MAJOR
QUESTION
Georgia Downard
________________________________________________________________________________
The tennis serve is arguably one of
the most important skills in tennis. Beginning the play, the serve is the only
part of the game where players can have complete control in the way the skill
is executed. Completing the serve in the most optimal, efficient and effective
way possible is crucial for the player’s game performance. The tennis serve is
a complex stroke which is chracterised by a series of segmental rotations
involving the entire kinetic chain (Kovacs & Ellenbecker, 2011). The
ultimate aim of a tennis serve is to hit the ball using an overarm action into
the cross court service box on the opposition’s side of the court, making it as
hard as possible to for the opposing player to return. Therefore, players are
continually being challenged to increase their serve velocity and use a variety
of different serves in order to gain an edge over their opponent (Fleisig,
Nicholls, Elliot & Escamilla, 2003). There are many biomechanical
principles that underpin the tennis serve, although carrying out the serve may not
always appear to be biomechanically favorable due to the organismic, environment
and task constraints (Davids, Button & Bennett, 2008). The tennis serve is
considered to have four main phases, including the:
1. Preparation
2. Wind Up
3. Force-generation
4. Follow through
Other than the preparation, all
three phases consist of important biomechanical principles which strongly
influence both the speed and accuracy of the tennis serve. Throughout this
blog, these principles will be discussed and answered in order to find out what are the most optimal biomechanics for speed and accuracy in a tennis serve.
PREPARATION PHASE
The preparation phase primarily
consists of the mental set in which the athlete prepares mentally for the skill
he/she is about to perform (Hopper, 2001). During this phase, it is important that
the performer understands ball placement, and the opponents limitations. Performers
should prepare their body in order to execute the next phase effectively. For a
right hand performer, a good base support with the left foot angled diagonally
across the court, with the right foot parallel to the base line. The performers
shoulder and trunk should be rotated across to the left hand side of the body. Player’s
mental state needs to be focused, with eyes on the target, maintaining a
relaxed body position. Performer’s preparation plays an important role in the effectiveness
of the execution of the serve in the next phase.
WIND UP PHASE
The purpose of the wind-up is to
store elastic potential energy or strain energy. Strain energy occurs because
the athletes muscles are stretched, the elastic recoil of the athlete’s muscles
convert the strain energy into kinetic energy, thus generating a tremendous
amount of force and momentum (Carr, 1997). The performer moves their arms in a
constant motion to release the ball, whilst rotating the racquet around the
body in a simultaneous motion. The wind up phase also incorporate Newton’s
third law “Every action has an equal and opposite reaction” (Blazevich, 2012). The
performer tosses the ball into the air, and the arm which is left in the air to
create an equal and opposite force with both arms. The action of the ball toss
arm, equals out the action of the racquet arm. This is so the racquet arm does
not initiate unwanted angular momentum.
The rate of force development, peak
force and torque are mechanical factors that collectively are often referred to
as load (Elliot, 2006). Performers who are able to increase the amount of load
generated through their serving technique, are able to increase their serving
speed. If a performer wished to serve the ball at a quicker speed, they need to
be able to modify their technique effectively so the rotation of the major
muscle groups (Hips, Shoulders and Upper Legs) are quicker. Using the bodies
Kinetic chain, enables this.
The kinetic chain can be defined as the synchronization
of single actions about numerous joints at the same moment with kinetic chain
movements being able to be open as either a push like movement or a throw like
movement (Blazevich, 2012). It is where linked muscle groups perform rigid
movements to create a greater force summation (McLester & Pierre, 2008). The
tennis serve as a whole, consists of a kinetic chain. Both types of the kinetic
chain movements are used in the tennis serve, as they both serve as key sources
of power.
Figure 1: Roger Federer Tennis Serve – Retrieved from (https://encryptedtbn2.gstatic.com/images?q=tbn:ANd9GcQR5c680jesC4Z6VsL0ljfJboGLwP7IDd4hbNImceXedGi4YlYFUg)
Figure 2: Pete Sampras Tennis Serve Sequence –
Retrieved from
The above figures show both Roger
Federer and Pete Sampras performing a serve. A kinetic chain motion is being
performed, as both pictures demonstrate the whole body momentum to produce
power. Figure 2 demonstrates a series of pictures showing Sampra, and in picture
three he begins to gain momentum and power by bending his knees, and beginning
to rotate both his shoulders and core. In further images, it is noticeable that
the racquet does not do too much, but Sampra’s legs begin to push off the
ground, rotation of his torso in the direction of where he is hitting the ball,
and his shoulder, elbow and wrist is coming up over the racquet. T
The biomechanical principle behind
this wind up phase, is the use of “Elastic potential energy”. According to
Blazevich (2008) Tendons are highly elastic, which means they store energy when
they are stretched by a force and recoil rapidly. Storing elastic potential
energy, and then converting into whole kinetic energy is the main purpose of
the wind up phase. Gaining the most speed and accuracy within a tennis serve,
means that the kinetic chain needs to be a constant movement phase, with no
pausing throughout the continual motion. The generation of power begins with
the feet making contact with the ground, and power coming up through the torso,
through the shoulders and wrists. This is when the ball makes contact with the
racquet, and this power would end.
Figure
3: Progression of the kinetic chain throughout the tennis serve. Retrieved
from (http://www.tenetfloridaphysicianservices.com/blog/tennis-injuries)
FORCE GENERATION
Force generation includes all three
of Newton’s laws. To gain air, the performer must apply an explosive thrust
with their legs against the ground to exert a force which exceeds their own
body weight (Hopper, 2001). This is demonstrating the use of Newton’s third
law, as explained earlier. The next key element involved with the third law, is
the hyperextension of the spine and torso. The athlete’s legs counteract the
angular momentum induced by the backwards flexion of the spine and striking arm
action by moving to the rear of the player. The hips move forwards also as a
result of Newton’s third law because the upper and lower body move backwards,
thus balancing the action (Hopper, 2001).
Force generation also includes
Newton’s first law: An object will remain at rest or continue to move with
constant velocity, as long as the net force equals zero (Blazevich, 2008). Once
the ball has made contact with the racquet, newton’s first law is applied.
Newton’s second law states that: The acceleration of an object is proportional
to the net force acting on it and inversely proportional to the mass of the
object (Blazevich, 2008). The mass of a tennis ball is constant, and due to the
equation of acceleration which is calculated by how fast the mass reaches its
top speed, rather than its actual top speed, meaning that the more force the
performer applies against the ball, the greater the acceleration. All three
laws play an important role in force generation.
Torque, also known as moment of
force is the force acting at a distance from the production of angular acceleration
(Blazevich, 2008). The rotation of the shoulder, has an impact on the speed of
the serve. This influencing factor is due to the racquet arm rotating around
the axis point of the shoulder, therefore this generates torque. The further the distance to travel from the
end point of the racquet to the contact point with the ball the greater the
moment of force, this is due to further rotation and further distance to gain
momentum (Blazervich, 2008).
Figure
3: Representation of the tennis racquet as a lever. (Retrieved from: http://tt.tennis-warehouse.com/showpost.php?p=5309329&postcount=124).
An example
of a third class lever is shown above in figure three. A lever is a mechanical
device used to move, or rotate around a fixed axis point. (Wuest & Fisette,
2012). The tennis serve uses the third class lever system, as the racquet is extended
to the fullest, generating the greatest force. Both the arm and the racquet are
defined as third class levers. According to Wuest and Fisette (2012) This lever
is a third class lever movement with the force being between the fulcrum and the
resistance, the favors range of motion and speed. This example is represented
above in figure three. The Levers are
essential in the tennis serve when producing force and speed.
FOLLOW THROUGH
The follow through phase allows the body to decelerate
with the shoulder rotation and forearm pronation continuing to help ball
accuracy (Kovacs & Ellenbecker, 2011). This is followed by the finish stage
where the feet return to the ground creating an eccentric and horizontal
breaking force, with the centre of mass shifting forwards (Kovacs &
Ellenbecker, 2011). A good follow through, will allow the performer to
be prepared for the return shot.
THE
ANSWER
Biomechanical principles play and
important and influential role within the speed and accuracy of a tennis serve.
If these biomechanical factors are understood and applied effectively, the
speed, accuracy and overall performance of the tennis serve can be vastly
improved.
It is vital to understand the
importance of all four phases, and the biomechanical principles associated
within. The force generated by the legs and the torso, is influential for the
force executed within the serve. The kinetic chain needs to have a free flowing
motion with no pauses, so that optimal summation of force and accuracy can be
achieved. If this action is not smooth and sequential, it can have effect on
the performance of the serve as the force generated through the body will not
transfer into the ball speed and serve.
Both the arm and racquet acting as
levers, assists the performers generated force in the serve. The mass of the
racquet has a massive influence of the torque generated and the production of
speed. This is due to the shoulder rotation and the force that can be obtained
from the kinetic chain and the motion range of the levers. Both torque and
levers are relevant for the performer to produce the greatest amount of speed,
as this will increase distance between both the axis and the contact point.
Newton’s laws are crucial for
greater performance in the execution of the serve. Newton’s first law is
important as the racquet makes contact with the ball in the force generation
phase. Newton’s second law is also involved within this phase, as it allows the
performer to understand the force which is required to execute a effective
serve. It is also essential when comparing the speed of the serve, as the ball
is completely dependent on the force which is applied as the ball has the same
amount of mass. The third law is applied throughout the serving process as
there is always an equal and opposite reaction. The greater force which is
applied through the feet on the ground will result in better performance as
force will transfer through the kinetic chain.
A variety of constraints such as;
environmental, task and organismic constraints can still effect an athlete’s
performance, no matter if all the biomechanical principles are applied. Performers
also have different abilities when applying the biomechanical principles, which
constantly effects speed and accuracy of the serve. Studies have shown that if
biomechanical principles are understood and attempted, speed and accuracy of a
performers tennis serve still can be improved. It is important to recognise a
variety of different constraints in regards to the learner when teaching the
tennis serve.
HOW
ELSE CAN WE USE THIS INFORMATION
Understanding biomechanical
principles in regards to speed and accuracy is crucial for the performance of
tennis players. Both coaches and educators should be aware of biomechanical principles,
so they are able to apply them too any sport to enhance the athletes
performance. Understanding biomechanical aspects also allows to solve specific
performance issues in individuals. A slight change to the way a performer
lands, or rotates their body can enhance the performance outcomes hugely. The
main concept of the tennis serve is the generation of force. Force generation
can be applied in many different sports, including individual and team.
Understanding biomechanical principles
can help determine the efficiency of a performers movement and skill execution.
Biomechanical principles are often able to be transferred between sports, and
it is vital that educators and coaches have an in-depth understanding on how to
apply them within different movement skills, so they can enhance optimal
performance within students and athletes.
Carr, Gerry. (1997). Mechanics of Sport: A Practitioner’s Guide. Windsor: Human Kinetics.
Davids,
K., Button, C., & Bennett, S. (2008). Dynamics
of skill acquisition: A constraints led approach. Human Kinetics.
Fleisig, G., Nicholls, R., Elliott, B., & Escamilla, R. (2003). Tennis:
Kinematics used by world class tennis players to produce high‐velocity serves. Sports Biomechanics, 2(1), 51-64.
Davids, K., Button, C., & Bennett, S. (2008). Dynamics of skill acquisition: A constraints led approach. Human Kinetics.
Hopper, T. (2001). Biomechanical Analysis of the Tennis Serve Greg Emery 9707553 PE 117
Kovacs, M., & Ellenbecker, T. (2011). An 8-stage model for evaluating the tennis serve implications for performance enhancement and injury prevention.Sports Health: A Multidisciplinary Approach, 3(6), 504-513.
Sandercock, T, G & Hubb, M. 2008. Force Summation between Muscles: Are Muscles Independent Actuators? American college of sports medicine.
Wuest, D., Fisette, J., (2012) Foundations of Physical Education, Exercise Science, and Sport, (17th Edition) New York.
