VOLLEYBALL: JUMP SERVE

The Question: 

What are the biomechanical principals of a volleyball jump serve and how can these be optimised?

The volleyball serve is used to commence the game by delivering the ball across the net to the opposite side of the court. The ideal outcome of the serve is to execute an un-returnable serve. Although this is optimal, it cannot always be achieved. A jump serve, nevertheless can increase the difficulty for the opposing team to make an effective attack, as this style is displayed to create the highest ball speeds in volleyball (Mackenzie, Kortegaard, LeVangie & Barro, 2012). To do this, the server must strike the ball with maximum force at the peak of the jump. But how can this be achieved?

To execute the volleyball jump serve, a player needs to combine a variety of skills for the biomechanically complex task. The sequence comprises of a number of components which intertwine for effective execution. The components include; ball release, run up, take off and jump, shoulder rotation, ball contact, follow through and landing. To optimally execute the jump serve the phases outlined in Figure 1 need to be combined fluently to increase the effect of the summation of forces. The qualitative and quantitative findings will be discussed in regards to the biomechanical principles such as the effects of the; kinetic chain, torque, centre of mass, inertia, conservation of angular momentum, Newtons laws of motion, push and throw like movement patterns, coefficient of restitution, velocity, acceleration and projectile motion. These biomechanical principals will be highlighted in order to discover how the body can be manipulated to shape an optimal performance and attain desired outcomes.

*The following biomechanical analysis describes the jump serve for a right hand server. The opposite body positions would need to be adopted for a left hand server.

Figure 1: The technical phases of the volleyball jump serve.

(Follow through and landing not included)

Conceptualising the answer:

Ready position and Ball Toss 

-Context

The ball toss can be performed using either arm, however a study by Tant and Witte (1991) determined that using the serving hand to toss increased the hitting arm and trunks range of motion in the toss. If the server throws with the non- serving arm an initial step from the left foot is produced, compromising horizontal velocity, as there is on average only two steps in the run up. Therefore, for this analysis the serving arm will be utilised as the throwing arm for the optimal biomechanics. 

-Court Positioning

Figure 2: Aiming for the ball to land in line with the serving line of the court. Starting back from the serving line 3 to 4 steps. (Image from: https://www.youtube.com/watch?v=qRE1PCvb0-0) (Author generated)

In the jump serve, the entirety of the serve is determined by the ball toss. The aim of the ball toss is toaccurately release the ball to occupy enough force and velocity to enable the server to complete 3 to 4 steps to follow on for the jump phase.  In this sense, the toss is performed 3 to 4 steps behind the serving line of the volleyball court as shown in Figure 2.

-Serving arm coupling with right foot

The objective of an accurate toss is an upward arm swing where the summation of the whole arm is in a supination position, which acts as a foundation for the volleyball to sit on the palm of the hand. Taken together, as the right foot is placed in front of the body with a large step, the ball is carried to a parallel position just above the right shoulder through a slight rotation of the shoulder and maintenance of arm extension. The server should keep stability during this period of the step phase, by slightly bending their knees creating a large base of support where their mass and centre of gravity is lowered. At this stage the body begins to gain horizontal velocity as the ball is thrown for the serve and thus the ball is released throughout the forward shift of the body weight and line of gravity over the right foot. At the same time, the height of the ball is further raised through a combination of slight shoulder flexion coupled with elbow flexion. In order to create an optimal toss for the serve, the ball should be released from the palm of the hand above head height at the highest point possible to ensure both horizontal and vertical velocity of the ball. 

-Simultaneous push

The ball toss movement pattern is characterised as a push-like movement pattern as the joints in the kinetic chain of the arm simultaneously move in a single sequence producing higher torques or cumulative forces generated about each joint, producing a greater overall force (Blazevich, 2007). The simultaneous joint rotations subsequently create end points of a chain, which have straight-line movements; this is effective for highly accurate movements.  As the objective of the ball toss is to ensure accuracy, to optimise the throw the player should ensure that the shoulder, elbow and wrist move in a single simultaneous motion, with no abrupt or separate forces. This technique will apply a greater cumulative force and maximise the outcome of the toss.

- High release point

Keeping the hand on the ball through a greater range of motion will generate more accuracy. Starting with the ball at waist height and moving it through to slightly above head height, will enforce greater ball contact. The greater ball contact will therefore influence the direction of the force application over a longer period of time, creating more control over the toss. In addition, these actions produce a longer lever arm and greater mass to create optimum velocity in the hand. In order to further optimise the jump serve, the player should encourage the ball at the end point, the fingers, to roll off with spin (Alexander et al., 2010). This is done by flexing the fingers slightly as the ball is leaving the hand. This spin will increase velocity of the push-like movement, which is characterised by slow movement speeds and will help for the generation of topspin at the contact phase. 

-High projection angle

Figure 3: When the angle of release is greater, a greater vertical velocity is obtained as opposed to greater horizontal velocity of a smaller angle of release. To meet the 4 step mark for the jump of the serve a projection angle of approximately 70˚ will create sufficient vertical velocity to achieve the range. (Author Generated)

Achieving a high and accurate toss will in turn create more time for the server to complete the run up, jump, shoulder rotation and contact phases of the serve and thus will contribute to a more successful serve. The projection speed will determine the height the ball reaches before gravity accelerates the ball back down to earth (Blazevich, 2007). Figure 3 demonstrates the optimum projection angle for a 4-step approach where the horizontal distance the server needs to cover in the run up is not excessive. Therefore, the ball is given a greater vertical projection rather than horizontal projection angle, as well as sufficient speed, to give the server time to perform the approaching techniques. 

Run up/Approach

- Large strides

Figure 4: Larger steps mean that the foot is in contact with the ground for longer periods of time producing greater forces. (Image: MacKenzie et al., 2012)

Once the server has released the ball in front of them, they must run the distance to begin the jump phase behind the service line with as much forward momentum as possible. The run up consists of 3 to 4 steps where the body moves towards the court with increasing speed. During the approach the kinetic energy in the steps are used as a loading mechanism to transfer the multiplication of the kinetic motions to execute a high vertical jump. In this sense, a stopping motion in the transition from the run up phase to the jump phase results in a loss of kinetic energy, creating a smaller amount of potential energy and a smaller jump height (Blazevich, 2012). The optimum run up is demonstrated in Figure 4 whereby the server takes larger steps so their foot lands as far as efficiently possible in front of their torso in order to generate higher forces. Because the legs move at angles, greater angular momentum will be generated and conserved as the joint torque can be produced over a longer period of time. 

- Keeping Low

As a result of taking large strides, during the three-step phase, the centre of mass lowers as the hips, knees and ankles contract. This contraction will develop flexion and therefore stretch the leg muscles moving in to the jump phase where further contraction will be required. This will be an important aspect of the run up as the goal is to transfer the energy from one movement phase to the next fluently to ensure as little energy is lost as possible.

- Accelerate from balls of feet

Although the server will benefit from taking large strides, they will need to ensure that the speed of their run up is not compromised. A faster horizontal velocity of the centre of gravity produced by a more rapid run up will inturn increase the speed of the ball leaving the hand. Therefore the server should accelerate off the balls of their feet so that force application occurs in a backwards direction. Applying a backwards force against the ground will enforce Newtons Third Law where the propulsive force exerts an equal and opposite reaction propelling the athlete forwards. 

-Aligning body with ball

The run up will be dependent on the volleyballs position in the air as a result of the toss. In order to maximise force production, the server needs to make contact behind the ball. If the player is unable to attend to the ball in the right position, they may create opposing forces, which will not enable them to jump as efficiently. Therefore, it is important that the server is ready to adapt to the direction of the ball release by watching the flight path of the ball before taking the first step.

Jump

-Generating power 

Figure 5: The ground exerting an equal and opposite reaction force. During the jump phase of the volleyball serve, the server should apply reaction forces shown in part B, both horizontal and vertical forces to accelerate the player in an upwards and forwards motion. (Blazevich, 2007).

Newton’s third law can be applied to the initial stage of the jump sequence in which the server generates force by planting both feet on the ground after the run up. The law states that “For every action there is an equal and opposite reaction” (Blazevich, 2007, p. 43). Therefore, as the player pushes into the ground they are applying both a vertical and horizontal force. Furthermore, to ensure that the server lands in front of the service line they will also need to push backwards from the balls of their feet in order to generate an equal and opposite force forwards. The ground then exerts an equal and opposite reaction force to accelerate the player in an upward and forward direction. This can be seen in Part B of Figure 5 in which the player is applying both horizontal and vertical forces. Therefore, in order to jump higher the server needs to overcome inertia by applying a large and well-directed force against the ground. The server should then as soon as possible extend both arms to utilise the moment of inertia and equal and opposite reaction forces to translate into the delivery of ball contact.

-Backward extension of arms

Figure 6: An elite volleyball player's shoulder hyperextension joint angle (Alexander, et al., 2010).

During the process of the jump the sever is required to shift the centre of gravity by using the arms. To initiate the jump phase, the server’s arms swing backwards into a horizontal position. The shoulder is at its maximum hyperextension in order to attain maximum position for the forward swing. Trunk flexion is accompanied with the shoulder hyperextension and thus a higher shoulder extension. Figure 6 demonstrates an elite volleyball player’s shoulder hyperextension joint angle. The athlete has increased her range of motion for her arm swing allowing a generation of more energy. This energy transfers during the swing phase to provide increased vertical ground reaction forces, facilitating a higher vertical jump performance (Alexander et al., 2010; Hsieh & Heise, 2008). To improve vertical jump performance athletes should ensure they extend their shoulders backwards and swing through fast in order to benefit from the greater range of motion created.

-Flexing Trunk

Figure 7: The kinetic variables produced by the servers arm swing can result in kinetic energy being transferred through into the jump.

As shown in Stage 1 of figure 7, the knee, hip and ankle extensors contract to lower the body mass as the player flexes the trunk forwards. This allows the tendons to stretch and store elastic energy. The server then rises by sequentially extending the hips then the knees and ankles. As the hips extend upwards the legs compress to perform a downward movement, rapidly shortening the calf muscles and further stretching the tendons. When the force of the tendons is high enough they will begin to recoil at high speeds creating high kinetic energy. As opposed to the server starting the swing phase at stage 2 or 3, to increase the speed of the jump the athlete should ensure they are flexing the trunk forward to allow for maximum flexion of the leg joints and therefore maximising tendon recoil.    

-Flexing Knees

The position of the trunk and the flexed knees also helps to keep the head stable once the server is airborne. As the server flexes their legs behind them and raises their arms to contact the ball, their centre of gravity moves higher in their trunk. As the centre of gravity moves downwards during the hit, the server can manipulate their body according to the law of conservation of momentum by extending their legs to thrust their upper body higher. This allows the server to keep their eyes and head relatively still whilst they execute the skill. This will help improve the accuracy of their serve, because the player is afforded time to track the ball to attack strategically. In order to “hang in the air”, servers should ensure their legs are flexed behind them at the peak of the jump and then rapidly extend them as they make contact with the ball.

Airborne phase- Arm swing

-Shoulder and body rotation

Figure 8: Not being square to the net increases the torque of the entirety of the body, therefore producing more force on the ball. Also shown is the backwards ‘C’ shape of the body as a result of this. (Image from: http://kenyapage.net/commentary/kenya-sports-commentary/taking-kenya-volleyball-to-next-level/) (Author Generated)

- Extending Shoulder

Prior to the contact phase the extension of the shoulder, elbow and wrist joints move sequentially to adopt a throw-like movement, catering for greater velocity to be achieved. As the shoulder extends backwards its tendons are stretched storing elastic energy. The shoulder is then propelled in a forward motion as the tendons are recoiled to achieve a force multiplication effect. Therefore the server should maximise the extension of the shoulder to increase the elastic energy that the tendons can store, resulting in an increased force multiplication effect.

- Long levers

To initiate the ball contact the server ensures that the hitting arm is extended to create a larger lever for rotation around the spine. The moment arm is increased, as the distances from the arm muscles to the joints are larger. This allows force to be applied over a greater distance, which in turn generates more torque around the joint and therefore creates more acceleration on to the ball. To ensure the volleyball is contacted with maximum force, the server should ensure their hitting arm is at full extension when making contact with the ball.

- Aligning hitting arm

To complete the swing phase the server directs the extended serving arm up towards the ball, in an attempt to increase the force production to overcome inertia. This is done by ensuring the arm extends directly above the shoulder, rather than out to the side. As the weight of the arm and hand is closer to the primary source of power production, the server will be able to increase the force on to the ball.  To increase the velocity of the ball servers should attempt to align their hitting arm directly behind the ball.

Contact phase

-Firm hands

The preliminary aspects for the contact phase require the server to; locate the hitting shoulder in line with the ball, be at the peak height of their jump, as well as have the contact arm at fullest extension for the highest possible point for the server (Lithio, 2006), that is, the upper limb should be flexed and internally rotated at the shoulder and the elbow extended (Alexander et al., 2010; Reeser, Fleisig, Bolt & Ruan, 2010). The collision between the hand and the ball will have a higher co-efficient of restitution if the palm of the hand makes the contact rather than the fingers. Although the fingers should be slightly spaced to increase the surface area of the hand (Blazevich, 2007), the fingers have the ability to flex and therefore provide less stability. However, using the palm of the hand will provide a solid surface for the ball to hit, replicating that of a hard surface. Producing a solid surface with the palm by engaging the hand muscles, the restitution of the ball will be maximised as less energy can be potentially lost in the collision between the hand and the ball. This will increase the velocity of which the ball leaves the hand. To improve contact of the ball the server should ensure the ball is contacted with the palm of the hand directly facing the ball and fingers extended, just as the elbow completes its extension.

-Quick contact

Figure 9: The energy produced in kinetic chain of the volleyball jump serve. (Author Generated)

The purpose of the contact phase is for the accumulation of all the biomechanical principals to come together and thus transfer the forces, speeds and sequential acceleration from the kinetic chain of the legs, knees, hips, torso, shoulders, arms, elbows, wrists and fingers to be imparted on the volleyball. Faster hand contact on the ball as Hirunrat and Ingkatecha (2015) describes is one of the most effective variables for the jumps serve in order to transfer momentum. Figure 9 demonstrates the order in which the energy is transferred from the lower extremities to the higher extremities and then to the ball. In the upper extremities as the optimal movement progresses from the proximal (the shoulder) to the distal end of the arm (the fingers), the distal end of the arm is accelerated (Hirunrat & Ingkatecha, 2015). Newton’s second law of motion is in interplay where “the acceleration of an object is proportional to the net force acting on it and inversely proportional to the mass of the object” (Blazevich, 2007, p. 43). This increase in the velocity of the body is important for more power and faster hand contact with the ball, thus a faster ball acceleration. In simple terms the contact phase can therefore be seen as ‘the last chance’ to impart on the intended outcome for the flight of the ball. 

-Contacting above centre of the ball

Figure 10: The imparted ball spin resultant of the Magnus Effect by contacting the right, left, top or bottom of a volleyball.

For successful performance the properties of the Magnus Effect need to be considered. The Magnus Effect reflects the airborne time of the volleyball in relation to the speed of the air over the ball as well as the speed of the spin of the ball (Blazevich, 2007). In contrast to hitting the ball with the palm in the centre of the ball travelling straight off the face of the palm, spin servers modify the direction of the ball by contacting it with an off centre force such as hitting the top of the ball where the top spins over the bottom. This can be seen in Figure 10 in the last contact example phase. As such top spin is characterised by the air on top slowing down and the air underneath moving relatively quicker (Blazevich, 2007). Multiple studies by Huang and Hu (2007) and Lithio (2006) concluded that the top spin serve was the most effective in that it had higher velocity speeds than other serves such as the jump float serve. By using the top spin approach the airborne time of the volleyball can be reduced as the top spin will cause the volleyball to quickly dip as it is travelling towards the ground. In order to increase the chances of effective top spin the server should be sure to snap their wrist over the ball. The server should intend to connect with the ball slightly above the centre of the ball which will determine a greater capacity for the wrist snap action (Reeser, Fleisig, Bolt & Ruan, 2010).

-Angle of trajectory

Immediately after the contact phase the volleyball is under the influence of its projection speed, projection angle and the relative height of projection (Blazevich, 2007). Because of the requirement for a high vertical jump in the jump serve at ball contact the volleyball already has extra flight time than if it were projected at ground height. In order to make it difficult to receive the ball for the opposing team, instead of giving the ball maximum vertical velocity the server should concentrate on the horizontal velocity therefore the optimal release angle is decreased and a flatter initial projection angle can be imparted to the ball (MacKenzie, 2012). By the server creating aforementioned top spin, the projection angle is decreased. To optimise the angle and speed of the shot the server needs to create an angle of release that is precise in that it is high enough to get over the net, but steep enough to make the ball drop quickly, increasing the difficulty for an effective return (Alexander et al., 2010). As a result of these post impact kinematics, MacKenzie (2012) indicates that the ball will correspondingly spend less time travelling, thus demanding quicker responses from the opposing team for returning the ball.

Follow through and landing

- Long follow through

After the hand has made contact with the ball, the hitting arm should diagonally move across the body through shoulder flexion and adduction and trunk rotation.  Alexander et al. (2010) describes how in order to decrease the force and speed applied to the arm the follow through should be performed over the longest time and distance as possible.

- Land on both feet

Both feet should be landed on from the jump. A flexion of the knees, ankles and hips should accompany the landing to absorb the impact of ground forces and to avoid injury. To provide a large base of support for the landing, create a centre of mass significantly smaller and ensure that weight is evenly distributed, the server should land with their feet shoulder width apart.

The Answer

By examining the biomechanical principles in play during the phases of the jump serve, we can now conclude that the optimum technique requires all phases to be completed fluently in order to effectively transfer force production. Therefore a server should consider releasing the ball with their hitting arm, creating a large base of support and releasing the ball at the highest point with a flick of the wrist during the phase of the ball toss. To optimise the run up and approach phase, the server should accelerate off the balls of their feet, take large strides, and keep the centre of mass low. To initiate the jump phase the server should extend their arms backwards as they flex their knees and trunk and then swing through fast as they rise. As the player is airborne, they should extend their striking shoulder back as they keep their elbow high then extend their hand upwards to meet the ball. As the server makes contact with the ball they will need to ensure that it is done so with a firm hand above the centre of the ball and then quickly snap the wrist over the top of the ball.  To finish the serve the server should follow through with the serving arm and land on both feet, shoulder width apart. A server should strive to complete all phases in this biomechanically efficient manner, to ensure the momentum and forces created are transferred to the ball. This will ultimately make the ball travel at faster velocities, which in turn will result in a more difficult serve to return.      

How else can we use this information?

The optimal biomechanical principals mentioned above can be used to better understand the internal and external factors affecting performance in many sports. Understanding the principals at play emphasise how smaller skill improvements in a subsystem of a skill can make a large difference to the execution of the total skill. By understanding these principals, coaches and teachers can help identify errors in their student’s execution of a skill, thus being able to break the skill into progressions to correct them and build them back up to optimise their technique. For example, a beginner server often is focused on obtaining accuracy for the projection of the ball over the net, nevertheless this often results in a push like movement or a short arm jab movement. By teachers focusing on the run up, jump phase and contacting the ball at the peak of the jump, students are given an implicit focus which will allow students to use a throw-like movement as a result of the speed and force produced in the prior phases.

In many sports there is limited time to apply forces where there is also limited time as an opponent to engage reaction responses. As a defending position, understanding the movement actions such as body position, velocity and acceleration such as the wrist and fingers at the end point of the serve can inform information movement coupling as an opponent. The opponent can understand the independency of information for movement of an incoming balls flight path in relation to their bodies speed, power and limb organisation. Players can become attuned to key informational variables, which regulate behaviour such as the server hitting the ball with a high off centre force, which provides the information that the ball will dip quickly. This is useful for many sport for example cricket or tennis where if the fielder or opponent knows what spin was placed on the ball, the flight path can be predicted and also as the ball is moving in the air they may be able to predict the spin of the ball after hitting the ground.

The principals of ground reaction forces and coefficient of restitution can be further applied to the variations of volleyball surfaces. For example, the height in the vertical momentum of the jump, can be optimised by applying a greater force against the ground in which a greater reaction force is created encouraging upwards momentum. In this sense if the grounds surface has a higher co-efficient of restitution, there is greater reaction forces. Nevertheless, if the ground was wet it would have a lower co-efficient of restitution when the foot makes contact, which would require more energy to get the reaction force back. The same principals apply to beach volleyball where a greater downwards force would be required to achieve a high vertical jump, when compared to indoor volleyball, as the sand is flexible and soft, absorbing most of the force and power.  In order to achieve a greater downwards force in the sand a study concluded that that there were significant differences between the values of ankle joint angles during starting posture and of hip joint at the moment of take-off, where the ankle joint range of motion and angular velocity was larger although there was still reduction in maximum force and take‐off velocity (Giatsis, 2004). This understanding would in turn require a higher ball toss, to give the player more time to perform the run up and jump phase.

References 

Alexander, M., Honish, A., Center-Manitoba, C. S., & Center, K. (2010). An Analysis of the Volleyball Jump Serve. Sport Biomechanics Lab University of Manitoba.

Blazevich, A. (2012). Sports biomechanics the basics: Optimising human performance (2^nd ed.). A&C Black Publishers.

Giatsis, G. , Kollias, I., Panoutsakopoulo, V. & Papaiakovou, G. (2004). Volleyball- Biomechanical differences in elite beach‐volleyball players in vertical squat jump on rigid and sand surface. Sports Biomechanics, 3(1), 145-158.

Hirunrat, S., & Ingkatecha, O. (2015). Kinematics and Kinetics of Jumping Serve in Youth National and National Thai Female Volleyball Players of Thailand. International Journal of Sport and Exercise Science, 7(1), 13-16.

Hsieh, C., & Heise, G. D. (2008). Arm swing of volleyball spike jump performance between advanced and recreational female players. In Proceeding of Fourth North American Congress on Biomechanics, University of Michigan, Ann Arbor, Michigan, USA,(August 5-9) (pp. 306-307).

Huang, C., & Hu, L. H. (2007). Kinematic analysis of volleyball jump topspin and float serve. In XXV ISBS Symposium (pp. 333-336).

Lithio, D. (2006). Optimising a Volleyball serve. Western Reserve University: Hope College.

MacKenzie, S. J., Kortegaard, K., LeVangie, M., Barro, B., Kanchanomai, C., Phiphobmongkol, V., ... & de Jesus, K. (2012). Evaluation of two methods of the jump float serve in volleyball. JAB, 28(5).

Reeser, J., Fleisig, G., Bolt, B., & Ruan, M. (2010). Upper Limb Biomechanics During the Volleyball Serve and Spike. Sports Health, 2(5), 368–374.

Tant, C. L. and K. J. Witte (1991). Temporal structure of a left-hand toss vs. a right-hand toss of the volleyball jump serve. Biomechanics in Sports IX, Iowa State University, International Society of Biomechanics in Sports.