By Larry Hodges
One of the most underrated strengths in table tennis is the ability to serve very low. How high your serve bounces on the far side of the table makes a big difference in how much clearance your opponent has in returning it. A very low serve means the opponent has to lift the ball, which makes an aggressive return difficult. A higher serve gives the receiver the clearance to be more aggressive.
When I ask beginning to intermediate students to show me with their hand where they contact the ball on their serve, they consistently put their hand four to five inches lower than where their contact point actually is. That means their serve is bouncing several inches higher on the far side of the table than it could be. This makes things quite a bit easier for the opponent.
A ball dropped from 30 cm over the table will bounce about 23 cm upward, according to ITTF rules. This means that a ball will bounce about 23/30 times the height it was dropped from (about .77). However, when serving, the ball bounces twice on the table. Roughly speaking, if you put no downward motion on the serve and ignore the affects of spin and air resistance, it's going to bounce just under .6 times as high as your striking point. (23/30 x 23/30 = about .59)
If the ball is contacted 6 inches higher than it needs to be, it'll bounce up about 3.6 inches higher on the far side then it needs to (.6 x 6), making things much easier for your opponent.
Therefore, to serve low, one must contact the ball low to the table. In fact, some top players contact the ball so low that they have to lift it or serve downward to get it to bounce high enough to go over the net.
Part of serving low, of course, is serving without hitting the ball downward into the table, which makes the ball bounce up higher. Similarly, an upward motion will make the ball go upwards, meaning it will bounce higher. Serve with a light touch, without much downward or upward movement of the ball, and the ball will not bounce as high. (When you serve backspin, you use a slight downward motion; however, the grazing motion, done correctly, means that the ball is directed forward, not downward. The same is true of a topspin serve with an upward grazing motion.)
If you contact the ball 12 inches above the table, it's going to bounce about 7 inches high on the other side, giving the opponent an inch of clearance over the six-inch net. If you contact the ball 8 inches above the table, you can keep its bounce about 4.7 inches on the far side, well below net height. This makes a huge difference in how strong the opponent's receive is going to be.
Have someone watch you serve, and have them tell you where your contact point is. Then practice contacting the ball from a lower and lower position, until your contact point is as low as possible. A good guideline is to try to contact the ball no higher than 8 inches high. From 8 inches high, the ball's first bounce will be barely over 6 inches, giving you minimum clearance over the net and a low serve bouncing just 4.7 inches on the opponent's side. Any less than 8 inches, and you'll have to either serve downward or lift the ball upward to make the ball bounce high enough to cross the net.