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  » Rakesh Patel
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Rakesh Patel

An 8-Stage Model for Evaluating the Tennis Serve

Implications for Performance Enhancement and Injury Prevention
Background:

A series of segmental rotations involving the entire kinetic chain. Many overhead athletes use a basic 6-stage throwing model; however, the tennis serve does provide some differences.

Results:

An 8-stage model of analysis for the tennis serve that includes 3 distinct phases (A) Preparation (B) Acceleration, and (C) Follow-through

Synchronised movement results from the combination of limb and joint movements required to summate and transfer forces from the ground up through the kinetic chain and out into the ball. Best servers use selective muscle groups, segmental rotations, and coordinated lower extremity muscle activation (quadriceps, hamstrings, and hip rotators, internal and external). 

If any of the links in the chain are not synchronized effectively, the outcome of the serve will not be optimal.


The Kinetic Chain And The Tennis Service Motion

Players increase the maximum linear velocity from the knee to the racquet.

The preparation phase (stages 1-4) results in the storing of potential energy that can be utilized as kinetic energy during the acceleration phase. 

In an efficiently functioning kinetic chain, the legs and trunk segments are the engine for the development of force and the stable proximal base for distal mobility. This link develops 51% to 55% of the kinetic energy and force delivered to the hand. This link also creates the back-leg-to-front-leg angular momentum to drive the arm up and forward.

The 3 Major Types Of Serves In Tennis

3 major types of serves:

(1) Flat (limited spin)

(2) Slice (sidespin), and 

(3) Topspin (kick)

It is important to understand the differences in these serves and how they may affect the kinetic chain muscle activation patterns and summation of forces. There is an inverse relationship between speed of serves and spin rate 

The lower body does not show major differences in the 3 serves. 

Figure 2.

The major differences seen in serves occur higher in the kinetic chain—namely, at the racket face angle, as determined by forearm pronation and internal shoulder rotation.

The 8-Stage Model

3 distinct phases: 

(1) Preparation - store energy 

(2) Acceleration - release energy

(3) Follow-through - deceleration

Preparation 

Phase 1: Start 


-The start of a player’s serve reflects style and individual tendency rather than substance. 

- Muscular demand is very low.

- The goal of the start is to align the body to utilize the ground for force/power generation throughout the service motion.

Figure 4.

 

Phase 2: Release 


- This stage occurs in an instant when the ball is released from the nondominant hand (left) (Figure 5). 

- Muscle activation is very limited in the left erector spinae during the start and release stages.

- The activity of the right erector spinae increases steadily from the beginning of the serve through the end. 

- The location of the toss relative to the player affects arm abduction and subacromial humeral position. The toss should be out slightly lateral to the overhead position of the server, facilitating ball contact at approximately 100° of arm abduction. 

- Improper toss location too close to the head (12 o’clock position) can increase arm abduction and cause subacromial impingement. 

- Trunk position and toss location are factors in shoulder pain during the acceleration and contact phases of the tennis serve.

Figure 5.

 

Phase 3: Loading 


Loading positions the body segments to generate potential energy (Figure 6). There are 2 broad types of lower body loading (foot position) options: the foot-up (Figure 7) or the foot-back (Figure 8) technique.

Figure 6.
 Figure 6
Figure 7.
Pinpoint Stance - Foot-up serving technique.
 
- Develop vertical forces, which allow them to reach a greater height than that of the foot-back

-The foot-up serving technique requires eccentric training of the lower body for landing.

Figure 8.
Platform Stance - Foot-back serving technique.

- The back leg provides most of the upward and forward push, whereas the front leg provides a stable post to allow rotational momentum. 

Service velocity correlates with greater muscle force during the loading stage (stage 3), while service efficiency is related to internal rotation of the arm.,, Optimal leg drive mechanics and internal rotation arm flexibility are critical for efficiency and velocity. Maximizing leg motion can produce a consistent leg drive that may enhance shoulder rotation and more efficient serves. Compared with beginner servers, elite servers have greater vertical and horizontal force production and earlier activation of the major lower body muscle.

Shoulder and pelvis lateral rear tilt before the cocking phase (ie, during the loading phase) is a feature of powerful servers (Figures 8 and 9). This tilted alignment facilitates the development of angular momentum through lateral trunk flexion during the forward swing: a critical factor in a high-velocity serve.

Figure 9.
Shoulder and pelvis lateral rear tilt during the loading stage.

The ground reaction forces created in stage 3 (loading) result in an off-center angular impulse, which elevates the racquet side (dominant arm side) of the body and lowers the opposite side (nondominant arm). This produces a shoulder-over-shoulder rotation as the server explosively moves the arm toward the position of ball contact (stage 6) and allows for greater racket height. These movements transfer angular momentum from the lower limbs to the upper limb. To achieve this optimum position, lateral trunk flexion (right to left) requires good flexibility and optimal core stability throughout the range of motion.

A front knee flexion angle greater than 15° during the loading stage is recommended for effective front “leg drive.” Elite servers with optimal front “leg drive” have lower anterior shoulder and medial elbow loads. The benefits of effective kinetic chain involvement include reducing injury potential in the high-performance tennis serve. The activation patterns of the lower trunk muscles clearly demonstrate a high degree of co-contraction during a tennis serve, especially during stages 3 to 7.

During right trunk rotation in a right-handed server (Figure 10), the ipsilateral erector spinae is more active than the contralateral. The ipsilateral erector spinae increase activity from stage 3 through the end of the deceleration phase of the serve. The lateral left erector spinae assist lateral flexion after stage 3 (loading).

Figure 10.
Trunk and torso rotation during the loading stage of the serve.

During the loading and cocking phases, the spine moves into hyperextension, ipsilateral lateral flexion, and ipsilateral rotation. This loads the spinal facets and is a potential factor in the development of spondylolysis in elite developing players. Electromyogram (EMG) studies demonstrate high trunk muscle activation in this stage. The plyometric stretch-shortening pattern in the tennis serve leads to selective development of the trunk flexors (abdominals). Isokinetic testing shows flexion:extension ratio imbalance in elite tennis players., Symmetric trunk rotation dictates the need for bilateral trunk rotation strength and conditioning exercise (core stabilization) as well as extensor targeting.,

Phase 4: Cocking 

The cocking position (Figure 11) depends on an efficient loading stage (stage 3). Increasing the efficiency of the dominant arm in driving the racket down and behind the torso lengthens the trajectory of the racket to the ball. 

Figure 9.
Shoulder and pelvis lateral rear tilt during the loading stage.

The ground reaction forces created in stage 3 (loading) result in an off-center angular impulse, which elevates the racquet side (dominant arm side) of the body and lowers the opposite side (nondominant arm). This produces a shoulder-over-shoulder rotation as the server explosively moves the arm toward the position of ball contact (stage 6) and allows for greater racket height. These movements transfer angular momentum from the lower limbs to the upper limb. To achieve this optimum position, lateral trunk flexion (right to left) requires good flexibility and optimal core stability throughout the range of motion.

A front knee flexion angle greater than 15° during the loading stage is recommended for effective front “leg drive.” Elite servers with optimal front “leg drive” have lower anterior shoulder and medial elbow loads. The benefits of effective kinetic chain involvement include reducing injury potential in the high-performance tennis serve. The activation patterns of the lower trunk muscles clearly demonstrate a high degree of co-contraction during a tennis serve, especially during stages 3 to 7.

During right trunk rotation in a right-handed server (Figure 10), the ipsilateral erector spinae is more active than the contralateral. The ipsilateral erector spinae increase activity from stage 3 through the end of the deceleration phase of the serve. The lateral left erector spinae assist lateral flexion after stage 3 (loading).

Figure 10.
Trunk and torso rotation during the loading stage of the serve.

During the loading and cocking phases, the spine moves into hyperextension, ipsilateral lateral flexion, and ipsilateral rotation. This loads the spinal facets and is a potential factor in the development of spondylolysis in elite developing players. Electromyogram (EMG) studies demonstrate high trunk muscle activation in this stage. The plyometric stretch-shortening pattern in the tennis serve leads to selective development of the trunk flexors (abdominals). Isokinetic testing shows flexion:extension ratio imbalance in elite tennis players., Symmetric trunk rotation dictates the need for bilateral trunk rotation strength and conditioning exercise (core stabilization) as well as extensor targeting.,

 

Phase 4: Cocking 

The cocking position (Figure 11) depends on an efficient loading stage (stage 3). Increasing the efficiency of the dominant arm in driving the racket down and behind the torso lengthens the trajectory of the racket to the ball. This position allows for greater potential energy but does require optimal range of motion, positioning, and stabilization throughout the shoulder region.

Figure 11.
Preparation phase. Stage 4: Cocking.

- High internal rotator eccentric loads are applied during the late preparation phase (backswing) (Figure 12), later transitioning into the acceleration phase (stage 5) before impact. 

- Effective leg drive forces the racket in a downward motion away from the back. 

Figure 12.
Shoulder and serving arm position during the cocking stage of the serve.

Between the loading stage (position 3) and the beginning of the acceleration stage (position 5), there is an increase in vertical ground reaction forces, while increased muscle activation occurs in the vastus medialis, vastus lateralis, and gastrocnemius. Maximal shoulder external rotation is achieved 0.090 ± 0.014 seconds before contact in professional tennis players. Leg drive is near completion at this stage. At the instant of maximum external rotation, the shoulder is abducted 101° ± 13°, horizontally adducted 7° ± 13°, and externally rotated 172° ± 12°; the elbow is flexed 104° ± 12°; and the wrist is extended 66° ± 19°. This resulted in a near parallel position between the racket and the trunk. The magnitude of external rotation is similar to that for elite baseball pitchers, 175° to 185°., This degree of external rotation is a combination of glenohumeral and scapulothoracic motion, as well as trunk extension motion.

Repeated external rotation in the tennis serve can lead to increased shoulder external rotation on the dominant arm at the expense of internal rotation., These increases in external rotation do not match the magnitude of the increases reported in the dominant arm of professional baseball pitchers., Loss of both internal rotation and total rotation up to 10° to 15° in elite level tennis players occurs at 90° in the abducted shoulder.,, Stretches of the posterior shoulder (sleeper and cross arm Pupils Linked In:0
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