MADRID -- Novak Djokovic, winner of a record 24 Grand Slam titles, says he can feel the changes taking place in tennis.

The author says older tennis players can be safe and competitive. Good preparation, smart play and a healthy attitude are keys to success.

Tennis is a game you can play late into life as demonstrated by these three players who've been playing a minimum of 35 years at McAdams Park in Wichita.