I NTRODUCTION

1. EFFECTS OF AGE AND STIMULUS VELOCITY ON THE PERFORMANCE OF A COMPLEX COINCIDENCE-ANTICIPATION TASK BY CHILDREN AND ADULTS Teresa Figueiredo¹ João Barreiros² teresa.figueiredo@ese.ips.pt, jbarreiros@fmh.utl.pt ¹ Department of Sciences and Technologies, Polytechnic Institute of Setúbal, Portugal ² Faculty of Human Kinetics, University of Lisbon, Portugal • INTRODUCTION • The coincidence-anticipation capacity is determinant in performing sports skills. Coincidence-anticipation requires anticipatory prediction, that is, the capacity to anticipate the trajectory of a stimulus moving in space and time and to tuning and synchronization motor actions. • Complex coincidence-anticipation tasks involve the production of a motor action to intercept a moving target, either using a segment of the body or an external object. In the past, research focused on these tasks has shown conflicting results: • Five studies indicate that the response error increases at the slower speeds of the visual stimulus presentation (1 to 5) • Three studies observed more accurate responses on coincident timing performance at the slower stimulus speeds (6 to 8). • The aim of this study is to examine the effect of stimulus velocity on the performance of a complex coincidence-anticipation task by children and adults. • OUTCOMES • DATA ANALYSIS • The magnitude and the direction of the response error were recorded for each trial. For the analysis of the response error, absolute error (AE) and variable error (VE) measures were calculated for each age group. A 2 (groups) x 4 (stimulus speed) analysis of variance with repeated maesures on the last factor was performed for each dependent variable. Also, the extension of the One-Way ANOVA was used for studying the dominant trend in the observed results for the different target speeds. This has been accomplished through polynomials orthogonal contrasts. For the statistical analysis the assumed significance level was α = 0.05. • Table 1: Mean (M) and standard deviation • (SD) for the absolute and variable errors • at the different target speeds. • Fig. 2: Mean absolute error as a function of • stimulus speed. • Fig. 3: Mean variable error as a function of • stimulus speed. • RESULTS • Adults performed the task more accurately and consistently than children at all target speeds. • For both children and adults, there was a significant decrement in the AE and VE performances from the faster speed (3.21 m/s) to all other target speeds, as well as between the two lowest speeds (1.61 m/s and 0.71 m/s). • A dominant linear trend was found to explain children and adults’ performance variability, in terms of accuracy and consistency, at the various stimulus speeds. • MATERIAL AND METHODS • PARTICIPANTS • Twenty-four right-handers equally distributed for both genders, 12 children (9.48 ± 0.79) and 12 undergraduate students (21.61 ± 1.46), volunteered to participate un the study. None had previous experience on the experimental task. • TASK AND APPARATUS • An adaptation of the Bassin Anticipation Timer to simulate a moving target was used, with a runway of 43 sequentially illuminated LEDs (270 cm long). • The task consisted of throwing a mini-tennis ball over the shoulder to intercept the luminous target, and the participants were required to produce the response as soon as they were ready to take a decision about the displacement of the luminous target along the runway. • At the end of each practice trial, it was possible to collect two measures for the evaluation of the response: (a) the place where the ball intercepted the light runway; (b) the position of the target when the ball intercepted the light runway. • PROCEDURES • The participants stood in the centre and in front of the apparatus, at a distance of 270 cm from the target. The motion of the light sequence was presented from left to right, at a height of 140 cm from the ground, for both age groups. • All individuals practiced five 24-trial blocks with the target speeds of 0.36 m/s, 0.71 m/s, 1.61 m/s and 3.21 m/s, and they performed 30 trials for one target speed before the presentation of another one. There was a two-minute rest interval between consecutive blocks of practice. • Knowledge of results, related to the direction and spatial magnitude of the response error, was supplied for 5 sec at the end of each practice trial and the intertrial interval had the overall duration of 10 sec. • Fig. 1: Apparatus used for the gathering of the data. • DISCUSSION • This study investigated the effect of stimulus velocity in a coincidence-anticipation throwing task performed by children and adults. • For both children and adults there was an increment of the AE and VE measures as the stimulus speed increases, and a dominant linear trend was found to explain the performance changes at the various target speeds. • A possible explanation for these findings may be related to differences in processing time information: • With the increase of the visual stimulus speed, the stimulus duration and the time available for the information processing become progressively shorter; this could lead individuals to automatically respond, or use stereotypic movements by a “default” processing at the faster stimulus speeds based on the subliminal perception and pre-programming of movement (6 and 9). • Similarly, the longer viewing time provided by slower stimulus speeds could have improved perceptual estimates, decision making and planning of movement (8). • Further research is needed on the influence of stimulus velocity on the visual processing information and control of anticipatory tasks, mainly focusing on sports skills that have rarely been used in previous studies. 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