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J. Greg Anson, Brian l. Hyland, Rolf Kötter and Jeffery R. Wickens

A movement task was used to investigate the effects of precued variables on reaction time. The task involved rapid rotation of a hand-held manipulandum to target locations and required either pronation or supination of the forearm through short or long extent. The effects on reaction time of precues signalling target direction, extent, or a combination of direction and extent, were measured. The longest reaction times occurred when no information about direction or extent was provided in the precue (all parameters uncertain). Complete prior specification of target position produced the shortest reaction times. Specification of direction when extent was uncertain produced a significantly larger reduction in reaction time than specification of extent when direction was uncertain. Prior specification of extent also produced a small but significant reduction in reaction time relative to the condition in which direction and extent were specified in a mutually conditional manner. The results are discussed in relation to parameter precuing and motor programming, in which the direction is programmed by the pre-selection of neurons representing the muscles to be used in the task while programming of extent is represented by their level of activity during task performance.

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Hatice Mujde Ayık and Michael J. Griffin

magnitude, the frequency, the direction, and the duration of the oscillations combine to cause loss of balance. In trains, buses, aircraft, buildings, and so on, the motions causing instability are often transient, so it is desirable to understand whether instability can be predicted from a peak measure of

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Atsushi Makimoto, Yoko Sano, Satoru Hashizume, Akihiko Murai, Yoshiyuki Kobayashi, Hiroshi Takemura and Hiroaki Hobara

75 Hz for GRFs 12 and 10 Hz for marker trajectories. 13 According to a previous study, 14 the timing of foot-ground contacts was determined using a threshold greater than 16 N of vertical GRF. The GRF variables analyzed were the peak vertical forces, peak braking (posterior direction

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Antonio C.S. Guimaraes and James G. Hay

The purpose of this study was to identify the mechanical characteristics of the hands-between-the-feet grab starting technique which contribute to a faster start. Twenty-four high school swimmers performed four trials of a grab start followed by a glide to a distance of 9 m. The results suggested that to obtain a faster start, swimmers should (a) move the center of mass fast in the forward direction while the feet are in contact with the starting block, (b) maximize the force exerted through the feet in the backward direction, and (c) maximize the force exerted through the hands against the starting block in the forward and upward direction.

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Javier Yanci, Daniel Castillo, Aitor Iturricastillo, Tomás Urbán and Raúl Reina

high international repercussion, footballers with CP deserve special attention. Most research has investigated the physical characteristics of footballers with CP, such as cardiovascular capacity, running economy, 4 changes of direction (CODs) ability, 5 jump capacity, muscle strength, and anaerobic

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Uta Sailer, Florian Güldenpfennig and Thomas Eggert

This study investigated the effect of hand movements on behavioral and electro-physiological parameters of saccade preparation. While event-related potentials were recorded in 17 subjects, they performed saccades to a visual target either together with a hand movement in the same direction, a hand movement in the opposite direction, a hand movement to a third, independent direction, or without any accompanying hand movements. Saccade latencies increased with any kind of accompanying hand movement. Both saccade and manual latencies were largest when both movements aimed at opposite directions. In contrast, saccade-related potentials indicating preparatory activity were mainly affected by hand movements in the same direction. The data suggest that concomitant hand movements interfere with saccade preparation, particularly when the two movements involve motor preparations that access the same visual stimulus. This indicates that saccade preparation is continually informed about hand movement preparation.

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Florian Loffing and Norbert Hagemann

When anticipating future events like an opponent’s stroke direction in tennis, players are assumed to rely on both kinematic and contextual cues such as an opponent’s on-court position. However, knowledge of position dependency in shot-direction probabilities and experimental evidence of the effect of on-court position on action-outcome anticipation is missing. Here we show that shot-direction probabilities vary as a function of a hitting player’s on-court position in professional tennis. Moreover, unlike novices, skilled players in particular relied on information about an opponent’s position when anticipating forehand baseline shot direction in a video-based experiment. The position dependency in skilled players’ prediction behavior was most evident when little information on an opponent’s stroke kinematics was available. Findings suggest that skilled players consider the reliability of different information sources by weighting the available contextual and kinematic cues differently in the course of an opponent’s unfolding action.

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Roya Khanmohammadi, Saeed Talebian, Mohammad Reza Hadian, Gholamreza Olyaei and Hossein Bagheri

The purpose of study was to demonstrate age-related changes during gait initiation (GI). Therefore, displacement, velocity, total power, mean and median frequency of COP trajectories were measured during phases of GI in anteroposterior (AP) and mediolateral (ML) directions. The older group demonstrated the slower and lesser displacement in comparison with the younger group during anticipatory phase in AP direction and during locomotor phase in AP and ML directions. In addition, the median and mean frequency were greater in the older relative to the younger group during anticipatory phase in AP direction, while these were lesser in older than younger group during locomotor phase in AP and ML directions. Moreover, total power was greater among older than younger adults during the anticipatory phase in ML direction and during all phases in AP direction. This study suggests that COP-related parameters extracted from time and frequency domains have the ability to demonstrate age-related changes.

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Wim H. van Lier, John van der Kamp and Geert J.P. Savelsbergh

We assessed how golfers cope with the commonly observed systematic overshoot errors in the perception of the direction between the ball and the hole. Experiments 1 and 2, in which participants were required to rotate a pointer such that it pointed to the center of the hole, showed that errors in perceived direction (in degrees of deviation from the perfect aiming line) are destroyed when the head is constrained to move within a plane perpendicular to the green. Experiment 3 compared the errors in perceived direction and putting errors of novice and skilled players. Unlike the perceived direction, putting accuracy (in degrees of deviation from the perfect aiming line) was not affected by head position. Novices did show a rightward putting error, while skilled players did not. We argue that the skill-related differences in putting accuracy reflect a process of recalibration. Implications for aiming in golf are discussed.

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Cornelius John, Andreas Stotz, Julian Gmachowski, Anna Lina Rahlf, Daniel Hamacher, Karsten Hollander and Astrid Zech

their shoes on and jump off the box with both feet in the direction of the landing line. Immediately after landing, the participant had to rebound for a maximal vertical jump. To assure that the participants understood the task and to avoid any incorrect trials, participants were asked to conduct some