Thermal effects and marathon runners - A symbiotic relationship

Abstract

The Hong Kong Standard Chartered Marathon has been held annually in Hong Kong since 1997 with recorded entrants growing to 75,000 in 2013. The event route is confined to urban areas passing through commercial districts packed with densely built high-rises to traffic interchanges with semi-enclosed tunnels and overhead suspension bridges. This unique setting coupled with an increasing number of runners on the course has raised concerns about thermal stress to runners throughout the event. Each year, there are runners reported to have suffered from heat exhaustion, heat stress and other heat related illnesses. The study placed 50 logging sensors at strategic locations along the marathon courses to take temperature and humidity measurements at minute time intervals. These measurements were mapped to sampled locations using GIS/GPS tools. The respective meteorological conditions were correlated with the crowd of runners for different time intervals along different sections of the course. The upper safety limit of Carbon Dioxide was also monitored within semi-enclosed tunnel of 2 km in length. This empirical study not only establishes the feasibility of employing the small and inexpensive logging sensors for widespread deployment but also confirms microclimate variations in different environmental settings. In particular, the study verifies the impact of herd effects on marathon runners in terms of thermal level and carbon dioxide concentration in a semi-enclosed tunnel. The findings inform the organizers the necessity to regulate airflow in traffic tunnels and caution special conditions to watch for in future events, including narrow street canyons and fully exposed sites.