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

但它的上旋较高，回比较困难。

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

由于弧线具有上旋， 这意味着它后面的空气会向上偏转。

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

被击中下身才会知道上旋的厉害。

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

因此，小威可能会发出上旋发、强力发，甚发。

That's where power and topspin come in.

这就力量和上旋进入的地方。

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

想想纳达尔的挥杆;他所做的一都为了在上赋予强大的上旋。

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

这因为的上旋迫使它在到达对手之前急剧下降。

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的弦床，以于它很快被国际网联合会禁止。

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

但上旋发更准确，而且仍然很难回击。

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的轨迹将越过网的重要性。

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。

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

这就为什么小威也会利用上旋来发挥自己的优势，通常在她的第一次强力发出界时。

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

例如，小威的平均上旋发速度约为每小时145公里，比她的强力发慢每小时25公里。

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的八步练法，能控， 能跟别人打一些温和的拉，明白什么上旋，能转肩， 那就 2.5 级的正手。

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的八步练法，并且会控， 跟别人打一些温和的拉，明白什么上旋，能转肩， 那就 2.5 级的正手。