Major Question

Trent Harris & Ross Dempster

Major Question: What are the optimal biomechanics for a Volleyball serve?

Introduction

The volleyball serve is a closed skill, players have the option of deciding when to initiate the feed (throw) and also when to make the connection. They are also capable of dictating the accuracy and power of the serve. Corrections can be made on technique to achieve the most effective serve, more specifically, biomechanical principles become the highlight. Some of the variables in focus will be torque, centre of mass, angular/linear velocity, impulse-momentum, kinetic chain, inertia, angular kinetics, Newton’s three laws of motion, throw like movements, coefficient of restitution, velocity, acceleration, projectile and range of motion. Serving in volleyball has a number of variations, these include the jump, standing and underarm while also being able to manipulate the ball spin. The standing serve will be the focus throughout the blog. Breaking the skill into movement phases will be crucial to exploring the biomechanics in detail, these stages include the ball toss, stepping motion, draw back, hitting, ball on hand placement and finally the follow through. Visual elements will be referred to regularly in order to help describe the exact movement phase in discussion. Understanding which biomechanical principles are evident and the importance they play in order to gain optimal performance will be comprehensively discussed throughout. 


The volleyball serve is a fundamental skill within the modern game (Kumar et al., 2012). The serve can be accomplished with numerous intentions, featured in the videos below (Elevate yourself, 2015; About.com, 2012), the server has the choice of either a float or top spin, both with their own benefits. The float serve has the ball deviate and alter direction mid-flight, making it very difficult for the opponent to successfully read the trajectory, creating an unpredictable component to the game (Nathial, 2012). For the top spin, the ball trajectory changes rapidly and can suddenly drop on opponents creating a difficult shot (Charalabos et al., 2013). How these two variations of the jump serve can be altered generating an optimal performance will be the primary focus of the bog. 

Elevate yourself, 2015. Float Serve.

About.com, 2012. Top Spin serve.

The Answer

Ball Toss
The ball toss is a very important step in the volleyball serve. The initial step is to distinguish which hand will be the dominant (hitting) hand. From here, the non-dominant hand should be used as the feeder allowing the torso and trunk to open up during the draw back phase. When it is not conducted properly, the ball trajectory is wayward making it difficult for the server to achieve maximum power and accuracy. The ball toss itself is labelled as a push-like movement pattern, this being because all the joints are extended simultaneously in a single movement. The simultaneous joint rotations often result in a straight-line movement at the end point of the chain. This straight line movement is evident in (figure 1.) By maintaining this straight line movement, highly accurate results can be achieved. The push like movement can be effective when the end of the kinetic chain is free to move (in this instance the hand), because the hand is not in a fixed position the ball toss is classified as an open kinetic chain movement (Blazevich, 2010). The optimal angle of ball release is 0 degrees as in throwing the ball directly vertical, the arm must remain extended and straight to ensure the greatest amount of accuracy is achieved. This is due to the ball being thrown in front of the body which allows the hitting arm a sufficient amount of time and range to step in and connect, increasing the impulse-momentum. In order to gain momentum, the non-dominant hand performs a slight draw back. To change an object’s momentum, a force must be applied (Blazevich, 2012). At the initial stage of the ball toss (figure 1.) the hand in possession of the ball must lower to increase the force applied to the stationary object. The ideal starting position is to have the non-dominant arm extended in a 90-degree angle from the torso to the ulna (hitting hand), step 1 (figure 1.). By starting in this ‘ready position’ the player has given themselves the greatest opportunity of generating efficient accuracy, acceleration and velocity in the push-movement. An increased arm acceleration will result in increased velocity leading to greater momentum (Momentum = Mass.Velocity) (Physics Classroom, 2016). With the aim to increase momentum, this will allow for a greater ball trajectory, meaning the server is provided with more time to position themselves and connect with the ball at a higher point. 

Figure 1.

Stepping motion

The stepping motion of the volleyball serve is a simple, yet important part of the volleyball serve when considering power. In (figure 1) looking only at the feet position you will notice that the sever has their feet almost parallel to each other with the feeding foot slightly forward. Before throwing the ball up, the weight should be transferred slightly onto the back foot. After the ball leaves the hand during the ball toss, step the feeding foot forward while bringing body weight forward as well. This transfers the weight from the back foot to the front, which brings the force and centre of gravity forward and therefore creating forward momentum (Poynter & Bachmatiuk, 2015). During the hitting motion (figure 1, frame 4) the back foot will generally be lifted onto the toes to allow a greater transfer the weight onto the front foot which creates an ultimately increasing momentum. In addition to this increased momentum from lifting the back foot, it also produces greater acceleration onto the ball as the server is hitting the ball while in motion and created greater inertia. Newtons 1st law mentions that an object will remain in motion with the same speed and direction unless acted upon by an unbalance force (The physics classroom, 2016). In relation to the volleyball serve, the object (server) will remain in forward motion until acted upon an unbalance force (ball), which forward motion will be transferred to the ball minus the force/inertia required to move the ball from its predicted path. Newtons third law also comes into consideration when the front foot is planted into the ground. Which is stated as “for every action, there is an equal and opposite reaction. When the foot contacts the ground in a downwards force, the ground exerts an equal and opposite reaction which accelerates us forward due to the transfer of weight (Blazevich, 2010). In relation to the centre of gravity, it is favourable to have it slightly forward of the midline of the body as having the mass further away from the midline of the power production it is harder to generate inertia (Magias, 2016). While having it backwards causes the body to lose momentum as the body is sent in the wrong direction.

Draw back phase:

In the early phase of the hitting motion of the volleyball serve, the hitting arm is placed in a cocked ready position. This phase is called the drawback phase, where the server is drawing their arms back in this read position while the ball drops. A major component of the drawback is having the hitting elbow high, around a 90 degree angle from the torso to the humorous. In addition to having the hitting elbow high, the hitting hand should be around head high with minimal distance between the hand and shoulder. This is to allow a greater range of motion between the humorous and the Ulna. From this increased angle or range of motion, it will allow the server to generate a greater impulse-momentum which is “applying the largest force possible for the longest time possible” (Blazevich, 2010, pg. 51). This results in an increased time that the muscles can be activated and thus increasing extension velocity. Once the ball is in the air the joints of the arm move in a throw-like movement pattern, where movements in the joints of the kinetic chain move sequentially one after another (Blazevich, 2010). The sequential order of this movement begins with the shoulder and elbow moving in a backwards motion, where tendons are stretched and elastic energy is stored. Elastic energy is the result of the muscle being stretched before contraction acting as a catapult which contains more energy and can result in a more powerful contraction (Sports science lab, 2016). The major muscle groups that will be incorporated are the pectorals, trapezius and the triceps.

The guiding hand during this phase is left above the head as it was during the ball toss phase. This is intentionally done to create greater accuracy in the shot and to produce greater power during the hitting phase. By leaving the hand high it allows the server to judge the distance, by creating a visual cue of the distance between the guiding hand and the ball. This guidance allows the server to hit the ball at the highest point of release. The greater height of release the further the horizontal distance the ball will travel. Having a greater height of release during a volleyball serve the more effective the serve will be, due to the ball being hit at a higher point and reducing the angle required for the ball to go over the net (Beaven, 2015).

Hitting phase:

Progressing on from the draw back stage, the next sequence in the serve is the hit. In this stage it is referring points 3 and 4 (Figure 2.), this is just after the hitting arm has been drawn back, however ball connection will not be discussed within this phase. The hitting phase uses a throw like motion which transfers into a push like motion in the final stages. During the throw like motion the joints in the kinetic chain extend sequentially, this meaning one after another. This sequential motion promotes summation of forces to occur. As (figure 4) shows summation of forces occur when the joint/muscle groups move in the correct sequence and the joint only moves as the prior has reached its maximal force generated, progressively adding to its potential power. Later on in the throw, the extension velocity of the hand and fingers increases significantly, resulting in a high ball release velocity (Blazevich, 2010). The sequential order of the joint progression begins with the shoulder rotating forwards, from this the wrist and forearm swings around straightening the arm and locking the elbow joint. We can take this sequence into consideration by understanding angular velocity, which is the rate of change of acceleration over 360 degrees (Magias, 2016). By increasing the distance from the hand (lever length) from the axis of rotation (shoulder) while still maintaining angular velocity, a greater release velocity is achieved. As mentioned prior the sequence begins as a throw-like movement and finishes in a push-like movement, as seen in (figure 2.). Getting this hitting sequence correct is very important for the optimal projectile motion. By achieving the highest point of release, this allows the player to decrease the angle of release required to propel over the net and into the opponent’s side of the court. Resulting in the server connecting with the ball at a greater horizontal speed and velocity. Gravity also has a very important influence upon height/angle of release, gravity only acts on bodies moving with vertical motion (Blazevich, 2010), by decreasing this vertical motion the server can acquire greater power with less resistance. (Figure 3.) relays this optimal angle, displaying the impact gravity and resistance has on trajectory. If the arm connects with the ball too close to the body or too far from, the exact result occurring within (Figure 3.) will happen on the serve, failing to enter the opponents side of the court. The optimal angle of release is 45 degrees when released from the ground, however as the server will be releasing (depending on server height) the ball from around 2-3 meters and the volleyball net height is 2.4 meters the optimal angle is reduced significantly depending on the power placed on the ball. However, the serve does not have to a small angle of release for success, there is a serve called the short serve where backspin and high angle of release (60degrees+) to allow the ball to just drop over the net. Impulse-momentum becomes very important in the hitting sequence, with the improved draw back mentioned prior, this allows the muscles to be activated for a longer period generating a greater amount of force at the point of contact. The lever length (arm) should also be extended to the fullest, resulting in an increased final velocity. Final Velocity (vf) = intial velocity (vi) + acceleration multiplied by time (at).

In addition to the serving hand, the feeding hand also plays a role in adding forward momentum onto the ball. As the serving hand starts its movement the feeding arm is ripped down and fully extended behind the back. This is in relation to newtons third law of equal and opposite reactions. By swinging the arm backwards fully extended it has allowed for a greater angular velocity to be achieved in a backwards direction, which in turn sends the body forward for an increase in momentum. It also allows the chest to be opened up allowing for a larger muscle group to be added to the force summation while also creating a pendulum affect with both arms for greater balance.

Figure 2. 

Figure 3.

Figure 4.

Hand on ball placement

The hand placement/connection with the ball can alter the ball trajectory greatly. As previously mentioned, the two variables in focus will be the Top Spin along with the Floater. The impact from the hand and the velocity of the arm both impact the swing/direction of the ball (Miller, 2005). Rokito et al., (1998) state “At the moment of ball contact, the accelerating upper limb should be flexed and internally rotated at the shoulder and extended at the elbow”. During both variations of the serve, when either heel of the hand or palm and fingers make connection (Figure 5.) the outcome is affected by both the coefficient of restitution and Magnus effect (Sandercock, 2015). The coefficient of restitution refers to the ability of an object to retain energy after a collision, specific to (Figure 5.) it is focused on how much energy the ball maintains after a smooth strike of the hand being propelled into the oppositions court (Blazevich, 2010). The Magnus effect establishes how the aeronautical path of a spinning object is affected by force (Blazevich, 2010). In relevance to the float serve, the unpredictability of flight path comes as a result of rough surfaces on the ball, causing the ball to rotate slightly (Blazevich, 2010). Opposing players find these serves incredibly difficult to return effectively, judging the flight path and connecting with a ball swaying side to side is no easy task. The Top spin serve is conducted in a different way to the float serve, by striking the ball with the fingers and palm of the hand this generates the ball to be spinning forwards in a downwards motion. Although his serve is more predicable to read when compared with the float serve, the difficult of returning it is higher. This comes as a result of the heavy top spin, velocity and momentum of the ball and the Magnus effect creating the downward drop (Kumar et al., 2012). The air flow coming over the top of the ball moves at a slower pace than the airflow beneath the ball, to gain the optimal downward drop the serve should be struck at a higher angular velocity allowing the Magnus effect and gravity to add a greater downward force (Blazevich, 2010). Both serves have their individual benefits, variation is important to ensure the opposition find it problematic to read the serve style. Volleyball can be both an inside and outside sport, our sport is inside meaning the environment has no impact on the optimal angle of release, if it were outside wind resistance would have to be considered. The shape of the volleyball influences the flight path and optimal angle of release, a standard volleyball weighs approximately 0.27kgs with a radius slightly over 4”. It also is designed with shallow grooves along its outer shell which affect the turbulence around the ball (Lithio & Webb, 2006). The ball is also designed with slight dimples, intended to generate accurate flight patterns. The light ball and its inflation allows the ball to float and spin to a greater degree, the elasticity also affects the coefficient of restitution. An increased surface area of the ball gives players the opportunity of greater hand contact which increases control, power and accuracy (Poynter & Bachmatiuk, 2015).

Figure 5.

Follow through

The final part of the volleyball serve is the follow through, which its main aspect in the volleyball serve is to provide greater accuracy. By continuing the range of motion well past the impact of the ball in the direction intended, the balls flight path is more predictable and precise. This follow through phase allows the object to be hit before actions of the body comes to a rest. By following through it allows all body movements to occur become coming to a rest and the full action to be performed. The follow through will continue the push like motion that occurs late in the volleyball serve to continue the kinetic chain and provide greater accuracy. Another bio-mechanical sporting example which is similar to bowling in cricket, abruptly stopping after the ball has been released puts strain on the joints. Following through carries out the movement in an orderly fashion and greatly assists the player to assume a ready position for the next set play. This part of the skill is crucial to recovery, injury prevention and the transition into the next play (Abendroth-Smith & Kras, 1999). Landing incorrectly after a serve and not allowing the body to follow through increases the chance of a trauma injury due to the greater impact stress (Mann, 2008). 

How else can we use this information?

The biomechanical principles highlighted throughout the blog can be an excellent resource for coaches or players struggling to identify faults within their serve. Using technology and software to the advantage of players would be very beneficial, coaches eye could be implemented into training sessions, now understanding the correct biomechanical principles athletes could quickly find faults in their game.

Not only for the sport of volleyball, but biomechanics apply to all sports. For example, very similar aspects apply to the jump shot and the spike within volleyball. In the sport of tennis, serving with an extended arm and lever will work to increase impulse-momentum, torque, moment of inertia and force. This fundamental movement pattern is evident in a range of sports and would not prove terribly difficult to transfer the knowledge between them.

Common net/wall games share similar fundamental skills, volleyball, tennis, badminton and squash. Lever length is very important amongst each of these sports, along with centre of mass, velocity, acceleration, coefficient of restitution, momentum, kinetic chain and other aspects covered in the blog.

Sport scientists could utilise the information to discover the reasons behind injuries. Breaking down the biomechanical principles in a skill will often uncover faults or other movements inhibiting the skill. This has already been evident when Brett Lee (famous Australian test cricketer) had his bowling technique critiqued and broke down. This discovered that his ‘sling-shot’ bowling technique allowed him to release the ball up to speeds exceeding 150 kmph, however, as a result it caused stress fractures in his lower back forcing him in and out of the side (Magias, 2016),(Figure 6 & 7). This information will prove very beneficial for sports players, coaches, parents etc. all around the world. 

 Figure 6

Figure 7

Reference List

Abendroth-Smith, J., & Kras, J. (1999). More B-BOAT: The volleyball spike. Journal of Physical Education, Recreation & Dance. 70(3), 56-59.

About.com. (2012). How to do a Topspin serve in Volleyball. Retrieved 16^th June, 2016. <https://www.youtube.com/watch?v=UcWyIjDfOj8>

Beaven, P. (2015), Biomechanics of volleyball, Academia, Accessed from: http://www.academia.edu/8070897/Biomechanics

Blazevich, A. (2010). Sports biomechanics, the basics: Optimising human performance. A&C Black.

Blazevich, A. (2012). Sports biomechanics. London: A. & C. Black.

Charalabos, I., Savvas, L., Sophia, P., & Theodoros, I. (2013). Biomechanical differences between jump topspin serve and jump float serve of elite Greek female volleyball players. Medicina Sportiva: Journal of Romanian Sports Medicine Society, 9(2), 2083.

Elevate yourself. (2015). How to serve a Volleyball tutorial (Part1/3). Retrieved 16^th June, 2016. <https://www.youtube.com/watch?v=NRV0rMeSOBI>

Kumar, A. (2012). Relationship of selected biomechanical variables with performance of volleyball players in jump serve. Sports and Yogic Sciences,1(3), 27.

Magias, T (2016) Skill acquisition and biomechanics for physical educators, lecture week (12), Flinders University, Sturt Rd, Bedford park, SA 5042

Magias, T (2016) Skill acquisition and biomechanics for physical educators, lecture week (7), Flinders University, Sturt Rd, Bedford park, SA 5042

Mann, M. (2008). The Biomechanics of the Volleyball Spike/Attack. Sport Biomechanics. 1-20.

Miller, B. (2005). The volleyball handbook. Human Kinetics.

Nathial, M. S. (2012). Motion assessment of volleyball overhead serve.International Scientific Journal of Sport Sciences, 1(2), 105.

Poynter, N., Bachmatiuk, A, (2015), HLPE3531 Biomechanics and skill acquisition, access from http://biomechanicsofaoverarmvolleyballserve.blogspot.com.au/

Rokito, A. S., Jobe, F. W., Pink, M. M., Perry, J., & Brault, J. (1998). Electromyographic analysis of shoulder function during the volleyball serve and spike. Journal of Shoulder and Elbow Surgery, 7(3), 256-263.

Sandercock. (2015). What are biomechanics behind performing. Retrieved 16^th June, 2016. <http://overheadvolleyballserve.blogspot.com.au/2015/06/what-are-biomechanics-behind-performing.html>

Sports science lab (2016), Muscles, rubber bands and elastic energy, accessed from: http://www.sportsciencelab.com/blog/tvitiello/muscles-rubber-bands-and-elastic-energy

The Physics Classroom. (2016). Momentum and its conservation. Retrieved 16^th June, 2016. <http://www.physicsclassroom.com/Class/momentum/u4l1a.cfm>