There is an ongoing debate about the aerobic nature of tennis. It is obvious the sport of tennis contains both aerobic and anaerobic components. This is sometimes misinterpreted by the coach or athlete as meaning the tennis player should run long, slow distances for training.
Previous research has suggested that tennis is an aerobic sport due to the length of matches which can last from 2-5 hours (9) with relatively moderate mean heart rate values found during play (1). Because of this, many coaches have recommended long distance runs of thirty minutes or more or long interval runs of 1-2 minutes. This training is often performed 3-5 times per week. Using heart rate ranges as a measure of energy system contribution can be misleading. Heart rate ranges during a match are rather wide due to the continual stop/start movements involved in tennis; therefore, mean measures do not accurately represent the explosive nature of the sport. It would be remiss to suggest that tennis is predominantly an aerobic sport. It might be better to classify the sport as an anaerobic-predominant activity requiring high levels of aerobic conditioning to avoid fatigue and aid in recovery between points.
Cardiorespiratory fitness is the ability of the heart and lungs to transport oxygen to working muscles to aid in energy production. VO2max is often used as an indicator of cardiorespiratory fitness. VO2max is defined as the maximum amount of oxygen an athlete can uptake, or utilize, to make ATP. There is a linear relationship between VO2 and heart rate. As heart rate increases with exercise, VO2 will also increase at the same rate. Because of this linear relationship, the volume of oxygen being utilized to produce energy at any point in time may be estimated using heart rate at a steady work rate. With training, the efficiency of ATP production improves, and movement economy (running economy in runners) improves so the athlete is more efficient at using the ATP produced. In the sport of tennis, the work rate is not steady, and therefore heart rates are continually going up and down.
If we were able to get an average heart rate throughout a point, or throughout a match, we would find that the tennis player with higher cardiorespiratory fitness would likely have the lower average heart rate. From this average heart rate, we could estimate the average oxygen consumption during the point or during the match. While this would not be as accurate as during a “steady state” activity, the general idea is the same. Improving cardiorespiratory fitness to a point can positively influence the ability of the athlete to perform physical work. In tennis, the methods used to produce increases in cardiorespiratory fitness become very important. As we will discuss below, long slow distance training is counterproductive to training the tennis player for the short explosive bursts of activity needed for tennis.
Training for aerobic endurance enhancement will result in a number of cardiovascular adaptations. The adaptations that occur are specific to the method of training.
Traditional long, slow endurance training will produce increases in VO2max. Increases in VO2max are attributed to increases in cardiac output as well as an improved extraction capability within skeletal muscle. During exercise, VO2 is increased above resting levels to meet the higher energy demands of the exercising muscle. As intensity of exercise increases, VO2 will also increase.
As exercise intensity increases, heart rate also increases in a linear fashion until it reaches a plateau. Endurance training will cause a decrease in resting heart rate and a decrease in heart rate at any given submaximal VO2 (11). The decrease in heart rate during submaximal exercise is a result of both improved cardiac output through increases in stroke volume (amount of blood pumped per beat) and more efficient exercise movement. Maximal heart rate is unaffected by endurance training. By improving movement economy, the tennis player can perform more work per volume of oxygen consumed. Because of the adaptations to the heart (increased stroke volume, decreased heart rate at a given work load) and the adaptations related to improved movement economy, the tennis player will be able to work at higher workloads for longer periods of time.
Stroke volume is the amount of blood ejected from the left ventricle in one heart beat. During exercise, stroke volume increases as the intensity of exercise increases. Resting stroke volume and maximal stroke volume are improved by endurance training because the increased ventricular filling, or preload, seen during endurance exercise enlarges the ventricular chamber. The increase of the preload is believed to be due to the expanded plasma volume seen in endurance training (3).
Cardiac output is the amount of blood pumped from the heart in one minute. It is a function of heart rate and stroke volume. At rest cardiac output is approximately 5 L, but during maximal endurance exercise cardiac output may increase to 20 L, and may reach 40 L in endurance trained male athletes (7). Since maximal heart rate is unaffected by training, the increase in cardiac output is primarily a result of improved stroke volume. With all things being equal, the tennis player with a greater cardiac output will be able to perform at a higher level for a longer period of time. Tennis players should consider the most effective training methods for improving cardiac output and stroke volume, but not those that have a negative effect on speed and power output.
In general, the respiratory system does not limit the amount of oxygen provided to the exercising muscles. Respiratory capacity does not appear to be significantly affected by endurance training. Therefore, breathing heavier and trying to get more oxygen in, will not improve tennis performance, since the amount of oxygen available is not a limiting factor.
Hypervolemia is an increase in blood volume. Endurance training has been shown to cause hypervolemia, which occurs in the first 2–4 weeks of training. Hypervolemia is thought to be the result of plasma volume expansion and an increase in the number of red blood cells (13).
While aerobic fitness is necessary for tennis, the amount of traditional long, slow aerobic exercise that is necessary is not clear. Tennis requires both aerobic and anaerobic metabolic pathways for a continuous supply of energy throughout the match. Anaerobic pathways are used to supply energy during points and allow for the quick explosive movements required. Aerobic pathways are used to supply energy between points so that the player can recover and perform again in 25 seconds. The efficiency of both of these energy systems is necessary for optimal tennis performance.
According to the principle of specificity, training should be as specific to the sport as possible in order to get maximum results. Watching a tennis match will demonstrate that tennis requires repeated quick explosive movements followed by a rest period. While long distance runs and long intervals will improve aerobic capabilities, it is not specific to the physiological demands of the sport of tennis. Using short interval sprints which match the work/rest intervals and the movement patterns of tennis is a more sport specific way to aerobically train tennis players. This method of training will still require the aerobic system to be used during the recovery periods and will use aerobic metabolism in the same manner it is used during actual tennis play.
Analyzing the length of the points and rest periods during matches yields relevant work/rest intervals that can be used for training. Several studies have examined the work/rest intervals in tennis matches. For high level play, work/rest ratios have been found to range from 1:2 to 1:5 (9). Total amount of match play has been shown to be 20 to 30 percent of the total match time (1, 8).
The length of points can vary greatly depending on factors such as surface, playing style, and level of play. A review of studies examining the length of points in tennis matches found the average point length ranged from 3 to 15 seconds depending on the surface (9). The average point length in all of these reviewed studies was 8 seconds.
This study also found a downward trend in the average point length in the last 20 years (9). One study which compared the 1988 men’s US Open final (4) to the 2003 men’s US Open final found that the average point length decreased by over 50% in that 15 year period. This should come as no surprise as racquet technology, an increase in resistance training, and increasing athleticism in tennis players has increased the power in tennis dramatically. This study also found that the time between points also decreased by approximately 50%. Even though the length of points has decreased, the actual work to rest ratios did not change significantly in the last 15 years. Additionally, 90% of the points were less than ten seconds (10).
Style of play has also been shown to affect the length of points. Attacking players play shorter points than players who prefer to play from the baseline (2). A player’s style of play should be taken into consideration when a designing conditioning program. Strength and conditioning coaches should perform a work/rest analysis for each player in order to design individualized conditioning programs. This evaluation should include multiple analyses using opponents with various styles and on different surfaces.
Based on available information, interval training for elite tennis players should include a majority of the time spent in work intervals of 3-15 seconds. Rest periods should also match the rest intervals seen in match play. There should be two to five seconds of rest for every second of work, making the ratios 1:2 to 1:5 (10). The work and rest periods can be adjusted within these ranges according to the individual player’s style and the competitive surface being utilized. It is also recommended that following a series of 10-15 repetitions of intervals that a longer rest period of 1-2 minutes be given to simulate the rest periods during changeovers.
Heart rate can be used to measure intensity during practice or match play. During tennis matches heart rate has been shown to increase as the match progresses, with a decrease during the changeovers (2). Heart rates were measured on a group of collegiate tennis players during 85 minutes of match play, and the mean heart rate was found to be 144.6 beats/minute, which is significantly higher than prematch heart rates (1). There is a wide range of heart rates found during a match due to the constant changing from work to rest and the variability of the length of the work period. It should be noted that the heart rate profile for a tennis match is much more similar to interval sprints than long distance running. This is further evidence for using short interval sprints instead of long distance running.
A recent review of VO2max values in competitive high-level tennis players found that VO2max results ranged from 44 to 69 ml/kg/min (9) with the vast majority of these tennis players having VO2max values above 50 ml/kg/min. These values would classify tennis players as being highly aerobically trained. Based on this information it is recommended that high level competitive tennis players have VO2max values higher than 50 ml/kg/min in order to train and compete at the desired level of play.
VO2 increases as the match progresses with a decrease during the rest periods while changing ends (2). Aggressive attacking players had lower VO2 values during play than baseline players (2). It can therefore be assumed that baseliners need a higher level of aerobic fitness than attacking players. Consequently, baseliners should perform slightly longer intervals over a longer time period than attacking players.
Although decreases in both technical and tactical performance occur when blood lactate concentrations exceed 7-8 mmol·L-1 (12), research has shown that blood lactate levels remain relatively low during match play (1) because regular rest periods between points and games allows for sufficient recovery. The lack of accumulation of blood lactate indicates that the alactic anaerobic energy system (ATP-PC) provides a majority of ATP production during the match. The aerobic energy system is active during recovery to replace the ATP used during the previous point.
While match play does not typically produce high blood lactate, the intensity and duration of some training sessions may produce high enough levels of lactate to decrease performance during drills. Many tennis players train at a much higher practice intensity and duration than what occurs during actual match play (5). Tennis players and coaches should take into account potential lactate levels when designing drills. If technical development is the goal, it is important for the athlete to be fresh with low levels of lactate so that performance is not negatively affected. If the goal of the training session is to improve conditioning, specificity of training would suggest that a training program for tennis players should progress toward sport-specific work/rest and intensity levels as the competitive season approaches.
Cardiorespiratory training may have negative effects on other aspects of training. It is obvious that speed and power are critical to success in tennis. There is some evidence that performing aerobic training concurrently with strength training is detrimental to strength production (6). Because of the close relationship between strength and power, it is possible this will cause a decrease in power output as well. Aerobic training may cause adaptations to muscle fibers that may decrease their ability to produce force. Additionally, the slow rhythmic contractions performed in aerobic training may cause an adaptation in the nervous system which could interfere with speed and quickness.
Continuous long distance running may make the athlete slower or make it difficult to gain muscle mass if this is a desired goal of training. Excessive amounts of aerobic training could also lead to overtraining and injury. Shin splints are a common result of overtraining through long distance running. Interval training can provide the tennis specific endurance required without the potential negative effects of traditional aerobic training. By using the appropriate work/rest intervals, interval training can more closely mimic the metabolic requirements of the sport.
While traditional long slow distance aerobic training may not be appropriate in general for tennis players, there are certain athletes who might benefit from periods of traditional aerobic training. This would include athletes who lack moderate fitness levels or are over the desired playing weight. When possible this training should be done in the offseason so that more sport specific training can be done prior to tournaments.
There are several differences between long distance endurance training and short interval sprint training. Short interval training has a heart rate profile which is specific to tennis while endurance training does not. Short interval training also uses neural patterns similar to tennis play because of the rapid contractions required while long distance endurance training does not. Interval training can be performed on a court with multiple changes of directions and footwork patterns in each sprint while long distance training cannot. Both methods of training will improve aerobic fitness, but because of its specificity to tennis in each of these areas, short interval training is recommended over long distance endurance training for tennis players for a majority of the training cycle (Figure 9.1).
Figure 9.1: Heart rate during tennis and traditional endurance exercise.
Cardiorespiratory fitness is important for tennis players as can be seen by their high VO2 values and the need for aerobic recovery between points. The training method used for cardiorespiratory fitness is important. For variety, offseason aerobic training can include longer distance runs. As the season approaches, training should move in the direction of short sport-specific intervals. Short intervals which match the demands of tennis should be used during the pre-competitive and competitive periods because of their specificity to the game and possibility that traditional aerobic training may decrease power outputs. The following chapter will provide sample conditioning drills which can be performed in tennis specific intervals for optimal carryover to the court.
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