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Tóm tắt nội dung (trích từ tài liệu gốc): See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/274370956 Biomechanics of Advanced Tennis Book � January 2003 CITATIONS READS 10 1,369 3 authors: Machar Reid Tennis Australia Bruce C Elliott 154 PUBLICATIONS 890 CITATIONS University of Western Australia 308 PUBLICATIONS 5,389 CITATIONS SEE PROFILE SEE PROFILE Miguel Crespo International Tennis Federation 212 PUBLICATIONS 419 CITATIONS SEE PROFILE All content following this page was uploaded by Bruce C Elliott on 23 April 2015. The user has requested enhancement of the downloaded fil
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Biomechanics of Advanced Tennis
Book � January 2003
CITATIONS READS
10 1,369
3 authors: Machar Reid
Tennis Australia
Bruce C Elliott 154 PUBLICATIONS 890 CITATIONS
University of Western Australia
308 PUBLICATIONS 5,389 CITATIONS SEE PROFILE
SEE PROFILE
Miguel Crespo
International Tennis Federation
212 PUBLICATIONS 419 CITATIONS
SEE PROFILE
All content following this page was uploaded by Bruce C Elliott on 23 April 2015.
The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document
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Biomechanics and tennis
B Elliott
Br. J. Sports Med. 2006;40;392-396
doi:10.1136/bjsm.2005.023150
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392
REVIEW
Biomechanics and tennis
B Elliott
...............................................................................................................................
Br J Sports Med 2006;40:392�396. doi: 10.1136/bjsm.2005.023150
Success in tennis requires a mix of player talent, good concentric phase (shorten) is enhanced. This is
coaching, appropriate equipment, and an understanding also supported by the fact that the concentric
of those aspects of sport science pertinent to the game. This action begins with the appropriate muscles
paper outlines the role that biomechanics plays in player under higher tension than would be created if
development from sport science and sport medicine they were to contract purely concentrically from
perspectives. Biomechanics is a key area in player a resting state. Research has shown that the
development because all strokes have a fundamental benefit to performance from these two factors,
mechanical structure and sports injuries primarily have a particularly the muscle pre-tension, is critical to
mechanical cause. success in sports such as tennis.6 Examples from
selected strokes are:
...........................................................................
N Service: A subtle coaching point in maximis-
S uccess in tennis is greatly affected by the
technique a player uses and biomechanics ing power in the serve is the timing of the ``leg
plays an integral role in stroke production. drive'' with the racquet preparation for the
All strokes have a fundamental mechanical drive to the ball. The eccentric stretch and pre-
structure, and sports injuries primarily have a tensing of the anterior shoulder muscles
mechanical cause.1 Player development based on (particularly the internal rotators) is max-
scientific evidence allows an individualised imised by a vigorous leg drive which positions
approach to be structured, with due considera- the racquet ``down behind and away from the
tion to the key mechanical features of each skill, lower back'' in preparation for the drive to the
while also fostering flair and permitting the ball.
physical characteristics of a player to be con-
sidered. An understanding of biomechanics from N Groundstrokes: Rotation of the shoulders
a sports medicine perspective is also important if
player development is to occur with minimal risk greater than the hips (creating a separation
of injury. angle) and the positioning of the upper limb
relative to the trunk during the backswing
The examples given in the following sections phase of these strokes, place appropriate
are intended to reflect general directions rather muscles on stretch. This is why in the back-
than provide a comprehensive review of the
literature. More detailed reviews can be found in hand a separation angle (one handed ,30�;
the ITF publication Biomechanics of advanced two handed ,20�) is created in the backswing
tennis,2 and the books From breakpoint to advan-
tage,3 The physics and technology of tennis4 and in preparation for the swing to the ball.7
Biomechanical principles of tennis technique: using
science to improve your strokes.5 N Volley/service return: The split step, an inte-
The review will be presented under a number gral part of preparation for a volley, service
of headings that reflect the different areas in return, or groundstroke, places the quadriceps
which biomechanics is important to player muscle (extensor at the knee joint) on stretch,
development. Firstly, biomechanics from a gen- permitting storage and subsequent release of
eral perspective will be followed by the role it energy to enhance quick movement in pre-
plays in stroke production. Sports medicine, as it paration for the subsequent stroke.
plays a role in the development of stroke
production, is then discussed from a biomecha- The key to the recovery of the elastic energy is
nical perspective. the timing between the stretch and shorten
phases of the motion. The benefit of this stored
....................... GENERAL THEORY OF BIOMECHANICS energy is reduced if a delay occurs between these
Biomechanics theory provides coaches, players, phases of the movement. In the bench press,
Correspondence to: and sport science support staff with a general after a period of about one second, 55% of the
Professor Elliott, University framework for the development of stroke pro- stored energy was lost.8 Elliott et al9 showed that
of Western Australia, duction. I will discuss a number of the general speed of internal rotation of the upper arm was
Perth, WA, Australia; principles that guide this development. increased by about 20% for a no-pause compared
bruce.elliott@uwa.edu.au with a 1.5 second pause condition. In tennis it is
Muscle pre-tension (elastic energy) therefore essential that only a short pause occurs
Accepted In a stretch-shorten cycle, elastic energy stored between the backswing and forwardswing
10 December 2005 during the eccentric phase of the action (the phases of stroke production or at maximum
....................... stretch) is partially recovered, such that the knee flexion during the serve.
Kinetic chain
There are generally two segment coordination
strategies used in tennis (table 1). In strokes
where power is required (such as the service and
groundstrokes), a number of body segments
must be coordinated in such a way that a high
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Biomechanics and tennis 393
Table 1 Coordination strategies in tennis
Power stroke (the service)10 Precision stroke (the volley at net)11
Leg drive and trunk rotations) shoulder speed Shoulder rotation, forward step of ) racquet speed
(forward/shoulder-over- the front leg, and forward
shoulder/twist) movement of the racquet arm all
work together as a unit
+ ) elbow speed
Upper arm elevation and
flexion ) wrist speed and
+ racquet orientation
Forearm extension and
pronation and upper arm ) racquet speed
internal rotation
+
Hand flexion
racquet speed is generated at impact. Where precision is The complexity of fig 1 is one reason why coaches often
needed, the number of segments is reduced and segments prefer to use the ``critical points'' approach as the basis for
operate more as a unit (such as the volley at the net), although their analyses.
the drive volley now challenges this general principle.
Irrespective of what procedure is used, the four stage
Efficient function, with maximal performance and mini- approach to technique development (preparation, observa-
mal risk of injury, requires optimum activation of all the links tion, intervention, and reassessment) developed by bio-
in the kinetic chain designed for power.12 Injury is often mechanists in combination with pedagogists has had a major
associated with alterations in the flow of energy across influence on the way tennis stroke production is analysed,
segments, such that if one segment is removed from the interventions developed, and performance reassessed.
chain, then there is an increased reliance on the others to
accommodate this loss, which may lead to tissue overload. Equipment design
A discussion of this topic is beyond the scope of this paper,
Variability in stroke production and the reader is directed to the book by Brody et al4 for a
Work by Knudson13 has shown that selected aspects of the complete review of this broad topic. However, there is no
stroke production of high performance players are variable, doubt that modern racquets have enabled the ball to be hit
whereas other aspects are repeatable. For instance, in the with a higher speed than was possible with previous designs.
forehand drive, wrist and elbow angular positions are Lighter racquets with larger ``areas of percussion'' and new
generally consistent at impact. However, this repeatable string designs have all affected modern technique and are the
angular position was not the result of highly consistent primary reason for a number of changes to stroke production
patterns of angular velocity and acceleration of the same discussed below.
joints. That is, a given end result is achieved through a variety
of movement strategies. Coaches in developing stroke BIOMECHANICS OF STROKE PRODUCTION
production must then vary drills--for example, pace, spin, Serve/groundstrokes
direction, and height of ball feed or drill structure--to Internal rotation of the upper arm at the shoulder
develop a variety of neuromotor timings associated with a Work by my team has primarily been responsible for
given stroke, to achieve the almost infinite combinations of identifying the important role that internal rotation of the
racquet speed, trajectory, and impact characteristics asso- upper arm at the shoulder joint plays in the service (fig 2)
ciated with a successful return. and the forehand strokes (table 2).10 14 This factor has in
many ways modified the way that these strokes are
Analysis protocols developed at beginner and advanced levels of play. The
Technique analysis falls on a continuum between subjective images in fig 2 show how internal rotation at the shoulder,
(qualitative) and more objective (quantitative) analyses. which begins before impact, continues into the early follow
Research shows that an expansive view of subjective through phase of the service action. Functionally, the internal
technique analysis, the procedure generally used by coaches, rotator musculature must accelerate the upper arm in the
is required if performance is to be optimised. Any effective swing to impact, before the external rotators eccentrically
process must evaluate movement to identify both strengths contract to decelerate this rotation during the follow through
and weaknesses in performance and then diagnose the phase of the action. As the external rotators are much smaller
movement to prescribe an appropriate intervention.15 than their internal rotator counterparts, it is essential that
specific training is structured to protect the shoulder from
A variety of models of technique analysis have been injury, as discussed in the sports medicine section below.
proposed. However, they may generally be divided into
approaches that focus on: Remember, these figures relate to the approximate
contributions at impact and take no consideration of such
N analysing general biomechanical principles--for example, movements as leg drive in the service action. They are
indicators of the movements responsible for the generation of
assessment of balance during stroke production, followed racquet speed and do not indicate the importance of a
by the application of force and inertia in the development particular movement in a stroke. For instance, in the power
of racquet speed and so on serve, pronation is primarily responsible for racquet orientation,
and elbow extension assists in the generation of impact height.
N identifying variables that are structured in a deterministic
Trunk rotations in the serve
model--the mechanical method (see fig 1 for a model of The view most commonly held by coaches was that a player
the serve). The advantage of this approach is that the rotated the trunk horizontally about a near vertical axis
relations between variables is highlighted
N key technique points (position of the racquet at the
completion of the backswing or impact) being identified
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394 Elliott
POWER SERVE
BALL SPEED BALL TRAJECTORY
Ball speed at impact (horizontal ~ 0) Air resistance/gravity
PREPARATION/BACKSWING Ball spin Vertical Racquet trajectory and
� Grip movement of alignment
� Foot positions
� Trunk rotation ball Vertical and horizontal
racquet speed
� hips Off-centre
� shoulders impact
� Racquet rotation
Racquet speed (horizontal) � displacement Angle of racquet face Grip
� Type of swing
� full Upper limb
� abbreviated angles
� Body orientation
� Ball toss Trunk alignment
� relationship of arms (off the ground)
� position of non-racquet arm
Pre-impact ball path and height
FORWARDSWING
� Leg drive IMPACT POSITION
� Position at maximum external rotation
� Shoulder and arm alignment � Off ground and in court
� Trunk rotations � Shoulder abduction angle
� Body extended
� twist � Racquet not aligned with forearm
� forward
� shoulder-over-shoulder
� Weight transfer
� Non-racquet arm tuck for trunk rotation
� Shoulder flexion
� Elbow extension
� Shoulder internal rotation
� Wrist flexion
FOLLOW THROUGH
� Internal rotation
� Landing
� foot
� position on court
� Racquet path
Racquet (strings, impact position)
Figure 1 Model of the power serve in tennis. Published with permission of the International Tennis Federation.
during the forward swing in the service action. Players knew Lower limb and pelvic drive in groundstrokes
better and have tilted the trunk to rotate more in a shoulder- Research at the University of Tokyo has provided insight into
over-shoulder orientation, rather than a simple horizontal the role of lower limb drive and pelvic rotation in the
rotation of the shoulders. They obviously positioned them- forehand17 and backhand18 strokes. The importance of
selves in this manner to enable internal rotation of the upper internal extensor moments at the back hip was identified
arm at the shoulder to play the important role in the service in both the above studies. Again the importance of hip
action that we now know it does (fig 2). Research by (pelvic) rotation has been highlighted in both forehand and
Bahamonde16 on angular momentum in the trunk during the backhand strokes.
serve clearly showed the importance of shoulder-over-
shoulder and forward rotation movements during the service SPORTS MEDICINE
action. Although science again cannot claim that it was the Loading
reason for these movements, it certainly played an integral Epidemiological data have shown that tennis injuries are
role in their integration into player development. Current primarily caused by overuse.3 Loading (the rate of force
research by Elliott, Sweeney, Alderson, and Reid is aimed at development, peak force, and torque are mechanical factors
quantifying the role of the ``back leg drive'' in the generation of that collectively are often referred to as ``load'') may be
shoulder-over-shoulder trunk rotation in the service action. applied to the body externally (ground reaction force,
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Biomechanics and tennis 395
Figure 2 Pictures of service action showing shoulder-over-shoulder trunk rotation and internal rotation of upper arm at the shoulder joint. Published
with permission of the International Tennis Federation. The player has given permission for publication of this figure.
vibration) or internally (muscle forces and torques). Research Tennis elbow
on elite players at the Sydney Olympics provided an insight The prevalence of lateral humeral epicondylitis is acknowl-
into the load placed on the shoulder and the elbow joint of edged as a condition that primarily occurs in the recreational
these players.19 These data provided information on leg drive, athlete. Research on the one handed backhand stroke shows
the abbreviated backswing, and service speed as they affected that this condition may be related to the use of faulty stroke
shoulder and elbow loading. In very general terms, this paper mechanics by novice players.21 Skilled players impact the ball
showed the following. with a hyper-extended wrist and extend the hand through
impact. That is the extensor muscles about the wrist joint act
N Loading increased with an increase in service speed. That concentrically to develop racquet speed through impact.
However, novice players often strike the ball with the wrist
is, irrespective of sex, if a player wishes to develop a more
powerful serve they need to modify technique (rotate flexed (,13�), while moving the hand at the wrist joint into
selected segments more quickly) and prepare the body
physically to perform the higher speed movement(s). further flexion. That is the extensor muscles about the wrist
joint contract eccentrically, before the contraction concen-
N Those players with more effective knee flexion-extension trically following impact. Wrist extensor electromyography
for both groups showed similar levels of activity in the period
during the service action were associated with lower before ball impact, whereas the skilled players showed
loading at the shoulder and elbow. This finding needs to greater electromyographic levels after contact.
be further clarified such that the effect of leg drive on
loading is assessed; this is currently taking place at the The above study was followed by another with a similar
University of Western Australia. design but with professionals and intermediate level players
N There was a trend for players with very abbreviated Table 2 Approximate contributions to impact racquet
velocity (%)
backswings to record higher force levels at the shoulder.
This finding is also currently being tested in a more Topspin forehand
controlled design. Power serve (forward direction)
Staying on the topic of loading and the tennis serve, Chow Shoulder 10 15
et al20 investigated activation on the lower trunk muscles Upper arm
during various types of service actions. They showed that co- 15 25
activation of lower trunk muscles assists in the stabilisation Horizontal flexion
of the lumbar spine during extension/flexion and rotation of Internal rotation 40 40
this region during the service action. The abdominal muscles Forearm
were more active in the topspin serve than the flat and slice Extension Negligible Negligible
serves during the upward swing of the racquet to impact. Pronation 5 Negligible
These results reinforced the importance of abdominal and Hand
low back exercises (core stability) together with the muscles Flexion (palm/ulnar) 30 �
about the shoulder and lower limbs in strength and Flexion (palmar/radial)
rehabilitation programmes in tennis. � 20
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396 Elliott
with and without a history of tennis elbow.22 Hand angular What is already known on this topic
velocity at the wrist, measured by an electrogoniometer, was
significantly different in the professionals (4 rad/s, exten- N The biomechanics of tennis has been well researched, but
sion) and intermediate group who had a history of tennis
elbow (0.4 rad/s, flexion). As with the study by Blackwell and publications are spread over a wide range of journals
Cole,21 lateral epicondylitis has been associated with an
eccentric contraction of the wrist extensors at impact. No N Furthermore, interpretations of findings are in various
significant differences were found in impact acceleration or
elbow kinematics between the three groups. formats, thus limiting their application
Muscle balance What this study adds
One of the possible causes of shoulder injury may be peak
strength/torque imbalances in those muscles responsible for N This review succinctly integrates biomechanical research
acceleration and then deceleration of the upper arm at the
shoulder joint. Certainly work by Tod Ellenbecker and Paul from performance and sports medicine perspectives
Roetert has provided players, coaches, and sports medicine
personnel with isokinetic profiles of highly skilled and junior has certainly assisted tennis development, it is also important
tennis players.23 The comparison of the concentric strength of to realise that much is still to be accomplished.
one muscle group compared with the eccentric strength of
the antagonist group in throwers was explored by Noffal.24 He Competing interests: none declared
concluded that rehabilitation and injury prevention regimens
that include exercises for eccentric external rotation strength The player in figure 2 has given permission for its publication.
may bring more balance to the dominant shoulder of
throwing athletes. Such information is critical to the REFERENCES
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CONCLUSIONS
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