Picture 1
ITF recommended minimum dimensions for multiple tennis courts in international competitions. (Reproduced with permission from the ITF and available at http://www.itftennis.com/technical/facilities/facilities-guide/site-plan.aspx)
Lines on the court [1]:
Baselines: Lines which delineate the width and edges of the court
Center mark: Mark in the center of each baseline
Service line: Line in the middle of the baseline and the net
Double sidelines: Outermost lines that delineate the length, used in doubles games
Single sidelines: Lines inside of the double lines, used in singles games
Center service line: Line dividing the service line into two from the net to the service line, creating two boxes
Classification Process of Wheelchair Tennis Athletes
The following classification rules are adapted from ITF Wheelchair Tennis Classification Manual as of 2016, but because it is subject to yearly review and changes, a general overview is provided here [8]. Wheelchair tennis players should have a permanent impairment that alters the biomechanical execution of the running action to the point that it will adversely affect sport’s performance. Further, such impairments must be assessed without aids or prosthetics [8].
Wheelchair tennis players can either be classified by the meeting minimal disability criteria (Fig. 19.1) or “quad” division criteria [8]. Athletes that participate in wheelchair tennis most commonly have a mobility related disability, including those with spinal cord injuries, strokes, brain injury, multiple sclerosis, spinal ataxia, cerebral palsy, amputations, limb deficiencies, or nerve injuries.
Quad Division Criteria
Athletes will be eligible for the quad division if they have a permanent impairment that alters their ability to manually use the wheelchair or to perform other sports-specific skills [8]. Again this is subject to yearly review [8]. Such skills include the overhead service, a continuous forehand, backhand, an inability to grip the racquet, and limited trunk function. Athletes also undergo “bench testing” which is available for review via the ITF. With bench testing, the strength and range of motion of the dominant limb and nondominant limb are classified according to the International Wheelchair Rugby Federation Classification Manual. Bench testing determines if the athlete meets impairment criteria for the quad division. If an athlete scores more than ten points out of the maximum 15 points, they are ineligible for the quad division [8].
Rules of Play
General Rules
Wheelchair tennis can be played as singles or between two teams of two players each (doubles) [7]. The general object of the game is to play the ball across the court so that the opposing player cannot make a valid return. The player that does not return the ball will not gain a point, whereas the opposite player will. Players are on opposite sides of the net. One player is the server; the opposite player is the receiver. If a wheelchair tennis player is playing with or against an able-bodied person in singles or doubles, the rules of wheelchair tennis apply to the wheelchair athlete, while the rules of tennis apply to the able-bodied athlete [7].
Serves
For each serve, the server starts behind the baseline, between the center mark and the sideline. Immediately before the serve, the wheelchair server is in a stationary position and is allowed only one push before serving [7]. If a conventional serve (kick serves and flat serves) is not possible for a wheelchair player (like a quad player), then the player or another individual may drop the ball for that player and allow it to bounce before being struck. The same strategy must be used throughout the match.
The player can also kick the ball up to be served. The ball must travel over the net, without touching the net, into the diagonal and opposite service box. If the ball hits the net, but lands in the service box, it is a “let” (which is considered void) and the server serves again [7]. If the wheelchair player’s wheel touches the baseline or the foot of an able-bodied server touches the baseline before the ball is hit, this is a “fault.” Two consecutive faults, is called a double fault, and the other player gets a point [7].
Plays
Once a rally starts, the player or team cannot hit the ball twice in a row. The “two-bounce rule” for wheelchair tennis players is as follows: the wheelchair player is allowed two bounces of the ball and the second bounce can either be in or out of the court boundaries [7]. The wheelchair player loses points if they fail to return the ball before it bounces three times or if the player uses any part of their feet. The wheelchair player must keep one buttock in contact with the chair when contacting the ball. If the player cannot propel the chair with the wheel, then they may use a foot; if they use a foot, the foot cannot be in contact with the ground during the forward motion of a swing through contact with the ball [7].
Scoring: Game, Set, Match
A game is won by the player who has four points in total or at least two points above the opponent. Scores of zero, one, two, and three are read as “love, fifteen, thirty, and forty,” and if both players are at forty each, it is read as “deuce.” The game advances until a player has won by two points [7].
A set consists of multiple games between the two players and lasts until a player wins at least six games with at least two games more than the opponent. The exception to the latter occurs if the set is tie at six games apiece, then a game occurs where the players alternate serves until someone leads by two points, and the final of the set would then be scored 7–6 [7].
A set break occurs at the conclusion of each set; there is a 2 min break until the time the first serve is struck for the next set. A match is complete after a sequence of three or five sets, depending on the events [7].
Important Medical Rules
A physician should be present at the event to evaluate and assess any injuries or illnesses that occur [7]. Although it is not mandatory, it is beneficial and preferable to the physician who has knowledge of spinal cord injuries and other disabilities. However, it is the goal of this chapter to provide fundamental knowledge for any volunteering physician to be comfortable with common conditions and injuries that one may encounter while covering wheelchair tennis.
Tournaments will provide shade and ice buckets on court for players with quadriplegia to prevent heat injuries given these athletes difficulties with thermoregulation. There are two toilet breaks permitted during a match. These are typically taken at a set break, which can be very important for spinal cord athletes to prevent autonomic dysreflexia due to an overdistended bladder or withholding a bowel movement [7].
An athlete can request a medical evaluation during a set break. Otherwise, only an acute medical condition can stop the play. An athlete is limited to two changeovers/set breaks for each treatable medical condition. If the player has a treatable condition, the medical team can determine if the player should continue [7]. A “medical time-out” is called if additional time for medical treatment is required. A time-out can only be 3 min long. Only one medical time-out is allowed per player and for each treatable medical condition. For example, all clinical manifestations of heat illness are considered one condition as are all treatable musculoskeletal injuries that manifest as part of the kinetic chain [7].
There are specific guidelines for certain conditions. For example, muscle cramping can only be treated during the change of ends/set breaks, unless it is part of one overall condition (like heat illness). If bleeding occurs, play should be stopped immediately and the medical team has up to 5 min to control the bleeding [7].
Equipment
Wheelchair
The wheelchair can be a sports wheelchair or an everyday wheelchair. Tennis players that meet bench test requirements can use a power wheelchair. The sports wheelchair often has a footrest, rear anti-tip tubes, a front caster, and a back caster [7]. They typically have non-marking tires that do not damage the court surface. Most tennis wheelchairs have wheels with a camber up to 25°, which provides a stable base for the player to move around the court [1]. Tennis wheelchairs also can have handles on the front seat for the athlete to stabilize themselves during a play [9]. Of note, there must be a secure place for players to store their tennis wheelchairs overnight at the events.
Racquet and Ball
Racquets must be approved by the ITF [1]. Tennis players with quadriplegia are allowed to use extra-long racquets in case where tape is required to secure the racquet to the player’s arm or hand. A player with quadriplegia can be given extra time to reposition or adjust the racquet without penalty during a match [7]. The balls used in matches vary depending on court type or even altitude of play but must be approved by the ITF [1].
Biomechanics
The tennis serve consists of four phases as described in Table 19.1 [10]. Shoulder joint biomechanics and kinetics of the wheelchair tennis serve has been studied and reviewed by Reid et al. [10] compared to able-bodied tennis players, and therefore this will be the focus of this section.
Table 19.1
The tennis serve
1. Cocking (the racquet’s highest point of vertical displacement in the backswing to maximal external rotation) |
2. Swing (from the racquet’s highest point to the time right before ball impact) |
3. Forward swing (from maximal external rotation to racquet-ball impact) |
4. Follow-through (brief time period post impact) |
In the study by Reid, wheelchair tennis players rotated their upper arms to positions of maximal external rotation 20° less than that seen in the able-bodied serve [10]. During forward swing, wheelchair tennis players have less trunk flexion, similar amounts of lateral trunk flexion, and more variable trunk rotation [10]. The humeral internal rotation during forward swing was 40–80% lower than that of able-bodied players [10]. Wheelchair tennis players have similar absolute pre-impact racquet velocities versus able-bodied players [10]. When compared to the able-bodied tennis serve, there was an estimated 33% reduction in the maximum pre-impact absolute and horizontal racquet velocities [10]. Further, relative post-impact peak external rotation moments and mean compressive forces (in the follow-through phase) were higher in able-bodied tennis serves compared to wheelchair tennis serves. In other words, wheelchair athletes did not demonstrate the expected compensatory kinetic response, like that seen in other adaptive athletes [10, 11].
There are important implications for these biomechanical differences observed in wheelchair tennis players. It appears the lack of the kinetic chain may work to the advantage of the wheelchair tennis player, unlike other sports where it may lead to increased forces throughout the shoulder [12]. For example, the mean plane of arm elevation in wheelchair tennis players was less than 180°, meaning their arms remained anterior to their shoulder alignments and suggesting less risk for impingement syndromes [10]. Further, wheelchair tennis players had a higher arm-thorax elevation angle during serves compared to able-bodied athletes [10]. This may actually help take load off the shoulder joint and improve speed. Reid’s study suggests that higher shoulder joint loading conditions may not occur in wheelchair tennis players, and therefore shoulder injuries are no more likely in wheelchair tennis players over able-bodied tennis players [10].
Common Injuries and Injury Prevention
Common wheelchair athlete injuries are summarized in Fig. 19.2 and expanded in this section. For review of studies looking at injuries specific to wheelchair tennis athletes, see Sect. “Wheelchair Tennis Injuries” in this chapter.
Fig. 19.2
Common wheelchair sport injuries (For references, refer to text.)
Common Wheelchair Athlete Injuries
Upper Limb Injuries
In general for wheelchair sports, upper limb injuries are most commonly reported. A 1991 study reported injuries commonly occurred in the hand (20%), followed then by the shoulder (15.5%), fingers (11.1%), and arm (10%) [13]. Another study, looking at only wheelchair athletes in track and field, wheelchair basketball, quad rugby, fencing, table tennis, tennis, and volleyball, similarly demonstrated soft tissue injuries commonly occurring in the shoulder (18%), followed by the arm (12%) and the wrist (12%) [14]. The general consensus within the adaptive sport literature is that injuries most commonly involve the shoulder, ranging between 15 [13] and 72% with the highest incidence in female wheelchair basketball players [15–17]. In those with arm injuries, the most likely diagnosis was muscle strains (52%), tendinopathy (30%), and bursitis (15.6%) and contusions [13, 14]. Interestingly, a 2012 Summer Paralympic study, which included all adaptive athletes (wheelchair and non-wheelchair users), determined that, irrespective of impairment type, the upper limb accounted for 50.2% of all injuries, with the shoulder being the most common (17.7%), followed by the wrist/hand (11.4%) and elbow (8.8%) [18, 19].
In wheelchair athletes, it appears chronic injuries (35–60%) may be more likely than acute, but this could be sport and study specific depending on the definition of acute versus chronic and methods to collect data [20–22]. Upper limb nerve entrapments are also common, specifically median mononeuropathy (50%) at the wrist and ulnar neuropathy (25%) at the wrist [23].
Spine Injuries
While the shoulder may be the most common site of reported pain in wheelchair athletes, the actual site of pathology in one study was determined to be the cervical and thoracic spine (59% and 8% respectively), suggesting common referral of pain to the shoulder [15]. This stresses the importance of a thorough physical examination.
Soft Tissue Injuries
Soft tissue injuries are often reported to include sprains, strains, and tendinopathies of the shoulder, elbow, arm, and hand, as well as blisters (74%), abrasions (68%), lacerations (12%), and decubitus ulcers (8.9%) [13]. Another study reported blisters and skin lacerations accounting for up to 35% of reported injuries [20]. Recall that the likely mechanism of blisters, abrasions, and lacerations (when there is not a collision involved) is contact of the hand or wrist with the chair rim. Since these may require minimum medical care, they may even be underreported [24].
Lower Extremity Injuries
Wheelchair Tennis Injuries
The incidence rate of wheelchair tennis injuries was reported as ~12.8 per 1000 athlete days at the 2012 Summer Paralympics, with the overall injury incidence rate being 12.7 [18]. Wheelchair tennis athletes reported 19 injuries (out of 106 athletes), 37% were acute injuries and 47% were overuse injuries. This is compared to boccia (91% acute (10× the amount of chronic injuries)) and goalball (77% acute (7× the amount of chronic injuries)) [18]. Wheelchair tennis is considered overall a low risk for injury when compared to high-risk sports like cycling, basketball, and rugby [26], but it still has a higher injury risk compared to bowling, billiards, table tennis, archery, and field events [20]. In a 1992 Paralympic study, 75% of wheelchair tennis players acquired an injury during training or competition [27].
With regard to the common risk for soft tissue injuries in wheelchair sports (strains, sprains, tendinopathy, bursitis) [14], certain soft tissues injuries may be more commonly seen in wheelchair tennis players, such as “tennis elbow” [10].
Shoulder injuries commonly seen in wheelchair tennis players are available by Jeon et al. [28]. Jeon performed ultrasonographic evaluation of the shoulder of 33 elite wheelchair tennis athletes and determined that the most common pathology in the dominant shoulder was acromioclavicular pathology (63.6%). Supraspinatus tears were found in eight dominant shoulders and six nondominant shoulders. The study found no correlation to shoulder pathology and the different variables studied including age, training time, or length of career/wheelchair use [28]. This study was limited by the fact that the pathologies seen may be related to the sport or everyday wheelchair use.
Another study compared scapular resting position and shoulder pain among wheelchair basketball players, amputee soccer players, and wheelchair tennis players. The study assessed scapular dyskinesis, as described by Kibler [29], and found that 54.5% had abnormal resting scapular positions (as well as more pain) compared to the non-wheelchair athletes (15.8%), suggesting frequent use of the wheelchair was responsible for the scapular dyskinesis. Racquet sport wheelchair players may therefore be prone to shoulder injuries since the movements performed during sport performance are different than those used in everyday wheelchair propulsion [30].
It is also important to remember that besides musculoskeletal injuries, illnesses can occur. For example, wheelchair tennis athletes, particularly ones with spinal cord injuries, are at higher risk of impaired thermoregulatory function and heat illnesses compared to wheelchair tennis players without spinal cord injury. The physician must be prepared to implement treatment [31].
Able-Bodied Tennis Injuries
There is a large body of literature reviewing the epidemiology of musculoskeletal injury in a tennis player, and it will only be briefly reviewed here in order to allow for comparison to wheelchair tennis injuries. According to a literature review in 2012 by Abrams et al., most able-bodied tennis injuries occur in the lower extremity (31–67%), followed closely by the upper extremity (20–49%) and trunk (3–21%) [32]. The authors also noted that chronic injuries were more common in the arm, while acute injuries were more common in the leg [32, 33]. The ankle and thigh (specifically ankle sprains) and the elbow and shoulder (specifically lateral epicondylitis) were the most commonly reported site of injuries for the lower limb and upper limb, respectively [32, 34]. Lateral epicondylitis was also the most common overuse injury [34]. With regard to the shoulder, younger tennis players tended to have shoulder pain secondary to shoulder instability, while older tennis players were more likely to have rotator cuff pathology [35]. Other common injuries (besides rotator cuff and lateral epicondylitis) for racquet sports in general are overdevelopment of the dominant arm, forearm nerve entrapments, low back pain, abdominal wall sprain, and tennis leg and eye injuries [36].
Injury Prevention in Wheelchair Tennis Players
Injury preventions have been proposed for wheelchair tennis athletes. Croft et al. proposed that with regard to the physiological demands of wheelchair tennis, wheelchair tennis players should have training through a full exercise intensity spectrum compared to other wheelchair athletes in order to compete safely. Of note, wheelchair tennis players with spinal cord injuries have been able to reach such physiologic thresholds for exercise intensity similar to able-bodied tennis players [37]. However, a study determined that physiologic parameters (such as peak oxygen uptake) do not correlate to wheelchair tennis ranks (i.e., performance), making it unclear the role physiologic-based training has in performance and injury prevention [38].
Wheelchair ergonomics must also be assessed including seat positioning, rear-wheel camber, wheel size, and hand-rim configurations [39]. A small survey revealed that wheelchair tennis athletes agreed that stability was the most important wheelchair contributor to performance, while camber was reported to have both positive and negative effects [40]. For more information on wheelchair ergonomics, see general injury prevention section.
There have been several risk factors identified with regard to injury in able-bodied tennis players that have yet to be assessed in wheelchair tennis players. For example, volume of play has been associated [33] with overall increased injury rate, while racquet grip and skill level may be risk factors for specific injuries [32]. Specifically for lateral epicondylitis (more common referred to as lateral epicondylitis), studies have looked at the two-handed versus one-handed backhand [41], vibration dampeners [34], and racquet grip size [32, 42], but there is inconclusive evidence on what role they may play in developing the pathology. It is likely that the etiology is secondary to improper technique [43] and time spent playing each week [44]. Risk factors that should be addressed to prevent recurrent shoulder injury in able-bodied tennis players have been identified as glenohumeral internal rotation deficit, rotator cuff strength (particularly the external rotators), and scapular dyskinesis [45, 46].
Injury Prevention for Wheelchair Sports (General)
As stated previously, all athletes should undergo a thorough physical examination and a task-specific performance evaluation to help identify areas prone to excessive load [36].
In general, since wheelchair athletes are more likely to develop upper limb injuries, it is not unreasonable to address range of motion and strengthening of the upper body. This includes the upper back, shoulder, and scapular muscles in all wheelchair athletes [47, 48]. Injuries in the upper limb may be due to the repetitive use of the upper extremities for wheelchair propulsion and overhead activities (in both everyday life and sport). For example, repetitive wheelchair propulsion mechanics encourage repetitive protraction of the scapula, leading to altered posture, and tightening of anterior shoulder muscles [49]. This may place the upper limb at increased risk for microtrauma and subsequent overuse injuries, like rotator cuff tears [50] and tendinopathies [30]. The “lack” of the entire kinetic chain during sports-specific tasks (like with racquet sports and throwing sports), and its role with regard to injuries, likely varies per wheelchair sport [10, 12].
The physician should also make sure that shoulder injuries are prevented “off the court.” For example, there is already a higher incidence of rotator cuff tears in wheelchair users compared to non-wheelchair users, which may mean the wheelchair athlete is at even higher risk for rotator injuries [51, 52]. In order to prevent injuries “off the court,” transfers and wheelchair propulsion should be monitored if applicable [53]. Physical therapy or occupational therapy should be considered for athletes who are at risk for injuries due to poor range of motion and improper technique seen with everyday functional tasks.
To expand on wheelchair ergonomics, assessment of the wheelchair in use may also help identify risk for nerve entrapments and spine injuries [39]. For example, nerve entrapments are likely secondary to hand-rim mechanics causing repetitive trauma to the nerves at the wrist or elbow [23]. It would not be unreasonable to consider orthotics as needed to try and prevent such entrapments. The spine may also be at risk for injury due to atypical seating position in wheelchair athletes. For example, spinal cord athletes typically sit with a posterior pelvic tilt and increased kyphosis of the thoracic spine and demonstrate a head forward position [30]. This may place inappropriate stress on the spine and lead to microtrauma and degeneration within the spine. All wheelchair modifications that can be made, without violating chair guidelines within each sport, should be considered.
Lastly, spinal cord athletes and cerebral palsy athletes have independent patterns of meeting energy demands during exercise (may not be anaerobic sources for power), and it is recommended that each strengthening program (such as intensity and frequency) be tailored toward the individual athlete’s impairments [54].
Summary
Wheelchair tennis athletes must have an impairment that alters the biomechanics of running. They may have spinal cord injuries, strokes, brain injuries, multiple sclerosis, spinal ataxia, cerebral palsy, amputations, limb deficiencies, or nerve injuries. The sport is very similar to able-bodied tennis, with the exception a two-bounce rule for wheelchair athletes. There are two main athlete classifications, the minimal disability division criteria and the quad division criteria. Wheelchair tennis players are generally at low risk for injury compared to other wheelchair sports, with overuse injuries being the most common. However, the medical team should be prepared to treat impairment-related illnesses, such as heat illnesses. Wheelchair tennis player shoulder kinetics do not demonstrate a compensatory kinetic response like that seen in other athletes. Further, the wheelchair tennis player’s adaptive serve may actually make their risk of injury no more likely than that of able-bodied tennis players.
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