Consensus recommendations

Table 1 summarises the tennis-specific additions to the IOC consensus statement: methods for recording and reporting of epidemiological data on injury and illness in sport 2020.1

Defining and classifying health problems

We adopt the definition of an athlete’s health problem as stated by the authors of the IOC consensus statement as any condition that affects an athlete’s normal state of full health, irrespective of its consequences on the athlete’s sports participation or performance, or whether the athlete sought medical attention.15 Such a broad definition is crucial for tennis, a sport where non-time-loss problems dominate the injury and illness spectrum.16 17

The IOC consensus statement recommends implementing methods that capture relevant subtleties of injury onset, rather than using sudden and gradual onset as a dichotomy only. In table 2, we provide tennis-specific examples for this classification.

Classifying sports injury and illness diagnoses

The IOC consensus statement provides a standard format for reporting injury characteristics, based on a template used by rugby. Unfortunately, for tennis, such detailed information is currently unavailable. We included examples of shoulder injuries and diagnoses to illustrate the potential format of standard reporting in tennis (table 3). Studies can expand or collapse tables to highlight specific diagnoses in any way they choose.

In wheelchair tennis, upper limb injuries are common, as well as injuries to stumps and insensate upper and lower limbs. These include lacerations, contusions and abrasions to the stump skin as well as insensate pressure areas. Stump injuries should be recorded according to their anatomical location and have associated Orchard Sports Injury and Illness Classification System and Sport Medicine Diagnostic Coding System codes.18

Severity of health problems

The duration of time loss is often used to capture severity. The IOC consensus statement defines time loss as the number of days that the athlete is unavailable for training and competition, from the date of onset until the athlete is fully available for training and competition. Although time loss is generally considered easy to capture, it is difficult to operationalise in tennis where systematic data collection is only available at tournaments. Even though it is possible to register a time-loss problem that occurs during a tournament, it is challenging to track the duration of every time-loss injury afterwards. Therefore, we recommend that the injury’s time-loss be confirmed at a later stage through the player or their doctor, if feasible. Be aware that there are inherent difficulties with this approach. Inability to contact players out-of-competition, recall bias, technological issues (ie, multiple athlete management systems are in use) and variations in medical personnel (ie, other medical support provided at each event) may affect the ability to capture this information.

Depending on the research question, it may be more appropriate to express the severity of the health problem in tennis by (1) the nature of the sports injury or illness (eg, stress fracture, rotator cuff tear), (2) the OSTRC severity score or (3) the outcome of the injury (eg, retirement from tennis).15 19

Capturing and reporting athlete exposure and expressing risk

Tennis is a sport that demands a variety of training methods to improve and optimise performance. Therefore, training exposure in hours should be registered separately for tennis practice (skills and drills), and strength and conditioning. When monitoring load in high-performance tennis and wheelchair tennis players, a further subdivision of strength and conditioning into strength training, conditioning, movement/speed/agility and body management skills is recommended (online supplemental appendix 1). In high-performance tennis, monitoring the response to training and matches is essential to optimise training programmes and mitigate the risk of injury, and the Rate of Perceived Exertion per session can be used as a measure of internal and external load (online supplemental appendix 1).20 21

However, specific to tennis, simply measuring exposure in terms of time may be insufficient because time and actual ‘workload’ do not correlate well. Workload does not equal time played because the game of tennis poses several factors that may make an hour of play more or less demanding for a player. This is especially true for exposure during competition because there is no time limit on the duration of a match. Tennis matches can last less than 30 min (3-set match) to more than 11 hours (5-set match).22 Therefore, for competition, we recommend registering exposure in time, as well as recording the number of matches, sets, games and/or points played.

We recommend expressing risk as the number of injuries per 1000 hours and per 1000 games played (ie, the games from a match) as this will allow for comparison between sexes and playing surfaces. It may not be feasible to collect such detailed data at the community level of play, and then injuries per 1000 sets or matches may suffice.

Additionally, tennis involves the loading of the upper and lower body, in marked contrast to sports like soccer, running and skating, where loading mainly affects the lower body. Because both the upper and lower limbs are involved, it is crucial to monitor the load on both the upper and the lower body to make meaningful inferences about the actual ‘load’ and subsequent health outcomes.23 This monitoring is an enormous challenge in practice, but the future sensor and video technology may well prove beneficial.

For specific research questions (eg, risk factors for calf muscle strains and the influence of serving load on shoulder injuries) it may be useful to collect data on:

• The total distance covered, running speed, total (sum of) whole-body acceleration and the number of changes of direction.24–27

• The number, velocity and type of strokes (eg, serves, forehands and backhands) (online supplemental appendix 1).27–29

The following tools are already available to capture some or all of these data, although with different accessibility, precision, reliability, ease of use and cost:

1. Optical tracking systems, for example, Hawk-Eye or Playsight.30 31

2. Global positioning system (GPS) systems, for example, Catapult.32

3. Inertial measurement unit (IMU) sensors, for example, Movesense33 or next-generation IMUs.34

To capture the distance covered in wheelchair tennis, we recommend using IMUs, because they are ubiquitous, low-cost, non-invasive, valid and reliable for wheelchair court sports.35 36

Because tennis is most commonly played outdoors, the environment changes continuously and the playing surface changes from tournament to tournament. There may be extreme heat in Atlanta, Miami and Australia (on hard courts), whereas it may be cold in Northern Europe (it snowed during the Munich 2016 Association of Tennis Professional (ATP) event on clay).37 Environmental factors, including court surface (eg, clay, grass, hard courts and synthetic turf), heat and humidity (eg, temperature, heat index and wet bulb globe temperature (WBGT)) and variations in air quality (air pollution, pollen and nitrogen dioxide) are all useful to add context to injury and illness surveillance. This information will help to answer specific research questions (eg, injury incidence on various playing surfaces, association between heat illness incidence and WBGT, incidence of asthma and air quality index) (online supplemental appendices 2–5).38–40 Recording of the environmental conditions is vital in wheelchair tennis. Some athletes with disabilities can have impaired thermoregulatory systems that lead to increased susceptibility to heat illness (eg, spinal cord injury with less or no sweating below the level of the lesions).41

Study population characteristics

Tennis is a sport with a wide variety of participants in terms of sex, age, disability and skill level. The amount of money and human resources available for data capture and analysis will vary based on factors including, but not limited to:

• The level of participation (professional/elite junior/community).

• The wealth and medical systems of the country in which it is taking place.

Tennis consists of singles and doubles, can be played from youth to seniors and can be played at many levels of expertise, each with a distinct risk for adverse health effects. Table 4 provides the minimum population characteristics to be reported in tennis-specific health monitoring. For the level of play, we recommend using the World Tennis Number as soon as it becomes available.42 Also, the discrete categories beginner, intermediate, advanced and elite/high performance can be used. However, researchers are encouraged to provide additional demographic information relevant for their studies, such as Women Tennis Association (WTA), ATP or ITF ranking; national, regional or club level; or high school or college athlete.

We recommend collecting the following data at baseline and annually: sex, date of birth, country of residence, level of play, dominant hand, regular playing surface, competition, training volume per week (tennis and strength and conditioning), other sports per week and current injuries.

Additional data (that might be omitted at community level surveillance if resources are limited) include:

• Starting age at tennis.

• Height, weight.

• Single-handed or double-handed backhand.

• Previous injuries.

• Number of singles and doubles tournaments per year.

• Number of singles and doubles matches per year.

• The highest level of education.

With reference to wheelchair tennis, there are currently seven eligible impairment types. These include impaired muscle power, athetosis, impaired passive range of movement, hypertonia, limb deficiency, ataxia and leg length difference. There are two classes in wheelchair tennis. The ‘Open’ Class is for athletes with permanent impairment of one or both legs, but with normal arm function. The ‘Quad’ Class is for athletes with additional restrictions in the playing arm, limiting the ability to handle the racket or manoeuvre the wheelchair. Both the impairment type and the class should be recorded in injury and illness surveillance to determine risk profiles.

Data collection methods

The two governing bodies for professional tennis, the Association of Tennis Professionals (ATP, men) and the WTA (women), currently use electronic in-competition registrations. The ITF (world tennis, wheelchair tennis and beach tennis) has recently started an electronic collection of injury data at the men’s and women’s world tennis tour. Many national federations have their own athlete health management systems, with more emphasis on out-of-competition data collection. However, because the data collected by these diverse electronic registration systems are not publicly available or compatible, we have developed templates for (1) the collection of baseline information in tennis and wheelchair tennis, (2) injury reporting, (3) illness reporting, and (4) match and training exposure (online supplemental appendices 1–5).