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Motor Control

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https://www.readbyqxmd.com/read/28121286/precision-dependent-changes-in-motor-variability-during-sustained-bimanual-reaching
#1
Alessia Longo, Ruud Meulenbroek
Movement variability of the upper limb was investigated using a bimanual Fitts' task. Participants tapped rhythmically between target-pairs of different Index of Difficulties (ID) for three intervals of 20 min each. We studied the effects of ID and time-on-task on movement time, end-point variability, approximate entropy and standard deviation of relative phase. Lower ID and time-on-task caused decreasing movement time and increasing end-point variability. Moreover, standard deviation of relative phase and approximate entropy moderately increased...
January 25, 2017: Motor Control
https://www.readbyqxmd.com/read/28121283/effect-of-different-evasion-maneuvres-on-anticipation-and-visual-behavior-in-elite-rugby-league-players
#2
Jonathan D Connor, Robert G Crowther, Wade H Sinclair
This study examined the anticipation and visual behavior of elite Rugby League (RL) player's during two different evasion maneuvers (side- and split-step). Participants (N = 48) included elite RL players (n = 38) and controls (n = 10). Each participant watched videos consisting of side- and split-steps with anticipation of movement and eye behavior measured. No significant differences between the groups or evasion maneuver were found. The split-step was significantly harder to predict. Elite players appeared to spend more time viewing the torso and mid-region of the body compared to the controls...
January 25, 2017: Motor Control
https://www.readbyqxmd.com/read/28050918/unstable-footwear-affects-magnitude-and-structure-of-variability-in-postural-control
#3
Michael Buchecker, Stefan Wegenkittl, Thomas Stöggl, Erich Müller
This study evaluated the amount, and particularly the structure of variability in postural control accompanying an unstable shoe (US) application. Medio-lateral and anterior-posterior center of pressure (COP) signals, plus electromyographic (EMG) profiles of the tibialis anterior and gastrocnemius medialis were recorded in 29 asymptomatic men while wearing both US and flat shoes (FS). Statistical analysis included common measures of dispersion, as well as sample entropy (SEn) and largest Lyapunov exponent (LyE) estimates...
January 4, 2017: Motor Control
https://www.readbyqxmd.com/read/28001484/assessment-via-the-oculus-of-visual-weighting-and-re-weighting-in-young-adults
#4
Anat V Lubetzky, Daphna Harel, Helene Darmanin, Ken Perlin
Substantial advances in virtual reality (VR) technology open an exciting window towards better understanding of subdomains of balance control. Here we studied whether a portable VR headset can be used to test sensory integration for balance. Twenty young adults stood on a Both-Sides-Up (BOSU) 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 BOSU but not on the floor and 're-weighting' with increased visual amplitude...
December 21, 2016: Motor Control
https://www.readbyqxmd.com/read/28001481/vertical-finger-displacement-is-reduced-in-index-finger-tapping-during-repeated-bout-rate-enhancement
#5
Mark Holten Mora-Jensen, Pascal Madeleine, Ernst Albin Hansen
The present study tested 1) 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 form of externally unloaded voluntary tapping) could be replicated, and 2) the hypotheses that the faster tapping was accompanied by changed vertical displacement of the fingertip and by 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...
December 21, 2016: Motor Control
https://www.readbyqxmd.com/read/27111919/effects-of-treadmill-exercise-on-spontaneous-firing-activities-of-striatal-neurons-in-a-rat-model-of-parkinson-s-disease
#6
Kaixuan Shi, Xiaoli Liu, Decai Qiao, Lijuan Hou
Exercise improves motor deficits in Parkinson's disease (PD) patients but the underlying neuronal mechanism is poorly understood. Since the striatum is critical to motor function, we have investigated the potential effects of exercise on the spiking activity of the striatal neurons in a rat model of Parkinson's disease. Twenty-four hours after injection of 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle, rats in exercise groups were trained to exercise on a treadmill. Twenty-eight days after 6-OHDA lesion, apomorphine induced fewer rotations in the PD rats with exercise than in PD + Ex rats...
January 2017: Motor Control
https://www.readbyqxmd.com/read/27111857/adaptation-behavior-of-skilled-infant-bouncers-leg-movements-and-mechanisms-of-control
#7
Olinda Habib Perez, Coren Walters-Stewart, D G E Robertson, Natalie Baddour, Heidi Sveistrup
Rhythmic behavior in nonlinear systems can be described as limit cycles or attractors. System perturbations may result in shifts between multiple attractors. We investigated individual cycle-to-cycle leg movement kinematics of three prewalking skilled infant bouncers (10.6 ±0.91 months) during four different spring frequencies (0.9, 1.15, 1.27 and 1.56 Hz). A novel visual analysis phase-plane methodology was introduced to analyze the lower body joint kinematics. It was found that as infants' bounce frequency increased to match the natural frequency of the system, their joint ranges of motion decreased and lower extremity dynamics shifted from forced to simple harmonic motion...
2017: Motor Control
https://www.readbyqxmd.com/read/26730523/the-effect-of-load-uncertainty-and-foreperiod-regularity-on-anticipatory-and-compensatory-neuromotor-control-in-catching
#8
William P Berg, Michael R Hughes
Muscle activation was measured using EMG in 28 males (n = 28) while participants caught visually identical balls of known and unknown weights (50, 1.32, 2.18, and 2.99 kg) under variable (1-10s) and constant (3s) foreperiods. EMG integrals were computed for three time intervals before the catch (anticipatory), and one after (compensatory). Load uncertainty caused the CNS to use an anticipatory strategy characterized by preparation to catch balls of an unknown weight by utilizing about 92% of the muscle activation used to catch the heaviest possible ball under the known weight condition...
January 2017: Motor Control
https://www.readbyqxmd.com/read/26625469/prehension-combined-with-gait-in-individuals-with-chronic-low-back-pain
#9
Priscila Abbári Rossi Manciopi, Natalia Madalena Rinaldi, Renato Moraes
Low back pain (LBP) can affect performance in the combined task (CT) of gait and prehension, since it increases muscle activity amplitude during voluntary movements, impairs the anticipatory postural adjustments and reduces gait speed. We analyzed and compared the effect of adding the prehension movement toward a dowel located at three different heights (80, 100 and 120% of the lower limb length) on gait of individuals with and without LBP. The CT caused anticipatory adjustments, showing that gait changes started during the approach phase and continued on the step corresponding to grasping, especially for the lowest dowel height...
January 2017: Motor Control
https://www.readbyqxmd.com/read/26618330/joint-coordination-and-muscle-activities-of-ballet-dancers-during-tiptoe-standing
#10
Hiroko Tanabe, Keisuke Fujii, Motoki Kouzaki
We aimed to investigate joint coordination of lower limbs in dancers during tiptoe standing and the relationship between joint coordination and muscle coactivation. Seven female ballet dancers performed tiptoe standing with six leg positions (fi e classical dance positions and one modern dance position) for 10 s. The kinematic data of the metatarsophalangeal (MP), ankle, knee, and hip joints was collected, and surface electromyography (EMG) of over 13 lower limb muscles was conducted. Principal component analysis was performed to determine joint coordination...
January 2017: Motor Control
https://www.readbyqxmd.com/read/26595318/axial-segmental-coordination-during-turning-effects-of-stroke-and-attentional-loadings
#11
Haidzir Manaf, Maria Justine, Hui-Ting Goh
Attentional loadings deteriorate straight walking performance for individuals poststroke, but its effects on turning while walking remain to be determined. Here we compared turning kinematics under three attentional loading conditions (single, dual-motor, and dual-cognitive task) between stroke survivors and healthy controls. Nine chronic stroke survivors and 10 healthy controls performed the Timed Upand- Go test while their full-body kinematics were recorded. Onset times of yaw rotation of the head, thorax and pelvis segments and head anticipation distance were used to quantify turning coordination...
January 2017: Motor Control
https://www.readbyqxmd.com/read/26595105/effects-of-unilateral-muscle-fatigue-on-performance-and-force-coordination-in-bimanual-manipulation-tasks
#12
Daniel Feeney, Igor Jelaska, Mehmet Uygur, Slobodan Jaric
We examined the effects of unilateral muscle fatigue on the performance and coordination of grip (GF; normal component acting between the hand and object) and load force (LF; tangential component) in bimanual manipulation tasks, as well as the associated lateral differences. Eleven participants performed various symmetric bimanual tasks either without fatigue, or after fatiguing the GF producing muscles of either the nondominant or dominant hand. The GF/LF ratio of the fatigued and nonfatigued hand decreased and increased, respectively, while the neither the effects of fatigue on the task performance and GF-LF coordination, nor the lateral differences were revealed...
January 2017: Motor Control
https://www.readbyqxmd.com/read/27834583/spinal-cord-injury-and-seated-postural-control-a-test-of-the-rambling-and-trembling-hypothesis
#13
Sunghoon Shin, Jacob J Sosnoff
Rambling-trembling analysis separates the center of pressure (COP) 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 spinal cord injury (SCI), comprising of 12 with and 6 without Harrington rods, and 18 age-matched controls...
November 11, 2016: Motor Control
https://www.readbyqxmd.com/read/27768538/delayed-compensatory-postural-adjustments-after-lateral-perturbations-contribute-to-the-reduced-ability-of-older-adults-to-control-body-balance
#14
Marcio Jose Dos Santos, Renato Claudino, Giovana Zarpellon Mazzo
The goal of this study was to investigate the timing of compensatory postural adjustments (CPAs) 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 (COP) excursion, which characterize postural stability, were analyzed in 40 older adults (non-fallers and fallers evenly split) and in 20 young participants. The older adults exhibited longer latencies of muscular activation in 8 out of 15 postural muscles as compared to young participants; for three muscles, the latencies were longer for the older fallers than non-fallers...
October 21, 2016: Motor Control
https://www.readbyqxmd.com/read/27768535/visual-search-strategy-during-regatta-starts-in-a-sailing-simulation
#15
Aaron Manzanares, Ruperto Menayo, Francisco Segado
In a sport conditioned by natural elements such as sailing, visual perception is a key factor for the performance. The research has shown that the visual behaviour 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 behaviour 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 the study. The visual behaviour was recorded at the start of a sailing simulation...
October 21, 2016: Motor Control
https://www.readbyqxmd.com/read/27736312/evaluation-of-sex-specific-movement-patterns-in-judo-using-probabilistic-neural-networks
#16
Bianca Miarka, Katarzyna Sterkowicz-Przybycien, David H Fukuda
The purpose of the present study was to create a probabilistic neural network (PNN) 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. PNN and χ(2) tests modeled and compared frequencies (p≤0.05). 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...
October 13, 2016: Motor Control
https://www.readbyqxmd.com/read/27736310/effects-of-a-10-week-introductory-judo-course-on-postural-control-during-a-bilateral-reactionary-gripping-task
#17
Tyler W D Muddle, David H Fukuda, Ran Wang, Joshua J Riffe, David D Church, Kyle S Beyer, Jay R Hoffman, 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 varied stance conditions. Twenty volunteers were divided into experimental (JDO) or control (CON) groups. Countermovement jump (CMJ) was measured and center of pressure (COP) variables were evaluated while performing a bilateral reactionary gripping task under varied stance conditions during pre and post testing. No interactions were observed for the COP variables (p>0...
October 13, 2016: Motor Control
https://www.readbyqxmd.com/read/27736308/dynamic-fatigue-does-not-alter-soleus-h-reflexes-conditioned-by-homonymous-or-heteronymous-pathways
#18
Preeti D Oza, Shauna Dudley-Javoroski, Richard K Shields
H-reflex depression (diminution of amplitude after a conditioning stimulus) is mediated presynaptically and therefore can help distinguish central versus peripheral mechanisms of fatigue. We examined the effects of a dynamic exercise protocol on H-reflex depression using two conditioning methods: homonymous conditioning (paired-pulse tibial nerve stimulation); and heteronymous conditioning (common peroneal nerve stimulation). Ten subjects performed dynamic contractions of the soleus muscle through 30° ankle range of motion...
October 13, 2016: Motor Control
https://www.readbyqxmd.com/read/26595190/the-effect-of-blocked-random-and-mixed-practice-schedules-on-speech-motor-learning-of-tongue-twisters-in-unimpaired-speakers
#19
Kelly Jones, Karen Croot
There are few investigations comparing practice schedules in speech motor learning, despite certain schedules being recommended for the clinical treatment of speech motor disorders. This study compared effects of random, blocked and mixed practice on tongue twister accuracy in unimpaired speakers. We hypothesized that blocked practice would benefit acquisition of learning, but that random practice and mixed blocked-then-random practice would yield superior retention of learning. We found that the random and blocked-random practice schedules yielded superior accuracy at the end of the acquisition phase of learning and at a 1-week retention test...
October 2016: Motor Control
https://www.readbyqxmd.com/read/26491902/a-surrogate-technique-for-investigating-deterministic-dynamics-in-discrete-human-movement
#20
Paul G Taylor, Michael Small, Kwee-Yum Lee, Raul Landeo, Damien M O'Meara, Emma L Millett
Entropy is an effective tool for investigation of human movement variability. However, before applying entropy, it can be beneficial to employ analyses to confirm that observed data are not solely the result of stochastic processes. This can be achieved by contrasting observed data with that produced using surrogate methods. Unlike continuous movement, no appropriate method has been applied to discrete human movement. This article proposes a novel surrogate method for discrete movement data, outlining the processes for determining its critical values...
October 2016: Motor Control
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