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21 sep 2006

Tennis play symulator ii speed of sequential ball-hitting movements under practice and competitive conditions

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The single ball-hitting movement in tennis has character of sequential movement and consists of four separate, sequentially performed segments (movements): preparatory movement (split step), displacement (locomotion) to hit the ball, ball-hitting proper, displacement after ball-hitting.
Autor(es): Janusz Lapso
Entidades(es): University of Poznan, Poland
Congreso: IV Congreso Mundial de Ciencia y Deportes de Raqueta
Madrid-21-23 de Septiembre de 2006
ISBN: 84-611-2727-7
Palabras claves: tennis play symulator, movements, competitive conditions.

Abstract tennis play symulator ii speed of sequential ball-hitting movements

The single ball-hitting movement in tennis has character of sequential movement and consists of four separate, sequentially performed segments (movements): preparatory movement (split step), displacement (locomotion) to hit the ball, ball-hitting proper, displacement after ball-hitting. The task of the preparatory movements (split step) is to prepare the muscles to move the body towards the ball as quickly as possible.

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1. Introduction

The single ball-hitting movement in tennis has character of sequential movement and consists of four separate, sequentially performed segments (movements): preparatory movement (split step), displacement (locomotion) to hit the ball, ball-hitting proper, displacement after ball-hitting. The task of the preparatory movements (split step) is to prepare the muscles to move the body towards the ball as quickly as possible. The “split step” often takes the form of a single jump on both feet. This movement induces the initial tension in the leg muscles so that the start of the run is faster. The displacement to hit the ball is directed towards moving the body as fast as possible to the place where the ball is flying. Except for the service, the ball-hitting proper is performed with respect to the place, speed, spin and trajectory of the flight of the ball and the opponent’s position. The final purpose of the ball-hitting proper is to score a point or cause the opponent to mishit the return. The purpose of displacement after the ball has been hit is to reach as quickly as possible the best position at the playing court to cover the possible lines (directions) of flight of the returning ball. Contemporary tennis requires the ball-hitting movements to be performed in an economical way (good space form and internal timing), at the right spot (good ball and racket movement coincidence), very fast and with very high precision. The space form (technique of performance) decides how the movement will run in the space. The form is determined by the muscles chosen to execute the movement. The internal timing (Lapszo, 1999a, 2000) reflects the time coordination of movement of particular body parts in a definite stroke. The trajectory and the speed of the ball and racket movement decide in what spot in the space the ball will be struck by the racket. The spot is related to the anticipation of coincidence (Belisle, 1963), which consists of predicting the time or place (or both) where the ball will arrive and performing a movement coincident with the time and the place. This anticipation can be divided into place and movement coincidence anticipation (?apszo, 1999a). In the first case, the anticipation consists in predicting the place towards which the ball is moving and executing a displacement movement in order to approach this place. In the second case, the anticipation is responsible for the spatial and temporal coincidence of the act of striking the ball with the path of the moving ball. Place coincidence anticipation is based on the perception of the opponent’s movement or of the early phase of the ball’s path. This information can be treated as a place coincidence (locomotion) anticipatory stimulus, indirectly indicating the place towards which the subject’s displacement movement should be carried out. The final phase of the ball’s path is the basis for the movement coincidence anticipation, and can be regarded as a ball hitting anticipatory stimulus, allowing the prediction of the ball hitting movement (its shape in the space and the speed). The anticipation enables hitting a ball in the optimal spot on the ball’s flight trajectory to direct it toward the chosen place on the opposite side of the court with the highest precision. In other words, the place anticipatory stimuli indicate where to run to hit the ball, while ball hitting anticipatory stimuli show, in what spot to hit the ball. The sequential ball-hitting movements (sequence of four different movements) can be initiated by place or ball hitting anticipatory stimuli. The movements initiated by place anticipatory stimuli are called anticipatory ball-hitting movements. The initiation of these movements on the basis of ball hitting stimuli is characteristic of orientation ball-hitting movements. Place coincidence anticipation is based on memorizing the way in which the ball was struck by the opponent and the place where the ball ended up. Memorized experiences of this kind make up an anticipatory schema (?apszo, 1999a,b, 2000a), the essence of which is similar to Schmidt’s motor schema (Schmidt, 1975, 1988). In every spot of the court there are a few ball hitting movements by opponent (that make tactical sense). For example, in the base line play in the forehand corner (for a right-handed player) there are 3 possible kinds of strokes (forehand topspin, slice or drop-shot). For each of these strokes there are only few places where it makes sense to direct the ball by the opponent. In the case of forehand topspin it makes sense to direct the ball across the court, in the middle of the court and down the line. By memorizing the way of performance of such strokes with the places where the ball was directed we create the “skill anticipatory schema in a defined situation”, in this case “forehand topspin anticipatory schema in the right corner of the court”. The right corner forehand topspin, slice and drop-shot anticipatory schemas constitute a bigger anticipatory structure, which we have called the “situation anticipatory schema”. The schema has a hierarchical structure. At the upper stage of the schema relations of the ball fight trajectories with the kinds of strokes applied to hit so flying balls in the past are memorized. At this stage we recognize what kind of stroke our opponent is going to apply to hit the ball. At the second (lower) stage skill anticipatory schemas that allow us to recognize in what direction our opponent is hitting the ball are located. The moment of initiating the locomotion movement and the direction of the movement in response to the opponent’s ball-hitting movement is determined by the speed and the accuracy of the place coincident anticipation. Our not published study on anticipation based on a video analysis has shown that Arantxa Sanchez Vicario initiated locomotion movements when a ball was in the distance of about 1 meter from the spot where it was struck by opponent, while Steffi Graf started displacing herself when the ball was about 4 meters from the ball-hitting spot. The very high place coincidence anticipation ability allows Arantxa Sanchez Vicario and Michael Chang to play against taller players successfully. The anticipation is responsible for fast initiating locomotion movements and an accurate prediction of the ball’s flight place. The well anticipating players don’t make a lot of correction movements; they displace themselves exactly to the place which is optimal to hit the ball. The place coincidence anticipation is an unconscious (automatic) information process. The concept of sequential ball-hitting movements, place and movement anticipatory stimuli, anticipatory and orientation ball-hitting movements and situation anticipatory schemas was used to design the tennis play simulator version I and II. The purpose of this paper is to present the construction and diagnostic possibilities of the tennis play simulator II, which was designated to test and improve orientation and the anticipatory ball-hitting movement speed in practice and competitive conditions. Eight highly-skilled American tennis players (av. age 14.2 years) with an average of 6.1 years of special training in tennis participated in the study. One of the tested players was located on the ATP list.

Method

Tennis play simulator The simulator, used in the study, is a second (advanced) version of the tennis play simulator. Both versions of the simulator consist of a computer, a controller and a specific simulator (Lapszo, 2002). The differences between the first and the second version are in construction of the specific simulator. In first version of the specific simulator the tactical sensor were used to identify the instant of reaching the spot of ball hitting. In the second version we have applied the sensors that enable performing the simulated ball-hitting movements with a tennis racket and in the way like in a real play. The first version of the simulator can be used to test children who cannot play tennis yet. The second version is designed to test high-skilled tennis players. The specific simulator- version II is presented in Fig. 1.

Fig.1. The drawing of the tennis play simulator II

Fig.1. The drawing of the tennis play simulator II.

This simulator consist of: 10 anticipatory stimuli lamps (red, yellow), 3 split step lamps (white), start (green) and end (blue) lamps, 10 sensors enabling performance of ball strokes with a tennis racket (8 base line strokes and 2 volleys). Anticipatory lamps are located in the boards in shape of a tennis racket head. The boards are put on special stands. Split step lamps are located in 3 places (middle of the court, on the left and right side. Fig. 1). In the boxes of the split step lights also 3 speakers are placed. The sensors consist of: a flexible steak with a tennis ball at the end, a plastic box with a lamp and a speaker, a stand and a base. The controller controls switching on lamps, speakers and sensors. It also measures the times of activation of these devices. The computer enables preparing the measurement tests. A special language was written to prepare the tests. The language is very user-friendly. The simulator was used to test the speed of simulated ball hitting movements in orientation (orientation ball hitting movements) and anticipation (anticipatory conditions). In the orientation conditions the movements are performed in response to switching on the lights in the sensors (orientation stimuli). The audio signal accompanies the lights in the sensors. In the anticipatory conditions first the anticipatory stimulus lamp is being switched on and then, with defined delay, (ball flight) lamp in the sensor. The audio signal also accompanies the lights on the boards (anticipatory stimuli) and in the sensors (orientation stimuli). Anticipatory and orientation lamps can emits the light in two colors: yellow and red. The players were instructed that the yellow color means “the ball is flying cross court”, the red one “the ball is flying down the line”. The players were also instructed to perform the simulated ball hitting movements in the way as in a real play. Their task was to displace themselves in the direction of the proper sensor and hit the sponge ball located on the top of the flexible stick as fast as possible in response to anticipatory lights (anticipatory conditions) or lights in the sensors (orientation conditions). The symmetric pairs of anticipatory stimuli lamps were associated in a computer program with symmetric pairs of sensors. For example, lamps number 1 and 10 (Fig. 1) were associated with sensors number 4 and 7. The yellow light of lamp No 1 indicated that the player should run and hit the ball in sensor No 7. If the light was red, she/he should hit the ball by sensor 4. The following pairs (anticipatory schema) were created (anticipatory lamps-sensors): 1,10–4,7; 2,9–2,9; 3,8–1,10, 4,7–3,8; 2,9–5,6 (volleys), 5–7,8 (service on forehand side), 6–3,8 (service on backhand side). The players learned this anticipatory schema. The anticipatory movements tests started from coming on the green light in the information box – which meant – “be ready”, next the white light came on - which meant- “perform split step” and then the light on the defined board (anticipatory stimulus) and with delay (ball’s flight) in the defined sensor (orientation stimulus) was presented. In the orientation movements tests the lights on the boards (anticipatory stimuli) did not come on. In orientation conditions after performing a split step the locomotion movements were stimulated by the light in the sensors. The speed of anticipatory (Ta) and orientation (To) ball hitting movements was measured by the time (with precision to milliseconds) elapsing from the instant of sensor activation to the instant of hitting the ball (on top of a flexible stick) in the sensor. The shorter the time was, the higher was the speed of the movements. The tested movements were performed in series (tests) of 6–8 movements in practice (pc) and competitive conditions (cc). The average speed for all movements in the series was the result of the tests. The players practiced simulated ball-hitting movements and learned the anticipatory schema before the research started. The research consisted of 5 measurement sessions. One session lasted half an hour. Two tennis players could participate in one session. The measurements were conducted in the morning. The whole research lasted 5 days. It is possible to test players twice per day. In such a case the research would last only 3 days. Running the tests The speed of orientation and anticipatory-ball hitting movements were measured in 6 series. Each series of orientation ball-hitting movements consisted of 8 movements initiated in the middle of the base line. The movements were stimulated only by the lamps in the sensors. The order of stimuli in each series was different. The players performed 4 backhand (Fig. 1, sensors 1,2,3,4) and 4 forehand (sensors 7,8,9,10) strokes. Each series of anticipatory ball-hitting movements consisted of 6-8 movements started in the return position. The tested player first performed return (Fig. 1, sensors 4 or 8 for forehand return, sensors 3 or 7 for backhand return), next combination of base line strokes (sensors 1,2,3,4 – backhands, sensors 7,8,9,10-forhands), finally volley (not in all series, sensor 5 – backhand volley, sensors 6-forehand volley). Three series started from right and 3 series from left return position. The players performed the orientation and anticipatory ball-hitting movements in practice and competitive conditions. In the practice conditions players were only instructed to perform tested movements as fast as they could without any additional motivation. In the competitive conditions players were playing a game of 6 points in both orientation and anticipatory conditions. We have manipulated the speed of the opponent’s play (speed of a simulated ball flight). To win a point players had to perform a series of 8 movements (orientation conditions) and 6-8 movements (anticipatory conditions) in the required time. The speed of play was controlled by a special coefficient (Csp) which determined the speed of a simulated ball flight. In the speed endurance study players played for 12 points only in the orientation conditions. The speed of play (Csp) was lower by 15% (for example Csp = 1.3 for player 1, for whom the maximum play speed coefficient Msp-oc was 1.0) below the maximum speed of play (Msp), for which the tested player was still able to win the points. The lower the coefficient Csp was, the higher was the play speed. The change of 0.1 of the coefficient Csp caused the change in the speed of play by 5%.

Results

The following psychomotor factors were obtained in the presented research project: - speed of orientation (To) and anticipatory (Ta) ball-hitting movements in practice (To-pc, Ta- pc) and competitive (To-cc, Ta-cc) conditions, - coefficients of the maximum speed of play in orientation (Msp-oc) and anticipatory (Msp-ac) conditions, - indexes of competitiveness in orientation (C-oc) and anticipatory conditions (C-ac), - anticipation of the ball flight in practice (A-pc) and competitive conditions (A-cc), - speed endurance (Se), - index of psychomotor efficiency (Ie). The average values of the factors are presented in form of profiles (Fig. 2) that constitute their graphic presentation in the same scale (Skorny, 1974, Lapszo. 1999b). In the same figure the profiles of the best player (located on the ATP list), the whole tested group and a chosen player (player 5) are shown.The speed of orientation and anticipatory ball hitting in practice (To-pc, Ta-pc) and competitive (To-cc, Ta-cc) conditions was calculated as the average speed for all 6 tests (series). In both conditions the anticipatory movements speed (Ta) was much higher than orientation movements speed, what we have expected. The results indicate, place. anticipation of ball flight enable much faster reaching the ball in tennis than that orientation of the ball fight spot. The speed of orientation ball-hitting movements (To) reflects the motor speed of a tennis player, which mainly depends on the body speed capability and motivation. In turn, the body speed capabilities depend on the proportion of the white and red fibers in the muscles and on the anaerobic power (the ability to use energy from anaerobic sources). The speed of anticipatory ball-hitting movements reflects the psychomotor speed of players, which means the speed of information and motor processes in anticipatory motor reacting. The body speed capabilities, anticipation ability and motivation have influence on the psychomotor speed. Anticipation depends on the ability to create anticipatory schemas (anticipatory experience) and on the speed and accuracy of information processes that allow recognizing anticipatory stimuli, choosing a proper movement and program it with high precision. Motivation is an energizing process of the human psychomotor system, directed at achieving a defined goal (Schmidt, 1988). We have tested orientation and anticipatory ball-hitting movements in practice conditions, in which the players had to motivate themselves to perform movements as fast as possible and in competitive conditions in which additional motivation occurred resulting from the play for points with a simulated opponent. We found statically significant differences between To-pc and To-cc (p<0.02) and between Ta-pc and Ta-cc (p<10-4).

Fig. 2. Profiles of the tested psychomotor factors for the best player

Fig. 2. Profiles of the tested psychomotor factors for the best player, the tested group and a freely chosen player (player 5).

The findings indicate that the play for points causes an increase in the speed of ball-hitting movements in both conditions. We analyzed the relative difference between orientation and anticipatory movement speed in practice and The profiles of tested factors 0.371.100.430.750.261.381.651.331.181.040.480.320.600.900.600.930.091.001.501.650.280.710.351.280.530.490.051.751.400.651.251.31.651.830.100.280.0000.5001.0001.5002.000To-pcTo-ccMsp-ocC-ocTa-pcTa-ccMsp-acC-acA-pcA-ccSeIeTested factorsBest playerGroupPlayer 5 IV Congreso Mundial de Ciencia y Deportes de Raqueta competitive conditions for particular players. The differences were treated as indexes of competitiveness (C-oc – for orientation conditions; C-ac – for anticipatory conditions; Fig. 2). The higher indexes C-oc and C-ac are, the more competitive is the player. The indexes show a relative (in percent – 0.6=60 %) increase in the speed of orientation (C-oc) and anticipatory movements (C-ac) as a result of an increase in motivation caused by playing for points.The play for points also enables obtaining the coefficients of the maximum speed of play in orientation ( Msp-oc ) and anticipatory (Msp-ac) conditions (Fig. 2). The lower the coefficients Msp-oc and Msp-ac were, the higher was the speed of the opponent’s play, for which the player was still able to win the points, for example for Msp-ac = 1.1 the play was 10% faster than for Msp-ac = 1.3. We have also tested the ball fight (place coincidence) anticipation in practice (A-pc) and competitive (A-cc) conditions (Fig. 2). The indexes A-pc and A-cc were calculated using the following formulas: A-pc = (To-pc – Ta-pc)/ To-pc and A-cc = (To-cc – Ta-cc)/ To-cc. The indexes A-pc and A-cc express the relative increase in the speed of ball- hitting movements as a result of the ball’s flight spot (place) anticipation. The order of movements in the tests of anticipatory and orientation movements used to calculate indexes A-pc and A-cc was the same in practice and competitive conditions. The study has shown that the speed benefit resulting from anticipation of the ball’s flight place is much larger in competitive (70%) than practice (37%) conditions. The speed endurance was tested in form of play for points (12). We have introduced the index of the endurance – Se (Fig. 2), which was calculated by the ratio of the number of lost points to the number of scored points multiplied by the coefficient of the play speed (1.3 for player No 1). A smaller Se index means larger speed endurance.All obtained factors in this study were then used to calculate the index of psychomotor efficiency Ie (Fig. 3). The following formula was used to calculate the index Ie: Ie = [(C-oc+C-ac+ A-pc+ A-cc)/(To-pc+To-cc+Msp-oc+Ta-pc+Ta-cc+Msp-ac+Se)]*5 The Ie index was calculated as a ratio of the sums of the above factors. The numerator was the sum of factors that expressed higher efficiency when they had higher values. The denominator was the sum of factors that reflected higher efficiency when they had lower values. The ratio was next multiplied by 5 to make it compatible with the scale of all the tested factors. The index of psychomotor efficiency comprehensively expresses the efficiency. The larger is the index, the higher is the psychomotor efficiency related to tennis game. Correlation of tested factors with sporting results The correlation of the tested psychomotor factors of psychomotor efficiency, obtained for particular players with sporting results (ranking) was also examined. The obtained correlation coefficients are presented in Fig. 3. Fig. 3. The profile of correlation coefficients between tested psychomotor factors

Fig. 3. The profile of correlation coefficients between tested psychomotor factors and sporting results ranking for tested group.

All the tested factors strongly correlate with sporting results. These findings are in disagreement with studies by Keele (1982) and Meeusen (1991), who found that movement time (motor speed) and anticipation do not differentiate highly proficient and less skilled players. Our research indicate that the tested factors reflect psychomotor capacities which are important in a contemporary tennis game. The obtained results support our study on psychomotor predispositions in a table-tennis game (Lapszo, 1997) that also showed a strong correlation of the ball-hitting movement speed, anticipation and concentration with sporting results. Unfortunately, not all obtained in this study correlation coefficients are statistically significant because the number of tested players was not large (8 players). The profiles of the best and a freely chosen player results were presented in the same figure with the tested group profile. The comprising of the chosen player’s profile with the whole group’s and the best player’s profiles allow recognizing the strong and weak aspects of the chosen competitor. The best player, who was on the ATP list at the time of the research, obtained better results than the group with respect to all tested factors.

Conclusions

The presented research project enables drawing the following conclusions: • The simulator allows simulating 22 different directions of ball’s flight . • 10 different ball-hitting movements can be simulated (5 backhand and 5 forehand strokes). The applied sensors allow the simulated ball-hitting movements to be performed in the way as in a real play. • The simulator enables testing 12 psychomotor factors related to tennis game in orientation and anticipatory, practice and competitive conditions. The factors reflect the motor (body speed), and psychomotor (brain and body speed) speed, competitiveness, anticipation ability, speed endurance and complex psychomotor efficiency related to tennis game. Coefficients of correlation between tested factors and sporting ranking 0.650.730.810.710.780.730.970.940.810.760.760.890.000.501.001.50To-pc(p=0.11)To-cc (p=0.04)Msp-oc(p=0.03)C-oc(p=0.18)Ta-pc(p=0.07)Ta-cc(p=0.3)Msp-ac(p=0.14)C-ac (p=0.05)A-pc(p=0.02)A-cc(p=0.22)Se(p=0.07)Ie (p=0.05)Tested factorsCoefficients ofcorrelation • The coefficients of correlation between all the tested factors and sports ranking are very high. These findings suggest that all these factors can have a strong influence on sporting results. • Anticipatory ball-hitting movements are much faster then orientation ball-hitting movements. • Play for points causes the increase in speed of orientation ball-hitting movements only by 5% (Fig. 2, C-oc,), while in the speed of anticipatory ball-hitting movements even by 53%. It suggests that the increase in attention concentration, which requires anticipatory reacting, is much higher in competitive than in practice conditions. • The speed benefit (an increase in the speed of ball-hitting movements) of the ball’s flight anticipation is much larger in competitive (70%) than practice (37%) conditions. • The comprising of the profiles of best player (placed on the ATP list) and whole group with a chosen player’s profile enables the recognition a of the weak and strong sides of the player.

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