What are the biomechanical principles that optimize the speed and accuracy of tennis serves?
The tennis serve is what starts every point of the match, therefore it is arguable the most important skill of a tennis players game. The aim of a serve is to hit the ball into the opponent’s service area and make it as difficult for the opposition to return the ball. The serve can be considered as one of the most attacking phase of the match. An athlete which has the ability to apply a large amount of velocity behind the ball has a greater chance of winning the point, due to the oppositions reaction time will have to be quicker to return the ball. Also being skilled enough to apply different variations of spin to the ball whilst in the serving action increases the difficulty to be able to return the ball. The tennis serve is considered to have four phases: preparation, wind-up, force-generation and the follow through. Other then the preparation phase each one of these four phases consists of very important biomechanics which influence the speed and accuracy of the tennis serve. Therefore this leads to the question “What are the biomechanical principles which influence the speed and accuracy of a tennis serve?”
The preparation phase
This mainly consists of mental mind set, where the player prepares for the shot in which he/she is about perform. There are a few little performance based actions which will help with the players ability to perform the serve to a high standard. Good base support, with the left foot pointing diagonally across the court, the right foot parallel to the base line (for a right hand players serve). The shoulders and trunk should be rotated across to the left hand side of your body; this is to prepare for the force production of the next phase.
The wind up phase
The purpose of the windup phase is to produce force summation,“the combination of forces produced by different parts of the human body. When a person is moving or attempting to move an object, several different parts of the body act together to maximize the force.”(Sandercock, 2009). The windup phase also incorporates Newton’s third law ‘every action has and equal and opposite reaction’. Once the player tosses the ball into the air, the arm is left in the air to create an equal and opposite force with both the arms. The action of the ball toss arm balances out the action of the racket arm, which means the faster the toss arm and torso are rotated the more force can be generated through the ball (Hass, R. 2011). Loading is classified as “the rate of force development, peak force, and torque are mechanical factors that collectively are often referred to as load”(Elliot, B. 2006). A player which is able to increase the amount of load generated through their serve technique is able to increase their serve speed. The way behind doing so, is to use the kinetic chain. If the player wishes to serve the ball quicker they need to modify their technique so they are rotating the major muscle groups quicker e.g. Upper legs, hips core and shoulders, by doing this the body needs to be prepared for high forces and quick speed movements.
The tennis serve consists of one big kinetic chain. Often when a player is having trouble with their serve, the problem can be found in the kinetic chain. 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, A, 2012, Pg 196).
To gain the most speed and accuracy in a tennis serve, the kinetic chain needs to be at a standard where there are no pauses throughout the motion. Elite servers utilize the entire body on the serve and also be very precise with the timing. The power of the serve starts from the feet making contact with the ground right through the torso, up through the shoulders, elbow, wrist and right till the very moment the ball makes contact with the racket. Throughout this motion is there is a pause, for example in the shoulder rotation, then all that momentum and kinetic energy gathered through the torso and legs has been lost.
Force generation
The force generation phase is conducted with the extension of the legs in a downward acceleration of the tossing arm. Once again, going by Newton’s third law, with the player driving his feet into the ground, the ground pushes back against the player with the exact same amount of force, causing him to gain momentum and producing a ground force reaction. Newton’s First law comes in to play during the force generation phase, the law states “An object will remain at rest or continue to move with a constant velocity as long as the net force equals zero” (Blazevich, A, 2012, Pg 44). Newton’s first law comes in to place once the ball has made contact with the racket in the force generation phase. “Once the ball is moving from the strike of the racket, its forward trajectory would continue indefinitely if the forces of gravity, friction from the air resistance or striking the ground and the force of the opposing player's racket did not stop it”(Haas, R. 2011). Newton’s second law of motion “the acceleration of an object is proportional to the net force acting on it and inversely proportional to the mass of the object” (Blazevich, A, 2012, Pg 45). The acceleration is calculated by how fast the mass reaches its top speed, rather than its actual top speed. Haas (2011) stats “During your serve, the mass of the tennis ball remains constant. Therefore, you can see in this equation that the more force you apply to the constant mass of the tennis ball on the serve; the greater the acceleration of that serve will be until it reaches its top speed”.
The whole body is made up of levers created by the human bones and muscle. The tennis serve is a form of the third class lever system, with the racket are extended to its fullest to create the longest possible lever and therefore creating the greatest force. The serve is classed as a third class lever due to the force being between the resistance and the fulcrum. The third class lever is often the one which is found in most sports, due to these levers being better at generating force due to the positioning of the fulcrum. By increasing the length of the lever, this then increases the range of motion at the levers end, therefore increases the speed of the racket (Ackland & Elliot, 2009). This is why it is recommended that the server has a fully extended arm whilst performing their routine, because the principle of leverage states that the velocity at the end of a long lever is faster than the velocity at the end of a short lever, and that the end of a lever will move more quickly than any other point on the lever. Whilst doing this it increase the inertia gathered by the racquets, therefore making it feel heavier and increasing the inaccuracy of the motion. This is why beginners often start with a shortened racquet to decrease the inertia and make it easier to perform the skill
The Magnus effect comes in when the ball is spinning through the fluid, which in this case is the air. "The fluid near the ball's surface that is travelling towards the flow will be impeded and thus slows down, increasing fluid pressure. In contrast, the fluid near the opposite surface of the ball that is travelling away from the flow will be speeded up lowering fluid pressure locally. The pressure difference across the ball then leads to a net force that curves the ball towards the low pressure side." (Thomas, 2012)
Figure 1: The spinning of a tennis ball as it travels through the fluid (the ball is traveling the direction of the arrow in the bottom left corner, whilst it is spinning around an axis at an angle of
A slice serve is when the player applies spin to the ball which causes the ball to spin around like a coin would when you flick it (
During this video Florian Meier (2012) described how the kinetic chain is used throughout tennis. Describes how using different body parts at the same time are used to create kinetic energy. It then goes on to describe how energy is transferred from linkage to linkage. This also answers the question to why tennis players don’t have to be muscular to hit the ball hard, because the use of all the major muscle groups. Florian describes this kinetic chain as coiling and uncoiling all the body segments which are involved, the muscles and tendons work as a rubber band in this situation, with them getting stretched, energy gets stored, and then transferred to the next segment of the kinetic chain. The kinetic chain consists of 6 different body segments being, legs, hips, truck, shoulders, arm and the wrist.
Projectile motion refers to “the motion of an object (in this case a ball) projected at a angle into the air” (Blazevich, A, 2012, Pg 25).
Figure 3: gravity acts upon the tennis ball the same way, whether its dropped to fall freely or if it is hit in a horizontal line, in some cases the air resistance can become a factor, but mainly there is not a big enough breeze to make an impact.
“Trajectory is influenced by the projection speed, the projection angle and the relative height of projection” (Blazevich, A, 2012, Pg 25). When serving the ball at a reasonable high speed there is minimal room for error. The ball needs to be hit a couple of degrees below horizontal otherwise the ball will be served into the net or go to long. There is only 2-3 degrees between either of those two outcomes happening (Cross, R. 2004)
The follow through
The follow through is a natural continuation of the serving motion, a good follow through will always allow the player to prepare well for the next shot. In the serve the body's radius is extended so according to the theory the rotation is reduced in the follow through phase, this is because with a expanded radius the body has more vicinity to cover. This is sacrificed because superior thrust to where the object (The ball) should be stroked is more vital then revolving velocity (Ryu, et al, 1988).
The Answer
Therefore the biomechanical principles that are required to achieve optimum speed and accuracy in tennis serve are a good base support which allows the athlete to be confident in there serving stance. Force summation is used in the wind up phase of the serve to start producing momentum to go on an hit the ball. Newton’s third laws comes into effect when the ball is tossed up and the player goes to swing the racquet twisting his truck and pulling his left arm down for a equal force produced by both arms. One of the most important attributes to the tennis serve would have to be the kinetic chain, by conducting enough elastic energy throughout the kinetic chain of the tennis serve will increase the speed of your serve. The player who tend to serve the quickest use the kinetic chain to their advantage by having a fluent motion with no pauses, which allows no energy or force to be lost. To have the force generation phase result in producing large amounts of power for the serve Newton’s third law come in to action again when the player pushes off of the ground, and starts to gain momentum which helps produce the greatest force. Newton’s first law comes is when the racquet makes contact with the ball in the force generation phase. Newton’s second laws once again occurs whilst in the force generation phase, this allows the player to understand the force which is required to produce the right serve which is going to set them up for the point. One of the biggest factor which result in producing speed is the bodies levers and how they function. To produce the most speed and momentum you need to increase the length of the lever, meaning increasing the distance between the pivotal point (shoulder) and the contact point (middle of the racquet). A tennis player who understands the Magnus effect will have an advantage over their opponents, the player will be able to work with better angles and have superior control over the serve, making it more accurate. This also makes it more difficult for his opponent, because they have to take into account the spin and swing of the ball, making it more unreliable. The projectile motion and trajectory of the ball is how gravity acts upon the tennis ball throughout the serve. Not getting the right angle will cause the ball to be in into the next or go to long, there is only centre meters between getting it right or wrong. So it is now evident that with a better understanding about the biomechanical principles involved in the tennis serve, it will increase the outcome of the players serve, by being more accurate and producing more speed.
How else we can use this information
For any type of athlete it is always important to understand the importance of the biomechanics which are involved in the sports they are involved in and the sequences which they have to perform. This will therefore make it easier to perform the skill at a higher level and help solve specific problems to particular parts of the sport. The biomechanics which are involved in the tennis serve can very easily be related to other sports such as badminton, table tennis, lacrosse, baseball and cricket. The Magnus effect is involved in any type of sport which involves a ball being penetrated through the air. The Magnus effect allows coaches to analyze the effectiveness of each baseball pitch or every cricket bowl. With the constant improvement of technology now days, coaches are able to look at different techniques in super slow motion to analyze the biomechanics and therefore determine how to produce the fastest ‘fast ball’ all by the improvements of biomechanics that the player uses. This is why the athletes which understand the biomechanics the best will often come out on top at the end of each game and continue to improve by gathering further knowledge about the biomechanics of a chosen sport.
References
Ackland, T, R. Elliott, B, C. 2009. Biomechanical levers. Applied anatomy and biomechanics in sport. (2nd Ed.) 3 (2) 74-126. United States of America
Blazevich, A, (2012), “Sports biomechanics, the basics: Optimising human performance”, A&C Black, Pp 44-202.
Cross, R. 2004. Ball Trajectory. Factors influencing the flight of a ball. 1 (45). 368.
Elliott, B. 2006. Biomechanics and tennis. British journal of sports medicine. 40(5): 392–396.
Hass. R . 2011. Tennis and Newton’s law. Live strong. 21 (3). 132. http://www.livestrong.com/article/425371-tennis-newtons-laws/
Ryu, R. McCormick, J. Jobe, F. Moynes, D. 1988. An electromyographic analysis of shoulder function in tennis players. American journal of sports Medicine. vol. 16 no. 5 481-485
Sandercock, T, G & Hubb, M. 2008. Force Summation between Muscles: Are Muscles Independent Actuators? American college of sports medicine. Pp 184. 5 (6).
Thomas, R. 2012. Spinning the perfect serve. Plus Magazine. 2 (4). 144. America
Youtube: Tennis tips. The kinetic chain http://www.youtube.com/watch?feature=player_detailpage&v=7Lq7Io2nHh
