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Hard courts vs. soft courts

Q: In the April issue of RSI, Crawford Lindsey provided the article “Follow the Bouncing Ball,” which describes the “coefficient of restitution” (COR) for a tennis ball as “0.6 for grass, 0.83 for hard courts, and 0.85 for clay courts.” Furthermore, the article says, “That means that a ball’s bounce will be the highest and fastest on clay, lowest and slowest on grass.” The article also states, “The harder the court, the higher the ball will bounce.”

If all this is not in error, then obviously clay courts, which we call soft, are harder than hard courts. I know this sounds like a line from comedian George Carlin, but if soft courts are harder than hard courts, why aren’t hard courts called soft courts?

I’m asking not because of ball bounce but because of player injuries. I see more injuries on clay courts because of the longer ball exchanges on each point, the physical exertion from getting to balls that are out of reach on the faster hard courts, and foot slippage from the lack of start/stop traction.

A: Good question, but the confusion stems from the fact that you are attempting to draw conclusions based on the coefficient of restitution for courts, rather than the coefficient of friction. According to From Breakpoint to Advantage: A Practical Guide to Optimal Tennis Health and Performance, by Dr. Babette Pluim and Dr. Marc Safran, the sliding characteristics of the court surface are more important than the cushioning properties. Surfaces that permit some sliding (such as clay) result in fewer injuries than surfaces that allow virtually no sliding (such as hard courts). This is because on clay, sliding to a stop lowers the peak force and spreads this already-lower force over more time. This translates to less wear and tear on your body. This conclusion is supported by statistics provided by the ATP, which show that players receive treatment at a rate of 0.37 times per match on hard courts (including carpet), compared to a rate of 0.20 times per match on clay. From Breakpoint to Advantage is available from RacquetTECH.com at a list price of $29.95.

From the August 2004 issue
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