Since a curveball has topspin, that means the air behind it gets deflected upwards.

由于弧线具有上旋， 着它后面空气会向上偏转。

You gotta put that topspin on it.

你得给它加上上旋。

For example, Serena's average topspin serve is about 145 kilometers per hour, 25 kilometers per hour slower than her power serve.

例如，塞雷娜平均上旋时速约为145公里，比她强力慢了25公里。

Man wouldn't know topspin if it hit him in the ball sack.

被击中下身才会知道上旋厉害。

Think of Nadal's swing; everything he does is to impart strong topspin on the ball.

想想纳达尔挥;他所做一切都是为了在上赋予强大上旋。

It created a string bed that generated so much topspin that it was quickly banned by the International Tennis Federation.

它创造了一个产生如此多上旋弦床，以至于它很快被国际网联合会禁止。

So, Serena could be about to deliver a topspin serve, a power serve, or even a slice serve.

所以，塞雷娜可能会出上旋、强力甚至切削。

As long as you follow the eight-step practice method we mentioned last time, and can control the ball, play some gentle rallies with others, understand what a topspin stroke is, and can turn your shoulder, that's a 2.5 level forehand.

只要按照我们上次提到八步练法，并且会控， 跟别人打一些温和拉，明白什么是上旋，能转肩， 那就是 2.5 级正手。

But topspin serves are more accurate and still difficult to return.

但上旋更准确，仍然很难被回击。

That's where power and topspin come in.

那就是力量和上旋挥作用地方。

Understand the importance of topspin and using lobs to get the ball over the net at a higher trajectory.

了解上旋和使用吊以更高轨迹将越过网重要性。

Because you see, the open stance shot doesn't have that topspin, and in an actual match, it can save two seconds.

因为你看， 开放站姿击没有那个上旋，在实际比赛中， 它可以节省两秒钟。

However, it has a high topspin, and it's awkward to return.

然而，它带有强烈上旋，回起来很别扭。

As long as you follow the eight-step practice method we mentioned last time, can control the ball, play some gentle rallies with others, understand what a topspin stroke is, and can turn your shoulder, that's a 2.5 level forehand.

只要按照我们上次提到八步练法，能控， 能跟别人打一些温和拉，明白什么是上旋，能转肩， 那就是 2.5 级正手。

That's because the topspin on the ball forces it to drop sharply right before it reaches the opponent.

那是因为上上旋迫使在接近对手之前突然下坠。

That's why Serena also uses topspin to her advantage, usually when her first power serve goes out of bounds.

就是为什么塞雷娜也会利用上旋优势，通常是在她第一次强力出界时。