Originally Posted by LeeD
I always thought it was a KNOWN fact that players with good strokes almost always hit harder with more flexible rackets, because when they use stiff rackets like PureDrives, the ball goes OUT OUT OUT, so they add more spin or swing more controlled, giving them LESS power.
On a flexi racket, the ball stays IN, so they can swing hard, and the ball goes faster.
I think one of the reasons that high-level, hardhitting players use flexible racquets is dwell time. The faster the incoming ball and the faster the racquet-head speed the shorter the time the ball is in contact with the strings. Some people find brief dwell time to be good for control, others feel that long dwell time allows them to cradle the ball on the strings and fling it where they want it to go. In order to have long dwell time with really fast swings and incoming balls you either need a flexible racquet, flexible strings, or loose strings, or some combination of those things. I look at a guy like Berdych and it makes sense that he uses a stick with sub-60 flex. If he used a stiff frame he would have little dwell time and might not be able to control his shots.
Of course, he probably grew up playing flexible racquets and developed his technique, timing and feel for the ball with them. If he had grown up with stiff frames he might be comfortable with briefer dwell time and might still be using stiff racquets.