The Encarta Dictionary lists conditioning as a "gradual training process," and this process in our definition covers many aspects. These aspects of conditioning are aerobic conditioning, anaerobic conditioning, conditioning for strength, and conditioning for movement/speed, etc. For now, we will focus on the aerobic and anaerobic training of a tennis player.

Aerobic is defined as needing oxygen to take place. Aerobic activity includes longer duration and steady-paced movements that require the body to receive energy from burning carbohydrates and fats using energy pathways that include oxygen.

Anaerobic is defined as not needing oxygen to take place. Anaerobic activity includes high-intensity, short-duration events that use stored energy in the muscles or energy made rapidly when you initiate the activity.

According to USPTA Master Professional Dave Porter, "Conditioning for tennis should include explosive movements over relatively short distances with emphasis being placed on maintaining appropriate balance. This almost always involves changing directions. Utilize games and drills that most closely resemble actual playing situations. At the early stages this may mean designing on-court games using racquets that challenge a player's ability to work when tired.

"At the higher levels this means creating a workload that places a player in oxygen debt (oxygen requirements are greater than a player's ability to replace used oxygen) and then training at that level. This ultimately will increase what is referred to as the anaerobic threshold or the place where the workload challenges both the physiological and psychological peaks. Gradually increasing this threshold will give a player both a physical and a mental advantage in competition