The Sydney City-2-Surf is the world’s largest annual run entered by around 80,000 people. First aid planning at mass participation running events such as the City-2-Surf is an area in the medical literature that has received little attention. Consequently, first aid planning for these events is based on experience rather than evidence. The models for predicting casualties that currently exist in the literature are either dated or not statistically significant.

The aim of this study was to characterize patterns of injuries linked to geographic location across the course of the City-2-Surf, and to explore relationships of injury types with location and meteorological conditions.

Records for formally treated casualties and meteorological conditions were obtained for the race years 2010-2016 and statistically analyzed to find associations between meteorological conditions, geographic conditions, casualty types, and location.

The most common casualties encountered were heat exhaustion or hyperthermia (39.2%), musculoskeletal (25.4%), and physical exhaustion (10.2%). Associations were found between gradient and the location. Type of casualty incidence with the individual distribution trends of casualty types were quite clear. Clusters of musculoskeletal casualties emerged in the parts of the course with the steepest negative gradients, while a cluster of cardiovascular events was found to occur at the top of the ‘heartbreak hill,’ the longest climb of the race. Regression analysis highlighted the linear relationship between the number of heat and physical exhaustion casualties and the apparent temperature (AT) at 12pm (R²= 0.59, P=0.044). This linear equation was used to formulate a model to predict these casualties.

The findings of this study demonstrate the relationship between meteorological conditions, geographic conditions, and casualties. This will assist planners of other similar events to determine optimum allocation of resources to anticipated injury and illness burden.