What Biomechanic Factors Influence the Initiation of a Volleyball Set?

Volleyball: A Brief Background

Volleyball, specifically indoor volleyball, is rapidly becoming one of the most popular mixed gender sports across the world. There are numerous, unofficial variations of the game however the official game of Volleyball, according to the international governing body of the sport, Federation Internationale de Volleyball, consists of two teams of six players who aim to hit a volleyball over a net and ground it on the oppositions side the court, to score a point.  Each team is allowed to contact the ball a maximum of three times before sending the ball over the net to score a point or for the opposition to play continue the rally. These rallies are continued until a team leads their opposition by two points, and has reached a minimum score of 25 points (FIVB, 2014).

To achieve this goal after the initial serve, each player uses a variety of hits – a dig, spike or set- to direct and propel the ball is a desired direction. League volleyballers generally have a distinct role and position within their team that allows them to utilise the appropriate hit for their role, although each player must know how to accurately and efficiently execute each of the skills.

Image 1 Source: Federation Internationale de Volleyball, 2014.

The Importance of the Volleyball Set:

Firstly, it is necessary to understand the importance of a volleyball set and its biomechanics to gain an appreciation for an effective set. The volleyball set (overhead pass) is a continuous and fluid combination of a catch and throw. A set is typically performed by the setter on the team, and is generally but not always the second contact that the team has with the ball, after the dig or bump pass. It is the setters role within the game to determine the tempo and the offensive tactics of the game depending on the placement of their set, whilst projecting the ball high enough and into an accurate position for their teammates to hit the ball into the opponent’s court by the third contact. (McLester & St. Pierre, 2008).

A setter must be physically and mentally agile and sure of themselves, as they need to place themselves in the balls line of fall and at the same time, decide how to place their hit to tactically determine the rest of the play. Being able to delay the physical preparation of ones body until the last second before the contact phase of the set also allows the setter a slight disadvantage over their opponents, as they have little time to read the body and determine the type of set about to be played (Ridgeway & Wilkerson, n.d.).  The set both slows the speed of the ball upon contact and then projects it forward or backward at a new controlled speed as determined by the setter.

Although the set looks like a simple manoeuvre, executing a successful overhead set relies greatly on the placement of the setter’s feet, hips, upper body and most importantly the elbows, wrists and fingertips.

The Big Question:

What are the biomechanic factors that influence the initiation of a volleyball set?

In any game of volleyball there are numerous factors that take place prior to and during a volleyball set that influence both the player and the play of the game and how the set is executed, each of which need to be discussed determining how to effectively set the ball. However, as shown by Image 2 (below) majority of the biomechanical influences occurs prior to contact with the ball, which occurs briefly at the last second. Forces such as acceleration, gravity, and projectile motion. Arguably the most influential factor on a game of volleyball however, is the concept of displacement. 

Displacement is a quantity that describes the change in position of an object from a beginning to end point, without concern for the total length of the path travelled (Blazevich, 2012). In a game of volleyball displacement affects the ball and each player, who begin in their designated position on the court but are immediately displaced across the court to play their designated role as the game begins. The ball is also continuously displaced as it moves around the court between players and back and forth over the net.

Acceleration & Velocity are two factors that are directly proportional to each other, where velocity is the rate(m/second) that an object is displaced in a given direction over a period of time, and acceleration is the rate of change in that velocity (Blazevich, 2012). Acceleration and velocity are both crucial factors that determine the skills of a 'good setter' in volleyball, as coaches want their players to be able to determine for themselves if they can reach the distance needed to travel to the ball before it reaches the ground (e.g. their velocity) and to be able to accelerate their quickly. 

The volleyball moves in two dimensions during a game, both forwards and upwards and is influenced by forces such as gravity and projectile motion.  Projectile motion is when an object moves in a free fall effect with an initial horizontal velocity, and is thereafter influenced only by the forces of gravity and air resistance, until it is affected by an external force (Blazevich, 2012). It is a setters job to interrupt the force of gravity and the projectile motion of the ball with enough of their own force to push the ball upwards and forwards in a new projectile motion, towards their target.

Newton's Laws each play a role in volleyball as well: 

Newton's First Law: Inertia: An object will remain at rest or continue to move with constant velocity as long as the net force equals zero.

Newton's Second Law: Acceleration: The acceleration of an object is proportional to the net force acting on it and inversely proportional to the mass of the object. 

Newton's Third Law: For every action there is an equal and opposite reaction.

Image 2 Source: Volleyball Techniques for Beginners (2014)

Acknowledging and combining these theories results in:

When a volleyball is hit (displaced), the ball will react equally and oppositely to the force applied to it (Newtons Third Law) and will then travel at the same constant velocity (Newton's First Law) proportional to its mass (Newton's Second Law). Its projectile motion will continue, until it is again influenced by another external force, such as another players hands, where impulse momentum theorem begins.

Impulse Momentum Theorem is possibly the final and most important piece of feedback that a setter receives when making contact with the ball and when releasing it. As the momentum of an object is conserved over a collision, the momentum of an object will change in proportion to the sum of applied impulses; therefore the longer amount of time that a large force is applied to an object the greater amount of momentum it will have (Blazevich, 2012).

The Big Answer: It is from here that the above biomechanical factors directly influencing the setter begin to fall together to form the initiation and contact phase of the volleyball set. As the ball is received, the setter is attempting to minimise the amount of contact time and therefore the transfer of momentum from the ball to the hands, and project enough force onto the ball to change its projectile motion towards either their teammates or the oppositions side of court. If a setter has contact with the ball for too long, not only does the ball lose its momentum but the setter is called for an 'illegal carry' -similar to catching-  of the volleyball. It is this reason why setters are instructed to contact the ball with only their finger tips, accumulating the most force through the angular 'flick' achieved by flexion then extension of the elbow and the dorsiflexion of the wrists, into the fingertips. 

The Sub Questions:

What physiological factors make a 'biomechanically good' setter?

Whilst volleyball players are allocate their role based upon the skill they are required to execute and their position on the court, it has become apparent that some athletes simply posses physical attributes that allow them to perform better biomechanically at setting. USA Volleyball (USAV), the national governing body for volleyball in the USA, identifies the ideal setter as typically being tall, left handed and athletic with a good vertical jump (Kane-Hopton, 2014). 

It has already been identified that an effective setter must be fast to move in a direct line, and agile to move from side to side to reach the fall of the ball in time in hope of creating a 'better ball' (Kane-Hopton, 2014).

A tall setter allows the team to theoretically have a seventh player on the court. As setters typically play at the net on the front right of the court, being tall allows them to be an effective blocker should the play become defensive, increasing their value to the team. This is also assisted if the setter has a large vertical jump, allowing them to produce a larger force and momentum from their jump and transfer this onto the ball.

As setters generally play toward the right hand side of the court facing towards the left, a left handed setter has a greater chance of being able to contact the ball on the second hit and produce force with their dominant, outside, left hand aiming to hit or dump the ball over the net (Kane-Hopton, 2014). It is possible to train right handed setters to use their left hand, although interrupting their internal logic pattern takes time, may be detrimental to their overall skill performance but, should be introduced from an early age. 

What affect does timing have on an individual’s ability to apply force on the ball during a volleyball set? 

There are numerous timing factors that a setter must take into account as  a part of their decision making in order to effectively execute a playable volleyball set. The player needs to judge the time to reach the ball and  the contact time necessary to apply suitable force and projectile motion upon the ball, pushing it upwards and towards their teammates or over the net, as a kinetic chain in a throw like motion from the feet to the finger tips, without reducing the level of momentum. 

By being able to read the velocity at which the oncoming ball is travelling, the setter is able to determine the necessary rate of acceleration needed for them to reach the ball prior to it reaching their optimum setting level (generally approx. 30cm above the forehead). Should the setter reach the position too late, they contact the ball with little preparation in directing the ball with the desired amount of force for their intended outcome. However being prepared too early allows the opposition time to read how the body is being prepared and aligned, so they can judge the type of set that is about to be played and arrange their defensive lineup as confirmed by Williams (2009). 

Image 3 Source: USC Trojans, (2014).

Do any upper body kinematic differences occur when preparing for a front set compared to a back set? 

The back set is a technique used by experienced setters that pushes the ball back behind the setter, in the opposite direction to what they are facing. Generally this opens up the play and is slightly harder for the opposition to read, as the preparation phase is similar to a front  set but the contact and follow through phases are completely different. During a back set, the ball is projected much higher than a front set, but closer to the setter and the middle of the court (see Image 4). 

Image 4 Source: Volleyballform.com (n.d.)

A study conducted by Ridgway & Wilkerson (n.d.) analysed the degrees of movement in the joints of the body, during the preparation, contact and follow through phase of a front set and a back set, and found that overall joints experienced greater angular displacement during a backset (Ridgway & Wilkerson, n.d.). The study found that in both sets, the three most active joints from preparation phase to follow through were the shoulder, elbow and knee, whilst the rest of the joints were similar between the front and the back set, as shown by the table below highlight the mean degrees of motion within the joints. 

Image 5 Source: Ridgway & Wilkerson (n.d.)

When viewing a backwards set in motion, it is no surprise that the shoulders experience the most rotation as the arms direct the ball upwards and backwards simultaneously, guided by bent knees and a slightly arched back and neck.  The main concern established through this study is that such large degrees of displacement in the body, again make it easier for the defence to determine the play. It was suggested that the setter should look at minimising the differences in body position between the front and back set, and perform these adjustments at the last minute so to inhibit the defences opportunity.

How can we further use this information?
The biomechanical principles discussed would be to any sporting coach or participant that utilises a throw like movement pattern of the kinetic chain, to take the force produced by the feet and transfer this through the body and onto the ball at a desired velocity towards a target. Sports such as netball directly utilise this transfer of force and momentum to produce shots at goal, where the shooter bends and the knees, through to the shoulders and then the extension of the elbows and finger tips upon the release of the ball, directing the ball into the netball goal. 

Effectively overcoming the general biomechanic forces that are applied to the body during sport is a skill that all sporting participants need to be proficient at as it allows them to efficiently maintain this over an extended period of time.

References:

Blazevich, A. (2012). Sports biomechanics the basics: optimising human performance. London: Bloomsbury

Federation Internationale de Volleyball(FIVB).,(2014). FIVB.

Retrieved 14 June 2014, from http://www.fivb.org/EN/FIVB/

Kane-Hopton, P. (2014). Recipe for a Setter. Teamusa.org. Retrieved 15 June 2014, from http://www.teamusa.org/USA-Volleyball/Education/Coaching-Education-Programs/Resources/CAP-II-Articles/Recipe-for-a-Setter

McLester, J., & St. Pierre, P. (2008). Applied biomechanics (1st ed., p. 156). Belmont, CA: Thompson Wadsworth.

Ridgway, M., & Wilkerson, J. (n.d.). A Kinematic Analysis of the Front Set and Back Set in Volleyball (1st ed., pp. 240-247). Denton, Texas: Texas Women's University. Retrieved from http://volleyball.qc.ca/sites/default/files/volley_files/FORE/FORE_KinematicAnalysisFontSetAndBack.pdf

Williams, A. (2009). Perceiving the intentions of others: how do skilled performers make anticipation judgments?. Progress In Brain Research, 174, 73--83.

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