Main Biomechanics behind the Volleyball Dig

Angle of Incidence:

Before the angle of incidence is gone into detail it must be made aware that when a ball makes contact with an object (bat, ground, wall or body part) it doesn’t lose energy, the energy is converted into other forms (Blazevich, 2010). “Coefficient of restitution describes the proportion of total energy that remains with the object after collision (Blazevich, 2010, p. 117)” This energy that remains determines how high the ball is to bounce after contact, after contact with the forearms the volleyball will rebound quicker if the platform of the forearms is smoother (Hede, Russell & Weatherby, 2011). The smoother and more locked the elbows and wrists are the more accurate the ball is at being performed at the correct angle (Hede et. al., 2011). The angle of reflection is greater than the angle of incidence which is the flight of the ball when it comes over the net (Blazevich, 2010). Meaning that for the ball to go in the air (the dig stopping the ball hitting the ground and preparing for a set) (Keeling, 2007) the ball must be hit from directly underneath the 90 degree angle is best as mentioned earlier.

 

Kinetic Chain – Push-like motion:

 



Image 2: Visual imagery for kinetic chain of the volleyball dig. Source Unknown

Video 1: Natalie Schmitting demonstrating a volleyball dig using the push-like motion. (About.com, 2012).

The kinetic chain is also referred to as the summation of forces, which our body can produce if the joints and next movement from the body is performed at the right time. This is where the volleyball dig can differ in technique; the ‘correct technique’ uses a push-like motion which is portrayed in image 2. The figure is using their legs for the strength, and moving the shoulders at the last bit just before contact with the ball to achieve the correct angle. This motion uses all parts of the body to achieve the most power in the dig as can be seen in video 1 above where Natalie’s body extends at the same time.  The other technique is where the arms are used as levers as their axis of rotation is that of the shoulders (Blazevich, 2010). This technique only gets power from that of the rotational point of the shoulders whereas the push-like motion from Natalie gets power from the proximal joints in her dig.

Centre of Gravity and Base of support:

The centre of gravity is where the total weight of the body is thought to be concentrated (Encyclopaedia Britannica, 2014). This is more known as the belly button for most humans as it is the middle point of our body thus our mass. When setting up for the dig, Natalie from video 1 gets her body low before the ball has come into view. This helps her balance and gives her the spring from her legs which produce the power of the shot. Not only does Natalie get her centre of gravity low to help balance but as can be seen her feet are at a wide distance apart. This is her base of support and when this is lower it makes it harder for her to fall over when performing the shot.

 

 

Newton's Laws:

Newton’s first law: This is the law that all things will stay in motion unless acted upon by an external force. This is also inertia, where the ball in volleyball will continue to head towards the ground unless it is stopped by the arms. If this didn’t happen the ball would hit the ground thus scoring a point for the opposition.

Newton’s second law: Acceleration is dependent on the force and mass of the ball (The Physics Classroom, n.d.). This acceleration from when the ball comes off of the forearms is important as it needs to be fast enough that it goes high enough in the air for the next person to get ready and perform the set shot.

Newton’s third law: For every action, there is an equal and opposite reaction (Blazevich, 2010). This law applies to that of the ground rather than the ball in this instance. When a force is applied to something which does not move (the ground) an equal and opposite reaction comes off the ground. In the push-like motion which is used, the ground enables the force to be equal which is applied to it.