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Sergio L. Molina and David F. Stodden

practices of practitioners (e.g., physical educators, coaches, and other movement educators). Fitts’ law ( 1954 ) and its application, the speed-accuracy trade-off, are well-known principles that can be applied to many fundamental movements and performance ( Urbin, Stodden, Fischman, & Weimer, 2011

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Tsung-Yu Hsieh, Matheus M. Pacheco, and Karl M. Newell

The goal of present experiment was to test whether different speed-accuracy paradigms outcomes (time minimization and time matching) were due to different temporal and spatial task constraints. Fifteen participants twice performed 100 trials of time minimization and time matching tasks with the yoked temporal and spatial requirements (criterion time and target width). The results showed that performing an aiming movement under the same spatial and temporal constraints resulted in similar outcomes with distributional properties (skewness and kurtosis) being slightly affected by practice effects. There was a trade-off in the information entropy for space and time (temporal information entropy decreased as spatial information entropy increased) with practice. Nevertheless, the joint space-time entropy of outcome did not change across tasks and conditions—revealing a common level of space-time entropy between these two categories of aiming tasks. These findings support the hypothesis that under the same spatial and temporal constraints the movement speed-accuracy function shares the same properties independent of task category.

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Stacey L. Gorniak, Marcos Duarte, and Mark L. Latash

We explored possible effects of negative covariation among finger forces in multifinger accurate force production tasks on the classical Fitts’s speed-accuracy trade-off. Healthy subjects performed cyclic force changes between pairs of targets “as quickly and accurately as possible.” Tasks with two force amplitudes and six ratios of force amplitude to target size were performed by each of the four fingers of the right hand and four finger combinations. There was a close to linear relation between movement time and the log-transformed ratio of target amplitude to target size across all finger combinations. There was a close to linear relation between standard deviation of force amplitude and movement time. There were no differences between the performance of either of the two “radial” fingers (index and middle) and the multifinger tasks. The “ulnar” fingers (little and ring) showed higher indices of variability and longer movement times as compared with both “radial” fingers and multifinger combinations. We conclude that potential effects of the negative covariation and also of the task-sharing across a set of fingers are counterbalanced by an increase in individual finger force variability in multifinger tasks as compared with single-finger tasks. The results speak in favor of a feed-forward model of multifinger synergies. They corroborate a hypothesis that multifinger synergies are created not to improve overall accuracy, but to allow the system larger flexibility, for example to deal with unexpected perturbations and concomitant tasks.

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Elizabeth J. Bradshaw and W.A. Sparrow

The study examined adjustments to gait when positioning the foot within a narrow target area at the end of an approach or “run-up” similar to the take-off board in long jumping. In one task, participants (n = 24) sprinted toward and placed their foot within targets of four different lengths for 8-m and 12-m approach distances while “running through” the target. In a second task, participants (n = 12) sprinted toward and stopped with both feet in the target area. Infra-red timing lights were placed along the approach strip to measure movement times, with a camera positioned to view the whole approach to measure the total number of steps, and a second camera placed to view the final stride, which was analyzed using an in-house digitizing system to calculate the final stride characteristics. In the run-through task, a speed-accuracy trade-off showing a linear relationship (r = 0.976, p < .05) between target length and approach time was found for the 8-m amplitude. An accelerative sub-movement and a later targeting or “homing-in” sub-movement were found in the approach kinematics for both amplitudes. Final stride duration increased, and final stride velocity decreased with a decrease in target length.

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Phillip D. Tomporowski and Michel Audiffren

Thirty-one young (mean age = 20.8 years) and 30 older (mean age = 71.5 years) men and women categorized as physically active (n = 30) or inactive (n = 31) performed an executive processing task while standing, treadmill walking at a preferred pace, and treadmill walking at a faster pace. Dual-task interference was predicted to negatively impact older adults’ cognitive flexibility as measured by an auditory switch task more than younger adults; further, participants’ level of physical activity was predicted to mitigate the relation. For older adults, treadmill walking was accompanied by significantly more rapid response times and reductions in local- and mixed-switch costs. A speed-accuracy tradeoff was observed in which response errors increased linearly as walking speed increased, suggesting that locomotion under dual-task conditions degrades the quality of older adults’ cognitive flexibility. Participants’ level of physical activity did not influence cognitive test performance.

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Elizabeth J. Bradshaw and W.A. Sparrow

Adjustments to gait were examined when positioning the foot within a narrow target at the end of an approach for two impact conditions, hard and soft. Participants (6 M, 6 F) ran toward a target of three lengths along a 10-m walkway consisting of two marker strips with alternating black and white 0.5-m markings. Five trials were conducted for each target length and impact task, with trials block randomized between the 6 participants of each gender. A 50Hz digital video camera panned and filmed each trial from an elevated position adjacent to the walkway. Video footage was digitized to deduce the gait characteristics. A linear speed/accuracy tradeoff between target length and approach time was found for both impact tasks (hard, r = 0.99, p < 0.01; soft, r = 0.96, p < 0.05). For the hard-impact task, visual control time increased linearly (r = 0.99, p < 0.05) when whole-body approach velocity decreased. Visual control time was unaffected by whole-body approach velocity in the soft-impact task. A constant tau-margin of 1.08 describes the onset of visual control when approaching a target while running, with the control of braking during visual control described by a tau-dot of –0.85. Further research is needed to examine the control of braking in different targeting tasks.

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Marcos Duarte and Sandra M.S.F. Freitas

We investigated the speed and accuracy of fast voluntary movements performed by the whole body during standing. Adults stood on a force plate and performed rhythmic postural movements generating fore and back displacements of the center of pressure (shown as online visual feedback). We observed that for the same target distance, movement time increased with the ratio between target distance and target width, as predicted by Fitts’–type relationships. For different target distances, however, the linear regressions had different slopes. Instead, a single linear relation was observed for the effective target width versus mean movement speed. We discuss this finding as a result of the pronounced inherent variability of the postural control system and when such a source of variability is considered, the observed relationship can be explained. The results reveal that the accuracy of fast voluntary postural movements is deteriorated by the variability due to sway during standing.

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Dalia Mickeviciene, Renata Rutkauskaite, Dovile Valanciene, Diana Karanauskiene, Marius Brazaitis, and Albertas Skurvydas

ages choose during speed–accuracy decision-making tasks. Would they prefer speed at the expense of accuracy or accuracy at the expense of speed? In our study, the subjects were asked to perform a movement not only as fast and accurately as possible, but also to react quickly. Therefore, it can be said

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Laura Žlibinaitė, Rima Solianik, Daiva Vizbaraitė, Dalia Mickevičienė, and Albertas Skurvydas

to move only in a horizontal plane). During the speed–accuracy task, the participant was required to position the handle symbol (0.0035 m in diameter) in the start zone on the computer screen. The participant then had to react to the target (a green circle, 0.007 m in diameter) on the computer screen

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Simon A. Feros, Kris Hinck, and Jake Dwyer

Pace bowling is a specialist role within the cricket team, whereby bowling speed, accuracy, and a high degree of consistency are important assets in reducing runs scored and dismissing opposition batters. 1 , 2 In addition, bowling “rhythm” is believed to be an important attribute for pace bowlers