes closed, hypohydration significantly decreased medial-lateral sway path and velocity by 13% (both p < .040). However, 95% confidence intervals for the mean difference between EUH and HYP were all within the coefficient of variation of EUH measures, indicating limited practical importance. Neither Vplasma loss nor Posm increases were associated with changes in balance. We concluded that standing balance was not altered by hypohydration.
Analysis of Increasing and Decreasing Isometric Finger Force Generation and the Possible Role of the Corticospinal System in This Process
Authors: Li Sheng
Published: August 2016

This study investigated the possible role of the corticospinal system during force generation and force relaxation. Nine young and healthy subjects were instructed to produce a total force with four fingers within a hand following a preset force generation and relaxation ramp template closely. Excitability of corticospinal (CS) projections was assessed by single- and paired-pulse TMS. Errors introduced by a finger force were partially compensated by other finger forces during force generation, but were amplified during force relaxation. The CS excitability was greater during force generation than maintenance or relaxation. No difference in intracortical inhibition or facilitation was found. Nonnormalized finger extensor EMG responses remained unchanged. The findings suggest that force relaxation is not just a withdrawal from activation, and multifinger interactions are likely controlled beyond the primary motor cortex.
The Power of Now: Brief Mindfulness Induction Led to Increased Randomness of Clicking Sequence
Authors: Kee Ying Hwa , Chaturvedi Iti , Wang Chee Keng John , Chen Lung Hung
Published: August 2016

The capacity for random movement production is known to be limited in humans (e.g., Newell, Deutsch, & Morrison, 2000). We examined the effects of a brief mindfulness induction on random movement production because there are useful implications for variability in solving movement-related problems. The main task involved randomly clicking the 9 boxes in a 3 × 3 grid presented on a computer screen for five minutes. We characterized the sequence of clicking in terms of degrees of randomness, or periodicity, based on the fit, or probability, of the experimental data with its best fitting Bayesian network (4-click memory nodes) using the Markov chain Monte Carlo (MCMC) approach. Sixty-three participants were randomly assigned to either the experimental or the control condition. Mixed design repeated-measures ANOVA results show that the short mindfulness induction had a positive effect on the randomness of the sequence subsequently produced. This finding suggests that mindfulness may be a suitable strategy for increasing random movement behavior.
Circular Components in Center of Pressure Signals
Authors: Agostini Valentina , Chiaramello Emma , Knaflitz Marco
Published: August 2016

Static posturography provides an objective assessment of postural control by characterizing the body sway during upright standing. The center of pressure (COP) signal is recorded by a force platform, and it is analyzed by means of many different models and techniques. Most of the parameters calculated according to these different approaches are affected by relevant intra- and intersubject variability or do not have a clear physiological interpretation. Traditional approaches decompose the COP signal into anteroposterior and mediolateral time series, corresponding to ankle plantar/dorsiflexion and hip adduction/abduction, respectively. In this study we hypothesized that COP signals show inherent rotational characteristics. To verify our hypothesis we applied the rotary spectra analysis to the two-dimensional COP signal to decompose it into clockwise and counterclockwise rotational components. We demonstrated the presence of rotational components in the COP signal of healthy subjects, providing a reference data set of the spectral characteristics of these components.
Recent Tests of the Equilibrium-Point Hypothesis (λ Model)
Authors: Feldman Anatol G. , Ostry David J. , Levin Mindy F. , Gribble Paul L. , Mitnitski Arnold B.
Published: August 2016

The λ model of the equihbrium-point hypothesis (Feldman & Levin, 1995) is an approach to motor control which, like physics, is based on a logical system coordinating empirical data. The model has gone through an interesting period. On one hand, several nontrivial predictions of the model have been successfully verified in recent studies. In addition, the explanatory and predictive capacity of the model has been enhanced by its extension to multimuscle and multijoint systems. On the other hand, claims have recently appeared suggesting that the model should be abandoned. The present paper focuses on these claims and concludes that they are unfounded. Much of the experimental data that have been used to reject the model are actually consistent with it.
Intrinsic Muscle Properties Facilitate Locomotor Control—A Computer Simulation Study
Authors: Gerritsen Karin G.M. , van den Bogert Anton J. , Hulliger Manuel , Zernicke Ronald F.
Published: August 2016

The purpose of this study was to investigate, theoretically, to what extent muscle properties could contribute to recovery from perturbations during locomotion. Four models with different actuator properties were created: the FLVT model, which encompassed force-length (FL) and force-velocity (FV) characteristics of human muscles as well as muscle stimulation inputs as functions of time (T); the FLT model, which had muscles without force-velocity characteristics; the FVT model, which had muscles without specific force-length characteristics; and the MT model, which had no muscles but was driven by joint moments (M) as a function of time. Each model was exposed to static and dynamic perturbations and its response was examined. FLVT showed good resistance to both static and dynamic perturbations. FLT was resistant to static perturbation but could not counteract dynamic perturbation, whereas the opposite was found for FVT. MT could not counteract either of the perturbations. Based on the results of the simulations, skeletal muscle force-length-velocity properties, although interactively complex, contribute substantially to the dynamic stability of the musculoskeletal system.
The Stretch Reflex and H-Reflex of the Human Suleus Muscle during Walking
Authors: Andersen Jacob Buus , Sinkjaer Thomas
Published: August 2016

Due to the complexity of applying a well-defined stretch during human walking, most of our knowledge about the short latency stretch reflex modulation in humans is based on H-reflex studies. To illuminate the difference between the two methodologies, both types of reflexes were evoked in the same subjects, same experiment. Stretch reflexes were evoked via a stretch device capable of evoking stretch reflexes of the human soleus muscle during walking. H-reflexes were elicited by an electrical stimulation of the tibial nerve at the popliteal fossa at the knee. A significantly different modulation of the two reflexes was found in the late stance where the stretch reflex decreased in relation to the H-reflex. This was consistent with an unloading of the muscle spindles during the push-off in late stance, suggesting a complex alpha-gamma coactivation, if any, at this time of the step. The soleus stretch reflex and H-reflex were compared during the stance phase of walking and sitting at matched soleus EMG activity. No difference was found in the amplitude of the stretch reflex. However, there was a significant decrease of the H-reflex during the stance phase of walking, consistent with a task-specific presynaptic mediated reflex control. It is proposed that the short latency stretch reflex during walking is not sensitive to such a presynaptic inhibition.
How Locomotor Parameters Adapt to Gravity and Body Structure Changes during Gait Development in Children
Authors: Brenière Yvon
Published: August 2016

The principles of direct dynamics and oscillating systems have been used to study the development of gait parameters in children, with respect to their kinetic consequences on the oscillations of body center of mass (CM). In particular the equations established (a) a natural body frequency (NBF), a body parameter specific to oscillating movements which is invariant for adults and decreases with age for children, and (b) the amplitude ratio of CM to center-of-foot pressure (CP) oscillations as a parametric function of the step frequency, whose parameter is the NBF. This function was used to analyze the development of gait locomotors with respect to their kinetic effects on balance in the frontal plane. Five children were examined longitudinally during their first 5 years of independent walking (IW), and two cross-sectional groups between 5 and 7 years of IW were also considered. The results showed a shift toward the low end of step frequency bands as the NBF decreased along with in variances in the amplitudes of CM oscillation in both the frontal and sagittal planes, regardless of age and gait velocity. The biomechanical meaning of the NBF, of its decrease and of postural invariances associated with the decrease of the frequency, are discussed as well how the programming of locomotor parameters adapts to changes in body structure during gait development.