QSU6054

QUALITATIVE ANALYSIS OF HUMAN

MOVEMENT

TENNIS OVERHEAD TOPSPIN SERVES

LECTURER :

DR. ONG KUAN BOON

ALIFF BIN ABU BAKAR (M20122001748) MUHAMMAD NUR FIKRI BIN MOHAMMAD ZAINURI (M20122001746)

1.0 INTRODUCTION

The serve is one of the most important skills a tennis player must acquire in

order to have an effective attack. The primary objective of the serve is to direct the

ball into the service area on the opponents side of the court. The serve is an

effective offensive weapon because the ball can be hit with a tremendous amount of

velocity, thus reducing the opposition reaction time and consequently their ability to

return the ball. Variations of the service action can also cause the ball to spin. A slice

serve is used in order to gain an advantage via the unpredictability of a spinning

balls bounce. The serve can be broken down into the following four phases:

preparation, wind-up, force-generation and the follow through/recovery.

Biomechanical analysis of the skills involved in each phase, enables us to give

effective instruction and appropriate technical cues to improve the performance of

students and athletes.

Preparation

The preparation phase primarily consists of the mental set in which the athlete

prepares mentally for the skill he/she is about to perform. During this phase the

athlete determines the location and type of serve they are going to hit based on the

positioning of the opponent and their knowledge of the opponents limitations. In

addition the athlete conducts preliminary movements in order to prepare the body for

the motion required of the skill.

Wind-up

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 muscles convert the strain energy into kinetic energy, thus

generating a tremendous amount of force and momentum. During the course of the

windup the athlete weight is initially shifted from the front foot to the rear foot.

Concurrently the left arm tosses the ball; consistency is imperative to the

performance of the serve. It is important for a consistent toss, to have the left arm

extended throughout the toss. The action of the non-racquet and racquet arm is an

example of Newton‘s third law, which states that every action has an equal and

opposite reaction. The action of the left arm balances that of the right arm so that the

racquet arm does not initiate unwanted angular momentum. As the action of the

arms and torso occur the weight is shifted from the rear leg back to the front leg and

the knees are bent in order to store potential energy. This concept is known as

ground reaction force and will be discussed in greater detail in the force generation

phase. The action of the arms and torso to the rear is equal and opposite to the hips

shifting forward. The body therefore maintains balance and allows the body to flex

further backward, storing more strain energy and increasing impulse. The motion of

the racquet head is crucial in the development of power, consistency, and spin.

Force-generation

The striking action of the force generation phase is initiated via the extension

of the legs and the downward acceleration of the tossing arm. According to Newton‘s

third law, as the athlete pushes against the ground, the earth pushes back up

against the athlete with the same force, this is also known as a ground reaction

force. The upward motion of both the racquet and non-racquet arms are a form of

momentum transfer that helps to propel the athlete into the air by increasing the

amount of downward thrust exerted upon the ground. The ground pushes back up

against the athlete and the athlete becomes airborne. Dropping the tossing arm

serves a duel function, it initiates force generation along with hip rotation, and

increases the angular momentum of the racquet arm. The next key element of the

service action is the hyperextension of the spine and torso. Again due to Newton‘s

third law, the athlete 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. The rotation of

the trunk and arm shifts the angular momentum of the body forwards and the legs

are forced to compensate by also rotating forward. The abdomen is flexed and the

rear end and hips move backwards as a result of Newton‘s third law. The sequential

body movements of the hips, torso, shoulder, arm, elbow, forearm, wrist and racquet

simulate the action of a whip. The body is comprised of a series of segments, which

form third class lever systems. A third class lever is when the pivot point is at the end

of the lever and the force is generated along the lever arm between the fulcrum and

the resistance. For example, the elbow is a pivot point, the bicep attaches to the

forearm in front of the pivot and the resistance is the tennis racquet. Each of the

body‘s segments progressively become less massive and thus while the slower

moving, more massive segments (hip and trunk) rotate forward to initiate the force

generation the lighter body segments (arm, forearm, wrist and racquet) complete

their backward extension. Furthermore each of these body segments are third class

levers that become shorter in length. The combination of these two factors result in a

whip like action in which each of these segments sequentially accelerate, thus

producing tremendous racquet head velocity. This concept demonstrates the

importance of the wrist rotation as it forms the final accelerating segment that

produces racquet head velocity, hence service power.

The ball is contacted though the centre of the racquet and the athlete can do one of

the following:

1) Apply top spin by flexing the wrist over the ball

2) Cut the ball to the side by contacting the ball through the centre of gravity and

then flexing and rotating the wrist to the side of the ball inducing sideways rotation on

the ball. To help students visualize this action instruct the student to ―wrap the

racquet around the pole.‖ This action induces spin on the ball creating the Magnus

effect, which causes the ball to follow a curved flight path. The Magnus effect

essentially describes the action of a spinning ball through the air. As a ball spins, it

creates a boundary layer of air that adheres to the ball and rotates with it. As a

result, on the side of the ball that this boundary air collides with the air flowing past

the ball, it decelerates the ball producing a high pressure zone. While on the

opposite side, the spinning ball moves in the same direction as the air flowing past it,

which accelerates the ball and creates a low pressure area. As a result, the ball

curves in the direction of the low pressure. Applying the Magnus effect to the serve,

flexing the wrist over top of the ball produces a low pressure gradient below the ball

and therefore a ball hit at a tremendous velocity will still drop down and into the

service box. While the side spin will cause the ball to violently curve to the outside of

the service box, thus after it bounces it shoots outside of the court. Once the ball

leaves the racquet the force generation phase is complete.

Follow-through / recovery

This phase of the skill commences following contact with the ball. In order to

reduce the stress placed upon the muscles, joints and bones the server must

increase the amount of time that the force of body contacts the ground. Accomplish

this by landing first on the ball of the left foot, flexing at the ankle, lowering the heel

to the ground and flexing at the knees and hips. Converts the angular momentum

produced via the body and arm rotation into forward linear momentum. This is

accomplished by arresting the rotation of the hips and shoulders once they become

perpendicular to the court, forcefully pushing off the left leg and driving the right leg

into the court. Generate much more power via the hip and trunk rotation because his

right leg is forcefully whipped around and through. The motion depicted in pictures

indicate that hips do not rotate as forcefully and follow a much narrower pathway.

Finally, immediately crouched in a low and prepared stance upon the conclusion of

the follow through, while appear to stand up. In preparation for the opponents return,

need to immediately conduct the split step, in order to get into a proper ready

position. The knees should be bent, should be on the balls of the feet and the

racquet should be up and in front of the body so that can react quickly and anticipate

the oppositions attack.

2.0 CASE STUDY

SUBJECT

IMRAN DANIEL B. MOHD HAZLI

• Nationality - Malaysia

• 10 Jun 2005

• 9 years old

• Left handed

• Height – 1.28 cm

• Weight – 30 kg

• Sekolah Kebangsaan Seri Hartamas , Kuala Lumpur

• Club – Duta Academy

• State Team – Kuala Lumpur (2012-2014)

• Played since four year

• Sponsor : Dunlop

• 3rd place State MSSWPKL – U12

• 1st place MSSM 2012 u12-groups event

OUR GOAL

RAFAEL NADAL PARERA

Born in Spain on June 3, 1986, Rafael Nadal is a Spanish professional tennis

player who has been ranked among the world's Top 5 since 2003. Nadal is only the

second male player to achieve the Career Golden Slam and the first to win seven

French Open titles. He won the Roland Garros for four consecutive years, from 2005

to 2008, and went on to win Wimbledon 2008 against tennis star Roger Federer. In

2009, Nadal won the Australian Open, and came back to win his second Wimbledon

in 2010, as well as his first U.S. Open and fifth French Open title. The following year,

a No. 1-ranked Nadal lost his top ranking as well as Wimbledon 2011 to Serbian

tennis star Novak Djokovic. Also in 2011, he won his sixth French Open, followed by

a seventh French Open victory in 2012. In the 2012 Wimbledon semifinals, a No. 3-

ranked Nadal lost to Czech player Lukas Rosol—a match that some commentators

labelled one the biggest upsets in tennis history. In June 2013, Nadal won his eighth

French Open title against David Ferrer.

At the age of 8, Nadal won an under-12 regional tennis championship, giving Toni

Nadal the incentive to step up his training. Toni noticed at the time that Rafael played

his forehand shots with two hands, so he encouraged him to play left-handed,

thinking it could give Rafael an edge on the court. When Nadal was just 12 years old,

he won the Spanish and European tennis titles in his age group, and at age 15, he

turned pro and started playing on the junior circuit. At the age of 16, in his first ITF

junior event, Nadal made it to the semi-finals of the Boys' Singles tournament at

Wimbledon. By age 17, he became the youngest man to reach the third round at

Wimbledon since Boris Becker. At the age of 19, in 2005, Nadal won the French

Open the first time he played it, and his world ranking went to No. 3. Nadal won 11

singles titles that year, eight of which were on clay, and he was soon dubbed the

"King of Clay."

Nadal went on to win the next three French Opens. In 2006, after winning the

French Open— despite both shoulder and foot injuries—he won four other titles. The

following year, he won again at Roland Garros and took home five other titles. Nadal

poured it on in 2008, winning the French Open again, in addition to winning

Wimbledon—where he beat long-time rival Roger Federer in the longest final in

Wimbledon history—gold at the Beijing Olympics, and five other titles. After

Wimbledon, Nadal's winning streak stood at a career-best 32 matches. Since 2008,

despite being occasionally hampered by injuries, Nadal has been one of the

superstars of the tennis world, winning 15 titles and hitting No. 1 in the world-ranking

twice (in August 2008 and again in June 2010). He won the Australian Open in 2009

and came back to win his second Wimbledon in 2010, as well as his first U.S. Open

and fifth French Open title. The following year, a No. 1-ranked Nadal lost his top

ranking as well as Wimbledon 2011 to Serbian tennis player Novak Djokovic. In June

2012, however, Nadal defeated top-ranked Novak Djokovic to win his record seventh

French Open title—a feat never accomplished before in men's tennis. That same

month, a No. 3-ranked Nadal lost to Czech player Lukas Rosol in the Wimbledon

semi-finals—Rosol's fifth Grand Slam win, and a match that some commentators

labelled one the biggest upsets in tennis history.

In June 2013, Nadal won his eighth French Open title against fellow Spaniard

David Ferrer, 6-3, 6-2, 6-3 marking his eight French Open victory in nine attempts. "I

never like to compare years, but it's true that this year means something very special

for me," Nadal said after the match, in an interview with ESPN. "Five months ago

nobody of my team dreamed about one comeback like this because we thought that

[was] going to be impossible. But here we are today, and that's really fantastic and

incredible." Later that same month, Nadal lost in the first round at Wimbledon to

Belgian player Steve Darcis. A shock to tennis fans who expected a strong

performance from the Spanish player, Nadal lost the match in three sets, by 7-6(4),

7-6(8), 6-4.

Nadal is only the second male player in tennis history to complete the Career

Golden Slam—winning the French, Australian and U.S. Opens; Wimbledon; and the

Olympic Gold medal. Additionally, by 2011, he had taken the Spanish Davis Cup

team to victory four times (2004, 2008, 2009 and 2011).

In 2013, the future of Nadal's career became the subject of much speculation. He

won the French Open that year, but he made a poor showing at Wimbledon. At

Wimbledon, Nadal was eliminated in the first round of competition. He seemed to be

back on the upswing, however, at the U.S. Open. He defeated Novak Djokovic to win

the men's singles title.

3.0 ANALYSIS FRAMEWORK

There are several models of qualitative analysis of human movement.

Traditionally, kinesiology professionals have used a simple error detection and

correction approach to qualitative analysis. Here the analyst relies on a mental

image of the correct technique to identify errors in the performance and provide a

correction. This approach has several negative consequences and is too simplistic a

model for professional judgements (Knudson & Morrison, 2002). The application of

the principles of biomechanics is illustrated in the present book using a more

comprehensive vision of qualitative analysis than the simple error detection /

correction of the past. This text uses the Knudson & Morrison (2002) model of

qualitative analysis. This model provides a simple four task structure: preparation,

observation, evaluation / diagnosis and intervention. This model of qualitative

analysis is equally relevant to athletic or clinical application of biomechanics to

improving human movement.

In the preparation task of qualitative analysis the professional gathers relevant

kinesiology knowledge about the activity, the performer, and then selects an

observational strategy.

In the observation task the analyst executes the observational strategy to

gather all relevant sensory information about the performance of the movement.

The third task of qualitative analysis has two difficult components: evaluation

and then diagnosis of performance. In evaluation the analyst identifies strengths and

weakness of performance. Diagnosis involves the prioritizing of the potential

interventions to separate causes of poor performance from minor or symptomatic

weakness.

Intervention is the last task of qualitative analysis. In this task the professional

executes some action on behalf of the performer. Often in live qualitative analysis,

the analyst will return immediately to the observation task to monitor the intervention

and the mover‘s progress.

TOP SPIN SERVE

In tennis because of a net being in the middle of the court, using topspin will

increase the player's consistency. Topspin also allows a player a greater margin of

error. Because topspin brings the ball down toward the ground quicker, a player can

hit the ball higher over the net, thus increasing the margin of error. This may help in

lobbing an opponent who is waiting at the net, or playing directly to a player's feet.

Hitting low to high as the player approaches the contact point will impart lift. Keeping

the racquet face (the strings) slightly closed from perpendicular will impart the

topspin to the ball that the player wants. However, balls that bounce lower due to

greater force or backspin are much more difficult to return using a grip that confers

topspin such as the semi-western and western grips, as the racket is angled too far

downwards to 'lift' the ball back over the net. As such, topspin is more effectively

used on slower, higher bouncing surfaces such as clay. Topspin is also far more

difficult to impart on backhand strokes due to the physical limitations of an arm

stretched across the body.

Developing a consistent topspin serve is the key to becoming a competitive

tennis player. Unless you‘re comfortable with your second serve and believe that

your opponents won‘t ever be able to consistently attack with an aggressive return,

you need to learn how to serve with topspin.

Most professional players use topspin on their second serve, but topspin can

also be effective for first serves at the recreational level. With topspin, you can serve

over 100 miles per hour (161 km/hour), while clearing the net at a safe height and

consistently keeping the ball in play. Without topspin, however, the server has to

come dangerously close to the net in order to ensure that the ball stays in the service

box.

The topspin serve is difficult to learn. Compared to other basic tennis serves,

you toss the ball in a different location, strike the ball at an unusual angle, and use a

different grip. If you are new to the game, it might be beneficial to work on fine-tuning

your slice and flat serves before tackling topspin serves. However, your game will

have a major hole and your second serve will never be fully effective if you plan on

overlooking topspin serves altogether.

The Grip

The grip is extremely important when trying to execute a topspin serve as it

helps generate the needed spin for a successful serve. The Continental grip

maximizes the ―brushing‖ effect that you put on the ball when you strike the back of

it, which produces topspin.

The Ball Toss

The ball toss is perhaps the most important step for hitting a topspin serve,

and it will always be thrown with your non-dominant hand. An inaccurate toss

sacrifices both the control of your serve and the amount of topspin you generate. For

a flat serve, you generally try aiming your toss so the ball would land on the shoulder

of your dominant hand. On a topspin serve, however, you position the ball farther

back and slightly to the left (for righties) in a location directly above or slightly behind

your head. You don‘t want to toss the ball so high that it disrupts your rhythm, but

you need to toss the ball high enough that your arm is fully extended when you make

contact with the ball.

The Swing

Begin your swing at the same time as your toss. You should bring your

racquet back in unison with your non-dominant hand as it throws the ball in the air.

Your body should be turned sideways to the court, but not so extreme that your feet

are parallel to the baseline. As you toss the ball, transfer your weight from your front

foot to the back foot and arch your back.

Your swing should flow in a sideways direction, almost parallel to the

baseline, rather than forward towards the net. This step cannot be stressed enough:

Topspin serves veer away from the traditional serve where you swing in a straight

ahead, towards-the-net motion. Imagine that you are hammering a nail into the

ceiling, and your tennis racquet is the hammer. This exercise emphasizes the

upwards motion that your dominant hand and racquet need to be making — you

aren‘t swinging down on the ball, you‘re swinging up. You want to brush the back of

the ball while striking it in an upwards motion.

As you bring your racquet up to meet the ball, accelerate your racquet head up and

over the ball to generate the desired topspin. The motion should be fluid, so don‘t

tense up or shorten your stroke.

Hot Tip: Crank Up the Speed

Your racquet head needs to be moving faster for topspin serves as compared

to other serves because of the upward motion you take when you brush up on the

ball. The faster you swing, the more topspin you can generate, but this swing takes a

lot of practice to master. Start off slow, and gradually build up your racquet speed as

you grow more comfortable.

Tips

Before you start working on your swing technique, keep in mind the following

suggestions:

Line up at the baseline with your non-dominant shoulder pointing towards the

target. Turn your head sideways to face the net, and have your feet parallel to

your shoulders.

Don‘t drop your non-dominant arm. Many players drop their arm after they

toss the ball, but this is a critical mistake. Your shoulder and head will follow in

the direction of your arm, so keep that arm pointed up and your chest square

to the ball as you swing.

Bend your knees and load up on your back foot as you toss the ball. You

generate power from your legs, so bend your knees and explode up and at

the ball as you swing.

Don‘t worry about spraying balls all over the court. Most players really

struggle while learning topspin serves, and it‘s not uncommon for balls to soar

onto adjacent courts. You will become more comfortable with the stroke over

time, so keep practicing.

It‘s a good sign if you‘re consistently hitting the ball long. Serving the ball long

is an indication that you are learning how to control the ball, but you might

need to use more spin in order to make the ball dive downward and into the

service box.

Practice with Persistence

There is nothing more frustrating than missing serve after serve, especially

when the balls are landing in the service box on the court next to you. Try not

to worry yourself with where the ball initially ends up. It‘s more important that

you focus on proper mechanics and to familiarize yourself with the stroke.

Over time, you will see the benefits of your hard work — just know that you‘ll

have to go through hundreds, possibly thousands, of balls before you can

consistently keep your serve in play.

4.0 FACTOR ANALYSIS

CRITICAL VARIABLES

5.0 INTERVENTION

PREPARATION PHASE

• Stand with the appropriate distance behind the baseline.

• Holds the ball and racquet out in front of his body, and his weight resting

primarily on his right leg.

• Toss the ball curve and high to the back body. Bent knee 45º and swing

racquet handed from the back.

• Contact the ball at your highest point. Make follow through with front leg.

OBSERVATION PHASE

In games

EVALUATION PHASE

• Prioritize weaknesses:

1. Height of the ball when toss curve to back body

2. Knee flexion over 45º

3. Body angle not straight

4. Contact end point before the ball goes down

INTERVENTION PHASE

• Priorities turned into verbal cues

• Visual feedback to explain the verbal cues

• “Toss”(ball toss curve high to the back body)

• ―Bent” (knee flexion 45º)

• “Hit” (before ball going down)

• Live video streaming using Kinovea software to provide visual feedback

2 WEEKS TRAINING PROGRAM

TRAINING 1 - CUE

• Curve to back body

• High-higher more better.

• Knee bent 45º

• Swing racquet at back

• maximizing the swing racquet for more power

• Racquet at highest point

• Hit ball – point of contact before ball going down

• Follow through

• 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).

• Subject take training by ―toss and catch‖ the ball 30 times per set. 6 set toss

training to provide the ball goes curves at the back and high.

TRAINING 2 – VIDEO ANALYSIS (FEEDBACK)

• Based on slow motion video from Rafael Nadal topspin serve found that he

created a body gesture while toss the ball curve at the back highest point

direct to right hand.

• After toss it, Nadal bent his knee at 45º to give more power of speed and the

racquet reach at the highest point to make more impact of acceleration.

• Meanwhile the subject didn‘t take serious of body gesture before proceed with

topspin serve. After instruction and guidance provided to subject, he still not

apply the body gesture at the earliest stage of serve.

• His body also not straight enough when hit ball and this may cause him not to

achieve the maximum performance of serve.

• Subject ―toss and knee bent training with and without ball‖. 10 repetition per

set without ball and 10 with ball. After toss the knee must bent at 45º to make

power of serving.

• Instruct student to do serve training for 2 weeks to improve his serve level.

• After instruction and training for 2 weeks subject achieve the main target.

Student toss the ball curve high to back body and bent his knee at 45º which

same with his model, Rafael Nadal.

6.0 RESULT

BEFORE AFTER

• After toss it, he did follow the contact end point before the ball goes down to

serve the ball with speed and inside the serving box with follow through.

• The higher the contact point can make the ball to be hit with more power and

speed.

• Top spin is produced by brushing the racket up the back and over the top of

the ball as it is leaving the racket. "This leads to a negative lift force (or larger

pull downwards) which makes the ball loop down towards the ground at a

steeper angle. The steeper angle makes the bounce higher and wilder (kick)

making it difficult to return"(Thomas, 2012).

7.0 CONCLUSION

• We can see improvement of overhead topspin serve steps for subject after

training and instruction given.

• In training, subject more focus on instruction cues given by coach that make

increase his performance.

• Subject easy to adapt the topspin serve steps due to have tennis experience

since four year.

• He also able to hit the ball accurately and most of the serve attempts went in

easily.

• The power and speed of topspin serve improve after training and instruction

cues provided.

• ―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.

8.0 SUGGESTION

• For further research need to allocated more timeframe to monitor student

improvement. Such as 4 to 8 weeks to get better result and progress.

• Next researchers also can focus on other factor such as preparation, wind-up

or follow through.

• This studies also can use for secondary school athletes for better

performance in overhead topspin serves.

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