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Assessment via the Oculus of Visual “Weighting” and “Reweighting” in Young Adults

Anat V. Lubetzky, Daphna Harel, Helene Darmanin, and Ken Perlin

Substantial advances in virtual reality technology open an exciting window toward better understanding of subdomains of balance control. Here, we studied whether a portable virtual reality headset can be used to test sensory integration for balance. Twenty young adults stood on a both-sides-up ball or floor. Moving spheres were projected from an Oculus Development Kit 2 at various amplitudes and frequencies. Participants’ gains indicated visual “weighting” when standing on both-sides-up but not on the floor and “reweighting” with increased visual amplitude. Intraclass correlations showed acceptable to good reliability for all floor conditions and for some of the both-sides-up conditions when we repeated the protocol a week later. Future steps to further develop our paradigm into a clinical assessment of sensory integration for postural control are discussed.

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Delayed Compensatory Postural Adjustments After Lateral Perturbations Contribute to the Reduced Ability of Older Adults to Control Body Balance

Renato Claudino, Marcio José dos Santos, and Giovana Zarpellon Mazo

The goal of this study was to investigate the timing of compensatory postural adjustments in older adults during body perturbations in the mediolateral direction, circumstances that increase their risk of falls. The latencies of leg and trunk muscle activation to body perturbations at the shoulder level and variables of center of pressure excursion, which characterize postural stability, were analyzed in 40 older adults (nonfallers and fallers evenly split) and in 20 young participants. The older adults exhibited longer latencies of muscular activation in eight out of 15 postural muscles as compared with young participants; for three muscles, the latencies were longer for the older fallers than nonfallers. Simultaneously, the time for the center of pressure displacement reached its peak after the perturbation was significant longer in both groups of older adults. The observed delays in compensatory postural adjustments may affect the older adults’ ability to prompt control body balance after postural disturbances and predispose them to falls.

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Effects of a 10-Week Introductory Judo Course on Postural Control During a Bilateral Reactionary Gripping Task

Tyler W.D. Muddle, David H. Fukuda, Ran Wang, Joshua J. Riffe, David D. Church, Kyle S. Beyer, Jay R. Hoffman, and Jeffrey R. Stout

This study examined the effect of a 10-week introductory judo course on postural control during a bilateral reactionary gripping task using different stance conditions. A total of 20 volunteers were divided into experimental (JDO) and control (CON) groups. Countermovement jump was measured and center of pressure variables were evaluated while performing a bilateral reactionary gripping task under different stance conditions during pre- and posttesting. No interactions were observed for the center of pressure variables (p > .05), while both countermovement jump power (+165.4 W; p = .036) and height (+3.5 cm; p = .018) significantly improved in the JDO group following the 10-week course. Results indicate that 10 weeks of an introductory judo course has no effect on postural control while performing a bilateral reactionary gripping task using different stance conditions.

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Evaluation of Sex-Specific Movement Patterns in Judo Using Probabilistic Neural Networks

Bianca Miarka, Katarzyna Sterkowicz-Przybycien, and David H. Fukuda

The purpose of the present study was to create a probabilistic neural network to clarify the understanding of movement patterns in international judo competitions by gender. Analysis of 773 male and 638 female bouts was utilized to identify movements during the approach, gripping, attack (including biomechanical designations), groundwork, defense, and pause phases. Probabilistic neural network and chi-square (χ2) tests modeled and compared frequencies (p ≤ .05). Women (mean [interquartile range]: 9.9 [4; 14]) attacked more than men (7.0 [3; 10]) while attempting a greater number of arm/leg lever (women: 2.7 [1; 6]; men: 4.0 [0; 4]) and trunk/leg lever (women: 0.8 [0; 1]; men: 2.4 [0; 4]) techniques but fewer maximal length-moment arm techniques (women: 0.7 [0; 1]; men: 1.0 [0; 2]). Male athletes displayed one-handed gripping of the back and sleeve, whereas female athletes executed a greater number of groundwork techniques. An optimized probabilistic neural network model, using patterns from the gripping, attack, groundwork, and pause phases, produced an overall prediction accuracy of 76% for discrimination between men and women.

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Laterality of Motor Control and Induced Gamma-Band Activity During Voluntary Movement: A Clinical Perspective of an Inexpensive Paper-and-Pencil Bimanual Simultaneous Drawing Test

Iraj Derakhshan

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Volume 21 (2017): Issue 4 (Oct 2017)

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Spinal Cord Injury and Seated Postural Control: A Test of the Rambling and Trembling Hypothesis

Sunghoon Shin and Jacob J. Sosnoff

Rambling–trembling analysis separates the center of pressure into two components: the rambling component (RM: supraspinal) and trembling component (TM: muscle stiffness/reflex). We hypothesized that persons with spinal cord injury (SCI) would demonstrate decreased RM resulting from altered supraspinal processing and increased TM resulting from increased muscle stiffness. We also anticipated that the TM component would be greater in SCI patients with Harrington rods than in those without them. The seated postural control was assessed in 18 persons with SCI, comprising 12 with and six without Harrington rods, and 18 age-matched controls. The SCI group had greater center of pressure sway, RM, and TM components than the controls, with no difference in the postural sway between the SCI subgroups, suggesting that the impairment of seated postural control in individuals with SCI results from disturbed supraspinal and peripheral mechanisms, but that the control itself is unaffected by internal fixation with Harrington rods. These were not entirely consistent with our hypothesis.

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Vertical Finger Displacement Is Reduced in Index Finger Tapping During Repeated Bout Rate Enhancement

Mark Holten Mora-Jensen, Pascal Madeleine, and Ernst Albin Hansen

The present study analyzed (a) whether a recently reported phenomenon of repeated bout rate enhancement in finger tapping (i.e., a cumulating increase in freely chosen finger tapping frequency following submaximal muscle activation in the form of externally unloaded voluntary tapping) could be replicated and (b) the hypotheses that the faster tapping was accompanied by changed vertical displacement of the fingertip and changed peak force during tapping. Right-handed, healthy, and recreationally active individuals (n = 24) performed two 3-min index finger tapping bouts at freely chosen tapping frequency, separated by 10-min rest. The recently reported phenomenon of repeated bout rate enhancement was replicated. The faster tapping (8.8 ± 18.7 taps/min, corresponding to 6.0 ± 11.0%, p = .033) was accompanied by reduced vertical displacement (1.6 ± 2.9 mm, corresponding to 6.3 ± 14.9%, p = .012) of the fingertip. Concurrently, peak force was unchanged. The present study points at separate control mechanisms governing kinematics and kinetics during finger tapping.

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Visual Search Strategy During Regatta Starts in a Sailing Simulation

Aaron Manzanares, Ruperto Menayo, and Francisco Segado

In a sport conditioned by natural elements such as sailing, visual perception is a key factor for the performance. Research has shown that the visual behavior of athletes at different skill levels varies, which may cause differences in the performance achieved. The aim of this research was to examine the visual behavior of sailors from different ranking positions at the start of a race in a simulated situation. Twenty junior sailors (N = 10 top and N = 10 bottom ranking) participated in this study. The visual behavior was recorded at the start of a sailing simulation. The top-ranking sailors performed more visual fixations on the locations that have more highly relevant information, such as “telltales” and “rivals,” than do bottom-ranking sailors (p < .005). The top-ranking sailors are closer to the start line at the time of the start signal. The analysis of the visual search strategy shows that top-ranking sailors employed a more active visual search strategy. More experienced athletes can make better use of the information obtained from the important locations.

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Biological Movement and Laws of Physics

Mark L. Latash

Living systems may be defined as systems able to organize new, biology-specific, laws of physics and modify their parameters for specific tasks. Examples include the force-length muscle dependence mediated by the stretch reflex, and the control of movements with modification of the spatial referent coordinates for salient performance variables. Low-dimensional sets of referent coordinates at a task level are transformed to higher-dimensional sets at lower hierarchical levels in a way that ensures stability of performance. Stability of actions can be controlled independently of the actions (e.g., anticipatory synergy adjustments). Unintentional actions reflect relaxation processes leading to drifts of corresponding referent coordinates in the absence of changes in external load. Implications of this general framework for movement disorders, motor development, motor skill acquisition, and even philosophy are discussed.