The purpose of this article is to examine the testing methods and protocols for tennis specific speed and agility. The combination of speed, agility, and reactive agility are considered important attributes for optimal tennis performance (8,16). A differential evaluation of each of the components of speed and agility should help to identify the important information to help direct training priorities and exercise prescription. Follow-up testing provides an indication of training progress or effectiveness, helping the strength and conditioning coach to reflect on the training methods used and therefore helping to further enhance exercise prescription and program quality.
It is important that strength and conditioning professionals understand the definitions of speed and acceleration and translate them to the context of tennis. Speed has been defined as the rate of change of distance with respect to time, whereas acceleration is the rate of change in speed with respect to time (1). The analysis of tennis has been limited by the difficulty with readily measuring the whole body speed and acceleration of players. The existing literature includes speed and acceleration findings based on Global Positioning System (GPS) that has an inadequate measurement frequency (1 Hz or 1 sample per second) (15) to accurately reflect the movements performed. Because most movements are approximately 2.5 m (10), maximal speed cannot be achieved and is unlikely to be a limiting factor. However, the current research has failed to determine the magnitude required to be successful at the international level.
The definition of agility has been a topic of significant debate in the scientific literature. The definition most commonly referred to is “the ability to change direction rapidly” (13). However, other authors have developed the definition further to include the important elements of perceptual motor and decision-making abilities including visual scanning, anticipation, pattern recognition, and knowledge of situations (6,17). More recently, this has been summarized with a new definition including the critical element of “reacting to a stimulus” (20).
One of the possible reasons for the debate on the definition of agility is the multifactorial nature of the skills required to demonstrate good agility. The ability to rapidly change direction in a predetermined pattern is one of these components, and most traditional methods for testing the agility have included tests that are designed to test just this component (e.g., 505 Agility Test, (7)). This approach fails to recognize the open nature of the agility requirement during tennis. It is thus the aim of this paper to evaluate the key components of speed, acceleration, change of direction (COD) speed, and planned and reactive agility.
SPEED AND ACCELERATION
Straight line sprint speed over distances of 5 and 10 meters provides useful information about whole body acceleration from a standing start (9). Players should start with feet parallel in a ready position, as they would do on the tennis court. The first step should not be standardized through specific instructions (split step, backward step, or forward step), and instead, the player should be instructed to perform his/her normal movement and the test administrator should observe the start and note whether a split step, backward step or forward step was used. Because of the short distances involved, it is essential that electronic timing gates are used. The poor reliability of handheld timing with a stopwatch (typical error of measurement = 10%) (12) means that typical training adaptations over a period of weeks or months (approximately 5%) cannot be evaluated (12).
Most traditional tests of agility have essentially assessed COD speed. The most fundamental changes of direction required on the tennis court are to a wide forehand or backhand with recovery to middle of the court and forward toward the net and recovering backward to an overhead position or retracting back to the baseline (2). COD speed provides vital information about the players' ability to combine appropriate acceleration, deceleration, and footwork. Again, because of the short distances (80% of all strokes are within 2.5-4.5 m) (10), it is essential that electronic timing gates are used to time each of the tests. Filming of the tests can help the strength and conditioning coach and the tennis coach to qualitatively examine the footwork and positioning used to change direction (14). Specific tennis movement tests to the forehand and backhand and forward and backward movements have been published elsewhere (14).
PLANNED VERSUS REACTIVE AGILITY
To assess the reactive component of agility, the authors have designed 2 tests that help to evaluate the difference between a tennis player's ability to perform repeated sport-specific COD in a planned and an unplanned or reactive condition. The Figure illustrates the test setup on an indoor court using a commercially available electronic timing system with programmable light stimuli (Smart Speed; Fusion Sport Pty, Ltd, Brisbane, Queensland, Australia). Tennis players rarely run more than 3 m to a ball (10,5), and thus, the 3 light gates were placed 3 m from the center of the baseline. The middle gate is placed directly along the centerline of the court, and the gates to the left and right are placed along the lines from the center of the baseline to the intersection of the service line and the singles side line on the left and right. Each gate is 1 m wide, and the tripods are placed along a line perpendicular to the line used to measure the 3-m distance from the baseline.
The players are instructed to perform 3 efforts of the planned and then the reactive agility conditions. Each effort requires the player to start behind the yellow contact mat, which is placed behind the baseline. The contact mat acts as a switch turning on the light on the selected gate. The player is asked to initiate the effort by split stepping on to the mat and to move as quickly as possible to the gate in which the light appears. On reaching the gate, the player is instructed to step over a line marker placed 30 cm beyond the gate. This helps to ensure that the trunk is consistently used to break the light gate. The player then returns to the contact mat and repeats this for a total of 3 gates.
Players are instructed to move as they would during a tennis match, as the testers did not wish to change existing natural movement patterns of the players. The total time taken to complete the movement to 3 gates is used for evaluation. The planned condition is programmed, so that the gates are illuminated in order from right to left (right, center, left; the player is informed of this in advance).
In contrast, the reactive condition is a sequence of 3 gates, which are randomized and may include returning to the same gate 2 or even 3 times. The best of the 3 times for each condition is taken, and the difference between planned and reactive conditions is used as a measure of reaction time. To ensure optimal times for each player, there should be no less than 60-second recovery between trials as previously suggested by other authors (11).
The tests outlined above provide a total of 9 data points. One way of summarizing and ranking these results is to use standardized scores (Z score). The quantity Z represents the distance between the raw score and the population mean in units of the SD ([mean − raw score]/SD). The Table includes sample results and sample Z scores from a player. In all the tests used here, a negative Z score indicates a performance that is poorer than the mean, and conversely, a positive Z score identifies those performed better than the population mean (the population mean should be specific to the age and gender of the player(s) being evaluated). This allows the identification of the individual player's relative strengths and weaknesses. Therefore, the authors would encourage the collection of age- and gender-specific data within a training facility including factors such as surface and equipment ensuring consistency for better test-retest reliability. The case example in the Table indicates that this player has a relatively good reaction time and reactive agility but may be limited by their maximal speed as may be required in defensive situations on the court compared with other players of the same age and gender.
OTHER PRACTICAL CONSIDERATIONS
The case example presented here includes a number of above-average results with the lowest Z scores in tests considered to have a lower relative importance to the tennis performance. The time constraints experienced in tennis (10) would intuitively imply that reactive abilities combined with acceleration and COD speed would be of greatest performance benefit. However, the current scientific literature does not include studies that permit the determination of the exact relative weighting of these tests in terms of performance impact.
From a training perspective, single-leg reactive strength has been shown to be important. Those individuals who possessed significantly greater reactive strength in the right leg produced significantly better COD speed to the left side (19,4). However, COD speed in tennis-specific movements may be different as the COD is most often achieved by a crossover step rather than a cutting movement that is used in many field sports. A recent review of training studies found that the training protocols reporting improvements in COD performance have used exercises that more closely mimic the sport-specific demands (4), including various forms of jump training or plyometrics (horizontal and lateral, unilateral and bilateral), loaded vertical jump training, sport-specific COD training, and general COD training (4).
To increase the specificity of the perceptual and decision-making elements of agility training, some authors have suggested practicing agility skills under the time constraints of match situations, thereby forcing the player to make fast adjustments to the demands of the situation (18). Practicing acceleration, deceleration, and the crossover step under a variety of conditions (loaded or resisted and different distances and speeds) is likely to assist COD speed. Most players will need to progress to reactive agility drills in a variety of situations and under match like time constraints. It is worth noting in overall program design that reactive exercises will place a greater load on the musculoskeletal system (3), and therefore, the programming used to achieve overload will not be the same as that used for the planned agility drills.
Speed and agility is a multifactorial concept and as such needs to take into account all of the factors likely to influence performance. By applying a differential evaluation approach to results from speed and agility tests, it is possible to identify those areas of the high-performance tennis players' profile that require specific attention. This may help players and coaches train to improve specific areas of weakness to further enhance their on-court agility. However, the interpretation of the results and implementation of a meaningful strength and conditioning program will largely determine the success of any intervention, and ongoing assessment is always necessary. There are a range of different training methods that have been shown to be effective at improving COD speed. On the whole, sport-specific exercises have the greatest efficacy in enhancing this aspect of speed and agility.
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