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Practice effects on fast and accurate spatially constrained movements

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Pereira C. F., Marques I., Okazaki V. H. A.

Human Movement

2014

vol. 15

issue 1

4-11

Purpose. The effects of practice were analyzed in the control of fast and accurate spatially constrained movements. Methods. Twenty men (20-26 years old) evenly divided into an experimental and control group were analyzed in three time periods: pre-test, post-test, and retention. Discrete Aiming Task ver. 2.0 software simulated Fitts’ task (1954) and provided kinematic analysis of mouse cursor movements (displacement, velocity, and acceleration). The task consisted of using the mouse to click on two parallel targets as fast and accurately as possible. Four target widths (W = 2.0, 1.0, 0.5, and 2.5 inches) and three distances between the targets (D = 2.0, 4.0, and 8.0 inches) were used to provide indexes of difficulty (ID) from 1 to 6 bits. The experimental group performed 108 practice trials (three blocks of 36 trials on different days) while the control group had no practice. Results. Movement time (MT) decreased in the experimental group largely due in part to a reduction of time used for feedback. It is suggested that the improvement in performance as a function of practice occurred through the interdependence of programming and the feedback process. As the task was practiced, there was decreased need for feedback due to better pre-programming of the primary submovement and the improved use of sensorial feedback information. This strategy and a lengthened deceleration phase can help explain the paradigm of fast and accurate movement as a result of practice. Conclusions. Despite the improved performance changes as a consequence of practice, Fitts’ Law proved to be robust enough to predict MT as a function of ID.

Anticipatory Postural Adjustments in Dart Throwing

100%

Juras G., Słomka K.

Journal of Human Kinetics

2013

vol. 37

issue 1

39-45

The aim of this study was to explore the effects of accuracy constraints on the characteristics of anticipatory postural adjustments (APA) in a task that involves a movement consisting of a controlled phase and a ballistic phase. It was hypothesized that APA scaling with task parameters (target size) would be preserved even when the task is performed by muscles that have no direct effects on APA. Sixteen healthy right handed subjects participated in the study. All participants had no prior experience in dart throwing. Subjects’ average age was 24.1 ± 1.9 years. A force platform and a motion capture system were used to register kinetics of the body and kinematics of the throwing arm and throwing accuracy. The experiment consisted of six series of twenty consecutive dart throws to a specified target. Target sizes (T2-T6) were set at 25%, 50%, 75%, 125% and 150% of target 1 (T1) initially set as the spread of the last 20 throws in a 50 throw training session. This allowed to distinguish six indexes of difficulty (ID’s) ranging from 2,9 to 5,9. A one-way ANOVA for repeated measures was used for statistical analysis. Results of ANOVA showed a significant effect of target size at Constant Error but no effect at APA time. There were also no significant differences between hit and miss throws. From a control perspective, it can be stated that changes in central commands did not lead to changes in APA time in the analyzed motor task.

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1 Human Movement

1 Journal of Human Kinetics

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1 Juras G.

1 Marques I.

1 Okazaki V. H. A.

1 Pereira C. F.

1 Słomka K.

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Practice effects on fast and accurate spatially constrained movements

Anticipatory Postural Adjustments in Dart Throwing