Biomechanics of the Tennis Serve

Authors: Costi Tsakiridis & Domagoj Bosnjak

Introduction

The tennis serve has been referred to as the most complex stroke in the game, as well as one of the most useful strokes for winning a match (Kovacs &Ellenbecker, 2011; Martin et al., 2014). These factors make the acquisition of the tennis serve both important and difficult to learn. The reason for the complexity of the serve is due to the combination of joint and limb movements which are required to transfer force from the ground, through the kinetic chain and following out into the ball. Professional tennis players are able to harness the maximal amount of power during a tennis serve through their kinetic chain, effectively using selected muscle groups in a synchronised order(Kovacs &Ellenbecker, 2011). The implementation of the kinetic chain allows greater ball velocity to manifest through generation, summation and transfer of mechanical energy (Martin et al., 2014). The advantage of an athlete who is able to generate larger amounts of velocity behind the ball increases their likelihood of winning the point during their service game. Kovacs and Ellenbecker (2011) break down the serve into an 8-stage model which has 3 distinct phases: preparation, acceleration and follow-through. These 3 distinct phases rely heavily on the knowledge and understanding of the tennis serve’s optimal biomechanics, which in turn produce an improved performance – leading to our question: “What are the optimal biomechanics of the tennis serve?”

Overview of 3-Phase, 8-Stage Model of Tennis Serve:

The 8-stage model is divided into three phases: preparation, acceleration and follow through (Refer Image 1). The 8 stages entail: starting position, release of the ball, loading, cocking, acceleration, contact, deceleration and finish position (Kovacs &Ellenbecker, 2011).

Image 1:

Types of serve:

There are three different types of serves which are commonly used in professional tennis, producing a different outcome which is determined by the spin action of the ball [Refer Image 2] (Abrams et al., 2014). These major types are: the flat serve which requires limited spin; the slice serve which requires side spin, either left or right; and the topspin serve, also referred to as the ‘kick’ serve, which requires topspin, springing upwards into the direction of the receiver (Kovacs &Ellenbecker, 2011). No major differences are seen within the lower body and trunk muscles when producing the different serves, however it is important to note that bilateral differences in muscle activation occur more in the rectus abdominis and external oblique in comparison to the internal oblique and lumbar erector spinae muscles (Kovacs &Ellenbecker, 2011).

Image 2:Types of serve

Stage 1: start

The main goal of the start of a tennis serve is to best align your body in order to utilize the ground reaction forces (GRFs) in the most effective possible manner (Fleisig et al., 2003). The many different styles and approaches that are used in relation to a professional tennis athletes initial stance and positioning is mainly due to personal style and preference, leaving little effect on the overall result of the serve itself. At this stage however, the training of an athlete’s stability and balance during the learning of this stage can be helpful as a stable base of support is an essential part of this stage (Refer Image 3). The use of the muscles within the scapular and shoulder regions is quite low at this stage and only comes into full activation later throughout the serve (Ryu et al., 1988).

Image 3: Stable base of support

Stage 2: release

The release stage starts as soon as the tennis ball has left the non-preferred hand of the athlete (Refer Image 4). The muscles used during the tennis serve and in particular at this stage are very minimal in the left parts of the erector spinae, staying this way for the majority of the serve. The use of the right side of the erector spinae increases steadily from the stat of the tennis serve all the way until the end (Chow et al., 2009). At this stage we see the introduction of the body trying to generate more force summation in order to generate more power out of the tennis serve. The overall combination of different parts of the body producing forces act together in order to produce maximum force which is called force summation (Sandercock& Mass, 2009).

Image 4: Release of Ball

Newton’s third law which is ‘every action has an equal and opposite reaction’ is also incorporated into the stage of the tennis serve (Blazevich, 2013, pp. 44-46). Once the ball is thrown into the air by the non-dominant hand, the same arm is left up in the air in order to help achieve an equal and opposite force with both of the arms. The action from the arm that threw the ball up originally helps balance out the action of the arm which holds the racquet; thismeans that the quicker the arm with the racquet rotates along with the torso, the more power will be generated (Knudson, 2007).

How and where a player tosses the ball for a serve in tennis is a vital part in making sure they can successfully perform a tennis serve. The throw of the ball should be lateral over the head of the server and ball contact should be made at around 100° of arm abduction (Bahamonde, 2000). Improper toss location of the tennis serve and trunk position can have an effect on potential shoulder pain and injuries if these issues are not addressed early.

Stage 3: loading

The loading stage entails positioning segments of the body in particular ways which in turn helps produce potential energy. There are two ways to position the athlete’s feet: the foot-up technique; and the foot-back technique (Refer Image5). Athletes who compose the tennis serve using the foot-up technique use vertical forces; this ultimately allows the athlete to reach greater heights in comparison to other techniques(Kovacs &Ellenbecker, 2011). In this technique, the rear leg provides a push forwards and upwards, whereas the front leg provides the athlete with a strong stable post which allows rotational momentum. It is important to note that this foot-up technique requires athletes to undergo unconventional training of the lower body for the landing of both feet after the service impact (Kovacs &Ellenbecker, 2011).

Image 5: Foot Techniques

On the other hand, the foot-back serving technique requires a greater knee joint extension, which in turn requires lower body training similar to above. Putting this into comparison, the optimal foot-up technique requires a knee extension of 54.1° ± 11.7° and the optimal foot-back technique requires the knee extension of 65.5° ± 12.6° (Kovacs &Ellenbecker, 2011). The advantage of using the foot-back technique is that it allows athletes to produce a wider base of support which in turn permits greater squat depth.

According to Kovacs &Ellenbecker (2011), the velocity of a serve has a correlation with greater muscle force during this third stage, the loading stage. Additionally, the efficiency of a server has a correlation with the internal rotation of the arm which holds the racquet. Although the two foot techniques will impact the outcome of stability and height of the loading stage, it is important to note that the velocity of the ball is not affected through different foot techniques. The lateral rear tilt of the shoulder and pelvis at the end of the loading phase enables the development of angular momentum through the lateral trunk flexion and is an important aspect of all powerful servers [Refer Image 6] (Kovacs &Ellenbecker, 2011).

Image 6: Lateral rear tilt and angles

Stage 4: cocking

The fourth phase of the tennis serve, the cocking position (Refer Image 7) relies heavily on efficiently moving through the loading stage (previous stage). Efficiency is produced through the dominant arm when it comes to driving the racquet down while the back of the torso increases the trajectory of the racquet to the ball. The benefit of this position is the fact that it does not need the optimal range of motion, stabilization, positioning throughout the shoulder region, however despite this, the position still allows for greater energy potential (Reid et all., 2008).

Image 7: Cocking and joint angles

During the late preparation stage there are high internal eccentric rotator loads which are being applied (backswing), which later change into stage 5 which is the acceleration phase before the impact with the ball. When the leg drive is used effectively it forces the racquet in a downwardsdirection away from the back of the athlete. This energy is found to help assist in producing racquet velocity throughout the acceleration phase of the tennis serve (Kibler et al., 2007).

Throughout the fourth stage, the cocking position, there is a rise in the vertical ground reaction forces, at the same time there is an increase in muscle activation in the following muscles: vastuslateralis; gastrocnemius; and the vastusmedialis (Chow et al., 2009). The maximum external shoulder rotation is achieved at 0.090 ± 0.014 seconds prior to contacting the tennis ball within professional tennis athletes. At this stage the leg drive is near complete. During the time of the maximum external rotation, the shoulder is abducted at 101º ± 13º, abducted horizontally 7º ± 13º, and rotated externally 172º ± 12º. The elbow at this moment is flexed 104º ± 12º, whilst the wrist is extended at 66º ± 19º (Refer Image 7). The result of this is in a tight and parallel position in between the trunk and the racquet. The motions which are used during this type of degree of external rotation are the trunk extension motion, the scapulothoracic motion and the glenohumeral motion. There is a similarity in the range of a professional athlete who plays baseball as to that of a professional tennis player when it comes to the magnitude of external rotation; in between 178º-175º (Elliot, 2006).

When there is a continued repetition of the external rotation throughout a tennis serve, it becomes possible that it can lead to a greater external shoulder rotation on the dominant arm whilst at the expense of the internal rotation. However,this rise in the external rotation does not match that of the dominant armof a baseball pitcher who plays at a professional level. When there is a loss of 10º to 15º, both the total rotation and internal rotation generally occur at 90º in the shoulder when abducted (Konda et al., 2010). The posterior shoulder stretches in order to counter the internal rotation losses in wise tennis players.

At the stage of cocking, additional loads on the shoulders whenin an abducted and externally rotated position can possibly lead to injuries. The activity of the muscles is between moderate and high at this stage of the tennis serve. The percentages of use in each of these muscles are as follows: serratus anterior (70%); biceps brachii (39%);subscapularis (25%); infraspinatus (41%); and supraspinatus (53%) (Kibler et al., 2007). These muscles are working at this level in order to help provide stabilisation. The moderate to high levels of muscle use throughout this stage highlights an importance of the posterior and anterior rotator cuff and scapular in order to properly execute the cocking stage of the tennis serve.

There is a large dependence on the glenohumeral position throughout this stage. In order for the coronal plane and the glenohumeral plane to be anterior to each other, 7º of horizontal adduction from the coronal plane must take place. The infraspinatus/supraspinatus and the glenoid have an increase in the amount of contact pressure between each other with the abducted shoulder which is externally rotated (Knudson, 2007). There is a high risk factor again with injures when it comes to the hyper abduction positioning with the throwing shoulder. When the tossing arm is dropped early as well as an early trunk and hip rotation forward, it is possible that there can be exaggerated horizontal abduction, which can otherwise be known as arm lag – this can place extra loading on the anterior capsular structures and can place the shoulder to posterior impingement.

During the action of maximal external rotation there are angles of 83º and 101º which are quite high and can possibly risk impingement. When there is lower internal and external rotation ratios produced by professional tennis players, it indicates that they have developed selective use of internal rotators relevant to the external rotators (Reid et al., 2008).

Stage 5 - acceleration

Stage 5 of the tennis serve is called the acceleration phase. This stage is greatly impacted by what has been happening on the previous 4 stages and how efficiently they are performed. Elite tennis players and servers have a much faster acceleration phase than that of a beginner; this is thanks to much more vigorous knee extension throughout the phases 3-6. Elite tennis players move throughout the maximum glenohumeral joint external rotation through to the contact of the ball in less than 1/100 of a second (Ryu et al., 1999).

Throughout this stage the muscles in which there is high muscle activity are: subscapularis (113%); latissimus dorsi (57%); pectoralis major (115%); and serratus anterior (74%) (Refer Image 8). Many of these figures correspond with the muscle use of that within the acceleration phase of a throw (Kibler et al., 2007). The deltoid, triceps, trapezius, and pectoralis major are all active throughout the stage of acceleration within the acceleration phase of both the tennis serve and the throwing motion.

Image 8: Muscle groups used

There are two factors which directly affect power production throughout this stage. These are both neuromuscular coordination and strength. 1.68 to 2.12 times a person’s body weight is approximately that of what is produced through vertical force production throughout the serve (Kovacs&Ellenbecker, 2011).

It is close the end of the fifth stage of the tennis serve in which peak values are reached for the gastrocnemius, vastusmedialis and the vastuslateralus. The acceleration phase is the phase in which the trunk muscles are getting used the most (Girard et al., 2005). The highest amount of kinetic energy is produced throughout this stage, making it a vital contributor to the power production of the serve.

In order to produce as much acceleration as possible for the tennis serve it is essential that as well as producing power from the trunk muscles, we need to produce acceleration of the racquet before the ball. This is done by a quick lumbar spine rotation reversal for a server which serves with his right hand through hyperextension and right lateral flexion to flexion and left lateral flexion. The corkscrew, as this movement is also known as, allows the transfer of the torque through to the muscle segments (Kovacs&Ellenbecker, 2011). Through constant trunk hyperextensions the serve may cause an athlete stress on the lumbar spine.

Stage 6 - contact

At the contact of the tennis ball, the trunk sits at an average tilt of around about 48º; abduction is at 101º; and the leading knee, elbow and wrist are flexed slightly inward in professional tennis athletes. The average shoulder abduction for elite tennis players before contact of the ball is around 100º, which again is quite similar to that of a baseball pitcher who need 100º ± 10º angle in order to produce maximum ball velocity as well as having as little as possible loading on the joints of the shoulders. Optimal contact for a tennis player would therefore be at around 100º ±15º. Elite tennis players at optimal performance are able to produce racquet velocities of around 38 – 47 m/sec [Refer Image 9] (Elliot, 2005).

Image 9: Contact point

At the contact of the ball, the ball velocity is produced by flexion of the wrist and internal shoulder rotation. Wrist flexion (15º ±8º), front knee flexion (24º ± 14º), and elbow flexion (20º ± 4º) are very small at contact. Trunk is generally tilted 48º ± 7º above horizontal for professional tennis players (Kovacs&Ellenbecker, 2011).

When the left lateral flexion angle is greater it shows us that more height will be achieved throughout the tennis serve. The left rectus abdomis is also greater in its activity levels at this stage (Kovacs&Ellenbecker, 2011). Tennis players with that of a higher skill are more likely to be subjected to higher asymmetric loads on their lumbar spines as a result of higher lateral flexion.

Stage 7 - deceleration stage

Stage 7, the follow through stage, is the phase which is considered to be the most violent and vigorous throughout the whole tennis serve. It requires the athlete to decelerate eccentric loads in both the lower and upper body. Forearm pronation and glenohumeral internal rotation are continued at this stage and through to after the contact of the ball in the serve through to the slowing down after contact has been made (Antunez et al., 2012). This type of motion has been named the long axis rotation.

It is possible that the deceleration force activity between both the arm and the trunk of the athlete during the stage of deceleration can be as high as levels of 300 N m. The benefit of this force is that it is able to stabilise one’s body weight up to 0.5 to 0.75 against any sort of distraction forces (Martin et al., 2014).

The muscles which are being used moderately-highly throughout this stage are: the dorsi musculature; deltoid; biceps brachii; serratus anterior; and the posterior rotator cuff. 30% - 35% is the percentage range of the posterior cuff activation because the humerus is slowed down after the point of contact. In order to offset any distraction force and keep glenohumeral congruity [Refer Image 10] (Kovacs&Ellenbecker, 2011).

Image 10: Muscle Groups used

Throughout the whole action of the tennis serve, the left internal oblique is more active than the right internal oblique apart from the deceleration stage (Abrams et al., 2014). The right erector spine becomes very active throughout this part of the serve as it helps to stabilize the trunk when the posture is unbalanced, which is the case in the deceleration stage.

Stage 8 – follow through

The final stage of the tennis serve finishes on the landing of the lower body (Refer Image 11). This motion generates eccentric forces. The front foot is used as a large horizontal breaking force using the foot up technique, but because the centre of the mass is moved to a forward position, it could possibly hinder players on their serve (Reid et al., 2008).

Image 11: Follow through and landing

There are very little alterations between the serve kinematics between female and male athletes who are professional at tennis; therefore different genders do not need to learn different mechanics (Kovacs&Ellenbecker, 2011).

Torque & Levers in relation to the tennis serve

Torque and levers both have some specific effects which can be intertwined with each other. When it comes to the amount of power which is released from the tennis serve, both the levers and torque share equal importance (Bahamonde, 2000). The force in which rotation is allowed is known as the torque. This is able to be presented around the object axis. The way in which this is related to the tennis serve is through movements from body parts such as the legs, arms and hips of the athlete. These types of movements rotate in a particular way. The main significance of torque within the tennis serve is throughout the swing of the serve (Elliott, 2006).

In order to increase the amount of torque we need to increase the distance of the muscle to the joint. This is shown through the extension of the arm from the action of the tennis serve. Extending the arm more is valuable as it gives players more acceleration on the head of the racquet and a greater power on the ball (Fleisig et al., 2003). This is due to us extending the length of the lever and the movement arm as mentioned earlier.

Kinetic Chain

The Kinetic chain is a process where the athlete should be required to understand a step by step list of instructions, understanding which mechanisms of their body will be in use throughout the performance of complex tasks required in sports skills; in this case, the tennis serve. It is a routine of movement sequences in which different parts of the body wither activates, mobilize or stabilize in order to generate force, motion production, and protection of muscle tissue damage and increased strain on the athlete’s body during activity. If throughout the kinetic chain we are to produce an increased power throughout a certain body part, the object will then have a higher velocity and will have a greater overall kinetic energy (Blazevich, 2013, pp. 102-103).

The main 3 purposes of the kinetic chain are;

Efficiently generating and transferring both force and kinetic energy to distal segment in order to proficiently move an object. This is accomplished by using the principle of ‘summation of speed’ where both the force and velocity which are produced throughout each different segment are supported and increased by the actions within the proximal segments. A good example of this is the cracking of a whip (Cordo&Nashner, 2008).
The position and the stabilization of the different segments of the body in order to help absorb and control the forces which have been developed at the joint. This is accomplished by making postural movements which are anticipatory which are mixed with the athletic activity pattern in order to maintain a more stable base for activity (Elliot, 2006).
Stabilizing the posture of the body in order to counteract destabilizing effects and any eccentric loads of any athletic movements. This is accomplished by assimilating proximal and distal muscle activation on order to spread the load throughout the whole extremity, controlling eccentric and tension loads and putting joints in a position in which they will be most stable in either the lower or the upper extremity (Zattara et al., 2010) .

Kinetic chain in relation to the tennis serve;

Within the serve in tennis there are many different components. The components include; spin and placement and velocity, these all have relations to effectively developing an action throughout the kinetic chain (Nicholls, 2003). The intended result of this is having the optimal placement of the racquet to be at the maximum velocity with the wanted trajectory to be ‘up and through’ the tennis ball. In order for this to happen, the body of the athlete must first go ‘down and back’ in to a kinematic position of loading and a kinetic position of cocking, the arms are to next move forward at a rapid pace, and through the ball.

There are two different ways in which you can perform this type of skill: the first is by pushing both the arm and the body through the ball impact; the second contains pulling it through. Both of these types of kinetic patterns have differences which are observable to the naked eye in how the segments are moved and activated. They also differ in the way that they both have different biomechanical results and physiological stresses for the performance of the serve (Putnam 1993).

It is known that within tennis, very rarely do you see two players serve the ball in the exact same way. However the guidelines for every athlete’s tennis serve remain the same and this is all based on the principles of the kinetic chain (Refer Image 12).

Image 12: Kinetic Chain of Tennis Serve

Biomechanical teaching cues (right handed tennis player)

1. Before doing anything in the serve you must ensure that you are standing behind the baseline, on the opposite side from where you will be serving from. Stand facing sideways, and point your left foot to face the other post of the net, ensuring that your right is parallel to the court.

2. Point your right shoulder towards the direction of the service box where you are serving.

3. Align the trunk of the body in order to try and utilise the ground below in order to generate power/force throughout the motion of the serve.

4. Throw the ball up in the air with your opposite hand to where the racquet is (your left), and keep the arm in the air in order to help generate power on the serve.

5. Ball toss must also ensure that it goes high and in front of you a little, in order to help generate momentum.

6. Bring the head of the racquet up behind you and bend your elbow behind your head, as emulating the position of as if you were to scratch your back with the racquet. Bending knees will help to move the head of the racquet in an upwards motion; it will again generate greater power.

7. Use either the foot-up technique, bringing your back foot closer to the front foot or the foot-back technique, which involves keeping your foot further back from your front foot.

8. Tilt right shoulder back and bend knees before jumping for contact of the ball to help generate power.

9. Jump in the air towards the ball, abducting shoulders and elbow flexion of around 115º as well as wrist extension of 77º.

10. Strike the ball in the sweet spot (the middle) of the tennis racquet. Bring the racquet head above in order to hit the ball with as much power and speed as possible all whilst keeping control on the tennis serve. Your shoulders will rotate similarly to how they would if they were throwing a ball. It is important to be fluid with your shot and not just try hitting the ball as hard as you can.

11. To get the most out of your shots, you should hit the ball at the point in which it is the highest.

12. Follow through on the tennis serve by singing the racquet down near the bottom of your opposite foot.

13. Ensure stable landing. The follow-through of the tennis serve should cause you to step in towards the court. Ensure that you are prepared for the return.

Breakdown of Roger Federer’s tennis serve (Refer Image 13).

Image 13: Federer Serving Motion Shots

Roger Federer has one of the most smooth and effortless tennis serves in the world and he has one of the most underrated serves going around. Although Federer does not reach quite the speeds of some of the other professional tennis players, he is much better in many of the other aspects of the serve. Federer’s serve is a great model for young people to try and emulate as it is a simpler, more classical and has less extreme elements than other professional tennis athletes (Shiras, 2014). Below is a rundown of the tennis legend’s serving technique in accordance to the biomechanical teaching cues above.

1.Federer never rushes his technique; he starts with his hands together with his racquet drawn back and down whilst his left hand drops.

2.Federer tends to let his racquet trial down instead of tossing and lifting the racquet at the same speed. He shifts his energy in to his quadriceps and bends his legs throughout this motion.

3.His wrist is loose and his arm is bent as the ball goes up. His ball toss is slightly in front of him and fairly high in the air. He turns his shoulder in such a way that the opponent will have trouble trying to predict what type of a serve he is going to produce.

4.This is Federer’s famous trophy position as it is now known as. He is basically underneath the ball with his chest pointing towards the sky looking at it. His racquet is about to drop down and is in mid loop. At this moment he is able to spring upward on towards the ball, putting all of his available energy at the ball.

5.This is the point where his racquet is at the lowest point. However, at this moment his torso, legs and chest are all on the way up. His racquet at this stage still hasn’t moved up. The purpose of his movement at this stage of the skill is to make the conditions perfect for the racquet to be able to spring up as fast as possible.

6.At this stage his arm is completely extended. There is a small arch to his body, but this is due to him moving up and out. As his racquet is so high it gives him the chance to hit the ball into his opposition’s service box from an improved angle. His head and eyes stay up and focused at the point of contact even after the serve has been played.

7.His head is still up even though the swing is just about in completion. His wrist has rotated onto the ball whilst his momentum has moved onto the court. His left arm is kept close to his body in order to maintain balance. Although this part of the serve is meant to be the most violent looking part of the swing, Roger makes it look effortless and smooth.

8.The landing of Roger is just on the inside of the baseline. His right foot moves back which helps him balance. His knees are also bent apart at this stage to help aid the landing. He is not looking towards the court and is positioned in a way in which he could easily move to the left and right of the court to return the next shot which comes his way (Shiras, 2014).

The Answer

The biomechanical principles which are required to achieve the optimum tennis serve can be easily split into 3 phases which are the further split into 8 stages. A confident and well established base of support is crucial to the commencement of the first stage. Throughout the next stage, force summation is used in order to produce the maximum possible momentum using a combination of different body parts. Newton’s third law now manifests itself during the ball toss as the player swings for the ball, utilising their trunk in a twist action, bringing the non-dominant arm down. Taking advantage of the knowledge surrounding the kinetic chain, a player will be able to understand how they can create an elastic energy which amplifies the speed of the serve. This speed is also heavily influenced by the proper execution of the cocking stage. This entails the player’s elbow flexion to average 115°, wrist extension to average 77° and shoulder abduction to average 113°. The contact point is equally as important. Contact should be made in the ‘sweet spot’ of the racquet while at the same time the trunk tilt is at an average of 48° and abduction at an average of 101°. The deceleration and follow through stage should be completed accordingly and comfortably. Many injuries occur due to poor technique and heavy landing positions so it is important to generate confidence in these stages. Following the teaching cue stages above which have additionally been connected to Roger Federer’s serve, players should produce the optimum tennis serve.

How else can we use this information?

Connections to baseball techniques have been made through the investigation. For example, there is a similarity in the range of a professional athlete who plays baseball as to that of a professional tennis player when it comes to the magnitude of external rotation; in between 178º-175º (Elliot, 2006). Followed by the fact that the average shoulder abduction for elite tennis players before contact of the ball is around 100º, which again is quite similar to that of a baseball pitcher who need 100º ± 10º angle in order to produce maximum ball velocity as well as having as little as possible loading on the joints of the shoulders.

References

Abrams, G. D., Harris, A. H., Andriacchi, T. P., &Safran, M. R. (2014). Biomechanical analysis of three tennis serve types using a markerlesssystem.British journal of sports medicine, 48(4), 339-342.

Antúnez, R., Hernández, F., García, J., Vaíllo, R., & Arroyo, J. (2012). Relationship between motor variability, accuracy, and ball speed in the tennis serve. Journal of Human Kinetics, 33, 45-53.

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.

Chow JW, Park S, Tillman MD. (2009). Lower trunk kinematics and muscle activity during different types of tennis serves. Sports Med Arthroscopy Rehabilitation Therapy Technol. 1(24).

Cordo PJ, Nashner LM (2008) Properties of postural adjustments associated with rapid arm movements. J Neurophysiol 1982; 47: 287-308.

Elliott, B. (2006). Biomechanics and tennis. British Journal of Sports Medicine, 40(5), 392-396.

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.

Fleisig, G., Nicholls, R., &Escamilia, R. (2003). Technique effects on upper limb loading in the tennis serve. Journal of Science and Medicine in Sport, 6(1), 76-87.

Girard, Olivier P, Micallef, J. P., & Millet, G. P. (2005). Lower-limb activity during the power serve in tennis: effects of performance level. Med Sci Sports Exerc, 37(6), 1021-1029.

Kibler, W. B., Chandler, T. J., Shapiro, R., &Conuel, M. (2007). Muscle activation in coupled scapulohumeral motions in the high performance tennis serve. British journal of sports medicine, 41(11), 745-749.

Knudson, D. (2007). Qualitative biomechanical principles for application in coaching. Sports Biomechanics, 6(1), 109-118.

Konda, S., Yanai, T., & Sakurai, S. (2010). Scapular rotation to attain the peak shoulder external rotation in tennis serve. Medicine and science in sports and exercise, 42(9), 1745-1753.

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., Bideau, B., Bideau, N., Nicolas, G., Delamarche, P., &Kulpa, R. (2014). Energy Flow Analysis During the Tennis Serve Comparison Between Injured and Noninjured Tennis Players. The American journal of sports medicine, 0363546514547173.

Martin, C., Bideau, B., Ropars, M., Delamarche, P., &Kulpa, R. (2014). Upper limb joint kinetic analysis during tennis serve: Assessment of competitive level on efficiency and injury risks. Scandinavian journal of medicine & science in sports, 24(4), 700-707.

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.

Putnam, C. A. (1993). Sequential motions of body segments in striking and throwing skills: descriptions and explanations. Journal of biomechanics, 26, 125-135.

Reid, M., Elliott, B., & Alderson, J. (2008). Lower-limb coordination and shoulder joint mechanics in the tennis serve. Medicine+ Science in Sports+ Exercise, 40(2), 308.

Ryu, R. K., McCormick, J., Jobe, F. W., Moynes, D. R., &Antonelli, D. J. (1999). An electromyographic analysis of shoulder function in tennis players.The American journal of sports medicine, 16(5), 481-485.

Sandercock, T., & Maas, H. (2009). Force summation between muscles: are muscles independent actuators?.Medicine+ Science in Sports+ Exercise, 41(1), 184.

Shiras, L. (2014). Great Shots: Roger Federer Serve, www.tennis.com, http://www.tennis.com/your-game/2014/01/great-shots-roger-federers-serve

Zattara M, Bouisset S. Posturo (2010) kinetic organization during the early phase of voluntary upper limb movement. J NeurolNeurosurg Psychiatry 1988; 51: 956-965.

Appendix 1: Images

Image 1 – 3-Phase, 8-Stage Model of Tennis Serve.

Information used in custom diagram taken from Kovacs &Ellenbecker (2011)

Image 2 – Types of serve

Image taken from Kovacs &Ellenbecker (2011)

Image 3 – Stable base of support