Physiological aspects of competitive tennis: a review of the recent literature

Transcription

1 Review Article Physiological aspects of competitive tennis: a review of the recent literature Tennis activity Tennis is a sport that requires a mixture of complex skills (technical, tactical, psychological) and physical attributes (speed, agility, endurance, strength, balance, flexibility, anticipation, power). (2) Match play is defined by intermittent exercise: short bout of high intensity (< 10 seconds) are interrupted by short recovery bouts (10-20 seconds) and periods of longer duration ( seconds). During this time, a player runs about 3m per stroke, (3) changes direction four times by point and completes explosive efforts during a match. (4) What is the physical profile of a male and a female tennis player? - Anthropological characteristics A summary of the physical characteristics of tennis players across the reviewed studies is presented in Table 1. It has been well described that there are specific physical characteristics in many sports, such as the anthropometric profile, that indicate whether the player would be suitable to compete at the highest level in a specific sport. (5) The quantification of morphological characteristics of elite athletes can be a key point to sports performance. However, at present, only few studies have specifically analyzed the physical characteristics of young and adult tennis players. The mean height of male players ranged from ± 5.5 cm in young players (7 and 8 years) (6) to ± 5.5 cm in 8 professional players during the Olympic Games in Sydney. (7) Concerning mean body mass, the Caroline Martin, Jacques Prioux J Med Sci Tennis 2011;16(3): Abstract Elite tennis players and coaches need some knowledge about the nature of physiological requirements of tennis matches. Indeed, according to the specificity principle of training, training programs must be both physiologically and mechanically specific to the demands of the tennis. (1) In this way, the aim of this review is to give an oversight of the recent results from scientific researches about physiological aspects of competitive tennis to help players and coaches to obtain optimal tennis performance. values approximate usually kg for male players and for female players (see Table 1). For this range of values, highest mean body mass is reported for professional players. (7,8) Percent body fat ranged from 7.3 ± 1.2 %9 to 16.5 ± 6.7 % in male professional players (10) and 19.1 ± 3.6 % 11 to 28.5 ± 3.7 % in female players. (12) It is important for tennis players and coaches to understand that, although a low percentage of body fat is desirable, it has been shown that muscle mass and not body fat are performance-determining in most athletic endeavours. (13) Sanchez-Munoz et al. (12) have evaluated the anthropometric characteristics and body composition of 123 elite junior tennis players (57 males and 66 females). They compared the values between the first 12 and the lower ranked male and female players. Their results showed that there were no significant differences in height and weight between the first 12 and the lower ranked boys, while the first 12 girls were significantly taller than the lower ranked girls. Moreover, the first 2 girls presented wider humeral and femoral breadths than the lower ranked players. The authors have assumed that these differences could influence the playing style in junior women, allowing a more aggressive and attacking playing pattern, as increased height is an advantage when serving. Kraemer et al. (11) have compared the physiological adaptations between periodized (P) and non-periodized (NP) resistance training over 9 months in women collegiate tennis players. They observed that fat-free mass increased and percent body fat decreased significantly Table 1. Mean values (± SD) of anthropometrical parameters from tennis research studies. M1 : first month, M10 : tenth month, B : before training, A: after training References Participants Age Height Body Body fat (%) (year) (cm) mass (kg) Berdejo- 7 elite children players 10.9 ± ± ± 7.6 M1: 23.9 ± 7.1 / M10 : 21.3 ± 6.8 Delfresno D, (3 males and 4 females) et al. (14) Bergeron MF, 10 male college players 20.3 ± ± ± ± 4.5 et al. (16) Bloomfield J, 65 male regular players ± ± 4.5 / et al. (6) ± ± ± ± 5.8 Elliot BC, 8 male professional players / ± ± 9.0 / et al. (7) 12 female professional players / ± ± 7.7 Girard O, 12 well trained male players 23.4 ± ± ± ± 3.0 et al. (19) Hornery DJ. (9) 14 professional male players 21.4 ± ± ± ± 1.2 Kraemer WJ, 27 female collegiate players et al. (11) placed in 3 groups 1) non linear periodized resistance training 19.2 ± ± ± 7.7 B: 22.9 ± 3.9 / A:19.1 ± 3.6 2) non periodized resistance training 18.6 ± ± ± 7.8 B: 23.7 ± 4.9 / A: 21.6 ± 2.9 3) control group 19.3 ± ± ± 7.6 B: 22.6 ± 5.7 / A:21.4 ± 4.3 Leone M, et al. (76) 15 female regional junior players 13.9 ± ± ± 8.3 / Leone M, et al. (75) 35 male regional players 14.5 ± ± ± 11.0 / Morante SM, 25 male professional players 23.9 ± ± ± ± 6.0 et al. (56) Sanchez- 57 male elite junior players 16.2 ± ± ± ± 3.6 Muñoz C, (Davis Junior Cup) et al. (12) 66 female elite junior players 15.9 ± ± ± ± 3.7 (Fed Junior Cup) Sanchez-Moysi J, 9 professional male players 26.0 ± ± ± ± 6.7 et al. (10) after P and NP training. The absolute change in fat-free mass over the 9 months was significantly greater in P (3.3 ± 1.7 kg) than in NP (1.6 ± 2.4 kg). In the same way, Berdejo-del-Fresno et al.(14) who assessed 7 elite children tennis players (3 boys and 4 girls) over one season to evaluate body composition changes. They found that during a season, children tennis players increased lean and bone percentage, and decreased abdominal and total fat percentage. - Physical attributes The maximal oxygen uptake (VO 2 max) values would classify high level tennis players as being highly anaerobically trained. (2) Indeed, VO 2 max values in adult competitive high level tennis players have varied between 50.3 ± 3.9 ml.min -1. kg -1 (15) and 58.5 ± 9.4 ml.min -1.kg -1, (16) with the majority of values greater than 50 ml.min -1.kg -1 (see Table 2). Beyond puberty, the mean VO 2 max values relative to lean body mass is 10% higher for male than for female players. (12) 6 7

2 Table 2. Mean values (± SD) of VO2max from tennis research studies. HRmax = maximal heart rate value, VO2 max = maximal oxygen uptake value. References Participants Test VO2max HR max (bpm) (ml.min- 1.kg- 1 ) Berdejo-Delfresno D, 7 elite children players (3 boys and 4 female) 20 m shuttle run test 54.2 ± 3.3 / et al. (14) Bergeron MF, et al. (16) 10 male college players Treadmill test 58.5 ± ± 6.3 Dansou P, et al. (36) 10 male regional players Treadmill test 58.5 ± ± 2.0 Girard O, et al. (15) 7 male club players Treadmill test 50.3 ± ± 8.5 Kraemer WJ, et al. (11) 27 female collegiate players Treadmill test 45.7 ± 2.2 / 51.0 ± 3.2 / Morante SM, et al. (56) 6 male professional players Treadmill test 56.7 ± ± 9.0 Murias JM, et al (51) 12 male national players Treadmill test 55.5 ± 2.3 / As high level competitive tennis players need a physiological regeneration between points, as well as between matches and tournaments, a high VO 2 max is important as it can help to avoid fatigue, and aid in recovery and long training, thus promoting continuous success. In this way, Banzer et al. (17) have carried out a 7-year prospective case report on the relationship between VO 2 max during preparation and the following year s entry ranking for a top player. They showed that during the period that the ATP ranking ranged from 6 97, VO2max ranged from ml.min -1.kg -1, averaging 61.1 ml.min -1.kg -1. A strong relationship was observed between VO2max and ATP entry ranking over time (Figure 1). Figure 1. Evolution of the maximal oxygen uptake of a professional tennis player as a function of entry ranking (according to Banzer et al. (17) ) Kovacs et al. (18) evaluated the impact of a 5 week unsupervised break from regular training in top collegiate players. They showed that this interruption of normal training caused significant decreases in physical attributes (speed, power and aerobic capacity). An 11 % reduction of VO 2 max has been observed at the end of the break. To test VO 2 max of player, Girard et al. (19) have created a tennis specific fitness test (FT) that consists of repeated displacements replicating the game at increasing speed on a court. The values of VO 2 max obtained for 9 junior competitive players were significantly higher in the FT (63.8 ± 3.0 ml.min -1.kg -1 ) than in the treadmill test (58.9 ± 5.3 ml.min-1.kg -1 ). In the same way, Ferrauti et al. (20) have evaluated and validated the Hit & Turn Tennis Test to obtain a reliable indicator for tennis specific endurance. These field tests can be routinely used to accurately prescribing appropriate aerobic exercise training. - Strength Strength is required for improving ball velocity and reducing injuries. Objective measurement of strength has been performed in elite, recreational and junior tennis players. For elite male adult (21), female adult (22) and junior tennis players (23), shoulder rotation muscle (external and internal rotators) strength imbalances have been reported and tends to alter the normal functional ratio between rotator cuff muscles and could lead to shoulder injuries. Moreover, Ellenbecker and Roetert (24) reported that elite level male tennis players have symmetric trunk rotation strength while the elite female players have slightly greater backhand rotation strength (by 4-8%) than forehand rotation. These results could be explained by the low percentage of female players that use one-handed backhand stroke. Isokinetic dynamometers have been used to compare the strength between dominant and nondominant arm in tennis players. It has been reported significant greater internal rotation, extension and flexion (25), horizontal abduction and adduction (26) in the dominant arm compared with the nondominant arm in elite players. For adolescent elite tennis players, it has been reported that upper trapezius and serratus anterior strength were significantly greater on the dominant side, while middle and lower trapezius strength showed no side differences. (27) Greater dominant arm wrist flexion extension and forearm pronation strength is common and normal in elite female tennis players. (28) All these results indicate sport specific muscular adaptations in the dominant tennis playing arm. However, no significant bilateral difference of strength between the dominant lower limb and the non-dominant side has been reported. (29) Ellenbecker et al. (30) have evaluated the impact of a 6-week training of concentric or eccentric isokinetic exercise. They reported significant increases in concentric and eccentric internal rotation, external rotation strength and maximum serve velocity in the concentric training group. The eccentric training group did not show increases in external rotation strength and serve velocity. These results provide a rationale for including isokinetic training of the rotator cuff for conditioning and performance. - Talent Identification and Physical Attributes For talent identification purposes, correlation studies have been carried out to know which physical attributes influence tennis performance and have a strong relationship with results and ranking. (31,32) Girard and Millet (32) have shown that speed, vertical power abilities, and maximal strength in the dominant side were significantly correlated with tennis performance for competitive teenage players (13.6 years). Only one correlation (hexagone test for ability and speed) has been reported between physical performance tests and the rankings of junior players. (31) Quinn and Reid (33) proposed physiological and physical tests to help coaches and players to determine where they are before contemplating the direction and pace you should go. Physiological demands involved in tennis matches - Energy Systems According to Kovacs (2) utilizing the correct energy system during training will improve performance during matches. As a consequence, it is important to know the involvement of energy systems during tennis matches. As tennis activity is characterized by periods of highintensity exercise (powerful serves and groundstrokes, rapid changes of direction, explosive nature of the displacements ) disrupted by periods of low-intensity exercise of various duration (active recovery between points or sitting periods during changeovers), one may have argued to classify it as anaerobic predominant activity requiring high levels of aerobic conditioning to aid in recovery between points and matches. (34) - Oxygen Uptake Different studies have used portable gas analyzers to have an oversight of mean oxygen uptake during tennis matches (see Table 3). It has been reported that VO2 levels during matches vary from 23.3 ± 3.0 ml.min -1. kg -1 for recreational veterans (35) to 40.3 ± 5.7 ml.min -1. kg -1 for club male players. (15) This corresponds to about 60 % of VO 2 max, with values ranging from 46 % to 80 % of VO 2 max (see Table 3). During matches, mean VO 2 reached 60 % of the VO 2 max for 80 % of the duration of the match. During the points, VO 2 varied from 70 to

3 Table 3. Mean values (± SD) of physiological parameters. HR : heart rate, [La] : blood lactate concentration, VO 2 : mean oxygen uptake, % VO 2 max : percentage of VO 2 max, RPE : rate of perceived exertion. Adv : advanced, Rec : recreational. References Surface Sex Level HR (bpm) [La] VO 2 % VO 2 max Peak core Body mass RPE (mmol.l -1 ) (ml.min -1 temperature deficit (%).kg -1 ) ( ) Dansou P, et al. (36) Hard Male Club ± ± ± ± 2.5 / / / Murias JM, et al (51) Clay Male National 143 ± ± ± ± 6.5 / / / Hard 135 ± ± ± ± 4.80 Girard O, et al. (15) Clay Male Club ± ± ± ± / / / Hard ± ± ± ± Martin C, et al. (41) Clay Male National 154 ± ± 1.20 / / / / / Hard Female 141 ± ± 1.80 Fernandez- Hard Female International 161 ± ± 0.80 / / / / / Fernandez J, et al. (39) (juniors) Fernandez- Clay Female International / 2.2 ± 0.90 / / / / 12.2 ± 2.4 Fernandez J, et al. (43) Fernandez- Clay Male Adv Veterans ± / 24.5 ± 4.10 / / / / Fernandez J, et al. (35) Rec Veterans ± ± 3.0 Hornery DJ, et al. (55) Clay Male International 152 ± 15 / / / 38.5 ± ± 0.56 / Hard 146 ± ± ± 0.49 Smekal G, et al. (37) Clay Male National / 2.07 ± ± ± 7.20 / / / % of VO 2 max and decreased rapidly during the changes of side. (36) - Heart Rate The literature shows that heart rate (HR) is measured as indices to evaluate the intensity and the psychological stress associated during practice. It has been reported that mean HR values during matches vary from 135 to 161 bpm (see Table 3) rising to bpm during long and intense rallies. (15,37) The mean percentage of maximum HR during matches has been reported to approximate 86 % and to be not significantly different from the 83 % measured during recovery (excluding the rest periods between points and games). (16) However, care should be taken when looking at the results of mean HR values as they do not accurately represent the intermittent nature of the tennis match. (2, 38) Indeed, HR values vary continuously during a match due to the continual stop-start movements and intermittent nature of the sport. (16, 36) (Figure 2). It has been reported that players spent about 13% of match duration at intensities higher than 90% of HRmax. Moreover, the serving situation influences HR during male and female matches: mean HR values were significantly higher when serving than when receiving. (39, 40) This result could be explained by the higher psychological stress and sympathetic activity related to the importance to win the service games. (38) Figure 2. Typical evolution of the heart rate of a tennis player during a simulated match (according to Dansou et al). (36) FC = heart rate, Temps = time. - Lactate Concentrations Lactate concentrations [La] is measured as indices to evaluate the intensity of tennis match play and to obtain an oversight of the energy production from glycolytic processes. (38) Mean [La] values during matches remain low (from 1.16 to 5.7 mmol.l -1 ) (see Table 3). Indeed, the periods of rest during match seem sufficient to allow players to reduce the metabolism products. (16,41) [La] values can rise to 8 mmol.l-1 during long and intense rallies, (41) suggesting an increased participation of glycolytic processes to energy supply. When [La] exceed 7-8 mmol.l-1, technical and tactical performance decreases. (42) Therefore, it is important to prepare players properly to deal with these high-intensity situations and to use optimally resting times. The discrepancies between studies concerning mean [La] values are probably the results of differences in the characteristics of the subjects and the experimental design (number and time of blood taking). However, care should be taken when looking at the results because [La] values only reflect the level of activity during the few minutes before sampling. - Rate of Perceived Exertion Rate of perceived exertion (RPE) can be defined as the subjective intensity of effort, strain, discomfort and/or fatigue that is experienced during physical exercise. (38) There are few studies describing the RPE responses to official tennis matches. (40, 43) Mean values ranged from 12 ( light ) to 13 ( somewhat hard ) with peak value of 17 ( very hard ). With the 15-category Borg RPE scale, RPE was significantly higher in service games than in receiving games for professional male players, (40) but not for female players. (43) Monitoring RPE may be a useful technique for regulating on-court tennis training intensity. (40) 10 11

4 Influence of playing style, age, gender, and wheelchair tennis on physiological parameters - Playing style and velocity It is interesting to note that the playing style has been shown to have an influence on the matches characteristics and the values of physiological parameters during matches. Indeed, Bernardi et al. (44) reported that the duration of each rally ranged from 5.13 ± 0.9 s (21 ± 2 % of the total time) for attacking players to 15.7 ± 4.5 s (38.5 ± 4.9 %) for baseliners. As a consequence, lower HR and VO 2 levels were observed for attacking players (123 ± 9 bpm and 30.9 ± 7.69 ml.min -1.kg -1 ) than for baseliners (159 ± 6 bpm and 37.5 ± 7.79 ml.min -1.kg -1 ). Fernandez-Fernandez et al. (45) reported that physiological responses (HR, % HRmax, VO 2, % VO 2 max) increased significantly with hitting velocity during training sessions. - Age Different researches investigated the physiological profile of veteran tennis players (46,47) and found that the relative demand on cardiopulmonary capacity approximates 60 % of VO 2 max. During matches, cardiac involvement is greater in veterans than in young players. (47) Recently, it has been shown that physiological demands (HR, VO 2, energy expenditure) were similar between advanced and recreational veteran tennis players. (35) Higher VO 2 values have been reported for younger players than for adults. (15) - Gender Although differences exist in the activity profile of female matches compared to male matches (less strokes per second, fewer aces, fewer services games won, more double faults, less points to the net, more baseline rallies), (48, 49, 50) similar physiological responses have been reported in female matches43 than in previous studies about male matches. (15,37,51) - Wheelchair Tennis Players Roy et al. (52) evaluated the physiological responses of players during a competitive wheelchair tennis match. They reported the following mean values: 69.4 ± 8.9 % of HRmax, 49.9 ± 14.5 % of VO 2 max. In a comparison between wheelchair basketball and wheelchair tennis, it has been shown that average match heart rate and average VO2 were lower during tennis play compared with basketball. (53) - Playing in the Heat Tennis players are subjected to high-heat loads during matches in hot environment. (54, 55, 56) High temperatures can impair central nervous system function and muscle function. (38) Tippet et al. (54) showed that on hot conditions (>30 C), mean sweat during matches was 2.0 ± 0.5 L/h for female professional tennis players, resulting in 1.2 ± 1.0% reduction in body mass. Precooling, intermittent cooling interventions and break in play afforded physiological advantage and decrease core temperature (54, 55) during tennis matches. Court Surface - Matches Characteristics Competitive tennis players are used to playing multiple tournaments on different court surfaces. The International Tennis Federation (57) classifies court surfaces into five categories according to court pace: slow, medium-slow, medium, medium-fast and fast. It is well known that the court surface influences the tennis ball rebound and as a consequence the ball speed. (58, 59) Indeed, court pace depends on the friction between the ball and the court surface (coefficient of friction) and somewhat by the coefficient of restitution. Slower surfaces, such as CL courts (CL), are characterized by higher friction and restitution coefficients than faster surfaces. This results in a high and relative gentle bounce and slows down the ball on CL58. The player will benefit from more time to get to the ball on CL than on faster surfaces. The surface allows a player to retrieve more balls, prolonging rallies before making errors or not being able to reach a ball played by the opponent. As a consequence, the court surface influences the match s technical characteristics - that is, its effective playing time (EPT), effective resting time (ERT), total match duration (MD), mean rally duration (MRD), resting time between points (RT), number of strokes per rally (SR), distance ran per point (DRP) (Table 4). The EPT, defined as the duration during which the ball is really in play is, on average, significantly longer on CL (20-30% of total match duration) than on faster surfaces, such as hard (H) courts (10-15% of total match duration) (Table 4). O Donoghue and Ingram (50) conducted a notational analysis of singles events at all four Grand Slam tournaments between 1997 and 1999 to determine the influence of the surface on tennis matches. Rallies of 6.3 ± 1.8 s at the Australian Open (H), 7.7 ± 1.7 s at the French Open (CL), 4.3 ± 1.6 s at Wimbledon (grass) and 5.8 ± 1.9 s at the US Open (H) were recorded. Rallies were significantly longer at the French Open than at any other tournament and significantly shorter at Wimbledon than at any other tournament. In the same way, it has been shown that SR, DRP are significantly higher on CL than on H. All these results can be explained by the tactical behavior used by players according to the court surface. For example, a more aggressive and attacking game is associated with faster surface such as grass. Indeed, it has been reported that there was significantly more baseline rallies on CL at the French Open (51 % of points) than at all other tournaments (Australian Open : 46 % of points, US Table 4. Mean values (± SD) of match characteristics. MD : match duration, MRD : mean rally duration, MRT : mean resting time, EPT : effective playing time, DRP : distance ran per point, SR : shots per rally. References Surface Sex Level MD (min) MRD (s) MRT (s) EPT (%) DRP (m) SR Murias JM, et al (51) Clay Male National / 8.8 ± ± 8.6 / 11.6 ± 1.5 / Hard 7.2 ± ± ± 1.8 Girard O, et al. (15) Clay Male Club / 7.2 ± 1.7 / / 9.8 ± ± 0.5 Hard 5.9 ± ± ± 0.4 Martin C, et al. (41) Clay Male National 56.9 ± ± 0.2 / 26.2 ± 1.9 / / Hard Female 56.0 ± ± ± 2.0 Fernandez- Hard Female International / 8.2 ± ± ± 3.8 / Fernandez J, et al. (39) (juniors) Fernandez- Clay Female International / 7.2 ± ± ± 6.1 / 2.5 ± 1.6 Fernandez J, et al. (43) Mendez-Villanueva A, Clay Male International / 7.5 ± ± ± 4.9 / 2.7 ± 2.2 et al. (8) Hornery DJ, et al. (55) Clay Male International 79 ± ± ± 3.3 / / 4.5 ± 2.0 Hard 119 ± ± ± ± 1.4 O Donoghue P, Clay Male International 7.7 ± 1.7 / 19.5 ± 2.1 et al. (50) Hard 5.8 ± ± 2.0 / / / Grass 4.3 ± ± 1.6 Clay Female International 18.2 ± 1.6 Hard 18.1 ± 2.0 Grass 18.1 ±

5 Open : 35 % of points, Wimbledon : 19 % of points). (50) In the same way, results show that the server approached the net significantly more on a fast surface like grass at Wimbledon (40 % points for the male) than at all other tournaments. (50) This type of study has been repeated for a more recent period. Indeed, Brown and O Donoghue (48) have conducted a notational analysis of singles events at all four Grand Slam tournaments during They revealed that the difference between rally durations at the French Open (7.3 s) and Wimbledon (3.8 s) in 1997 to 1999 has decreased in 2007 (7.6 s and 5.4 s respectively). Moreover, rallies in men s singles have increased in duration at all four tournaments since There was a lower percentage of service points (aces, double faults, serve winners and return winners) in men s singles at each tournament in 2007 than reported by O Donoghue and Ingram. (50) These data reflect two evolution points in elite competitive tennis matches. Firstly, they can be explained by the introduction of new balls by the ITF to reduce the variation between different surfaces. In 2006, the ITF decided to use type 1 balls on the slowest surfaces and type 3 ball on the fastest surface. Because the type 3 ball is 6-8 % bigger than the standard type 2, it generates greater air resistance, resulting in greater air deceleration before the rebound. (59) Secondly, one may argue that players are fitter and show better technical abilities currently than during the 1990s, allowing them to reach more balls and increase the duration of rallies. (48) - Physiological Parameters Studies analyzed the effect of court surfaces on the match s technical characteristics in relation with the player s physiological responses during simulated tennis competition. (15, 41, 51) They found a relationship between the changes in match characteristics induced by court surface and physiological responses. Court surface influences tennis match characteristics that are probably responsible for the higher mean HR and [La] values measured on CL than on H, suggesting an overall higher physiological demand on that surface. (41, 51) The fact that, on H, the rallies are less long and less intense than on CL could be a factor responsible for higher [La] values on CL. Girard and Millet (15) found high correlations between the percentage of HRmax, duration of rallies and shots played consecutively on CL and H courts. HR increases when subjects hit more consecutive shots and play longer rallies. In the same way, Fernandez-Fernandez et al. (39) found a significant positive relationship between rally duration, strokes per rally, changes of direction and [La] and HR responses, with stronger correlations when the players were serving on CL. Concerning VO 2, Girard and Millet (15) reported higher mean VO 2 values on CL than on H. According to Murias et al., (51), mean % of VO 2 max was not altered by the playing surface. These results are suggestive of an increased physiological demand on CL. Fernandez-Fernandez et al. (45) have examined how the training surface (CL or carpet) affects the characteristics (ball velocity, running pressure, running volume, physiological responses) of a training session. They reported no significant difference of the court surface on any variables analyzed. Fatigue in Tennis and Effect on Performance Fatigue can be defined as an acute impairment of exercise performance, which ultimately leads to the incapacity to produce maximal force output and/or control motor function. (60) In tennis, fatigue may be related to a prolonged or high-intensity physical exertion. (60) Different reviews about fatigue in tennis have been published (40, 60) recently and we invite readers to read them. Prolonged tennis matches result in fatigue, which impairs skilled performance and, notably stroke accuracy. Fatigue from maximal tennis hitting in the Loughborough Intermittent Tennis Test resulted in a 69 % deterioration in hitting accuracy of the groundstroke and a 30 % decline in accuracy of the service. (61) Fatigue affects also serve and ground stroke velocity. (62) These reductions are probably the consequence of a protective mechanism to avoid injury by limiting the large ranges of motion, forces and torques exerted on joints. (34) Fatigue impairs the running movement efficiency and the quality of movement patterns. Indeed, Ferrauti et al. (42) evaluated the effect of the resting duration in intermittent tennis training drills on running speed. Players who had only benefited from 10-second rest between every trial ran significantly slower, and were more strained than the players having benefited from 15-second rest. Moreover, Vergauwen et al. (62) attempted to identify the fatigue effects during an on court strenuous training session by pairing players with an opponent of identical level. Decreases in sprint performance (70 m) only appeared after 2 hours of the experimental training. These results could be related to the muscular and power decrements observed during high intensity intermittent exercise. (63) Indeed, fatigue has a detrimental effect on player s muscular functioning. Tennis matches induce muscle damage as players are subjected to strenuous eccentric contractions (breaking, deceleration, flexion, stretchshortening actions). The lower body needs to perform large flexion and decelerations to prepare for and recover after groundstrokes and volleys, as well as during the follow-through and landing phase of the serve. (64) It has been reported that the material used by players had an influence on muscular fatigue. Fabre et al. (65) analyzed the influence of the type of string (monofilament polyester vs. multifilament polyurethane) on muscular fatigue of the forearm after a simulated match of 124 minutes. They reported a higher level of muscular fatigue after the match with the monofilament polyester string (-22 % of mean strength) than with the multifilament polyurethane (-2 % of mean strength). Results showed also a higher decrease of groundstroke ball speed (-10 %) with the monofilament polyester. - Hydration and Supplementation Wu et al. (66) investigated the effect of sodium supplementation on skilled tennis performance after a simulated match. RPE was significantly higher in the placebo group (15.7 ± 1.9) than in the sodium group (15.2 ± 2.8). As service and groundstroke consistency scores declined significantly for the placebo group and were maintained for the sodium group, their results suggest that sodium supplementation could prevent the decline in tennis performance after a tennis match. Indeed, it has been reported that sodium supplementation increases muscle fiber conduction velocity and may alleviate the exercise-induced impairment in the neural functions. (66) Moreover, it has been shown that caffeine supplementation attenuates the effects of fatigue and increases serve velocity. (55) and tennis success in women. (67) Tennis players began matches in a poor state of hydration. (68) It has been shown that in this case players could have progressively been increasing thermal strain and a greater risk for exertional illness as the match advances. (69) Two percent of the body fluid loss has been reported to induce decrements in sport performance. Indeed, decrease in plasma volume can induce heat stress, hyperthermia, exhaustion and muscular cramps. (38, 70) So, consuming ad libitum carbohydrate/electrolyte drink is recommended to aid in glycogen resynthesis, minimize dehydration, fluid deficits and mean core temperature responses during tennis. (68) Recommendations for Coaches As tennis players need to be exceptional movers in a linear and lateral direction for short distance, (34) specific speed and agility drills should be implemented in conditioning programs. Basic endurance should be developed for tennis players by favoring the extensive continuous training method (running, cycling, mountain biking). This training should be done in the offseason. More specific endurance training can be done prior to the competitive period. In this way, semi-specific endurance training (fartlek, high intermittent exercise) is an important extension of basic endurance training. Then, tennis specific endurance training should be used to replicate the physical demands of tennis matchplay. Moreover, it is important to prepare players properly to deal with the high-intensity situations. Reid et al. (71) have determined the physiological responses (HR, [La], RPE) of on-court drills (Star, Box, Suicide, Big X) commonly used in the endurance training of professional players (Figure 3). As these exercises (6 x 60 seconds) induce similar responses to maximum in game values, it would be interesting to use them. Competitive players are subjected to overuse injuries. As a consequence, optimal periodization plan is necessary to limit injury potential. In this way, Fernandez-Fernandez et al. (38) recommended a minimum of 8 training weeks for junior players to prepare them to overcome the competitive season. Moreover, they suggested the inclusion of competitive cycles of 3 weeks interspersed by 2 weeks of recovery and training. Because CL courts induce longer points, higher EPT, HR, and [La], training in preparation for the CL court season needs to focus on developing muscular and cardiovascular endurance. In addition to the offseason endurance training period in mid-november, professional players should participate in a second endurance training phase in preparation for the CL court season. (72) The conditioning phase should focus on tennis specific endurance training using on-court drills, such as cross rallies or baseline competitions without service and return. (73) During matches or training, it has been reported that 1.2 to 1.6 L/h hydration with water and carbohydrate is beneficial to aid in glycogen resynthesis. (74) When playing in the heat, sodium supplementation should be encouraged at a rate of 1.5 g/l in order to replace electrolytes lost. (38) Coaches should encourage players to drink more in preparation for and recovery from the matches. The American College of Sports Medicine recommended consuming between 400 and 600 ml of water two hours before exercise. (74) Hydration should begin immediately after the match and it is recommended to drink 150 % of any fluid deficit. (70) Coaches should encourage players to use water immersion, ice jackets, water spraying, cold air exposure and to make breaks when they practice tennis in hot conditions

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Caractéristiques anthropométriques et biomotrices d adolescents athlètes élites de disciplines sportives différentes. Sci Sports 1998;13: Leone M, Lariviere G, Comtois AS. Discriminant analysis of anthropometric and biomotor variables among elite adolescent female athletes in four sports. J Sports Sci 2002; 20: Caroline Martin Caroline Martin completed under and post-graduate studies in Sports Sciences in the Sports Sciences and Physical Education (2SEP) Department of the ENS Cachan. Her research interests are related to physiological and biomechanical key features of the tennis performance. She is currently completing his PhD in Biomechanics Optimization of the tennis serve in the M2S Laboratory of the Rennes 2 University. Caroline is also a physical education professor (agrégée), tennis player (ITN 1) and coach. ENS (Ecole Normale Supérieure) de Cachan, Antenne de Bretagne, Bruz, France. M2S Laboratory (Movement, Sport, Health), Rennes 2 University, Rennes. Jacques Prioux Jacques Prioux is the director of the Sports Sciences and Physical Education (2SEP) Department of the ENS Cachan. He is a sport physiologist professor at the ENS Cachan and at the M2S Laboratory of the Rennes 2 University involved in physiological research with the aim of improving sport performance. jacques.prioux@bretagne.ens-cachan.fr About the authors 18 19