Serve Racquet Head Speed
You can click on the pictures for a larger version.
Recognize this fellow? It's Pete Sampras slamming a serve at the US Open. What's the swirling pattern around him? That's the pattern that the tip of his racquet head made from pre-toss to his post-serve follow-through. We superimposed the racquet head tip's path for the entire serve over this single picture of Sampras. We actually marked the tip of the racquet head (one point) in about 200 separate video frames and then combined the points into this pattern.
We call these "serve silhouettes". A silhouette is a dark outline of an object against a light background. Although we use colors now - blue for the racquet head tip and yellow for the ball - when we first started this study everything was black against white. Hence the name "silhouette" and the name stuck.
On the next page you'll find 10 serve patterns. The patterns represent 5 pairs of first and second Sampras serves. But we've shuffled them around and mixed them up. Can you do the following? Tell us which are 1st serves and which are 2nd serves? Can you tell us what type of serve each pattern is: flat, slice, American twist (kick) serve?
One thing that you might try to do is print the next page out. Cut the charts out and place two charts that you feel are similar over one another and hold them up to a light so that you can see through one chart and see the other. Now compare the charts and start grouping similar patterns.
Alternately click on each chart and you will see a larger version of that chart that fits on a full sheet of paper. Print the larger charts out and place two of the larger charts over one another and follow the same procedure that we just described. Sort the charts. Remember there are 5 1st serves and 5 second serves. Then try and determine which type of serve each one is.
We'd like to point out a few things about the patterns. We started with Pete Sampras, but have begun to look at serve patterns for Venus Williams and Martina Hingis. The first thing, principal investigator, Dr. Jani Macari Pallis, noticed was Sampras' smooth fluid circular motions. When the second silhouette was completed, it had the same almost identical pattern and so did the third one. Then we started calculating the velocity of the racquet head tip. The velocities (speed) for the racquet head tip is also very consistent from one serve to the next. Sampras not only has a consistent pattern of motion but a very consistent velocity of motion.
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