One day, I strapped a racket to my body, turned on the ball machine, stepped into the ball and managed to get about six miles per hours more speed on my forehand shot than simply letting the ball bounce off my stationary racket. When we shot balls into a clamped stationary racket, the ball generally lost one-half of its speed coming off the racket. It's true that a clamped racket is not the same as a racket held in one's hand. But, as the ball is on the strings only four milliseconds, there wasn't much difference recorded when the stationary racket was hand held.
So, why did I only get six mph more speed when I stepped into the ball with no arm swing. Dr. Howard Brody discovered, the speed of your shot is determined by getting approximately 1.5 times your rackethead speed, plus one-half of the incoming ball speed. That rule applies to both ground strokes and serves. That means I was stepping into the ball at about 4 mph and 1.5 times 4 got me an amazing 6 mph moe speed.
Two handed backhand players normally step into the ball to free their upper body to uncoil. Plus, they need their lower body segments stabilized to uncoil their upper body, but If stepping into the ball contributes little to ball speed, why do many coaches think it's so important? Stepping into the ball just might get your center of gravity ahead of your front foot which will give you a faster first step towards the net than the player who faces the net and waits for the ball. But if you haven't been to the net since last April, stepping into the ball has very little value.
In a biomechanical study Drs. Ariel, Vorobiev and I did on Andre Agassi, we found he uses the forearm muscles, and physical principles, a little differently than most tour players. The majority of players generate rackethead speed by cordinating body link coiling and uncoiling, often called 'The kinetic chain'. One argument is that when one steps into the ball, there is a capability for greater body coiling and uncoiling. That also happens to be a myth, which will be discussed in another issue.
John Tichy, one of our coaches at the Tennis College hit a 124 mph while serving from his knees. Yet, we often see players take violent steps into the ball on the serve and the result is a helium ball. Think about it, for a player to hit a 100 mph serve, his rackethead speed must travel close to 66 mph. That means, if one used only his body on a serve, and used no internal rotation of the upper arm, and forearm pronation, one would have to step into the ball at about 66 mph. If one could do that he wouldn't need a car, he could just run to work on the freeway.