upper extremity power: tennis

Up until now, no consensus has been reached, although researchers have theorised that an optimal combination of strength and flexibility in the wrist and shoulder area would be necessary.

Now, new research carried out at Johns Hopkins University School of Medicine in Baltimore, Maryland, identifies factors which are critically important for powerful serving. At Johns Hopkins, researchers studied 40 tournament-level tennis players who had all been given a skill rating of 5.0 or greater by the National Tennis Rating Program. The subjects averaged 33 years of age (range 17- 50), were about 5'11' in height (range 5'2' to 6'4') and had an average percent body fat of 17 per cent (range 5-35 per cent). Thirty-six of the players were right-handed and four were left-arm dominant.

The athletes were tested for strength and flexibility and performed serves on an indoor tennis court. Each individual warmed up with 10 to 25 practice serves and then made six maximal serving attempts. Measurements of ball velocity for serves that cleared the net and landed in the service box were made with a Juggs radar gun.

The investigators found that several factors were important for strong serving. Not surprisingly, age had an inverse effect on service velocity (the older the athlete, the weaker the serve). Wrist flexibility was also critical (the more flexible the wrist, the higher the ball velocity). Flexible wrists appear to provide more 'snap' to the tennis racket just before ball impact and therefore boost velocity.

Shoulder flexibility was also essential for rapid serving. Those players with excellent flexibility of the shoulder when the arm moved straight ahead--or when the arm rotated inward--were likely to have much stronger serves than individuals with tight shoulders.

And, of course, strength measurements were important, too. Interestingly enough, the best predictor of serve velocity of all was 'elbow extension torque', ie, the ability of the triceps muscles in the serving arm to exert power. Also very important was the strength of internal rotation of the shoulder (the power exerted when the arm is rotated inwards towards the body)--and especially the ratio between shoulder internal-rotation and external- rotation strength. Those players with a ratio of about 4:3 (between internal-rotation and external-rotation strength) had the most powerful services. While some experts have argued that this ratio could increase the risk of injury, the Johns Hopkins researchers found no history of injury in the rapid servers. The 'torque imbalances' are also similar to those found in top- flight baseball pitchers and water-polo players.

This new study is a great one, because it identifies the factors which are important for rapid-fire serving and therefore permits the creation of an exercise programme which bolsters serving ability by enhancing specific strength and flexibility. In fact, in the next issue of PEAK PERFORMANCE, we'll describe a strength-building programme which can boost tennis serve velocity by over 10 per cent!

( ' Upper Extremity Physical Factors Affecting Tennis Serve Velocity, ' The American Journal of Sports Medicine, vol. 22 (6), pp. 746-750, ]994) Owen Anderson


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