The Biomechanics of Tennis Fundamentals

Tennis development is a natural consequence of biomechanics. Biomechanics, stated simply, can be defined as the study of human motion in its physical entirety. It involves efficiency of movement and effectiveness in performing at the highest level, i.e., (by hitting the serve harder, or the approach shot deeper). To understand how your players develop coordinated skills, control, consistency, placement and power, it is important to consider the idea of a linked system of body segments.

This linked system, or KINETIC CHAIN, works in a very systematic fashion with the legs interacting with the ground. The legs take the force and add to it by transferring the force to the hips, from the hips force is transferred to the trunk, from the trunk to the arm, and from the arm to the racket. The summation of this kinetic chain adds up to racket velocity and control. It is vital that teaching professionals understand this kinetic chain so that they can better recognize errors or inefficient movement.

One aspect of inefficient movement is when one of the body parts is left out or the kinetic chain is broken. This means that subsequent body parts must work harder.

For example: When the two handed backhand is hit with no trunk rotation the arms must swing harder, increasing the chance of an error.

A second form of inefficient stroke production occurs when all of the body parts are used but not employed correctly. For example: When hitting the serve the legs may not be utilized completely, resulting in the hips and trunk working harder to create arm and racket speed.

A final aspect of inefficiency takes place when the kinetic chain is not properly synchronized. For example: Some players have a hitch in their service motion. It throws the timing of the body’s kinetic chain out of synch, forcing the arm to swing with excessive action. If the analysis of inefficient movements is followed, it can be of great assistance in locating a problem in stroke production.

There is no perfect way to stroke the ball, but there is one time when the stroke must be perfect -IMPACT. Regardless of grip type, backswing or follow-through, impact must be exact for a player to hit a specific shot. This involves having control over the racket head and swinging the racket with optimal speed.

If impact is viewed as the most important part of a tennis stroke, and it is accepted that there are several backswings and follow-throughs a player could use, then the next step is to identify the other important attributes of sound stroke production. This concept indicates that the speed of the racket is built by summing up the individual speeds of all participating segments. Recent developments in forehand and backhand stroke production have created a needed change in coaching methodology. Particular attention must now be paid to the use of individual segments of the upper arm, forearm and hand.

Following is a biomechanical look at the four basic strokes: Forehand, backhand, serve and volley, as well as footwork.

Forehand
Modern tactics dictate that the forehand be hit with varying degrees of topspin.

The backswing, commencing with flexion of the lower legs and irrespective of style, is characterized by a loop, which has shown to increase racket speed (as opposed to the straight backswing which provides control), and a large rotation of shoulders and trunk.

Forward swing to impact consists of trunk rotation initiating racket movement and is responsible for the forward movement of the hitting arm. Shoulder speed has been shown to contribute 25% of racket speed. The rotation of upper arm, forearm, and hand, account for the remaining 75% of racket speed at impact. Research indicates that the segmental contributions are influenced by grip type and ball level. Forward movement of the upper arm is a key feature of forehand mechanics, producing 30% of the racket speed. The hand plays an integral role in generating racket speed. The follow-through is across the line of the body and a recovery step brings the player into the ready position.

Backhand
The backhand backswing is similar to the forehand with the exception of the loop.

Forward swing to impact requires more trunk rotation of the hitting shoulder. Wrist extension is also a feature of the one-handed backhand of advanced players. Like the forehand, racket speed at impact is derived from a sequencing of trunk and shoulder rotation as well as arm and hand extension.

The backhand underspin has an impact point that occurs closer to the front foot and closer to the body. At impact the racket shoulder moves more toward the net than the topspin stroke.

The two-handed backhand is a three-segment sequence (hips and trunk / upper arms and hands) as opposed to the five-segment sequence of one handed backhands (hips, trunk, upper arm, forearm and hand). All things being equal, the kinetic chain is virtually the same for both types of backhands and should be observed as such.

Serve

The serve is the most strenuous stroke in tennis and deserves critical analysis.

The toss should be positioned in front and slightly to the left of the front foot, and should be impacted at the top of its flight. The swing to impact involves the lower limb drive, together with trunk rotation that produces the shoulder rotation and represents 20 percent of the racket speed. The rotations of the upper arm, forearm and hand account for the remaining 80 percent of racket speed. Hand and wrist flexion (snap) are the last movements and produce 30% of the total racket speed. Therefore the wrist action is an extremely important aspect of service mechanics. Lastly, an up and out hitting action is a key feature of a mature swing.

Volley

For effective volleys, players need to execute a split step in preparation for both volleys.

The backswing requires an increased shoulder rotation on the backhand volley as the racket has to move to the opposite side of the body. During the forward movement of the racket, the left or right foot steps toward the ball. Much of the power in the volleys comes from this step. The upper limb movements are responsible for the majority of racket speed at impact. Lastly, the wrist must be firm (fixed) at impact. The follow-through decelerates immediately after impact as the racket resumes its ready position.

A similar kinetic chain of body segments accompanies the remaining strokes. How well these factors are perceived by the coach will dictate how well the players will respond and initiate the movement needed to perform. Effective analysis of this kinetic chain is an essential ingredient in developing technique in stroke production and in determining the possible cause of an injury.

Footwork
Footwork, or movement, is another important biomechanical attribute. A player’s positioning, and how he or she uses the ground is vital to stroke production. It does not matter how great the stroke is if the player is not in the right place at the right time. From the sports medicine point of view, when a player is out of position, it is difficult to use the body properly in generating force to hit the ball which means that the upper arm must work harder than it should. Spend as much time as your practice time allows developing movement.

An essential ingredient of footwork is to think of the body as a series of small, coiled springs that, when activated, sequentially result in propelling the player in the desired direction. Moving efficiently on a tennis court requires changing direction and speed smoothly and quickly.

Most importantly, a split step must occur just as the opponent is starting the forward swing. This movement primes the body in readiness for an explosive move in any direction. In a split step the feet should be shoulder width apart, with legs flexed, the upper body leaning slightly forward and the weight on the balls of the feet. This ground action force is necessary to decelerate the body from one direction and accelerate the body in another direction.

Additionally, when working on movement there should be a coordinated effort between the legs and the upper body. Coach the player to initiate the first movement with the upper body and not the legs. Using the upper body to lean forward toward the action just before the legs add their contribution is also the same way that players move to ground strokes. This “lean into the ball” tends to level out the racket path, resulting in a longer, more stable hitting zone. This linear motion of the body and racket also encourages more racket force being applied in the intended direction of the shot. In order to move well, players need to efficiently coordinate their upper and lower body to enhance movement and footwork.

Finally, biomechanics involves the design and function of equipment. It is important to examine how the equipment protects the players during performance.

The design of the racket (shape and material) has changed dramatically over the past few years. From the sports medicine point of view it is important to consider how the racket dampens vibration and reduces shock. The stiffer the racket, the more shock will be sent to the arm. The flexible racket has been shown to dampen the shock better. Keep in mind that: the function of the racket is to enhance the function of the player.