Biomechanics Blog

How can an understanding of the biomechanics behind the volleyball spike be used to better performance outcomes?

 

The volleyball spike is one of the most important skills during a game of volleyball. The aim of the spike is to hit the ball into the opposition side of the court using an overarm action at the top of a jump. The harder the spike is hit, the less time the opponent will have to react to the ball, thus increasing the likely hood of an error. There are various types of spikes that can be performed during a game. These spiking types are the outside spike, the middle spike, and the backcourt spike. These three types of spikes all work on the same biomechanical underpinnings, with the only real difference being in the length of the approach. Each spike has three phases, the approach, the spiking motion and the contact and follow through. For the purpose of this blog; the outside spike will be the main focus, as it is the most commonly used spike in a game. Throughout this blog, the biomechanical principles of the outside volleyball spike will be identified, and then from that, which biomechanical principles a coach could focus on to improve performance outcomes will be discussed.

Approach:
 

During the approach phase of the volleyball spike, players are looking to reach maximum vertical velocity by applying maximum vertical ground reaction force during their jump to be able to spike the ball at the highest point possible (Blazevich, A. J. 2010). To do this players must first overcome their inertia, which means that they will have to apply a certain amount of force in order to change their velocity (Blazevich, A. J. 2010).

When a person has momentum, their inertia remains the same, meaning they must exert the same force to change their velocity. To overcome inertia and gain momentum as quickly as possible, the athlete must apply as large of force as possible over a long time, and this is called impulse (Blazevich, A. J. 2010). The greater the impulse, the greater the change in momentum and this is called the impulse-momentum relationship (Blazevich, A. J. 2010). Since our mass is changing, our velocity should change also (Blazevich, A. J. 2010). All this information is relevant to the first stage in the volleyball spike approach, which is the initial run up.

The aim of the run up is to gain as much horizontal velocity as possible in the short three to four step run up. This energy from the horizontal velocity of the run up is then convert to vertical velocity when the athlete exerts force into the ground, causing their momentum to shift vertically for a jump. This happens because of Newton’s third law that states that for every action, there is an equal and opposite reaction (Blazevich, A. J. 2010). When the athlete applies downwards force, the ground exerts an equal and opposite reaction force which stops the foot from sinking into the earth (Blazevich, A. J. 2010). This opposite reaction force is called the ground reaction force or GRF. This is seen in figure 1.  During actions such as running and jumping, we apply both vertical and horizontal force into the ground (Blazevich, A. J. 2010). This vertical and horizontal force will change dependent on whether we want to run horizontally or jump vertically. If the person exerts an equal and opposite GRF strong enough to overcome their inertia, then the force will accelerate our velocity whether it be vertical or horizontal (Blazevich, A. J. 2010).

(Figure 1: Newton's Third Law, Ground Reaction Force  (Retrieved from: Blazevich, A. J. 2010 pp.45)

When our foot first hits the ground during running, we initially apply a force or impulse in the forward direction, which according the Newton’s third law, will exert force back towards us and slow us down (Blazevich, A. J. 2010). It is only later that we apply backwards force that we are propelled forwards (Blazevich, A. J. 2010). This is called braking and propulsive impulses, and will play a huge role in the jumping phase of the approach.

Figure 2: Braking and Propulsive Impulses (Retrieved from: Blazevich, A. J. 2010 pp.55)

Spike:

The Kinetic chain is a linkage of body segments performing movements together to create force summation (Blazevich, A. J. 2010; McLester & Pierre, 2008). The kinetic chain consists of two different kinetic chain patterns; the push- like pattern and the throw- like pattern (Blazevich, A. J. 2010). The throw- like pattern involves the body segments moving sequentially with the momentum from the proximal segments transferring to the distal segments to produce force (Blazevich, A. J. 2010). This is different from the push- like pattern where all body segments move simultaneously in a single movement to produce force (Blazevich, A. J. 2010). The volleyball spike is a throw-like pattern.

The spike has three movement phases within it, the back- swing, turn-swing and forward-swing (Li-Fang, Liu & Gin-Chang, Liu, 2008). Each phase then can be broken down into different stage within the phases. The back-swing phase has a lead and pull, the turn-swing has a trunk turn and the forward-swing has acceleration and contact. This is shown in figure 3.

Figure 3: Back-Swing, Turn-Swing and Forward-Swing phases (Retrieved: from Li-Fang, Liu & Gin-Chang, Liu, 2008)

The back-swing phase is essential, as it results in potential energy being stored for use as kinetic energy during the forward-swing phase (Blazevich, A. J. 2010).  The turn-swing is the beginning of the kinetic chain, as a sequential acceleration from proximal to distal segments occurs starting from the shoulders, to the elbow and then to the hand (Li-Fang, Liu & Gin-Chang, Liu, 2008).

As describe before by Newton’s third law, for every action there is an equal and opposite reaction (Blazevich, A. J. 2010). This principle is the same during the motion of rotation, as for every angular motion there is an equal and opposite angular reaction (Blazevich, A. J. 2010). This is best explained during the basketball dunk, as the forward and downward rotation of the arm creates an equal and opposite reaction rotation through the legs (Blazevich, A. J. 2010). The legs do no have as much noticeable movement in them because they have a greater inertia, thus requiring more force to overcome (Blazevich, A. J. 2010). This concept is called conservation of angular momentum.

Due to lack of ground reaction force from the jump, the throw like kinetic chain movement must be balanced by the reaction of other segments of the body like the legs and the opposite arm (Li-Fang, Liu & Gin-Chang, Liu, 2008). This counter balancing in the air is the conservation of angular momentum as explained above. The arms forward and downward rotation creates an equal and opposite reaction rotation in the legs, and although the change is not to noticeable because of the greater inertia in the legs, there must small and minor adjustments mid air to ensure not to lose balance and land in a way that would increase the likelihood of injury (Li-Fang, Liu & Gin-Chang, Liu, 2008).

Figure 4: The full volleyball spike motion (Retrieved from: http://www.pinterest.com/pin/105271710012814223/)

Contact:

As a ball spins, the spinning ball grabs the air that flows past it because of the friction between the air and the ball, and this causes the air to start to spin with the ball (Blazevich, A. J. 2010). As shown in figure 5, the left side of the spinning ball collides with the oncoming air and slows down (Blazevich, A. J. 2010). The right side of the ball creates a pressure differential directed from left to right, therefore causing the ball to swing to the right (Blazevich, A. J. 2010).

Figure 5: The Magnus Effect (Retrieved from: http://ellieslicesbagels.files.wordpress.com/2014/05/curveball.jpg)

This principle is called the Magnus effect (Blazevich, A. J. 2010). This same principle applies when there is topspin applied to a volleyball. When there is topspin applied, the ball will swing downwards. The more spin applied, the more downward swing will occur. A spinning volleyball, because of the lift forces produced by the Magnus effect, has the advantage of being able to be hit with greater velocity, higher above the net, and at flatter angles over the net than balls with little or no spin while still landing in the court on the opposite side.

The Answer:

There are many biomechanical principles that make up a biomechanical model of the volleyball spike. Each of these biomechanical principles can be focused on to improve the performance outcomes of a player.

During the jumping phase, it is important not to have too much horizontal velocity because this velocity will cause your body to jump into the net, which is a violation and will reward the opposition the point. But it is important to have some horizontal velocity, as this will allow for more force to be applied during the spike because the horizontal force during the jump will be exerted through the ball. Therefore it is imperative that the athlete is applying the right amount of braking impulse during the jump to slow their horizontal velocity enough to ensure they do not jump into the net but at the same time, have enough horizontal velocity to exert maximum force through the ball.

In order to create as much velocity through the ball during the spike, the player should take full advantage of the potential energy created during the back and turn-swing phase(Li-Fang, Liu & Gin-Chang, Liu, 2008). By focusing on ‘pulling’ back as far as possible during the back-swing, the player will create more potential energy to be converted to kinetic energy later on in the movement. This ‘pulling’ allows for more time for the ‘trunk turn’ to occur during the turn-swing phase, thus increasing the force created through the turn that can be summated through the kinetic chain (Li-Fang, Liu & Gin-Chang, Liu, 2008).

Finally, a coach should focus on the technique used to create topspin on the ball. As state before, the more topspin on the ball allows the player to hit the ball at greater velocity, higher above the net and at flatter angles. Thus creating as much topspin as possible is imperative to performance outcomes, as being able to create more velocity through the ball will further reduce the opponents’ time to react. According to a study done by Baudin, Peter F. and Wu, Tom (2004), there are two different techniques that produce topspin onto the ball. The first technique shows that the spin is produced by the palm of the hand first contacting the middle of the ball followed by a wrapping action of the fingers over top creating the torque. The second technique shows the fingers of the hand contacting first, at a point high on the ball to create torque, with the finger contact followed by the palm of the hand striking the middle of the ball. The first technique produced a mean ball angular velocity of 39.02 rad/s, whereas the second technique produced a mean angular velocity of 41.42 rad/s. while the difference between the two techniques may be small, that could be the difference between the ball landing in or out.

Clip 1: How to Spike a Volleyball (in Slow Motion)  (Retrieved from:https://www.youtube.com/watch?v=FMtUqoxfR50)

How else can we use this information?

With so many biomechanical principles being transferable from sport to sport, it is extremely useful for a coach to have an understanding of not only the biomechanical principles behind a sport movement skill, but also how they can then alter the player’s movements to better their performance outcomes.

From this identification of the biomechanical principles of the volleyball spike, it is easy to see how this information could be useful to other sporting areas. Sports that require either a jump or a throw-like kinetic chain could use this identification of the biomechanical principles, transfer it and then apply it in way that the coach see fit. Sports such as long jump, triple jump and high jump all work on the exact same principles discussed in the approach, with the difference being that the long and triple jump is looking for a balance between maximum vertical and horizontal velocity to increase the horizontal distance of the jump.

Understanding the kinetic chain and the importance that sequential movements can make will result in the greater force transfer thus resulting in a greater force at the release or contact phase of the movement is essential to a lot of sports. The throw-like kinetic chain transfers to a number of sports such as the tennis, badminton, cricket, baseball and basketball.

Although there may be a correct biomechanical model to a sport skill such as volleyball, it is important to note that due to task, environmental and organismic constraints; there will always be various differences to individual players performance outcomes. It is up to the coach to identify which principles can be applied and worked on within the individual technique to better their player’s performance outcomes.

Reference:

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

McLester, J., & Pierre, P. S. (2007). Applied biomechanics: concepts and connections. Cengage Learning.

Li-Fang, Liu and Gin-Chang, Liu. (2008). The Application of Range of Motion (ROM) and Coordination on Volleyball Spike. International Symposium on Biomechanics in Sports. Conference Proceedings Archive, 26.

Baudin, Peter F. and Wu, Tom (2004). An Examination of the Biomechanical Factors that Produce Spin on a Volleyball in the Skill of Spiking. International Symposium on Biomechanics in Sports. Conference Proceedings Archive, 22.