The fact that athletes routinely use a wide array of substances is well documented as are the potential reasons for use . Whilst performance-enhancing substances are recognised in global as well as local anti-doping prevention programmes , other substances such as alcohol, tobacco and psychoactive drugs constitute a somewhat neglected area in the current idealised anti-doping educational effort. This prevailing approach creates an artificial divide between athletes' lives as sportspersons and private individuals. In reality, athletes constantly navigate their athletically active years on a tightrope between the different expectations they face both as athletes (often being in the spotlight) and as ordinary citizens, and know that failing in one part of their lives could easily result in failures in the other and vice versa.
Substances in sports are mainly used for the following reasons: (1) enhancing physical capacities (e.g., enhancing endurance, strength, or recovery between exercise sessions); (2) psycho-stimulation (e.g., as a way of dealing with psychological stress); or (3) improving physical appearance (e.g., for achieving a lean figure) [4–6]. Contemporary sport legislation recognises two types of substances used in sports: (1) non-controlled substances, such as the majority of nutritional supplements, and (2) products that contain prohibited substances (the use of which is often referred to as 'doping'). Nutritional supplementation is defined as a preparation intended to provide nutrients, such as vitamins, minerals, fibre, fatty acids or amino acids, which are otherwise missing or not consumed in a sufficient quantity in the athlete's diet . Doping is defined as the occurrence of one or more anti-doping code violations, mostly detected by the presence of a prohibited substance or its metabolites or markers in an athlete's specimens . Whereas nutritional supplementation should be considered a logical and natural consequence of the increased physical demands on athletes [9, 10], doping is deemed unethical for performance enhancement . Excessive use of NS and polypharmacy  as well as doping hasbeen connected to serious health problems [13, 14] and even death .
It is generally accepted that substance use and misuse (SUM) in sports is more common in physically demanding sports (e.g., weightlifting or cycling) than in sports that require advanced specific motor skills (e.g., diving, sailing, table tennis or curling) [4, 16]. However, to our knowledge, such generalisation is not sufficiently supported by any systematic comparative analyses of SUM across a variety of sports. Instead, the association of doping with particular types of sports has mostly come from anti-doping testing and the consequential public perception about doping in certain sports such as professional cycling, track and field or weightlifting.
In its capacity as the global anti-doping governing body, the World Anti-Doping Agency (WADA) established a detection-based system consisting of both systemic and random testing of athletes' blood and/or urine. Participation in this system is mandatory for all athletes registered in the testing pool at the national Olympic committees. This component of WADA's anti-doping programme uses detection and sanctions to keep doping out of sports by random testing from a pool of selected athletes in and out of the competition to find evidence for the presence of a prohibited substance or substances. Those with confirmed positive test results are typically banned from competition for a period of time (1-2 years) and stripped of any medals and records that were thought to have been achieved with the aid of doping. As a different approach, WADA's anti-doping prevention aims to create a strong anti-doping culture and target all athletes with its value-based education programmes to foster abstinence from prohibited performance-enhancing drugs.
The majority of sport activities take place outside of controlled environments, leading to substance use without medical advice or supervision . The mismatch in targets in the anti-doping prevention and deterrence programmes coupled with the limited concern over substances such as alcohol and social drugs raises questions about the suitability of the current anti-doping policy.
Whilst both arms of WADA's anti-doping effort represent heroic measures to keep doping out of sports, laboratory statistics shows no significant change between 2003 and 2009 with the proportion of adverse and atypical findings ranging between 1.50% and 2.12% . Self-reports, alternative analyses and epidemilogic estimations indicate that the actual prevalence of doping is greater than this official statistic and ranges up to 40% . Although it is difficult to make a direct comparison between the latter and the WADA laboratory report, a recently published report evaluating 7,289 blood samples from 2,737 track and field athletes in the athlete testing pool, using the Athlete Biological Passport approach , estimated the prevalence of blood doping to be at 14% overall and between 1% and 48% for sub-populations , which supports the results from the epidemiologic studies.
Furthermore, it is apparent from annual lab statistics  that the doping-testing programmes concentrate the analyses on(a) Olympic rather than in Non-Olympic sports, and on(b) sports which are already associated with doping (e.g., 'physically demanding sports'). For example, in 2009, 26,593 urine and blood samples from track and field athletes yielded 398 total findings of suspicious substances. At the same time, 467 tests of curling athletes resulted in only 14 total findings . The higher absolute number of adverse or atypical analytical findings in 'highly physically demanding' track and field athletics than in 'less-demanding' curling seems unsurprising (398 vs.14). But, the surprising pattern is evident for aquatics (13,995 total samples; 156 total findings, or 0.65% of samples) in comparison to shooting (24/2,630; 0.91% of samples) or archery (14/976; 1.44% of samples). Doping in Olympic racket sports was found to range from0.17% to 0.94% in the following order: badminton: 2/1,175, tennis: 17/3,945 and table tennis: 10/1,066.
Racket sport games are characterised by a handheld racket that is used to propel a missile between two (or four) players with the purpose of placing the missile in such a position that one player is unable to return it successfully. These sports are also characterised by an area of play that has a specified size, within which the missile must be contained, and by the presence of a net that the missile must pass above on each play. The unique sizes and shapes of the area of play, the height of the net and the type of missile and racket used give character to each variant of the game. Racket sports are unique due to the fact that players can modify the physiological demands of the game by controlling the rest intervals between rallies, games and sets. Average oxygen consumption for single-match duration badminton is reported to be 39.6 ± 5.7 ml/kg/min (73% VO2max); oxygen consumption for table tennis is 26 ± 4 ml/kg/min (47% of VO2 max), and consumption for tennis is 29 ± 6 ml/kg/min (51% of VO2 max). Of course, average match duration must also be considered. In the 2006 badminton World Championship in Madrid, the average match duration was 33:35 minutes. At the Olympic Games in Beijing, the average table tennis match lasted for 27:31 minutes. The average duration of tennis matches depends on the type of court but typically ranges from 120 to 180 minutes. For example, at Wimbledon in 2005, the average duration of tennis matches was 137 minutes, whereas the average match in the Australian Open that same year lasted for 154 minutes. A major determinant of the outcome of a game is an individual's physical fitness, which can be influenced by SUM [22, 23].
Although SUM is regularly investigated in sports as a whole , SUM is rarely studied in racket sports. To the best of our knowledge, apart from studies dealing with sports and physical activity in youth and related SUM issues in which racket sports (tennis mostly) were not studied systematically [25, 26], there are only a few papers addressing SUM in Olympic racket sports. Briefly, Kondric et al.  reported on SUM habits in Slovenian table tennis players. Also, Maquirriain  analysed offences to the Doping Code committed by tennis players between 2003 and 2009. When studying SUM problems in sports, previous investigations noted that SUM is gender-, sociodemographic-, culture-, and sport-specific and, therefore should be studied accordingly . Furthermore, one recently published study highlighted the advantage of a comparative approach to investigating SUM in sports . The authors investigated SUM templates in aesthetic sports (synchronised swimming, dance sport, and ballet) while focusing on organisational differences and anti-doping regulations across the different activities. In short, the authors found evidence for (1) different substance use and misuse patterns and (2) sport-specific correlations between educational and sociodemographic factors along with the likelihood of overall substance misuse (as predictors) and doping. These findings demonstrated the necessity of using a similar experimental approach when evaluating other sports and sport activities.
Apart from the fact that SUM is rarely investigated among racket sports, we determined that these sports would be particularly suitable for our study based on several factors. First, table tennis, tennis and badminton are Olympic Sports that fall directly under WADA jurisdiction and anti-doping legislation. Second, all three sports share similar competitive characteristics as they are all individual sports with no physical contact between opponents. However, these sports are also diverse in terms of physiological demands.
The primary aim of this study was to investigate substance use and misuse and to determine sport-specific and sex-related differences regarding SUM habits and attitudes in Slovenian Olympic racket sports (table tennis, badminton and tennis). In addition, we have studied the relationships between sports, education, and non-sport-specific substance use and misuse with doping factors. In response to the recognised need for critical evaluation of the current anti-doping approach and to extend the harm reduction argument presented in the literature for doping control  to include substances beyond performance-enhancing drugs, the present study evaluated non-sport-specific substance use and misuse among elite racket sport players in order to ascertain whether the current anti-doping policy has the potential to adequately address its mission of protecting the integrity of sport as well as the health of athletes.