practice swing
Refers to swinging a sword, bat, racket, etc. without hitting a ball or target, as a warm-up or form practice. Common in sports and martial arts.
I take practice swings before stepping into the batter's box.
I did one hundred practice swings in kendo training.
素振り is specifically a practice swing (e.g. in baseball or swordsmanship), while 振り alone is the general word for any swinging motion.
Formed from 素 “without anything added or involved” and 振り “swing,” referring to a swing made without striking a ball or other target.