The Tennis Serve The tennis serve is the stroke that puts the ball in play and is often referred to as the most important stroke in the game of tennis. It has become a principle weapon of attack and is used to place the opponent on the defensive by forcing a return from the weak side or by moving the receiver out of position. A good strong serve can sometimes be the basis of winning a game of tennis. I have included eight picture sequences to illustrate the tennis serve. Represented in picture A is the stance of the serve.
In this part of the serve, the person needs to take a position sideways to the net, about three or four feet to the right center mark behind the baseline. The left foot is two to three inches behind the line, the toes pointing toward the net post. The back foot is parallel to the baseline and spread conformably from the front. Pictures B and C represent the preparation phase. In these pictures, the execution of the ball toss is performed.
The ball toss is the key to a well-executed serve: a good release consistently places the ball in the proper hitting position. A poor release can throw off timing and ultimately cause a bad serve. In pictures D-F the action phase is represented. In picture D of the action phase, the elbow reaches a position slightly higher than the shoulder, then the elbow bends and the racket head drops down behind the back into what is called the back scratching position. In picture E, the ball should be at its maximum height of the toss before striking it.
In picture F, the last of the action phase, the movement of striking the ball is explosive in an upward and forward motion until contact Pictures G and H represent the follow through. In the follow through the action is performed up and out, not down, in the direction of the intended target area. The follow through is a natural continuation of the stroke. A good follow through will help prepare for the next step in approaching the net for a return. Kinematics is defined as the study of motion.
It is compiled of different bodily planes and different joint motions. In the beginning of the serve, during the stance (picture A), the feet are outwardly rotated. The hips and the trunk are extended. The left shoulder is slightly flexed along with the right shoulder and the shoulder girdles are slightly abducted. Both of the wrists are pronated with the elbows slightly flexed.
During the preparation (pictures B and C) the feet are still in an outwardly rotated position. The hips slightly abduct with the trunk still in full extension. The shoulders are abducted, with slight elevation of the shoulder girdle. Both elbows are extended, but the right wrist stays in a pronated position and the left wrist is supinated. During the action (pictures D-F) the right foot inwardly rotates along with it performing planter flexion but the left foot stays in an outwardly rotated position. The hips are adducted but then they shift to abduction.
The trunk starts in hyperextension then get fully extended and slightly rotate to the left. Both knees flex but the left knee extends while the right knee stays flexed. The left shoulder goes from flexion to extension while the right shoulder performs high diagonal adduction. The left elbow goes from extension to flexion and the right elbow goes from flexion to extension. The left hand goes from supination to pronation while the right hand stays in a pronated position. Finally, during the follow through (pictures G and H) the left foot inwardly rotates along with some planter flexion. The right foot inwardly rotates and goes back to a naturally flat position. Both hips are flexed along with the flexion of the trunk and it’s rotation.
The left shoulder remains in an extended position but the right shoulder follows through with the high diagonal adduction, while both shoulder girdles perform abduction. The right elbow slightly flexes but the left elbow extends. The knees go from flexion to a greater degree of flexion. The kinematics of the tennis serve is a complicated thing, it consist of many laws and principles. One law is the law of inertia and the principles deal with motion, force and projectiles.
These laws and principles can be applied to a skill, for example the tennis serve. The first principle deals with stability. This principle consist of smaller groups dealing with mass, friction, height of the center of gravity, position of the center of gravity, and base of support. The mass of the person in pictures A through H is of a certain weight. This mass or weight throughout the serve is considered to be constant. This observation is made because during the tennis serve the person performing the serve cannot gain or loss mass during the serve. Friction can be a major factor in a sport or game. The type of footwear available can help an althea to the point of better counter force when jumping or better traction for different surfaces.
A tennis shoe does not need to have great counter force because there is not a lot of jumping but traction is important because of different surfaces like clay, grass, and concrete. Each surface performs differently for each athlete so there should be a traction on the shoe to benefit sprinting forward but also being able to move side to side. Height of center of gravity is one important factor in good equilibrium. In the stance position of the tennis serve (picture A), the height of gravity is in the middle around the navel. This remains constant through the prep phase (picture C), but when the action phase starts (pictures D – F) the height of gravity moves up with the extension of the racket arm and trunk.
Then in the follow through (picture G, H) height of gravity starts to go down because of the descending motion of the racket arm and trunk. Position of center of gravity is another important part in good equilibrium. In the stance position of the tennis serve (picture A) the position of gravity is about two inches above the belt. Then in the prep phase (picture C) it moves upward about four inches above the navel. Next, in the action phase (pictures D – F) center of gravity moves three inches to the right of the navel and about four inches above the navel. In the follow through (picture G, H) the center of gravity is about four inches outside the body parallel to the belt line.
Base of support is the area formed by the outer most region of contact between the body and a support surface. During the serve (pictures A – D) the base of support is pretty much constant. It is just enough not to fall but good enough to push off of the surface. In picture E the base narrows a little because of the force of pushing off with the left foot. Pictures F and G, the base is wider then narrows and drops down and forward, this is because of momentum pulling the body forward into the follow through.
At the end the base of support is narrowed to bring the feet under the body for better equilibrium because the center of gravity is outside the body, this is to keep the body from falling. The first law of kinematics is the law of interia. This law has principles that deal with motion. Translatory motion is defined as motion moving in a straight line. Rotary motion is defined as motion moving in a circle.
Combining translatory and rotary motion in the tennis serve is shown by the rotary motion of the racket arm and the motion of the trunk in the follow through. Translatory motion is shown by the stepping forward of the trunk, legs, and partially of the racket arm. Continuity of motion is shown during the action phase (pictures D – F) with the tossing of the tennis ball while bringing the racket into a striking position and also extended the trunk and legs. This is all performed at the same time with no pause. If there was pause in any of these motions there would not be enough momentum to create a very effective serve. Momentum is the product of a body’s mass and linear velocity.
Momentum can be changed by changing direction. To produce an effect of momentum during the serve, since mass is constant, the velocity of the body must be increased. This is done by the extension of the racket arm along with the trunk and moving the center of gravity forward to produce a good momentum in striking the tennis ball, this intern with the racket striking the ball turns it into a force, this force is equal to the momentum of the body. During the action phase of the serve (pictures D – F) transfer of momentum is achieved by extending the legs, trunk, and racket arm. This is done because mass remains constant, so to increase speed the body must become longer to help contribute to the total body momentum.
In the tennis serve acceleration is proportional to force because mass in the body of the server is constant. So if the server has a great amount of acceleration then there will be a great amount of force when striking the tennis ball with the racket. Maximum acceleration is achieved by moving the whole body in a forward motion with continuity and timing. There are really no extraneous movements because most movements like the extension of the legs, trunk, racket arm, and the moving forward of the body are all extended to create greater body momentum. Timing is very important and should be practiced because it is probably the hardest thing to get down to create maximum acceleration and effective motion. In the serve the body’s radius is lengthened so according to the principle the rotation is shortened during the follow through phase, this is because with a lengthened radius the body has more area to cover.
This is sacrificed because greater momentum to where the ball must be hit is more important then rotational speed. This is illustrated in the action phase (pictures D – F) with the extension of the legs, trunk and racket arm. This shows the lengthening of the body’s radius. During the action phase of the serve never unsupported as seen in the pictures D – F. Both feet seem to be on the ground in constant support of the body, so this principle does not apply to this particular serve.
Although some people might actually, force a split second, become airborne during the serve, then this principle would apply. There are three major surface variations in tennis all with different counter force. Clay is the first surface, although it is somewhat soft is does not contain good counter force because it has a bad coefficient of restitution, which means it does not bounce back to original shape very well. Clay is also somewhat slippery so players must slide to position to hit the ball. Grass is another form of surface variation, it is also somewhat soft and does not have a very good coefficient of restitution but it is better then clay.
Grass also has a degree slipperiness and also requires the sliding into position. Finally, concrete is the last surface variation, it has no counter force because there is no give and no coefficient of restitution but concrete is not as slippery as the other two surfaces. During the action phase of the tennis serve (pictures D – F), the direction of counter force is projected down and back which in turn propels the server up and forward. This is done in a perpendicular manner to the surface so there will be no slippage. When the racket strikes the ball there are counter forces.
When the ball is in contact with the racket, the racket has mo …