Cool-weather races can leave you chilly once you cool down, so race organisers will often hand out mylar "space blankets." Don't throw yours away — it's the perfect way to keep warm at the start line of your next race.
Photo by ActiveSteve.
This is just one of the suggestions in Runner's World's list of lesser-known options for start line comfort. Marathoners often show up in thrift-store sweats, and peel them off as the race begins. (By the way — be considerate and throw them in the trash or, if available, charity bins.) But there are other great suggestions on the list, including cutting off a pair of knee socks to make arm warmers.
The Best Throwaway Gear to Stay Warm Before a Race [Runner's World]