Trail degradation is a common management problem in protected areas, especially those that accommodate high levels of trail users or organized sporting events. Trail running became popular in Hong Kong in the early 2000s, with a number of trail running events involving large numbers of runners organized in recent years. Although trail competitions are believed to produce very intense impacts on trails and their surrounding environments, limited research exists to quantify and characterize these impacts to inform policy and management responses. This study empirically examined and evaluated the impacts generated by a running competition on a remote trail in Hong Kong. Results indicated that a running competition can cause significant initial degradation on the trail. Although some degradation features (e.g., incision) can recover in 6 months, some negative effects (e.g., soil coarsening) can persist or worsen. It is recommended that trail running competitions should be regulated in protected areas in terms of both number of events and number of participants. Trail maintenance is crucially important for keeping the protected areas in good condition.