It is commonly believed that when you get an injury it is due to lack of strength. This is true in many cases, since strength is a key element involved in injury. However, the main reason for most injuries occurring is poor technique and/or a lack of coordination. This is known as neuromuscular coordination, the interplay between the nerves and the muscles they affect. When you have good technique (good coordination), the muscles fire at the right time in the right sequence and with the right intensity. This enables you to do the movements smoothly without any interruption or abrupt changes in speed of movement. When there are flaws in your technique that disrupt coordination, then injuries can easily occur.
Strength plays an important role in coordination and is strongly involved. The greater your strength levels, the greater the forces that you can encounter, especially when you have some hits with poor technique or if you execute movements that your body is not accustomed to. The strength is very important in handling additional stress on the joints to help prevent injury. But, in all cases, developing good neuromuscular control is the key to not only more effective groundstrokes but also the prevention of injury.
This is one reason why it is important that youngsters first master correct and effective execution of the strokes involved in tennis. Wins and loses and exactly where the ball goes is not always of the greatest importance, even though we always like to see more wins and better shots. It is necessary to think long-range, i.e., where will the player be as a teenager or adult rather than how successful he or she can be at the earliest ages. By increasing strength and improving technique, you produce better strokes and have fewer injuries.