Spectators at the finish of a marathon can watch a long line of runners, draped in shiny silver blankets as they make their way through the finishing area. Some of the runners are walking slowly, some are limping, some look bewildered and some are trying to peel a banana. After running 26.2 miles, they need some TLC, which is what the silver thermal blankets provide.
Unlike football, basketball or baseball, marathons don't have a season. Runners can choose races all over the world, in all climates, time zones and elevations. However, host cities always schedule their marathons in their mildest weather. For example, Boston and London are in April, after their hard winters but before the heat sets in. Chicago is in October -- before cold winds blow off Lake Michigan but after the hot and humid summers. For runners, this means perfect running weather, but it also means it can be cold at the finish after they stop running but are still wearing their damp running clothes.
Long Walk to Dry Clothes
After crossing the finish line, marathoners stop running, but they don't stop sweating. In addition, the evaporation effect they were getting from running stops too. So damp running clothes get even wetter. And wet clothes translate into shivering runners. Races give participants the option of packing a bag that is available at the finish. But in big races such as Boston, it can take the runner 20 minutes to find his bag with dry, warm clothes. Allison Macsas, a 2012 U.S. Marathon Olympic trials qualifier explains, "No matter how hot and sweaty I may be at the finish, it never fails that 30 minutes later I'll find myself cold, shivering and still searching for my bag full of nice dry clothing."
NASA developed the material for thermal blankets as insulation and used it on all manned and unmanned missions since Apollo. Most dramatically after Skylab lost a heat shield during take off, NASA engineers fashioned an umbrella-like protector from the reflective material. In the mid-1970s, marathon race organizers started distributing the "space" blankets to finishers. As of 2011, the blankets are often customized with race logos, making them a shiny souvenir.
According Princeton's Outdoor Action, signs of hypothermia include shivering, clumsiness, stumbling and confusion. These symptoms also describe what some marathoners experience at the finish line. Without the thermal blankets, many runners would find themselves in the medical tent instead of celebrating with family and friends. The next marathon you run, take Macsas's advice: "Always take the blanket."