the purpose of this study was to evaluate the heart rate responses of the 2 Multiball table tennis interval training protocols during the competitive period on young table tennis players. Fourteen (n=14) players, aged 12±2yrs participated in this study. participants were randomly divided into 2 training duration groups (15s vs. 30s) and were trained under the 2 interval protocols for 6 weeks (3 sessions. w -1 ). heart rate (hr) data was electronically recorded by using the Polar Team System at the completion of each exercise at the 1 st and 5 th set in the 1 st and 6 th week. the Wilcoxon signed-rank test was applied in order to compare the repeated measurements, whereas spearman's rank correlation (ρ) analysis was employed to determine whether the testing parameters are significantly related. From the results it is shown that regarding to the hr both training protocols can simulate the match conditions. In both groups participants' the footwork exercises with Forehand and Backhand strokes recorded the higher hr (190-210 b.min -1 ). additionally, significant hr differences were recorded in group a (z=-2.023, p=0.043) in Footwork Forehand Backhand (FtFB). In conclusion, both Multiball protocols can generally simulate match conditions supporting the weekly training program of young table tennis players.

The present study investigated the generalizability of contextual interference effects by extending previous laboratory and field research to novel movements controlled by different motor programs. 30 men and 33 women learned novel throwing and kicking tasks, practicing with blocked, serial, or random schedules. The subjects practiced the tasks four days a week for two weeks and then were given a postest. One week later subjects were given a retention test. Significant improvements in performance were found for all groups for both tasks; however, a significant effect for practice condition was found only for the throwing task during retention, for which the random practice schedule led to better learning than the blocked and the serial practice. These findings suggest that the blocked, serial, and random practice methods could be effectively used for tasks controlled by different motor programs but must be practiced in the same teaching session, without expecting one to be more effective in learning than any other.

Perceived parental screen time rules play a role in the amount of screen time among adolescents. Interventions that focus on parental limit setting development and physical activity support may be effective in decreasing screen time among youth aged 13-15 years.

Certain environmental predictors influence adolescents' screen time, as a result, corrective intervention should aim at the family as a whole, as this whole shapes home environment.

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