What are the biomechanics behind performing a successful overhead volleyball serve?

Introduction

The different forces that act on the human body and the effect these forces have on the human body is the underpinning of the science of biomechanics.  Biomechanics allows educators, coaches and athletes to analyse the individual components of a skill and have the scientific background to be able to do so (Snigh, 2013).  Biomechanically, the volleyball overhead serve can be applied to the concept of the kinetic chain, a series of linked body parts that move together.  More specifically throw like movement patterns, meaning the kinetic chain extends sequentially. (Blazevich, 2010, p196-198). 

Major Question

The serve in volleyball is an integral skill within the modern game (Kumar et.al, 2012).  The game is initiated with a serve and is described as the first offensive attack, in this case the overhead serve is the focus (Huang & Hu, 2007; Kumar et al., 2012).  The overhead serve can either be performed as a float (video 1) or topspin (video 2) serve and can be accomplished from either a standing or jumping position.  For a successful float serve the ball is hit with the heel of the hand, which produces no spin resulting in a path that is unpredictable (Nathial, 2012).  While the hand placement of the topspin serve, the palm and fingers make contact with the ball provides the topspin, generating more power and is generally used in conjunction with a jump serve (Charalabos et al., 2013).  Jump serves have a higher ball toss than a standing serve.  When contact is made with the ball by the server off the jump, a strong downward motion from the striking arm makes it difficult for the defence to respond.  Hence why it is favoured in Collegiate and Professional competitions (Charalabos et al., 2013; Nathial, 2012).  During an overhead serve, whether it is float or topspin there are several characteristics that are common to both, the ball toss, arm swing, hand contact on the ball, foot placement and follow through (Nathial, 2012). 

This information helped to form the question, what are the biomechanics behind performing a successful overhead volleyball serve?

Video 1:The technique for the standing float serve (YouTube, 2014)

Video 2: The technique for the jump topspin serve (YouTube, 2009)

The Answer

Lower body movement during standing float serve and jump topspin serve

The movement of the lower extremities is the beginning of both the float and topspin serve.  During the float serve, the server steps forward with the non-dominant foot, making contact with the ground where vertical force is applied creating an equal and opposite ground reaction force (Newton’s Third Law).  The force created as a result of foot contact with the ground applies a force great enough to change the state of motion of an object (Newton’s Second Law).  During the float serve it is the state of motion of the volleyball we are attempting to change, from the current vertical force to a horizontal force.  The force applied has to be large enough to over the inertia of the ball (Blazevich, 2010, p.45). 

The topspin serve comprises a run and jump component to it serve.  The run up consists of three to four initial steps then a jump.  To achieve the optimum biomechanics during the short run up, each time a foot make contact with the ground, it generates an equal and opposite ground reaction force (Newton’s Third Law).  There needs to be the largest conceivable force applied for as long as possible, creating impulse to generate the greatest change in momentum (impulse-momentum relationship).  The larger the force generated the greater the transfer is during the jump stage of the serve.  When transitioning from the run into the jump there are both vertical and horizontal forces to be overcome in order to change the state of motion.  The ground reaction force helps to propel the run forward and the jump up.  The force applied from the ground reaction force during the final step must be greater than the inertia created by the server in order to initiate the jump (Blazevich, 2010, p.45-58).

Torso movement through the float and topspin serve

During both the float and topspin, torso movement remains the same, although the force generated by ground force reaction in the step forward or run up is increased (Balzevich, 2010, p.45).  The torso starts facing the net and the rotation occurs at the transverse plane and rotates to a 45° angle, which would not alter the current centre of gravity or centre of mass (Blazevich, 2010, p.16).  As the torso rotates forward again, force is generated from the mass of the body and acceleration, propelling the whole body forward.  This results in the hand of the service arm making contact with the ball.  The rotation acts as another mechanism that creates a force capable of changing a state of motion of an object (body being propelled forward), as the force is great enough to overcome the inertia (Blazevich, 2010, p.8)

Upper limb mechanics of the float and topspin serve

There are five phases when performing the float (figure 1) and topspin serves (figure 2).  At the wind up phase of the arm movement during the float serve, the service shoulder abducts while the non-service shoulders begins to extend, which starts the release of the ball.  The service arm also exhibits flexion at the elbow decreasing the angle creating a smaller lever, meaning the moment of inertia is also smaller (Blazevich, 2010, p.73; Rokito, 1998).  The cocking phase initiates the external shoulder rotation (torque) increasing the angle through extension at the elbow, therefore increasing the moment of inertia.  As the external shoulder rotation increases and reaches its maximum it triggers the internal rotation of the shoulder and extension at the elbow.  When the torque of both is at its maximum it initiates the acceleration to propel the arm forward so the hand can make contact with the ball.  During the acceleration transition into deceleration the moment of inertia is greatest for the service arm.  The service arm is completely straight producing the longest possible lever increasing the force, accelerating the arm forward, thus increasing the moment of inertia.  The deceleration and follow through see the service arm start to abduct and continue to do so until it comes to rest at the service player’s side ready to play the next shot (Rokito, 1998)

Figure 1: The motion for the standing float serve (Tribesports, 2012).

The only difference between the arm action of the standing float and jump topspin serve is the arm action during the wind up phase.  There is abduction of both the service and non-service arm behind the body and by propelling the arms back towards the body and then up above the head there is an increase in force generated from the rotation (torque) (Blazevich, 2010, pp.63-65, Rokito, 1998).  This combined with force generated from the run up and torso movement increases the force that is imparted on to ball at the point of contact, influencing the coefficient of restitution (Balzevich, 2010, p.73).

Figure 2: The motion for the jump topspin serve (Mercerisl and volleyballclub, 2015).

Impact of the hand on the ball

When contact is made on the ball by the heel of the hand during a float serve and the palm and finger during the topspin serve (figure 3), the outcome is affected by both the coefficient of restitution and Magnus effect.  The coefficient of restitution describes how an object retains energy after a collision, in this case how much energy the ball retains after colliding with the hand to be propelled forward (Blazevich, 2010, p.117). 

Figure 3: The different hand placement of the float and topspin serve (Volleyball, 2015).

Magnus effect demonstrates how the flight path of a spinning object is affected by force (Blazevich, 2010, p.188).  According to the Magnus effect during the float serve, the unpredictable flight path is caused by the variation in rough surfaces on the ball.  Hitting the ball without spin causes air flow to impact the path of the ball, it impacts the rough surfaces causing the ball to rotate slightly.  As this is a continual effect throughout the flight path the ball continues to rotate slightly, resulting in the unpredictable flight path (Blazevich, 2010, p.192).

The flight path of the topspin serve is more predictable than the float serve, however it is more difficult to return due to the heavy topspin and speed at which it is hit (Kumar et al., 2012).  When topspin is placed on a serve it is hit with high horizontal velocity and the air flow around the top of the ball moves at a slower pace than the airflow underneath the ball (relatively quickly).  The pressure exerted onto the top of the ball causing a downward force is similar to that of the spike, making difficult to return (Blazevich, 2010, p.193).

Injury concerns

The most common injury arising in volleyball related to the serve is in the shoulder and occurs more often with the jump topspin serve than with the float serve.  Injuries to the shoulder relate to chronic overload which is derived from a combination of repetitive jump serves in association with spikes.  Volleyball players responsible for the spikes should limit the number of jump serves they perform, specifically in practice (Resser et al., 2010).  The float serve is safer in terms of resultant injury compared to the topspin serve, however the topspin is favoured at the collegiate and professional level due to the speed and ultimate placement of the ball (Resser et al., 2010; Kumar et al., 2012).

How are the biomechanical principles influenced by movement?

The kinematical variables assessed during the volleyball serve are the joints where rotation occurs.  The joints assessed were the ankles, knees, hips, shoulders, elbows and wrists, these are the angular kinematics.  The studies considered how each of the joints were affected at stance and execution and whether there was any correlation between the two.  Studies found that there was not a significant correlation between stance and execution, concluding that angular kinematics have a limited effect on the overhead serve (Nathial, 2012; Singh, 2013).

REFERENCES

Blazevich, A. J. (2010). Sports biomechanics: the basics: optimising human performance. 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, 9(2), 2083-2086.

Escamilla, R.F., & Andrews, J. R. (2009). Shoulder muscle recruitment patterns and related biomechanics during upper extremity sports. Sports medicine, 39(7), 569-590.

Huang, C., & Hu, L. H. (2007, December). Kinematic analysis of volleyball jump topspin and float serve. In 25 International Symposium on Biomechanics in Sports (pp. 333-336).

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

Mercerislandvolleyballclub.com,. (2015). CONDITIONING | Mercer Island Volleyball Club. Retrieved 19 June 2015, from http://mercerislandvolleyballclub.com/conditioning/

Nathial, M. S. (2012). Motion Assessment of Volleyball Overhead Serve. International Scientific Journal of Sport Sciences, 1(2), 105-112

Reeser, J. C., Fleisig, G. S., Bolt B., & Ruan, M. (2010). Upper limb biomechanics during the volleyball serve and spike. Sports Health: A Multidisciplinary Approach, 2(5), 368-374.

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.

Singh, M. SKILL ANALYSIS OF VOLLEYBALL SERVE THROUGH KINEMATIC APPLICATIONS.

Tribesports,. (2012). Float Serve. Retrieved 19 June 2015, from
http://community.tribesports.com/challenges/float-serve

Volleyball, H. (2015). How to Jump Serve a Volleyball. wikiHow. Retrieved 19 June 2015, from http://www.wikihow.com/Jump-Serve-a-Volleyball

YouTube. (2009). Jump Topspin Serve. Retrieved 19 June 2015, from https://www.youtube.com/watch?v=0XTB8vkV5bI

YouTube. (2012). How to do an overhead volleyball serve. Retrieved 19 June 2015, from https://www.youtube.com/watch?v=9QRnGaFitCc