Seibu Lions used for the first time the "expanded base," which will be introduced at regular season this season, on the first day of spring camp. Base running was performed. The top batter was Takayoshi Yamamura infielder (23). The distance they ran was gradually increased, first to first base, then around first base to first and second base, and fielder everyone got a good feel for it.

Major League Baseball will begin using it in 2023. Professional baseball aims to introduce it in regular season next season. The expansion of the stadium from the current 15-inch (approximately 38.1 cm) square used in professional baseball to the major league standard of 18 inches (approximately 45.7 cm) square will also narrow the distance between bases.