Article: article from journal or magazin.
Accuracy and Reliability of a New Tennis Ball Machine
Journal of Sports Science and Medicine
Brechbuhl, Cyril Millet, Gregoire Schmitt, Laurent eng Turkey 2016/06/09 06:00 J Sports Sci Med. 2016 May 23;15(2):263-7. eCollection 2016 Jun.
The aim was to evaluate the reliability of a newly-developed ball machine named 'Hightof', on the field and to assess its accuracy. The experiment was conducted in the collaboration of the 'Hawk-Eye' technology. The accuracy and reliability of this ball machine were assessed during an incremental test, with 1 min of exercise and 30 sec of recovery, where the frequency of the balls increased from 10 to 30 balls.min(-1). The initial frequency was 10 and increased by 2 until 22, then by 1 until 30 balls.min(-1). The reference points for the impact were 8.39m from the net and 2.70m from lateral line for the right side and 2.83m for the left side. The precision of the machine was similar on the right and left sides (0.63 +/- 0.39 vs 0.63 +/- 0.34 m). The distances to the reference point were 0.52 +/- 0.42, 0.26 +/- 0.19, 0.52 +/- 0.37, 0.28 +/- 0.19 m for the Y-right, X-right, Y-left and X-left impacts. The precision was constant and did not increase with the intensity. (e.g ball frequency). The ball velocity was 86.3 +/- 1.5 and 86.5 +/- 1.3 km.h(-1) for the right and the left side, respectively. The coefficient of variation for the velocity ranged between 1 and 2% in all stages (ball velocity ranging from 10 to 30 balls.min(-1)). CONCLUSION: both the accuracy and the reliability of this new ball machine appear satisfying enough for field testing and training. Key pointsThe reliability and accuracy of a new ball machine named 'Hightof' were assessed.The impact point was reproducible and similar on the right and left sides (+/-0.63 m).The precision was constant and did not increase with the intensity (e.g ball frequency).The coefficient of variation of the ball velocity ranged between 1 and 2% in all stages (ball velocity ranging from 10 to 30 balls.min(-1)).
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