TENNIS BIOMECHANICS

INJURY POTENTIAL OF CORE STROKES In competitive tennis, the forehand accounts for 70% of all the strokes played in a match, and for most players it is one of the main weapons for winning points. Lighter rackets, harder court surfaces and fitter players means that technique has changed dramatically over the last 30 years - gone is the sliced shot played side- on with a continental grip from below knee level yards behind the baseline! Players now employ extreme grips such as semi-westerns (eg. Agassi) and westerns (eg. Ferrero and Mauresmo), allowing the ball to be hit at shoulder height from an open stance (ie. with the feet facing the net), with considerable topspin and greater force, making life far more difficult for opponents. Biomechanically, the mod- ern forehand involves much greater trunk rotation, generated by ground reaction force and leg drive, and resulting in a high racket head momentum. Executed properly with the body segments moving in the cor- rect sequence of the kinetic chain, it is a very effective way of hitting the ball hard and keeping it in court while minimising injury potential. However, the weekend player who watches his heroes winning Grand Slam tournaments may not see all the elements of the stroke, and subse- quently attempts the shot with the west- ern grip and open stance, but omits the trunk rotation. The result is a stroke where all the racket head momentum has to be produced from the shoulder with contribu- tions from the elbow and wrist. The subse-

Figure 2: Full western forehand grip used by the women’s world number 6 seed, Amelie Mauresmo

quent increase in load and stress on those joints carries a higher risk of injury to the player, especially as his racket is likely to be lighter than the professional’s and therefore has to be swung faster in order to generate the same momentum. The message for the club player is that a small coaching input may ultimately save you the frustration and pain of injury, not to mention cost of treatment afterwards.

LINKING TECHNIQUE AND TACTICS The serve represents the only time a play- er starts in total control of the ball, and

Figure 1: Semi-western forehand grip used by Andre Agassi

generation of maximum power and spin along with accurate placement, are the key to being able to win at least half the games in a match. In performance level play there are two main stances, or start- ing positions, used:

The ‘foot-up’ or pinpoint serve (eg. Lleyton Hewitt) - the back foot is dragged up to behind or alongside the front foot during the ball toss so that both feet are together during the leg flexion and drive that lifts the player off the ground to make contact with the ball, before landing on the front foot (see figure 3).

The ‘foot-back’ or platform serve (eg. Pete Sampras) - the server keeps both feet apart throughout the whole service action, and may land on either the front or the back foot (see figure 4). The appar- ent benefits and drawbacks of these styles of serve have been the focus of much discussion amongst coaches - are there differences in the ground reaction forces generated, does one style favour body rotation more than the other? Current coaching “wisdom” which is based purely on subject observation, says that a pinpoint serve produces more height and the platform serve more forward move- ment. 3-D biomechanical analysis howev- er shows a clear difference - the pinpoint serve reveals that horizontal displacement occurs before vertical displacement, whereas the platform serve shows vertical before horizontal. Perhaps more interest-

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