Background Mass participation in recreational sport (such as cycling) is part of a healthy lifestyle, and is an important component in the primary and secondary prevention of non-communicable diseases (NCD's). However, there is a risk of acute traumatic injuries and acute medical complications during community mass participation cycling races, but this has not been well documented.

Objective The objective of this study was to document the incidence of acute traumatic injuries and acute non-traumatic medical complications in a community mass participation cycling race.

Design Retrospective cohort study.

Setting 109 km cycling race.

Participants All 34 033 race starters (males=26 835, females=7 198) to the 2014 Cape Town Cycle Tournament.

Assessment Pre-race entry demographic data and race-day medical complications data (all incidents that required assessment by the medical team on race day) were collected.

Main Outcome Measurements The incidence (per 1000 race starters) of all complications, acute traumatic injuries and non-traumatic medical complications and serious life threatening complications were determined for all cyclists, and male and female cyclists.

Results The incidence (per 1000 starters) of all complications was 6.35, and this was significantly higher in females vs. males (male=5.78, female=8.47; p=0.014). The incidence of serious life-threatening complications was 0.5, and there was a trend toward a higher incidence in female cyclists (female=0.97, males=0.37; p=0.06). Female cyclists also had a significantly higher (p=0.027) incidence of acute traumatic injuries (females=6.53, males=4.47; p=0.027). The incidence of acute non-traumatic medical complications was 1.44 (males=1.30, females=1.94; p=0.203).

Conclusions 1/157 race starters (males: 1/173; females: 1/118) at a community based cycling event were injured or developed a medical complication during the race, and the risk is significantly higher in female cyclists. These data indicate the need to develop and implement prevention strategies to reduce the risk of medical complications, specifically traumatic injuries, in female cyclists.