According to many pros, tennis is an endurance sport and you should train for endurance to be at your best. Understand that many tennis matches go well over three hours and require a great number of repetitions, not only in hitting groundstrokes and serves but also in movement on the court.
Thus, there’s no questioning the fact that tennis requires endurance in order to be successful. But training for only endurance, which involves mostly cardiovascular and respiratory system improvement, is not the answer to improving your game.
Close examination of tennis play shows that most often court movements consist of quick, explosive periods of acceleration for 2-5 yards. These short bursts of speed and explosiveness are most often followed by “rest” during which the intensity drops and you recover.
When serving or hitting groundstrokes, you must exhibit explosive power or great force in hitting the ball, after which you “rest” in between points. There may be three or more repetitions of a groundstroke, but then it is always followed by a period of slow walking or relative inactivity.
Based on actual game play, you need more explosive power, speed and quickness rather than endurance. But yet, you must be able to repeat these bouts of explosive power, speed and quickness throughout the match.
Thus, it is more accurate to say that you need speed-strength (power) endurance to play the game well. Cardiovascular and respiratory system endurance comes into play mainly for recovery in between each of these bouts. Thus, you need a combination of both.
How much of each is determined by your present level of fitness. Most training, however, should be devoted to speed, quickness and explosive power or to speed-strength training, which can also develop aerobic and anaerobic power. This training can be followed by cardiovascular training to improve the pure endurance component.
However, if sufficient endurance training is done in childhood and during the teenage years, it will not be necessary to do much additional aerobic/anaerobic training when playing on the adult level.
For more information on tennis training, see Explosive Tennis: The Forehand and Backhand and Build a Better Athlete.