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Original Research

A Comparison of the Activity Profile and Physiological Demands Between Advanced and Recreational Veteran Tennis Players

Fernandez-Fernandez, Jaime1; Sanz-Rivas, David1; Sanchez-Muñoz, Cristobal2; Pluim, Babette M3; Tiemessen, Ivo4; Mendez-Villanueva, Alberto5

Author Information
Journal of Strength and Conditioning Research: March 2009 - Volume 23 - Issue 2 - p 604-610
doi: 10.1519/JSC.0b013e318194208a
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Abstract

Introduction

Tennis is one of the most popular sports worldwide; however, relatively few studies have investigated the activity profile and physical demands during play (2,4,6,28,31). A better understanding of the physiological demands and movement profile of tennis is important, to develop optimal practice drills and to give sound training recommendations. In addition, knowledge of the intensity, volume of work involved, and estimation of energy expenditure in playing tennis enables a comparison to be made between tennis and other forms of physical activity from a health perspective, which may lead professional tennis organizations (e.g., International Tennis federation [ITF]) to espouse health benefits of tennis participation on the basis of experimental interventions (13,24).

The American College of Sports Medicine (ACSM), to promote and maintain health in healthy adults, recommends engaging in moderate-intensity aerobic physical activity (i.e., intensities of 40-60% of o2max; 60-75% of maximum heart rate [HRmax]) for a minimum of 30 min·d−1, 5 d·wk−1 or vigorous-intensity aerobic activity (i.e., 60% of o2max; 75% HRmax) for a minimum of 20 min·d−1, 3 d·wk−1 (1,13). Previous studies on the physiological demands of tennis have focused on activity profile (2,8,15,19,20,23,26,28), heart rate (HR) (2,8,15,20), blood lactate concentrations (2,4,8,24,28,30), and o2 (9,28,29) during tennis play. Mean HR during singles play ranged from 140 to 180 bpm, equating to 70-90% HRmax, and mean o2 during play ranged from 23 to 40 ml·kg−1·min−1, reflecting 50-80% o2max (8,15,16). Thus, exercise intensity during singles tennis play seems high enough to categorize it as a moderate- to vigorous-intensity sport. However, most of the previous studies investigated young, regular tennis practitioners exclusively (2,4,6,8,19,20,23,26,28), who usually carry out intensive tennis practice with the goal of mastering sport-specific skills. It is likely that many of the adults who can choose tennis as the preferred physical activity to promote and maintain health have lower-skill levels than their younger and more dedicated counterparts. As tennis has an important technical component, poor sport-specific skills can prevent less skilled practitioners from deriving sufficient health benefits out of tennis match play (18). Therefore, the aim of this study was to examine the physiological parameters (HR, o2), energy expenditure, and activity profiles of advanced (high skill level) and recreational (low to average skill level) tennis players during match play. In addition, this study investigated whether the physical demands of tennis meet the criteria laid down by the ACSM for improving and maintaining cardiovascular fitness in healthy adults (1,13).

Methods

Experimental Approach to the Problem

To determine whether tennis match play can provide an adequate intensity stimulus to improve cardiovascular capacity, we recruited 20 physically active recreational (n = 10) and advanced (n = 10) men's tennis players. The variables analyzed were used to describe various physical and physiological responses of veteran (i.e., ≥40 years) tennis players when playing an hour of tennis.

Subjects

The study population consisted of 20 men's tennis players, divided into 2 groups according to standards of play based on the International Tennis Number (ITN) test, which represents a player's general level of play (14). The subjects in the first group (group A) were advanced tennis players (ITN levels 3-5, which represent top division/middle division county players and top club team players). The subjects in the second group (group B) were recreational tennis players (ITN levels 7-9, which represent lower club team players and players competing regularly in singles and/or doubles) (14). Each subject gave written informed consent to participate in the study, which was approved by the university institutional review board for studies involving human subjects. A medical examination was required of all subjects before participation in the study.

Study Design

Four experimental sessions were conducted during a 30-day testing period: a) the ITN on-court assessment, b) a laboratory incremental treadmill test to identify HRmax and o2max, c) an hour of simulated tennis match play with video analysis to record the activity profile and HR monitoring, and d) 30 minutes of tennis match play using a portable gas analyzer to determine o2 and energy expenditure during play.

Laboratory Treadmill Test

On arrival at the laboratory, anthropometric measurements including height and weight were determined, and skinfold measurements were taken. Percent body fat was determined from the sum of 7 skinfolds (34) using a Lange skinfold caliper (Takei Grip-A, Takei Scientific Instruments, Japan). The complete set of skinfold measures was taken 3 times, and median values were used for analytical purposes. All subjects performed a maximal exercise test on a motorized treadmill (RAM 550S) to determine HRmax and o2max. The treadmill test consisted of an initial workload of 8 km·h−1 with an increase of 2 km·h−1 every 3 minutes at a constant grade of 3%, with a 1-minute break between each stage, until exhaustion (31). Respiratory gas exchange measures were taken using a breath-by-breath portable gas analyzer (K4b2, Cosmed, Rome, Italy) and recorded at 5-second intervals. Heart rate was recorded by the K4b2 with athletes wearing a chest belt (Suunto t6). The volume calibration of the system for gas analysis was conducted before each test day, and the gas calibration was performed before each test using instructions provided by the manufacturer. The highest 30-second mean o2 and HR values measured during the test were used as maximum reference values (HRmax and o2max). Criteria for determination of o2max included plateau in o2 despite an increase in workload, respiratory exchange ratio >1.1, and HR > 90% of predicted HRmax (12).

On-Court Testing

International Tennis Number Test

The ITN On Court Assessment is an objective on-court assessment based on a set number of tennis-specific tasks (i.e., ball control, accuracy, power), developed as a tool to enable players to benchmark their tennis level against themselves and others around the world (14). The ITN On Court Assessment was performed following the instructions provided by the International Tennis Federation (www.internationaltennisnumber.com). A ball machine (Tennis Tower, Professional Model, Sports Tutor Inc.) was used to feed balls to the players who were tested. A radar machine (Speed Chek, Personal Sports Radar, Tribar Industries Inc.) was used to measure ball velocities during the ITN tests. Previous research has demonstrated the accuracy of the ball feed from the tennis ball machine (5).

Tennis Match Play

Each player (groups A and B) played a singles match of 1 hour (in pairs), resulting in 10 matches (5 matches for players of group A and 5 matches for players of group B). All players were equipped with a Suunto t6 chest-belt telemetry monitor to record HR. Before each match, subjects performed a standardized warm-up for 5 minutes, including ground strokes (players were asked to play the balls to the center of the court), volleys plus overhead plays (one player on the baseline, the other playing volleys), and services. All matches were conducted on an outdoor clay court and were played according to the rules of the ITF. A set of 4 new balls (Slazenger, London, UK) was used for each test.

Activity Profile

Each player was individually videotaped for the entire duration of the match. A match protocol developed by Smekal et al. (31), which has been shown to be reliable (20), was used to monitor and record the duration of each game and each rally, the duration of the rest intervals between games and changeover breaks, and the number of shots per rally. From these data, the following variables were calculated for each game: 1) the duration of rallies (DR in seconds), 2) the rest times (RT in seconds), 3) the work:rest ratio (W:R; the ratio of duration of rallies to rest times), 4) effective playing time (EPT; expressed as a percentage of the total time of play in a game), and 5) strokes per rally (SR). The EPT was determined by dividing the entire playing time of a game (from the beginning of the first rally until the end of the last rally) by the real playing time (sum of the single duration of rallies) performed in a specific game.

Distance Covered and Running Speed

The distance covered (m) during the entire match by each individual player and the time spent (seconds) in various speed categories were measured using the software Winanalyze V1.4 (Mikromak, Berlin, Germany) (6,7,24,25). This automated software tracks a visual marker frame-by-frame in the video files taken during the matches. The visual marker was set afterward and was placed on the right hip of each tennis player. This position was chosen because during the analysis it became apparent that the visual marker kept best track on the right hip compared with all other body parts. In case the visual marker lost track, the marker position was reset manually by one experimenter. Final marker positions were analyzed using Matlab 6.5 (The Mathworks, Natick, Mass) to calculate distance covered and running speed (by differentiation). Five different speed categories were defined according to a study by Burgess et al. (3): 0-7, 7-12, 12-18, 18-24, and >24 km·h−1. Test-retest reliability of the method was assessed within 1 tennis match.

Physiological Demands

o2 Measurement During Match Play

A week after the singles match play, 13 players (group A, n = 7, group B, n = 6) played singles for 30 minutes, using a Cosmed K4 portable gas analyzer to measure o2 and to estimate the quantity of energy expended during tennis play. Subjects' o2 and HR were determined at 5-second intervals. Energy expenditure was calculated from the o2 values using 5 kcal·L−1 O2 as the caloric equivalent. Values were averaged for the 30 minutes of each tennis match to obtain the total energy expenditure (31).

Statistical Analyses

Mean and SD were calculated for all specified outcome measures in groups A and B. Differences in rally duration, rest times, and strokes per rally were evaluated using 2-factor analysis of variance. To test the test-retest reliability of the Winanalyze system, we assessed the intraclass correlation coefficient for single measures. An intraclass coefficient of 0.80 or higher was considered reliable (27). The differences between the group mean values of the variables measured with the treadmill test and the on-court assessments were tested by unpaired Student t-tests. Data were checked for normality (Shapiro-Wilk test), and, in cases of nonnormality, nonparametric Wilcoxon signed rank tests were performed. Values of p ≤ 0.05 were considered statistically significant. Data were analyzed using SPSS statistical software (version 13.0; SPSS Inc., Chicago, Ill).

Results

Subjects' characteristics and the results of the laboratory treadmill test are shown in Table 1. Both groups were comparable with regard to age, height, weight, and fat percentage. In addition, there were no statistically significant differences in the mean o2max (p = 0.64) and HRmax (p = 0.25) values that advanced and recreational players achieved during the treadmill test.

T1-32
Table 1:
Subject characteristics.

Activity Profile

The variables describing the characteristics of the matches for both groups are shown in Table 2. The results show that differences between the advanced and recreational players in DR (p = 0.98), RT (p = 0.94), SR (p = 1.00), and EPT (p = 0.80) were not statistically significant. Figure 1 shows the mean distribution of work (i.e., DR) and recovery (i.e., RT) periods at given time intervals during the 166 games analyzed. For both groups, most of the rallies (about 55%) were performed at time intervals between 1 and 6 seconds (p < 0.05); when combined with rallies between 6 and 9 seconds (about 20%), this represents 70-80% of the total points performed during the matches in groups A and B. More than 70% of the RT was between 9 and 18 seconds. More than 60% of all rallies demanded players to execute between 1 and 2 strokes (p < 0.05). When combined with rallies demanding 3-4 strokes, this accounted for more than 90% of the total rallies.

T2-32
Table 2:
Movement pattern and associated physiological responses during 1 hour of tennis match play.
F1-32
Figure 1:
Mean percentage of playing time and rest intervals during an hour of simulated match play. Black and white bars represent the duration of rallies (DR) and rest time (RT), respectively, for group A. Dotted and stripped bars represent the DR and RT, respectively, for group B.

Distance Covered

The reliability of the Winanalyze system for measuring the distance covered during play was high. The intraclass coefficient for single measures was 0.98, with a lower bound of 0.57. The advanced players covered significantly more meters than the recreational players during their 1 hour of tennis match play (3568.8 ± 532.2 vs. 3173.8 ± 226 m, p = 0.04, Table 2). Running speed between the advanced and recreational players revealed differences in the average speed while playing (3.8 ± 0.3 vs. 5.0 ± 0.3 km·h−1, p < 0.01) and in the total time spent in the different speed categories (Table 3). Advanced players spent more time in the lowest speed category (0-7 km·h−1) than recreational players and less time in all higher-speed categories.

T3-32
Table 3:
Speed analysis: the average speed and the amount of time (s) the advanced and recreational players spent in each speed category during 1 hour of tennis match play.

Physiological Demands During On-Court Assessment

The physiological responses of the on-court assessment (i.e., 1 hour of tennis match play and 30 minutes of play wearing the portable gas analyzer), which were calculated as mean values for all games performed by players, are displayed in Tables 2, 3 and 4, respectively. During 1 hour of tennis match play, differences in HR (p = 0.61) and %HR (p = 0.52) were not significantly different between advanced and recreational players. The results also show no significant differences between the advanced and recreational players in HR (p = 0.39), HRmax (p = 0.79) and o2 (p = 0.54) percentage of laboratory o2max (%o2max; (p = 0.55), percentage of laboratory HRmax (%HRmax) (p = 0.90), or energy expenditure (p = 0.18) during the 30 minutes of play wearing the portable gas analyzer.

T4-32
Table 4:
Physiological responses during 30 minutes of tennis match play.

Discussion

The purpose of this study was to provide a physiological basis on which to recommend regular tennis play as a healthy exercise modality in middle-age individuals. Accordingly, this study investigated movement patterns, physiological responses, and energy costs during tennis match play. The main finding of the present study was that singles tennis match play can satisfy the ACSM recommendations for quantity and quality of exercise for the development and maintenance of cardiovascular fitness in healthy adults (1,13) regardless of the playing ability of the participants (i.e., recreational vs. advanced players).

Time motion analysis is important to quantify the physiological responses and requirements of a particular sport (28,32). The present motion analysis characteristics (see Table 2) showed no significant differences between groups, with average values (DR ≈ 7 seconds, RT ≈ 14 seconds, SR ≈ 2 seconds) in agreement with previous studies (8,16,17). Interestingly, playing level (advanced vs. recreational) did not influence activity patterns during tennis match play (see Table 2). We have previously shown that physiological responses during tennis match play are influenced by movement patterns (9,20). Thus, as can be expected, none of the measured physiological responses were significantly affected by the playing levels of the subjects in the present study.

During 1-hour matches of tennis, players covered distances of approximately 3-3.5 km at different running speeds. Although the emphasis of running speed is in the lowest speed category (i.e., walking 75-80% of the total time), players still need to accelerate for 10-15 minutes to reach the necessary running speeds to get to the ball in time. In this study, advanced players covered greater distances than recreational players. This can be explained by the higher skill level of the advanced players, enabling them to hit sharper angles and resulting in full use of the court and longer running distances. However, speed analysis also revealed that advanced players had lower average speeds and spent more time in the lowest speed category (walking) during the 1 hour of tennis match play compared with recreational players, demonstrating a more continuous movement pattern on court. These findings cannot be explained by longer rally durations of the advanced players because rally duration and EPT were not significantly different between the 2 groups. The most likely explanation is the better anticipation of the advanced players. Although the advanced players have to cover more meters during play (because of the wider angles) compared with recreational players, by anticipating well, advanced players could use lower speeds to move to the ball.

The values found for distance covered in this study were much higher than those reported by Murias et al. (21), who reported 1447 ± 143 m for nationally ranked players on a clay court during 90 minutes of play. The distances covered by the hard court players in that study were even lower (1199 ± 168 m), which was to be expected, because rallies on hard courts tend to be shorter than rallies on clay courts. There are several explanation for this difference. The main reason may be that Murias et al. (21) only analyzed distances when the ball was in play, whereas in the current study the walking distances for picking up the ball and changing ends were included as well. Furthermore, Murias et al. (21) used a different, less accurate methodology than the one used in the current study: they drew a grid on a 21-inch flatscreen television and calculated a proportionality model. They did not describe the reliability of this method.

A subject's o2max value is an interesting variable from which to glean information about the intensity of play during a match, and it also may serve as a reference from which to provide practical information about suitable conditioning for different players (8). The mean o2max of players involved in our study was 44.9 and 44.1 ml·kg−1·min−1 for advanced and recreational players, respectively. Normative o2max values for sedentary adults range between 30 and 40 ml·kg−1·min−1, and the mean o2max reported for regular tennis players ranged from 35 to 65 ml·kg−1·min−1, depending on age, gender, and training level (9,16,17). According to the ACSM, the minimal training intensity threshold for cardiovascular exercise is approximately 50% o2max. Studies using portable gas analyzers have reported o2 levels during tennis play ranging from 23 to 29 ml·kg−1·min−1 (2,8,23,31). This corresponds to about 50% o2max, with values ranging from 46 to 56% o2max (8,16,17). In our study, both groups achieved the recommended stimulus for effective initiation of cardiovascular adaptations and conditioning as expressed by the percentage of o2max (50-85%), with exercise intensities ranging from 53 to 55% o2max, which is slightly above the minimum intensity recommended by the ACSM (1,13). Moreover, the results show no significant differences between groups, suggesting that a lower technical level (i.e., in the recreational group) did not prevent these players from obtaining a positive cardiovascular stimulus.

The measurement of match HR provides a useful index of overall physiological strain during play. The mean HR in trained players ages 20-30 years ranges from 140 to 160 and from 95 to 165 bpm during singles and doubles tennis competitions, respectively, rising to 190-200 bpm during long and fast rallies, reflecting phases of high activity (8,16,17). These mean values represent approximately 70-90% HRmax. The average HR values in this study were close to 150 bpm for advanced and recreational players, with no significant differences between groups, which represented approximately 80% HRmax. These values are well above the threshold (60% HRmax) for the cardiovascular training effect and are, therefore, within the recommended cardiovascular training zone for the entire hour of tennis play regardless of experience and level. Thus, on the basis of exercise HR responses, both groups achieved the recommended stimulus for effective initiation of cardiovascular adaptations and conditioning as prescribed by the ACSM (60-90% HRmax) (1,13).

The ACSM guidelines recommend that an exercise routine should elicit an expenditure of 300 kcal and be performed for a minimum of 3 d·wk−1 for total body mass and fat weight loss (1,13). An expenditure of 200 kcal is also recommended if the frequency is more than 3 times per week. Data in this study indicate a moderate caloric expenditure for this mode of exercise (∼265 and ∼280 kcal·min−1 for 30 minutes of match play in advanced and recreational players, respectively), which supports the notion that tennis is an exercise modality that can be appropriately prescribed for enhancing weight control and fat weight loss. On the basis of the responses of the subjects to an hour of tennis match play, it would require approximately 30 minutes to expend approximately 260-280 kcal (i.e., between 8 and 10 kcal·min−1). These values are similar to the results obtained by other authors (10,11,23). Thus, during 1 hour of singles tennis play, a recreational tennis player would be expected to burn approximately 500-600 kcal, which would represent an extra energy expenditure of 1500-3000 kcal by playing tennis 3 times a week, contributing to long-term weight management (22). This has important ramifications because weight loss and fat reduction are often reasons that motivate people to exercise (33). The Cardio-Tennis program promoted by the United States Tennis Association seems to be the latest trend and activity widely used by the adult population in the United States as a fitness activity. Therefore, tennis match play would be a good way to achieve the aforementioned goals (i.e., weight loss and fat reduction), but more research is needed to support this idea.

In conclusion, we reported physiological (i.e., cardiorespiratory responses and energy cost) and movement pattern responses during tennis match play and compared these responses in 2 groups of veteran tennis practitioners with different playing levels (i.e., recreational vs. advanced players). No significant differences between the groups were found in any of the parameters investigated. The results also suggest that regular tennis play (i.e., 2-3 times per week) can satisfy the ACSM recommendations for quantity and quality of exercise for the development and maintenance of cardiovascular fitness in healthy adults, regardless of the playing ability of the participants (i.e., recreational vs. advanced players).

Practical Applications

The results of the present study suggest that individuals playing tennis on a regular basis (2-3 times a week) can work at a sufficient intensity to meet the ACSM's recommendations for enhancing aerobic fitness and promoting total body mass and fat weight loss (1,13) regardless of their playing ability (i.e., recreational vs. advanced players). Therefore, even players with low to average skill capacities could obtain positive health benefits from regular tennis play. Moreover, the ACSM suggests that adults also will benefit from performing activities that maintain or increase muscular strength and endurance for a minimum of 2 d·wk−1 (13). Therefore, tennis, in combination with supervised strength workouts, would therefore be an ideal sport to improve physical activity levels of the general population, and it may have positive benefits on lifelong health.

Acknowledgments

This work was supported by a research grant from the International Tennis Federation (ITF). The authors would like to thank the Royal Spanish Tennis Federation (RFET) and the FIATC insurance company (Barcelona, Spain), especially Arnau Florit, Drs Angel Cotorro, and Angeles Estruch for their technical assistance. Moreover, the authors thank the members of Real Club de Tenis Barcelona 1899 (Barcelona, Spain), players and especially Ventura Durall for giving their time and effort to participate in this study.

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Keywords:

energy expenditure; fitness; heart rate; racquet sports; oxygen uptake

© 2009 National Strength and Conditioning Association