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Old 12-26-2010, 01:36 PM   #62
toly
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Default Seriously About Flat and Kick Serve

2.2.2 The Flat Serve with Intensive Arm Pronation, Wrist Flexion, and Restrained Wrist Ulnar Deviation
Figures below give us an idea about arm actions during typical flat serve.

Figure 2.15. The arm’s actions during Marat Safin's flat serve

Figure 2.16. The arm’s actions during Kevin Anderson’s flat serve

In case of the typical flat serve the main components of the racquet speed are: the fast arm pronation, the fast wrist flexion and slow vertical arm rotation. If players are employing Continental grip, all these motions mostly create the flat component of the racquet speed and practically no spin. The most important would be the arm pronation.
It follows from these photos, during the pronation phase of the flat serves both players keep their right elbows in bend position. In all previous analyzed spin serves, most pros maintain their arms during pronation phase practically straight.
Question: Why during the pronation phase, these players keep elbows in bend position?
Answer: When we swing the racquet upward our shoulder joint brings the upper arm in vertical and the forearm in horizontal position. After that, by using fast elbow extension, the forearm moves upward and the pronation angle β equal 90 degrees (Fig. 2.15.1). If the elbow unbends completely, it brakes and inevitably the racquet starts moving upward by using inertia and very fast wrist ulnar deviation. This motion reduces the pronation angle beta (Fig. 2.15.4 β=45) and can kill pronation component of the racquet speed. To prevent it from occurrence, even during the impact, the elbow joint should be bent. Next pictures (Figure 2.17) illustrate Andy Roddick’s arm action during flat serve and confirm last statement.


Figure 2.17. Andy Roddick's arm actions during flat serve
Pay attention on the angle between axis of the upper arm and the forearm. This angle is never less than 30 degrees. Andy constructs the motion which often called as elbow snap. Maybe this is the main secret of his so successful flat serve. For instance, Marat Safin during impact keeps his elbow straight (Fig. 2.15.4). That’s why, perhaps, his serve is slower than Roddick’s. But, Marat straightens his arm at the very last moment before impact by using the elbow extension. This motion doesn’t have enough time to decrease significantly pronation angle beta, and produces just spin (not flat component). Hence, it enhances the serve’s reliability.
In everyday life, when we “pronate/supinate” a screwdriver, for example, we always unconsciously keep elbow in bend position to increase a force applied to the screwdriver’s handle. The same natural motion Andy applies to the racquet’s handle. He uses bend elbow as some kind of “force multiplier”. I think, it doesn’t make any harm if this force would be very active during impact. This screwdriver approach could be very handy to overcome the inertia’s resistance of the tennis ball and hence, increase its speed. Bent elbow also increases radius of internal shoulder rotation and thus boll’s translational speed. To increase the flat component of the racquet speed all the best servers also apply the wrist flexion.
I believe, we can keep the bend elbow before and during impact even in case of the kick serve, but with deliberately active the wrist ulnar deviation. It could help to curb excessive activity of the wrist ulnar deviation and hence keep the appropriate amount of the pronation angle beta (not less than 30 degrees).
To be continued, see please post #63.
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Anatoly Antipin - one of the most delicate tennis players in the world.

Last edited by toly : 03-01-2013 at 10:48 PM.
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