Purpose:
This study aimed at determining: (a) whether the effect of modifying ball mass allowed youth basketball players to attempt a greater number of lay-ups and hook shots during real games, and (b) whether the modification affected successful shots.

Methods:
Fifty-four boys from six basketball teams, aged between 10–11 years, participated in the study. The independent variable was ball mass and the dependent variable was the attempted and successful type of shots (set and jump shot, lay-ups, and hook shot). We established three situations in which four games were played with each of the following balls: (a) a regulation ball, (b) a ball of smaller mass (440 g), and (c) a ball of greater mass (540 g). Four observers were trained (intra- and inter-observer reliability > 0.96). Four observers recorded the data utilizing a systematized register from observation of the game videos.

Results:
A higher percentage of lay-ups were attempted with the 440-g ball in comparison with the regulation ball (U = 227906, p = 0.01, ES = 0.152) and with the 540-g ball (U = 218614, p = 0.01, ES = 0.160). A higher percentage of lay-ups were successful with the 440-g ball in comparison to the 540-g ball (U = 223080, p = 0.02, ES = 0.210).

Conclusions:
Only attempted lay-ups increased with the 440-g ball in comparison to the regulation ball, but the percentage of the rest of kinds of attempted shots and successful shots were similar when comparing the modified balls to the regulation ball.