Background Despite the growing popularity of triathlon, very few studies have assessed the casualty incidence and profile during races. The World Triathlon Championships in London offered the opportunity to observe this at the largest triathlon ever held.

Objective This study describes the profile of casualties sustained across a five day triathlon event. It is hypothesised that an association exists between casualty risk and the variables of age, gender, event standard and distance.

Design Observational data was collected on all participants who were entered to compete in the event, and whom sought medical aid either during the event or after the finish of the event. Casualty nature was categorised into topical, musculoskeletal and constitutional.

Setting The World Triathlon Championship Grand Final was held in Hyde Park, London over five consecutive days in September 2013, comprising both elite and non-elite fields.

Participants A total of 6 103 inidviduals participated from 84 countries. Age ranged from 16 to 80 years.

Risk factor assessment Independent variabales included: age; gender; event standard, event distance and event type.

Main outcome measurements 1) Total casualty incidence for age, gender and standard. 2) Casualty incidence difference by gender for each event type 3) Nature of casualty incidence for age, gender and event type.

Results Females had a higher casualty rate than males, across majority of event types. Elite athletes had a higher casualty rate. Topical casualties were highest in 40–49 age group, and for sprint distances, musculoskeletal casualties were highest in 50–59 age group. For the Olympic distance, constitutional casualties were highest for females, the oldest and the youngest.

Conclusions In a large world triathlon championship event, the incidence and nature of participant casualties is associated with age, gender, event distance and standard. These findings could support organisers seeking to plan effective medical resourcing and injury prevention strategies for such future events, and help inform triathletes of their risk of injury during races.