Medical encounters, cardiac arrests and deaths during a 109 km community-based mass-participation cycling event: a 3-year study in 102 251 race starters-SAFER IX.

In a 109 km community-based mass-participation cycling event, medical encounters (moderate to severe) occurred in about 1 in 200 cyclists. Injury-related (1/300 cyclists) encounters were higher than illness-related medical encounters (1 in about 500). Serious life-threatening medical encounters occurred in 1/2000 cyclists. These data allow race organisers to anticipate the medical services required and the approximate extent of demand.