Impact of a Ball Regulation Change on Game Performance and Shooting Play in Japanese U-15 Girls' Handball.

We aimed to investigate how a ball regulation change, implemented in U15 girls' handball games, now affects game performance and shooting plays. Over 14 matches (28 observations), we included all the attacks ( = 813) and shooting plays ( = 589) with the conventional ball and all the attacks ( = 821) and shooting plays ( = 618) with the new ball performed by both teams. We used notational analysis to compare the game performance and shooting plays in these two conditions. Our main results were as follows: (i) the attack efficacy was higher with the new ball (41.9%) than with the conventional ball (36.1%); and (ii) the prevalence of the three-line defensive system was higher with the new ball (10.5%) than with the conventional ball (2.7%). It can be inferred that the new ball enabled backcourt players to execute more powerful middle- and long-range shots, leading to their adoption of deeper defensive tactics that were effective in halting advancing backcourt players. Moreover, implementing new ball regulations resulted in a significantly higher frequency of shots targeted at the upper third of the goal frame (44.4%) compared to those observed with the conventional ball (35.8%). This implies that the introduction of the new ball enhanced precision control over shot placements, resulting in an increased player preference for targeting the upper course. Lastly, goalkeepers' saving rates decreased under the new ball, highlighting the need for technical and tactical coaching, tailored to goalkeepers. In summary, implementing the new ball regulations had a positive impact on Japanese U15 girls' handball performance.