The Optimum Biomechanical Technique to Maximise Speed and Accuracy of the Tennis Serve

MAJOR QUESTION

The tennis serve, and in particular the first serve, is used as an offensive weapon to give the server an advantage towards winning the point. Highly effective servers of the game are able to consistently deliver the ball at high speeds and with precise accuracy. The serve does contain a major degree of tactics and skill acquisition, however this blog will concentrate on optimising the biomechanical principles embedded in the serve to maximise both speed and accuracy. To do so, I will break the serve down into what I believe is the four most crucial movement phases of the serve which include: preparation phase, wind-up phase, force production phase, and the ball contact phase.

THE ANSWER

Preparation Phase

During the preparation phase of the tennis serve, the biomechanics play a minor role in the success of the serve, with psychological factors such as focus, arousal level, tactical awareness and visualisation playing a more significant role (Guillot, Genevois, Desliens, Saieb & Rogowski, 2012). The biomechanical influence within the preparation phase is based around getting the body into the optimum starting positions to begin the movements that occur during the wind-up and force production phases of the movement. In order to promote the greatest degree of torso rotation to produce greater energy through the kinetic chain, the majority of elite tennis players adopt a back foot position that is largely parallel to the baseline (Blazevich, 2013). This concept is illustrated in Figure 1 with Novak Djokovic and Roger Federer, using a yellow line to underline the parallel back foot. The front foot is generally positioned up to the baseline on varying diagonal angle; this varies between individual techniques and even between the types of serve (Reid, Whiteside & Elliott, 2011). The feet are separated in order to create a broad base of support, which the player’s centre of gravity is positioned within during the preparation phase. It is also essential for the player to establish elasticity of muscles and joints in preparation for the kinetic chain during the force production phase (Blazevich, 2013).

Wind-Up Phase

As highlighted in Figure 2, Andy Roddick uses Newton’s third law of motion in order to generate the starting power and momentum for his first serve. Newton 3^rd law states: “For every action, there is an equal and opposite reaction” (Blazevich, 2013, p. 45). Showed by red arrows, the initial action is a force directed vertically towards the court generated primarily by the flexion of the knees, before the forceful contraction of the lower limb muscles. In turn, this action creates a reaction of an equal force in the opposite vertical direction, illustrated by yellow arrows. The upwards reaction not only acts as the start of Roddick’s force production and kinetic chain, but the more height gained from the ground creates a higher point of contact (Fleisig, Nicholls, Elliott & Escamilla, 2003), which will be further analysed within the ball contact phase.

Another essential part of the wind-up phase is the ball toss and the location of the ball in relation to the player at the point of contact. In order to achieve both high speed and accuracy, it is essential to establish consistency with the ball toss to allow for repetition with the serving routine (Bahamonde, 2000). Figure 3 highlights the ball toss position of elite performer Roger Federer. By tossing the ball slightly into the court, the athlete is encouraged to jump into the court. This forward movement moves the athlete’s centre of gravity (red line) over the forward edge of their base of support (yellow arrow), resulting in forward momentum (blue arrow) being generated and a greater velocity being placed upon the ball (Blazevich, 2013). However, the position of the ball toss must not travel too far forward in hope of generating increasing speed, as the height of release is compromised, hence impacting upon accuracy as the margin for error of the angle of release is reduced (Whiteside, Elliott, Lay & Reid, 2013), which is discussed further in the ball contact phase.

Force Production Phase

The kinetic chain involves a rapid sequence of body segment rotations and force contributions that generate elastic energy through angular velocity (Blazevich, 2013). A biomechanical analysis study by Fleisig, Nicholls, Elliott & Escamilla (2003) of 20 world-class tennis players, both male and female, supported the principle of kinetic energy and angular velocity playing a major role towards increasing serving velocity.

“Based upon the mean values for this group, the elbow flexed to 104° and the upper arm rotated into 172° of shoulder external rotation as the front knee extended. From this cocked position, there was a rapid sequence of segment rotations. The order of maximum angular velocities was trunk tilt (280°/s), upper torso rotation (870°/s), pelvis rotation (440°/s), elbow extension (1510°/s), wrist flexion (1950°/s), and shoulder internal rotation. Shoulder internal rotation was greater for males (2420°/s) than females (1370°/s), which may be related to the faster ball velocity produced by the males (50.8 m/s) than the females (41.5 m/s)” (Fleisig, Nicholls, Elliott & Escamilla, 2003, p. 51).

Therefore, this quote highlights the importance of maximising the degree of angular velocities within all contributing body joints. This contribution of many interrelating movements is an example of a throw-like sequence. A throw-like pattern uses the sequential summation of individual forces, illustrated in Figure 4, to transfer a greater amount of energy than a push-like pattern. This is due to a throw-like pattern having an increased kinetic chain, hence the force summation occurs for a greater duration, multiplying the energy as it moves through the kinetic chain (Blazevich, 2013).

With the legs, torso, shoulder, and striking arm working together to produce a summation of forces, the critical role of the non-striking arm and shoulder needs to be recognised. After delivering the ball toss strategically with a straight arm in order to produce more consistent accuracy (Martin, Kulpa, Delamarche & Bideau, 2013), the non-striking arm must perform a flexion at the elbow. This movement of tucking the arm into the body aims to conserve angular momentum and reduce the body’s moments of inertia (Bahamonde, 2000). By tucking in and pulling the non-striking arm downward, a ‘windmill’ effect occurs to assist the force generated by the striking arm. Hence, a conservation of the body’s angular momentum and reduction in their moment of inertia results in a greater overall energy being transferred onto the next phase of ball contact (Blazevich, 2013).

Ball Contact Phase

The point of contact is the most critical part of the movement. All of the kinetic energy produced, angular momentum conserved and forward momentum gained will count for nothing if the ball contact phase is not effective. The success of this phase depends largely of developing hand-eye coordination through a sound routine, however, there are many biomechanical principles embedded within.

Maximising the height of release of the serve is essential towards allowing for a greater margin for error in regard to distance above the net and area of the service box for the ball to land in (Kovacs & Ellenbecker, 2011). This concept is highlighted in Figure 5 where it shows the yellow dotted ball path coming from a greater height, giving it a ‘safer’ clearance height above the net and landing into the service box with ample margin for error. Contrastingly, the green dotted ball path comes from a significantly lower height of release, minimising the clearance height above the net and the area for the ball to land within the service box. Hence, contacting the ball from a greater height allows the player to hit the ball flatter (no spin) to generate a greater speed than a topspin serve.

In Figure 6, I have constructed a graph illustrating the correlation between player height and the speed of their fastest recorded serve. Whilst the correlation is not extremely strong, there is still a moderate linear relationship evident between player height and service speed. Most players, as previously highlighted in Figure 1 with Andy Roddick, will use strength from their lower limbs to ‘jump’ as they serve in order to gain a greater height of release, and therefore an increased ability to hit the ball flatter.

The angle of release is directly linked to the height of release, with a greater height of release allowing for a greater range in the angle of release. The angle of release however is more responsible for the accuracy of the serve (Whiteside, Elliott, Lay & Reid, 2013). In reference to the parallel at the point of contact, a greater angle of release (more downward angle) will generally be hit flatter, with increased velocity, but will have a reduced margin for error. Whilst a smaller angle of release (less downward angle) must be hit at a lower velocity, and/or with a greater amount of topspin in order to allow for the ball to ‘dip’ down into the service box (Blazevich, 2013). This concept was demonstrated through an experiment I conducted with a skilled tennis player using the Speed Clock application on an iPhone.

Notice in Figure 7 that the ‘flatter’ serve had an angle of release of 9.4° and resulted in a faster ball velocity (180km/hr). In Figure 8, the ‘topspin’ serve recorded an angle of release of 5.9° and a slower ball velocity (170km/hr). For the serve in Figure 8, the athlete had to impart a greater amount of topspin on the ball in order to ‘dip’ the ball into the court in comparison to the ‘flatter; serve in Figure 7, hence the difference in ball velocity.

The skill of using topspin to ‘dip’ the ball into the court whilst allowing for a greater clearance over the net is based on a biomechanical principle called the Magnus effect (Blazevich, 2013). Figure 9 illustrates that by hitting the ball with an angled racquet, facing upward or downward, creates a ‘lift force’ that will manipulate the flight path of the ball. By hitting down (slicing) on the ball, the upper half of the ball possesses a greater drag force than the lower half, causing the ball to spin backwards and ‘float’ through the air before bouncing low. Contrastingly, hitting over the ball creates a lift force above the ball, with the lower half possessing a greater drag force, causing the ball to ‘dip’ down into the court before bouncing high (Sakurai, Reid & Elliott, 2013).

HOW ELSE CAN WE USE THIS INFORMATION?

By developing the movement of a tennis serve to optimise the biomechanical principles, there is a direct relationship towards improved biomechanical outcomes for other sporting examples such as bowling in cricket, serving in volleyball and throwing in javelin just name a few. This is because all of these movements resemble a throw-like pattern; hence there is a summation of individual segment forces that combine to produce a high velocity at release. Understanding the advantages of biomechanical principles allows for elite performers to critique and analyse their own performance, to continue to evolve and improve their individual technique. As a future educator, I will consciously aim to improve biomechanical deficiencies, through strategic coaching as well as educating every student on the importance of understanding biomechanical principles within Physical Education.

REFERENCES

Bahamonde, R. E. (2000). Changes in angular momentum during the tennis serve. Journal of sports sciences, 18(8), 579-592.

Blazevich, A. J. (2013). Sports biomechanics: the basics: optimising human performance. A&C Black.

Fleisig, G., Nicholls, R., Elliott, B., & Escamilla, R. (2003). Tennis: Kinematics used by world class tennis players to produce high‐velocity serves. Sports Biomechanics, 2(1), 51-64.

Guillot, A., Genevois, C., Desliens, S., Saieb, S., & Rogowski, I. (2012). Motor imagery and ‘placebo-racket effects’ in tennis serve performance. Psychology of Sport and Exercise, 13(5), 533-540.

Kovacs, M., & Ellenbecker, T. (2011). An 8-stage model for evaluating the tennis serve implications for performance enhancement and injury prevention. Sports Health: A Multidisciplinary Approach, 3(6), 504-513.

Martin, C., Kulpa, R., Delamarche, P., & Bideau, B. (2013). Professional tennis players' serve: correlation between segmental angular momentums and ball velocity. Sports Biomechanics, 12(1), 2-14.

Reid, M., Whiteside, D., & Elliott, B. (2011). Serving to different locations: set-up, toss, and racket kinematics of the professional tennis serve. Sports Biomechanics, 10(4), 407-414.

Sakurai, S., Reid, M., & Elliott, B. (2013). Ball spin in the tennis serve: spin rate and axis of rotation. Sports Biomechanics, 12(1), 23-29.

Whiteside, D., Elliott, B., Lay, B., & Reid, M. (2013). A kinematic comparison of successful and unsuccessful tennis serves across the elite development pathway. Human movement science, 32(4), 822-835.