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In the present investigation we determined the time course of attention demands during the jumping service in volleyball by the dual-task paradigm. Fourteen voluntary junior elite volleyball players performed 60 jumping serve. Jumping-serve performance (JSP) as primary task and verbal reaction time (RT) to an auditory stimulus that was administered in four probe positions (PP), as secondary task was measured. Repeated measures analyze of variance (ANOVA) showed no significant effect of the PP on JPS, indicates allocating the most attentional weight to the JSP. In second analyze, effect of PP on RT was significant, so that all probes RT were significantly higher than the base line RT, indicates attention demanding of the JSP. Results also showed that pre-shot in run-up (PP1) and after the ball strike (PP4) had the greatest attentional demands respectively while per-jump stepping ahead (PP2) and just pre-striking the ball (PP3) had respectively the lowest needs of attention. The results indicate that attention follows a non-linear pattern, in the JSP.

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In the current research, the dual-task paradigm was used to examine the temporal distribution of attentional demands during a tennis serve. Twenty experienced tennis players to performed tennis serves. The participants were asked to respond verbally to an auditory tone presented at four probe positions (PPs) during tennis serves. The probe reaction time measure of attention was administered during four segments of a tennis serve including preparation period (PP1), from onset of backswing-loading (PP2), from onset of forward movement just before stroke in the exploding period (PP3), and after the stroke during follow-through (PP4). Reaction time was significantly longer when the probe stimulus was presented at PP4 than those of the other segments. Reaction time at PP2 was significantly greater than those of PP1 and PP3. The results showed a unique non-liner distribution of attentional demands for tennis serves. It appears that monitoring of proprioceptive feedback following movement begins, and that initiation of corrective sub-movements is necessary for skillful performance of tennis serves. So it is concluded that from a motor control perspective, PP2 is the most important segment during a tennis serve.

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In this investigation the authors presented an attentional demand explanation for the choking under pressure occurred in sport skills. For this porpouse, attentional demands in tennis serve performance was compared under low and high pressure conditions by using dual task paradigm. Twenty tennis players served as participants and performed sixty serves as primary task in low and high (competition) conditions. Secondary task was to respond an auditory stimuli that presented during tennis serve in four probe positions. The results showed that on one hand, the pressure condition deteriorated tennis serves performance and on the other hand, it caused an increment in level of attentional resources and changeed pattern of attentinal demands. The results indicated that skillful athletes allocated more attention to their performance and more focusing to some positions of the skill under pressure condition compared to normal condition. It suggested that such attention demands changes can cause choking in sport. The results provide objective and stronge support for the predictions of self-focus theories proposed for choking in sports.