Definition
In tennis or similar sports, players warm up by rallying the ball to each other before the game starts.
（网球等运动）赛前练习
Before the match, players usually knock up to prepare themselves for the game.
比赛前，球员通常会先进行赛前试打，为比赛做好准备。
The coach asked the players to knock up thoroughly before the game to ensure they are ready.
教练要求球员在比赛前彻底进行赛前试打，确保他们已准备好。
We always arrange to knock up together before the season starts to improve our performance.
我们总是在赛季开始前安排一起赛前试打，以提高我们的表现。