The ball takes off too fast on those courts for any talented youngsters to develop the solid ground strokes that you can't learn after you're 21. (si.com)
Newer recommendations suggest that you start your workout routine with a warm - up, such as an easy walk or a sport - specific routine, such as serving some tennis balls and practicing ground strokes before a match. (health.harvard.edu)
For a typical ground stroke with a horizontal velocity of 25 meters per second, a ball of radius 0.033 meter will have to be spinning at greater than 120 revolutions per second. (scientificamerican.com)