13.1 and 26.2 correspond to the distances (in miles) a runner should cover in a marathon.
The 26.2 miles is the official distance for a full marathon while 13.1 is just half of that road running event (half-marathon).
13.1 and 26.2 stickers are popular and are commonly used as car decals and temporary tattoos representing completion of a half or full marathon.
The Athens Marathon is regarded as the original marathon course. Legend has it that the first man (Phidippides), honored by a 24.85 mile (40,000 meters) run from Marathon Bridge to Olympic stadium in Athens died and collapsed after covering the distance.
The distance was changed to 26.2 miles at the 1908 Olympic Games in London to cover the ground from Windsor Castle to White City Stadium. 2.2 miles were added on so the race could finish in front of the royal family's viewing box. This added two miles to the course, and is the origin of the Marathon tradition of shouting "God save the Queen!" as mile post 24 is passed.
The marathon is a difficult distance to master, no matter if you're a bucket-list runner whose only goal is to cross the finish line, or if you're a competitive runner on the hunt for a personal best.
Everything—from an ache in your calf to a hotspot on your foot to that cup of water you missed at the last fluid station—is heightened when you cover 26.2 miles on foot, but that's part of the lure of the marathon. If it were easy, the accomplishment wouldn't be as coveted.
Check out these 22 pieces of expert marathon advice that will help you get through training, racing and recovery with aplomb shared by Active.com.