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Frequency and type of adverse analytical findings in athletics: Differences among disciplines

Athletics is a highly diverse sport that contains a set of disciplines grouped into jumps, throws, races of varying distances, and combined events. From a physiological stand-point, the physical capabilities linked to success are quite different among disciplines, with varying involvements of muscle strength, muscle power, and endurance. Thus, the use of banned substances in athletics might be dictated by physical dimensions of each discipline. Thus, the aim of this investigation was to analyse the number and distribution of adverse analytical findings per drug class in athletic disciplines. The data included in this investigation were gathered from the Anti-Doping Testing Figure Report made available by the World Anti-Doping Agency (from 2016 to 2018). Interestingly, there were no differences in the frequency of adverse findings (overall, (cid:1) 0.95%, range from 0.77 to 1.70%) among disciplines despite long distance runners having the highest number of samples analysed per year ( (cid:1) 9812 samples/year). Sprinters and throwers presented abnormally high proportions of adverse analytical findings within the group of anabolic agents ( p < 0.01); middle- and long-distance runners presented atypically high proportions of findings related to peptide hormones and growth factors ( p < 0.01); racewalkers presented atypically high proportions of banned diuretics and masking agents ( p = 0.05). These results suggest that the proportion of athletes that are using banned substances is similar among the different disciplines of athletics. However, there are substantial differences in the class of drugs more commonly used in each discipline. This information can be used to effectively enhance anti-doping testing protocols in athletics.

body mass may have a positive contribution on some disciplines such as shot put and the hammer throw. Conversely, performance in middle-and long-distance running races and racewalking is based on the combination of high maximal oxygen uptake, running speed at lactate threshold, and running/racewalking economy. Low body bass may also be beneficial for these physiological determinants and is usually a key anthropometric objective in long distance athletes. With a few exceptions, elite athletes are only capable at achieving records within their own discipline, signifying the unique performance characteristics of each discipline. In fact, the evolution of track and field records in the last century has been uneven. 3,4 It has been speculated that the use of banned substances might have contributed to the atypical achievements found in some disciplines at very specific moments. 5 In this regard, it has been previously speculated that the use of banned substances in each track and field discipline might be dictated by the discipline's physiological dimensions and performance determinants, 6 but to date, this has not been properly confirmed with real and objective data.
An adverse analytical finding indicates the presence of prohibited substances in a particular sample obtained during a doping control test and measured by a laboratory accredited by the World Anti-Doping Agency (WADA). Previous research 7 has revealed that the prevalence of adverse analytical findings in athletics is around 1.6%, which has been kept relatively constant since 2003. Despite having the highest number of doping control tests conducted each year, 7 athletics has one of the lowest proportions of adverse analytical findings among individual sports. However, the prevalence of doping has been estimated to be up to 43.6% in World Championships in athletics by using surveys with the randomized response technique. 8 The discrepancy in the estimated prevalence of doping by surveybased investigations and the proportion of adverse analytical findings may be associated to the different methodologies used to collect the information. Nevertheless, it suggests that the current anti-doping systems has several limitations to accurately trace the use of banned substances and methods. Specifically, the limited analytical capability of WADA-accredited laboratories, the short detection window for some banned drugs, and the economic costs of testing athletes several times during the season produce that some cheaters remain undetected by the current system of doping control. 9 Despite these limitations, the analysis of the results of doping tests is an objective and robust method that allow to understand trends in the abuse of substances within a particular sport. 7 Overall, anabolic agents represent the most commonly found adverse drug finding of in athletics (when analysing all disciplines together as a unique sport), followed by peptide hormones and stimulants. 10 Interestingly, the concentration of these substances is higher than the concentration found in other individual and team sports. 10 However, it is likely that the prevalence of adverse analytical findings across drug classes is different among all track and field athletic disciplines, as the physiological determinants are highly different among disciplines. Obtaining more information about the most commonly used substances in each athletic discipline might be the key to plan more comprehensive anti-doping policies. This would entail the establishment of in-and out-of-competition doping testing on athletes by specifically searching for substances habitually used in each discipline. Thus, the aim of this investigation was to analyse the number and distribution of adverse analytical findings per drug class in athletics disciplines using data from the WADA-accredited laboratories. From the data included in the Testing Figure Reports, we excluded samples that had insufficient information for the purposes of the study or were labelled as "Athletics" (5176 data in 2016, 447 data in 2017, and 186 data in 2018) since it was impossible to categorize the data into any of the above mentioned athletic disciplines.

| Statistical analysis
The data were electronically extracted from the Testing

| RESULTS
A total of 87,380 doping control tests were taken and analysed for athletics from 2016 to 2017. Figure 1 contains information about the number of samples analysed per year in each discipline.
The statistical analysis revealed a significant difference in the number of samples analysed among disciplines (K = 21.52; p < 0.01).
The number of samples analysed in long-distance runners and sprinters was higher than in athletes of combined events, road runners, and racewalkers (p < 0.05). The samples analysed in throwing and jumping events were also higher than in racewalking (p < 0.05).
The ANOVA analysis revealed no significant differences in the proportion of adverse analytical findings among disciplines (F = 8.91; p = 0.26). Overall, the frequency of adverse analytical findings in most disciplines was below 1.0%. Only road runners (1.7 ± 0.2%) and long-distance runners (1.1 ± 0.2%) had an average that lied beyond this threshold. A detailed analysis of the number of adverse findings per year in each discipline is included in Table 1.  Interestingly, jumping and combined events also share the need for high values of muscle power, but the proportion of anabolic agents is lower. In the case of jumpers, they had an abnormal proportion of hormone and metabolic modulators (Figure 2). Within the group of hormone and metabolic modulators lies several synthetic compounds, which act by modulating various endogenous hormonal pathways and muscle-specific transduction pathways. In most cases, the aim of such modulators is to enhance non-steroidal anabolism, although it is has been found that some of them may counteract the unwanted side effects of anabolic androgenic steroid administration. 6 In the case of combined events, there was a high proportion of glucocorticoids, likely due to the use of these banned substances to treat the consequences in form of injury and pain induced by the extreme physical demands of this discipline. Although the high use of glucocorticoids has previously been reported in other elite sportswhere overuse is a particular concern 20 -anti-doping organizations should make an effort to reduce the use of this group of substances in combined events.
Peptide hormones and growth factors were more commonly found in middle-and long-distance runners. This drug class contains erythropoietin-receptor agonists, hypoxia-inducible factor activating agents, and innate repair receptor agonists, all of which have a potent capacity to increase erythropoiesis and red blood cell concentration in the blood. In middle-and long-distance race events, blood oxygen carrying capacity is an essential factor for performance. Thus, several peptide hormones may help to increase muscle oxygen supply, ultimately boosting performance. 21 Growth factors-such as growth hormone-may help to reduce body fat and enhance tissue-repairing effects on the musculoskeletal system, which may be performance factors for middle-and long-distance runners. Interestingly, the presence of adverse findings due to peptide hormones and growth factors in disciplines whose success primarily depends on muscle power was small. Together, these outcomes suggest that the search for this class of drugs in doping control tests may primarily be focused on track and field disciplines with an endurance component.
At the same time, long distance runners had an atypical proportion of β2-agonists. β2-agonists are commonly used as bronchodilators in the treatment of asthma, which is the most common medical condition in elite-level athletes. 22 In the last few years, the perception that asthma medication may enhance sports performance has created a negative stigma towards athletes with asthma. 23 WADA currently allows the therapeutic use of salbutamol, formoterol, and salmeterol.
These substances are only considered as an adverse finding when they surpass a certain threshold. 24 Although the majority of studies have demonstrated limited effects of inhaled β2-agonists on aerobic exercise performance, 25 short-term oral administration of salbutamol has been shown to significantly improve submaximal time to exhaustion in non-asthmatic elite athletes. 26 Anti-doping authorities should study the motives behind the high proportion of findings related to β2-agonists in endurance athletes and harden the criteria to grant therapeutic use exemptions if necessary. 27 Racewalkers had a high proportion of diuretics and masking agents. Despite diuretics not directly producing a clear benefit on physical performance, they can be used to mask the administration of other doping agents by reducing their concentration in urine through increased urine volume. 28 The authors hold the opinion that the use of diuretics may not entail a potential benefit for racewalking races since these events have a long duration and the hypohydration produced by these substances may be negative for performance. 29 A more thoughtful analysis should be made to determine why racewalkers may use diuretics and other masking agents.
The current analysis has some limitations that should be considered when drawing conclusions about the use of banned substances in track and field disciplines. First, the current investigation includes an analysis of the adverse analytical findings obtained by the system of doping control tests in athletics. However, it has been previously proposed that the current anti-doping system has several flaws that allow that some athletes using banned substances remain undetected. 9 In fact, it has been suggested that the probability of detecting a cheater is only of 33% when the athlete is tested 12 times per year and it may be needed up to 50 tests per athlete to detect 100% of doping. 30 It is probable that the analysis of detected sub- However, anti-doping authorities should be aware that doping misconducts are in constant change while the analytical capacity of the laboratories may be not enough to detect the use of some substances in microdoses.