Background Decathlon is a track and field discipline where participants run, jump, and throw; and the competitions are highly demanding from both the physical and psychological standpoints because of the frequency and intensity of the events. Knowing the frequency and causes of dropouts in decathlon competitions seems relevant and helpful to develop strategies of injury prevention for decathletes.

Objective To determine the causes of dropouts and the frequency of injury as the cause of dropout in decathlon.

Design Pilot prospective epidemiological study.

Setting This study focused on three senior male national or international level (high-level) decathlon competitions.

Participants 50 senior male national or international decathletes.

Interventions Data concerning athlete's participation (number of participating athletes listed on the start list, number of athletes in the final ranking), the event (or time) of dropout, and the causes of dropouts were collected prospectively during the three high-level decathlon competitions. In case injury was retained as the cause of dropout, its description was made following the IAAF and IOC recommendations.

Main outcome measurements Percentage of dropouts and percentage of each dropout cause, description and percentage of injuries (circumstance, location, type).

Results 38% of decathletes did not complete these competitions. The causes of dropout were: injury (36%), loss of motivation (36%), tiredness (9%), and indeterminate (18%). 50% of injuries were acute hamstring injuries during explosive events on the first day (100-m and long jump).

Conclusion Not completing a decathlon is rather common due to various difficulties (physical, technical and psychological). Although caution is needed when interpreting these results due to methodological limitations, musculoskeletal injury prevention and motivational aspects seem important to complete an entire decathlon and to aim at best performance. More detailed prospective studies are needed to determine the exact medical causes of dropouts in decathlon.