Introduction During last few years, important changes in table tennis rules have been introduced: increasing in ball weight (from 2.5 to 2.7 gr.) and diameter (from 38 to 40 mm), and reducing match`s score (from 21 to 11 points). Supposed to reduce rallies speed, these modifications should require adaptations in player way of acting and in his/her physical preparation, due to observed increasing duration in rallies (see players and trainers comments published in domain journals, Jégouzo, 2001, FTT Magazine, 750, 16-17 ; Sève, 2001, FTT Magazine, 758, 12-13). In this study we analyze movement adaptations and physiological implications caused by changed ball size. We suppose that increasing the diameter of table tennis ball generates adaptations in player`s drives, mainly in terms of movement amplitude and energy consumption (deduced through heart rate and effort perception). These adaptations depends on player`s practice level. Method: Subjects are asked to perform a returning task of 60 balls at the rate of 1 ball per second, both with 38mm and 40mm balls. In test 1, subjects are experts players (n=9, National level) and beginners (n=9, subjects who have acquired fundamentals of activity). In test 2, subjects (n=11) have at least a 5 years experience in table tennis practice. We record precision and amplitude of drive movement (test 1), precision, heart rate and effort perception by means of Borg scale (1998, Borg`s perceived exertion and pain scales, Champaign, IL, Human Kinetics) (test 2). Main results: Test 1: experts are more accurate than beginners (67% of success versus 43% ; F(1,16)= 37.8, p<.05) and both practice levels show a lower performance with 40mm balls (F(1,16)= 6.8, p<.05). Results show a movement amplitude adaptation (ampler movement) changing from 38mm to 40mm balls exclusively for high level players (F(1,16)= 7.4, p<.05). Test 2 : we find again, as in test 1, higher performance with 38 than 40 mm balls (73 ± 10.1% of success versus 67.7 ± 8.2% ; p<.05). On the other hand, no significant differences are observed concerning heart rate (170.3 ± 12.2 bpm versus 170.3 ± 13.3 bpm ; p=ns) and perceived effort (14.4 ± 1.3 versus 14.9 ± 1.6 ; p=ns). Discussion and conclusion: These two experiments show that changing in ball diameter, from 38 to 40 mm, generates a reorganization of pattern movement and that movement adaptation depends on players` practice level. Results put in evidence that table tennis players, despite rules changes, try to accelerate movements and to play more powerfully, maintaining a constant effort.
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