This is an excerpt from Championship Tennis by Frank Giampaolo & Jon Levey.
Unfortunately, tennis is full of stock teaching methodology that should be banished—well-intentioned, catchy phrases that have become dated or, worse yet, were never even correct to begin with. Here are a few of the bigger culprits concerning groundstrokes.
Roll over the ball for topspin. This is a favorite among TV commentators. Sadly, countless teaching pros are still using this phrase, too. Players try to time the racket roll at contact, resulting in shots that spray all over the court.
Here are the facts: Depending on the type of shot, the ball is on the strings for about 2 to 4 milliseconds. It takes another 150 to 200 milliseconds for an electrical signal to travel from a player's hand back to the brain. The brain then sends a new motor program back to the muscle group to begin the wrist roll. This takes an additional 150 to 200 milliseconds, by which time the ball is now 8 to 10 feet off the racket face toward the opponent's side of the court. In other words, it's impossible to roll over the ball for topspin. The spin comes from the brushing motion of a low-to-high swing path.
Watch the ball hit the strings. As mentioned earlier, the human eye cannot register a two-millisecond event. No one has ever seen a ball hit the strings. It's simply a blur. Keeping the head down and still through contact is the best recipe for a steady racket path through the strike zone. Watch film of the best baseliners, and it's easy to see how quiet they keep their head during their groundstrokes.
Skim the net. On television, it appears that professionals barely clear the net on their groundstrokes. This is rarely the case. The deception occurs because the television cameras at pro tour events are often placed high in the stadium. This angle offers a clear view of match play, but it distorts the trajectory of the ball flight.
In actuality, players use a variety of heights, generally dictated by their court positioning. This is often the result of managing the time between hits. When players are on the defensive, they generally hit higher to buy more time for recovery. Conversely, they move forward and hit harder and lower to take time away from a vulnerable opponent.
At the club level, a ball that barely clears the net lands midcourt and bounces perfectly into an opponent's primary strike zone; this is not recommended unless losing is the main objective. The net skimmer only becomes a smart choice when the opponent is transitioning to or established at the net and a passing shot is in order, or when an opponent is well behind the baseline and the player wants to bring her in, specifically if the opponent is weak at the net.
Stay down on groundstrokes. A player's center of gravity plays an important role in generating power and depth on groundstrokes. Three critical elements lift up on world-class strokes: the knees, the backside, and the racket face. Even on slice backhands, all three critical elements rise at completion of the stroke. If not, the resulting shot will lack pace and penetration. Players who prematurely lift their head before contact do indeed need to “keep their head down” through the shot. But it's a fallacy to apply the principle to the entire body.
Keep your eye on the ball. This is correct . . . half the time. Vision control plays various functions over the course of a point that are critical for consistent ball striking and court coverage. Narrow vision is applied on an incoming ball: watching it leave the opponent's racket, cross the net, and bounce up and into the strike zone. In this regard, a player should absolutely be keeping an eye on the ball.
Broad vision, on the other hand, is used to spot the dozens of visual clues after the ball leaves the racket toward the opponent's side of the court. Such clues include an opponent's court position, body language, strike zones, swing speed, and swing length. Broad vision is a crucial component of anticipatory speed. The best movers know how to assimilate the information from their broad vision and instinctively adjust their positioning accordingly.
Read more from Championship Tennis by Frank Giampaolo and Jon Levey.